Orthopedic Hand & Wrist MCQs: Online Exam & Study Questions

The most common mechanism of injury for turf toe is a hyperextension injury to the MTP joint. The foot is typically in a dorsiflexed position with the heel raised when an external force drives the MTP joint into further dorsiflexion. The joint capsule usually tears at the metatarsal neck because its attachment is weaker there than at the proximal phalanx. Some compression injuries to the dorsal articular surface of the metatarsal head can result from extension or hyperextension.
REFERENCES: Clanton TO, Ford JJ: Turf toe injury. Clin Sports Med 1994;13:731-741.
Rodeo SA, O’Brien S, Warren RF, et al: Turf toe: An analysis of metatarsophalangeal joint sprains in professional football players. Am J Sports Med 1990;18:280-285.

According to the referenced study by Folk et al, the risk of early wound complications is highest in open injuries, diabetics, and smokers.
No significant differences were seen in complication rates in terms of: age, sex, other pre-existing medical conditions, social history, mechanism of injury, time from injury to surgical stabilization, the type of incision used, use of preoperative antibiotics, or type of wound closure.
Notably, 25% of the patients had some sort of early wound complication, and 21% of the patients required surgical treatment due to their wound complication.
Their conclusion: "Smoking, diabetes, and open fractures all increase the risk of wound complication after surgical stabilization of calcaneus fractures.
Cumulative risk factors increase the likelihood of wound complications."

A brachial plexus injury would involve all of the upper extremity muscles as well as most of the periscapular muscles. Complete plexus palsies are rare, and are often associated with scapulothoracic dissociation or other high-energy injuries.
Preganglionic injuries often involve the cervical paraspinal musculature as well as a complete plexus injury. EMG evidence of intact signals in the serratus anterior (long thoracic nerve) and rhomboids (dorsal scapular nerve) are suggestive of a postganglionic lesion/injury.
Tubbs et al. reported on the surgical anatomy of the dorsal scapular nerve in a cadaver study. They found that the nerve came off the C5 nerve root in 95%, ran 2.5cm medial to the spinal accessory nerve as it traveled on the anterior border of the trapezius muscle, and was intertwined with the dorsal scapular artery in all specimens.
Balakrishnan et al reported on the comparison of clinical exam and EMG in predicting site of lesions in brachial plexus injuries. The combination of EMG and exam localized the nerve injury in 80%, while the paraspinal EMG was the most sensitive solitary examination method (67%).
Illustration A shows a diagram of the brachial plexus. Incorrect Answers:
2-5: These muscles are all innervated by nerves that come from the brachial
plexus, and would be affected with a postganglionic injury.

Dislocation after total hip arthroplasty is a multifactorial problem. Numerous risk factors may act independently or cumulatively to increase the risk of this complication. Previous hip surgery of any kind is associated with a twofold increased risk for dislocation. Other risk factors include female gender, impaired mental status, inflammatory arthritis, and older age. Numerous studies have shown a lower dislocation rate with a direct lateral approach, although surgical techniques such as capsular repair have significantly lowered the incidence of dislocation after using the posterior approach. Metal-on-metal bearings have been associated with other complications such as adverse tissue reactions but are often used with larger-diameter bearings, which pose a lower risk of dislocation.
**Question 2** A patient has pain 2 years after undergoing a metal-on-metal (MOM) left total hip arthroplasty (THA). Which test(s) best correlate with a prognosis if this patient is having a reaction to metal debris?
1. Erythrocyte sedimentation rate, C-reactive protein, and white blood cell count
2. Serum cobalt and chromium ion levels
3. MRI with metal artifact reduction sequence (MARS)
4. CT of pelvis
CORRECT ANSWER: C DISCUSSION:
Painful MOM THA and taper corrosion can cause substantial damage to a patient's hip if left untreated. In this case, the workup for a painful MOM THA starts the same as a workup for a painful metal-on-polyethylene bearing couple. Infection must be ruled out in every case with a set of inflammatory markers. If these markers are remotely elevated, this is an indication for joint aspiration. In patients with metal debris, the pathology report often indicates too many cells to count or cellular debris. Metal ion levels do not seem to correlate with prognosis. There are well-functioning patients with high ion levels and poor-functioning patients with low ion levels. Advanced imaging with MARS MRI to evaluate for peritrochanteric fluid collection, a soft-tissue mass, or synovial/capsular hypertrophy will reveal signs of a metal reaction that indicate the need for a revision discussion. A CT scan can show more advanced bony destruction as an indicator of poor prognosis. These films can be used to determine the need for a structural graft or augments for reconstruction of bone loss attributable to metal debris.
**Question 3** Figures below demonstrate the radiographs obtained from a 35-year-old woman with end-stage debilitating osteoarthritis of the right hip. She is contemplating total hip arthroplasty (THA). She has a history of right hip dysplasia and underwent hip osteotomy as an adolescent. Over the years, nonsurgical treatment, including weight loss, activity modifications, and intra-articular injections, has failed. Her infection work-up reveals laboratory findings within defined limits. A further work-up reveals elevations in serum cobalt and chromium levels and fluid collections surrounding the hip on MRI with MARS. Revision THA is recommended. The most common complication following revision of a failed metal-on-metal hip arthroplasty is

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1. infection.
2. instability.
3. loosening.
4. periprosthetic fracture.
CORRECT ANSWER: B DISCUSSION:
THA has proven durable and reliable for pain relief and improving function for patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. A metal-on-metal articulation is associated with excellent wear rates in vitro. With its capacity to offer a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis with potential transfer of metal ions across the placental barrier make metal-on-metal bearings less desirable and relatively contraindicated for younger women of childbearing age. The workup of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including sedimentation rate, CRP, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging including MARS MRI should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so, when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cellcounts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following revision of failed metal-on-metal hip replacements.
**Question 4** Figure 1 shows the radiograph and Figure 2 shows the MRI scan obtained from a 37-year-old woman with a 2-month history of left hip pain. Which combination of a single symptom and examination finding is most likely in this scenario?

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D. Buttock pain; pain with hip extension, adduction, and external rotation while prone
1. Pain during sitting; flexion abduction and external rotation of the hip
2. Groin pain; pain with internal rotation and adduction while supine with the hip and knee flexed 90°
3. Clicking; abductor lurch
CORRECT ANSWER: B DISCUSSION:
MRI reveals an anterior labral tear, and the radiograph shows minimal arthritis with possible dysplasia. The most common location of pain in patients with a labral tear is the groin, and the most common physical finding is a positive impingement test result. Pain during sitting, clicking, and buttock pain are frequently described by patients with a labral tear, but these symptoms are less common than groin pain. A positive posterior impingement test finding is more common in patients with a posterior labral tear. Although age over 40 years and a body mass index higher than 30 can adversely affect clinical outcomes after joint preservation procedures such as PAO, hip arthroscopy, and femoral acetabular impingement surgery, the presence of hip arthritis on presurgical radiographs is the most commonly mentioned cause of failed hip joint preservation surgery. Tönnis grade is a radiographic measure of hip arthritis. A higher Outerbridge score is associated with more frequent poor outcomes after hip arthroscopy; however, the Outerbridge cartilage score is determined by direct visualization at the time of surgery. The Outerbridge score cannot be determined presurgically.
**Question 5** Figures 1 and 2 demonstrate the radiographs obtained from a 35-year-old woman with end-stage debilitating osteoarthritis of the right hip. She is contemplating total hip arthroplasty (THA). She has a history of right hip dysplasia and underwent hip osteotomy as an adolescent. Over the years, nonsurgical treatment, including weight loss, activity modifications, and intra-articular injections, has failed. Her infection work-up reveals laboratory findings within defined limits.The patient undergoes successful primary THA with a metal-on-metal bearing. At 1-year follow-up, she reports no pain and is highly satisfied with the procedure. However, 3 years after the index procedure, she reports atraumatic right hip pain that worsens with activities. Radiographs reveal the implants in good position with no sign of loosening or lysis. An initial laboratory evaluation reveals a normal sedimentation rate and C-reactive protein (CRP) level. The most appropriate next diagnostic step is

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1. MRI with metal artifact reduction sequence (MARS) only.
2. serum cobalt only.
3. serum cobalt and chromium levels.
4. serum cobalt and chromium levels and MRI with MARS.
CORRECT ANSWER: D DISCUSSION:
THA has proven to be durable and reliable for pain relief and improvement of function in patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. A
metal-on-metal articulation is associated with excellent wear rates in vitro. Because it offers a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions—including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis after the possible transfer of metal ions across the placental barrier—make metal-on-metal bearings less desirable and relatively contraindicated for younger women of child-bearing age.The work-up of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including the erythrocyte sedimentation rate, C-reactive protein (CRP) level, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging, including MRI with MARS, should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cell counts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following a revision of failed metal-on-metal hip replacements.
**Question 6** A 59-year-old woman with a history of osteoporosis is involved in a high-speed motor vehicle accident, resulting in left hip pain and deformity. The initial radiograph from the trauma bay is shown in Figure 1. Postreduction CT is shown in Figures 2 through 4. What is the most appropriate definitive surgical treatment?

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1. Open reduction and internal fixation (ORIF) of the acetabular fracture with concomitant acute total hip arthroplasty
2. ORIF of the acetabular fracture and ORIF of the femoral head fracture fragments
3. ORIF of the acetabular fracture and hemiarthroplasty
4. Skeletal traction with delayed total hip arthroplasty after the acetabular fracture has healed
CORRECT ANSWER: A
DISCUSSION:
The radiograph shows a posterior wall acetabular fracture-dislocation. Post reduction CT indicates a large comminuted posterior wall fracture with marginal impaction of the articular surface. A comminuted femoral head fracture also is seen extending to the superior weight-bearing surface. Given the marginal
impaction of the acetabulum and the considerable comminution of the femoral head (which is likely unreconstructible), this injury would have a high risk of causing posttraumatic arthritis if treated with ORIF of the fractures alone. Considering this fact and the patient’s age, ORIF of the posterior wall and acute total hip arthroplasty would likely have the best functional result and the lowest risk of reoperation. Hemiarthroplasty is inappropriate for this injury considering the acetabular fracture. Skeletal traction currently plays a limited role in the definitive treatment of acetabular fractures.
**Question 7** Figures below show the radiographs, MRI, and MR arthrogram obtained from a 25-year-old collegiate soccer player who has new-onset left groin pain. He played competitive soccer from a young age and has competed or practiced 5 to 6 times per week since the age of 10. He denies any specific hip injury that necessitated treatment, but his trainer contends that he had a groin pull. He reports groin pain with passive flexion and internal rotation of the left hip, and his hip has less internal rotation than his asymptomatic right hip. He is otherwise healthy. What is the primary cause of a cam deformity?

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1. A genetic problem
2. Repetitive activities involving an open proximal femoral physis
3. Early closure of the proximal femoral physis
4. Hip dysplasia
CORRECT ANSWER: B DISCUSSION:
Multiple studies have confirmed that cam or pincer anatomy is commonly present in asymptomatic hips. According to a large systematic review, cam deformities are present in approximately one-third of asymptomatic hips in young adults, and the proportion is higher than 50% in the subgroup of athletes. Ganz and associates proposed that femoral acetabular impingement is the root cause of osteoarthritis in most nontraumatic, nondysplastic hips, and functional improvement with surgical correction of the deformity has been demonstrated. Despite the link between cam deformity and hip osteoarthritis, a corresponding link between the correction of the deformity and prevention of osteoarthritis has never been proven. The results of cam deformity correction, typically including repair of the degenerative labral tear, are much poorer when substantial joint space loss is present. A typical joint space cutoff of 2 mm or less is used to recommend against hip preservation surgery.
**Question 8** Figures below show the radiographs, and the CT obtained from a 58-year-old woman who underwent cementless left total hip arthroplasty. Nine months after surgery, she continued to have groin pain when actively flexing her hip. She has trouble walking up stairs and getting out of her car. A course of appropriate nonsurgical treatment failed. What is the next step in definitive treatment?

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1. Acetabular component revision
2. Femoral component revision
3. Acetabular liner exchange
4. Trochanteric bursectomy
Submit Answer
**Question 9** What factor is associated with a high risk of developing pseudotumors after metal-on-metal hip resurfacing?
1. Large-diameter components
2. Age 40 or older for men
3. Age 40 or younger for women
4. Diagnosis of primary osteoarthritis
CORRECT ANSWER: C DISCUSSION:
The recent experience of a large clinical cohort revealed the most likely risk factors as being female gender, age younger than 40, small components, and a diagnosis of hip dysplasia causing osteoarthritis. Failure was least likely among men and after procedures involving larger components. These data have prompted some authors to caution against using metal-on-metal hip resurfacing in women and to primarily target candidates who are men younger than age 50. Small components may be more prone to failure because of malpositioning and edge loading, which have been noted to be more common in dysplasia cases.
**Question 10** Figures below show the radiographs, MRI, and MR arthrogram obtained from a 25-year-old collegiate soccer player who has new-onset left groin pain. He played competitive soccer from a young age and has competed or practiced 5 to 6 times per week since the age of 10. He denies any specific hip injury that necessitated treatment, but his trainer contends that he had a groin pull. He reports groin pain with passive flexion and internal rotation of the left hip, and his hip has less internal rotation than his asymptomatic right hip. He is otherwise healthy.When counseling patients who have a cam deformity, the orthopaedic surgeon should note that

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1. osteoarthritis of the hip is likely to occur later in life.
2. correction prevents later development of osteoarthritis.
3. most acetabular tears are symptomatic, and surgical treatment will be necessary.
4. this is an inherited deformity.
CORRECT ANSWER: A DISCUSSION:
Multiple studies have confirmed that cam or pincer anatomy is commonly present in asymptomatic hips. According to a large systematic review, cam deformities are present in approximately one-third of asymptomatic hips in young adults, and the proportion is higher than 50% in the subgroup of athletes. Ganz and associates proposed that femoral acetabular impingement is the root cause of osteoarthritis in most nontraumatic, nondysplastic hips, and functional improvement with surgical correction of the deformity has been demonstrated. Despite the link between cam deformity and hip osteoarthritis, a corresponding link between the correction of the deformity and prevention of osteoarthritis has never been proven. The results of cam deformity correction, typically including repair of the degenerative labral tear, are much poorer when substantial joint space loss is present. A typical joint space cutoff of 2 mm or less is used to recommend against hip preservation surgery.
**Question 11** Figures below demonstrate the radiographs obtained from a 63-year-old man who had right total hip arthroplasty (THA) 4 months ago. Progressive stiffness began 2 months after surgery, and he now reports pain only after prolonged physical activity. His examination reveals a normal gait and painless range of motion with flexion of 70°, extension of 0°, internal rotation of 20°, external rotation of 20°, abduction of 10°, and adduction of 10°. His erythrocyte sedimentation rate and C-reactive protein level are within defined limits. Physical therapy has produced no benefit. What is the most appropriate next step?

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1. 25 mg of indomethacin 3 times daily for 6 weeks
2. 1 dose of irradiation at 800 Gy
3. Surgical excision of heterotopic ossification (HO)
4. Reevaluation in 6 months
CORRECT ANSWER: D DISCUSSION:
This patient presents with HO 4 months after undergoing THA. Symptomatic HO may complicate nearly 7% of primary THA cases. Improvement in pain is expected within 6 months, and most patients will not need surgical treatment. Surgical excision may be warranted for symptomatic patients after full maturation of the HO, usually 6 to 18 months after the surgery. Patients can be followed with repeated serum alkaline phosphatase levels, which are elevated initially and should return to normal upon maturation of the HO. Alternatively, a bone scan can show decreased activity after the HO has matured. Twenty-five milligrams of indomethacin 3 times daily for 6 weeks or 1 dose of irradiation at 700 to 800 Gy is effective in the prevention of HO but not for the treatment of established HO.
**Question 12** A 55-year-old man is about to undergo right total hip arthroplasty. A preoperative AP pelvis radiograph is shown in Figure below. The final acetabular component and polyethylene liner are implanted. With the broach in place, the surgeon trials a standard offset neck and neutral length femoral head. The leg lengths are approximately equal, but the hip is unstable. What is the best next step?

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1. Choosing a longer femoral head and accepting a resulting leg-length discrepancy
2. Trialing a lateralized femoral neck component
3. Removing the acetabular liner and implanting an offset liner instead
4. Performing a trochanteric osteotomy with advancement
CORRECT ANSWER: B
DISCUSSION:
The radiograph shows that this patient has a high offset varus femoral morphology of both hips. Preoperative templating would identify this, and the surgeon should choose an implant system that has extended offset options to help match the native anatomy and biomechanics and minimize the risk of instability. Trialing a high offset neck, rather than a standard offset neck, is the next most appropriate step. Depending on the design of the implant system, this step can be accomplished by direct medialization of the femoral head, which would not affect leg length, or by lowering the neck angle, which would affect the leg length and would require a longer femoral head, because the leg lengths had previously been equal. Placement of a longer femoral head would likely improve hip stability but would also make the leg length uneven, which is a common cause of dissatisfaction after total hip arthroplasty. An offset acetabular liner also increases the leg length and does not correct the issue, which is on the femoral side. Trochanteric
advancement is sometimes used as a treatment for instability but would be inappropriate as the next step in this setting.
**Question 13** During total hip arthroplasty, what characteristic of irradiated (10 Mrad) and subsequently melted highly cross-linked polyethylene should provide a more wear-resistant construct than traditional gamma-irradiated (2.5-4 Mrad)-in-air polyethylene mated with the same head?
1. Resistance to adhesive wear
2. Resistance to abrasive wear
3. Resistance to fatigue wear
4. Resistance to creep
CORRECT ANSWER: B
DISCUSSION:
Highly cross-linked polyethylene makes material resistant to adhesive wear. Abrasive wear from third bodies does not decrease wear. The fatigue strength of such material is inferior to that of traditional polyethylene, and its resistance to creep is the same, if not lower, than that of traditional polyethylene.
**Question 14** When compared with patients having a body mass index (BMI) lower than 35, patients with a BMI above 40 who undergo primary total hip arthroplasty (THA) and total knee arthroplasty (TKA) are
likely to have
1. smaller incisions.
2. more wound complications.
3. fewer 30-day and 90-day readmissions.
4. lower rates of patient satisfaction.
CORRECT ANSWER: B
DISCUSSION:
The obesity epidemic is increasing, and the number of patients with a BMI higher than 35 undergoing THA and TKA also is growing. Controversy exists over the optimal BMI cutoff and the ability to perform joint replacements safely in patients who are morbidly obese. Several clinical series and national database analyses have shown that morbidly obese patients undergoing THA or TKA are at increased risk for wound complications as well as 30-day and 90-day readmissions. These patients’ incisions are typically larger because of the size of the soft-tissue envelope. Although the clinical scores following successful THA or TKA often are lower than the scores of controls, the overall changes in clinical function and satisfaction are equivalent in nonobese and obese patients.
**Question 15** An otherwise healthy 76-year-old woman has pain 2 years after total hip arthroplasty. The clinical photograph in Figures below demonstrates her skin envelope, and associated radiograph. Her C-reactive protein level is normal, and her erythrocyte sedimentation rate is mildly elevated. The white blood cell count is normal. Hip aspiration attempted under fluoroscopy generates no fluid. What is the best definitive treatment?

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1. Repeat left hip aspiration
2. Initiation of a wound care consult and oral antibiotics
3. Irrigation and debridement with closure of the dehisced wound, performance of a liner exchange, and administration of intravenous antibiotics
4. Debridement of the wound, explant of the total hip, placement of a spacer, and administration of intravenous antibiotics
CORRECT ANSWER: D
DISCUSSION:
This patient clearly has a chronically infected total hip arthroplasty, indicated by the open, draining sinus, as well as trochanteric bone resorption on radiographs, and two years of pain. Recently, specific guidelines have been published to better help the clinician define infection. Repeating the hip aspiration is unnecessary, because infection is already evident. Initiating a wound care consult would not address the underlying infection. The determination whether to retain the components or perform a two-stage exchange is based more on the acuity of infection. In this particular case, the patient is chronically infected. Irrigation and debridement with a liner exchange and retention of the components are reserved for the acute setting.
**Question 16** Figures below show the radiographs obtained from a 90-year-old woman who is seen in the emergency department after a fall from a height. She has right hip and thigh pain and is unable to bear weight. Based on this patient's history and imaging, what is the best next step?

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1. Hip revision and implantation of a proximal femoral replacement
2. Hip revision and implantation of a tapered fluted stem
3. Open reduction and internal fixation with a locked plate and allograft struts
4. Erythrocyte sedimentation rate and C-reactive protein laboratory studies
CORRECT ANSWER: D
DISCUSSION:
Periprosthetic fracture is the third most common reason (after loosening and infection) for revision surgery after total hip arthroplasty (THA). Late periprosthetic fracture risk is 0.4% to 1.1% after primary
THA and 2.1% to 4% after revision THA. Risk factors for periprosthetic fracture include age over 70 years, decreasing bone mass, and loosening of implants and osteolysis. The risk of concomitant infection in the presence of a periprosthetic fracture is 11%, according to Chevillotte and associates. Obtaining presurgical aspiration or intrasurgical tissue for culture is recommended if concomitant infection is suspected.
**Question 17** Figure below shows the radiograph obtained from a 73-year-old woman who returns status post total hip arthroplasty 14 years earlier. She denies pain and has no discomfort on examination. She then undergoes revision total hip arthroplasty with head and liner exchange and bone grafting. After a physical therapy session two days after surgical intervention, she develops inability to dorsiflex the foot while she is sitting in a chair. The initial treatment should consist of

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1. lying completely supine in bed.
2. remaining seated and placing the postsurgical leg on a stool.
3. transferring back to bed with the head of the bed no lower than 60°.
4. transferring back to bed with the head of the bed level and the surgical knee flexed.
CORRECT ANSWER: D
DISCUSSION:
Gamma irradiation produces free radicals. Although these free radicals can form cross-links with other polyethylene chains, the free radicals can also form a bond with oxygen, resulting in early oxidation. Gamma irradiation in air produces the highest risk for oxidized polyethylene, resulting in the highest risk for wear, delamination, and subsequent osteolysis. This patient demonstrates severe periarticular osteolysis. When she is asymptomatic, this suggests the acetabular and femoral components remain well fixed to the bone. Consequently, she can be treated by removing the wear generator (polyethylene exchange), along with bone grafting of the osteolytic defect. Considering the extensive amount of osteolysis indefinite observation would not be appropriate. A foot drop develops 2 days after surgery. As a result, it can be assumed that the nerve was not injured directly during the surgical procedure. Although MRI or CT may be indicated to identify an evolving hematoma, the immediate concern is to minimize pressure on the sciatic nerve. Tension on the nerve can be reduced by flexing the surgical knee and positioning the bed flat.
**Question 18** Figure below depicts the radiograph obtained from a 52-year-old woman who has leg-length inequality and chronic, activity-related buttock discomfort. This problem has been lifelong, but it is getting worse and increasingly causing back pain. What is the best current technique for total hip arthroplasty?

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1. High hip center
2. Anatomic hip center with trochanteric osteotomy and progressive femoral shortening
3. Anatomic hip center with subtrochanteric shortening osteotomy
4. Iliofemoral lengthening followed by an anatomic hip center
CORRECT ANSWER: C
DISCUSSION:
A high hip center is not recommended for Crowe type IV hips because of the lack of acetabular bone and altered hip biomechanics. An anatomic center is a better option but necessitates a technique to address the tight soft-tissue envelope. A trochanteric osteotomy with progressive femoral shortening has been described but can be prone to trochanter nonunion. Iliofemoral lengthening prior to surgery has been described but may not be tolerated by all patients. A shortening subtrochanteric osteotomy avoids trochanter nonunion and allows adjustment of femoral anteversion. Fixation of the osteotomy can include a stem with distal rotational control, plate fixation, a step versus oblique cut, or strut grafts.
**Question 19** Figures 1 through 5 show the radiographs, MRI, and MR arthrogram obtained from a 25-year-old collegiate soccer player who has new-onset left groin pain. He played competitive soccer from a young age and has competed or practiced 5 to 6 times per week since the age of 10. He denies any specific hip injury that necessitated treatment, but his trainer contends that he had a groin pull. He reports groin pain with passive flexion and internal rotation of the left hip, and his hip has less internal rotation than his asymptomatic right hip. He is otherwise healthy. Approximately what percentage of asymptomatic athletes have cam deformities of the hip?

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1. 5%
2. 10%
1. 25%
2. At least 50%
CORRECT ANSWER: D
DISCUSSION:
Multiple studies have confirmed that cam or pincer anatomy is commonly present in asymptomatic hips. According to a large systematic review, cam deformities are present in approximately one-third of asymptomatic hips in young adults, and the proportion is higher than 50% in the subgroup of athletes. Ganz and associates proposed that femoral acetabular impingement is the root cause of osteoarthritis in most nontraumatic, nondysplastic hips, and functional improvement with surgical correction of the deformity has been demonstrated. Despite the link between cam deformity and hip osteoarthritis, a corresponding link between the correction of the deformity and prevention of osteoarthritis has never been proven. The results of cam deformity correction, typically including repair of the degenerative labral tear, are much poorer when substantial joint space loss is present. A typical joint space cutoff of 2 mm or less is used to recommend against hip preservation surgery.
**Question 20** A 59-year-old active woman undergoes elective total hip replacement in which a posterior approach is used. She has minimal pain and is discharged to home 2 days after surgery. Four weeks later, she dislocates her hip while shaving her legs. She undergoes a closed reduction in the emergency department. Postreduction radiographs show a reduced hip with well-fixed components in satisfactory alignment. What is the most appropriate management of this condition from this point forward?
1. Observation and patient education regarding hip dislocation precautions
2. Revision to a larger-diameter femoral head
3. Revision to a constrained acetabular component
4. Application of a hip orthosis for 3 months
CORRECT ANSWER: A
DISCUSSION:
First-time early dislocations are often treated successfully without revision surgery, especially when no component malalignment is present. In this clinical scenario, it appears the patient would benefit from better education about dislocation precautions. Hip orthoses are of questionable benefit unless the patient is cognitively impaired. Revision surgery can be successful but is usually reserved for patients with recurrent dislocations.
**Question 21** A 62-year-old active man returns for routine follow-up 16 years after hip replacement. He has no hip pain. Radiographs reveal a well-circumscribed osteolytic lesion around a single acetabular screw. All hip components are perfectly positioned. Comparison radiographs obtained 6 months later show an increase in the size of the osteolytic lesion. CT depicts a well-described lesion that is 3 cm at its largest diameter and is localized around one screw hole with an eccentric femoral head. What treatment is appropriate, assuming that well-fixed cementless total hip components are in place?
1. Revision of the polyethylene liner, removal of the screw, and debridement of the osteolytic lesion with or without bone grafting
2. Revision of the acetabular component to a newer design without screws
3. Removal of the screw, revision of the polyethylene liner, and stem cell injection into the lytic lesion
4. Removal of the offending screw from the metal socket and placement of a new polyethylene liner in the existing socket
CORRECT ANSWER: A
DISCUSSION:
Given a well-fixed acetabular metal shell and a localized osteolytic lesion, good outcomes can be expected from liner revision in this clinical scenario with retention of the metal socket, assuming no damage to the components or other unexpected findings arise during revision surgery. Here, complete cup revision is not warranted, considering the appropriate implant position. Beaulé and associates reviewed 83 consecutive patients (90 hips) in whom a well-fixed acetabular component was retained in a clinical scenario such as the one described. No hip showed recurrence or expansion of periacetabular osteolytic lesions. If the metal cup is unstable, acetabular component revision may be indicated.
**Question 22** Figure 1 shows the radiograph obtained from a 78-year-old woman who has a recent history of increasing thigh pain 12 years after undergoing total hip arthroplasty. Figure 2 depicts the radiograph obtained after she fell and was unable to ambulate. What is the most appropriate treatment?

