AAOS Orthopedic MCQs: Hip & Knee Reconstruction Review

Question 1

A 37-year-old man who works in a factory has isolated, lateral unicompartmental pain about his knee with activities. Nonsurgical management has failed to provide relief. The radiograph shown in Figure 45 reveals a tibiofemoral angle of approximately 15 degrees which is clinically correctable to neutral. What is the best surgical option in this patient?

Explanation

Patients with a valgus alignment about the knee can have lateral compartment arthritis. Similar to a high tibial osteotomy, a supracondylar femoral osteotomy is indicated in younger patients who have a more active lifestyle and isolated unicompartmental disease. In this young patient who works in a factory and has a valgus knee, a medial closing wedge supracondylar femoral osteotomy is the treatment of choice. The role of arthroplasty is limited in younger patients. Mathews J, Cobb AG, Richardson S, et al: Distal femoral osteotomy for lateral compartment osteoarthritis of the knee. Orthopedics 1998;21:437-440.

Question 2

Figure 46 shows the AP radiograph of an active 80-year-old patient with an acetabular fracture. The fracture was initially managed nonsurgically; however, the patient is now scheduled to undergo total hip arthroplasty. What is the treatment of choice for the contained acetabular bone defect?

Explanation

Acetabular fractures can result in a relative or actual acetabular bone defect. The medial blow-out fracture of the acetabulum has united well in this patient. It is likely that a medial shell of bone will be present during hip arthroplasty. The femoral head may be used as morcellized or structural bone to augment the medial defect and is preferred to structural allograft. Bipolar hip arthroplasty is notorious for medial migration in patients without a medial bone defect; therefore, it will not be a good choice in this patient. Filling the defect with methylmethacrylate cement, though an option, is not the best option in this active patient with an extensive medial defect. A double-bubble acetabular cup is used for patients with deficiency of the bone in the dome region. Mears DC: Surgical treatment of acetabular fractures in elderly patients with osteoporotic bone. J Am Acad Orthop Surg 1999;7:128-141.

Question 3

A 28-year-old woman who is an avid runner reports pain about the left hip with activities. Nonsurgical management has failed to provide relief. An MRI arthrogram is shown in Figure 47. What is the most likely diagnosis?

Explanation

The MRI arthrogram reveals dye extravasation into the labrum, consistent with a labral tear. The MRI findings are not typical of osteonecrosis, stress fracture, or transient osteoporosis. There is no increase in bone marrow edema in the neck or femoral head. Guanche CA, Sikka RS: Acetabular labral tears with underlying chondralmalacia: A possible association with high-level running. Arthroscopy 2005;21:580-585.

Question 4

Figure 48a shows the full-leg standing radiograph of a patient with a prior femoral fracture. Figure 48b shows the lateral view of the same joint. The patient is scheduled to undergo total knee arthroplasty. Because the mechanical axis of the lower extremity in patients with a prior femoral fracture may be disrupted, which of the following should be used during surgery to restore the mechanical axis of the lower extremity in this patient?

Explanation

The radiograph shows hardware that was used for fixation of a prior femoral fracture. The mechanical axis of the lower extremity in this patient is nearly normal (3 degrees valgus), and the deformity at the healed fracture site (14 degrees) does not appear to affect the joint alignment and is acceptable. Use of a routine knee prosthesis will be possible in this patient. To avoid hardware removal, extramedullary jigs and/or computerized navigation may be used to measure and restore the long axis of the femur. The use of a hinged prosthesis does not influence the mechanical axis directly. Extra-articular osteotomy is occasionally needed to reverse severe deformities. Papadopoulos EC, Parvizi J, Lai CH, et al: Total knee arthroplasty following distal femoral fractures. Knee 2002;9:267-274.

Question 5

Figure 49 shows a histologic section of the lung in a patient who died during total hip arthroplasty. What unexpected finding is seen in the pulmonary capillaries?

Explanation

Sudden death during total hip arthroplasty has been reported. In a report from the Mayo Clinic, intraoperative death occurred during cemented total hip arthroplasty in 23 patients. Fat and marrow embolization during preparation of the femur or cementing of the femoral component was believed to be responsible for the cardiopulmonary collapse that occurred during arthroplasty. Although fat and marrow emboli were found in the pulmonary capillaries of most of the patients on autopsy, this histologic section shows two particles of cement in the pulmonary capillaries. Parvizi J, Holiday AD, Ereth MH, et al: The Frank Stinchfield Award. Sudden death during primary hip arthroplasty. Clin Orthop 1999;369:39-48.

Question 6

After trial placement of components in a primary total knee arthroplasty, the knee is unable to come to full extension, but the flexion gap is appropriately balanced. After adequate soft-tissue releases have been performed, what is the next most appropriate action to balance the reconstruction?

Explanation

The reconstruction requires additional resection of the distal femur to allow increased extension while maintaining the current flexion gap tension. Resecting more proximal tibia or decreasing the tibial polyethylene thickness will decrease flexion tension as well as extension tension. Adding posterior femoral augments and using a larger femoral component will increase flexion tension. Ayers DC, Dennis DA, Johanson NA, et al: Common complications of total knee arthroplasty. J Bone Joint Surg Am 1997;79:278-311.

Question 7

Figure 50 shows the cross table lateral radiograph of a 31-year-old paratrooper who has recalcitrant groin pain. The pain is worse after activities such as standing or sitting (driving). Examination reveals that pain can be reproduced by internal rotation of the leg with the hip and knee in 90 degrees of flexion. Extensive nonsurgical managment has failed to provide relief. What is the treatment of choice?

