Orthopedic Hip & Knee 2026 MCQs: Board Review Part 2

Question 1

A 59-year-old woman who underwent a total hip arthroplasty 5 years ago now has recurrent dislocation following bariatric surgery and a weight loss of 200 lb. An attempt at converting to a larger head size and trochanteric advancement has failed. Her components are well aligned. What is the best course of action?

Explanation

When a patient has well-aligned components and soft-tissue tensioning with a larger femoral head and trochanteric advancement has failed, options are limited. The use of a constrained acetabular liner is the best option in this situation. Goetz and associates and Shrader and associates have demonstrated good results with these implants. Shrader used this device on 109 patients with recurrent instability with a successful outcome in all but 2 patients. Resection arthroplasty is a salvage situation and is not the best option at the present time. A hip abduction brace does not address the soft-tissue laxity. Conversion to a bipolar arthroplasty, although possibly minimizing the incidence of dislocation, will lead to groin pain and migration of the component with diminished functional results. Goetz DD, Capello WN, Callaghan JJ, et al: Salvage of recurrently dislocating hip prosthesis with use of a constrained acetabular component: A retrospective analysis of fifty-six cases. J Bone Joint Surg Am 1998;80:502-509. Shrader MW, Parvizi J, Lewallen DG: The use of constrained acetabular component to treat instability after total hip arthroplasty. J Bone Joint Surg Am 2003;85:2179-2183.

Question 2

Figure 15 shows the radiograph of an active 60-year-old woman. Which of the following variables is considered the strongest contraindication to a unicompartmental knee arthroplasty in this patient?

Explanation

Unicompartmental arthroplasty of the knee for single compartment arthrosis has recently become more popular. Contraindications to unicompartmental knee arthroplasty include fixed varus or valgus deformity of more than 5 degrees, restricted range of motion, fixed flexion contracture, joint subluxation of 5 mm or greater, and arthrosis of the opposite and/or patellofemoral compartment. Cossey AJ, Spriggins AJ: The use of computer-assisted surgical navigation to prevent malalignment in unicompartmental knee arthroplasty. J Arthroplasty 2005;20:29-34. Iorio R, Healy WL: Unicompartmental arthritis of the knee. J Bone Joint Surg Am 2003;85:1351-1364.

Question 3

Figure 16 shows the radiograph of an otherwise healthy 62-year-old woman who fell. Management should consist of

Explanation

The radiograph reveals that the femoral component is grossly loose as evidenced by disruption of the cement column; therefore, retention of the original components will not yield a successful outcome. A cementless revision is the procedure of choice. A strut graft and/or plate may be added at the surgeon's discretion. A resection arthroplasty would only be considered in a nonambulatory patient. Cemented fixation of the revision component would be problematic given the numerous fracture fragments and the inability to contain the cement. Springer BD, Berry DJ, Lewallen DG: Treatment of periprosthetic fractures following total hip arthroplasty with femoral component revision. J Bone Joint Surg Am 2003;85:2156-2162.

Question 4

Which of the following is the strongest contraindication to unicompartmental knee arthroplasty (UKA)?

Explanation

UKA prostheses cannot substitute for an absent ACL, and if arthroplasty is indicated, these patients should receive a total knee arthroplasty rather than a UKA. Age is not an absolute contraindication, and the procedure has been advocated for young patients as well as older patients if they meet the appropriate indications for an arthroplasty. Varus deformities of the mechanical axis of up to 10 degrees generally are not a contraindication to unicompartmental arthroplasty, as long as the knee can be properly balanced at the time of surgery. Modest chondromalacia of the patellofemoral joint, especially if asymptomatic, is not a contraindication to UKA. Lotke PA (ed): Knee Arthroplasty: Master Techniques in Orthopaedic Surgery. New York, NY, Raven Press, 1995, pp 275-293. Insall JN, Windsor RE, Scott WN, et al (eds): Surgery of the Knee, ed 2. New York, NY, Churchill Livingstone, 1993, pp 805-814.

Question 5

Figure 17 shows the AP radiograph of a 75-year-old man with right hip pain. The femoral component is loose. The mechanism of loosening is most likely secondary to

Explanation

The femoral construct shown in the radiograph has failed to produce ingrowth of the stem. The stem has subsided and rotated. Impingement of the trochanter did not occur until after the stem subsided. There is no evidence of osteolysis or third-body wear debris from the cerclage wire. A larger femoral stem needs to be implanted to achieve rigid fixation. Pelicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 217-238.

Question 6

A 75-year-old woman undergoes hybrid total hip arthroplasty for osteoarthritis. A postoperative radiograph obtained in the recovery room is shown in Figure 18. Treatment should now consist of

Explanation

Intraoperative femoral fractures can often be avoided by careful preoperative planning to optimize implant design and size. Most fractures occur during implantation of a cementless implant; many can be avoided by careful femoral preparation and component implantation, with particular caution in osteopenic bone. Intraoperative femoral fractures are managed according to fracture severity. Minor cracks that do not affect stability or femoral integrity can often be managed intraoperatively with cerclage fixation, limited weight bearing, and observation. Femoral fractures that compromise implant stability or femoral integrity require fracture fixation with cerclage wires, strut grafts, or plates and may require conversion to a long stem implant. This patient's fracture is nondisplaced and the implant is well seated; therefore, limited weight bearing is considered appropriate management. Lee SR, Bostrom MP: Periprosthetic fractures of the femur after total hip arthroplasty. Instr Course Lect 2004;53:111-118. Kelley SS: Periprosthetic femoral fractures. J Am Acad Orthop Surg 1994;2:164-172.

Question 7

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?

Explanation

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. 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.

Question 8

A 58-year-old man reports a 2-month onset of groin pain with no history of trauma. Examination reveals that range of motion of the hip is mildly restricted, and he has pain with both weight bearing and at rest. An MRI scan is shown in Figure 20. Treatment should consist of

Explanation

The MRI findings show highly increased signal through the entire femoral head and neck on STIR imaging, diagnostic of transient osteoporosis of the femoral head. This disease entity can be seen in middle-aged men, and should be treated nonsurgically. The natural history is that of self-resolution. Guerra JJ, Steinberg ME: Distinguishing transient osteoporosis from avascular necrosis of the hip. J Bone Joint Surg Am 1995;77:616-624.

Question 9

Figure 21 shows the radiograph of a 32-year-old patient with right hip pain that has failed to respond to nonsurgical management. What is the most appropriate surgical treatment at this time?

Explanation

The radiograph reveals developmental dysplasia of both hips. The patient has classic anterolateral undercoverage of the femoral head on the right side as demonstrated by a high acetabular index (measured at 27 degrees). Anterior undercoverage can be determined by drawing the marking for the anterior wall that fails to overlap the femoral head in this patient. Currently in North America, the most accepted surgical management for symptomatic dysplasia of the hip with good joint space is a Bernese (Ganz) periacetabular osteotomy. Surgical dislocation of the hip and femoroacetabular osteoplasty may be considered for patients with symptomatic femoroacetabular impingement of the hip. Ganz R, Klaue K, Vinh TS, et al: A new periacetabular osteotomy for the treatment of hip dysplasias: Technique and preliminary results. Clin Orthop 1988;232:26-36.

