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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 55 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 1081

Topic: 3. Adult Reconstruction (Hip & Knee)

A total knee arthroplasty is recommended to a mentally competent 68-year-old woman who has disabling knee pain caused by degenerative arthritis. Her son has researched the procedure on the internet and prefers the Acme Female Knee for his mother. You have designed the Axis Woman's Knee, for which you receive royalties, and use it exclusively. Which of the following ethical principles takes precedence in guiding her treatment?

. Informed consent
. Patient autonomy
. Fiduciary responsibility
. Physician paternalism
. Justice

Correct Answer & Explanation

. Informed consent

Explanation

Informed consent incorporates a number of ethical principles relevant to this case. The fundamentals of medical ethics include nonmaleficence, beneficence, autonomy, and justice. The patient is competent and capable of exercising her autonomy in choosing the Acme Female Knee. She also depends on her physician's paternalism and knowledge in looking out for her best interests, which in his opinion, may be use of the Axis Woman's Knee. The physician has a fiduciary responsibility to inform the patient that he has a financial interest in the implant system he recommends. A thorough informed consent will respect the patient's autonomy, explain the rationale for the physician's recommendation, and notify the patient that there may be a perceived conflict of interest. The ethical principle of justice has no relevance in this case.

Question 1082

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 25 shows the radiograph of an 84-year-old woman who has pain and is unable to extend her knee. History reveals that she underwent total knee arthroplasty 8 years ago. Aspiration and studies for infection are negative. During revision surgery, management of the tibial bone loss should consist of

. reconstruction with a metal augmented revision tibial implant.
. reconstruction with a hinged prosthesis.
. reconstruction with a structural allograft.
. reconstruction with iliac crest bone graft.
. filling the defect with cement.

Correct Answer & Explanation

. reconstruction with a metal augmented revision tibial implant.

Explanation

DISCUSSION: Massive bone loss encountered in revision total knee arthroplasty remains a significant challenge.  Recent reports have shown high success rates using structural allograft to reconstruct large structural bone defects.  A hinged prosthesis is not required in this setting.  In this patient, a large amount of posterior cortex has been lost, making the area too large to fill with cement or iliac crest bone graft.  Because of her age, the treatment of choice is a revision tibial implant and metal augments.  Structural allograft would be suitable in a younger patient.REFERENCES: Mow CS, Wiedel JD: Structural allografting in revision total knee arthroplasty.  J Arthroplasty 1996;11:235-241.Engh GA, Herzwurm PJ, Parks NL: Treatment of major defects of bone with bulk allografts and stemmed components during total knee arthroplasty.  J Bone Joint Surg Am 1997;79:1030-1039.Clatworthy MG, Ballance J, Brick GW, et al: The use of structural allograft for uncontained defects in revision total knee arthroplasty: A minimum five-year review.  J Bone Joint Surg Am 2001;83:404-411.

Question 1083

Topic: 3. Adult Reconstruction (Hip & Knee)

Metal-on-metal articulation has been reintroduced because of concern about polyethylene wear. This type of articulation is considered favorable because

. metal particles are inert.
. metal particles are larger than polyethylene particles.
. the surfaces can now be fabricated with low carbon, machined cobalt-chromium.
. less than 0.6 mm 3 of metallic debris are generated per year.
. electrochemical problems of the articulation have now been solved through passivation.

Correct Answer & Explanation

. metal particles are inert.

Explanation

DISCUSSION: The improvements in metal-on-metal bearing surfaces come from the nonlinear wear rate and smaller particle size of the high carbon wrought material.  Extremely low rates of wear have been demonstrated with high carbon metal-on-metal implants.  There is no significant electrochemical effect of mating two like materials in vivo.REFERENCE: Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 25-34.

Question 1084

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 13 shows the radiographs of a 56-year-old woman who has pain and varus knee deformity after undergoing total knee arthroplasty 8 years ago. Aspiration and studies for infection are negative. During revision surgery, management of the tibial bone loss is best achieved by

. a custom tibial implant.
. a hinged prosthesis.
. reconstruction with structural allograft.
. reconstruction with iliac crest bone graft.
. filling the defect with cement.

Correct Answer & Explanation

. a custom tibial implant.