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1. Application of a femoral cable plate
2. Application of cerclage-wired double allograft femoral struts
3. Femoral revision with an uncemented long stem
4. Femoral revision with a cemented long-stem prosthesis
CORRECT ANSWER: C
DISCUSSION:
The surgical treatment of periprosthetic fractures of total hip replacement with a loose implant and progressive bone loss is associated with a high complication rate. The recent literature would favor the use of long "Wagner-type" stems, which have a long distal taper that may optimally engage the remaining femoral shaft isthmus. Plating options are problematic, because the intramedullary stem limits the ability to use screws with the plate. Using long distally fixed stems circumvents this problem by enhancing fracture healing and creating a long-term prosthetic solution in these most difficult cases.
**Question 23** Early postoperative infections following primary total hip arthroplasty are most likely caused by which organism?
1. Staphylococcus epidermidis
2. Streptococcus viridans
3. Propionibacterium acnes
4. Staphylococcus aureus
CORRECT ANSWER: D
DISCUSSION:
_S aureus is the most common organism cultured in early (fewer than 4 weeks postoperative) periprosthetic infections. Methicillin-resistant S aureus is becoming a more common pathogen in certain patient populations. B hemolytic Streptococcus and some gram-negative infections can also be found in early postoperative infections. S epidermidis, S viridans, and P acnes are more commonly found in late (more than 4 weeks postoperative) infections._
**Question 24** A healthy, active 72-year-old man trips and falls, landing on his left hip 10 weeks after an uncomplicated left primary uncemented total hip replacement. A radiograph taken 6 weeks after surgery and before the fall is shown in Figure 1. A radiograph taken after the fall is shown in Figure 2. He is unable to bear weight and is brought to the emergency department. Examination reveals a slightly shortened left lower extremity and some mild ecchymosis just distal to the left greater trochanteric region, but his skin is intact, without abrasions or lacerations. What is the most appropriate treatment?

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1. Open reduction and cerclage fixation of the fracture
2. Open reduction and revision of the femoral implant to a long cemented stem
3. Open reduction and revision of the femoral implant to a long fluted and tapered uncemented stem
4. Application of balanced traction followed by surgery after the ecchymosis has resolved
CORRECT ANSWER: D
DISCUSSION:
This patient has a periprosthetic femoral fracture with a loose femoral stem and normal femoral bone stock, representing a Vancouver type B2 fracture. The most appropriate treatment is fixation of the fracture, along with revision of the stem. Considering his age, bone quality, and activity level, a longer uncemented stem is most predictable. Although a cylindrical stem may also be used, the fluted stem option is the only uncemented choice listed and is the most appropriate option. A cemented stem is a poorer choice because it is difficult to keep the cement out of the fracture site, which would pose a risk for nonunion at the fracture. Also, overall poorer results have been associated with long cemented stems in healthy, active people. Surgery does not need to be delayed to allow the ecchymosis to resolve, and simple open reduction and fixation does not address the loose stem.
**Question 25** A 70-year-old man undergoes removal of an infected total hip arthroplasty (THA) and insertion of an articulating antibiotic-loaded spacer to treat a deep periprosthetic hip infection. While in a nursing home receiving intravenous antibiotics 3 weeks after surgery, the patient trips and falls. Examination reveals swelling in the mid and distal thigh, intact skin and neurovascular structures, and severe pain with knee or hip movement. Radiographs of the femur are shown in Figures 1 through 4. What is the most appropriate treatment for the fracture below the implant?

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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/HK-3_Fig-06a-1543610199711.jpg)
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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/HK-3_Fig-06a-1543610199711.jpg)
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1. Balanced traction to address concern for persistent infection with reoperation
2. Open reduction and internal fixation of the fracture with a lateral plate and screws
3. Removal of the articulating spacer and revision to a longer-stem antibiotic-loaded articulating spacer
4. Removal of the articulating spacer and reimplantation using a long-stem fluted uncemented hip replacement
CORRECT ANSWER: B
DISCUSSION:
This patient has a type C periprosthetic femoral fracture. The articulating spacer is not involved in the fracture, which is well distal to the implant. The most appropriate treatment is open reduction and internal fixation of the fracture. Traction is not appropriate for this fracture because the injury can be treated surgically despite the history of previous hip infection. Traction would also be needed for at least 5 weeks and would delay the surgical treatment of the periprosthetic fracture until the time of second-stage revision THA. The fracture is fairly distal, and revision to a longer antibiotic-loaded implant or uncemented stem is not suitable for this fracture pattern, because it extends well past the isthmus. A femoral stem in the distal fragment would provide little stability for the fracture. Removal of the articulating spacer and reimplantation using a long-stem fluted uncemented hip replacement is not appropriate, because it would be premature to reimplant the man's hip while he is still receiving treatment for a deep hip infection.
**Question 26** Figures 1 and 2 demonstrate the radiographs obtained from a 35-year-old woman with end-stage debilitating osteoarthritis of the right hip. She is contemplating total hip arthroplasty (THA). She has a history of right hip dysplasia and underwent hip osteotomy as an adolescent. Over the years, nonsurgical treatment, including weight loss, activity modifications, and intra-articular injections, has failed. Her infection work-up reveals laboratory findings within defined limits. Which bearing surface is contraindicated for this patient?

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1. Ceramic-on-ceramic
2. Ceramic-on-highly cross-linked polyethylene (HXPE)
3. Metal-on-HXPE
4. Metal-on-metal
CORRECT ANSWER: D
DISCUSSION:
THA has proven durable and reliable for pain relief and improving function for patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. A metal-on-metal articulation is associated with excellent wear rates in vitro. With its capacity to offer a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis with potential transfer of metal ions across the placental barrier make metal-on-metal bearings less desirable and relatively contraindicated for younger women of childbearing age. The workup of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including sedimentation rate, CRP, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging including MARS MRI should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so, when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cell counts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following revision of failed metal-on-metal hip replacements.
**Question 27** Figures below show the radiograph and the MRI scan obtained from a 37-year-old woman with a 2-month history of left hip pain. Which presurgical factor is most commonly associated with a poor outcome after a hip joint salvage procedure?

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1. Age older than 40 years
2. Body mass index higher than 30
3. Tönnis grade of 2 or higher
4. Outer bridge grade of III or IV
CORRECT ANSWER: C
DISCUSSION:
MRI reveals an anterior labral tear, and the radiograph shows minimal arthritis with possible dysplasia. The most common location of pain in patients with a labral tear is the groin, and the most common physical finding is a positive impingement test result. Pain during sitting, clicking, and buttock pain are frequently described by patients with a labral tear, but these symptoms are less common than groin pain. A positive posterior impingement test finding is more common in patients with a posterior labral tear. Although age over 40 years and a body mass index higher than 30 can adversely affect clinical outcomes after joint preservation procedures such as PAO, hip arthroscopy, and femoral acetabular impingement surgery, the presence of hip arthritis on presurgical radiographs is the most commonly mentioned cause of failed hip joint preservation surgery. Tönnis grade is a radiographic measure of hip arthritis. A higher Outerbridge score is associated with more frequent poor outcomes after hip arthroscopy; however, the
Outerbridge cartilage score is determined by direct visualization at the time of surgery. The Outerbridge score cannot be determined presurgically.
**Question 28** Figure below shows the radiograph obtained from a 68-year-old man who fell 3 weeks after undergoing a successful left primary total hip arthroplasty. He is experiencing a substantial increase in pain and an inability to bear weight. What is an appropriate treatment plan?

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1. Open reduction and internal fixation (ORIF) of the fracture
2. Removal of the current stem, femur ORIF, and insertion of a longer revision stem
3. Femur ORIF with cables and strut graft, leaving the current stem in situ
4. Femur ORIF combined with reimplantation of the primary component
CORRECT ANSWER: B
DISCUSSION:
The fracture has occurred around the stem, representing a Vancouver type B fracture, and the stem is clearly loose, making it a type B2 fracture. The appropriate treatment is removal of the loose in situ stem; ORIF of the femur using cerclage wires, cables, or a plate; and insertion of a longer revision stem such as a tapered fluted modular titanium or fully porous coated cylindrical stem to bypass the fracture. All of the other options are incorrect, because they represent inappropriate treatment options for a Vancouver type B2 fracture.
**Question 29**
What factor is associated with a higher risk of dislocation after total hip arthroplasty?
1. Male gender
2. Previous hip surgery
3. A direct lateral surgical approach
4. Metal-on-metal bearing surfaces
CORRECT ANSWER: B
DISCUSSION:
Dislocation after total hip arthroplasty is a multifactorial problem. Numerous risk factors may act independently or cumulatively to increase the risk of this complication. Previous hip surgery of any kind is associated with a twofold increased risk for dislocation. Other risk factors include female gender, impaired mental status, inflammatory arthritis, and older age. Numerous studies have shown a lower dislocation rate with a direct lateral approach, although surgical techniques such as capsular repair have
significantly lowered the incidence of dislocation after using the posterior approach. Metal-on-metal bearings have been associated with other complications such as adverse tissue reactions but are often used with larger-diameter bearings, which pose a lower risk of dislocation.
**Question 30** Figures below show the radiographs obtained from a 19-year-old woman with a 3-year history of progressive hip pain in the left groin with activity, which is unresponsive to activity modification and physical therapy. Examination reveals normal range of motion, with pain on anterior impingement testing. What treatment is associated with the best long-term results?

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1. Hip arthroscopy with labral repair
2. Reverse periacetabular osteotomy
3. Varus rotational osteotomy
4. Open surgical dislocation with rim trimming
CORRECT ANSWER: B
DISCUSSION:
This patient has symptomatic femoroacetabular impingement as well as clinical and radiographic signs of acetabular retroversion, including a cross-over sign, ischial spine sign, and posterior wall sign bilaterally. Good midterm to long-term outcomes have been reported with reverse (anteverting) Bernese periacetabular osteotomy (PAO). In patients with less retroversion, open or arthroscopic rim trimming with labral refixation have shown good short-term results, but longer-term results have yet to be fully delineated. Isolated hip arthroscopy and labral repair would not be indicated without addressing the retroversion deformity. Femoral varus rotational osteotomy plays no role in the treatment of this pathology. Open surgical dislocation with rim trimming could be considered in patients with less deformity, but some studies have shown inferior long-term results compared with reverse PAO.
**Question 31** Figure below depicts the radiograph obtained from a 30-year-old woman who began having more right than left hip pain during a recent pregnancy. Physical examination reveals increased range of motion with positive flexion abduction and external rotation and flexion adduction and internal rotation as well as pain with external logroll. Assessment of Figure below reveals

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1. classic dysplasia with volume deficient acetabula.
2. acetabular retroversion with positive crossover signs and ischial spine signs.
3. no substantial dysplasia, with normal acetabular volume and anteversion.
4. inadequate radiographic evidence to assess for hip dysplasia.
CORRECT ANSWER: D
DISCUSSION:
Studies have demonstrated that pelvic inclination can dramatically affect the interpretation of radiographs in the dysplastic hip, with 9° of increased pelvic inclination leading to the presence of crossover signs and posterior wall signs. A distance of 30 mm to 50 mm from the sacrococcygeal junction to the pubis is often used to assess the adequacy of pelvic inclination on radiographs, although Siebenrock and associates determined the mean difference to be 32 mm in men and 47 mm in women. In this patient, the pelvic inclination is dramatically increased, leading to overestimation of acetabular retroversion.
**Question 32** In patients with Crowe types III and IV developmental dysplasia of the hip with high hip centers, acetabular reconstruction often requires lowering the acetabular component into the native acetabulum. In doing so, considerable risk for limb lengthening beyond 4 cm exists, making the hip difficult to reduce and raising the risk for nerve injury. Which technique is used to overcome this problem?
1. Subtrochanteric osteotomy with femoral shortening
2. An offset femoral component
3. A lateralized liner
4. Extended trochanteric osteotomy
CORRECT ANSWER: A
DISCUSSION:
When substantial lengthening of a dysplastic hip will occur because a high dislocation is relocated into a considerably lower acetabulum, a femoral shortening may be necessary to reduce the hip and avoid a stretch injury to the sciatic nerve. No other choice specifically addresses the need for femoral shortening, and high offset stems and lateralized liners may exacerbate the problem if used alone and without femoral shortening.
**Question 33** Figures 1 through 3 show the radiograph and MR arthrograms obtained from a 25-year-old woman who has had right groin pain since joining the military 4 years ago. She has undergone treatment with NSAIDs, physical therapy, and activity modification. Examination reveals positive flexion abduction and external rotation, a positive external log roll, and increased range of motion. What is the most appropriate treatment?

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1. Viscosupplementation of the right hip
2. Hip arthroscopy with labral repair
3. Periacetabular osteotomy
4. Total hip arthroplasty
CORRECT ANSWER: C
DISCUSSION:
This patient has symptomatic hip dysplasia that has been recalcitrant to nonsurgical management. Radiographs reveal an upsloping sourcil (acetabular index of 18) and a lateral center edge angle of 14, with posterior uncovering. The MR arthrogram shows no definitive evidence of a labral tear. Appropriate surgical management would include periacetabular osteotomy. Viscosupplementation in the hip is controversial in the treatment of osteoarthritis and plays no role in the treatment of dysplasia. Hip arthroscopy with labral repair is controversial in mild hip dysplasia, with studies demonstrating between 60% and 77% good and excellent results, inferior to the results for hip arthroscopy in a femoroacetabular impingement cohort. In moderate to severe dysplasia, hip arthroscopy is not recommended. Because the acetabular cartilage is well maintained, total hip arthroplasty would not be recommended in this young and active patient.
**Question 34** Figures 1 and 2 show the radiographs obtained from a 68-year-old morbidly obese man who underwent left total hip replacement 7 years ago and did well, with no symptoms prior to the current presentation. He recently rose from a seated position and felt a pop in the hip, with immediate pain and inability to bear weight. Any pressure on the left foot now produces a painful, grinding sensation with loss of left hip stability. What is the best next step?

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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/540604F1-1543613620740.jpg)
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1. Revision of the acetabular implant to a constrained bearing with modular exchange of the femoral head and neck
2. Revision of the acetabular and femoral implants
3. Retention of the acetabular implant with modular exchange of the femoral head and neck
4. Revision of the femoral component alone with a new ceramic head
CORRECT ANSWER: B
DISCUSSION:
The modular femoral stem has fractured. Changing the liner to a constrained design is not warranted at this time based on the information provided. Revision of the acetabular implant is appropriate because of the potential for damage to the existing cup from metal debris and femoral implant contact and to convert from a metal-on-metal articulation. Nonsurgical management would not provide pain relief or improvement; revision of the total hip arthroplasty is recommended. The implant failed in a short time, and retention of the femoral stem is not recommended because of the concern for failure with only a neck exchange. A dual-mobility bearing may be a good option if the surgeon plans to retain the acetabular component. Extended trochanteric osteotomy is a useful technique for the removal of a well-fixed femoral implant. In this patient, femoral stem removal without
osteotomy would be difficult due to the fracture of the implant’s femoral neck and the inability to gain purchase for extraction.
**Question 35**
A 63-year-old woman had a primary total hip arthroplasty 7 years ago that included a proximally coated
titanium stem, a cobalt alloy femoral head, a titanium hemispherical acetabular component, and a polyethylene liner. She did well for 4 years but has now had two dislocations and reports pain and weakness around the left hip. She denies any fevers, chills, or constitutional symptoms. On examination, the patient walks well without any signs of an antalgic or Trendelenburg gait. Her abductor mechanism demonstrates good strength. Her erythrocyte sedimentation rate and C-reactive protein level are normal. On radiographs, all components appear well fixed and in good alignment. What is the most appropriate treatment at this time?
1. Physical therapy to improve hip stability
2. Use of an abduction brace to limit the patient’s range of motion
3. Conversion to a constrained acetabular liner
4. Cobalt and chromium serum metal ion level testing
CORRECT ANSWER: D
DISCUSSION:
Trunnionosis is a recently recognized complication following total hip arthroplasty and can occur when a cobalt alloy femoral head is used on a titanium alloy or cobalt alloy femoral stem. Patients often present with pain or swelling around the hip but at times can present with instability. Certain femoral stem designs have been associated with increased reports of trunnionosis. In a patient with a cobalt alloy femoral head who presents with instability, swelling, and weakness around the hip, the potential for trunnionosis and
an adverse local tissue reaction should be considered.
**Question 36** Figures below show the radiographs obtained from a 68-year old man with progressively worsening right side hip pain over the last 8 months. He is 6 feet tall, with a BMI of 51 kg/m2 and reports that his index total hip arthroplasty was performed 8 years ago. The preoperative work-up includes negative infectious laboratory results. What is the most appropriate surgical plan for revision of the femoral component in this patient?

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1. Superior approach with trochanteric slide
2. Direct anterior approach with a chevron modification of the standard greater trochanteric osteotomy
3. Lateral approach with a partial greater trochanter osteotomy
D. Posterolateral approach with an extended trochanteric osteotomy
Submit Answer
CORRECT ANSWER: D
DISCUSSION:
The patient’s radiographs demonstrate varus femoral remodeling around a broken cylindrical, distally fixed femoral stem. Proximal femoral remodeling around loose or fractured stems occurs in 21% to 42% of femoral revisions, based on the definitions outlined by Foran and associates. In definition 1, varus femoral remodeling occurs when the template falls within 2 mm of the endosteal cortex of the metaphysis on templating with a diaphyseal engaging stem. In definition 2, varus femoral remodeling = when the template crosses the lateral femoral cortex proximally. Based on the templating or drawing a line from the isthmus proximally along the lateral cortex, implantation of a straight stem would perforate the cortex proximally, indicating varus femoral remodeling. An extended trochanteric osteotomy would aid in the removal of the well-fixed distal segment and enable the safe insertion of the new femoral component. The approach is not the concern in this case, because extended trochanteric osteotomies have been described from the posterior and direct lateral approaches with excellent outcomes and union rates. The key is that the extended osteotomy is necessary and not a trochanteric slide or standard (shorter or incomplete trochanteric) osteotomy. These types would not provide access to the well-fixed distal stem, nor would they afford a straight tube in which to insert a new femoral component.
**Question 37** Figures 1 and 2 show the radiograph and CT obtained from a 78-year-old woman who underwent right total hip replacement in 1995. She initially did well with no pain. She was last seen 7 years ago and was having mild hip pain at that time. She was found to have a supra-acetabular cyst on radiographs. She has had severe right hip pain for the past 9 months while using a walker for ambulation. The initial blood work reveals an estimated erythrocyte sedimentation rate of 32 mm/hr, a C-reactive protein level of 0.5 mg/L, a serum cobalt level of 0.4 µg/L, and a serum chromium level of 0.6 µg/L. Right hip aspiration is performed, revealing a white blood cell count of 139, 52% neutrophils, and a negative leukocyte esterase test. What is the best next step?

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1. Acetabular revision, with placement of a custom triflange acetabular component and femoral head exchange
2. Removal of the femoral and acetabular components and placement of an antibiotic spacer, with 6 weeks of intravenous antibiotics
3. Head and liner exchange and retention of the femoral and acetabular implants with acetabular bone grafting
4. Nonsurgical management with the initiation of bisphosphonates and referral to pain management
CORRECT ANSWER: A
DISCUSSION:
The hip replacement was performed in 1995, during the period when the previous generation of polyethylene was utilized. This polyethylene was subjected to irradiation in air, with subsequent oxidation and consequent osteolysis after implantation. The mechanism of osteolysis begins with the uptake of polyethylene particles by macrophages, which then initiate an inflammatory cascade and the release of osteolytic factors. This cycle continues, with eventual implant loosening and failure. The imaging shows significant osteolysis and raises concern for pelvic discontinuity and acetabular implant failure. The surgical treatment consists of acetabular reconstruction. In this patient, concern exists for discontinuity based on the substantial amount of bone loss and nonsupportive anterior and posterior columns. This scenario requires complex acetabular revision using a custom triflange device, distraction with a jumbo acetabular component, or placement of a porous metal cup/cage construct with augmentation. The laboratory values are not consistent with infection or failure due to metal debris.
**Question 38** Figure below shows a cross-table lateral radiograph obtained from a healthy 56-year-old woman with recurrent hip dislocations 6 months after total hip arthroplasty performed through a posterolateral approach. Each dislocation occurred when she was bending over to put her shoes on or pick something up. She has dislocated four times and has had no pain between dislocations. Abductor strength is 5 out of
5/. The infection work-up is negative. What is the best next step?

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1. Revision of the acetabulum and evaluation of the femoral stem
2. Conversion to a constrained liner
3. Gluteus medius repair and application of a hip abductor brace
4. Revision to an elevated acetabular polyethylene liner
CORRECT ANSWER: A
DISCUSSION:
The cross-table lateral radiograph shows that the patient has decreased acetabular anteversion. She is likely impinging on her cup in flexion and levering the femoral component posteriorly. Given a well-fixed and well-aligned femoral component and a negative infection work-up, the preferred treatment is to revise the acetabulum with a goal of increasing acetabular anteversion to avoid prosthetic impingement. Conversion to a constrained or elevated rim liner is suboptimal in this setting, because the problem is impingement. Indications for a constrained liner are neuromuscular compromise, abductor deficiency, or instability despite well-fixed and well-placed components. Given her 5 of 5 abductor strength, gluteus medius repair is not indicated.
**Question 39** Figures below show the radiographs obtained from a 75-year-old woman who underwent right total hip arthroplasty in 2009. She did well until last month, when a right posterior hip dislocation occurred after she fell from her bed to the floor. Successful closed reduction was performed. She sustained two more posterior dislocations requiring closed reduction under anesthesia. The surgical report from the index arthroplasty notes a 54-mm monoblock acetabular component with a 28-mm inner diameter compression molded polyethylene and a high offset neck cementless stem with a +8-mm length, 28-mm head. What is the best next step?

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1. Hip spica cast placement
2. Acetabular revision arthroplasty
3. Resection arthroplasty
4. Femoral head revision to a 28-mm diameter, +10-mm length head
CORRECT ANSWER: B
DISCUSSION:
This patient has demonstrated recurrent instability, and her current implants lack the modularity to upsize and improve the head-neck ratio and range to impingement. Given the monoblock acetabular component and a +7-mm neck length, the best option is revision to a large-diameter femoral head or dual-mobility component. Placement of a hip spica cast and resection arthroplasty are unreasonable. Revision to a longer ball length likely would not solve this recurrent instability pattern.
**Question 40** According to Musculoskeletal Infection Society (MSIS) guidelines, which set of patient laboratory study results fits the definition of chronic prosthetic joint infection?
D. ESR 25 mm/hr, CRP 7 mg/L, joint aspiration WBC count 252, 82% neutrophils, and negative leukocyte esterase
1. Erythrocyte sedimentation rate (ESR) 50 mm/hr, C-reactive protein (CRP) 8 mg/L, joint aspiration white blood cell (WBC) count 542, 62% neutrophils, and positive leukocyte esterase
2. ESR 42 mm/hr, CRP 12 mg/L, joint aspiration WBC count 3,540, 72% neutrophils, and positive leukocyte esterase
3. ESR 20 mm/hr, CRP 15 mg/L, joint aspiration WBC count 4,135, 54% neutrophils, and negative leukocyte esterase
CORRECT ANSWER: B
DISCUSSION:
The MSIS definition of periprosthetic joint infection was updated in 2014 with two major and six minor criteria. The presence of one major criterion or three minor criteria is diagnostic for infection. The major criteria are two positive cultures with the same organism or a draining sinus tract. The current MSIS minor criteria are 1) an elevated ESR (more than 30 mm/hr) and CRP level (more than 10 mg/L), 2) an elevated synovial WBC count (more than 3,000 cells per/microliter), 3) an elevated synovial fluid polymorphonuclear count (more than 80%), 4) a positive histological analysis of periprosthetic tissue, and 5) a single positive culture.
**Question 41** Figures below show the AP and lateral radiographs obtained from a 54-year-old woman who has worsening groin pain 18 months after a primary left total hip arthroplasty. The pain is worst when climbing stairs, when rising from a seated position, and during resisted hip flexion. Her pain improved early after surgery but did
not completely resolve. Her C-reactive protein and erythrocyte sedimentation rate results of less than 1 mg/dL and 10 mm/hr, respectively, were obtained in the office. What is the best next step?

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1. MRI with MARS of the left hip
2. Revision of the left acetabular component
3. Intra-articular ultrasound-guided left hip injection
4. Physical therapy for the left hip
CORRECT ANSWER: B
DISCUSSION:
Iliopsoas impingement is a potential cause of persistent groin pain after a total hip arthroplasty. This patient’s history gives groin pain with resisted hip flexion and during activities that require this level of function. The radiographs depict an acetabular component with substantial retroversion. Typical options for the management of iliopsoas tendon impingement include injections, tenotomy, and acetabular revision. Recently, Chalmers and associates reported more predictable groin pain resolution with 8 mm or more of anterior acetabular component when overhang was revised. The radiographs clearly show more retroversion, with a cup prominence of more than 8 mm anteriorly. MRI with MARS could potentially help in the diagnosis of this impingement but would not help in management (option A). An ultrasound-guided injection would need to be administered into the iliopsoas tendon sheath to be of help and, in this case, would likely be performed for diagnostic purposes due to the extreme anterior overhang (option C). Option D would be useful for mild cases of iliopsoas impingement but likely would not help much in this more extreme case.
**Question 42** Figure 1 shows the radiograph obtained from a 67-year-old man recently diagnosed with osteoarthritis, 8 years after receiving a left metal-on-metal total hip arthroplasty (THA). The acetabular component has a modular cobalt alloy acetabular liner. The patient states that he did very well postoperatively, but for the last 6 months has noted worsening pain and swelling in his left hip. Serum metal ion testing reveals a chromium level of 12.4 ng/mL, compared with a normal level of less than 0.3 ng/mL, and a cobalt level of 11.8 ng/mL, compared with a normal level less than 0.7 ng/mL. An MRI with metal artefact reduction sequence (MARS) was performed and is shown in Figure 2. What is the most appropriate management at this time?