Question 10

A patient reports pain in the hip with functional positioning. With the patient supine, pain in which of the following positions would be typical for femoral acetabular impingement?

Explanation

Patients with dysplasia often have a hypertrophic labrum. Abnormal contact between the femoral neck and the acetabular rim leads to labral injury, especially in the anterior-superior acetabular zone. Typically, young patients with the condition report pain with activity or long periods of sitting or driving. The hips often have limited motion, in particular in internal rotation and flexion. Forceful adduction with the maneuver causes pain. Vaccaro AR (ed): Orthopaedic Knowledge Update 8. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2005, pp 411-424. Beck M, Leunig M, Parvizi J, et al: Anterior femoroacetabular impingement: Part II. Midterm results of surgical treatment. Clin Orthop 2004;418:67-73.

Question 11

A patient who underwent a total knee arthroplasty for osteoarthritis 18 months ago now reports the sudden development of pain in the ipsilateral knee. Radiographs and examination of the knee are unremarkable. Aspiration of the synovial fluid 3 days later reveals a WBC count of 1,500/mm3. The cells consist of 30% neutrophils and 70% monocytes. Culture results will not be available for several days. The patient has not been on antibiotics prior to this point. Based on these findings, what is the most appropriate management?

Explanation

Synovial fluid analysis is a very sensitive tool for detecting infection in total knee arthroplasties. Several studies have demonstrated that an absolute leukocyte count in the synovial fluid of less than 1,700 to 2,500/mm3 is an accurate predictor of absence of infection. Similarly, a differential cell count of the WBCs demonstrating less than 50% to 60% neutrophils is an accurate predictor of absence of infection. If both parameters are normal, it is unlikely that the patient has an infection. The three surgical options are contraindicated based on the normal examination findings and laboratory parameters. Similarly, antibiotics should be avoided. The work-up should include tests to evaluate noninfectious sources of knee pain and sources of referred knee pain. Trampuz A, Hanssen AD, Osmon DR, et al: Synovial fluid leukocyte count and differential for the diagnosis of prosthetic knee infection. Am J Med 2004;117:556-562. Mason JB, Fehring TK, Odum SM, et al: The value of white blood cell counts before revision total knee arthroplasty. J Arthroplasty 2003;18:1038-1043.

Question 12

A 38-year-old man who is an avid tennis player has had persistent pain over the medial aspect of his knee for the past 6 years. He notes that the pain occurs on a daily basis with any significant activity. Nonsteroidal anti-inflammatory drugs have failed to provide relief. Radiographs are shown in Figures 22a and 22b. What is the best course of action?

Explanation

22b In a relatively young patient who is an avid tennis player, the treatment of choice is a joint preserving procedure. The radiographs reveal varus alignment with loading of the medial compartment. After all nonsurgical management options have been used, the best treatment option is a medial opening wedge osteotomy. A lateral closing wedge osteotomy of the proximal tibia is also a reasonable option, but it is not one of the choices. A unicompartmental arthroplasty or a total knee arthroplasty would place significant restrictions in this patient. A unispacer may be a temporizing procedure but is controversial and without substantial data in the literature. The knee arthroscopy will not address the medial compartment osteoarthritis. Nagel A, Insall JN, Scuderi GR: Proximal tibial osteotomy: A subjective outcome study. J Bone Joint Surg Am 1996;78:1353-1358. Rinonapoli E, Mancini GB, Corvaglia A, et al: Tibial osteotomy for varus gonarthrosis: A 10- to 21-year followup study. Clin Orthop 1998;353:185-193.

Question 13

Which of the following statements best describes the outcome of the routine use of continuous passive motion (CPM) machines after total knee arthroplasty (TKA)?

Explanation

Although CPM machines are used widely in the United States for patients undergoing TKA, the benefit seems to be marginal, if any. Numerous randomized trials have shown that final outcomes after total knee arthroplasty are unaffected by the use of CPM machines postoperatively. Some studies have suggested that use of CPM may improve flexion in the first few weeks, but any short-term benefit from the machine was lost by intermediate-term follow-up. Aside from potential improvement in flexion within the first few postoperative weeks, there does not appear to be any benefit from the machines. There is no improvement in pain, ambulation, or extension. The cost-effectiveness of these machines has been questioned by many authors. Pellicci PM, Tria AJ, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 287-293. McInnes J, Larson MG, Daltroy LH, et al: A controlled evaluation of continuous passive motion in patients undergoing total knee arthroplasty. JAMA 1992;268:1423-1428.

Question 14

When performing knee arthroplasty, which of the following procedures provides the most consistent fixation for the tibial component?

Explanation

All of the options, except cementing the metaphyseal portion and press fitting the keel of the tibial component, have been shown to create strong and long-lasting constructs; however, cementing of both the platform and the keel offers the most predictable solution. Cementing the platform and not the keel has been shown to have a higher loosening rate than the more traditional methods of fully cementing or using screws to augment fixation.

Question 15

Sterilization of ultra-high molecular weight polyethylene by gamma irradiation in air will degrade its wear performance because of

Explanation

Gamma irradiation has long been used as a sterilization method for polyethylene. Exposure to gamma irradiation causes breakage of the chemical bonds in the polyethylene, and oxidation will occur if the material is subsequently exposed to air. The amount of oxidation and decrease in wear performance is also related to the length of time that the gamma-irradiated polyethylene is exposed to oxygen. Collier JP, Sutula LC, Currier BH, et al: Overview of polyethylene as a bearing material: Comparison of sterilization methods. Clin Orthop 1996;333:76-86. McKellop H, Shen FW, Lu B, et al: Effect of sterilization method and other modifications on the wear resistance of acetabular cups made of ultra-high molecular weight polyethylene: A hip-simulator study. J Bone Joint Surg Am 2000;82:1708-1725.

Question 16

Figure 23 shows failure of the femoral stem in a patient. What is the most likely reason for the failure?

Explanation

A two-dimensional stress analysis has been used to study the effects of some of the factors leading to early fatigue failure of the femoral stem in total hip arthroplasty. It has been demonstrated that loss of proximal stem support at the level of the calcar femorale and subsequent stem stress can lead to fatigue failure. In addition, the role of body weight and range of cyclic stress fluctuation play an important role in fatigue life under conditions where the stem has lost proximal support. These results indicate that stem design could be improved by incorporating some means of adequate support at the calcar femorale where maximum tensile stresses are found to occur. Femoral component fracture is a rare but well-documented complication after total hip arthroplasty. Historically, most stem fractures occur at the middle third of the implant where proximal stem loosening and solid distal stem fixation result in cantilever bending and eventual fatigue failure. The component shown is a modular fluted cementless stem that occasionally fractures at the modular junction in patients with poor proximal bone support. Andriacchi TP, Galante JO, Belytschko TB, et al: A stress analysis of the femoral stem in total hip prostheses. J Bone Joint Surg Am 1976;58:618-624.