Explanation

DISCUSSION: Massive bone loss encountered in revision total knee arthroplasty remains a significant challenge.  Recent reports have shown high success rates using structural allograft to reconstruct massive bone defects.  Custom and hinged prostheses in this setting are no longer favored.  The defect shown is segmental and is too large to be filled with cement or iliac crest bone graft.REFERENCES: Mow CS, Wiedel JD: Structural allografting in revision total knee arthroplasty. J Arthroplasty 1996;11:235-241.Engh GA, Herzwurm PJ, Parks NL: Treatment of major defects of bone with bulk allografts and stemmed components during total knee arthroplasty. J Bone Joint Surg Am 1997;79:1030-1039.Clatworthy MG, Ballance J, Brick GW, Chandler HP, Gross AE: The use of structural allograft for uncontained defects in revision total knee arthroplasty: A minimum five-year review. J Bone Joint Surg Am 2001;83:404-411.

Question 1085

Topic: 3. Adult Reconstruction (Hip & Knee)

An obese patient undergoing total knee arthroplasty is at increased risk for which of the following complications?

. Wound complication
. Infection
. Lower knee score
. Aseptic loosening
. Patellar subluxation

Correct Answer & Explanation

. Wound complication

Explanation

DISCUSSION: The rate of wound complications is significantly increased after total knee arthroplasty in obese patients.  Knee scores and the rate of aseptic loosening or patellar subluxation do not appear to be significantly altered.REFERENCES: Winiarsky R, Barth P, Lotke P: Total knee arthroplasty in morbidly obese patients.  J Bone Joint Surg Am 1998;80:1770-1774.Stern SH, Insall JN: Total knee arthroplasty in obese patients.  J Bone Joint Surg Am 1990;72:1400-1404.Griffin FM, Scuderi GR, Insall JN, Colizza W: Total knee arthroplasty in patients who were obese with 10 years follow-up.  Clin Orthop 1998;356:28-33.

Question 1086

Topic: 3. Adult Reconstruction (Hip & Knee)
  • Almost 50% of all long-term complications following total knee arthroplasty are due to
. Early and late infection
. Periprosthetic fracture of the femur
. Failure of the patellofemoral and extensor mechanisms
. Aseptic loosening of cementing tibial components
. Asceptic loosening of cemented femoral components

Correct Answer & Explanation

. Early and late infection

Explanation

50% of failures are due to the patellofemoral component and extensor mechanisms. These include failure of the metal backed components, patellofemoral instability, component loosening, patellar fracture, osteonecrosis,and failure of the extensor mechanism. The incidence of the other choices are far less.

Question 1087

Topic: 3. Adult Reconstruction (Hip & Knee)

A 42-year-old man undergoes right total hip arthroplasty for hip dysplasia. Postoperatively, he has a significant limb-length increase with a foot drop. A preoperative radiograph is shown in Figure 19. Which of the following should have been considered preoperatively to avoid this complication?

. Medialization of the acetabular component
. Use of a modular femoral implant
. Anterolateral approach to the hip
. Femoral shortening
. Electromyography

Correct Answer & Explanation

. Medialization of the acetabular component

Explanation

DISCUSSION: In a patient with bilateral hip dysplasia, there are significant technical challenges that need to be addressed to ensure a successful total hip arthroplasty.  Restoring the center of the hip may cause significant lengthening and require femoral shortening.  Lengthening of greater than 4 cm can lead to sciatic nerve palsy that will present clinically as a foot drop.  A high hip center can be used when there is inadequate bone stock in the acetabulum to achieve adequate host bone coverage.  A modular femoral implant may be used for a dysplastic hip with significant rotational deformity.  Although an anterolateral approach to the hip may decrease the incidence of sciatic nerve palsy during the exposure, it will not be helpful when there is more than 4 cm of limb lengthening.REFERENCES: Schmalzried TP, Amstutz HC, Dorey FJ: Nerve palsy associated with total hip replacement: Risk factors and prognosis.  J Bone Joint Surg Am 1991;73:1074-1080.Papagelopoulos PJ, Trousdale RT, Lewallen DG: Total hip arthroplasty with femoral osteotomy for proximal femoral deformity.  Clin Orthop 1996;332:151-162.Huo MH, Zatorski LE, Keggi KJ: Oblique femoral osteotomy in cementless total hip arthroplasty: Prospective consecutive series with a 3-year minimum follow-up period.J Arthroplasty 1995;10:319-327.

Question 1088

Topic: 3. Adult Reconstruction (Hip & Knee)

A 58-year-old man has anterior knee pain after undergoing total knee arthroplasty for osteoarthritis 2 years ago. He denies any history of trauma. A Merchant view is shown in Figure 20. What is the most likely cause of his pain?