Explanation

The radiograph reveals the classic "bump" that is seen in patients with femoroacetabular impingement (FAI). Ganz and associates described two types of FAI. This patient has cam impingement, which describes a nonspherical femoral head being forced into the acetabulum during hip motion and resulting in labral and chondral injury. Hip arthroscopy and labral debridement is unlikely to control the symptoms because the underlying anatomic abnormality is often difficult to address with arthroscopy. The treatment involves surgical dislocation of the hip with preservation of the blood supply to the femoral head, removal of the asphericity on the femoral side (femoral osteoplasty), and removal of the acetabular rim (acetabular osteoplasty) if the latter is found to contribute to impingement. Ganz R, Gill TJ, Gautier E, et al: Surgical dislocation of the adult hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br 2001;83:1119-1124. Ganz R, Parvizi J, Beck M, et al: Femoroacetabular impingement: A cause for early osteoarthritis of the hip. Clin Orthop 2003;417:112-120.

Question 8

During total knee arthroplasty, the patella is noted to subluxate laterally despite a lateral retinacular release. Which of the following methods is most likely to improve patellar stability?

Explanation

Slight external rotation of the tibial component will cause a net medialization of the tibial tubercle when the knee is articulated. This will help centralize the extensor mechanism over the trochlear groove and minimize the tendency for lateral subluxation. Internal rotation of the femoral component increases the risk of patellar instability. Anterior translation of the tibial component moves the patellar tendon insertion posteriorly, and may increase force on the patella but should not substantially alter patellar tracking. Clinical studies have shown no patellofemoral benefits to the use of fixed- or mobile-bearing designs. Thicker patellar components will not improve tracking, and may compound the problem. 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 207, 323-337 Pagnano MW, Trousdale RT, Stuart MJ, et al: Rotating platform knees did not improve patellar tracking: A prospective, randomized study of 240 primary total knee arthroplasties. Clin Orthop 2004;428:221-227.

Question 9

A 73-year-old man has stiffness after undergoing primary posterior cruciate ligament-retaining total knee arthroplasty 18 months ago. Extensive physiotherapy, dynamic splinting, and manipulations under anesthesia have failed to result in improvement. Examination reveals range of motion from 30 degrees to 60 degrees of flexion. The components are well fixed, and the evaluation for infection is negative. In discussing the possibility of revision arthroplasty, the patient should be advised that

Explanation

Stiffness following primary total knee arthroplasty remains a vexing problem. Treatment options have included extensive physical therapy, dynamic splinting, manipulation under anesthesia, arthroscopic arthrolysis, open arthrolysis with polyethylene exchange, and ultimately revision arthroplasty. Results are not as gratifying as would be expected. Babis and associates performed an open arthrolysis and polyethylene exchange on seven patients who were followed for a mean of 4.2 months. The results were poor. The mean improvement in arc of motion was only 20 degrees. Nicholls and Dorr treated 13 patients for stiffness. Only 40% of those patients obtained good to excellent results. Four patients (30%) required manipulation because of recurrent stiffness postoperatively. They noted they could not predictably improve the arc of motion with a revision operation. Haidukewych and associates reported on 15 patients who underwent revision of well-fixed components after total knee arthroplasty for stiffness. Of the 15 patients, 10 (66%) were satisfied with the outcome revision. Interestingly, they noted that in patients for whom the total arc of motion did not improve but who regained near full extension, there was a greater amount of satisfaction with the procedure than for those who did not regain full extension. Babis GC, Trousdale RT, Pagnano MW, et al: Poor outcomes of isolated tibial insert exchange and arthrolysis for the management of stiffness following total knee arthroplasty. J Bone Joint Surg Am 2001;83:1534-1536. Nicholls DW, Dorr LD: Revision surgery for stiff total knee arthroplasty. J Arthroplasty 1990;5:S73-S77.

Question 10

A 62-year-old patient is seen for routine follow-up after undergoing cementless total hip arthroplasty 2 years ago. The patient reports limited range of motion that severely affects daily activities. A radiograph is shown in Figure 51. Management should now consist of

Explanation

The patient has symptomatic postoperative heterotopic ossification after total hip arthroplasty. Postoperative prophylactic treatments include nonsteroidal anti-inflammatory drugs (usually indomethacin) or low-dose irradiation. The heterotopic ossification shown here is quite mature; therefore, nonsurgical management will not be successful. Surgical excision of grade III or IV heterotopic ossification should be followed with postoperative irradiation to minimize the chances of recurrence. Ayers DC, Evarts CM, Parkinson JR: The prevention of heterotopic ossification in high-risk patients by low-dose radiation therapy after total hip arthroplasty. J Bone Joint Surg Am 1986;68:1423-1430.

Question 11

What bilateral surgical intervention is considered inappropriate based on the findings shown in the radiograph in Figure 52?

Explanation

The radiograph reveals osteonecrosis of both femoral heads with reasonably maintained joint surfaces. There may be some slight flattening of the femoral heads. Hip arthrodesis is difficult to perform because of the necrotic bone. Its use in patients with osteonecrotic hips is limited because of the 80% bilaterality; therefore, it is not an acceptable alternative. All the other options are acceptable interventions. Mont MA, Jones LC, Sotereanos DG, et al: Understanding and treating osteonecrosis of the femoral head. Instr Course Lect 2000;49:169-185.

Question 12

Figure 53a shows the AP radiograph of a 70-year-old patient who is scheduled to undergo unicompartmental knee arthroplasty. Figure 53b shows the immediate postoperative radiograph, and the radiograph shown in Figure 53c, obtained 6 months after surgery, shows a medial tibial plateau fracture. The etiology of the fracture is best related to

Explanation

While all of the above may contribute to the etiology of a tibial plateau fracture following unicompartmental knee arthroplasty, the recent literature has clearly noted that pin placement for fixation of tibial resection guides is the most critical factor associated with a tibial plateau fracture following unicompartmental knee arthroplasty. Vince and Cyran suggest that fractures associated with unicompartmental knee arthroplasty might be avoidable by limiting the number and paying attention to the location of the pin holes that are created to secure the tibial resection guides. Brumby and associates suggest avoiding multiple guide pin holes in the proximal tibia for unicompartmental knee arthroplasty. They currently recommend the use of one centrally placed pin and an ankle clamp to stabilize the resection guide. Yang and associates note that a medial tibial plateau fracture in association with minimally invasive unicompartmental knee arthroplasty can be eliminated by avoiding fixation pins close to the medial tibial cortex. Brumby SA, Carrington R, Zayontz S, et al: Tibial plateau stress fracture: A complication of unicompartmental knee arthroplasty using 4 guide pinholes. J Arthroplasty 2003;18:809-812. Yang KY, Yeo SJ, Lo NN: Stress fracture of the medial tibial plateau after minimally invasive unicompartmental knee arthroplasty: A report of 2 cases. J Arthroplasty 2003;18:801-803.