Question 17

What property of titanium alloys accounts for their high corrosion resistance in vivo?

Explanation

In both room temperature air and physiologic fluids, titanium alloys self-passivate or spontaneously form a layer of titanium oxide very rapidly. This layer makes titanium alloys resistant to surface breakdown. Callaghan JJ, Rosenberg AG, Rubash HE, et al (eds): The Adult Knee. Philadelphia, PA, Lippincott, 2003, vol 1, pp 269-278.

Question 18

Which of the following aids in correction of patellar tracking after total knee arthroplasty (TKA)?

Explanation

Correct patellofemoral tracking has proven to be a crucial aspect in TKA because a large percent of problems after TKA are related to the patellofemoral articulation. External rotation of the femoral and tibial components has been shown to aid in tracking. Likewise, medialization of the patellar button aids in patellar tracking and prevention of lateral subluxations and dislocations. Attention to the distal femoral cut is critical in maintaining the joint line and preventing patella baja or alta. Tibial sizing, however, is not directly related to patellar tracking after TKA. Callaghan JJ, Rosenberg AG, Rubash HE, et al (eds): The Adult Knee. Philadelphia, PA, Lippincott Williams & Wilkins, 2003, pp 1245-1258.

Question 19

Figure 24 shows the radiograph of a 36-year-old volleyball player with right hip pain. What is the cause of the pain?

Explanation

Femoral acetabular impingement usually presents in active young adults with the slow onset of groin pain that often starts after a minor trauma. Physical examination reveals limitation of motion with a positive impingement test which consists of forceful internal rotation with flexion and adduction. Femoral acetabular impingement is a mechanism for the development of early osteoarthritis in nondysplastic hips. Surgical debridement of the impinging, nonspherical portion of the femoral head restores offset and improves the clearance of the head, thus preventing abutment of the neck against the acetabular rim. The patient has no evidence of osteonecrosis, developmental dysplasia of the hip, rheumatoid arthritis, or femoral neck fracture. Ganz R, Parvizi J, Beck M, et al: Femoroacetabular impingement: A cause for osteoarthritis of the hip. Clin Orthop 2003;417:112-120.

Question 20

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

Explanation

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. 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.

Question 21

A 62-year-old woman with a bone mass density (BMD) T-score of -2.0 sustained a subcapital fracture of her hip. She is an avid tennis player, and history reveals no previous fractures. What is the most appropriate follow-up care?

Explanation

A DEXA scan is most appropriately used to establish a baseline score. Even if the bone mineral density is not within the osteoporotic range (T-score less than -2.5), a prior fragility fracture is a strong risk factor for a second fracture as a result of factors other than bone density, such as worsening vision or balance, confusion, or other predispositions to falls. The guidelines of the National Osteoporosis Foundation indicate that, following a fragility hip fracture, active anti-osteoporotic medication should be initiated, whether or not a DEXA scan is performed. A recent study showed that antiresorptive therapy following a hip fracture reduces not only the risk of a second fracture but also overall mortality.

Question 22

A 58-year-old patient who underwent bilateral hip arthroplasty 12 years ago now reports pain in his hips and difficulty with ambulation to the point where he now uses crutches. A radiograph of the hip and pelvis is shown in Figure 26. What is the best treatment option for this patient?

Explanation

The radiographs reveal acetabular component failure with bone loss. There are several treatment options available. The best option for survivorship is a cementless porous-coated acetabular component. This patient may or may not require structural bone graft, which may need to be determined at the time of surgery. Bipolar implants and cemented acetabular components for revision surgery have not demonstrated long-term success. The use of a protrusio ring is reserved primarily for massive bone loss such as a Paprosky type III bone loss with significant superior migration of the acetabular component. The best clinical results for acetabular component revision have been achieved with cementless porous-coated implants. Haddad FS, Masri BA, Garbuz DS, et al: Acetabulum, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopaedics. St Louis, MO, Mosby, 2002, pp 923-936. D'Antonio JA: Periprosthetic bone loss of the acetabulum: Classification and management. Orthop Clin North Am 1992;23:279-290.

Question 23

Figure 27 shows the AP radiograph of a patient who has late instability. The problem most likely occurred as a result of

Explanation

Although dislocation can occur anytime after hip arthroplasty, the highest incidence is observed within the first few months. Dislocation occurring many years after arthroplasty has also been described. In contrast to early dislocation, it appears that late dislocation frequently requires surgical intervention. Recent studies suggest that the incidence of late dislocation may be greater than initially appreciated and that the cumulative rate of dislocation rises with increasing follow-up. The presumed etiologic factors for late instability include long-standing problems with the prosthesis (such as malpositioning of the components) with late manifestation, trauma, deterioration in the neurologic status of the patient, and polyethylene wear. The eccentric position of the femoral head in this patient confirms polyethylene wear. The femoral stem is well-fixed, and the greater trochanter osteotomy has united well. The minor osteolysis observed around the proximal femur is also the consequence of wear and is not the cause of instability. Infection, without component loosening and massive soft-tissue destruction, is not otherwise known to result in late instability. Berry DJ, von Knoch M, Schleck CD, et al: The cumulative long-term risk of dislocation after primary Charnley total hip arthroplasty. J Bone Joint Surg Am 2004;86:9-14.

Question 24

Figure 28 shows the postoperative radiograph of a 36-year-old patient. The cerclage cable was placed for a minimal medial calcar fracture seen during femoral preparation. In the immediate postoperative period, what is the highest level of activity that would be safely permitted?

Explanation

The incidence of femoral fracture in primary cementless total hip arthroplasty ranges from 1.5% to 27.8%. It is imperative that the implant and fracture are stable both intraoperatively and postoperatively. Cerclage wiring or cerclage cabling is the current recommended treatment for nondisplaced calcar fractures and minimally displaced proximal fractures. Berend and associates reviewed the results of 58 total hips in 55 patients with intraoperative calcar fracture managed with single or multiple cerclage wires or cables and immediate full weight bearing. Follow-up averaged 7.5 years, and there were no revisions of the femoral component. No patients had severe thigh pain. Berend KR, Lombardi AV Jr, Mallory TH, et al: Cerclage wires or cables for the management of intraoperative fracture associated with a cementless, tapered femoral prosthesis: Results at 2 to 16 years. J Arthroplasty 2004;19:17-21. Schmidt AH, Kyle RF: Periprosthetic fractures of the femur. Orthop Clin North Am 2002;33:143-152.

Question 25

Embolic material generated during total knee arthroplasty (TKA) shown in Figure 29 is composed of which of the following substances?