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A. Annual monitoring of serum metal ion levels
1. Repeated MRI with MARS in 6 months
2. Conversion of the THA to a cobalt alloy femoral head and polyethylene bearing
3. Conversion of the THA to a ceramic femoral head with an inner titanium sleeve and polyethylene bearing
CORRECT ANSWER: D
DISCUSSION:
Metal-on-metal THA was initially introduced in the 1990s, with the proposed advantages of decreased wear and improved stability. However, catastrophic adverse local tissue reactions associated with their use has raised numerous concerns. The work-up of a patient with a prior metal-on-metal total hip arthroplasty involves a thorough history and physical examination; blood analysis, including the erythrocyte sedimentation rate, C-reactive protein, and metal ion levels; and secondary imaging, including ultrasonography, CT, and MRI. In a patient with clinical symptoms, elevated metal ion levels, and a large fluid collection seen on MRI, the most appropriate treatment would be removal of the metal-on-metal bearing. Given the presence of an adverse reaction involving cobalt and chromium, a revision ceramic head may be most appropriate to avoid the potential of trunnion-associated corrosion.
**Question 43** Figures below depict the radiographs obtained from a 76-year-old woman with a painful total knee arthroplasty. She describes an uneventful recovery with no wound-healing issues and was pain free for the first 10 years. Although reporting no trauma or inciting event, she now describes pain in the entire knee that is most severe with her first few steps. She has begun to notice night pain and, more recently, constant swelling. What is the most appropriate work-up at this time?

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1. Knee aspiration with cell count/cultures, C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR), CT
2. Knee aspiration with cell count/cultures, CRP, ESR
3. Fresh-frozen specimen at the time of revision knee arthroplasty only
4. Technetium-99m bone scan, knee aspiration with cell count/cultures
CORRECT ANSWER: B
DISCUSSION:
An evaluation of the painful total knee must be supported by an understanding of the potential etiologies of pain. They may include, aseptic loosening, infection, osteolysis, gap imbalance, referred pain, stiffness, and complex regional pain syndrome. In this case, the patient demonstrates start-up pain and had no prior history of infections. Her radiographs show subsidence of the tibia, indicating a loose prosthesis. Knowing that the prosthesis is already loose precludes the need for a bone scan. It is, however, important to rule out infection in this case; therefore, CRP and ESR testing is essential. Aspiration is also recommended when going into knee arthroplasty, and infection is a concern.
**Question 44** The direct anterior (Smith-Peterson) approach to hip arthroplasty is most commonly associated with injury to what nerve?
1. Lateral femoral cutaneous
2. Sciatic
3. Pudendal
4. Superior gluteal
CORRECT ANSWER: A
DISCUSSION:
Some authors have reported the incidence of lateral femoral cutaneous nerve neuropraxia following hip arthroplasty with the direct anterior approach to be near 80%, but resolution of the sensory deficits has been observed in most patients over time. Femoral nerve palsy has been reported to occur in .64% to 2.3% direct lateral (Hardinge) and anterolateral (Watson-Jones) approaches, and the superior gluteal nerve may be injured with proximal extension of the abductor muscular dissection. The posterior approach has been reported to be associated with sciatic nerve injury, especially in cases of dysplasia. Pudendal nerve injury has not been reported with the anterior, anterolateral, direct lateral, or posterior approaches to hip
arthroplasty. It has been reported following hip arthroscopy and the use of a traction table, however.
**Question 45** A 55-year-old woman is referred for evaluation of a painful knee replacement. She underwent total knee arthroplasty (TKA) more than 1 year ago without perioperative complications but has had consistent pain since the surgery. The patient’s preoperative radiographs and postoperative radiographs are shown in Figures below. Examination reveals medial laxity during valgus stress testing and range of motion of 0° to 70°. Her erythrocyte sedimentation rate and C-reactive protein level are normal. What is the best next step?

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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/563538F1-1543610007742.jpg)
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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/563538F1-1543610007742.jpg)
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[](https://cdn.mycrowdwisdom.com/aaos/te-questions/563538F1-1543610007742.jpg)
1. Unloader brace
2. Distal femoral osteotomy
3. Open arthrofibrosis debridement with lateral ligament balancing and polyethylene exchange
4. Revision TKA of both the femoral and tibial components
CORRECT ANSWER: D
DISCUSSION:
The radiographs show substantial valgus malalignment of the femoral component, with lateral mechanical axis deviation. Clinically, by examination she displays instability and stiffness as a result. Revision knee replacement is appropriate and should consist of total revision to stemmed femoral and tibial components with a varus-valgus constrained insert, given the likely attenuation of the medial collateral ligament. Open debridement with ligament balancing and polyethylene exchange do not address the underlying cause and are inappropriate. Distal femoral osteotomy is not useful in the setting of previous total knee replacement. Nonsurgical treatment with an unloader brace would be ineffective in correcting the alignment.
**Question 46** A 45-year-old man has a draining sinus and recurrent infection of his right total knee arthroplasty. He has had two prior revision surgeries after the primary procedure and three other surgeries before his initial replacement, including a proximal tibial osteotomy and subsequent hardware removal. On clinical examination, he has a draining sinus in the mid portion of his surgical scar and a range of motion of 5° to 85°. AP and lateral radiographs of the right knee are shown in Figures below. During surgery, the femoral component is found to be grossly loose, but the tibial component is well fixed. What is the most appropriate extensile approach that would provide adequate exposure and aid in tibial component extraction?

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1. Extended medial parapatellar approach
2. Quadriceps snip
3. Extended tibial tubercle osteotomy
4. Medial epicondyle osteotomy
CORRECT ANSWER: C
DISCUSSION:
Extended tibial tubercle osteotomy is an extensile approach to revision total knee arthroplasty that affords excellent exposure and can facilitate removal of tibial sleeves and cones. This patient has had multiple surgeries, including a proximal tibial osteotomy, as well as poor range of motion, patella baja, and a well-fixed metaphyseal sleeve component. Classically, an extended tibial tubercle osteotomy provides outstanding exposure for component removal in the setting of prior high tibial osteotomy and patella baja. For this patient, it is important to recognize the patella baja on the radiographs, as well as the tibial sleeve. In many of these cases the osteotomy provides access to the sleeve to help with extraction, because the stem will not pull through the sleeve or detach from the tray to allow visualization of the sleeve. The extended medial parapatellar approach is just a long medial approach that typically yields good exposure
but would not help with the patella baja or extraction of the tibial sleeve. The quadriceps snip would give good exposure to the knee but would not aid in tibial component removal. Lastly, the medial epicondyle osteotomy could help with exposure and tensioning of the medial complex of the knee but would not help with tibial component extraction.
**Question 47** A 58-year-old woman underwent a left total knee arthroplasty 6 years ago. She initially did well after surgery but sustained a fall 2 months ago while at work. She now describes left knee pain and instability and an inability to straighten her knee since the fall. She has been using a hinged knee brace, which provides partial support. On examination, she has passive range of motion of 0° to 115° and active range of motion of 80° to -115°. Her radiographs are shown in Figures below. What is the best option for the restoration of her function?

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1. Revision total knee arthroplasty with placement of a hinge constrained device
2. Patellar tendon repair with nonabsorbable suture and patellar resurfacing
3. Hinged knee brace with drop lock design to restore stability during ambulation
4. Extensor mechanism reconstruction using synthetic mesh or allograft
CORRECT ANSWER: D
DISCUSSION:
The patient has an extensor mechanism disruption with patellar tendon rupture. This injury is treated with extensor mechanism reconstruction in the setting of previous total knee arthroplasty. There is a reported high failure rate with attempted repair. Revision to hinge knee arthroplasty would provide implant stability but would not restore the extensor mechanism. The patient is relatively young and is working, so reconstruction would offer better long-term function than a drop lock brace, which can be better used in low-functioning patients with this type of injury. Extensor mechanism reconstruction historically has been accomplished with allograft material, but a novel technique using synthetic mesh also has proved successful in treating this difficult problem.
**Question 48** Figures below show the radiographs, and the CT obtained from a 58-year-old woman who underwent cementless left total hip arthroplasty. Nine months after surgery, she continued to have groin pain when actively flexing her hip. She has trouble walking up stairs and getting out of her car.
What is the most likely diagnosis?

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1. Trochanteric bursitis
2. Femoral component loosening
3. Iliopsoas tendonitis
4. Acetabular component loosening
CORRECT ANSWER: C
DISCUSSION:
Groin pain after total hip replacement has a number of possible causes, and an exact diagnosis may remain elusive in some patients. Infection should be ruled out with laboratory studies and, if indicated, diagnostic aspiration of the hip joint. Implant loosening should be evaluated by plain radiograph and bone scan, if indicated. Synovitis resulting from wear debris should be considered in patients with polyethylene liners who experience late-onset symptoms or in any patient with a metal-on-metal bearing. This patient's symptoms are classic for iliopsoas tendonitis. Physical examination usually reveals pain and weakness with resisted hip flexion. A cross-table lateral radiograph and CT show that the anterior edge of the acetabulum protrudes beyond the anterior wall, thereby acting as a source of iliopsoas tendon irritation. In such cases, acetabular component revision and repositioning are indicated. Fluoroscope-guided iliopsoas cortisone injection can help to establish the diagnosis and relieve groin pain. If the acetabular component is well positioned, then iliopsoas tenotomy should be considered.
**Question 49** A 72-year-old woman is scheduled to undergo right total hip arthroplasty. Her preoperative radiograph is shown in Figure below. To avoid increasing this patient’s combined offset while maintaining her leg length, what is the most appropriate surgical plan?

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1. Lateralize the acetabular component, use a low offset femoral component, and make a shorter neck cut
2. Medialize the acetabular component, use a low offset femoral component, and make a longer neck cut
3. Lateralize the acetabular component, use a high offset femoral component, and make a shorter neck cut
4. Medialize the acetabular component, use a high offset femoral component, and make a longer neck cut
CORRECT ANSWER: B
DISCUSSION:
The management of patients with proximal femoral deformity can be difficult. Appropriate implant selection and preoperative templating are critical. In this patient, it would be difficult to avoid increasing the combined offset by too much, which could contribute to the overtensioning of the soft tissues and trochanteric pain. By medializing the acetabular component (decreasing the combined offset), using a low offset femoral component or a cemented component placed more valgus (decreasing the combined offset), and making a longer neck cut (to avoid shortening of the lower extremity), restoration of the patient’s native offset and leg length can be achieved.
**Question 50** Figures below demonstrate the radiographs obtained from a 56-year-old man with a 3-year history of right groin pain. A comprehensive nonsurgical program has failed, and the patient would like to proceed with total hip arthroplasty. He is seen by a pain management specialist and is currently taking 40 mg of sustained-release morphine twice daily with oxycodone 10 mg 2 to 3 times a day for severe pain. What is the recommended course of action regarding his chronic narcotic use?

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D. Stop all his opioids 5 days before surgery, and place the patient on a morphine pain control pump postoperatively with a basal rate.
1. Increase his current opioid medication regimen prior to and after surgery as needed to control his pain.
2. Decrease his preoperative opioid use, and work with his pain management physician to decrease his postoperative opioid requirement.
3. Avoid using narcotics in the perioperative period to prevent overdose, and use acetaminophen only for pain control.
CORRECT ANSWER: B
DISCUSSION:
Chronic opioid consumption prior to total joint arthroplasty has been associated with increased pain after surgery, increased opioid requirements, a slower recovery and longer hospital stay, and higher 90-day postoperative complications compared with patients not on chronic opioids preoperatively. Based on this information, Nguyen and associates performed a study in three patient groups that included 1) chronic opioid users who underwent no preoperative intervention, 2) chronic opioid users who were weaned down to 50% of their prior opioid regimen, and 3) patients who were not chronic opioid users. The authors found that the reduction of preoperative opioid use improved postoperative function, pain, and recovery and that the weaned group performed more like the opioid naive group than the chronic opioid user
group. Increasing opioid use prior to surgery in this patient would make it more difficult to control pain after surgery. Stopping all of his opioids just prior to surgery would place the patient at substantial risk for opioid withdrawal and is not recommended. Avoiding the use of all narcotics and using only acetaminophen postoperatively is very unlikely to provide appropriate pain relief in a chronic opioid user. The recommendation based on the provided literature is to decrease the patient's narcotic use prior to surgery.
**Question 51** A 72-year-old patient fell 3 weeks after undergoing a total hip arthroplasty using cementless fixation of the femoral component. She sustained a comminuted Vancouver type B-2 fracture with displacement of the calcar fragment. What is the best treatment option?
1. Revision using a proximal femoral replacement prosthesis
2. Revision using a diaphyseal engaging femoral prosthesis along with cerclage fixation
3. Open reduction internal fixation using a locking plate with strut graft
4. Protected weight bearing with abduction bracing
CORRECT ANSWER: B
DISCUSSION:
The patient has an acute postoperative fracture of the proximal femur with subsidence. It is also common that the stem retroverts relative to the femur. It is most often seen in proximally porous coated stems within 90 days of surgery, one paper found it to occur 0.7% of the time in modern implants. There is always a debate whether this is a missed intraoperative fracture, or a new fracture that has resulted from an event of increased hoop stresses. Removal of the primary stem, placement of a diaphyseal engaging stem (most frequently a tapered-fluted stem), and cabling of the fracture is the most successful treatment.
**Question 52** What is the most important preoperative factor predicting conversion to total hip arthroplasty after arthroscopic surgery of the hip?
1. Age over 60 years
2. Morbid obesity
3. Diagnosis of osteoarthritis
4. Tobacco use
CORRECT ANSWER: B
DISCUSSION:
The authors cited in the

Scientific References

examined large databases to determine the risk factors for conversion to total hip arthroplasty after arthroscopic surgery of the hip. In the study by Kester and associates, obesity had an odds ratio (OR) of 5.6 for conversion to hip arthroplasty, whereas age over 60 years had an OR of 3.4, osteoarthritis had an OR of 2.4, and tobacco use had an OR of 1.9.
**Question 53** A 70-year-old woman with a body mass index (BMI) of 34 and a history of hypercholesterolemia has elected to undergo total hip arthroplasty. Her son recently learned he has factor V Leiden following an episode of pulmonary embolism. What are this patient's risk factors for thromboembolic disease?
1. Type of surgery, age, and BMI
2. Type of surgery, hypercholesterolemia, and age
1. Age, BMI, and hypercholesterolemia
2. BMI, type of surgery, and hypercholesterolemia
CORRECT ANSWER: A
DISCUSSION:
Risk stratification is one of the most critical clinical evaluations to undertake before performing total joint arthroplasty. Many factors have been identified that increase the risk for venous thromboembolism (VTE) The major factors include previous VTE, obesity, type of surgery (such as total joint arthroplasty), hypercoagulable states, myocardial infarction, congestive heart failure, family history of VTE, and hormone replacement therapy. Hypercholesterolemia is not a risk factor for thromboembolic disease.
**Question 54** Figures below depict the radiographs obtained from a 76-year-old woman who comes to the emergency department after experiencing a fall. She is an unassisted community ambulator with a history of right hip pain. What is the most appropriate surgical treatment for this fracture?

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1. Cemented unipolar hemiarthroplasty
2. Cemented bipolar hemiarthroplasty
3. Total hip replacement
4. Open reduction and internal fixation
CORRECT ANSWER: C
DISCUSSION:
This patient has pre-existing right hip osteoarthritis. The most correct option for the treatment of this active patient is a right total hip arthroplasty. Hemiarthroplasty would not address the patient's pain from osteoarthritis, and open reduction and internal fixation would not fix the femoral head issue or the osteoarthritis.
**Question 55** Figures below show the clinical photograph and radiograph obtained from a 62-year-old man who has deformity and pain 1 year after primary total hip arthroplasty. What is the reason for the observed deformity?

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1. A Vancouver type B1 fracture
2. Residual leg-length discrepancy
3. Loosening and subsidence of the femoral stem into anteversion
4. Loosening and subsidence of the femoral stem into retroversion
CORRECT ANSWER: D
DISCUSSION:
Figure 1 reveals an external rotation deformity of the right lower extremity. This deformity can have numerous causes, including extra-articular deformity. Figure 2 reveals a loose, subsided femoral component. Femoral stems typically subside into retroversion due to proximal femoral biomechanics, which cause a compensatory external rotation deformity. The combined findings from both images suggest an external rotation deformity most likely related to subsidence into retroversion.
**Question 56** Figures below show the radiographs obtained from an 86-year-old-woman who has had chronic left hip pain for several years. She now uses a walker and a wheelchair for ambulation. She is medically healthy. What is the most appropriate surgical intervention?

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1. Cemented left total hip arthroplasty (THA)
2. Cementless left THA with a proximally porous coated femoral stem
3. Hybrid left THA
4. Cementless left THA with a diaphyseal engaging conical femoral stem
CORRECT ANSWER: C
DISCUSSION:
This 86-year-old woman has poor bone quality and osteoarthritis of the left hip. Her lateral radiograph confirms Dorr type C bone quality. A hybrid left THA with a cemented femoral stem would be the treatment of choice.
**Question 57** Figure below shows the radiograph obtained from a 76-year-old woman who has sharp pain in her groin, thigh, and buttocks that worsens with activity. She has been dealing with this pain for more than a year but is otherwise healthy. Recently, she has begun to notice night pain. The pain no longer responds to NSAIDs. She would like to be able to dance at her daughter's wedding in 4 months and wonders how best to proceed. What is the best next step?

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1. Radiograph-guided steroid injection followed by total hip arthroplasty 6 weeks later
2. Total hip arthroplasty
3. Physical therapy
4. Referral back to her spine surgeon
CORRECT ANSWER: C
DISCUSSION:
The next best course of action is total hip arthroplasty. The patient is an otherwise healthy woman requesting pain relief and expresses a desire to be dancing in 4 months. She has had more than 6 months of symptoms that are classic hip osteoarthritis symptoms, with pain in the groin and thigh. Severe osteoarthritis is seen in the radiograph as well. NSAIDs are no longer working. Given the objective findings, the subjective reports, and the duration of symptoms, this patient merits surgery. Consideration for steroid injection is reasonable, but given her desire to be dancing in 4 months, an injection would increase her risk of infection if total hip arthroplasty were to be performed within 3 months of the injection.
**Question 58** A 68-year-old woman underwent an uncemented medial/lateral tapered femoral placement during a total hip arthroplasty. The orthopaedic surgeon noticed a nondisplaced vertical fracture in the calcar region of the femoral neck during final implant insertion. What is the most appropriate treatment?
1. Removal of the press-fit implant and cementing of the same femoral stem
2. Removal of the uncemented femoral component and placement of a revision modular taper-fluted femoral stem
3. Removal of the implant, placement of a cerclage wire around the femoral neck above the lesser trochanter, and reinsertion of the implant
4. Final seating of the uncemented femoral component without additional measures
CORRECT ANSWER: C
DISCUSSION:
The recognized treatment for a proximal periprosthetic fracture is to first identify the extent and then optimize the correction of the fracture. Several studies indicate that proximal cerclage wiring is adequate to create "barrel hoop" stability of the proximal femur. Braided cables offer superior stability compared with twisted wires or Luque wires. Finally, the appropriate postoperative treatment is protected
weight bearing for 6 weeks, with periodic radiographs taken at 2-week intervals. Other options such as cementing the femoral stem and using a revision arthroplasty device are indicated for unstable fractures.
**Question 59** Injury to the popliteal artery during total knee arthroplasty (TKA) is most likely to occur when placing a sharp retractor
1. directly posterior to the posterior cruciate ligament (PCL).
2. posteromedial to the PCL.
3. posterolateral to the PCL.
4. in the posteromedial corner of the knee.
CORRECT ANSWER: C
DISCUSSION:
Vascular complications during TKA are rare but do occur. Traditionally, it was taught that the popliteal artery was situated posterior to the PCL; however, more recent anatomic dissections have demonstrated that this artery is usually located posterolateral to the PCL.
**Question 60** A 70-year-old woman has a 3-year history of gradually increasing diffuse and global right knee pain. Her main issues are difficulty with stairs, stiffness with prolonged sitting, and swelling. She has taken NSAIDs and has received intra-articular steroid injections, all with decreasing efficacy. Her right knee examination reveals a range of motion of 15° to 80° with a fixed deformity to varus and valgus stress. Her symptoms are no longer manageable nonsurgically. Radiographs reveal a 30-degree mechanical axis deformity. When using the measured resection technique during total knee arthroplasty (TKA), the best way to avoid femoral malrotation is to reference the
1. anteroposterior axis.
2. tibial intramedullary axis.
3. posterior condylar axis.
4. femoral intramedullary axis.
CORRECT ANSWER: A
DISCUSSION:
In the setting of valgus deformities, TKA poses different challenges than those encountered when varus deformities are present. Most valgus alignment is attributable to a deformity of the distal femur rather than of the proximal tibia, as seen in varus knees. One of the major anatomical differences is a hypoplastic lateral femoral condyle which, when not recognized and used as a rotational reference point, can lead to internal rotation of the femoral component. This malrotation in turn leads to patellofemoral maltracking or instability, which is a common complication associated with primary TKA.
**Question 61** A 70-year-old woman has a 3-year history of gradually increasing diffuse and global right knee pain. Her main issues are difficulty with stairs, stiffness with prolonged sitting, and swelling. She has taken NSAIDs and has received intra-articular steroid injections, all with decreasing efficacy. Her right knee examination reveals a range of motion of 15° to 80° with a fixed deformity to varus and valgus stress. Her symptoms are no longer manageable nonsurgically. Radiographs reveal a 30-degree mechanical axis deformity. The deformity shown in Figure below is predominantly associated with

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1. a hypoplastic lateral femoral condyle.
2. a contracted medial collateral ligament.
3. an excessive proximal tibial slope.
4. trochlear dysplasia.
CORRECT ANSWER: A
DISCUSSION:
In the setting of valgus deformities, TKA poses different challenges than those encountered when varus deformities are present. Most valgus alignment is attributable to a deformity of the distal femur rather than of the proximal tibia, as seen in varus knees. One of the major anatomical differences is a hypoplastic lateral femoral condyle which, when not recognized and used as a rotational reference point, can lead to internal rotation of the femoral component. This malrotation in turn leads to patellofemoral maltracking or instability, which is a common complication associated with primary TKA.
**Question 62** Figures below show the radiographs, and the MRIs obtained from a 32-year-old man with worsening left knee pain. A 3-foot hip-to-ankle radiograph shows a 13-degree varus knee deformity. The patient sustained a major left knee injury 5 years ago and a confirmed complete anterior cruciate ligament (ACL) tear. He managed this injury nonsurgically with a functional brace but experienced worsening pain. He was seen by an orthopaedic surgeon 18 months ago, and a medial meniscus tear was diagnosed; the tear was treated with an arthroscopic partial medial meniscectomy. Since then, his knee has been giving way more often, and he no longer feels safe working on a pitched roof. The patient received 6 months of formal physical therapy and was fitted for a new functional ACL brace, but he still has pain and instability. He believes he has exhausted his nonsurgical options and would like to undergo surgery. What is the most appropriate treatment at this time?

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1. ACL reconstruction and subsequent proximal tibial osteotomy
2. ACL reconstruction alone
3. Distal femoral osteotomy with simultaneous ACL reconstruction
4. Proximal tibial osteotomy with subsequent ACL reconstruction
CORRECT ANSWER: D
DISCUSSION:
Proximal tibial osteotomy is the most appropriate intervention to correct varus malalignment and to reduce stress on the ACL. In some cases, proximal tibial osteotomy alone may address both pain and instability, but if instability persists, particularly in the setting in which instability can be dangerous, subsequent ACL reconstruction can further stabilize the knee with less stress on the graft after the correction of malalignment. Varus alignment places increased stress on the native or reconstructed ACL. ACL reconstruction should be performed only at the same time as or following proximal tibial osteotomy to correct alignment in the setting of varus malalignment. It is not appropriate to perform ACL reconstruction prior to proximal tibial osteotomy in this setting. Distal femoral osteotomy is not indicated to correct varus malalignment. Varus alignment places increased stress on the native or reconstructed ACL, and ACL reconstruction alone is not indicated for this patient.
**Question 63** When balancing gaps in the coronal plane, what structure preferentially impacts the flexion space more than the extension space?
1. Iliotibial band
2. Popliteus tendon
3. Lateral collateral ligament
4. Lateral head of the gastrocnemius
CORRECT ANSWER: B
DISCUSSION:
In the setting of valgus deformities, TKA poses different challenges than those encountered when varus deformities are present. Most valgus alignment is attributable to a deformity of the distal femur rather than of the proximal tibia, as seen in varus knees. One of the major anatomical differences is a hypoplastic lateral femoral condyle which, when not recognized and used as a rotational reference point,
can lead to internal rotation of the femoral component. This malrotation in turn leads to patellofemoral maltracking or instability, which is a common complication associated with primary TKA.
**Question 64**
A 45-year-old woman has severe anterior knee pain. Her radiographs indicate end-stage patellofemoral
compartment osteoarthritis. The tibiofemoral compartments are preserved. Extensive nonsurgical treatment has failed to provide relief, and she is offered patellofemoral arthroplasty (PFA). What is the most common long-term mode of failure for PFA using an implant with an onlay prosthesis design?
1. Infection
2. Patellar instability
3. Aseptic loosening
4. Progression of tibiofemoral arthritis
CORRECT ANSWER: D
DISCUSSION:
Contemporary onlay-design trochlear prostheses in PFA replace the entire anterior trochlear surface. Previous inlay designs were inset within the native trochlea and carried a higher risk of catching and patellar instability, particularly in patients with trochlear dysplasia; they also generally have higher failure rates. The current most common mode of failure is progression of arthritis throughout the knee, in some series as high as 25% at 15 years. Aseptic loosening, particularly of cemented implants, is less common. Infection is an uncommon long-term complication. Patients considering PFA should be advised of the risk of arthritis progression. Many authors routinely obtain a preoperative MRI to assess the status of the tibiofemoral compartments.
**Question 65** Figures below show the radiographs obtained from a 79-year-old woman who has been experiencing increasing tibial pain 10 years after undergoing revision total knee arthroplasty. No evidence of infection is seen. What is the most appropriate treatment?