Question 13

During impaction of a cementless acetabular component, the posterior column was fractured and found to be displaced. Which of the following is considered the most appropriate surgical option?

Explanation

Acetabular bone loss presents a challenge during reconstruction. A cementless hemispherical cup can be used in most patients provided that the acetabular rim, particularly the posterior column, is intact. When the posterior column is disrupted, fixation with a reconstruction plate and/or the use of an antiprotrusio cage is recommended. The latter is particularly important when the posterior column is fractured and displaced, such as in this patient. Under these circumstances, reduction of the fracture and application of an antiprotrusio cage is recommended. In this particular type of case, some surgeons may elect to retain the hemispherical cup and apply an antiprotrusio cage over the cup ("cage over cup" technique). Berry DJ: Antiprotrusio cages for acetabular revision. Clin Orthop 2004;420:106-112.

Question 14

Which of the following factors increases the risk of sciatic nerve injury in primary total hip arthroplasty (THA)?

Explanation

Injury to the sciatic nerve is a relatively rare but serious complication of THA. Dissection of the sciatic nerve is not typically done during primary THA, although the nerve can be identified during the surgical approach. An anterolateral approach to THA would not necessarily be associated with any greater incidence of sciatic nerve injury than other approaches. Screw fixation for the acetabular component is often a matter of surgeon preference. Provided that the anatomic safe zones for screw fixation (posterior inferior and posterior superior) are recognized, injury to the sciatic nerve from acetabular screws can be minimized. Restoration of anatomic length is important in primary THA. Overlengthening can result in sciatic nerve palsy. Developmental dysplasia of the hip can lead to a congenitally shortened extremity with concomitant congenital shortening of the associated neurovascular structures. Overlengthening of the extremity during THA for developmental dysplasia of the hip can lead to sciatic palsy. Osteonecrosis is not an associated risk factor for sciatic nerve palsy. DeHart MM, Riley LH Jr: Nerve injuries in total hip arthroplasty. J Am Acad Orthop Surg 1999;7:101-111.

Question 15

A 68-year-old woman who underwent a right total hip arthroplasty 1 year ago has dislocated her hip five times since surgery. Radiographs show a retroverted acetabular component. What is the best treatment for this patient?

Explanation

The most common cause of recurrent dislocation following total hip arthroplasty continues to be component malposition. Component malposition should be addressed prior to any other treatment options, such as increasing soft-tissue tension with increased femoral offset or greater trochanteric advancement. A larger femoral head size may help, but correcting the component malposition should give more predictable results. A retroverted acetabular component should be revised to 15 degrees to 20 degrees of anteversion, matching the patient's anatomy with an abduction angle close to 45 degrees. Daly PJ, Morrey BF: Operative correction of an unstable total hip arthroplasty. J Bone Joint Surg Am 1992;74:1334-1343. Jolles BM, Zangger P, Leyvraz PF: Factors predisposing to dislocation after primary total hip arthroplasty: A multivariate analysis. J Arthroplasty 2002;17-282-288.

Question 16

Figure 54 shows the preoperative radiograph of a 45-year-old woman who is considering total hip arthroplasty with her orthopaedic surgeon. What femoral characteristic is a typical concern in this patient?

Explanation

Developmental dysplasia of the hip (DDH) leads to early arthritis of the hip as seen in this patient. Although DDH is believed to mostly affect the acetabulum, most patients with DDH also have anatomic aberrations of the femur. Using three-dimensional computer models generated by reconstruction of CT scans, dysplastic femurs were shown to have shorter necks and smaller, straighter canals than the controls. The shape of the canal became more abnormal with increasing subluxation. The studies also have shown that the primary deformity of the dysplastic femur is rotational, with an increase in anteversion of 5 degrees to 16 degrees, depending on the degree of subluxation of the hip. The rotational deformity of the dysplastic femur arises within the diaphysis between the lesser trochanter and the isthmus and is not attributable to a torsional deformity of the metaphysis. Osteopenia is not a concern in a patient with an excellent cortical index (thick cortices and narrow canal). Femoral varus or bowing of the femur is not a typical finding in patients with DDH. Noble PC, Kamaric E, Sugano N, et al: Three-dimensional shape of the dysplastic femur: Implications for THR. Clin Orthop 2003;417:27-40.

Question 17

A 68-year-old man with no significant medical history underwent a total knee arthroplasty 4 years ago. A radiograph is shown in Figure 55. He reports that he had no problems with the knee until 6 weeks ago when he noted the gradual onset of pain following a colonoscopy. Examination reveals a painful, swollen knee. Knee aspiration reveals a WBC count of 40,000/mm3. Management should consist of

Explanation

The treatment of choice for a late hematogenous infection is two-stage resection arthroplasty and reimplantation, with parenteral antibiotics prior to reimplantation. This is particularly true when septic loosening has occurred as in this patient. Open irrigation and debridement with polyethylene exchange has been used successfully when the duration of symptoms is 3 weeks or less. Long-term suppressive antibiotics are most commonly used when the patient's medical condition precludes further surgery. Delayed reimplantation has been shown to be superior to immediate reimplantation in multiple studies. Little data support the use of arthroscopic irrigation and debridement. Swanson KC, Windsor RE: Diagnosis of infection after total knee arthroplasty, in Callaghan JJ, Rosenberg AG, Rubash HE, et al (eds): The Adult Knee. Philadelphia, PA, JB Lippincott, 2003, vol 2, pp 1485-1491.

Question 18

Which of the following substances makes up the majority by weight of the extracellular matrix for articular cartilage?