Explanation

Emboli are created during TKA. Usually there is an increased incidence with the use of intramedullary rods that disrupt the marrow contents. These are not fat emboli per se. They are material composed of fat cells and marrow that act like pulmonary emboli to obstruct small arterioles in the lung. They are different from free fat emboli that are seen in fractures and that lead to chemical injury to the lung rather than obstructive injury. Markel DC, Femino JE, Farkas P, et al: Analysis of lower extremity embolic material after total knee arthroplasty in a canine model. J Arthroplasty 1999;14:227-232. Pell AC, Christie J, Keating JF, et al: The detection of fat embolism by transoesophageal echocardiography during reamed intramedullary nailing: A study of 24 patients with femoral and tibial fractures. J Bone Joint Surg Br 1993;75:921-925.

Question 26

A 32-year-old highly active man undergoes a total hip arthroplasty for osteonecrosis. To minimize long-term wear and eliminate the risk of polyethylene-induced osteolysis, which of the following bearing surface combinations is most appropriate?

Explanation

Ceramic-on-ceramic bearings offer the lowest wear rates among all bearing surfaces, making them ideal for young, highly active patients. They effectively eliminate the risk of polyethylene-induced osteolysis, though they carry risks of squeaking and catastrophic fracture.

Question 27

During a posterior-stabilized total knee arthroplasty, trial components are placed. The knee is symmetric and stable in extension but tight in flexion. Which of the following intraoperative modifications will best address this imbalance?

Explanation

A knee that is tight in flexion and stable in extension has a tight flexion gap and a balanced extension gap. Downsizing the femoral component (when using anterior referencing) increases the posterior condylar resection, effectively opening the flexion gap without affecting the extension gap.

Question 28

A 65-year-old man returns to the clinic 3 weeks after an uncomplicated primary total knee arthroplasty with acute onset of knee pain, swelling, and a draining sinus tract. Synovial fluid analysis shows a white blood cell count of 45,000/µL with 95% neutrophils. Radiographs show well-fixed components. What is the most appropriate management?

Explanation

Debridement, antibiotics, and implant retention (DAIR) with modular component exchange is indicated for acute periprosthetic joint infections (symptoms < 3 weeks or < 90 days post-op) with well-fixed implants. A draining sinus is not an absolute contraindication to DAIR in the acute postoperative setting.

Question 29

A 72-year-old woman experiences her third posterior dislocation 2 months after a primary total hip arthroplasty via a posterior approach. Radiographs reveal the acetabular component is placed in 45 degrees of abduction and 5 degrees of retroversion. The femoral stem is anteverted 15 degrees. What is the most appropriate definitive management?

Explanation

The patient's acetabular component is retroverted, strongly predisposing her to posterior instability. The most appropriate definitive treatment is isolated revision of the acetabular component to achieve proper anteversion (typically 15 to 20 degrees).

Question 30

A 68-year-old man with a history of a long spinal fusion from T10 to the pelvis is planned for a total hip arthroplasty. How does his spinal pathology alter the target placement of his acetabular component compared to a patient with normal spinopelvic mobility?

Explanation

Patients with spinopelvic stiffness (e.g., prior lumbopelvic fusion) cannot undergo normal posterior pelvic tilt during hip flexion. To prevent anterior bony impingement and subsequent posterior dislocation during sitting, the acetabular component must be placed in greater anteversion and abduction.

Question 31

An 80-year-old woman sustains a fall and presents with a periprosthetic fracture around her total hip arthroplasty stem. Radiographs show a fracture at the tip of the stem. The stem has subsided by 2 cm and the cement mantle is fractured. The acetabular component remains well-fixed. What is the most appropriate surgical treatment?

Explanation

This is a Vancouver B2 periprosthetic fracture, characterized by a fracture around a loose femoral stem with adequate proximal bone stock. The standard of care is revision of the femoral component using a long cementless stem that bypasses the fracture by at least two cortical diameters.

Question 32

A 65-year-old woman who underwent a posterior-stabilized total knee arthroplasty 9 months ago presents with a painful catching sensation in her knee. The catching occurs as she actively extends the knee from a flexed position, typically between 30 and 45 degrees of flexion. What is the most likely diagnosis?

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized TKA designs when a fibrous nodule forms at the superior pole of the patella. This nodule catches in the intercondylar box of the femoral component during active extension.

Question 33

A 68-year-old man presents with an inability to perform an active straight leg raise 4 weeks after a primary total knee arthroplasty. Examination reveals a palpable gap at the inferior pole of the patella. What is the most reliable surgical reconstruction method for this complication?

Explanation

Extensor mechanism disruption after TKA has a high failure rate with primary repair. Extensor mechanism allograft reconstruction (Achilles tendon or whole extensor mechanism) or synthetic mesh are preferred for reliable restoration of function.

Question 34

A 55-year-old active man with a ceramic-on-ceramic total hip arthroplasty complains of a squeaking noise during gait. Radiographs show a well-fixed implant. Which of the following component positions is most strongly associated with this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is primarily associated with edge loading. This is typically caused by malpositioning of the acetabular cup, particularly excessive inclination (vertical cup) or excessive anteversion.

Question 35

In kinematic alignment for a total knee arthroplasty, the surgical goal differs from traditional mechanical alignment by aiming to restore the patient's pre-arthritic joint lines. This approach typically results in which of the following component positions compared to mechanical alignment?

Explanation

Kinematic alignment aims to restore the native joint line, which typically involves placing the femoral component in slightly more valgus and the tibial component in slightly more varus compared to the neutral mechanical axis.

Question 36

A 70-year-old woman experiences multiple posterior dislocations following a primary THA via a posterior approach. A CT scan shows the acetabular component is in 5 degrees of anteversion and 40 degrees of inclination. The stem is in 15 degrees of anteversion. What is the most appropriate definitive management?

Explanation

The patient has a retroverted or under-anteverted acetabular cup (5 degrees) leading to recurrent posterior instability. Revision of the acetabular component to achieve appropriate anteversion (typically 15-20 degrees) is the definitive treatment.

Question 37

A 62-year-old man presents with knee pain 2 years after a primary TKA. Joint aspiration yields a synovial WBC count of 4,500 cells/uL with 85% neutrophils. Alpha-defensin is positive, and synovial CRP is 15 mg/L. According to the 2018 International Consensus Meeting criteria, what is the diagnosis?

Explanation

According to the 2018 ICM criteria, elevated synovial WBC (>3,000 cells/uL), elevated PMN% (>80%), positive alpha-defensin, and elevated synovial CRP strongly confirm the diagnosis of definite periprosthetic joint infection.

Question 38

A 55-year-old man with medial compartment knee osteoarthritis is being considered for a unicompartmental knee arthroplasty (UKA). Which of the following is considered an absolute contraindication for a medial UKA?

Explanation

An absent anterior cruciate ligament with clinical instability leads to altered kinematics and accelerated failure in a medial UKA. It is widely considered a strict contraindication, whereas age, obesity, and asymptomatic patellofemoral changes are relative.

Question 39

A 65-year-old man presents with new-onset groin pain 6 years after a metal-on-polyethylene THA with a modular titanium stem and cobalt-chromium head. Radiographs show no loosening. Serum cobalt is 8.5 ppb and chromium is 1.2 ppb. What is the best next step in management?