. External rotation of the femoral component
. Overstuffing of the patellofemoral joint
. Less than 12 mm of bony patella remaining after resection
. Lateral retinacular release
. Use of a cemented patellar component

Correct Answer & Explanation

. External rotation of the femoral component

Explanation

DISCUSSION: The patient has a patellar stress fracture after resurfacing in a total knee arthroplasty.  Several studies have shown that over-resection of the patella to less than 12 to 15 mm increases anterior patellar surface strains to a point where the risk of fracture is increased.  Increasing the patellar thickness, positioning of the femoral component, lateral releases, and component types have not been clearly associated with increased fracture risk.REFERENCES: Reuben JD, McDonald CL, Woodard PL, Hennington LJ: Effect of patella thickness on patella strain following total knee arthroplasty. J Arthroplasty 1991;6:251-258.Hsu HC, Luo ZP, Rand JA, An KN: Influence of patellar thickness on patellar tracking and patellofemoral contact characteristics after total knee arthroplasty. J Arthroplasty 1996;11:69-80.Greenfield MA, Insall JN, Case GC, Kelly MA: Instrumentation of the patellar osteotomy in total knee arthroplasty: The relationship of patellar thickness and lateral retinacular release. Am J Knee Surg 1996;9:129-131.

Question 1089

Topic: 3. Adult Reconstruction (Hip & Knee)

After completion of bone cuts and ligament balancing of a severe valgus knee during primary total knee arthroplasty, there is a 5-mm increased medial gap that cannot be corrected. In this scenario, what is the most appropriate level of constraint?

. Cruciate-retaining
. Posterior stabilized
. Varus-valgus constrained
. Rotating hinge

Correct Answer & Explanation

. Cruciate-retaining

Explanation

DISCUSSIONCruciate-retaining implants are typically used in the presence of a functioning posterior cruciate ligament (PCL). A posterior stabilized insert improves anteroposterior stability in the absence of a PCL but does not account for imbalance of the collateral ligaments. Anuncorrectable laxity medially indicates insufficiency of the medial collateral ligament (MCL), which is best treated with a varus-valgus constrained component. A rotating hinge is generally reserved for complete absence of the MCL or both collateral ligaments.Change of IV antibiotics and splintingArthroscopic irrigation and debridementCT-guided needle aspirationOpen debridementDISCUSSIONIn an acutely febrile child with bone pain and elevated acute-phase reactants, osteomyelitis is suspected. Blood cultures will yield the offending organism in 30% to 60% of patients and are the most appropriate next step. Knee aspiration in the absence of an effusion likely will not be helpful. Although a bone scan may show an osteomyelitic focus, an indium-labeled WBC scan is unnecessarily complex and costly in this case. Pelvic radiographs would add little to the unremarkable femur films.Initiating IV antibiotics after obtaining blood cultures is appropriate, even in the presence of an MRI with normal findings. Observation or discharge may be considered, but suspicion for infection should be strong in this clinical situation and delay is not warranted. A CT scan of the knee in the setting of normal MRI findings will not be helpful.Most hematogenous osteomyelitis cases among children are attributable to S. aureus. In many areas of the country, MRSA is endemic, and initial coverage for resistance is appropriate. The other listed organisms would rarely be seen in this scenario.The MR images show early abscess formation in the distal medial femoral metaphysis. Because the formation developed during antibiotic treatment, surgical drainage (rather than a change of antibiotic) is appropriate. Arthroscopy is not helpful because this is not an intra-articular process. Although aspiration prior to surgical debridement could be considered, the organism has already been identified from the blood culture, and CT guidance is not needed to locate this large abscess in such an accessible area.

Question 1090

Topic: 3. Adult Reconstruction (Hip & Knee)

During total knee arthroplasty using a posterior cruciate-retaining design, excessive tightness in flexion is noted, while the extension gap is felt to be balanced. Which of the following actions will effectively balance the knee?

. Resect more distal femur.
. Resect more anterior tibia.
. Use a larger femoral component.
. Use a smaller polyethylene insert.
. Recess the posterior cruciate ligament.

Correct Answer & Explanation

. Resect more distal femur.

Explanation

DISCUSSION: Excessive flexion gap tightness can be addressed with a variety of techniques; including: (a) recess and release the posterior cruciate ligament; (b) resect a posterior slope in the tibia; (c) avoid an oversized femoral component that moves the posterior condyles more distally; (d) resect more posterior femoral condyle and use a smaller femoral component placed more anteriorly; and (e) release the tight posterior capsule and balance the collateral ligaments.REFERENCE: Ayers DC, Dennis DA, Johanson NA, Pelligrini VD: Common complications of total knee arthroplasty. J Bone Joint Surg Am 1997;79:278-311.