Explanation

The extracellular matrix consists of water, proteoglycans, and collagen. Water makes up the majority (approximately 65% to 80%) of wet weight; 95% of the collage is type II with much smaller amounts of other collagens, including types IV, VI, IX, X, and XI. The exact functions of these other collagens are unknown, but they are believed to be important in matrix attachment and stabilization of the diameter of collagen fibrils. Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 444-445.

Question 19

A 58-year-old woman is seen in the emergency department after falling at home. History reveals that she underwent right total knee arthroplasty 2 years ago. Radiographs are shown in Figures 56a and 56b. What is the most appropriate treatment?

Explanation

The radiographs show an oblique periprosthetic distal femoral fracture. Of the options listed, open reduction and internal fixation is the most appropriate surgical option because a well-fixed, posterior stabilized closed box femoral component is present. Nonsurgical methods are not favored because of the highly displaced, unstable fracture pattern and prolonged immobility. Revision with a stemmed component is an option but would sacrifice more bone stock in this younger patient. Moran MC, Brick GW, Sledge CB, et al: Supracondylar femoral fracture following total knee arthroplasty. Clin Orthop 1996;324:196-209. Raab GE, Davis CM III: Early healing with locked condylar plating of periprosthetic fractures around the knee. J Arthroplasty 2005;20:984-989.

Question 20

A patient with a valgus knee and lateral compartment bone loss undergoes a total knee arthroplasty using posterior condylar referencing instrumentation. Six months after surgery, the patient reports significant anterior knee pain, and radiographs reveal severe lateral patellar tilt. Management should consist of

Explanation

Severe valgus deformity is frequently accompanied by hypoplasia of the lateral femoral condyle. Posterior referencing instrumentation can substantially internally rotate the femoral component with respect to the transepicondylar axis and Whiteside's line. The femoral component malrotation must be corrected to properly address this problem. Berger RA, Della Valle CJ, Rubash HE: Patellofemoral problems in total knee arthroplasty, in Callaghan JJ, Rosenberg AG, Rubash HE, et al (eds): The Adult Knee. Philadelphia, PA, JB Lippincott, 2003, vol 2, pp 1245-1258.

Question 21

Figures 57a through 57c show the radiographs of a patient who has pain, discomfort, and a popping sensation localized to the posterior aspect of the knee after undergoing primary left total knee arthroplasty 6 months ago. Examination reveals that the patient is able to ambulate without a limp. There is no significant swelling, erythema, or effusion. Range of motion is 0 degrees to 115 degrees, and a palpable crepitation or snapping is detected at the posterior lateral joint line. What is the most likely diagnosis?

Explanation

Popliteal snapping syndrome represents the most likely diagnosis. Barnes and Scott noted that the popliteus tendon can be a potential source of internal derangement after total knee arthroplasty. They noted that it can be subluxated anteriorly and posteriorly over a retained lateral femoral condyle osteophyte. Allardyce and associates described the condition as a popliteus condition, snapping as it rolls over a retained lateral femoral condylar osteophyte. Patellar clunk syndrome is a distinct syndrome associated with the patella and has been reported in posterior stabilized knees. In addition to crepitation with range of motion, the patella literally snaps or jumps as the knee is taken from flexion to extension. Beight JL, Yao B, Hozack WJ, et al: The patellar "clunk" syndrome after posterior stabilized total knee arthroplasty. Clin Orthop 1994;299:139-142. Barnes CL, Scott RD: Popliteus tendon dysfunction following total knee arthroplasty. J Arthroplasty 1995;10:543-545.

Question 22

Which of the following is the primary mechanism of polyethylene wear in the hip?

Explanation

Although previous theories on acetabular wear implicated fatigue cracking and delamination as primary wear mechanisms, these have actually manifested as major modes of polyethylene wear in knees. The primary mechanism of wear in polyethylene acetabular components appears to be adhesion and abrasion. In an analysis of 128 components retrieved at autopsy or revision surgery, wear appeared to occur mostly at the surface of the components and was the result of large strain plastic deformation and orientation of the surface layers into fibrils that subsequently ruptured during multidirectional motion. It was also shown conclusively that 32-mm heads displayed significantly more wear (volumetric wear) than either 22-mm or 26-/28-mm heads (1-mm increase in size increased volumetric wear by 10%). The wear at the articulating surface was characterized by highly worn polished areas superiorly and less worn areas inferiorly separated by a ridge. Abrasion was very common, occurring after adhesion and plastic deformation of polyethylene fibrils, and abrasion secondary to third-body wear. Wear rates decreased with longer survival of components, indicating a "bedding in" phenomenon, arguing against oxidative and fatigue wear. Crevice corrosion occurs in fatigue cracks with low oxygen tension (under screw heads, etc). Oscillatory fretting consists of cyclical abrading of the outer surface from small movements. Fatigue and delamination is predominant in total knee arthroplasty where stresses are maximum just below the surface of the polyethylene component, causing fatigue over time with subsequent delamination. In contrast, hip wear occurs primarily at the surface of the polyethylene component. Jasty M, Goetz DD, Bragdon CR, et al: Wear of polyethylene acetabular components in total hip arthroplasty: An analysis of one hundred and twenty-eight components retrieved at autopsy or revision operations. J Bone Joint Surg Am 1997;79:349-358. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 47-53. Bell CJ, Walker PS, Abeysundera MR, et al: Effect of oxidation on delamination of ultrahigh-molecular-weight polyethylene tibial components. J Arthroplasty 1998;13:280-290.

Question 23

Which of the following complications may occur subsequent to resurfacing hip arthroplasty for osteonecrosis of the hip but not after total hip arthroplasty?

Explanation

Advocates of resurfacing hip arthroplasty cite preservation of the proximal femoral bone stock as the main advantage of this procedure over total hip arthroplasty. Fracture of the retained femoral neck has been reported following resurfacing arthroplasty. The exact etiology of the latter is unknown. Technical errors, such as notching of the femoral neck or possibly disruption of the blood supply to the femoral head during extensive soft-tissue exposure, may result in femoral neck fracture. Gabriel JL, Trousdale RT: Stem fracture after hemiresurfacing for femoral head osteonecrosis. J Arthroplasty 2003;18:96-99.