Explanation

Elevated serum cobalt levels with normal chromium in a metal-on-polyethylene THA indicates trunnionosis (corrosion at the head-neck taper). A MARS MRI is the best next step to evaluate for an adverse local tissue reaction (ALTR) or pseudotumor.

Question 40

A 60-year-old woman is 6 weeks post-primary TKA and has a range of motion of 10 to 75 degrees despite aggressive physical therapy. She has no signs of infection and radiographs show well-fixed, well-aligned components. What is the most appropriate next step?

Explanation

Manipulation under anesthesia (MUA) is most effective when performed between 6 and 12 weeks postoperatively for arthrofibrosis after TKA. Delaying intervention beyond this window decreases the likelihood of successfully restoring motion.

Question 41

Following a primary THA via a direct anterior approach, a patient complains of numbness and burning pain over the anterolateral thigh. Which of the following intraoperative maneuvers most likely caused this complication?

Explanation

The lateral femoral cutaneous nerve (LFCN) is at risk during the direct anterior approach. Aggressive retraction of the tensor fasciae latae or dissection lateral to the sartorius can compress or stretch the LFCN, causing anterolateral thigh paresthesias.

Question 42

A 70-year-old patient reports a feeling of instability and giving way when rising from a chair or using stairs 1 year after a TKA. Clinical examination demonstrates stability at 0 degrees and 90 degrees of flexion, but excessive varus-valgus laxity at 30 to 45 degrees of flexion. What is the primary cause of this presentation?

Explanation

Mid-flexion instability typically occurs when the joint line is elevated, often due to excessive distal femoral resection compensated by a thicker polyethylene insert. This leaves the collateral ligaments lax in mid-flexion despite being tight in extension and 90 degrees of flexion.

Question 43

A 68-year-old man is 3 weeks status post primary TKA and presents with a 4-day history of increasing knee pain, erythema, and a temperature of 38.5 C. Joint aspiration yields purulent fluid. Which of the following is the most appropriate indication for proceeding with Debridement, Antibiotics, and Implant Retention (DAIR)?

Explanation

DAIR is indicated for early postoperative infections (typically within 4 weeks of surgery) or acute hematogenous infections with symptom duration of less than 3 weeks, provided the implants are stable and the soft tissue envelope is intact.

Question 44

A 50-year-old woman with a metal-on-metal THA presents with a palpable groin mass and discomfort. A MARS MRI demonstrates a large, thick-walled cystic lesion communicating with the joint space. What histological characteristic is most commonly associated with this condition?

Explanation

Adverse local tissue reactions (ALTR) or pseudotumors in metal-on-metal THA are characterized histologically by an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). This involves perivascular lymphocytic infiltrates and extensive tissue necrosis.

Question 45

A 78-year-old woman sustains a fall resulting in a periprosthetic femur fracture around her cemented THA stem. Radiographs show a spiral fracture around the stem tip, and the stem has subsided 1 cm, indicating it is loose. Bone stock is adequate. According to the Vancouver classification, what is the most appropriate management?

Explanation

This is a Vancouver B2 fracture (fracture around the stem, loose stem, adequate bone stock). The standard of care is revision arthroplasty using a long, diaphyseal-engaging stem (fluted tapered or fully porous-coated) to bypass the fracture and achieve stability.

Question 46

During a posterolateral approach THA, which intraoperative landmark is most reliable for assessing leg length and offset changes prior to final component implantation?

Explanation

The most reliable intraoperative method to assess leg length and offset is to measure the distance between a fixed point on the pelvis (like a Steinman pin in the ilium) and a fixed reference point on the proximal femur (like a cautery mark on the greater trochanter).

Question 47

A patient complains of anterior knee pain and a "clunking" sensation 6 months following a primary TKA. Examination shows lateral patellar subluxation in early flexion. Which component malposition is most likely responsible for this finding?

Explanation

Internal rotation of either the femoral or tibial components increases the Q-angle, which pulls the extensor mechanism laterally. This leads to lateral patellar maltracking, subluxation, and anterior knee pain.

Question 48

A 35-year-old man on chronic corticosteroids presents with bilateral groin pain. MRI reveals bilateral femoral head osteonecrosis without subchondral collapse (Ficat Stage II). What is the primary rationale for performing a core decompression in this patient?

Explanation

Core decompression is indicated for pre-collapse osteonecrosis of the femoral head (Ficat Stage I or II). The rationale is to relieve elevated intraosseous pressure, improve blood flow, and stimulate angiogenesis and bone healing.

Question 49

A 42-year-old woman with severe bilateral hip osteoarthritis desires a hip resurfacing arthroplasty to maintain her high level of athletic activity. Which of the following factors is considered the most significant contraindication for hip resurfacing in this patient?

Explanation

Hip resurfacing is generally contraindicated in female patients and those with smaller femoral head sizes. These patients have a significantly higher risk of femoral neck fracture, implant failure, and adverse local tissue reactions from metal wear.

Question 50

In considering the design of a total knee arthroplasty, which of the following is a recognized indication for using a posterior-stabilized (PS) design rather than a cruciate-retaining (CR) design?

Explanation

A prior patellectomy alters knee kinematics and extensor mechanism mechanics, often leading to anterior-posterior instability. A posterior-stabilized (PS) design is recommended in these cases to substitute for the PCL and provide reliable AP stability.

Question 51

A 68-year-old woman is undergoing a primary total hip arthroplasty. She has a prior spinal fusion from L2 to the pelvis. Preoperative standing and sitting lateral radiographs show no change in her pelvic tilt. To minimize the risk of posterior dislocation, how should the acetabular component be positioned compared to a patient with normal spino-pelvic mobility?

Explanation

In a patient with a stiff spino-pelvic segment (fusion to pelvis), the pelvis fails to retrovert during sitting. This requires the acetabular component to be placed in increased anteversion to clear the femur and prevent posterior dislocation during hip flexion.

Question 52

During a primary total knee arthroplasty, the surgeon notes that the joint space is symmetrically tight in flexion, but perfectly balanced and symmetric in extension. Which of the following is the most appropriate next step to correct this mismatch?

Explanation

A knee that is balanced in extension but tight in flexion requires an increase in the flexion gap. This is achieved by downsizing the femoral component (reducing the AP diameter) or increasing the posterior slope of the tibial cut.

Question 53

A 62-year-old man presents with progressive groin pain 6 years after a metal-on-polyethylene total hip arthroplasty utilizing a titanium stem and a large-diameter cobalt-chromium head. Inflammatory markers are normal. Aspiration yields sterile, cloudy fluid, and MRI demonstrates a thick-walled cystic pseudotumor. What is the most likely etiology?

Explanation

The scenario describes adverse local tissue reaction (ALTR) due to mechanically assisted crevice corrosion, also known as trunnionosis. This is classic for a metal-on-polyethylene THA with a large cobalt-chromium head on a titanium stem presenting with a sterile pseudotumor.

Question 54

A 75-year-old woman sustains a closed fracture of her distal femur following a mechanical fall. Radiographs show a comminuted supracondylar femur fracture extending to the flange of her posterior-stabilized femoral component. The femoral component is noted to be grossly loose on fluoroscopy. What is the most appropriate surgical management?

