Orthopedic Hip & Knee 2026 MCQs: Board Review Pt 1

Question 1

A patient is scheduled to undergo total knee arthroplasty (TKA) following failure of nonsurgical management. History reveals that she underwent a patellectomy as a teenager as the result of a motor vehicle accident. Examination reveals normal ligamentous stability. For the most predictable outcome, which of the following implants should be used?

Explanation

Paletta and Laskins performed a retrospective study of the results of TKA with cement in 22 patients who had a previous patellectomy. Nine of the patients had insertion of a posterior cruciate ligament-substituting implant. Thirteen patients had insertion of a posterior cruciate ligament-sparing implant. The 5-year postoperative knee scores were 89 for the posterior cruciate ligament-substituting knee versus 67 for the posterior cruciate ligament-sparing knee (P < 0.01). The patella functions to increase the lever arm of the extensor mechanism and to position the quadriceps tendon and the patellar ligament roughly parallel to the anterior cruciate ligament and posterior cruciate ligament, respectively. The patellar ligament thereby provides a strong reinforcing structure that functions to prevent excessive anterior translation of the femur during flexion of the knee. The absence of the patella results in the patellar ligament and the quadriceps tendon being relatively in line with one another. After a patellectomy, the resultant quadriceps force is no longer parallel to the posterior cruciate ligament. This results in loss of the reinforcing function of the patellar ligament. The authors believe this loss of reinforcing function may place increased stresses on the posterior cruciate ligament and posterior aspect of the capsule, which may result in stretching of these structures over time. They found a high rate of anteroposterior instability, a high prevalence of recurvatum, and a high rate of loss of full active extension compared with passive extension in the posterior cruciate ligament-sparing group, which supports their theory. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 559-582.

Question 2

Figure 1 shows the radiograph of a patient who underwent a total knee revision with a posterior stabilized mobile-bearing prosthesis and now has recurrent knee dislocations. What is the most likely cause?

Explanation

The patient has a posterior stabilized total knee revision, and the femoral component has dislocated over the tibial polyethylene cam/post. This usually indicates a loose flexion gap, or "flexion instability." A loose flexion gap can occur due to undersizing of the femoral component, anteriorization of the femoral component, excessive distal augmentation of the distal femur, or collateral ligament insufficiency, especially if combined with posterior capsular insufficiency. Isolated laxity of the extension gap (with a well-balanced flexion gap) causes varus/valgus instability, but it rarely causes the femoral component to "jump" the tibial cam of a posterior stabilized tibial insert. Malrotation of the components may cause patellar instability or a rotational instability of the tibiofemoral joint but should not cause a frank posterior dislocation of the tibia, unless combined with other errors of balancing. Although a mobile-bearing total knee arthroplasty may be more sensitive to errors in balancing than a fixed-bearing total knee arthroplasty, this complication does not reflect a faulty prosthetic design. 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 339-365. Lotke PA, Garino JP: Revision Total Knee Arthroplasty. New York, NY, Lippincott-Raven, 1999, pp 173-186, 227-249.

Question 3

A metal-on-metal bearing used for total hip arthroplasty shows which of the following properties?

Explanation

Activity levels do not affect cobalt and chromium ion levels, which are the bulk of serum ion levels. The majority of ions are produced in the run-in period in the first several years. A gradual reduction in ion levels occurs thereafter. The kidneys are responsible for the bulk of clearance from the serum, and to date there is no relationship of cancer to ion levels in the serum.

Question 4

Which of the following treatment regimens for thromboembolic prophylaxis meets the American College of Chest Physicians Guidelines for 10-day treatment after total hip arthroplasty and total knee arthroplasty?

Explanation

Only three thromboembolic treatment protocols have reached Grade 1A status for the American College of Chest Physicians Guidelines for thromboembolic prophylaxis after total hip arthroplasty and total knee arthroplasty. Grade 1A evidence shows a clear benefit/risk improvement with supportive data from randomized clinical trials, which are strongly applicable in most clinical circumstances. Warfarin is recommended but at an INR level of 2 to 3. Low-molecular-weight heparin and fondaparinox are also acceptable treatment options. Aspirin, adjusted dose unfractionated heparin, and elastic compressive stockings are not recommended as stand-alone options. Colwell C: Evidence based guidelines for prevention of venous thromboembolism: Symposia. Proceedings of the 2005 AAOS Annual Meeting. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2005, pp 15-18.