Question 24

Which of the following statements best describes results that have been reported with roentgen stereophotogrammetric analysis (RSA)?

Explanation

Migration of total hip femoral components has been measured by RSA, a technique that affords accuracy of 2 degrees and 0.5 mm. Several published studies on total hip arthroplasty femoral components have established the importance of this technique. Both cemented and cementless components migrate, with the rate of migration suggesting the adequacy of fixation of a component. Migration of 1 mm to 2 mm (occurring in either the varus-coronal plane and retroversion-transverse plane, or both) has been associated with a higher risk of loosening of the component.

Question 25

Osteonecrosis of the large joints may develop in patients with which of the following conditions?

Explanation

Osteonecrosis of major joints can occur in patients exposed to corticosteroids, alcohol, and antiseizure medications, as well as patients with hemaglobulinopathy, such as sickle cell anemia. In addition, patients with primary APS who had not taken corticosteroids were also found to be at high risk for osteonecrosis of the hip. In one study of 30 patients with primary APS, asymptomatic osteonecrosis was evident in 20%. A recent article has also found a high association between idiopathic osteonecrosis of the hip and collagen II mutation. None of the other conditions has been shown to be associated with a higher risk of osteonecrosis. Tektonidou MG, Malagari K, Vlachoyiannopoulos PG, et al: Asymptomatic avascular necrosis in patients with primary antiphospholipid syndrome in the absence of corticosteroid use: A prospective study by magnetic resonance imaging. Arthritis Rheum 2003;48:732-736.

Question 26

A 65-year-old man undergoes a posterior-stabilized total knee arthroplasty. Intraoperative trialing reveals the knee is perfectly balanced in full extension but is overly tight in 90 degrees of flexion. What is the most appropriate surgical step to balance the knee?

Explanation

Tightness isolated to flexion is managed by decreasing the anteroposterior diameter of the femoral component. This effectively increases the flexion gap without altering the extension gap.

Question 27

A 52-year-old man reports an audible squeaking noise from his right hip 3 years after a ceramic-on-ceramic total hip arthroplasty. He denies any pain or instability. What is the most common cause of this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic THA is strongly associated with component malposition, specifically extreme anteversion or retroversion, which leads to edge loading and stripe wear.

Question 28

During a total knee arthroplasty, the femoral component is inadvertently placed in 5 degrees of internal rotation relative to the surgical transepicondylar axis. This error is most likely to result in which of the following complications?

Explanation

Internal rotation of the femoral component medializes the distal condyles and lateralizes the trochlear groove relative to the extensor mechanism. This significantly increases the Q-angle and the risk of lateral patellar maltracking.

Question 29

When performing a primary total hip arthroplasty via the direct anterior (Smith-Petersen) approach, the deep surgical interval is developed between which two muscles?

Explanation

The superficial interval of the direct anterior approach is between the sartorius (femoral nerve) and TFL (superior gluteal nerve). The deep interval is between the rectus femoris and the TFL.

Question 30

An 82-year-old woman sustains a fall 10 years after a primary total hip arthroplasty. Radiographs reveal a periprosthetic femur fracture extending around the tip of the stem. The stem is frankly loose, but there is excellent surrounding diaphyseal bone stock. According to the Vancouver classification, what is the best treatment?

Explanation

A fracture around a loose stem with adequate bone stock is a Vancouver B2 fracture. The standard of care is revision to a longer stem, bypassing the fracture by at least two cortical diameters, to achieve diaphyseal fixation.

Question 31

A 66-year-old man presents with a chronically painful TKA. Joint aspiration is performed to rule out periprosthetic joint infection (PJI). The synovial fluid alpha-defensin test returns positive. What is the primary function of alpha-defensin in this context?

Explanation

Alpha-defensin is an antimicrobial peptide released by activated neutrophils in response to infection. It serves as a highly sensitive and specific biomarker for diagnosing periprosthetic joint infection.

Question 32

A 45-year-old woman presents with persistent anterior groin pain 1 year after an uncemented total hip arthroplasty. The pain is exacerbated by active straight leg raising. A cross-table lateral radiograph shows the acetabular component overhangs the anterior bone edge by 6 mm. What is the most appropriate initial management?

Explanation

The patient's presentation is classic for iliopsoas impingement over a prominent anterior acetabular rim. Initial management should always be nonoperative, utilizing NSAIDs and physical therapy before considering surgical release or cup revision.

Question 33

A 60-year-old woman complains of a painful 'catching' sensation at the anterior aspect of her knee when extending from a flexed position, 14 months after a posterior-stabilized total knee arthroplasty. What is the most likely etiology of this condition?

Explanation

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

Question 34

The primary advantage of highly cross-linked polyethylene compared to conventional ultra-high-molecular-weight polyethylene (UHMWPE) in total hip arthroplasty is:

Explanation

Highly cross-linked polyethylene significantly reduces volumetric wear and the subsequent generation of submicron particles. This drastically lowers the risk of periprosthetic osteolysis compared to conventional UHMWPE.

Question 35

A 72-year-old woman undergoes revision total knee arthroplasty. Intraoperatively, she is noted to have a deficient medial collateral ligament (MCL) but an intact patellar tendon and adequate bone stock. Which type of implant constraint is most appropriate?

Explanation

A constrained condylar knee (CCK) utilizes a tall, wide central post to substitute for a deficient collateral ligament (specifically the MCL or LCL) in the setting of balanced gaps and an intact extensor mechanism.

Question 36

A direct lateral (Hardinge) approach is used for a primary total hip arthroplasty. To minimize the risk of denervation to the anterior portion of the abductor musculature, proximal splitting of the gluteus medius should be limited to what distance superior to the tip of the greater trochanter?

Explanation

The superior gluteal nerve runs approximately 3 to 5 cm proximal to the tip of the greater trochanter. Splitting the gluteus medius proximal to this safe zone risks nerve injury and subsequent abductor weakness (Trendelenburg gait).