Explanation

For a periprosthetic distal femur fracture with severe comminution and a loose femoral component (Felix Type IIB or Rorabeck Type III), a distal femoral replacement is the most reliable treatment to restore stability and allow early mobilization.

Question 55

An 80-year-old man presents with a periprosthetic femur fracture around a cementless THA stem after a fall. Radiographs reveal a fracture at the tip of the stem, and comparison with previous films shows the stem has subsided 2.5 cm. The surrounding bone stock is adequate. What is the standard of care?

Explanation

This describes a Vancouver B2 periprosthetic fracture (fracture around the stem, loose implant, good bone stock). The standard treatment is revision arthroplasty bypassing the fracture site with a long, diaphyseal-fitting stem.

Question 56

A 67-year-old woman presents 14 months after a posterior-stabilized TKA complaining of a painful catching sensation at the anterior aspect of her knee when extending from a flexed position. The catch consistently occurs around 35 degrees of flexion. What is the most likely diagnosis?

Explanation

Patellar clunk syndrome occurs in posterior-stabilized knees when a fibro-synovial nodule forms at the superior pole of the patella. This nodule catches in the femoral intercondylar notch during active extension, typically between 30 and 45 degrees.

Question 57

A 71-year-old man complains of persistent knee pain 2 years after a TKA. Aspiration of the joint reveals a synovial white blood cell (WBC) count of 4,200 cells/uL with 88% neutrophils. Serum CRP is 18 mg/L. What is the most appropriate definitive management for this chronic condition?

Explanation

The synovial fluid analysis confirms a chronic periprosthetic joint infection (WBC >3,000 cells/uL and >80% PMNs). The gold standard treatment for chronic PJI occurring months or years postoperatively is a two-stage revision arthroplasty.

Question 58

A 65-year-old man presents with progressive groin pain 5 years after a primary total hip arthroplasty (THA) utilizing a titanium stem, cobalt-chromium modular head, and highly cross-linked polyethylene liner. Radiographs show a well-fixed stem and cup with no osteolysis. Aspiration yields dark, turbid fluid with 500 WBCs/mcL and negative cultures. Serum cobalt is markedly elevated compared to chromium. What is the most likely diagnosis?

Explanation

Elevated cobalt relative to chromium with dark fluid and a metal-on-polyethylene bearing indicates mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction. This can lead to an adverse local tissue reaction (ALTR) requiring revision.

Question 59

A 72-year-old woman presents with an inability to perform a straight leg raise 4 weeks after a primary total knee arthroplasty (TKA). Examination reveals a palpable defect at the inferior pole of the patella. Surgical exploration confirms a massive patellar tendon rupture with severely attenuated, retracted tissue that cannot be approximated. What is the most reliable reconstructive option?

Explanation

In the setting of acute-on-chronic massive extensor mechanism deficiency post-TKA with poor tissue quality, an extensor mechanism allograft or synthetic mesh reconstruction provides the most reliable long-term clinical outcome. Primary repair has a high failure rate.

Question 60

A 68-year-old male is 3 weeks post-primary THA and presents with 3 days of increasing pain, erythema, and incisional drainage. CRP is 150 mg/L. Joint aspiration yields 45,000 WBCs/mcL with 95% polymorphonuclear cells. What is the optimal surgical management?

Explanation

This patient presents with an acute postoperative periprosthetic joint infection (less than 4 weeks post-op and short duration of symptoms). The optimal management is DAIR with exchange of modular components, followed by targeted antibiotic therapy.

Question 61

A 60-year-old woman is 1-year post-posterior stabilized TKA. She complains of a painful catching and popping sensation in her anterior knee as she actively extends her knee from a flexed position. What implant design factor most significantly contributes to this specific complication?

Explanation

Patellar clunk syndrome occurs in posterior-stabilized knees when a fibrotic nodule forms at the superior pole of the patella and catches in the intercondylar notch. A high intercondylar box ratio and sharp superior box edges increase this risk.

Question 62

A 55-year-old man with ankylosing spondylitis and a fused lumbar spine is undergoing THA. Preoperative standing and sitting lateral spinopelvic radiographs show less than 10 degrees of change in pelvic tilt between positions. How should the acetabular component positioning be adjusted to minimize dislocation risk?

Explanation

In a stiff spine, the pelvis fails to retrovert during sitting, leaving the acetabulum relatively under-anteverted and increasing the risk of anterior impingement and posterior dislocation. The cup should be placed in more anteversion to accommodate sitting.

Question 63

A 75-year-old woman sustains a periprosthetic femur fracture around a cemented polished taper slip stem. Radiographs show a fracture line propagating just distal to the tip of the stem. The stem has subsided 10 mm and the cement mantle is fragmented, but the proximal femur bone stock remains robust. According to the Vancouver classification, what is the most appropriate treatment?

Explanation

This is a Vancouver B2 fracture (fracture around a loose stem with adequate bone stock). The standard of care is revision arthroplasty using a diaphyseal engaging (extensively porous-coated or fluted tapered) stem bypassing the fracture by at least two cortical diameters.

Question 64

A 45-year-old woman complains of groin pain 6 months after an uncomplicated direct anterior approach THA. Pain is reproducible with active straight leg raise and resisted hip flexion. Radiographs demonstrate a neutral acetabular component with 8 mm of anterior overhang over the bony rim. Initial management should consist of?

Explanation

Anterior overhang of the acetabular cup can cause iliopsoas impingement. Initial management should always be conservative, including physical therapy and image-guided corticosteroid injections, before considering surgical tenotomy or cup revision.

Question 65

Squeaking in a ceramic-on-ceramic total hip arthroplasty is most strongly associated with which of the following biomechanical phenomena?

Explanation

Squeaking in ceramic-on-ceramic bearings is strongly correlated with edge loading, often due to cup malposition (high inclination or malversion). This edge loading causes stripe wear, disrupting fluid-film lubrication and producing the audible squeak.

Question 66

A 62-year-old woman requires a TKA for severe osteoarthritis. She has a documented severe nickel hypersensitivity with previous blistering from inexpensive jewelry. What is the most appropriate implant choice to minimize the risk of a hypersensitivity reaction?

Explanation

Standard cobalt-chromium implants contain small amounts of nickel, which can elicit reactions in highly sensitized patients. Oxidized zirconium (Oxinium) femurs paired with titanium tibial trays contain virtually zero nickel and are preferred in confirmed metal allergy.

Question 67

During a primary TKA utilizing a gap balancing technique, the surgeon finds that the extension gap is perfectly symmetric and rectangular. However, the flexion gap is tight medially and loose laterally. What is the most appropriate adjustment to the femoral component to balance the flexion gap?

Explanation

External rotation of the femoral component relative to the posterior condylar axis removes more bone from the posteromedial condyle and less from the posterolateral condyle. This opens the medial flexion space and tightens the lateral flexion space, balancing the gap.