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1. Retain the components, and implant a tibial strut allograft.
2. Revise the tibial component with a metaphyseal cone and metaphyseal uncemented stem.
3. Revise the tibial component with a metaphyseal cone and a press-fit diaphyseal-engaging stem.
4. Revise the tibial component with a long cemented diaphyseal-engaging stem.
CORRECT ANSWER: C
DISCUSSION:
Stems are available for cemented and press-fit implantation. To be effective, press-fit stems should engage the diaphysis, as shown in Figures 3 and 4. They also assist in obtaining correct limb alignment. Short metaphyseal-engaging stems are associated with failure rates that range between 16% and 29%. Cemented stems may be shorter than press-fit stems, because they do not have to engage the diaphysis. Short, fully cemented stems offer the advantage of metaphyseal fixation. Hybrid stem fixation makes use of the metaphysis for cement fixation with metaphyseal cones or sleeves and diaphyseal-engaging press-fit stems.
**Question 66** A 70-year-old man reports symptomatic medial knee pain that has become progressively worse during the past year. MRI reveals a complex, posterior horn medial meniscus tear with associated medial lateral and patellofemoral cartilage defects. Radiographs reveal medial joint space narrowing and osteophytes in the other compartments. What treatment is most likely to provide long-term, durable relief of symptoms?
1. High tibial osteotomy
2. Total knee replacement
3. Unicondylar knee replacement
4. Arthroscopic partial meniscectomy
CORRECT ANSWER: B
DISCUSSION:
Total knee replacement is a well-established surgery for diffuse, symptomatic osteoarthritis of the knee joint, and its efficacy has been shown in many studies. According to the 2008 AAOS Clinical Practice Guideline, Treatment of Osteoarthritis of the Knee, arthroscopy in the setting of existing osteoarthritis is efficacious for relieving the signs and symptoms of a torn meniscus but not for osteoarthritis. Likewise, in young and active patients, clinical outcomes show improvement after realignment osteotomy for single-compartment osteoarthritis. Unicondylar knee replacement is not indicated for tricompartmental disease of the knee.
**Question 67** A 58-year-old man with insulin-dependent diabetes mellitus underwent primary total knee arthroplasty (TKA). A full-thickness skin slough measuring 3 cm by 4 cm developed, with postsurgical exposure of the patellar tendon. No change is observed in the appearance of the wound after 2 weeks of wet-to-dry dressing changes. What is the best next treatment step for the soft-tissue defect?
1. Continued dressing changes
2. Split-thickness skin graft
3. Full-thickness skin graft
4. Local rotational flap
CORRECT ANSWER: D
DISCUSSION:
If wound healing does not occur and deep soft tissues such as the patellar tendon are exposed following TKA, local rotational flap is the procedure of choice. The procedure should be performed relatively early after the recognition of a soft-tissue wound-healing problem. In the setting of TKA, the gastrocnemius muscle is an excellent source of flaps for wound coverage of the proximal tibia.
**Question 68**
A 77-year-old man who underwent right total knee replacement surgery 2 and a half years ago has had knee pain since surgery. The pain is diffuse, constant, and made worse with activity. He notes warmth and swelling in his knee. Examination shows a well-healed incision, no erythema, moderate warmth, synovitis, and an effusion. The knee is stable, and has an arc of flexion between 3° and 120°. Radiographs show well-fixed and well-aligned implants. What is the most appropriate initial treatment?
1. Knee aspiration for culture
2. CT of the knee to assess implant rotation
3. Indium-111 leukocyte/technetium-99m sulfur colloid scan of the knee
4. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) laboratory studies
CORRECT ANSWER: D
DISCUSSION:
This patient's history and physical findings are concerning for deep infection. Inflammatory markers, including ESR and CRP, should be obtained first. If the levels are elevated, knee aspiration should be performed for the synovial cell count and culture. A bone scan is not indicated in an initial investigation for deep infection; it is rarely helpful and is not cost effective. CT to assess implant rotation is an appropriate investigation for knee pain when the clinical scenario is not suspicious for a deep infection and when infection has been excluded.
**Question 69** A 61-year-old man with a body mass index of 31 had a 6-month gradual onset of right medial knee pain. Examination revealed a small effusion, stable ligaments, a normally tracking patella, and mild medial joint line tenderness. Standing radiographs show mild medial joint space narrowing. Effective treatment at this stage of early medial compartmental osteoarthritis includes
1. glucosamine 1,500 mg/day and chondroitin sulfate 800 mg/day.
2. weight loss through dietary management and low-impact aerobic exercises.
3. arthroscopic debridement and lavage.
4. a valgus-directing brace.
CORRECT ANSWER: B
DISCUSSION:
According to the 2008 AAOS Clinical Practice Guideline, Treatment of Osteoarthritis of the Knee (Nonarthroplasty), level 1 evidence confirms that weight loss and exercise benefit patients with knee osteoarthritis. The other responses have either inclusive evidence (a valgus-directing brace) or no evidence to support their use (glucosamine 1,500 mg/day and chondroitin sulfate 800 mg/day as well as arthroscopic debridement and lavage).
**Question 70** In patients with Crowe types III and IV developmental dysplasia of the hip with high hip centers, acetabular reconstruction often requires lowering the acetabular component into the native acetabulum. In doing so, considerable risk for limb lengthening beyond 4 cm exists, making the hip difficult to reduce and raising the risk for nerve injury. Which technique is used to overcome this problem?
1. Subtrochanteric osteotomy with femoral shortening
2. An offset femoral component
3. A lateralized liner
4. Extended trochanteric osteotomy
CORRECT ANSWER: A
DISCUSSION:
When substantial lengthening of a dysplastic hip will occur because a high dislocation is relocated into a considerably lower acetabulum, a femoral shortening may be necessary to reduce the hip and avoid a stretch injury to the sciatic nerve. No other choice specifically addresses the need for femoral shortening, and high offset stems and lateralized liners may exacerbate the problem if used alone and without femoral shortening.
**Question 71**
What factor is considered one of the early changes in osteoarthritic cartilage?
1. Decreased water content
2. Increased proteoglycan content
3. Decreased loading of the solid matrix
4. Increased cartilage tissue permeability
CORRECT ANSWER: D
DISCUSSION:
The normal regulation of a cartilage surface is a delicate balance of degradation and synthesis. When this normal regulation of the cartilage is disturbed, a proinflammatory state tips the cellular pathway in the direction of degradation. The proinflammatory state upregulates the production of cytokines and proteolytic enzymes, specifically matrix metalloproteinases. These enzymes attack the proteoglycan content of the cartilage, leading to an overall reduction in the proteoglycan content. This reduction in content leads to increased permeability of the cartilage substrate. With increased permeability, water is able to move into the cartilage itself, thereby increasing the overall water content within the cartilage in an arthritic state. Finally, because of the increased permeability and increased water content, the overall load or pressure placed on the underlying solid matrix is increased. Increased water content, decreased proteoglycan content, and an increased load on the solid matrix are typical of an osteoarthritic process within normal cartilage. Therefore, the only correct option is that the cartilage has an increased amount of permeability in osteoarthritis.
**Question 72** A 47-year-old obese man with a body mass index of 42 comes into the office with left knee pain 1 year after undergoing an uncomplicated left medial unicompartmental knee arthroplasty (UKA). Radiographs show a loose tibial component in varus. What is the most appropriate next step to treat this failed construct?
1. Aspiration of joint fluid to obtain a cell count
2. Revision of the UKA using primary total knee arthroplasty (TKA) components
3. Revision of the UKA using a revision TKA with augments
4. Procurement of the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level
CORRECT ANSWER: D
DISCUSSION:
This patient likely is experiencing failure of the UKA secondary to poor patient selection. In this young, heavy man, the component likely loosened due to the ongoing varus alignment of the knee and his elevated
weight. Despite this likely scenario, the next step is determining whether an infection is the cause of his pain. Prior to obtaining an aspiration, the surgeon can order ESR and CRP studies to determine whether aspiration is warranted. If the laboratory studies are unremarkable, the surgeon likely can forgo the aspiration and proceed to a revision TKA with possible augments on standby.
**Question 73** Figure below shows the standing AP radiograph obtained from a 55-year-old man who has a 5-year history of daily left knee medial joint line pain with weight-bearing activities. He denies night pain or symptoms of instability. On examination, his range of motion is 0° to 140°. He has a mild, fully correctable varus deformity and a negative Lachman test result. Nonsurgical treatment has failed. What is the UKA survivorship for a 55-year-old patient, compared with the survivorship for total knee arthroplasty?

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1. Equal at 10 years
2. Lower at 10 years
3. Higher at 10 years
4. Not known when using a mobile-bearing UKA
CORRECT ANSWER: B
DISCUSSION:
A patient with medial compartment arthritis and a correctable varus deformity with no clinical or examination findings of knee instability most likely has an intact anterior cruciate ligament (ACL). The pattern of medial compartment osteoarthritis most commonly associated with an intact ACL is that of anteromedial osteoarthritis. An incompetent ACL is commonly associated with a fixed varus deformity and radiographic signs of posteromedial wear. An incompetent ACL is a relative contraindication to a mobile-bearing UKA. When evaluating patients for a mobile-bearing UKA, a stress radiograph aids the orthopaedic surgeon in determining the correction of the varus deformity and assessing the lateral compartment. An inability to fully correct the deformity or narrowing of the lateral compartment with valgus stress should influence the surgeon against UKA. Joint registries across the world have shown decreased survivorship associated with TKA and UKA in men compared with other age groups, but survivorship is lower for UKA than for TKA. No studies to date have shown any differences in survivorship between fixed-bearing and mobile-bearing UKAs. The complication that is unique to mobile-bearing UKA is bearing spinout, which occurs in less than 1% of mobile-bearing UKA procedures. In vivo and in vitro polyethylene wear in mobile-bearing UKA are low. Arthritis may progress faster in patients with mobile-bearing UKAs than in those with fixed-bearing UKAs.
**Question 74** A 57-year-old woman experiences pain 1 year after total knee arthroplasty (TKA). She reports sharp anterior pain and a painful catching sensation that is aggravated by rising from a chair or climbing stairs. Physical examination reveals a mild effusion and a range of motion of 2° to 130°, with patellar crepitus.
The symptoms are reproduced by resisted knee extension. Radiographs show a well-aligned posterior-stabilized TKA without evidence of component loosening. What is the most likely cause of this patient's pain?
1. Patellar clunk syndrome
2. Flexion gap instability
3. Polyethylene wear
4. Femoral component malrotation
CORRECT ANSWER: A
DISCUSSION:
Patellar clunk syndrome is caused by the development of a fibrous nodule on the posterior aspect of the quadriceps tendon at its insertion into the patella. It causes a painful catching sensation when the extensor mechanism traverses over the trochlear notch as the knee extends from 45° of flexion to 30° from full extension. It characteristically occurs in posterior stabilized total knee arthroplasties and appears to be related to femoral component design. The syndrome can usually be prevented by excising the residual synovial fold just proximal to the patella. Flexion gap instability can also cause a painful total knee arthroplasty but is less common in posterior stabilized implants. Femoral component malrotation can cause pain attributable to a flexion gap imbalance or patellar tracking problems. Polyethylene wear would be unlikely after just 1 year. Patellar clunk syndrome can usually be addressed successfully with arthroscopic synovectomy. Recurrence is uncommon. Physical therapy may help to strengthen the quadriceps following synovectomy but would not resolve the clunk syndrome symptoms. Femoral or tibial insert revision is not indicated if patellar clunk syndrome is the only problem resulting in a painful
total knee arthroplasty.
**Question 75** In total knee arthroplasty, in vitro testing has shown that cross-linking can diminish the rate of polyethylene wear by 30% to 80%. What other change in material properties is possible when polyethylene is highly cross-linked?
1. Increased ductility
2. Increased wettability
3. Diminished fatigue strength
4. Decreased resistance to abrasive wear
CORRECT ANSWER: C
DISCUSSION:
The most important concern regarding highly cross-linked polyethylene relates to decreased mechanical properties. Cross-linking results in reduced ductility, tensile strength, and fatigue crack propagation resistance. These problems have not been shown to cause implant failure in the most recent clinical trials, but they remain the most important mechanical issues associated with current material processing methods.
**Question 76** A 70-year-old woman who underwent total knee replacement 18 months ago has had 3 weeks of moderate drainage from a previously healed wound. What is the most appropriate treatment?
A. Vacuum-assisted wound closure dressing
1. Intravenous antibiotics for 6 weeks, followed by long-term oral antibiotic administration
2. Irrigation and debridement, followed by polyethylene exchange
3. Two-stage debridement and reconstruction
CORRECT ANSWER: D
DISCUSSION:
This situation represents a definitively and chronically infected knee replacement. Antibiotic therapy alone might suppress the infection but would not eradicate it. Debridement and polyethylene exchange would be appropriate treatment for an early postoperative infection. The treatment of choice is to perform a two-stage debridement and reconstruction. Although not among the listed choices, an aspiration or culture could be done presurgically and might help clinicians identify the best antibiotics to treat the condition. Antibiotic selection would not affect the need for the two-stage reconstruction, however.
**Question 77** During a posterior cruciate ligament (PCL)-retaining total knee arthroplasty, a critical principle to remember is to
1. accurately tension the PCL.
2. use bony resection to adjust the joint line.
3. maintain a small amount of residual deformity.
4. use intraoperative fluoroscopy to ensure femoral roll back.
CORRECT ANSWER: A
DISCUSSION:
Maintenance of the joint line and accurately tensioning the PCL are critical in the proper execution of a PCL-retaining total knee arthroplasty. Appropriate tension helps ensure femoral rollback and avoid stiffness or instability. Raising the joint line to help ensure full extension should be avoided in cruciate-retaining knees, because doing so creates an unfavorable kinematic environment. The three important principles of surgical technique needed to maintain appropriate tensioning of the PCL include 1) choosing the proper femur size to reproduce the native femoral anterior/posterior dimension, 2) reproducing the joint line by resecting as much tibia from the healthy side as will be replaced by the smallest thickness of the tibial component and, 3) ensuring that full extension is achieved by soft-tissue releases and not by taking additional distal femur, as may be done in a posterior stabilized approach. Another important principle is to re-create the natural degree of the patient’s posterior tibial slope to avoid tightness in flexion.
**Question 78** Figures below depict the AP and lateral radiographs obtained from a 64-year-old man with long-standing right knee osteoarthritis and pain that is unresponsive to nonsurgical treatment. The patient undergoes navigated cruciate-retaining right total knee arthroplasty. After surgery, this patient continues to experience pain and swelling of the knee with recurrent effusions. He returns to the office reporting continued pain 2 years after surgery. He describes instability, particularly when descending stairs. On examination, range of motion of 0° to 120° is observed, with no extensor lag. Slope of the tibial component is 7°. The knee is stable to varus and valgus stress in extension, but flexion instability is present in both the anterior-posterior direction and the varus-valgus direction. Bracing leads to a slight decrease in symptoms but is not well tolerated. Isokinetic testing demonstrates decreased knee extension velocity at
mid push. Radiographs demonstrate well-aligned and fixed knee implants. An infection work-up is negative. What is the most appropriate surgical intervention at this time?

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1. Tibial polyethylene exchange
2. Revision of the femoral and tibial components and conversion to a posterior stabilized insert
3. Revision of the femoral and tibial components to a constrained rotating hinge prosthesis
4. Isolated femoral component revision and upsizing of the femoral implant with a new posterior cruciate ligament (PCL)-retaining polyethylene insert
CORRECT ANSWER: B
DISCUSSION:
The patient’s symptoms at follow-up—pain, swelling, and difficulty descending stairs—suggest knee flexion instability. Considering his history, an incompetent PCL must be considered. Revision of the knee to a posterior stabilized or nonlinked constrained condylar implant (depending on the condition of the ligaments) likely is needed to address his symptoms. The difference in extension stability and flexion stability makes polyethylene exchange a poor option. A constrained rotating hinge design is not necessary. Repeat use of a PCL-retaining insert is not recommended. Tibial and femoral revision both are required. Correction of excessive slope will be attained with tibial revision, femoral component revision is required to convert to a PCL-substituting design. There is also an opportunity to increase posterior condylar offset if needed.
**Question 79** Figure below shows the standing AP radiograph obtained from a 55-year-old man who has a 5-year history of daily left knee medial joint line pain with weight-bearing activities. He denies night pain or symptoms of instability. On examination, his range of motion is 0° to 140°. He has a mild, fully correctable varus deformity and a negative Lachman test result. Nonsurgical treatment has failed. Unicompartmental knee arthroplasty (UKA) is discussed with the patient. The most appropriate next radiographic evaluation should be

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1. MRI of the left knee to evaluate the lateral compartment.
2. a CT arthrogram to evaluate the status of the medial and lateral meniscus.
3. a stress radiograph to evaluate correction of the varus deformity.
4. a sunrise view to determine the status of the patellofemoral joint.
CORRECT ANSWER: C
DISCUSSION:
A patient with medial compartment arthritis and a correctable varus deformity with no clinical or examination findings of knee instability most likely has an intact anterior cruciate ligament (ACL). The pattern of medial compartment osteoarthritis most commonly associated with an intact ACL is that of anteromedial osteoarthritis. An incompetent ACL is commonly associated with a fixed varus deformity and radiographic signs of posteromedial wear. An incompetent ACL is a relative contraindication to a mobile-bearing UKA. When evaluating patients for a mobile-bearing UKA, a stress radiograph aids the orthopaedic surgeon in determining the correction of the varus deformity and assessing the lateral compartment. An inability to fully correct the deformity or narrowing of the lateral compartment with valgus stress should influence the surgeon against UKA. Joint registries across the world have shown decreased survivorship associated with TKA and UKA in men compared with other age groups, but survivorship is lower for UKA than for TKA. No studies to date have shown any differences in survivorship between fixed-bearing and mobile-bearing UKAs. The complication that is unique to mobile-bearing UKA is bearing spinout, which occurs in less than 1% of mobile-bearing UKA procedures. In vivo and in vitro polyethylene wear in mobile-bearing UKA are low. Arthritis may progress faster in patients with mobile-bearing UKAs than in those with fixed-bearing UKAs.
**Question 80** Compared with retention of the native patella in primary total knee arthroplasty, routine patellar resurfacing is associated with
1. no patellar complications.
2. an increased occurrence of anterior knee pain.
3. a reduced patellar fracture rate.
4. a reduced risk for revision surgery.
CORRECT ANSWER: D
DISCUSSION:
Despite concerns regarding fracture, osteonecrosis, and patellar clunk, the routine retention of the native patella during primary total knee replacement is associated with a 20% to 30% increased revision risk in
large joint registries. In addition, the retention of the native patella results in a 5.7% revision surgery rate in patients with anterior knee pain.
**Question 81** A surgeon prepares a medial gastrocnemius rotational flap to cover a medial proximal tibia defect at the time of revision knee replacement surgery. To optimize coverage, the surgeon must optimally mobilize which artery?
1. Profunda femoris
2. Middle genicular
3. Medial sural
4. Inferior medial genicular
CORRECT ANSWER: C
DISCUSSION:
The medial sural arteries vascularize the gastrocnemius, plantaris, and soleus muscles proximally. These arteries arise from the popliteal artery. If this artery is not adequately mobilized, a gastrocnemius soleus flap can be devascularized.
**Question 82** Figures below represent the radiographs obtained from a 37-year-old man with severe right knee pain. He has a history of prior tibial osteotomy for adolescent tibia vara but notes residual bowing of his legs. On examination, he is 5'8" tall and weighs 322 pounds. He has a waddling gait with a bilateral varus thrust and 20° varus deformity of both legs. His right knee range of motion is 0° to 120° with a fixed varus deformity. What is the best next step?

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1. Total knee arthroplasty with standard components
2. Correction of tibial deformity with osteotomy and nonsurgical management of the osteoarthritis
3. Arthrodesis with a long antegrade nail
4. Total knee arthroplasty with a constrained device
CORRECT ANSWER: D
DISCUSSION:
This patient has severe, uncorrectable varus deformity and pain from end-stage osteoarthritis secondary to prior adolescent tibia vara. Although he is young to consider arthroplasty, this option is likely to give him the most functional limb, compared with arthrodesis with a long antegrade nail. During arthroplasty surgery, his knee will likely require extensive medial release to achieve anatomic limb alignment. Standard components in total knee arthroplasty likely would result in lateral instability, so this option is
not the best answer. The best choice is total knee arthroplasty with a constrained device, which adds constraint to the knee to provide balance.
**Question 83** An 85-year-old obese woman has left knee pain. She had surgery 5 years ago for a patellar nonunion after total knee arthroplasty that was complicated by infection, which was treated with implant removal and patellectomy. She has not been ambulatory since then. She states she is no longer on antibiotics. She has moderate pain, but her primary problem is instability of the knee. She has a 40° extensor lag. Darkening of the skin is present distal to the incision consistent with venous stasis changes. The erythrocyte sedimentation rate is 12 mm/h (reference range 0 to 20 mm/h) and her C-reactive protein level is 1.0 mg/L (reference range 0.08 to 3.1 mg/L). Left knee aspiration shows a white blood cell count of 800 and 20% neutrophils. What is the best next step?
1. Revision total knee arthroplasty with primary quadriceps tendon repair
2. Hinged knee arthroplasty with full extensor mechanism allograft
3. Arthrotomy with debridement and antegrade knee arthrodesis nailing
4. Two-stage revision knee arthroplasty and quadriceps repair with Achilles allograft
CORRECT ANSWER: C
DISCUSSION:
This patient is elderly, obese, and nonambulatory and has a chronic quadriceps tendon rupture after infected total knee arthroplasty. Her potential for ambulation after revision total knee arthroplasty is very low. Primary repair of the tendon is unlikely to be successful, even with augmentation, so revision total knee arthroplasty with primary quadriceps tendon repair and two-stage revision knee arthroplasty and quadricep repair with Achilles allograft are not the best management techniques. Extensor mechanism allograft could be done but would have a high failure rate in a patient of this size. No sign of infection is seen, based on laboratory studies, so a two-stage procedure is not necessary. The best management although not optimal, would be treatment in a drop-lock brace. Arthrodesis is also an option, but would have a high complication rate, and in a patient that is nonambulatory, a fused knee would be increasingly difficult with activities of daily living and mobility.
**Question 84** Figures below depict the radiographs obtained from a 53-year-old man who has had swelling in his right knee for 2 years, with minimal pain. He did not note an injury to the knee but has been unable to ambulate without crutches during this period. His past history is unremarkable, and he denies a history of diabetes or back problems. The social history reveals that he emigrated from China, and he works at a desk job. Physical examination shows a healthy man in no acute distress. Range of motion of the right knee is 5° to 120° actively and 0° to 120° passively, without pain. Sensation is decreased on the bottom of both feet, but otherwise the neurologic examination is unremarkable. Laboratory testing reveals a positive rapid plasma reagin (RPR) test. What is the best next step?