Question 37

A 60-year-old man presents with a painful, swollen hip 6 years after a metal-on-polyethylene total hip arthroplasty. Aspirate yields fluid with a high lymphocyte count, but cultures are negative. Serum cobalt levels are highly elevated, while chromium is normal. What is the most likely diagnosis?

Explanation

Elevated serum cobalt levels with normal chromium, an ALVAL reaction, and a metal-on-polyethylene bearing point to mechanically assisted crevice corrosion at the modular head-neck junction (trunnionosis).

Question 38

During total knee arthroplasty, the surgeon evaluates the gaps with trial components. The knee is tight in full extension but perfectly balanced at 90 degrees of flexion. Which of the following is the most appropriate corrective action?

Explanation

A tight extension gap with a balanced flexion gap is corrected by resecting more bone from the distal femur. This enlarges the extension space without affecting the flexion space.

Question 39

A 55-year-old active male is undergoing total hip arthroplasty. He asks about bearing surface options. Which of the following bearing couples has the lowest volumetric wear rate while avoiding the risk of squeaking or stripe wear?

Explanation

Ceramic-on-highly cross-linked polyethylene (HXLPE) offers excellent wear characteristics, significantly lower than CoCr-on-HXLPE. It avoids the unique risks of squeaking and catastrophic component fracture associated with ceramic-on-ceramic bearings.

Question 40

During a primary posterior-stabilized total knee arthroplasty, the knee is found to be well-balanced in extension but tight in flexion. Which of the following is the most appropriate adjustment to achieve a balanced gap?

Explanation

A tight flexion gap with a balanced extension gap can be addressed by downsizing the femoral component when using anterior referencing, which decreases the posterior condylar offset. Alternatively, increasing the posterior tibial slope can also increase the flexion gap.

Question 41

A 72-year-old woman presents with thigh pain after a fall. A radiograph reveals a fracture around her cemented femoral stem.

The stem is visibly loose with subsidence, but the proximal femoral bone stock is adequate. According to the Vancouver classification, what is the most appropriate surgical treatment?

Explanation

This is a Vancouver B2 periprosthetic fracture (fracture around the stem, loose stem, adequate bone stock). The gold standard treatment is revision to a long uncemented, extensively porous-coated or fluted tapered stem to bypass the fracture.

Question 42

A 68-year-old man presents with acute onset of knee pain, swelling, and fever 3 weeks following a primary total knee arthroplasty. Aspiration yields a synovial white blood cell count of 65,000 cells/µL with 95% neutrophils. Which of the following is the most appropriate initial management?

Explanation

Debridement, antibiotics, and implant retention (DAIR) with exchange of modular components is the indicated treatment for acute postoperative periprosthetic joint infections, typically defined as occurring within 4 weeks of the index surgery.

Question 43

A surgeon is performing a primary total hip arthroplasty utilizing the direct anterior approach. Which of the following describes the internervous plane utilized in the superficial dissection?

Explanation

The direct anterior (Smith-Petersen) approach exploits the superficial internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve).

Question 44

A 54-year-old woman complains of groin pain 6 years after receiving a metal-on-metal total hip arthroplasty. Her radiograph shows a steep cup abduction angle. MRI demonstrates a large fluid collection around the joint.

Serum cobalt and chromium are significantly elevated. Which histological finding is most expected in the periprosthetic tissue?

Explanation

Adverse local tissue reactions (ALTR) associated with metal-on-metal implants typically show an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). This is secondary to a type IV delayed hypersensitivity reaction to metal wear debris.

Question 45

A 65-year-old woman undergoes a posterior-stabilized total knee arthroplasty. Intraoperatively, with the trial components in place, the knee is stable in extension but exhibits significant laxity in flexion. Which of the following component changes is the most appropriate next step?

Explanation

A loose flexion gap with a stable extension gap is managed by increasing the anteroposterior dimension of the femur. Downsizing the femur or using a thicker polyethylene would not isolate the flexion gap alone.

Question 46

A 48-year-old active man complains of a loud, high-pitched squeaking noise coming from his right hip, particularly when bending to tie his shoes. He underwent an uncomplicated ceramic-on-ceramic total hip arthroplasty 2 years ago. Radiographs demonstrate a well-fixed stem and a cup with 65 degrees of inclination. What is the most likely cause of this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, often due to a steeply inclined or excessively anteverted cup. This causes microseparation and abnormal wear patterns.

Question 47

A 65-year-old woman undergoes a posterior-stabilized (PS) total knee arthroplasty. Postoperatively, she experiences a sense of instability when rising from a low chair. Evaluation reveals a cam-post dislocation. What is the primary mechanical feature that prevents this specific complication in a properly balanced PS TKA?

Explanation

In a posterior-stabilized TKA, the cam-post mechanism substitutes for the PCL. A sufficient 'jump distance'—the vertical height the femoral cam must translate to dislocate over the tibial post—prevents posterior dislocation of the tibia during deep flexion.

Question 48

A 45-year-old active man presents with a high-pitched squeaking noise from his hip 3 years after a cementless primary THA with a ceramic-on-ceramic bearing. The noise occurs primarily during deep flexion activities. Which of the following component positional factors most strongly correlates with this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic THA is heavily associated with edge loading, which disrupts the normal fluid lubrication film between the bearings. This microseparation and edge loading typically results from acetabular cup malposition, particularly excessive inclination or version.

Question 49

A 72-year-old man presents with a painful TKA 4 years postoperatively. Both ESR and CRP are elevated. Joint aspiration yields synovial fluid with a WBC count of 4,500 cells/uL and 85% neutrophils. Which additional synovial fluid test has the highest specificity for confirming a periprosthetic joint infection?

Explanation

Alpha-defensin is an antimicrobial peptide released by activated neutrophils in response to pathogens. It has demonstrated extremely high sensitivity and specificity for diagnosing periprosthetic joint infection, outperforming traditional inflammatory markers.