Question 68

Which of the following describes the primary biomechanical mechanism by which a dual mobility cup decreases the risk of dislocation compared to a standard unconstrained THA?

Explanation

Dual mobility constructs consist of a standard head freely articulating within a larger polyethylene head, which then articulates within the metal shell. This increases the effective head diameter, vastly increasing the jump distance required for dislocation.

Question 69

A 68-year-old woman undergoes a primary TKA for an end-stage 25-degree valgus knee deformity. In the PACU, she has a complete foot drop and sensory loss over the dorsum of the foot. Pulses are symmetric and palpable. What is the immediate recommended management?

Explanation

Peroneal nerve palsy post-valgus TKA is typically a stretch neuropraxia resulting from deformity correction. Initial management includes releasing tight dressings and flexing the knee to 20-30 degrees to relieve tension on the nerve.

Question 70

Which of the following patient factors is widely considered an absolute contraindication to metal-on-metal hip resurfacing arthroplasty?

Explanation

Metal ions (cobalt and chromium) from metal-on-metal articulations are excreted renally. Renal insufficiency is an absolute contraindication as it prevents clearance of these ions, leading to systemic toxicity.

Question 71

A 65-year-old man is 8 weeks post-TKA and presents with an active and passive range of motion of 10 to 75 degrees despite aggressive, daily physical therapy. Radiographs confirm properly sized and positioned components without loosening. What is the most appropriate next step in management?

Explanation

For postoperative stiffness (arthrofibrosis) following TKA without component malposition, manipulation under anesthesia (MUA) is highly effective when performed within the optimal window of 6 to 12 weeks postoperatively.

Question 72

A 32-year-old man with a history of systemic lupus erythematosus and high-dose corticosteroid use presents with groin pain. Radiographs demonstrate mixed sclerosis and cysts in the superior femoral head, but the articular surface is perfectly spherical with no subchondral radiolucent crescent sign. MRI confirms osteonecrosis involving 25% of the weight-bearing surface. What is the most appropriate joint-preserving surgical intervention?

Explanation

This patient has pre-collapse avascular necrosis (AVN) of the femoral head (Ficat Stage II or Steinberg Stage II). Core decompression, with or without bone grafting, is the preferred joint-preserving treatment to relieve intraosseous pressure and promote revascularization.

Question 73

A 68-year-old woman with a severe valgus deformity undergoes a total knee arthroplasty using a lateral parapatellar approach. During trial reduction, the knee is tight in extension laterally but balanced in flexion. Which of the following structures should be released next?

Explanation

The iliotibial band is tight primarily in extension. Selective release of the IT band is appropriate when addressing isolated lateral tightness in extension during TKA.

Question 74

A 72-year-old man with previous lumbar fusion from L2 to S1 is scheduled for a total hip arthroplasty. Flexion-extension seating radiographs demonstrate less than 10 degrees of change in his pelvic tilt. To minimize the risk of posterior dislocation, how should the acetabular component be positioned compared to a patient with normal spinopelvic mechanics?

Explanation

Patients with a stiff spine cannot increase pelvic tilt when sitting, requiring the cup to be placed in greater anteversion and inclination to accommodate hip flexion. This prevents anterior impingement and subsequent posterior dislocation.

Question 75

A 65-year-old man presents with a painful total knee arthroplasty 3 years after the index procedure. His ESR is 45 mm/hr and CRP is 22 mg/L. Joint aspiration yields a WBC count of 2,500 cells/uL with 75% PMNs. Which of the following tests would be most definitive in confirming the diagnosis of periprosthetic joint infection?

Explanation

Alpha-defensin is a highly sensitive and specific biomarker for periprosthetic joint infection. It is particularly useful when standard aspiration results fall into the indeterminate or "grey" zone.

Question 76

An 80-year-old woman sustains a fall 8 years after a cementless total hip arthroplasty. Radiographs show a periprosthetic fracture around the femoral stem. The fracture extends into the diaphysis, and the stem is demonstrably loose. The patient has good remaining proximal bone stock. What is the most appropriate surgical management?

Explanation

This represents a Vancouver B2 fracture (fracture around a loose stem with good bone stock). The standard of care is revision of the femoral component using a bypass stem, typically a diaphyseal-engaging porous-coated or fluted tapered stem.

Question 77

A 70-year-old man presents with a complete patellar tendon rupture 4 years after a total knee arthroplasty. He has an active extension lag of 45 degrees. Primary repair is attempted but cannot be opposed without severe tension. What is the most reliable reconstructive option?

Explanation

Synthetic mesh reconstruction has shown superior outcomes and lower failure rates compared to extensor mechanism allografts for chronic ruptures in the setting of TKA. It provides a reliable scaffold for robust fibrovascular ingrowth.

Question 78

A 60-year-old man complains of groin pain 6 years after a metal-on-polyethylene total hip arthroplasty utilizing a large diameter cobalt-chromium head. Radiographs show a well-fixed implant with no osteolysis. Aspiration is negative for infection, but MARS MRI reveals a solid pseudotumor adjacent to the joint. What is the most likely etiology?

Explanation

Mechanically assisted crevice corrosion (trunnionosis) occurs at the head-neck junction, especially with large-diameter cobalt-chromium heads on titanium stems. This leads to an adverse local tissue reaction despite a metal-on-polyethylene bearing.

Question 79

During a posterior-stabilized total knee arthroplasty, the surgeon notes the knee is well-balanced and symmetric in extension, but symmetrically tight in flexion. Which of the following is the most appropriate next step?

Explanation

A knee that is tight in flexion but balanced in extension requires an increase in the flexion gap without altering the extension gap. Decreasing the anterior-posterior size of the femoral component achieves this.

Question 80

A 55-year-old woman complains of an audible squeaking sound from her ceramic-on-ceramic total hip arthroplasty while walking. Which of the following factors is most strongly associated with this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic THA is heavily correlated with edge loading, which often results from component malposition. This disrupts fluid film lubrication, leading to stripe wear and squeaking.

Question 81

Which of the following patient profiles represents an absolute contraindication to metal-on-metal hip resurfacing?

Explanation

Impaired renal function is an absolute contraindication to metal-on-metal bearings due to the inability to clear circulating cobalt and chromium ions. Furthermore, females of childbearing age and those with DDH are generally considered poor candidates.

Question 82

A 68-year-old woman reports a painful catching sensation in her knee when transitioning from deep flexion to extension, one year after a posterior-stabilized total knee arthroplasty. Which intraoperative factor most likely predisposed her to this condition?

Explanation

Patellar clunk syndrome occurs when a fibrotic nodule forms at the superior pole of the patella and catches in the intercondylar box of a posterior-stabilized femoral component during extension. It is managed by arthroscopic resection of the nodule.

Question 83

A 52-year-old active man with isolated medial compartment knee osteoarthritis is evaluated for a unicompartmental knee arthroplasty (UKA). Which of the following physical examination or radiographic findings is an established contraindication to UKA?