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1. Open reduction and internal fixation
2. Hinged total knee arthroplasty
3. Arthrodesis using an intramedullary nail
4. Irrigation and debridement with spacer placement
CORRECT ANSWER: B
DISCUSSION:
This patient has a neuropathic knee caused by neurosyphilis, as shown by the joint destruction on the radiographs, with a lack of pain and a positive RPR test. He has a low-demand job and would be best treated with a hinged knee arthroplasty to provide stability for his knee.
**Question 85** At the time of revision knee arthroplasty, a surgeon performs a rectus snip to gain exposure to the knee. When compared with a standard parapatellar approach, what is the expected outcome?
1. Improvement in range of motion
2. Reduction in range of motion
3. Increase in extensor mechanism lag
4. No differences in motion and strength
CORRECT ANSWER: D
DISCUSSION:
Rectus snip during total knee arthroplasty has no effect on motion or strength at long-term follow-up. It has not been associated with extensor mechanism lag.
**Question 86** Hip pain of 1-month duration has developed in a 72-year-old man with a previous total hip arthroplasty. He underwent dental work 6 weeks ago. Aspiration shows a white blood cell count of more than 6,000 cells/μL (reference range 4,500 to 11,000 cells/μL) and the presence of gram-positive cocci in clusters on Gram stain. The orthopaedic surgeon recommends urgent debridement and irrigation. Fixation of the components is judged to be stable, and the surgeon elects to retain the implants. The patient has a final culture that reveals methicillin-resistant _Staphylococcus aureus_(MRSA). If the attending physician recommends the two-stage protocol, including the use of an antibiotic-cement spacer, what is the most likely prognosis for this patient?
1. Better functional outcome than that associated with infections from sensitive organisms
2. Same functional outcome as that associated with infections from sensitive organisms
1. Same prognosis for eradication of infection as that associated with infections from sensitive organisms
2. Poorer prognosis for eradication of infection than that associated with infection from sensitive organisms
CORRECT ANSWER: D
DISCUSSION:
The patient has a late infection of at least 4 weeks symptomatic duration that most likely is hematogenous in etiology. This infection is not an acute hematogenous infection that can successfully be treated with irrigation and debridement. Retention of the implants with debridement and irrigation alone has been associated with a poor prognosis. In a recent study, the success rate was only 44% in a series of 104 patients at a mean 5.7-year follow-up. In one study of 50 infections attributable to MRSA or methicillin-resistant _Staphylococcus epidermidis_ organisms treated with a two-stage protocol, the failure rate was 21%. Patients who experienced successful infection treatment had lower functional outcome measures using the Western Ontario and McMaster Universities Osteoarthritis Index, the University of California Los Angeles Activity Score, and the 12-item Oxford Knee Score, however.
**Question 87** An 80-year-old African American woman who lives in a large city is scheduled for total hip arthroplasty to address primary osteoarthritis. Part of the presurgical protocol includes nasal swab screening to assess for methicillin-resistant _Staphylococcus aureus_(MRSA) colonization. Which demographic factor places this patient at highest risk for a positive result?
1. Gender
2. Age
3. Race
4. Environment
CORRECT ANSWER: C
DISCUSSION:
Demographic factors are associated with increased risk for MRSA colonization, so it is important to identify vulnerable patients. Female gender and advanced age reduce the risk for colonization, whereas African American race increases this risk. Urban environments do not influence MRSA colonization.
**Question 88** Hip pain of 1-month duration has developed in a 72-year-old man with a previous total hip arthroplasty. He underwent dental work 6 weeks ago. Aspiration shows a white blood cell count of more than 6,000 cells/μL (reference range 4,500 to 11,000 cells/μL) and the presence of gram-positive cocci in clusters on Gram stain. The orthopaedic surgeon recommends urgent debridement and irrigation. Fixation of the components is judged to be stable, and the surgeon elects to retain the implants. What is this patient's prognosis for infection resolution?
1. Good because it is a gram-positive organism
2. Good because it is an acute infection
3. Poor because it is a gram-positive organism
4. Poor because it is a late infection
CORRECT ANSWER: D
DISCUSSION:
The patient has a late infection of at least 4 weeks symptomatic duration that most likely is hematogenous in etiology. This infection is not an acute hematogenous infection that can successfully be treated with irrigation and debridement. Retention of the implants with debridement and irrigation alone has been associated with a poor prognosis. In a recent study, the success rate was only 44% in a series of 104 patients at a mean 5.7-year follow-up. In one study of 50 infections attributable to MRSA or methicillin-resistant _Staphylococcus epidermidis_ organisms treated with a two-stage protocol, the failure rate was 21%. Patients who experienced successful infection treatment had lower functional outcome measures using the Western Ontario and McMaster Universities Osteoarthritis Index, the University of California Los Angeles Activity Score, and the 12-item Oxford Knee Score, however.
**Question 89** A 40-year-old man with a history of Legg-Calve-Perthes disease underwent a right hip resurfacing 3 years ago with no perioperative complications. Hip pain has developed gradually during the last 4 months. Radiographs show no evidence of fixation loosening or any adverse changes at the femoral neck. No periarticular osteolysis is evident. What is the most appropriate management of this condition?
1. Continue to observe with repeat radiographs in 6 months
2. Fluoroscopic-guided iliopsoas tendon cortisone injection
3. Hip aspiration
4. Serum cobalt and chromium levels and metal-reduction MRI scan
CORRECT ANSWER: D
DISCUSSION:
Controversy persists over what exactly is the best approach to managing patients with metal-on-metal (MOM) hip arthroplasties. All patients with painful MOM hip arthroplasties should be examined for fixation loosening, wear/osteolysis, and infection—no differently than patients without MOM hip arthroplasties. It is recommended to obtain serum trace element levels. If the levels are high, cross-sectional imaging should be obtained to determine whether any pseudotumor or tissue necrosis is present around the hip arthroplasty. Hip aspiration should be considered if concern for infection exists. Adverse tissue reaction has been identified to occur around MOM hip arthroplasties. The predominant histologic feature is tissue necrosis with infiltration of lymphocytes and plasma cells.
**Question 90** In patients undergoing elective hip or knee arthroplasty who are not at elevated risk (beyond the risk associated with the surgery) for venous thromboembolism or bleeding, using pharmacologic agents and/or mechanical compressive devices for the prevention of venous thromboembolism was assigned what grade of recommendation by the 2011 AAOS Clinical Practice Guideline, Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty?
1. Strong
2. Moderate
3. Limited
4. Inconclusive
CORRECT ANSWER: B
DISCUSSION:
Using pharmacologic agents and/or mechanical compressive devices for the prevention of venous thromboembolism in patients undergoing elective hip or knee arthroplasty who are not at elevated risk beyond that of the surgery itself for venous thromboembolism or bleeding was given a moderate grade of recommendation in the 2011 AAOS Clinical Practice Guideline referenced above.
**Question 91** A 40-year-old man with a history of Legg-Calve-Perthes disease underwent a right hip resurfacing 3 years ago with no perioperative complications. Hip pain has developed gradually during the last 4 months. Radiographs show no evidence of fixation loosening or any adverse changes at the femoral neck. No periarticular osteolysis is evident. A large intra-articular and intrapelvic pseudotumor has developed. What predominant histological feature(s) is/are present in such a lesion?
1. Polymorphonuclear leukocytes
2. Extracellular metal-wear debris
3. Cement particles within the macrophages
4. Lymphocytes and plasma cells
CORRECT ANSWER: D
DISCUSSION:
Controversy persists over what exactly is the best approach to managing patients with metal-on-metal (MOM) hip arthroplasties. All patients with painful MOM hip arthroplasties should be examined for fixation loosening, wear/osteolysis, and infection—no differently than patients without MOM hip arthroplasties. It is recommended to obtain serum trace element levels. If the levels are high, cross-sectional imaging should be obtained to determine whether any pseudotumor or tissue necrosis is present around the hip arthroplasty. Hip aspiration should be considered if concern for infection exists. Adverse tissue reaction has been identified to occur around MOM hip arthroplasties. The predominant histologic feature is tissue necrosis with infiltration of lymphocytes and plasma cells.
**Question 92** A 57-year-old woman experiences pain 1 year after total knee arthroplasty (TKA). She reports sharp anterior pain and a painful catching sensation that is aggravated by rising from a chair or climbing stairs. Physical examination reveals a mild effusion and a range of motion of 2° to 130°, with patellar crepitus. The symptoms are reproduced by resisted knee extension. Radiographs show a well-aligned posterior-stabilized TKA without evidence of component loosening. What is the recommended treatment for this patient?
1. Physical therapy
2. Arthroscopic synovectomy
3. Tibial insert revision
4. Femoral component revision
CORRECT ANSWER: B
DISCUSSION:
Patellar clunk syndrome is caused by the development of a fibrous nodule on the posterior aspect of the quadriceps tendon at its insertion into the patella. It causes a painful catching sensation when the extensor
mechanism traverses over the trochlear notch as the knee extends from 45° of flexion to 30° from full extension. It characteristically occurs in posterior stabilized total knee arthroplasties and appears to be related to femoral component design. The syndrome can usually be prevented by excising the residual synovial fold just proximal to the patella. Flexion gap instability can also cause a painful total knee arthroplasty but is less common in posterior stabilized implants. Femoral component malrotation can cause pain attributable to a flexion gap imbalance or patellar tracking problems. Polyethylene wear would be unlikely after just 1 year. Patellar clunk syndrome can usually be addressed successfully with arthroscopic synovectomy. Recurrence is uncommon. Physical therapy may help to strengthen the quadriceps following synovectomy but would not resolve the clunk syndrome symptoms. Femoral or tibial insert revision is not indicated if patellar clunk syndrome is the only problem resulting in a painful total knee arthroplasty.
**Question 93**
Which modality has the broadest application for the reduction of postsurgical transfusion?
1. Regional anesthesia
2. Tranexamic acid (TXA) administration
3. Reduced transfusion trigger
4. Hypotensive anesthesia
CORRECT ANSWER: B
DISCUSSION:
TXA is easy to administer, inexpensive, and safe for virtually all patients. Multiple studies have demonstrated transfusion rates lower than 3% for total knee arthroplasty and lower than 10% for total hip arthroplasty. Regional and hypotensive anesthesia effectively reduce transfusion; however, they cannot be used in as wide a range of patients as can TXA. A reduced transfusion trigger must be considered along with patient symptoms when determining the need for transfusion.
**Question 94**
When do most symptomatic thromboembolic events occur after total joint arthroplasty?
D. More than 3 months after surgery
1. On the day of surgery
2. Within the first week after surgery
3. Between 1 week and 6 weeks after surgery
CORRECT ANSWER: C
DISCUSSION:
Most clinical venous thromboembolism events occur between the second and sixth weeks after surgery. It is estimated that 10% of patients are readmitted to the hospital within the first 3 months after total hip or knee arthroplasties. Most pulmonary events on the day of surgery are related to fat embolism or cardiac events.
**Question 95** When comparing arthroscopic lavage and knee debridement with placebo in patients with chronic symptomatic osteoarthritis, what outcome has been demonstrated?
1. Reliable and durable pain relief
2. No significant benefit for chronic osteoarthritis
3. Up to 75% pain relief for 2 months, then variable response
4. Three-month measurable pain relief, followed by recurrence
CORRECT ANSWER: B
DISCUSSION:
Excluding a diagnosis of meniscal tear, loose body, or mechanical derangement, treating knee osteoarthritis of indeterminate cause with arthroscopic lavage and debridement has been found to provide no discernable benefit to offset the risk of surgery. The effects of arthroscopy have not been clinically significant in the vast majority of patient-oriented outcomes measures for pain and function at multiple times between 1 week and 2 years after surgery.
**Question 96** Figure below shows the abdominal radiograph obtained from a 70-year-old woman who experiences nausea and abdominal tightness 48 hours following left total knee arthroplasty performed under general anesthesia. She received 24 hours of cefazolin antibiotic prophylaxis and a patient-controlled analgesia narcotic pump for pain management. She has been receiving warfarin for thromboembolic prophylaxis. Her severe abdominal distension and markedly decreased bowel sounds are most likely secondary to the administration of

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1. general anesthesia.
2. antibiotics.
3. warfarin.
4. narcotics.
CORRECT ANSWER: D
DISCUSSION:
The radiograph reveals severe intestinal dilatation, which has occurred as the result of acute colonic pseudo-obstruction and is associated with excessive narcotic administration following total joint arthroplasty. Anesthetic type, antibiotic administration, and warfarin have not been associated with this obstruction. Electrolyte imbalances such as hypokalemia have been associated with postsurgical acute colonic pseudo-obstruction.
**Question 97** Venous thromboembolism may occur after total joint arthroplasty. The risk of this complication is elevated in patients with
1. a BMI lower than 30.
2. diabetes mellitus, with a hemoglobin A1c test result less than 7.
3. tranexamic acid use.
4. metabolic syndrome.
CORRECT ANSWER: D
DISCUSSION:
Obesity, a prior history of venous thromboembolism, and metabolic syndrome have all been associated with an increased risk of thromboembolism. A recent meta-analysis showed that diabetes had no significant relationship with venous thromboembolism following hip or knee arthroplasty. Tranexamic acid is an antifibrinolytic agent that has been shown to reduce blood loss substantially following hip and knee arthroplasty. It has also been shown to be safe in patients with severe medial comorbidities and a prior history of venous thromboembolism.
**Question 98** A 70-year old woman undergoes revision total knee arthroplasty for tibial component aseptic loosening. She is concerned about recurrent loosening, and tibial stem fixation options during revision are reviewed. Figure below displays a radiograph of the revision technique used for this patient. What is the incidence of intraoperative tibial shaft fracture that is associated with this type of revision surgery?

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1. 0% to 1% with press-fit tibial stems
2. 3% to 5% with press-fit tibial stems
3. 3% to 5% with cemented tibial stems
4. More than 5% with press-fit tibial stems
CORRECT ANSWER: B
DISCUSSION:
Using press-fit tibial stems during a hybrid revision total knee arthroplasty is associated with a 3% to 5% incidence of intraoperative tibial shaft fracture. Diaphyseal fixation of press-fit stems has the advantage of setting component alignment, dispersing forces on the proximal tibia, and offers excellent clinical results. The disadvantages include proximal and distal tibia anatomic mismatch and tibial shaft fracture. Cipriano and associates reported a tibial shaft fracture incidence of 4.9% in a series of 420 consecutive
knee revisions. All fractures healed with nonsurgical management, and none led to implant loosening. In this patient, it is important to recognize on the radiograph that this technique is a hybrid method of revision total knee arthroplasty, with cementation along the tibial tray and metaphysis and with press-fit fixation of the diaphyseal engaging stem. Then, it is important to know the risk and management of intraoperative diaphyseal tibial fractures. Cemented tibial stems are associated with a low rate of intraoperative fracture, because the implant is typically undersized to allow for an appropriate cement mantle. Option C is incorrect, because this revision is not cemented. Option A underestimates the incidence of fracture, whereas D overestimates the rate of fracture.
**Question 99** Figures below depict the radiographs obtained from a 60-year-old man with instability and pain 1 year after primary right total knee arthroplasty. He states that he had surgery on two occasions for a tendon rupture that was repaired with sutures but that his knee popped again, and now the leg is unable to hold his weight. On examination, he is in no acute distress. His height is 6'3", and he weighs 240 pounds. He is ambulatory with crutches. Range of motion of the right knee is 50° to 120° actively and 0° to 120° passively. More than 10° of varus/valgus laxity and more than 5 mm of anteroposterior drawer are present. A palpable defect is observed in the tissue just proximal to the patella. The incision is well healed. The erythrocyte sedimentation rate is 46 mm/h (reference range 0 to 20 mm/h) and the C-reactive protein level is 2.04 mg/L (reference range 0.08 to 3.1 mg/L). Aspiration of the right knee reveals hazy yellow fluid with a white blood cell count of 120 and 1% neutrophils. No growth of organisms is seen on routine culture. What is the best next step?

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1. Revision total knee arthroplasty with extensor mechanism allograft
2. Revision total knee arthroplasty with liner change and primary quadriceps repair
3. Resection knee arthroplasty and arthrodesis with antegrade nail
4. Two-stage revision total knee arthroplasty with extensor mechanism allograft
CORRECT ANSWER: A
DISCUSSION:
This patient has a chronic quadriceps tendon rupture after total knee arthroplasty. Two previous primary repair attempts have failed, which is not surprising based on the poor results of primary repair reported in the literature. The patient also has an unstable knee and will require revision of some or all of the prosthesis to achieve a stable knee. Revision total knee arthroplasty with extensor mechanism allograft allows an allograft reconstruction of the ruptured quadriceps tendon. The other option is to utilize a synthetic mesh extensor mechanism reconstruction. These are likely to have the best result in this situation. Revision total knee arthroplasty with liner change and primary quadriceps repair is not the best form of management, because it involves a third attempt at primary tendon repair, which will likely fail again. Resection knee arthroplasty and arthrodesis with antegrade nail is a possible option but is not the best, because it would likely make driving and other daily activities difficult. Two-stage revision total
knee arthroplasty with extensor mechanism allograft is not the best option because the laboratory results show no signs of infection, so a single-stage procedure is preferred.
**Question 100** A 60-year-old man who underwent left partial knee arthroplasty 6 months earlier was doing well until he experienced left knee pain and swelling for 4 weeks following a dental procedure. The left knee aspirate was bloody, with a white blood cell count of 8,000 and 70% neutrophils. Culture grew group B Streptococcus (_Granulicatella adiacens_), and serologies were elevated, with an erythrocyte sedimentation rate of 55 mm/h (reference range: 0 to 20 mm/h) and a C-reactive protein level of 24 mg/L (reference range: 0.08 to 3.1 mg/L). What is the best next step?
1. Arthroscopic debridement
2. Two-stage total knee revision arthroplasty
3. Resection arthroplasty without an antibiotic impregnated cement spacer
4. Knee fusion
CORRECT ANSWER: B
DISCUSSION:
This complication is best addressed with either a single-stage or two-stage total knee arthroplasty. A recent report suggests that a single-stage arthroplasty can be effective, although many surgeons would perform a two-stage procedure with an articulating or static spacer. Arthroscopic would be non-effective, especially given 4 weeks of symptoms. Resection arthroplasty without a spacer would leave an unstable _and poorly functioning extremity. Knee fusion should be used as a salvage procedure._

- Cam-type femoroacetabular impingement with an acetabular labral tear

- MRI

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Duchenne muscular dystrophy is a recessive, X-linked, inherited disorder. Most (90%) untreated boys with this disorder develop progressive scoliosis, secondary to muscle weakness, after becoming full-time wheelchair users. Several studies suggest that the long-term use of glucocorticoids has prolonged effects against detrimental aspects of Duchenne muscular dystrophy.
The widespread use of glucocorticoids for patients with Duchenne muscular dystrophy has dramatically decreased the development of scoliosis and need for subsequent surgical intervention. There is still much to be learned about the impact of glucocorticoids on the spine, including the duration of glucocorticoid treatment needed to reduce the risk of a progressive curve and whether this treatment merely delays the onset. In recent studies in which researchers followed young men into their twenties, it was shown that glucocorticoids protect against the development of scoliosis well past skeletal maturity.
Posterior spinal instrumentation and fusion are recommended in those whose spinal curve is >20°, are prepubertal, and are not on glucocorticoids because progression of the curve is expected. Although patients taking glucocorticoids may still develop a scoliosis, it is reasonable to wait until progression is documented. When surgery is done to correct scoliosis, it is recommended that those with a pelvic obliquity of >15° also have stabilization and fusion into the pelvis. This helps patients with seating and positioning. Fusion to the L5 is sufficient for patients who do not have a severe pelvic obliquity. With surgical intervention of the spine, the aim is to reduce the patient’s pain, improve his ability to sit comfortably, and prevent further progression.

A standard popliteal nerve block is performed with the patient prone. The injection aims for the area at, or close to, the peroneal and tibial nerves. The sural nerve branches distal to the injection site, so this nerve and the superficial peroneal, deep peroneal, and tibial nerves are covered with the injection. The saphenous nerve is in an anteromedial location at knee level and is not close enough to the area covered by the posterior injection to be included in the analgesic effect.
RECOMMENDED READINGS
[Varitimidis SE, Venouziou AI, Dailiana ZH, Christou D, Dimitroulias A, Malizos KN. Triple nerve block at the knee for foot and ankle surgery performed by the surgeon: difficulties and efficiency. Foot Ankle Int. 2009 Sep;30(9):854-9. PubMed PMID: 19755069. ](http://www.ncbi.nlm.nih.gov/pubmed/19755069)[View Abstract at](http://www.ncbi.nlm.nih.gov/pubmed/19755069)[ ](http://www.ncbi.nlm.nih.gov/pubmed/19755069)[PubMed](http://www.ncbi.nlm.nih.gov/pubmed/19755069)
[Hromádka R, Barták V, Popelka S, Jahoda D, Pokorný D, Sosna A. [Regional anaesthesia of the foot achieved from two cutaneous points of injection: an anatomical study]. Acta Chir Orthop Traumatol Cech. 2009 Apr;76(2):104-9. Czech. PubMed PMID: 19439129. ](http://www.ncbi.nlm.nih.gov/pubmed/19439129)[View](http://www.ncbi.nlm.nih.gov/pubmed/19439129)[ ](http://www.ncbi.nlm.nih.gov/pubmed/19439129)[Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/19439129)
[Tran D, Clemente A, Finlayson RJ. A review of approaches and techniques for lower extremity nerve blocks. Can J Anaesth. 2007 Nov;54(11):922-34. Review. PubMed PMID: 17975239. ](http://www.ncbi.nlm.nih.gov/pubmed/17975239)[View Abstract at PubMed](http://www.ncbi.nlm.nih.gov/pubmed/17975239)
CLINICAL SITUATION FOR QUESTIONS 42 THROUGH 44

42A

B
Figures 42a and 42b are the radiographs of a 32-year-old man with an accessory navicular, pes planovalgus deformity, and an associated gastrocnemius contracture. He has been treated with custom orthotics and a physical therapy program for several years and has progressed to stage II posterior tibial tendon dysfunction (PTTD). This patient is now interested in surgery. Tendon reconstruction with bony procedure to correct alignment, medializing calcaneal osteotomy with lateral column lengthening, and a subtalar arthroereisis implant are discussed with the patient.

Flap necrosis and infection rates are lowest if free flap coverage is performed within 72 hours of injury. Delays beyond 72 hours are associated with a higher rate of complications.
REFERENCES: Godina M: Early microsurgical reconstruction of complex trauma of the extremities. Plast Reconstr Surg 1986;78:285-292.
Manske PR (ed): Hand Surgery Update. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 31-37.

- revision posterior instrumentation with extension of the fusion to T1 to span the area of junctional kyphosis.

Maintenance of adequate hydration is the single most important factor affecting athletic performance. While carbohydrate loading may be beneficial for some endurance athletes, the consumption of carbohydrates during exercise does not appear to be beneficial for athletes engaged in events that last less than 1 hour. In general, athletes consuming a balanced diet do not need electrolyte supplementation.
REFERENCES: Maughan RJ, Noakes TD: Fluid replacement and exercise stress: A brief review of studies on fluid replacement and some guidelines for the athlete. Sports Med 1991;12:16-31.
Barr SI, Costill DL, Fink WJ: Fluid replacement during prolonged exercise: Effects of water, saline, or no fluid. Med Sci Sports Exerc 1991;23:811-817.

DISCUSSION: The 2007 AAOS guidelines for thrombophlebitis prophylaxis for patients undergoing total hip and knee arthroplasty includes preoperative risk assesment for deep venous thrombosis, pulmonary embolism, and

bleeding. Regional anesthesia when appropriate is suggested. Inferior vena cava filters may be appropriate in selected patients. When warfarin is used as a chemoprophylactic agent, the goal INR is less than or equal to 2 to minimize the risk of bleeding. This is in contrast to the 2004 ACCP guidelines for warfarin with a goal INR of 2-3.
-

REFERENCE: American Academy of Orthopaedic Surgeons Guideline on the Prevention of Symptomatic Pulmonary Embolism in Patients Undergoing Total Hip or Knee Arthroplasty. [www.aaos.org/Research/](http://www.aaos.org/Research/) guidelines/PEguide.asp

Figure 46

Landsmeer (oblique retinacular ligament) runs from the flexor tendon sheath of the proximal phalanx to the lateral extensor tendon as they insert onto the base of the proximal phalanx. A stay or retaining ligament maintains centralization of the extensor tendons.

The fracture has occurred around the stem, representing a Vancouver type B fracture, and the stem is clearly loose, making it a type B2 fracture. The appropriate treatment is removal of the loose in situ stem; ORIF of the femur using cerclage wires, cables, or a plate; and insertion of a longer revision stem such as a tapered fluted modular titanium or fully porous coated cylindrical stem to bypass the fracture. All of the other options are incorrect, because they represent inappropriate treatment options for a Vancouver type B2 fracture.

62
The patient's radiographs and CT scan show advanced glenohumeral osteoarthritis with posterior humeral head subluxation and mild posterior glenoid erosion (Walch type B2 glenoid). The preferred type of shoulder arthroplasty in this setting remains controversial, as there are data to support both anatomic and reverse total shoulder arthroplasty. There is no significant atrophy of the rotator cuff musculature on sagittal CT to suggest a rotator cuff tear, and a rotator cuff repair is likely contraindicated by the degree of underlying arthritis. A glenohumeral joint debridement would be expected to provide only partial/short-term pain improvement, and is unlikely to be a long- term solution. A shoulder hemiarthroplasty has been shown to result in worse pain relief and functional outcomes than total shoulder arthroplasty in this setting.

Aneurysmal bone cysts frequently occur in the first two to three decades of life. Patients report pain and a slow-growing lesion. Radiographs show an expansile lesion with septae or striations.Treatment is usually curettage and grafting of the lesion. In the foot, unicameral bone cysts are seen most frequently in the calcaneus, and are usually incidental findings rarely requiring treatment. Infection or acute osteomyelitis typically shows lucency of bone, periosteal reaction, and a permeative pattern on radiographs.
Patients often have systemic complaints as well. Giant cell tumor is usually seen in the epiphysis of long bone with radiographs revealing a radiolucent lesion with a small rim of reactive bone.

---

Proximal humeral fractures in children are classified as metaphyseal or Salter-Harris type I or II fractures, and most of these fractures are treated with closed methods. Eighty percent of the growth of the humerus comes from the proximal physis; therefore, tremendous remodeling potential is present. Indications for open reduction include open fractures or severely displaced fractures in adolescents with minimal growth remaining. Acceptable limits of reduction in adolescent proximal humeral fractures include bayonet apposition and angulation of less than 35°. Common blocks to reduction in adolescents include the biceps tendon and periosteum. For this fracture, use of a shoulder sling without reduction will lead to healing and an excellent result as the proximal humerus remodels.
REFERENCES: Kohler R, Trillaud JM: Fracture and fracture separation of the proximal humerus in children: Report of 136 cases. J Pediatr Orthop 1983;3:326-332.
Beaty JH: Fractures of the proximal humerus and shaft in children. Instr Course Lect 1992;41:369-372.
Dobbs MB, Luhmann SL, Gordon JE, et al: Severely displaced proximal humeral epiphyseal fractures. J Pediatr Orthop 2003;23:208-215.
Beringer DC, Weiner DS, Noble JS, et al: Severely displaced proximal humeral epiphyseal fractures: A follow-up study. J Pediatr Orthop 1998;18:31-37.
Wang P Jr, Koval KJ, Lehman W, et al: Salter-Harris type III fracture-dislocation of the proximal humerus. J Pediatr Orthop B 1997;6:219-222.

Lateral condylar fractures are challenging to treat because of late displacement and development of a nonunion that may lead to valgus instability, pain, or tardy ulnar nerve palsy. Fractures such as this one with more than 2 mm of displacement on any radiographic view are prone to nonunion and should be stabilized. Fractures with less than 2 mm of displacement usually are stable and may be treated nonsurgically. In these patients, careful follow-up is recommended within several days of casting to check for fracture displacement. Arthrography or MRI may be helpful in these minimally displaced fractures. Fractures with an intact articular cartilage surface, such as noted on these studies, are unlikely to displace further.
REFERENCES: Finnbogason T, Karlsson G, Lindberg L, et al: Nondisplaced and minimally displaced fractures of the lateral humeral condyle in children: A prospective radiographic investigation of fracture stability. J Pediatr Orthop 1995;15:422-425.
Attarian DE: Lateral condyle fractures: Missed diagnoses in pediatric elbow injuries. Mil Med 1990;155:433-434.
Flynn JC: Nonunion of slightly displaced fractures of the lateral humeral condyle in children: An update. J Pediatr Orthop 1989;9:691-696.
Badelon O, Bensahel H, Mazda K, et al: Lateral humeral condylar fractures in children: A report of 47 cases. J Pediatr Orthop 1988;8:31-34.

OCD is an acquired lesion of the subchondral bone. Patients with OCD initially report nonspecific pain and variable amounts of swelling. Initial radiographs help identify the lesion and establish the status of the physes. An MRI scan is useful for assessing the potential for the lesion to heal with nonsurgical treatment. Nonsurgical treatment is appropriate for small, stable lesions in patients with open physes and focuses on activity restriction for 3 to 9 months. Surgical treatment is necessary for unstable or detached lesions. Stable lesions with intact articular cartilage can be treated with subchondral drilling to stimulate vascular ingrowth, with radiographic healing at an average of 4.4 months. Fixation is indicated for unstable or hinged lesions, and stabilization of the fragment can be achieved using a variety of implants through an arthroscopic or open approach. The fragment should be salvaged and the normal articular _surface restored whenever possible._

Anteversion of the humeral component may result in anterior instability of the component. Posterior instability after total shoulder arthroplasty is usually the result of some combination of the following factors: untreated anterior soft-tissue contractures, excessive posterior capsular laxity, and excessive retroversion of the humeral and/or glenoid components.
REFERENCES: Cofield RH, Edgerton BC: Total shoulder arthroplasty: Complications and revision surgery. Instr Course Lect 1990;39:449-462.
Wirth MA, Rockwood CA Jr: Complications of total shoulder replacement arthroplasty. J Bone Joint Surg Am 1996;78:603-616.
69. A 70-year-old man seen in the emergency department has had left shoulder pain and a fever of 101.5 degrees F (38.6 degrees C) for the past 3 days. He denies any history of trauma. Examination reveals tenderness anterosuperiorly and at the posterior glenohumeral joint line. He has very limited range of motion (passive and active). Laboratory studies show a WBC count of 12,000/mm3 and an erythrocyte sedimentation rate of 48 mm/h. Initial management should consist of
1- an oral cephalosporin antibiotic and discharge home.
2- IV oxacillin and gentamicin.
3- arthroscopic drainage of the glenohumeral joint.
4- open irrigation and drainage of the glenohumeral joint.
5- aspiration of the glenohumeral joint and subacromial space with Gram stain and culture of the fluid.
PREFERRED RESPONSE: 5
DISCUSSION: It appears that the patient has septic arthritis of the glenohumeral joint; therefore, initial management should consist of aspiration of the glenohumeral joint and subacromial space separately, followed by Gram stain and culture of the fluid. Based on the findings, broad-spectrum IV antibiotics should be started. If the diagnosis of septic arthritis is confirmed, then arthroscopic or open surgical drainage usually is indicated.
REFERENCES: Sawyer JR, Esterhai JL Jr: Shoulder infections, in Warner JJ, Iannotti JP, Gerber C (eds): Complex and Revision Problems in Shoulder Surgery. Philadelphia, PA, Lippincott-Raven, 1997.
Leslie BM, Harris JM, Driscoll D: Septic arthritis of the shoulder in adults. J Bone Joint Surg Am 1989;71:1516-1522.