Question 50

An 82-year-old woman with a history of recurrent posterior dislocations following a primary THA presents for revision. She has severe neuromuscular weakness and poor compliance with hip precautions. Her abductor mechanism is deficient but structurally intact. What is the most appropriate acetabular reconstruction option to minimize future dislocation risk?

Explanation

Dual-mobility articulations increase the effective head size and jump distance, significantly reducing dislocation rates in high-risk patients. They are preferred over constrained liners when the abductor mechanism is at least partially functioning due to lower rates of mechanical failure and aseptic loosening.

Question 51

A 68-year-old man presents 1 year after a posterior-stabilized TKA complaining of a painful catch and audible "pop" in his knee when extending from a flexed position. The examination is otherwise normal, and radiographs are unremarkable. What is the most likely etiology of his symptoms?

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized TKAs when a fibrous nodule forms at the superior pole of the patella and catches in the femoral intercondylar box during extension. Treatment typically involves arthroscopic or open excision of the fibrous nodule.

Question 52

A 55-year-old woman is being evaluated for a medial unicompartmental knee arthroplasty (UKA). According to classical and modern guidelines, which of the following preoperative findings is an absolute contraindication for this procedure?

Explanation

Inflammatory arthritis (e.g., rheumatoid arthritis) is considered an absolute contraindication for UKA due to the pan-articular nature of the disease. Age, moderate obesity, and minor fixed flexion contractures (< 15 degrees) are no longer considered absolute contraindications in modern practice.

Question 53

In total hip arthroplasty, the use of highly cross-linked polyethylene (HXLPE) has significantly reduced wear rates compared to conventional polyethylene. Which of the following manufacturing processes specifically decreases the fatigue strength and fracture toughness of HXLPE?

Explanation

Remelting HXLPE after irradiation eliminates free radicals to prevent oxidation but decreases the material's crystallinity. This reduction in crystallinity subsequently lowers the mechanical fatigue strength and fracture toughness of the polyethylene.

Question 54

A 58-year-old woman complains of persistent groin pain 6 years after receiving a metal-on-metal total hip arthroplasty. Aspiration of the hip yields sterile, blood-tinged fluid. MRI demonstrates a large, solid and cystic periarticular mass. Histologic examination of the periarticular tissue would most likely demonstrate which of the following?

Explanation

Adverse local tissue reactions (ALVAL) associated with metal-on-metal implants are characterized by a delayed type IV hypersensitivity response. Histology typically shows characteristic perivascular lymphocytic infiltration, tissue necrosis, and the formation of pseudotumors.

Question 55

During a primary TKA in a patient with a varus deformity, the surgeon assesses the gaps using spacer blocks after making the initial bone cuts. The knee is tight medially in both extension and flexion. What is the most appropriate initial soft tissue release to balance the knee?

Explanation

When a varus knee is tight medially in both flexion and extension, it indicates a symmetric medial tightness. Release of the deep medial collateral ligament (MCL) off the proximal medial tibia is the most appropriate initial step to balance the gaps.

Question 56

A surgeon performs a primary total hip arthroplasty using the direct anterior (Smith-Petersen) approach. Which of the following represents the correct superficial internervous plane utilized in this surgical approach?

Explanation

The direct anterior approach to the hip utilizes a true internervous and intermuscular plane. The superficial interval is safely developed between the sartorius (supplied by the femoral nerve) and the tensor fasciae latae (supplied by the superior gluteal nerve).

Question 57

An 81-year-old man falls and sustains a periprosthetic femur fracture around his cemented THA.

Radiographs reveal a fracture occurring around a loose femoral stem, but with adequate surrounding proximal bone stock. What is the most appropriate surgical treatment?

Explanation

A fracture around a loose femoral stem with adequate remaining bone stock is classified as a Vancouver type B2 periprosthetic fracture. The standard of care is revision of the loose component to a long-stem prosthesis that bypasses the fracture by at least two cortical diameters.

Question 58

A 66-year-old man undergoes explantation of an infected TKA and placement of an articulating antibiotic-loaded cement spacer. Six weeks later, his wound is well-healed, and serum ESR and CRP have normalized. Before proceeding with the second-stage reimplantation, what is the most appropriate next step to confirm eradication of the infection?

Explanation

Prior to a second-stage reimplantation, evaluating the joint for residual infection is critical, even with normalized serum inflammatory markers. Joint aspiration for synovial fluid cell count, culture, and potentially biomarkers is recommended to ensure the infection is eradicated before placing new implants.

Question 59

During trialing in a primary THA via a posterior approach, the surgeon notes the leg lengths are perfectly equal to the contralateral side, but the hip easily dislocates in adduction and internal rotation. To increase stability via soft tissue tensioning without altering the leg length, which of the following component changes should be made?

Explanation

A high-offset femoral stem increases the horizontal distance from the center of rotation to the femoral shaft, tightening the abductors and improving stability. It accomplishes this strictly on the horizontal axis without increasing vertical leg length, unlike substituting a longer femoral head.

Question 60

A 70-year-old woman presents with progressive knee pain 12 years after a primary TKA.

Radiographs demonstrate extensive osteolysis behind the tibial tray. Which of the following factors is most strongly associated with accelerated polyethylene wear and subsequent osteolysis in TKA?

Explanation

Coronal plane malalignment in TKA leads to eccentric loading and increased focal contact stresses on the polyethylene insert. This significantly accelerates polyethylene wear, generating particulate debris that initiates the macrophage-mediated biological cascade resulting in osteolysis.

Question 61

A 65-year-old woman suffers an acute patellar tendon rupture 3 months following a primary TKA. Primary repair is attempted but fails at 6 weeks postoperatively. She now has an active extensor lag of 40 degrees and profound difficulty mobilizing. What is the most reliable surgical option for restoring extensor mechanism function?

Explanation

In the setting of a failed extensor mechanism repair after TKA, direct primary repair has an unacceptably high failure rate. Use of an extensor mechanism allograft (such as an Achilles tendon with a bone block or a whole patellar-tendon-tubercle allograft) or synthetic mesh offers the most reliable reconstruction.