Explanation

Symptomatic patellofemoral osteoarthritis or diffuse anterior knee pain is a strict contraindication to a medial UKA. Intact ACL, correctable mild varus, and minor flexion contractures are acceptable indications.

Question 84

A patient undergoes a total hip arthroplasty via the direct anterior approach. Postoperatively, she develops numbness and a burning sensation over the anterolateral aspect of her thigh. Which of the following intervals was most likely aggressively retracted during the exposure?

Explanation

The direct anterior approach utilizes the internervous plane between the tensor fasciae latae and sartorius. Aggressive retraction medially can stretch or injure the lateral femoral cutaneous nerve, causing anterolateral thigh dysesthesia.

Question 85

Osteolysis following total knee arthroplasty is most commonly driven by a biologic cascade initiated by particulate debris. Which of the following cells is the primary mediator of this osteolytic process?

Explanation

Macrophages phagocytose polyethylene wear debris and release pro-inflammatory cytokines such as TNF-alpha and IL-1. This cascade ultimately activates osteoclasts, leading to periprosthetic osteolysis.

Question 86

A 65-year-old man is undergoing simultaneous bilateral total knee arthroplasty. To minimize the risk of perioperative deep vein thrombosis (DVT) and reduce blood loss, which anesthetic modality is most strongly recommended?

Explanation

Neuraxial anesthesia (spinal or epidural) is consistently associated with reduced blood loss, lower rates of DVT, and decreased perioperative mortality in lower extremity arthroplasty compared to general anesthesia.

Question 87

A 60-year-old woman with a history of massive weight loss following gastric bypass surgery presents with recurrent posterior instability of her total hip arthroplasty. Her abductor mechanism is chronically deficient and atrophic. If revision surgery is pursued, what is the most appropriate implant choice to provide stability?

Explanation

In patients with severe abductor deficiency and recurrent instability, standard head size increases are often insufficient. A dual-mobility construct or constrained acetabular liner is indicated to provide mechanical stability and prevent dislocation.

Question 88

A 58-year-old man with a metal-on-metal hip resurfacing presents for his 5-year follow-up. He is asymptomatic, and radiographs are pristine. Routine blood work reveals a serum cobalt level of 8.5 ppb (normal <1 ppb). What is the recommended next step in management?

Explanation

Elevated serum metal ions (cobalt or chromium > 7 ppb) in a metal-on-metal bearing warrant advanced imaging to evaluate for asymptomatic adverse local tissue reactions (ALTR) or pseudotumors. MARS MRI is the modality of choice.

Question 89

A 65-year-old man requires a total hip arthroplasty. He has a history of a long spinal fusion from T10 to the pelvis. Compared to a patient with normal spinopelvic mobility, this patient is at highest risk for which of the following complications, and how should acetabular cup positioning be adjusted?

Explanation

With a fused spine, the pelvis cannot retrovert to accommodate hip flexion during sitting. This leads to anterior impingement of the femur on the pelvis, levering the femoral head out posteriorly. Consequently, the cup requires greater anteversion to accommodate sitting flexion and prevent posterior dislocation.

Question 90

During a total knee arthroplasty for a severe valgus deformity, the surgeon notes that the lateral compartment is tight in extension but balanced in 90 degrees of flexion. Which of the following structures is the most appropriate to release first?

Explanation

In the valgus knee, tightness in extension only indicates an iliotibial band contracture. The popliteus predominantly causes tightness in flexion, whereas the lateral collateral ligament causes tightness in both flexion and extension.

Question 91

A 58-year-old man presents with progressive groin pain 6 years after a total hip arthroplasty utilizing a titanium stem, a cobalt-chromium head, and highly cross-linked polyethylene. Radiographs show well-fixed components, but MRI reveals a large solid and cystic mass surrounding the hip joint. Laboratory tests reveal elevated serum cobalt with normal chromium. What is the most likely diagnosis?

Explanation

Mechanically assisted crevice corrosion (trunnionosis) at the head-neck junction can occur with a cobalt-chromium head on a titanium stem. It presents with an adverse local tissue reaction (ALTR) and disproportionately elevated serum cobalt compared to chromium.

Question 92

A 62-year-old woman complains of a painless, palpable popping sensation at the anterior aspect of her knee that occurs when extending her knee from a flexed position. She underwent a posterior-stabilized total knee arthroplasty 14 months ago. What is the most likely etiology of her symptoms?

Explanation

Patellar clunk syndrome is characterized by a fibrous nodule forming at the superior pole of the patella. During active extension, this nodule catches in the intercondylar box of a posterior-stabilized femoral component before popping out.

Question 93

A 68-year-old man sustains a traumatic complete rupture of the patellar tendon 3 months following a primary total knee arthroplasty. He is unable to perform a straight leg raise. What is the most appropriate surgical management?

Explanation

Primary repair of patellar tendon ruptures in the setting of a TKA has an unacceptably high failure rate due to poor soft-tissue quality and compromised vascularity. Reconstruction with an extensor mechanism allograft or synthetic mesh is the preferred definitive treatment.

Question 94

A 42-year-old highly active man is undergoing a total hip arthroplasty. The surgeon selects a ceramic-on-ceramic bearing surface. Which of the following is a known disadvantage specific to this bearing combination when compared to ceramic-on-polyethylene?

Explanation

Ceramic-on-ceramic bearings have exceptionally low wear rates but are associated with a unique complication of audible squeaking. This phenomenon occurs in up to 10% of patients and may be related to micro-separation, edge loading, or component malposition.

Question 95

A 71-year-old woman presents with persistent right knee pain 2 years after a primary total knee arthroplasty. Her serum ESR is 40 mm/hr and CRP is 22 mg/L. A synovial fluid aspirate yields a white blood cell (WBC) count of 4,200 cells/mcL with 72% polymorphonuclear cells (PMNs). Which of the following is the most appropriate next step in management?

Explanation

The synovial WBC count is in the equivocal range (3,000-10,000 cells/mcL) for chronic periprosthetic joint infection based on ICM criteria. Secondary biomarker tests like alpha-defensin or synovial CRP are indicated to confirm the diagnosis before proceeding to major revision surgery.

Question 96

A 38-year-old woman with systemic lupus erythematosus presents with bilateral hip pain. She has a history of high-dose corticosteroid use. Radiographs are normal, but MRI demonstrates bilateral anterosuperior femoral head edema with a serpiginous band of low signal intensity. There is no evidence of subchondral collapse. What is the most appropriate joint-preserving surgical intervention?

Explanation

The patient has early-stage avascular necrosis (Ficat Stage I/II) without subchondral collapse or joint space narrowing. Core decompression decreases intraosseous pressure and creates a channel for revascularization, making it the ideal joint-preserving procedure in pre-collapse stages.

Orthopedic Board Review Set 675: 100 MCQs for ABOS, OITE, FRCS – Hip Focus

Orthopedic Hip & Knee 2026 MCQs: Board Review Questions & Answers (Part 2)

Key Takeaway

Orthopedic Hip & Knee 2026 MCQs: Board Review Questions & Answers (Part 2)

Chapter Index