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The images demonstrate osteochondritis dissecans. The history of pain with even mild activity such as walking, presence of effusion, and limited range of motion raise concern for an unstable lesion. MRI is the best modality to detect this and would be the next indicated step in evaluation.
CT is better for delineating bony anatomy, not the stability of the lesion. Arthroscopy is not indicated before MRI. Patients with stable lesions and open physes can heal their lesions without surgery. Physical therapy would not be appropriate without first determining the stability of the lesion.

- Figure 59b is the radiograph of a 45-year-old man with acromiohumeral distance equal to 7 mm. He is able to actively raise his arm above shoulder level, has lateral arm pain, and abduction and external rotation weakness.

**30 • American Academy of Orthopaedic Surgeons**

DISCUSSION: The occurrence of a forearm fracture in a 9-month-old child has a greater than 50% chance that the injury is due to child abuse. It is mandatory to report this to child protective services unless there is some compelling reason that it is definitely not child abuse. In addition, a skeletal survey should be requested to look for other injuries. A bone scan would show other injuries, but a skeletal survey is a more efficient way to evaluate for other fractures. A MRI of the brain is not indicated unless fimdoscopic examination reveals an abnormality.

REFERENCES: Kocher MS, Kasser JR: Orthopaedic aspects of child abuse. J Am Acad Orthop Surg 2000;8:10/- 20.
Chang DC, Knight V, Ziegfeld S, et al: The tip of the iceberg for child abuse: The critical roles of the pediatric trauma service and its registry. J Trauma 2004;57:1189-1198.

58
The MRI scans reveal an acute ACL rupture with pivot shift contusions in the lateral tibiofemoral compartment and a bucket handle tear of the medial meniscus. Additionally, there is likely a radial tear of the lateral meniscus at the anterior horn/body junction (Figure 4). Figure 1 shows a bucket handle tear of the medial meniscus with the posterior horn displaced anteriorly. Figure 3 shows a double posterior cruciate ligament sign. Figure 2 shows the ACL tear and Figure 4 shows the pivot shift contusions. There is no evidence of PCL injury on examination or imaging.

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This patient has the diagnosis of X-linked hypophosphatemic rickets, which is associated with a mutation in the PHEX gene. Answer A demonstrates the typical lab findings with this diagnosis. Answer B is associated with vitamin D-dependent rickets type 1. Answer C is associated with hypophosphatasia. Answer D is associated with renal osteodystrophy.

Repetitive overhead slams and serves may produce a traction injury to the distal branch of the suprascapular nerve. Bankart, biceps, and superior labrum anterior and posterior injuries can occur but usually do not produce visible atrophy. Muscle avulsion is uncommon.
REFERENCES: Ferretti A, Cerullo G, Russo G: Suprascapular neuropathy in volleyball players. J Bone Joint Surg Am 1987;69:260-263.
Bigliani LU, Dalsey RM, McCann PD, April EW: An anatomical study of the suprascapular nerve. Arthroscopy 1990;6:301-305.

of the mechanism mediating this effect. Whereas all of the above have been postulated as explanations, more recent studies have
demonstrated that nicotine delivered via a transdermal patch significantly enhanced posterior spinal fusion in rabbits. Thus it appears that the effects of smoking on fracture healing are multifactorial and not yet fully understood.

In the intertrochanteric hip fracture displayed, a sliding hip screw (SHS) or cephalomedullary nail (CMN) would be indicated; the SHS is the cheaper implant.
In a standard obliquity intertrochanteric fracture without lateral wall comminution, an SHS is a cost-effective option. In reverse obliquity fractures or those with lateral wall comminution (unstable), there is an increased failure rate with this implant and an CMN should be considered. There is some controversy in terms of short and intermediate nail indications, which are attractive because they do not require reaming. SHS implants are contraindicated in subtrochanteric fractures. Although some hospitals receive discounts on implants, in general, intramedullary nail options are more expensive than SHS.
Swart et al. examined the cost-effectiveness of different fixation options for intertrochanteric hip fractures. They compared SHS and CMN implants using an expected-value decision-analysis model, taking into account fracture patterns, failure rates, and revision costs. In their study, the average cost of a SHS was
$2,000 compared to $3,200 for a standard CMN. They concluded that the SHS was likely more cost-effective for stable and questionably stable fractures compared to CMN fixation; CMN was more cost-effective for reverse obliquity patterns.
Kaplan et al. provided a review article on the surgical management of intertrochanteric fractures. Factors to determine treatment should include the patient's medical co-morbidities, pre-existing arthritis, bone quality, and fracture morphology. Their study did not find an appreciable difference in patient outcomes using either CMN or SHS for stable intertrochanteric fractures; surgeon experience and implant costs should, therefore, drive the decision making process for implant selection.
Figures A and B are AP and lateral right hip radiographs, respectively, demonstrating a standard obliquity intertrochanteric hip fracture. Illustration A is an AP post-operative radiograph showing a hip fracture treated with a SHS.
Incorrect Answers:
Answers 1 and 2: Both of these options are appropriate for this fracture but more costly than a SHS.
Answer 4: Arthroplasty is not indicated for this patient with an intertrochanteric fracture and preserved joint space.
Answer 5: Cannulated screws are not indicated for an intertrochanteric fracture.

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The patient has a classic hyperflexion neck injury with clinical resolution of neck pain upon follow-up. Furthermore, lack of historical radiculopathy or myelopathy, maintained normal neurological exam static, and dynamic radiographs rule out occult ligamentous or disk injury of the cervical spine. Accordingly, this patient’s cervical spine can be clinically and radiographically cleared without indication for further advanced imaging. However, the initial distractor of predominant neck pains should not overshadow the likelihood that this patient had a concussive event and remains symptomatic with headaches and inability to concentrate. Clearance to return to sport poses the risk of second impact and is not advisable. Prompt evaluation by traumatic head injury clinic or concussion clinic is imperative. Physical therapy may be beneficial if patient has persistant trapezial or periscapular symptoms but should not be prioritized over prompt concussion evaluation and treatment.

Salvage of a total elbow arthroplasty is possible with early aggressive management of acute infection (symptoms for less than 30 days) with serial irrigation and debridement and antibiotic bead placement. This form of treatment is indicated when there are no radiographic or intraoperative signs of loosening. However, successful treatment is largely dependent on the organism. Staphylococcus epidermidis is associated with persistent infection because it is an encapsulating organism, and it is best treated with implant removal and
IV antibiotics.
REFERENCES: Yamaguchi K, Adams RA, Morrey BF: Infection after total elbow arthroplasty. J Bone Joint Surg Am 1998;80:481-491.
Schoifet SD, Morrey BF: Treatment of infection after total knee arthroplasty by debridement with retention of the components. J Bone Joint Surg Am 1990;72:1383-1390.

- FGFR-1, FGFR-2, and FGFR-3.

Lacerated radial nerves are associated with open humeral fractures. All open humeral fractures with radial nerve palsy should be managed with radial nerve exploration and skeletal stabilization. Closed humeral fractures with associated radial nerve palsy usually have an intact nerve with neurapraxia. Most of these patients recover without surgical treatment. If the patient has multiple injuries, skeletal stabilization may be indicated to improve mobilization. For an isolated closed humeral fracture with a radial nerve palsy, the treatment of choice is splinting for 1 to 2 weeks, followed by a humeral fracture brace.
REFERENCES: Ring D, Chin K, Jupiter JB: Radial nerve palsy associated with high-energy humeral shaft fractures. J Hand Surg Am 2004;29:144-147.
Foster RJ, Swiontkowski MF, Bach AW, et al: Radial nerve palsy caused by open humeral shaft fractures. J Hand Surg Am 1993;18:121-124.

If a single flexor digitorum profundus (FDP) tendon is debrided more than 1 cm prior to repair, the tendon is advanced too far distally, essentially shortening the musculotendon unit. The finger will likely develop a flexion posture. Because of the common muscle belly and interconnections of the profundi, the long and small fingers adjacent to the injured finger will be affected because of loss of some of their normal proximal excursion. The result is an inability of the adjacent fingers to completely flex. This condition, known as quadrigia, is named after the Roman chariot driver who held control of the reins of 4 horses, forcing them to move as 1. Quadrigia occurs when the FDP tendon is advanced too far distally, when a tendon graft is too short, or when the profundus is sutured over the end of an amputated digit. Intrinsic muscles of the hand flex the metacarpophalangeal (MP) joints and extend the PIP joint. Intrinsic tightness causes decreased PIP flexion when the MP joint is in extension. The lumbrical muscle modulates tension on the flexor profundus tendon. When a tendon graft to repair the profundus tendon is too long, a lumbrical plus deformity occurs. This is a paradoxical PIP extension as the finger is flexed. Disruption of the tendon
repair causes limited flexion of the injured finger.

The pisotriquetral joint is best seen on a lateral view in 30 degrees of supination. The carpal tunnel view provides visualization of the joint but to a lesser extent. The other views do not provide clear and accurate visualization.
REFERENCES: Paley D, McMurty RY, Cruickshank B: Pathologic conditions of the pisiform and pisotriquetral joint. J Hand Surg Am 1987;12:110-119.
Steinmann SP, Linsheid RL: Pisotriquetral loose bodies. J Hand Surg 1997;22:918-921.
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The clinical imaging and lab results are suggestive of osteomyelitis, although tumor could also present in this manner. The plain radiographs are unremarkable, but the MRI shows a distal tibial lesion, which is enhancing, as well as a large subperiosteal fluid collection. This is most consistent with osteomyelitis and an associated soft-tissue abscess. To obtain a source culture and gain control of the infection, incision and drainage are required. The subperiosteal abscess and intramedullary purulence must be drained. Once the source culture has been obtained, antibiotics can be started.
Referring the patient to a musculoskeletal oncologist is not appropriate, as the MRI is most consistent with infection, not tumor. Antibiotics alone will not treat the abscess. Although biopsy of the tibia will most likely result in obtaining a source culture, the subperiosteal abscess remains undecompressed.

Flexion instability is common following revision total knee replacement. The following principles are important:
Undersizing the femoral component is common. This occurs secondary to the posterior femoral condyle bone loss.
Anterior translation of the femoral component increases the flexion gap. The use of posterior femoral condyle augments or an offset stem can solve this problem.
Distal femoral augments that are too thick will narrow the extension gap. One should set the joint line approximately 25 mm to 30 mm below the epicondylar axis.
Excessive size of the patellar component will restrict knee flexion, however, it will not change the flexion and extension gaps. Correct Answer: There is excessive thickness of the distal femoral augmentation blocks.

- Wound-healing problems_

The clinical presentation is consistent with end-stage arthritis in a valgus knee. All of the factors listed are risk factors for peroneal nerve palsy EXCEPT female gender, which is not a risk factor.
Peroneal nerve palsy is a potential serious complication of TKA in patients with a pre-operative valgus knee deformity. Peroneal nerve palsy is likely caused by lengthening of the lateral aspect of the knee and subsequent traction on the peroneal nerve. It is generally recommended that patients be evaluated
carefully for symptoms postoperatively. If peroneal nerve palsy symptoms are discovered, the knee should be flexed to relax the tension that is effectively being placed on the nerve. If peri-operative nerve exploration or decompression is undertaken, the posterior border of the biceps-femoris tendon is the proper site of identification.
Idusuyi et al. published a retrospective review of 32 postoperative peroneal nerve palsies in thirty patients in which they identified possible risk factors. Prior proximal tibial osteotomy, lumbar laminectomy (thought to be a “double-crush” phenomenon), and preoperative valgus alignment of 12 degrees or more were all identified as risk factors. Other concerns included epidural anesthesia for postop pain control, preoperative flexion contractures and tourniquette time greater than 120 minutes also increased concern.
Favorito et al reviewed valgus total knee arthroplasty and reported that the most common complications of patients with a valgus deformity include: tibiofemoral instability (2% to 70%), recurrent valgus deformity (4% to 38%), postoperative motion deficits requiring manipulation (1% to 20%), wound problems (4% to 13%), patellar stress fracture or osteonecrosis (1% to 12%), patellar tracking problems (2% to 10%), and peroneal nerve palsy (3% to 4%).
Figure A demonstrates and AP radiograph of the knee showing end-stage arthritis with severe lateral compartment narrowing.
Incorrect Answers:

: Pre-operative flexion contracture >10 degrees is a risk factor for postoperative peroneal nerve palsy due to stretching the nerve, causing neurologic ischemia.
Answer 2: History of lumbar laminectomy is thought to place patients at risk for postoperative peroneal nerve palsy because of the "double-crush" phenomenon.
Answer 4: Valgus deformity >12 degrees increases the risk for postoperative peroneal nerve palsy due to stretching the nerve beyond functional tolerance postoperatively.
Answer 5: Epidural anesthesia has been found to be significantly associated with post-operative peroneal nerve palsy. Idusuyi et al postulate that the decrease in proprioception and sensory stimuli that accompany epidural anesthesia postoperatively allow the limb to rest in an unprotected state, thus placing the limb at risk for neurologic ischemia from local compression.

An 82-year-old woman falls and sustains the fracture shown in figure A. She denies any history of dislocation or prodromal pain prior to her fall. What is the most appropriate treatment?
1) Toe-touch weightbearing

2) Open reduction internal fixation with a cable plate

3) Revision of the femur with a long, cementless stem

4) Revision of the femur with a long, cemented stem

5) Girdlestone resection arthroplasty

The radiograph demonstrates a periprosthetic femur fracture extending to the tip of the stem. The long spiral fracture is consistent with a loose implant. The bone stock is sufficient. Therefore, this fracture pattern would classify as a B2 using the Vancouver classification system. The Vancouver classification for periprosthetic femoral fractures is simple yet incorporates all the pertinent factors such a location, stem fixation, and bone stock. Type A is a trochanteric fracture- lesser or greater. These can be treated non-operatively usually and ORIF if symptomatic. Type B fractures are around or just below the stem and are subdivided into three types. Type B1 is a fracture with a well fixed stem.
The treatment is cable plating or allograft struts or a combination of the two. Type B2 is a fracture with a loose stem with good bone stock. The treatment is a cementless porous coated long stem atleast two diameter length past the
fracture site. Type B3 is a fracture with a loose stem and comminution. For younger patients, use cementless porous coated long stems with allograft struts. For older patients, consider a tumor prosthesis. Cement fixation is sometimes necessary Type C is a fracture well below the stem tip. These can be treated independently of the prosthesis.
Springer et al showed optimal outcomes with revision involving long extensively-coated femoral stems for Vancouver B fractures.
Masri et al review the classification and treatment of periprosthetic femur fractures.

A 67 year-old woman sustained an ACL tear while playing basketball when she was 35 years-old. She has noted progressive leg deformity and episodes of giving way, and now has pain preventing activity. Non-operative management has failed to provide relief. Treatment should consist of?
1) Opening wedge high tibial osteotomy with autograft

2) Closing wedge proximal tibial osteotomy

3) Medial interpositional arthroplasty

4) Medial unicompartmental knee arthroplasty

5) Total knee arthroplasty

The radiograph seen in Figure A reveals varus alignment of the knee, with medial tibial deficiency; from this X-ray the patient appears to have unicompartmental arthritis. Treatment options for unicompartmental arthritis include high tibial osteotomy, interpositional arthroplasty, unicondylar knee replacement and total knee replacement. Interpositional arthroplasty became popular in the 1950’s when early outcomes analysis seemed to indicate good results; long term follow up in one study found 0/12 excellent results, with all patients requiring conversion to TKA. This procedure is no longer recommended due to the poor long term outcomes.
While an osteotomy is still used for young and active patients, unicompartmental or total knee arthroplasty have largely replaced this treatment in older patients. Advantages of UKA and TKA include more predictable relief of pain, quicker recovery, and better long-term results. Criteria for UKA include limited unicompartmental disease, no more than a fixed 10 degrees of varus or 5 degrees of valgus deformity from neutral and an intact anterior cruciate ligament with no signs of medial lateral subluxation of the femur on the tibia; this patient is therefore not a good candidate for this procedure.
Total knee arthroplasty can be used to provide predictable pain relief in a patient with unicompartmental and tricompartmental degenerative disease and varus malformation of the knee and for this patient is the best option.

A 65-year old healthy male has just undergone primary total knee arthroplasty. Which of the following is associated with use of a closed suction drain in this procedure?

1) Increased incidence of wound dehiscence

2) Increased incidence of transfusion

3) Decreased incidence of infection

4) Decreased incidence of hematoma formation requiring return to OR

5) Decreased pain scores on post-op days 1 and 2

The cited meta-analysis by Parker et al evaluated 18 studies with 3495 patients (3689 wounds) and demonstrated that closed suction drainage increases the transfusion requirements after elective hip and knee arthroplasty (relative risk, 1.43; 95% confidence interval, 1.19 to 1.72). They found no significant effect on wound hematoma, infection, or operations for wound complications.

A 75-year-old man underwent total hip arthroplasty 10 years ago. He now reports mild groin pain which has been increasing lately. What is the most likely explanation for the finding in Figure A indicated with the arrows?
1) Osteosarcoma

2) Galvanic corrosion of the modular components

3) Polyethlene wear particles tracking through the effective joint space

4) Joint sepsis

5) Occult fracture

Osteolysis of the pelvis is a common complication associated with total hip arthroplasty. Osteolysis affects sockets with and without cement, and has been attributed to the biologic reaction to wear debris. With well-fixed cementless sockets, an expansile pattern of osteolysis is usually seen.
The radiographic appearance has a radiolucent area that starts at the implant-bone interface and expands into the cancellous bone away from the implant.
This pattern of osteolysis can be explained with the concept of effective joint space. This concept states that joint fluid and wear particles will flow according to pressure gradients and follow the path of least resistance.
The Level 5 review article by Chiang discusses osteolysis in further depth.

All of the following are risk factors for post-operative total knee arthroplasty periprosthetic supracondylar femur fractures EXCEPT:

1) Rheumatoid arthritis

2) Parkinson's disease

3) Chronic steroid therapy

4) Revision knee arthroplasty

5) Male gender

Rheumatoid arthritis, Parkinson's disease, chronic steroid therapy, osteopenia, and female gender have all been found to be risk factors for postoperative periprosthetic supracondylar femur fractures. Male gender has not been found to be a risk factor.
Su et al discuss risk factors for supracondylar periprosthetic femoral fractures which include rheumatoid arthritis, neurologic disorders such as Parkinson's disease, chronic steroid therapy, and revision knee arthroplasty. Analysis of the Mayo Clinic joint registry by Berry found that females are at increased risk of postoperative periprosthetic fracture, likely due to the increased incidence of osteoporosis. There is controversy regarding anterior cortical notching (Illustration A) and increased risk for periprosthetic fracture.
Lesh et al performed a biomechanical study on the consequences of anterior femoral notching. Using cadaveric matched femora with and without full thickness anterior cortex defects above TKA implants, they found that notching decreased both bending and torsional strength in the supracondylar region of the femur. They also found that fracture orientation differed between the two groups following the application of a bending load.
Ritter et al in a series of 670 total knee arthroplasties, of which 27% had notching (
A 64-year-old woman with osteoarthritis underwent bilateral total knee replacement 3 years ago. Current radiographs are shown in Figure A. She reports a 3-month history of bilateral knee pain while at rest and increasing swelling in the knees. Her ESR and CRP are elevated and bilateral knee aspiration cultures reveal Staphylococcus aureus. What is the most likely outcome if the patient undergoes simultaneous, bilateral knee resection arthroplasty with cement spacer and a course of intravenous antibiotics?
1) Prosthesis reimplantation with need for multiple surgical debridements at 2-year follow-up

2) 20% risk of above knee amputation

3) Retention of antibiotic cement spacer and low chance of successful prosthesis reimplantation at 2-year follow-up

4) 50% rate of conversion to knee fusion following resection arthroplasty

5) Successful prosthesis reimplantation at 2-year follow-up with less than 20% revision rate

This patient presents with bilateral total knee arthroplasty infection.
Wolff et al report Level 4 evidence of 18 patients followed an average of 5 years after bilateral TKA infection. Eleven patients were initially treated with attempts to salvage the original prosthesis (polyethylene l liner exchange, I&D, IV antibiotics and chronic oral suppressive antibiotics. With prosthesis retention, 9/11 (81%) developed recurrent infection at a mean of 15 months. The other 10 patients initially underwent resection arthroplasty with cement spacer and a course of IV antibiotics. Seven of the 10 (70%) underwent reimplantation at a mean of 3 months (6 weeks to 5 months) and none of the patients required revision at mean of two years follow up. Satisfaction rates were significantly higher among this group of patients. The authors advocate the protocol of bilateral TKA resection arthroplasty with cement antibiotic spacer and course of IV antibiotics followed by prosthesis reimplantation.

During insertion of a cementless femoral stem, a nondisplaced fracture is noticed along the femoral calcar. Which of the following is the most appropriate next step in surgical management?

1) Continued insertion of the stem, cerclage wiring around the fracture site, and non-weight bearing x6 weeks

2) Continued insertion of the stem, reduction of the hip, and non-weight bearing activity restrictions following surgery

3) Removal of the stem, cerclage wiring around the fracture site, and re-insertion of a stem

4) Removal of the stem and conversion to a cemented femoral stem

5) Removal of the stem, open reduction internal fixation of the femur with planned delayed femoral stem insertion following fracture healing

Appropriate care of an intraoperative fracture during total hip arthroplasty requires removal of the stem to adequately evaluate the fracture. The fracture should then be stabilized with cerclage wiring, and a long stem should be inserted to ensure stability of the stem in the postoperative period.
Tsiridis et al review the identification, classification, and management of intraoperative and postoperative periprosthetic hip fractures. Postoperative fractures around stable components may be treated with open surgical fixation. All intra-operative fractures should be considered inherently unstable, and should be treated with a long stem that bypasses the femoral fracture as well as cerclage wiring.
Incorrect Answers:
Answer 1: If there is a fracture while inserting the final femoral stem, it should be removed, a cerclage wire should be placed, then the final stem should be inserted.
Answer 2: The fracture creates an unstable situation with the femoral stem, and this should be stabilized intraoperatively to prevent settling, continued pain, and possible instability.
Answer 4: Simple conversion to a cemented stem with a proximal fracture, without cerclage placement, will lead to a loss of hoop stresses as the fracture can continue to displace during pressurization.
Answer 5: There is no need to delay femoral implant insertion to a second stage.

A 72-year-old male presents 2 years status post fixation of an impending pathologic right femur fracture due to metastatic renal cell carcinoma. He is minimally ambulatory due to pain. Despite radiation therapy, there has been progression of the lesion with extensive cortical bone loss, which is shown in Figure A. A proximal femoral replacement arthroplasty is performed without complications, and is demonstrated in Figure B. Which of the following is true regarding this patients post-operative course?
1) Deep prosthetic infection is the most common complication

2) Mean Harris Hip score will likely not improve

3) The patient will most likely continue to be minimally ambulatory

4) Aseptic failure rate at 5 years is >50%

5) Pre-operative radiation decreases the risk of infection post-operatively

Deep prosthetic infection is the most common complication after hip arthroplasty performed for salvage of failed internal fixation after pathologic proximal femoral fracture secondary to malignancy.
Jacofsky et al reviewed the complications in 42 patients with a mean age of 63 who were treated with hip arthroplasty for salvage of failed treatment of a pathologic proximal femoral fracture. Multiple different constructs were used.
The most common complication was deep prosthetic infection, which occurred in nearly 10% of the patients studied. All infections occured in patients whom had previously received radiation. The mean Harris Hip score improved from 42 to 83 points post-operatively, and 41 of the 42 patients were ambulatory at follow-up. Implant survivorship free of revision for any reason at 5 years was 90%, and free of revision for aseptic failure or radiographic failure was 97%.
Figure A shows a lytic lesion of the proximal femur with an intramedullary implant. Figure B shows a proximal femoral replacement.

All of the following are true for a patient who underwent a metal-on-metal total hip arthroplasty (THA) EXCEPT?

1) they will have production of ionically charged wear particles

2) there is a higher cancer risk than with metal-on-polyethylene THA

3) they will have elevated levels of cobalt and chromium in the serum

4) they will have elevated levels of cobalt and chromium in the urine

5) there is a higher frictional torque than with ceramic on ceramic THA

Metal-on-metal articulations in THA are characterized by ionically charged wear particles. Elevated serum and urine concentrations of metallic elements including chromium, cobalt, and molybdenum are found in patients with metal-on-metal joint replacements as compared with controls. To date, there is no correlation between metal serum levels and cancer risk. As such, the link between metal on metal arthroplasty and an elevated cancer risk has not been supported by hard data. Finally, metal-on-metal THA has higher frictional torque than ceramic on ceramic THA.
The reference by Brockett et al is a biomechanical analysis of the friction of various hip arthroplasty components. Ceramic on ceramic was found to have the lowest coefficient of friction, followed by ceramic on metal.

A 62-year-old woman is undergoing a revision total knee arthroplasty for aseptic component loosening. The surgeon has all the trial components in place and recognizes that the soft tissues are balanced in the coronal plane, but the knee is 10 degrees from reaching full extension. He proceeds to correct the contracture by
making an additional 2mm cut off of the tibia and is successful in achieving full extension. What is the most likely effect of this additional resection?

1) Loss of full flexion

2) Flexion instability

3) Extension instability

4) Valgus instability

5) Varus instability

This patient presents with asymmetric gapping because she is tight in extension and balanced in flexion. Ries discusses that resection of the proximal tibia in this situation is a common pitfall in surgical technique as it “will resolve the flexion contracture but produce instability in flexion”. The preferred method of restoring the distal femoral joint line to achieve full extension and maintain flexion stability is to cut “more of the distal part of the femur, as this will not affect the flexion space”. Similarly, there is an asymmetric gap if full extension is achieved, but flexion is limited. The lack of full flexion can be treated with distal femoral augments and a thinner tibial insert.