Question 62

During a primary total knee arthroplasty (TKA), the surgeon decides to use a posterior-stabilized (PS) implant. Which of the following best describes the primary mechanical function of the cam-and-post mechanism in this design?

Explanation

In a PS TKA, the tibial post engages the femoral cam during knee flexion, driving the femur posteriorly. This forced femoral rollback substitutes for the resected posterior cruciate ligament, improving maximum flexion and preventing anterior femoral subluxation.

Question 63

A 65-year-old man presents with an audible and palpable squeaking sound from his right hip 2 years after a primary total hip arthroplasty (THA). Radiographs show well-fixed components. What is the most likely bearing surface combination he received?

Explanation

Squeaking is a specific, well-documented complication associated with ceramic-on-ceramic bearing surfaces in THA. It is often linked to component malpositioning, edge loading, and stripe wear.

Question 64

A 68-year-old woman presents with a painful total knee arthroplasty 4 years post-surgery. Her serum ESR and CRP are elevated. Aspiration yields synovial fluid. According to the Musculoskeletal Infection Society (MSIS) criteria, what minimum synovial fluid white blood cell (WBC) count strongly indicates a chronic periprosthetic joint infection?

Explanation

For a chronic periprosthetic joint infection (PJI), a synovial fluid WBC count of >3,000 cells/uL (with >80% PMNs) is a major diagnostic criterion. In the acute postoperative period (<6 weeks), a higher threshold of >10,000 cells/uL is used.

Question 65

A 70-year-old man undergoes revision THA for recurrent posterior dislocations. During the procedure, the surgeon notes that the existing acetabular component is in neutral version. To minimize future posterior instability, the surgeon should reposition the cup to achieve which target orientation?

Explanation

Lewinnek's 'safe zone' for acetabular cup placement to minimize the risk of dislocation is historically defined as 15 degrees (+/- 10 degrees) of anteversion and 40 degrees (+/- 10 degrees) of abduction. Retroversion or inadequate anteversion significantly increases the risk of posterior dislocation.

Question 66

A 62-year-old woman complains of a painful catch and an audible pop when actively extending her knee from a flexed position, one year after a primary TKA.

What implant design or technical factor most increases the risk of this specific complication?

Explanation

This presentation is classic for patellar clunk syndrome, caused by a fibrotic nodule forming at the superior pole of the patella. It is most commonly associated with posterior-stabilized (PS) designs due to the nodule catching in the intercondylar box during extension.

Question 67

A 55-year-old woman presents with persistent groin pain and a palpable mass 4 years after a metal-on-metal THA. Imaging reveals a solid and cystic mass adjacent to the joint. Which histological finding is most characteristic of this condition?

Explanation

The patient has a pseudotumor due to an adverse local tissue reaction (ALTR/ALVAL) from metal wear debris. Histology characteristically shows an aseptic lymphocytic vasculitis-associated lesion (ALVAL) with extensive necrosis and perivascular lymphocytic cuffing.

Question 68

During a primary TKA using a measured resection technique, the extension gap is symmetric and perfectly balanced, but the flexion gap is unacceptably tight. What is the most appropriate surgical step to correct this mismatch?

Explanation

A tight flexion gap with a balanced extension gap implies the anteroposterior dimension of the femoral component is too large. Downsizing the femoral component removes more posterior bone, which opens the flexion gap without altering the extension gap.

Question 69

An 82-year-old woman falls and sustains a periprosthetic femur fracture around her cementless THA stem.

Radiographs demonstrate a fracture at the tip of the stem. The stem is loose, but there is adequate proximal bone stock. According to the Vancouver classification, what is the standard treatment?

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 stem that bypasses the fracture by at least two cortical diameters, typically utilizing a diaphyseal engaging design.

Question 70

In a TKA, which of the following soft-tissue releases is most appropriate to correct a severe fixed valgus deformity?

Explanation

A fixed valgus deformity in TKA requires stepwise release of contracted structures on the lateral side. The standard sequence typically involves the iliotibial (IT) band, the lateral collateral ligament (LCL), and the popliteus tendon, depending on whether the tightness is in flexion or extension.

Question 71

A surgeon performs a THA using the direct anterior approach (DAA). This approach exploits a true internervous plane between which two muscles?

Explanation

The direct anterior approach utilizes the Smith-Petersen interval. This is a true internervous plane between the sartorius (innervated by the femoral nerve) and the tensor fasciae latae (innervated by the superior gluteal nerve).

Question 72

A 75-year-old woman sustains a supracondylar femur fracture just above a well-fixed, closed-box posterior-stabilized (PS) TKA femoral component.

What is the preferred method of fixation for this Lewis-Rorabeck Type II fracture?

Explanation

Because the PS TKA component has a closed-box design, a retrograde intramedullary nail cannot be passed through the intercondylar notch. The best option for a fracture above a well-fixed, closed-box component is ORIF with a lateral locked plate.

Question 73

A 30-year-old man with a history of high-dose corticosteroid use presents with groin pain. Hip radiographs are normal, but an MRI shows a focal lesion in the anterosuperior femoral head with a double-line sign. There is no subchondral collapse. What is the most appropriate initial surgical intervention?

Explanation

The patient has pre-collapse (Ficat Stage I/II) avascular necrosis of the femoral head. In a young, active patient prior to subchondral collapse, core decompression is indicated to relieve intraosseous pressure and potentially delay the need for joint replacement.

Question 74

A 55-year-old man presents with an audible squeaking noise from his hip 2 years after a total hip arthroplasty with a ceramic-on-ceramic bearing.

Which of the following factors is most strongly associated with this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic hips is strongly associated with component malposition, specifically acetabular cup anteversion or inclination errors that lead to edge loading. This disrupts fluid film lubrication, causing the ceramic surfaces to rub directly.

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

AAOS Orthopedic MCQs (Set 4): Hip & Knee Reconstruction | Board Review Questions

Key Takeaway

AAOS Orthopedic MCQs (Set 4): Hip & Knee Reconstruction | Board Review Questions

Chapter Index