Question 1091

Topic: 3. Adult Reconstruction (Hip & Knee)

An 82-year-old osteoporotic woman undergoes total hip arthroplasty for osteoarthritis. During implant trialing, a crack is heard. Intraoperative fluoroscopy reveals a long, spiral fracture of the distal femur. The fracture is reduced and fixed with an anatomic locking plate. The rest of the total hip arthroplasty proceeds uneventfully. Following surgery the surgeon has a meeting with the family and apologizes and provides full disclosure, accepts responsibility, provides a detailed explanation as to what happened, and gives reassurance that steps will be taken to prevent recurrences. This communication approach will most likely

. Lead to lower patient satisfaction rates
. Lead to higher patient satisfaction rates
. Lead to higher likelihood the patient will take legal action against surgeon
. Lead to higher likelihood the patient will change physicians
. Prevent any legal action

Correct Answer & Explanation

. Lead to lower patient satisfaction rates

Explanation

The surgeon has provided all the elements of good communication with the patient and family. His actions will lead to improved patient satisfaction, compared to nondisclosure and attempting to push or shirk responsibility.In the event of a medical error or adverse event, effective communication with the patient and family is necessary. Effective communication should comprise: an apology, full disclosure (an explanation of what happened), accepting responsibility, and corrective steps that will be taken to prevent recurrence.While accepting responsibility is integral to the explanation process, it is different from accepting blame.Mazor et al. found patients would more likely change physicians and seek legal advice in situations with a life-threatening outcome where physicians chose nondisclosure. They recommend full disclosure, acceptance of responsibility, an apology, detailed explanations, and assurances that steps will be taken to prevent recurrences will result in positive outcomes in terms of patient satisfaction, trust, and emotional response.MacDonald et al. addressed medical errors in an editorial. Besides full disclosure, they feel that an apology is necessary. This includes an acknowledgement of the event and one’s role in the event, and a genuine expression of regret. Apology laws exist to to reduce concerns about legal implications of disclosure and apology.Incorrect Answers:

Question 1092

Topic: Total Knee Arthroplasty (TKA)

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?

. Aspiration of joint fluid to obtain a cell count
. Revision of the UKA using primary total knee arthroplasty (TKA) components
. Revision of the UKA using a revision TKA with augments
. Procurement of the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level

Correct Answer & Explanation

. Aspiration of joint fluid to obtain a cell count

Explanation

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 elevatedweight. 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  theaspiration and proceed to a revision TKA with possible augments on standby.

Question 1093

Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following design features of a femoral component used in a total knee arthroplasty best minimizes the patellar component contact stresses?
. Shallow, flat anatomic femoral trochlear groove
. Deep, curved anatomic femoral trochlear groove
. Narrow femoral trochlear groove
. Universal trochlear groove (same for right and left)
. Thickened anterior flange

Correct Answer & Explanation

. Deep, curved anatomic femoral trochlear groove

Explanation

DISCUSSION: Several studies have shown that design of the femoral component, especially the trochlear groove portion, largely influences patellar tracking and patellofemoral contact stresses. A deep, curved anatomic femoral trochlear groove has been shown to have the lowest contact stresses.

Question 1094

Topic: 3. Adult Reconstruction (Hip & Knee)

Two weeks after undergoing total knee arthroplasty, a 68-year-old woman experiences moderate, yet worsening, knee pain. Upon examination, she can walk with a cane but she has swelling with mild reactive erythema. She has a well-healed incision with no drainage. A review of her medications reveals the she has been taking warfarin and has an international normalized ratio (INR) of 4.0. Her erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level are slightly elevated, and radiographs are unremarkable other than for effusion. What is the most likely diagnosis?

. Deep periprosthetic joint infection
. Deep vein thrombosis
. Hemarthrosis
. Extensor mechanism disruption

Correct Answer & Explanation

. Deep periprosthetic joint infection

Explanation

DISCUSSIONThis patient likely has a hemarthrosis related to INR elevation. The slight elevations in ESR and CRP are likely attributable to the nature of the surgery itself rather than an infection, and the mild reactive erythema is likely attributable to the hemarthrosis.

Question 1095

Topic: 3. Adult Reconstruction (Hip & Knee)
The optimal method with which to diagnose component malrotation in total knee arthroplasty (TKA) is:
. clinical assessment of foot position and patellar tracking.
. radiographic skyline view of the patella.
. CT scan with metal artifact suppression.
. MR imaging with metal artifact reduction sequences.