A 67-year-old diabetic male presents 4 months status post right total knee arthroplasty (TKA) complaining of pain and stiffness for the last four weeks. A clinical photograph is shown in Figure A. Radiographs and a bone scan are shown in Figures B, C and D. Blood work shows an ESR of 14mm/hr (normal 0-12mm/hr) and a CRP of 2mg/L (normal 1-3mg/L). Knee aspiration yields WBC of 1000, 30% PMNs, and a negative gram stain. He finished a 14-day course of antibiotics prescribed to him by his primary care physician one week ago. Which of the following is the most appropriate next step in management?
1) Broad-spectrum, empiric oral antibiotics

2) Repeat aspiration after one week

3) Irrigation and debridement of the right knee with a polyethylene liner exchange

4) One-stage irrigation and debridement of the right knee with a component exchange

5) Two-stage component removal, antibiotic spacer placement and subsequent revision

The clinical scenario describes a patient with an equivocal presentation of a periprosthetic joint infection (PJI) and recent history of antibiotic use. As such, a repeat aspiration in one week is indicated.
The work-up of a suspected PJI after TKA includes an evaluation of radiological (x-ray +/- bone scan and PET scan) and laboratory (ESR and CRP) parameters as well as analysis of joint aspirate fluid (cell count and differential, culture, gram stain +/- PCR).
Barrack et al. evaluated the utility of routine aspiration of a symptomatic TKA before reoperation and found aspiration to have a sensitivity of 75%, specificity of 96%, and accuracy of 90%. Previous antibiotic use increased the
risk of a false negative result, and reaspiration at a later date was found to significantly improve the value of this test in such cases.
Parvizi et al. published an AAOS Clinical Practice Guideline (CPG) on the diagnosis of PJI of the hip and knee using evidence from the literature. They found sufficient evidence to make strong recommendations for the use of ESR, CRP, joint aspiration, intraoperative gram stain, frozen sections of peri-implant tissues, multiple intraoperative cultures and withholding antibiotics until after cultures have been obtained.
The Workgroup Convened by the Musculoskeletal Infection Society proposed diagnostic criteria for PJI after the evaluating the available evidence and suggested that a definite PJI exists when: (1) there is a sinus tract communicating with the prosthesis; or (2) a pathogen is isolated by culture from 2 or more separate tissue or fluid samples obtained from the affected prosthetic joint; or (3) when 4 of the following 6 criteria exist: (a) elevated serum erythrocyte sedimentation rate and serum C-reactive protein (CRP) concentration, (b) elevated synovial white blood cell count, (c) elevated synovial polymorphonuclear percentage (PMN%), (d) presence of purulence in the affected joint, (e) isolation of a microorganism in one culture of periprosthetic tissue or fluid, or (f) greater than 5 neutrophils per high-power field in 5 high-power fields observed from histologic analysis of periprosthetic tissue at ×400 magnification.
Figure A is a clinical photograph demonstrating a swollen, erythematous right knee with a well-healed incision from a previous TKA. Figure B and C are AP and lateral radiographs of the right knee with no obvious acute findings. Figure D is a bone scan demonstrating increased uptake in the post-operative knee, which is consistent with the 4 month follow-up.
Incorrect Answers:
Answer 1, 3, 4 & 5: Broad-spectrum antibiotics, I & D +/- liner exchange, one stage and two stage revision would not be appropriate at this time point as the diagnosis remains unclear.

Internal rotation of the femoral component during total knee arthroplasty can result in which of the following?

1) Increased need for lateral release

2) Decreased post-operative pain

3) Increased polyethylene thickness

4) Decreased post-operative Q angle

5) Elevation of the native joint line

Internal rotation of the femoral component during total knee arthroplasty causes increased lateral patellar subluxation forces, which effectively increases the Q angle. Femoral component rotation, in isolation, does not affect the position of the joint line or dictate the necessary polyethylene thickness.
Internal rotation of the femoral component can be a source of increased pain post-operatively. Sodha et al compared the rates and results of lateral release before and after femoral component placement. The rates of lateral release in internally rotated femoral components was 24% for varus deformities and 33% for valgus deformities. When the femoral component was externally rotated, based off the transepicondylar axis in 246 TKA's, lateral release rates of 7% in varus deformities and 29% in valgus deformities were noted.
Illustration A demonstrates internal rotation of the femoral component, and increased lateral patellar subluxation.

The schematic shown in Figure A displays a ceramic-on-ceramic total hip arthroplasty articulation with impingement. Which of the
following modifications would increase the primary arc range of motion?
1) Addition of a collar on the femoral head

2) Exchanging the ceramic liner with a hooded polyethylene liner

3) Increasing the femoral head size

4) Increasing the femoral offset

5) Increasing the acetabular anteversion

The assessment of hip stability involves four major areas: component design, component alignment, soft tissue tensioning, and soft tissue function. The primary determinant of primary arc range is the head-neck ratio, which is defined as the ratio of the femoral head diameter to the femoral neck diameter. Increasing the size of the femoral head will increase the excursion distance of the femoral head to dislocate, thus making the hip more stable.
Illustration A shows how a greater head-to-neck ratio may improve range of motion before impingement. Increasing femoral component offset increases the abductor moment arm and reduces the resulting hip joint reactive force but does not affect primary arc range of motion impingement.
The article by Yoon et al reports that ceramic-on-ceramic constructs are susceptible to osteolysis resulting from particulate debris. The histologic reaction to the smaller ceramic particles was similar as the reaction to larger particles such as polyethylene. The debris in the listed study was found to be largely from the articulation and was also thought to be secondary to a decreased head-neck ratio leading to impingement.

A patient who has previously undergone a high tibial osteotomy 10 years prior is scheduled for a total knee arthroplasty (TKA). Which of the following factors is most likely to be present and may complicate the arthroplasty?

1) Collateral ligament instability

2) Patella alta

3) Patella baja

4) Patellar tendon insufficiency

5) Severe varus deformity

TKA after a high tibial osteotomy (HTO) can be more difficult to perform than a primary knee replacement because of a shift of the proximal tibial articular surface in relation to the medullary canal, retained hardware, previous skin incisions, scar tissue, and altered patellofemoral mechanics caused by patella baja and contraction of the patella tendon. The frequency of valgus deformity is greater following HTO.
Parvizi et al reviewed 166 TKA's performed following a high tibial osteotomy. A higher rate of component loosening was observed with 8% revision at 5.9 years follow-up. Male gender, preoperative limb malalignment, young age, and collateral ligament instability were associated with higher rates of failure.
Meding et al reviewed 39 patients who had bilateral TKA performed following unilateral high tibial osteotomy. There were no differences between the two
groups including postoperative complications, range of motion, revision surgery, and patient satisfaction scores.

Osteopenia has what effect on the strength of the bone-cement interface in comparison to normal bone?

1) no effect

2) improved mechanical integrity (higher fracture resistance)

3) diminished mechanical integrity (low fracture resistance)

4) reduced depth of cement penetration into bone

5) less affected by cement pressurization

The increased porosity seen in osteopenia and osteoporosis actually helps create a stronger bone-cement interface. Graham et al studied the effects of bone porosity, trabecular orientation, cement pressure, and cement penetration depth on fracture toughness at the bone-cement interface in bovine femora. They found that improved mechanical integrity (higher fracture resistance) is correlated with increased bone porosity (worsening osteopenia) and maximum cement penetration depth. The authors also found that with increased cement pressurization, the cement penetration depth was increased and the fracture resistance was also increased. In conclusion, "a lack of porosity is associated with reduced mechanical integrity of the cemented interface and may contribute to the relatively poorer results of cement fixation in young male patients." The fracture resistance of the bone-cement interface is greatly improved when the ability of the cement to flow into the intertrabecular spaces is enhanced."

Figure A demonstrates a total knee prosthesis design. Which of the following motions is constrained in this particular design:
1) Complete anterior-posterior translation constraint only

2) Partial varus-valgus angulation constraint only

3) Partial varus-valgus angulation and partial internal-external rotation constraint

4) Complete internal-external rotation constraint only

5) Complete varus-valgus angulation and anterior-posterior translation constraint

Figure A demonstrates a non-linked, constrained total knee arthroplasty prosthesis. This drawing depicts the degree of coronal plane and rotational constraint provided by the tall, wide tibial spine in the deep femoral box. This design constrains varus-valgus (allows 2°-3°) and internal-external rotation (allows 2°). A linked, rotating-hinge prosthesis (Illustration A) constrains anterior-posterior translation in addition to varus-valgus and internal-external rotation.
The article by Scuderi reports that in revision TKA, the goal is to restore the original anatomy, restore function, and provide a stable joint. To this point of stability, it is preferable to implant the prosthesis that provides adequate stability with the least mechanical constraint possible to avoid bone-implant stresses that may cause early loosening. Therefore, it is preferable to use a posterior-stabilized (cruciate substituting) articulation (Illustration B) if the knee remains stable without constrained components.
McAuley et al suggest that more predictable results are obtained with the use of cruciate-substituting components. However, if there is functional loss of the medial collateral ligament or lateral collateral ligament, inability to balance the flexion and extension spaces, or a severe valgus deformity, then a constrained
condylar prosthesis is needed.
Rodriguez et al reports Level 4 evidence of 44 patients revised with varus-valgus constrained implants followed for an average of 5.5 years. There was a theoretical concern that the increased constraint of the prosthesis would lead to component loosening, however their series had only one femoral component and no tibial components that loosened.

A surgeon is planning to revise a left hip resurfacing component to a total hip arthroplasty. He wishes to decrease the joint reaction force of the left hip by increasing the femoral offset. Which of the following labeled measurements found in Figure A best describes femoral offset?
1) Line 1

2) Line 2

3) Line 4

4) Line 5

5) Line A

In total hip arthroplasty, the femoral component offset is measured as distance between the center of the femoral head and a line drawn down the center of the femoral shaft(Line 4 shown in Figure A). Increased femoral offset is also shown in Illustration A.
The review article by Bourne et al states that offset is relevant to soft tissue balancing around the hip and the forces generated at the hip joint.
Lateralization of the femoral shaft restores offset, reduces femoropelvic impingement, and increases abductor muscle tension leading to a decreased joint reaction force. However, increasing femoral offset may have the unwanted effect of increasing rotational torque on the stem leading to aseptic loosening and increasing trochanteric bursitis.

A 62-year-old woman presents for her 1-year follow-up after a revision right total hip arthroplasty. She has no complaints of pain and has returned to all her activities of daily living. An AP radiograph is shown in Figure A. The black arrow in the radiograph indicates she is at higher risk for which of the following?
1) Aseptic loosening

2) Aseptic lymphocytic vasculitis-associated lesions (ALVAL)

3) Dislocation

4) Third body wear

5) Catastrophic ceramic bearing failure

The radiographs reveal a constrained system by the metal ring of the constrained liner, and subsequent broken ring representing a dissociation of the liner. Ring failure is associated with increased risk of hip dislocation. The incidence of dislocation ranges from 0.5% to 10% after primary and up to 28% after revision THA. Procedures described to treat this instability include reorientation of femoral or acetabular component position, trochanteric reattachment or advancement, capsulorrhaphy, the use of an elevated acetabular liner, conversion to a bipolar prosthesis, lengthening of the femoral neck, resection arthroplasty, or the use of a constrained acetabular component.
In the Level 4 study by Shapiro et al, 85 constrained THAs were implanted during revision THA for chronic instability. There was a 2.4% dislocation rate in this cohort and both of these were secondary to constrained liner dissociation. Illustration A shows a radiograph of a constrained hip dislocation secondary to
fracture of the constraining ring on the neck of the liner. An example of a broken constraining ring is shown in Illustration B.

Which of the following characteristics of stromelysin is incorrect?

1) Belongs to the family of proteolytic enzymes called metalloproteinases

2) Secreted by chondrocytes

3) Inhibited by Tissue Inhibitor of Metalloproteinase

4) Inhibited by plasmin

5) Degrades cartilage and is thought to play a role in degenerative joint disease

Stromelysin is not inhibited by plasmin.
Metalloproteinases (MMPs) are a family of proteolytic enzymes which utilizes a metal during the catalytic process. Stromelysin and plasmin are two examples of metalloproteinases, both secreted by chondrocytes, which have degradative action against cartilage. It is believed that these metalloproteinases play a role in articular degeneration and degenerative joint disease. Tissue inhibitor of metalloproteinase inhibits the degradative action of stromelysin. Tissue inhibitor of metalloproteinase (TIMPs) counteract the proteolytic enzymes produced by chondrocytes.
Tetlow et al performed an experiment on the superficial zone of cartilage in in osteoarthritis specimens. They found cells that immunostain for IL-1beta, TNFalpha, and 6 different MMP's which support the concept that cytokine-MMP associations reflect a modified chondrocyte phenotype and an intrinsic process of cartilage degradation in OA.

What preoperative knee deformity puts a patient at most risk for a postoperative peroneal nerve palsy after total knee arthroplasty?

1) Valgus deformity only

2) Valgus and flexion contracture

3) Varus and flexion contracture

4) Varus deformity only

5) Flexion contracture only

Conditions that have been associated with an increased prevalence of peroneal nerve injury include a significant fixed valgus deformity and flexion contracture. Immediate treatment of a peroneal nerve palsy post-operatively includes dressing removal and flexion of the knee 20-30 degrees.
Ayers et al report a 0.58% cumulative prevalence of peroneal nerve palsy
after TKA in their review article. They state that possible mechanisms of nerve injury include traction during correction of a valgus deformity, ischemia when stretching of the surrounding soft tissue causing occlusion of small vessels, and compression by a tight dressing or splint.
In a more recent review article, Nercessian et al report a peroneal nerve palsy incidence of 0.3-1.3% after primary total knee arthroplasty. Their reviewed studies reported a preoperative valgus deformity of 18-23.3 degrees, and flexion deformity of 15.5-22 degrees as being risk factors for peroneal nerve palsy after TKA.

Osteolysis occurs because there is a histiocytic response by macrophages to wear debris. What size particles are implicated in osteolysis?

1) less than 1 micron (submicron)

2) approximately 10 microns

3) approximately 100 microns

4) approximately 1000 microns

5) approximately 5000 microns

Osteolysis is the histiocytic response by macrophages to wear debris particles, which are often less than 1 micron in size.
Osteolysis is a particle-induced biological process occurring at the bone-metal or bone-cement interface around total joints resulting in rapidly expanding focal lesions that may or may not cause loosening. Its slower counterpart, aseptic loosening, involves the identical biological process. Wear particles generated within the joint space are phagocytosed and stored within cells in the joint capsule. Sub-micron particles are retained within macrophages and are implicated in osteolysis.
Campbell et al. described an isolation method to recover ultra-high-molecular-weight polyethylene (UHMWPE) particles from tissues around failed total hip replacements. This process yielded particles that had rounded or elongated shapes. Additionally, the majority of particles isolated were reported to be submicron in size.
Mckellop reviews four topics in wear including Modes, Mechanisms, Damage and Debris. Four Modes that creates debris are described. Wear Mode 1 occurs
when the two bearing surfaces are articulating against each other in the manner intended by the implant designer. Mode 2 occurs when a bearing surface articulates against a non-bearing surface. Mode 3 occurs when third-body abrasive particles have become entrapped between the two bearing surfaces, and Mode 4 occurs when two non-bearing surfaces are wearing against each other.
Incorrect Answers:
As reported by Campbell et al. the majority of particles recovered from prosthetic joints with osteolysis were submicron in size. Answer choices 2, 3, & 4 contain values greater than a micron and are therefore incorrect.

A 62-year-old female underwent a primary total knee arthroplasty of the left knee 10 days ago. She presents to clinic with skin necrosis of the midline incision. There is no deep infection present upon aspiration of the knee joint. She undergoes superficial irrigation and debridement and is left with exposed patellar tendon as shown in Figure A. What is the most appropriate next step in management?
1) Split thickness skin grafting

2) Twice daily wet-to-dry dressing changes with Dakin's solution until healing by secondary intention

3) Latissimus dorsi free flap transfer

4) Vacuum-assisted closure device until healing by secondary intention

5) Medial gastrocnemius muscle flap transfer and skin grafting

Medial gastrocnemius muscle flap transfer and skin grafting is the most appropriate choice of the options listed (postoperative image shown in Illustration A).
Level 4 evidence by Ries describes 9 patients sustained skin necrosis after total knee arthroplasty. Seven of these cases were over the patella tendon or tibial tubercle, of whom 6 were treated with medial gastrocnemius flap coverage. Successful wound healing and salvage of the TKA was achieved in all cases. Ries concluded that necrosis of the proximal wound including the area over the patella can be treated by local wound care and skin grafting.
However, skin necrosis over the tibial tubercle or patellar tendon requires muscle flap coverage to prevent extensor mechanism disruption and deep infection.

A 58-year-old man has significant pain and stiffness after undergoing right total knee arthoplasty 6 months ago. A current radiograph and bone scan are shown in Figures A and B. Labs show an ESR of 45mm/hr (normal 0-20) and a CRP of 13.5 mg/l(normal
1) Two-stage component removal, antibiotic spacer placement and subsequent revision

2) Observation with repeat ESR and CRP in one week

3) Surgical debridement and polyethylene exchange only

4) Repeat aspiration and culture

5) One-stage irrigation and debridement with exchange of all components

The clinical scenario describes a patient with an equivocal presentation of an infected total knee. The radiographs are normal and the bone scan shows uptake as would be expected 6 months out. A repeat aspiration is indicated in cases of equivocal laboratory aspiration data.
Mason et al in 2003 reviewed 440 revision TKA's of which 86 had preoperative aspirations. The aspirations yield 55 aseptic failures and 31 septic failures. The mean WBC of the aseptic group was 645 cells/mm(3) compared to 25,951 cells/mm(3) for the septic group (P=1100 cells/mm3 and PMN > 64% are suggestive of infection. When both tests were below these respective values, the negative predictive value was 98.2%.

Figures A and B are pre-operative and intra-operative radiographs of a 67-year-old male that has undergone a left total hip arthroplasty under general anesthesia. The patient had no motor deficits preoperatively. During the operation, the trial acetabular and femoral components were positioned and reduced with no complication. Intraoperative leg lengths were equal. Before implanting the real components, the surgeon and anaesthesiologist performed a wake up test, which revealed that the patient was unable to dorsiflex the left foot. What would be the most appropriate next step in the management of this patient?
1) Urgent electromyogram and nerve conduction study

2) Continue with sized trial components and observe the motor function in surgical recovery area

3) Remove all implants and insertion of cement spacer

4) Perform a shortening subtrochanteric osteotomy

5) Urgent neurology consult

This patient has undergone a left THA with significant leg lengthening. The biggest concern is stretch to the sciatic nerve. The most appropriate step at this stage would be to perform a subtrochanteric osteotomy to decrease leg length and sciatic nerve stretch.
Patients with DDH that have undergone a large limb-lengthening procedure are at a greater risk due to the significant stretch of the sciatic nerve. Intraoperative procedures that have been shown to prevent this outcome include good pre-operative planning, limb lengthening
A 45-year-old woman is scheduled to undergo a TKA. Which of the following implant designs theoretically reduces poylethylene wear and reduces bone-implant-interface stress?

1) Mobile-bearing TKA

2) Posterior stabilized fixed bearing TKA

3) Cruciate retaining fixed bearing TKA

4) Constrained TKA

5) Mobile-bearing hinged TKA

Total knee arthroplasties continue to be performed in patients who are younger and more active. As a result of this trend, better wear performance is imperative for long-term durability. Research continues to be done to determine optimal wear characteristics of different polyethylene and metal surfaces. Mobile-bearing knee systems are distinguished from conventional, fixed-bearing systems in that they allow dual-surface articulation between an ultra-high molecular weight polyethylene insert and metallic femoral and tibial tray components. This results in increased sagittal femorotibial conformity of most mobile-bearing implants, which reduces polyethylene shear stresses and should lessen polyethylene wear rates. By allowing more contact area, the surface and subsurface stresses in the poly bearing are significantly reduced (recall that pressure = force / area).
The ICL by Callaghan et al review the early findings of studies of fixed versus mobile bearing implants. Research is progressing as long term data continues to be collected and analyzed. Despite theoretical advantages, there has been no documented improvement in survivorship between mobile and fixed bearing TKA's in short and intermediate term studies.

Which of the following intra-operative techniques during total knee arthroplasty (TKA) decreases the need for lateral retinacular release?

1) Internal rotation of femoral component

2) External rotation of femoral component

3) Internal rotation of tibial component

4) Lateralization of patellar component

5) Insertion of a posterior cruciate retaining device

The only answer choice above that decreases the need for a lateral release during TKA is external rotation of the femoral component. Internal rotation of the femoral component increases lateral subluxation forces on the patella, and will increase the need for a lateral release.
Akagi et al looked at the relationship of femoral component rotation on lateral releases on 44 consecutive patients undergoing TKA. Twenty-two patients had femoral component set parallel to the posterior condylar axis, while twenty-two patients had femoral components set at 3-5 degrees of external rotation to the posterior condylar axis. Only 6% of patients in the externally rotated group required a lateral release, vs 33% of the neutrally aligned group.
Parker et al showed that extensor mechanism failure is the most common reason for revision TKA. They discuss the morbidity of patellar tracking which can be caused by either internal rotation of the femoral or tibial component. Furthermore, they recommend intra-operative assessment of patellar tracking with both trial and final implants. If maltracking is present in the presence of an inflated thigh tourniquet, they recommend tourniquet deflation before lateral release as this can alter patellar maltracking. A lateral release should only be considered if lateral tilt or maltracking continues in the presence of properly aligned femoral and tibial components.

When placing acetabular screws to supplement cementless acetabular fixation in total hip arthroplasty, placing screws in which zone poses the highest risk to damaging the external iliac vasculature?

1) anterior-inferior zone

2) anterior-superior zone

3) posterior-inferior zone

4) posterior-superior zone

5) oblique zone

The acetabulum is divided into four quadrants with two bisecting lines. One from the ASIS to center of acetabular socket and the second is perpendicular to it. This is a source of repeat questions concerning the danger/safe zones of various quadrants for placement of acetabular screws. anterosuperior quadrant may injure the external iliac artery and vein. The anteroinferior quadrant may injure the obturator artery, nerve, or vein. The posterosuperior quadrant may injure the sciatic nerve, superior gluteal nerve and vessels and is considered the "safe zone". Posteroinferior quadrant may injure the inferior gluteal, internal pudendal structures. In general, posterior quadrants are safe except if long screws are placed posteroinferiorly. See illustration A. Wasielewski et al conclude "quadrant system provides the surgeon with a simple intraoperative guide to the safe transacetabular placement of screws during primary and revision acetabular arthroplasty."

Which of the following factors MOST places the knee at risk of patellar maltracking in total knee arthroplasty?

1) Thickness of patellar resection

2) Cruciate retaining component

3) Medial placement of patellar component

4) Preoperative patellar tilt

5) Lateral placement of patellar component

Level 4 evidence by Kawano et al found that lateral patellar component position has been shown to directly correlate with lateral subluxation and maltracking. The study also found that there was no significant influence of the thickness of the patellar resection and preoperative patellar tilt on postoperative patellar tracking.
Avoiding implantation of the patellar component in a lateral position is paramount to tracking. Lateral positioning of the patellar component is shown in Illustration A.
An ideal percentage for patella component placement was calculated as 40-45% with the following equation: Distance of medial resected edge to central peg/length of patellar resection surface *100.

During a primary total knee arthroplasty, trial of components demonstrates a knee that is balanced in flexion and loose in extension. Which of the following will balance the flexion and extension gap?

1) Distal femur resection only

2) Distal femur augmentation and use of the same size polyethylene

3) Downsize femoral component and use a thinner polyethylene insert

4) Proximal tibia resection only

5) Distal femur augmentation and thicker polyethylene insert

The goal in sagittal balancing of TKA is to obtain a gap that is equal in flexion and extension. General principles to remember: 1. Changing the distal femur only affects extension, 2. Changing the femoral component size only affects flexion, and 3. Changing the proximal tibia/polyethylene insert affects both extension and flexion. In the above scenario, distal femoral augmentation will correct the "looseness in extension" without changing the "balanced flexion".
The above principles are reviewed by Ries et al along with soft tissue balancing principles for stability in the coronal plane.

A 69-year-old female 16 years status post total knee arthroplasty complains of knee pain. A radiograph is provided in Figure A. Which of the following is true regarding the pathogenesis of the bony abnormality seen in the distal femur?
1) It is related to the toughness of the polyethylene liner

2) It is more likely to occur with highly cross-linked polyethylene compared to conventional polyethylene

3) It is caused by macrophage activation by polyethylene particles

4) It is most frequently caused by infection

5) It occurs more frequently in patients taking immunosuppressive medications.

The radiograph demonstrates polyethylene wear and osteolysis around the femoral component of a total knee replacement. Osteolysis is caused by macrophage activation from polyethylene particles. Ingham et al reviews the pathologic role of macrophages in osteolysis. Answer #1 is incorrect because toughness of the polyethylene is not related to wear rate, but does affect its overall mechanical strength. Answer #2 is incorrect because highly cross-
linked polyethylene liners have lower wear rates compared to conventional polyethylene. The listed reference by Huang concludes that there is an increased rate of osteolysis in mobile bearing TKA. This is a contradictory finding as mobile-bearing designs were created to decrease the stress and subsequent wear of the polyethylene

A 41-year-old male has steroid-induced avascular necrosis of the hip and decides to undergo metal on polyethylene total hip arthroplasty. His 80-year-old, sedentary father had a total hip replacement 5 years ago. With comparison to his father, the patient should be informed of the following risk?

1) Increased risk of sciatic nerve palsy

2) Increased longevity of prothesis

3) Increased risk for polyethylene wear and osteolysis

4) Reduced range of motion

5) Lower likelihood of revision surgery

A younger, active patient will sustain more polyethylene wear and osteolysis due to greater activity levels and more years of use.
Kim et al prospectively studied 98 consecutive patients with osteonecrosis of the femoral head with an average follow-up was 9.3 years. Although there was no aseptic loosening of the components, they reported a high rate of linear wear of the polyethylene liner and a high rate of osteolysis in these high-risk young patients (16% in cemented femoral stems, 24% in uncemented stems).

In evaluating methods of polyetheylene sterilization for hip arthroplasty, gamma-irradiation in air compared to irradiation in an inert substance results in which of the following?

1) No difference in regards to outcome

2) Higher rate of cross-linking when irradiated in air

3) Lower rate of oxidation when irradiated in air

4) Accelerated wear and failure when irradiated in air

5) Better wear resistance and longevity when irradiated in air

The standard of care is irradiation of polyethylene (PE) in an inert gas (e.g. argon, nitrogen or vacuum packaging). Irradiation of PE in air (i.e. oxygen present) results in oxidized PE while irradiation in the absence of oxygen results in greater cross-linking.
The quoted studies by McKellop et al and Sychtez et al both demonstrate that irradiation in air results in early PE delamination and cracking and accelerated failure due to increased oxidation.