Correct Answer & Explanation

. CT scan with metal artifact suppression.

Explanation

DISCUSSION: The epicondylar axis and tibial tubercle can be used as references on CT scans to quantitatively measure rotational alignment of the femoral and tibial components. This technique has been used to determine whether rotational malalignment is present and whether revision of 1 or both components may be indicated. Although clinical assessment is useful, malrotation can occur as a result of deformities unrelated to the arthroplasty. Similarly, an isolated radiographic skyline view of the patella may indicate a problem with patellar maltracking, but cannot quantitatively assess malrotation of the components.

Question 1096

Topic: 3. Adult Reconstruction (Hip & Knee)

An operating room intervention that should be undertaken by anesthesia staff during the cementing of a femoral stem is to

. decrease the fraction of inspired oxygen (FiO2).
. decrease the intravenous (IV) fluid rate.
. have phenylephrine on standby.
. redose epidural anesthesia.

Correct Answer & Explanation

. decrease the fraction of inspired oxygen (FiO2).

Explanation

DISCUSSIONYoung age is a risk factor for early failure of cementless femoral components. Surgeons could consider cementing for patients older than 80 years of age. The Dorr classification has been shown to favor a cemented femoral stem in Dorr type C bone. Dorr type B bone can potentially sustain a proximally porous ingrowth stem. Osteoporosis is a risk factor for early failure of cementless femoral components.Earlier designs for cemented femoral stems used microtexture to interlock the stem into the cement mantle. If these stems became loose, they would abrade the cement and loosen the stem further. Successful cemented femoral components are polished and have smooth edges with tapered bodies. Collars do not add to the design of femoral stems.Patients are at risk for hypotension during the femoral pressurization process. With that in mind, the surgeon should make sure the anesthesiologist is ready to respond to hypotension. The FiO2 should be increased. The IV fluid rate also should be increased, and the anesthesiologist should be prepared with phenylephrine to support the patient’s blood pressure if he or she becomes hypotensive.

Question 1097

Topic: 3. Adult Reconstruction (Hip & Knee)
The need for postoperative allogeneic blood transfusions after total hip arthroplasty has been shown to be reduced when using
. cementless fixation.
. suction drains.
. general anesthesia.
. preoperative erythropoietin injections.
. low-molecular-weight heparin.

Correct Answer & Explanation

. preoperative erythropoietin injections.

Explanation

In a prospective study, 216 patients were randomized into three groups consisting of low-dose preoperative erythropoietin, high-dose preoperative erythropoietin, and placebo control. All patients were treated for 4 weeks prior to total hip arthroplasty. Both the low- and high-dose erythropoietin groups had a significantly lower rate of blood transfusions (p < 0.001) after surgery.

Question 1098

Topic: 3. Adult Reconstruction (Hip & Knee)
When do most symptomatic thromboembolic events occur after total joint arthroplasty?
. On the day of surgery
. Within the first week after surgery
. Between 1 week and 6 weeks after surgery
. More than 3 months after surgery

Correct Answer & Explanation

. Between 1 week and 6 weeks after surgery

Explanation

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 1099

Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following procedures is considered most appropriate in patients with rheumatoid arthritis?
. Hip arthrodesis
. Osteotomy of the hip
. Core decompression of the hip
. Synovectomy of the knee
. Unicondylar knee arthroplasty

Correct Answer & Explanation

. Synovectomy of the knee

Explanation

Synovectomy of the knee prior to loss of articular cartilage has been shown to consistently relieve pain in patients with rheumatoid arthritis. Partial knee replacement will not arrest the process of joint destruction. Osteotomy of the hip has not been found to be a successful procedure in patients with rheumatoid arthritis. Hip arthrodesis should not be considered because of the multiarticular involvement in patients with rheumatoid arthritis. Core decompression of the hip has not been shown to save the femoral head because the necrosis appears to occur simultaneously with the inflammatory joint process.

Question 1100

Topic: Total Hip Arthroplasty (THA)
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?
. Revision of the acetabular implant to a constrained bearing with modular exchange of the femoral head and neck
. Revision of the acetabular and femoral implants
. Retention of the acetabular implant with modular exchange of the femoral head and neck
. Revision of the femoral component alone with a new ceramic head

Correct Answer & Explanation

. Revision of the acetabular and femoral implants

Explanation

The modular femoral stem has fractured. Revision of the acetabular and femoral implants is appropriate because of the potential for damage to the existing cup from metal debris and femoral implant contact. Retention of the femoral stem is not recommended because of the concern for failure with only a neck exchange. 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.

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