A 67-year-old man who underwent total hip arthroplasty (THA) 4 years ago fell on to his right hip. His pre-injury right hip film is seen in Figure A while films of his current injury are seen in Figures B and C. Prior to the fall he had no thigh or hip pain. His ESR and CRP are within normal limits. During intraoperative assessment, the acetabular and femoral stems are found to be well fixed. What is the next best course of action?
1) Revision of the acetabular component and ORIF of the femur with locking plates and cerclage wires

2) Revison of the femoral component, bypassing the fracture by two cortical diameters

3) Revision of the femoral component with impaction grafting and cerclage wires

4) Revision to a cemented component, bypassing the fracture by two cortical diameters

5) ORIF of the femur with locking plates and cerclage wires

This patient has a periprosthetic hip fracture at the level of the stem with a stable prosthesis, indicated open reduction and internal fixation as the treatment of choice.
The Vancouver Classification can be helpful in clinical decision-making regarding fixation versus revision of periprosthetic hip fractures of the proximal femur. A stable implant, by nature, does not need to be revised in the setting of adequate bone stock for fixation, but the ultimate test of stability should be in the operating room. Many fixation strategies are appropriate, but many implants include locking plate fixation for concerns of stress-shielded bone around the implant as well as use of unicortical fixation at the level of the stem.
Pike et al review the current trends in treating B1 fractures including locking plates with strut allografts, minimally invasive plate osteosynthesis (MIPO) and locking plates spanning femoral THA and TKA stems in selected patients. The authors conclude that no studies currently provide evidence establishing one
technique over the other and recommend treatment on a case by case basis.
Illustration A shows a possible fixation construct for this patient's fracture. The Vancouver Classification is seen in Illustration B and Illustration C represents an algorithm for treatment options.
Incorrect Answers:
1-4: All other answer choice include revising the implants, which is unnecessary based on this question stem.

While performing a cementless total hip arthroplasty in a healthy 68-year-old female, the surgeon notes an audible change while impacting the final broach. The broach is removed and a 1cm longitudinal crack originating at the calcar is visualized. Bone stock is otherwise preserved. What is the next best step in management?

1) Insert standard press-fit stem, weight bearing as tolerated postoperatively

2) Apply cerclage wire, insert standard press-fit stem, weight bearing as tolerated postoperatively

3) Insert long porous-coated stem, touch down weight bearing postoperatively

4) Insert long cemented stem, weight bearing as tolerated postoperatively

5) Insert long porous-coated stem, augment with cortical allograft and cerclage wires, touch down weight bearing postoperatively.

The patient has sustained an intraoperative proximal femur fracture and should be managed with placement of cerclage wire to prevent propagation of the fracture, insertion of the press-fit stem as planned, followed by weight bearing as tolerated postoperatively.
Intraoperative periprosthetic femur fractures occur in 1-18% of primary total hip arthroplasties (THA). Risk factors include the use of minimally invasive
techniques, press-fit cementless stems, revision surgeries, female sex, metabolic bone disease, Paget disease and intraoperative technical errors. Management of these fractures depends on timing of recognition (intraoperative or postoperative) and appropriate classification of the fracture (Vancouver classification for intraoperative fractures; Illustration A), which is dictated by fracture location, bone quality and implant stability. fMinimally displaced fractures at the calcar (Type A2) occur most often during broaching and are managed with removal of the broach, application of a cerclage wire around the fracture followed by insertion of the implant. Weight bearing does not need to be restricted postoperatively, as these minimally displaced calcar fractures are stable following cerclage wiring and implant placement. If implant stability is compromised or bone quality is poor (Type A3), a long diaphyseal stem may be used to bypass the defect. Minimally displaced fractures at the implant tip discovered immediately postoperatively may be managed with touch down weight bearing alone.
Berry reviewed management of perioperative fractures during THA. Minor cracks can be managed intraoperatively with cerclage fixation. Fractures noted postoperatively that do not affect implant stability or femoral integrity may be successfully managed with limited weight bearing and observation. Unstable implants or loss of femoral integrity require fracture fixation with either cerclage, strut grafts, plates or conversion to a long-stem implant.
Zhao et al investigated risk factors for intraoperative periprosthetic femoral fractures during cementless THA. A Corail stem (compared to Synergy), the anterolateral approach (compared to posterolateral), advanced age and a low Metaphyseal-Diaphyseal Index score (MDI score; Illustration B) were associated with increased risk of fracture. The MDI score was 25.89 (+/-8.11) in the fracture group versus 32.94 (+/-14.22) in the non-fracture group (p = 0.016). All fractures were treated with cerclage wire application and cementless implant insertion, followed by protected weight bearing postoperatively for 6 weeks, with no revisions required.
Illustration A depicts the Vancouver classification for perioperative periprosthetic femur fractures. Type A involves the proximal metaphysis [labelled A-C], type B involves the diaphysis [D-F]and type C fractures are distal to the stem tip and not amenable to insertion of the longest revision stem [G]. Each type is further sub-classified into type I if there is only a cortical perforation, type 2 is there is a nondisplaced crack and type 3 is there is a displaced unstable fracture pattern. Illustration B is an image from Zhao et al demonstrating radiographic measurements. The MDI is calculated by (D/F) / (G1+G2) where D = canal width 20mm above the mid-lesser trochanter line, F
= canal width 20mm below the mid-lesser trochanter line, G1 and G2 = two
cortical thicknesses at the same level as line F.
Incorrect Answers:
Answer 1: A cerclage wire should be placed prior to insertion of the stem, to prevent fracture propagation, loss of metaphyseal fit and ultimately stem subsidence.
Answer 3: Long porous-coated press-fit stems are usually reserved for periprosthetic fractures with extensive proximal bone loss (type A3) in which metaphyseal fixation is not possible, and therefore is not the best choice for this patient.
Answer 4: A long cemented stem is unnecessary for this periprosthetic fracture pattern. However, if a standard cemented stem is chosen, a cerclage wire should first be applied to reduce the fracture and prevent cement from entering the fracture site and potentially causing a nonunion.
Answer 5: Augmentation with cortical allograft is reserved for unstable periprosthetic fractures with diaphyseal bone loss (type B3) and therefore is not appropriate for this patient.

During revision total hip arthroplasty (THA), adjunctive motor-evoked potentials (MEPs) and electromyography (EMG) are utilized to monitor the sciatic and peroneal nerves. During the procedure, a conduction abnormality arises in the sciatic nerve. Which of the following actions would decrease tension on the sciatic nerve?

1) Provide traction to the leg

2) Pulsatile irrigation in the wound to remove blood clots

3) Flex the hip

4) Extend the hip

5) Extend the knee

The only answer choice that would decrease tension on the sciatic nerve is hip extension.
Satcher et al used motor-evoked potentials (MEPs) and electromyography (EMG) monitoring during 27 consecutive total hip revision cases to identify intraoperative events that caused conduction abnormalities of the sciatic and peroneal nerves. Leg positioning was the most commonly associated factor that increased sciatic nerve pressure, causing changes in monitored parameters in 4 patients. The position that caused the most conduction abnormality was hip flexion during posterior acetabular retraction in these patients.
Incorrect Answers:
1,2,3,5: During hip flexion, the nerve can impinge on the acetabular retractor. Providing traction to the leg, pulsatile irrigation, hip flexion, and knee extension would all increase sciatic nerve pressure.

In animal models, which of the following is true when comparing hydroxyapatite(HA)-coated femoral stems to identical non-HA porous-coated stems after implantation?

1) Grit-blasted stems have decreased rates of loosening

2) Hydroxyapatite-coated stems have shorter time to biologic fixation

3) Harris hip scores are higher after porous-coated stem insertion

4) Transient thigh pain is increased after hydroxyapatite-coated stem insertion

5) Porous-coated stems show increased rates of calcar atrophy

Hydroxyapatite-coated femoral stems have shown shorter times to biologic fixation in animal models, however clinical studies have yet to support their superiority to other stem designs.
Eckardt et al evaluated the influence of a proximal hydroxyapatite coating in comparison with a grit-blasted titanium surface of an anatomic hip stem in a canine model. Radiographically, animals with uncoated prostheses showed characteristic signs of loosening more frequently. Histomorphometrically, an average of 65% of the surface of HA-coated implants had bone contact, but this was present on only 14.7% of the surface of grit-blasted prostheses.
Kim et al followed 50 patients who underwent simultaneous bilateral hip arthroplasty in which a a proximally porous-coated titanium stem with hydroxyapatite coating was implanted on one side, and a proximally porous-coated titanium stem without hydroxyapatite coating was implanted on the other side. At a mean follow-up of 6.6 years, there was no difference in the rate of thigh pain, Harris hip score, or severity of calcar atrophy.
More recently, Camazzola et al performed a prospective randomized trial comparing hydroxyapatite-coated and non-hydroxyapatite-coated femoral total hip arthroplasty components in 61 patients. At 13 year follow-up, All femoral stems were well fixed on x-ray with no evidence of loosening. There was no statistically significant difference in the revision rates or in the Harris hip score between the two groups, and all femoral stems were well fixed radiographically. They concluded that there is no clinical advantage to the use of a hydroxyapatite coating on the femoral component for primary total hip arthroplasty.

A 60-year-old male tennis player undergoes a unicompartmental knee arthroplasty (UKA) shown in Figures A and B. Which of the following statements regarding this procedure is true?
1) Compared to total knee arthroplasty (TKA), UKA more closely approximates native knee kinematics

2) Patients undergoing a UKA and TKA have equivalent blood loss and pain
medication requirements

3) Compared to their TKA counterparts, UKA patients have a slower return to function

4) There is no difference in range of motion at short or long term follow-up when compared with TKA

5) Postoperative hospital stay is equivalent for UKA and TKA patients

Figures A and B depict radiographs of a unicompartmental knee arthroplasty (UKA). UKA kinematics have been shown to most closely approximate native knee kinematics.
In an in vitro cadaver study, Patil et al found that TKA significantly changed knee kinematics while the unicompartmental replacement preserved normal knee kinematics.
Fisher et al performed a retrospective study comparing the short-term outcomes of small-incision unicompartmental knee arthroplasty (UKA) with standard total knee arthroplasty (TKA) in 91 consecutive patients older than 70 years. They found: 1) Blood loss was significantly more for the TKA group, as was the need for blood transfusion. 2) Patients with unicompartmental replacements had a much quicker return of function and discontinuation of pain medication. 3) While knee scores and ROM were similar preoperatively, both were better in the unicompartmental group at each postoperative time interval. 4) Narcotic use and length of hospital stay were also significantly less for the unicompartmental group. Therefore answers 2,3,4 and 5 are false.

With regard to unicompartmental knee arthroplasty, all of the following are true EXCEPT:

1) Females have a higher revision rate

2) BMI greater than 32 is not a risk factor for early implant failure

3) Presence of osteopenia contributes to premature implant failure

4) Lateral compartment arthroplasties have higher failure rates than medial compartment arthroplasties

5) Progressive arthritis within the remaining compartments of the knee is low 5 years post-operatively

Lateral compartment arthroplasties have not been shown to have higher failure rates than medial compartment arthroplasties.
Heck et al determined survivorship and risk factors for failure in their study of 294 UKA's with an average follow-up of 6 years. No statistically significant difference in the need for revision was demonstrated between those knees in which a medial as compared with a lateral compartmental arthroplasty had been performed. Female gender had a RR of revision of 1.7 compared to men. They also found that the average patient requiring revision had a BMI of 32.6 kg/m2, and an association between obesity (wt >81kg) and revision was statistically significant. However more recent data, summarized below, has called this particular finding into question.
Pandit et al sought to determine whether potential and previously described contraindications to UKA should apply to patients with a mobile-bearing UKR. With regards to BMI, they found no significant clinical or functional outcome difference, failure rate or survival between 551 UKRs performed in ideal weight patients (44-82kg) compared to non-ideal (82-185kg).
Weale et al evaluated the radiographic changes in 50 UKA's at 5 years postop. They found no correlation between the post-op tibiofemoral angle and the extent of recurrent varus recorded at five years, and stated that changes in alignment may be indicative of minor polyethylene wear or of subsidence of the tibial component. They also found that the incidence of progressive osteoarthritis within the knee was very low after UKA.

Which of the following factors is most likely to increase the risk of hip dislocation after a total hip arthroplasty (THA)?

1) Large head-to-neck ratio

2) Use of a skirted femoral head

3) Femoral component in 15 degrees of anteversion

4) Acetabular cup in 15 degrees of anteversion

5) Acetabular cup in 50 degrees of abduction

The use of a skirted femoral head actually decreases the head to neck ratio as seen in illustration A, and leads to increased risk of hip impingement and dislocation after THAs. Illustration B shows an example of a smaller head-to-neck ratio causing decreased hip arc of motion before impingement occurs.
Barrack looked at implant design and orientation and its role in hip impingement and dislocations after THAs. Ways to minimize the risk of impingement and dislocation included avoiding the use of skirted heads, maximing head-to-neck ratio, and using chamfered acetabular liners whenever possible. With the use of computer modeling studies, he found that optimal femoral component anteversion is 10-20 degrees, while optimal acetabular component positioning is 10-20 degrees of anteversion and 45-55 degrees of abduction.
Illustration A shows how a skirted femoral head decreases the head to neck ratio. Illustration B shows an example of a smaller head-to-neck ratio causing decreased hip arc of motion before impingement occurs.

During total hip arthroplasty, which of the following techniques increases range of motion prior to impingement?

1) Using implants with a smaller femoral head

2) Using implants with a larger femoral head to neck ratio

3) Using a ultra high molecular weight polyethylene liner on the acetabulum

4) Decreasing femoral offset

5) Cementing the femoral stem

Using implants with a larger femoral head to neck ratio increases range of motion prior to impingement and improves stability.
The efficacy of using a larger size diameter femoral head to improve stability has been recognized since the early 1970s. With the larger head (larger head to neck ratio), the distance to travel before subluxation and dislocation is greater, and more ROM is allowed before the neck impinges on the shell wall and levers the head from the shell.
Amstutz et al. evaluated the outcomes of 140 THAs using size 36mm femoral heads or larger. Patients were divided into 3 groups: revision for dislocation, revision for reasons other than dislocation, and primary THA. Six cases required revision surgery for instability and all were found to have mal-oriented acetabular components. After revision, all the hips were stable and none required the use of a constrained acetabular liner. The authors concluded that large diameter femoral heads provide additional stability not only for patients with recurrent dislocations, but for any revision.
Sikes et al. compared 52 THA cases at high risk of dislocation to a matched cohort. The high risk patients were all treated with a large diameter metal on metal components while the matched group received the standard metal on poly. The large head group had 0 disclocations compared to 2 in the standard head size. Ultra high molecular weight polyethylene liners (answer #3) are used in almost all metal on plastic THA today and have greater resistance to wear than prior generation of liners. However, they have no effect on ROM and impingement. Decreased femoral offset (#4) would result in decreased tension in the abductors and could result in increased risk of dislocation, but has no effect on impingement of the femoral neck on the acetabular cup. Cemented (#5) versus press fit stems should have no effect on ROM and impingement.

Which of the following motions shows the greatest difference between a normal and ACL deficient knee?

1) Posterior femoral translation at 30° flexion

2) Posterior femoral translation at 60° flexion

3) Axial rotation in full extension

4) Axial rotation at 50° flexion

5) Varus angulation at 30 ° flexion

The study by Dennis et al, found a different axial rotation pattern in ACL deficient (ACL-D) knees compared to normal knees after 30° of knee flexion. Axial rotation was the same between the two groups in less than 30° of flexion. They also found normal and ACL deficient (ACL-D) knee patients demonstrated a similar pattern of posterior femoral translation during progressive knee flexion (0-120°). Additionally, the study showed increased variability in knee kinematic patterns observed in ACL-D knees as compared to the normal knees. Posterior femoral translation is substantially greater laterally than medially in both normal and ACL deficient patients, creating a medial pivot type of axial rotation pattern. With knee flexion, the normal tibia typically internally rotates relative to the femur and conversely, externally rotates with knee extension (i.e., screw home mechanism)

Figure A shows a ceramic head removed during a total hip revision. The component shows damage to the femoral head which was most likely caused by which of the following?
1) Third body debris

2) Chronic infection

3) Impingement of the femoral stem neck on the acetabular socket

4) Lift-off separation of the femoral head during hip range of motion

5) Insertion of the head on the femoral stem at time of initial surgery

Ceramic-on-ceramic articulation has been an attractive alternative to metal-on-polyethylene articulation because it exhibits low-friction, load-tolerant behavior with satisfactory wear characteristics. Stripe-wear as found in Figure A is a distinct type of impingement from the classic impingement of the femoral head on the acetabular socket found in episodes of instability (ie. lift-off separation) during gait.
Yammamoto et al in a retrieval study of 3 ceramic bearings and found significant stripe scars/wear at the rim of the alumina, but not at the weight bearing portion of the head. They concluded that stripe wear is caused by the femoral head making contact with the rim of the socket when the head undergoes lift-off separation from the socket.
Manaka et al found that the locations of the stripes were similar in retrieved and simulator ceramic heads. However, the stripes from the simulator were narrower than the short-term retrievals and much narrower than some longterm retrievals.

A 57-year-old man complains of knee pain that is exacerbated with weight bearing and ambulation. He underwent surgery on his knee 10 years ago following a motor vehicle collision. On physical exam he has medial and lateral joint line tenderness and no instability. Radiographs are provided in figures A and B. Conservative therapy with NSAID's and viscosupplementation is initiated. If he continues to develop further degenerative changes and needs arthroplasty what type of implant should be utilized?
1) Unicompartmental mobile bearing knee arthroplasty

2) Posterior cruciate retaining total knee arthroplasty

3) Posterior stabilized total knee arthroplasty

4) Constrained nonhinged total knee arthroplasty

5) Constrained hinged total knee arthroplasty

The radiographs and clinical presentation are consistent with a patient who has undergone a previous patellectomy and is now developing degenerative arthritis of the knee. Patellectomy is an indication to use a posterior stabilized implant. The PS implant will offer better femoral rollback and reduce the risk of potential anteroposterior instability that may occur with use a cruciate retaining prosthesis.
Paletta et al review a series of patients undergoing TKA following patellectomy and compared them to a series of TKA patients who did not have a previous history of patellectomy. Most importantly they showed better outcomes in patellectomy patients who had a posterior-stabilized implant placed at the time of TKA.
Incorrect Answers:
Answer 1: UKA is not suitable for a patient with medial and lateral pain nor a patient with previous patellectomy
Answer 2: Posterior cruciate retaining knee following patellectomy risks anteroposterior instability
Answer 4 & 5: Constrained knee options are not necessary for patellectomy as there is no loss of varus/valgus stability.

A 66-year-old male is undergoing a total knee arthroplasty using a fixed bearing posterior stabilized component. During intraoperative trialing of the components it is noted that the flexion gap is loose, and extension gap is appropriate. If this is not corrected, what postoperative complication is this patient most at risk of having?

1) Spin out of the polyethylene

2) Periprosthetic fracture

3) Posterior knee dislocation

4) Osteolysis

5) Patellar instability

A posteriorly stabilized knee has a post built into the polyethylene bearing that articulates with the box of the femoral component in flexion to act as a cam
mechanism. If the knee is too loose in flexion, it is possible for the femoral component to "jump the post", causing a posterior dislocation.
Clarke and Scuderi review flexion instability as a mode of failure in knee replacements. They describe how this is usually due to lack of adequate balance at the time of surgery. They also report that revision surgery is usually the only way to correct symptomatic flexion instability.

A 56-year-old gentleman presents to your office one year after undergoing total hip arthroplasty with the implant seen in Figure A. He is concerned about the potential complications given the recent media attention his implant has received. He is currently asymptomatic. Which of the following statements is accurate regarding his prosthesis and future care?
1) He should have bi-annual LFTs measured, as metal ions are metabolized by the liver.

2) His risk of developing cancer is dramatically increased.

3) There is no correlation between activity level and serum levels of metal ions.

4) His prosthesis design is safe in women of child-bearing age as the ions cannot be transmitted via pregnancy.

5) His prosthesis design puts him at an increased risk for dislocation.

There is currently much debate over metal-on-metal (MOM) hip replacements and the optimal management of these patients in the post-operative period.
While data is currently limited, it has been shown that activity level does not affect serum metal ion levels.
Heisel et al. in their article from JBJS 2005 present level II evidence where they looked at the relationship between patient activity and cobalt and chromium ion levels. They found no correlation between patient activity and serum levels of cobalt or chromium, or urine levels of chromium.
Incorrect answers:

DISCUSSION: The radiographs and MRI scan show a displaced tibial eminence fracture. Meyer and McKeever classified these injuries, with type 1 being a nondisplaced tibial eminence fracture; type 2 being a displaced tibial eminence fracture with a posterior hinge, and type 3 being a displaced tibial eminence fracture. Tibial eminence fractures in children are equivalent to anterior cruciate ligament tears in adults. Treatment should be anatomic reduction, which often requires an arthroscopic or open procedure, followed by fixation.
REFERENCES: Green NE, Swiontkowski MF: Skeletal Trauma in Children, ed 3. Philadelphia, PA, WB Saunders, 2003, pp xvi, 452-455, 638.
Zionts LE: Fractures around the knee in children. J Am Acad Orthop Surg 2002;10:345-355.

2010 Pediatric Orthopaedic Examination Answer Book • 79

Figure 96

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Bone marrow aspirate has been shown to have higher concentrations of IL-1ra versus both leukocyte-rich and leukocyte-poor platelet-rich plasma. IL-1 is a potent proinflammatory cytokine. IL-1ra blocks binding of IL-1 to its receptor and therefore, serves an anti-inflammatory role.

A pseudotumor is a hemophilic subperiosteal hematoma. The pseudotumor expands by repeated bleeds and increasing osmotic pressure.
There was no periosteal reaction or intralesional calcification.
The bone wall itself is not expanded as in aneurysmal bone cyst.
There is nothing in the physical examination or patient history to point to infection.

The patient has a symptomatic os trigonum caused by impingement that occurs with maximal plantar flexion of the ankle in the demi-pointe or full-pointe position. Patients frequently report posterolateral pain localized behind the lateral malleolus that may be misinterpreted as a disorder of the peroneal tendon. Pain with passive plantar flexion (the plantar flexion sign) indicates posterior impingement, not a problem with the peroneal tendon. The symptoms are not characteristic of a stress fracture, nor do the radiographs show a stress fracture or an osteochondritis dissecans lesion. The os trigonum is modest in its dimensions. The incidence or magnitude of symptoms does not correlate with the size of the fragment. Large fragments may be asymptomatic, while small lesions may create significant symptoms.
REFERENCES: Marotta JJ, Micheli LJ: Os trigonum impingement in dancers. Am J Sports Med 1992;20:533-536.
Hamilton WG: Foot and ankle injuries in dancers, in Mann RA, Coughlin MJ (eds): Surgery of the Foot and Ankle, ed 6. St Louis, MO, CV Mosby, 1993, pp 1241-1276.

The histologic features of multiple myeloma are distinctive for this lesion. The plasma cells are round or oval and have an eccentric nucleus and prominent nucleolus. These characteristics and a clear area next to the eccentric nucleus representing the prominent Golgi center are pathognomonic for plasma cells. Lymphoma is in the differential diagnosis; the most frequent types that occur in bone are large cell or mixed small and large cell types. The histologic appearance of the specimen is not consistent with the other choices.
REFERENCE: Dorfman HD, Bodgan C: Immunohematopoietic tumors, in Dorfman HD, Bogdan C (eds): Bone Tumors. St Louis, MO, Mosby, 1998, Chapter 12.

Based on the choices above, the most important predictor of wound healing is the serum albumin level.
Wound healing is based on several factors, which include the vascular status, the immune status, and the nutritional status of the patient. Some important clinical findings include an ankle brachial index (ABI) > 0.45, a total lymphocyte count > 1500/mm3 and a serum albumin > 3.0 g/dL.
Kay et al. discuss the importance of the nutritional status in wound healing after lower extremity amputation procedures. They found eleven of 25 patients who were malnourished sustained either local or systemic complications postoperatively. They recommend that patients should undergo nutritional screening prior to elective lower extremity amputations, to help optimize their wound healing.
Incorrect Answers
Answer 2: While total protein is a marker of nutritional status, it is not as sensitive as the serum albumin for wound healing potential.
Answers 3, 4, 5: Calcium levels, C-reactive protein and ESR are not markers of wound healing

The patient is presenting with a septic nonunion following an open tibial shaft fracture. Of the given answer choices, the timely administration of antibiotics, ideally within 3 hours of injury, is associated with decreased wound infection
rates and subsequent septic nonunion.
Tibial shaft fractures are the most common long bone fracture, with up to 24% of fractures presenting as an open injury. Appropriate initial management of these injuries is crucial to optimizing outcomes, as they are often fraught with high wound complication and infection rates. Literature has demonstrated that the prompt delivery of appropriate IV antibiotic coverage is one of the most important factors in minimizing wound infection rates and subsequent septic nonunions. The risk of infection is decreased substantially when antibiotics are started within three hours of the injury, compared to later treatment. Ideal coverage includes 1st generation cephalosporins for grades I and II, sometimes with the addition of gentamicin for grade III injuries. During the evaluation for septic nonunion, elevated CRP and ESR levels are suggestive of an infection.
Babhulkar et al. retrospectively reviewed 113 patients with long bone fracture nonunions of various etiologies, including 16 tibial shaft nonunions. The authors reported that the initial treatment of these injuries consisted of six intramedullary nails, four platings, two external fixators, and one plaster cast, which resulted in nine aseptic and four septic nonunions. Following appropriate treatment, all patients eventually attained fracture union, with 16% of tibial nonunions resulting in an acceptable malunion, 13% resulting in limb shortening, and two patients with a persistent septic nonunion that was successfully treated with Ilizarov frame. The authors concluded that successful treatment of long bone fracture nonunions requires consideration of the pathophysiology of the nonunion and appropriately addressing stability, infection control, and provision of an osteogenic environment.
Mundi et al. reviewed the management of open tibial shaft fractures. The authors supported the use of either bacitracin or castile soap irrigation, with no difference in infection outcomes, while low-pressure irrigation delivery was associated with lower reoperation rates due to infections, nonunion, and wound healing problems. They also supported that definitive closure of wounds within seven days of the initial injury was associated with a reduced rate of complications, including infection. The authors concluded that prompt administration of appropriate antibiotic prophylaxis was the single-most important determinant in minimizing wound infections.
The investigators of the SPRINT (The Study to Prospectively Evaluate Reamed Intramedullary Nails in Patients with Tibial Fractures) study performed a multicenter blinded randomized trial of 1319 patients treated with either reamed or unreamed intramedullary nailing for tibial shaft fractures. In the 406 patients with open fractures, of which 137 were grade III, there was no
treatment benefit between reamed and unreamed nails. However, the investigators reported a significantly increased union rate with reamed intramedullary nails for closed tibial shaft fractures. They concluded that reamed intramedullary nailing appears to have a treatment benefit only for closed tibial shaft fractures.
Figures A and B are the AP and lateral radiographs of the right tibia and fibula demonstrating a comminuted fracture of the tibia with minimal healing after intramedullary nail fixation.
Incorrect answers:
Answer 1: Definitive wound coverage should be performed within seven days of the injury in wounds requiring delayed closure in order to minimize the risk of infection. Wound coverage for the patient in this scenario was delayed < 7 days.
Answer 2: Union rates are comparable between unreamed and reamed intramedullary nailing for open tibial shaft fractures.
Answer 4: The patient has a normal vitamin D level, and an elevated CRP suggests an infectious rather than a nutritional etiology of the nonunion. Answer 5: Low-pressure irrigation is associated with lower reoperation rates due to infection, wound complications, and nonunion.

- increased dural tear risk.