Question 5

Figures 2a and 2b show the radiographs of a 72-year-old man with aseptic loosening of the tibial component of his total knee arthroplasty. Optimal management should include

Explanation

2b The radiographs show massive subsidence of the lateral side of the tibia with severe tibial bone loss and a fractured proximal fibula. Reconstruction should consist of a large metal or bony lateral tibial augmentation, and a stem long enough to bypass the defect is required. The femoral and tibial components are articulating without any remaining polyethylene medially; therefore, the femoral component is damaged and needs revision. The insertions of the lateral ligaments are absent, thereby rendering the lateral side of the knee predictably unstable. Also, the large valgus deformity compromises the medial collateral ligament. The posterior cruciate ligament is also likely to be deficient with this much tibial bone destruction. The patient requires a posterior stabilized femoral component at the minimum, and possibly a constrained femoral component. Retention of the femoral component, even though it may be well-fixed, jeopardizes the outcome. Lotke PA, Garino JP: Revision Total Knee Arthroplasty. New York, NY, Lippincott-Raven, 1999, pp 137-250. Insall JN, Windsor RE, Scott WN, et al: (eds): Surgery of the Knee, ed 2. New York, NY, Churchill Livingstone, 1993, pp 935-957.

Question 6

Which of the following factors is responsible for causing the distal femur to pivot about a medial axis as the knee moves from full extension into early flexion?

Explanation

The radius of curvature of the distal femur is greater over the distal aspect of the lateral femoral condyle than the distal aspect of the medial femoral condyle. As the femur rolls posteriorly during early knee flexion, both condyles undergo similar angular changes equal to the amount of flexion. With a similar amount of angular rotation, the sphere with the larger radius experiences greater net rollback, producing a pivoting motion. Although the anterior cruciate ligament plays a role in producing tibial rotations, the posterior cruciate ligament does not play a significant role in producing such rotations. Similarly, the tibial tubercle does not play a significant role in producing normal rotations of the femur relative to the tibia. The popliteus may also play a role in producing rotational pivots, as might differential laxity of the medial and lateral collateral ligaments in early knee flexion. 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 239-240.

Question 7

Figure 3 shows the AP radiograph of a patient with diabetes mellitus who has knee pain. A semiconstrained knee prosthesis was used in this patient to prevent which of the following complications?

Explanation

The radiographic appearance of the joint is highly suspicious for neuropathic joint (Charcot's joint). Evidence of bone loss on both the tibial and the femoral sides may necessitate the use of metal and/or bone augments. Patients with a neuropathic joint often have excellent range of motion, and postoperative stiffness is not a problem. The main problem with these patients is instability that occurs secondary to ligamentous laxity. Use of a semiconstrained prosthesis prevents the latter complication. Parvizi J, Marrs J, Morrey BF: Total knee arthroplasty for neuropathic (Charcot) joints. Clin Orthop 2003;416:145-150.

Question 8

Based on the radiograph shown in Figure 4, the innervation of what muscle is most at risk with total hip arthroplasty?

Explanation

The radiograph reveals a Crowe IV deformity in a patient with developmental dysplasia of the hip. If hip arthroplasty is performed, then some degree of limb lengthening is anticipated. Excessive limb lengthening can result in sciatic nerve palsy in these patients. The peroneal branch of the sciatic nerve is most often affected. Of the muscles listed, only the extensor hallucis longus is innervated by the peroneal branch of the sciatic nerve. Eggli S, Hankemayer S, Muller ME: Nerve palsy after leg lengthening in total replacement arthroplasty for developmental dysplasia of the hip. J Bone Joint Surg Br 1999;81:843-845.

Question 9

A 75-year-old woman who fell on her right knee now reports pain and is unable to bear weight. History reveals that she underwent total knee arthroplasty on the right knee 6 years ago. Radiographs are shown in Figure 5. Management should now consist of

Explanation

The radiographs show a loose femoral component with an associated medial condyle distal femoral fracture. The treatment of choice is open reduction and internal fixation with revision of the femoral component because of the femoral component loosening. Moran MC, Brick GW, Sledge CB, et al: Supracondylar femoral fracture following total knee arthroplasty. Clin Orthop 1996;324:196-209. McLaren AC, DuPont JA, Schroeber DC: Open reduction internal fixation of supracondylar fractures above total knee arthroplasties using the intramedullary supracondylar rod. Clin Orthop 1994;302:194-198.

Question 10

Which of the following nutraceuticals has been associated with perioperative bleeding?

Explanation

Ginkgo biloba is a popular nutraceutical for patients who have early dementia, intermittent claudication secondary to peripheral vascular disease, vertigo, and tinnitus. It is reported to improve mental alertness and cognitive deficiency. It has antiplatelet properties as a result of one of its components, ginkgolide B, which displaces platelet-activating factor from its receptor binding sight. Rowin and Lewis reported on spontaneous bilateral subdural hematomas associated with chronic ginkgo biloba ingestion. Vale also reported on subarachnoid hemorrhage associated with ginkgo biloba. Bebbington and associates reported on persistent postoperative bleeding after total hip arthroplasty secondary to ginkgo biloba usage. Furthermore, the use of ginkgo biloba with aspirin or other antiplatelet agents or anticoagulants represents a relative contraindication. Physicians should be aware not only of prescribed medications but also alternative nutraceuticals that are used by the patient. Rowin J, Lewis SL: Spontaneous bilateral subdural hematomas associated with chronic ginkgo biloba ingestion. Neurology 1996;46:1775-1776. Vale S: Subarachnoid hemorrhage associated with ginkgo biloba. Lancet 1998;352:36.

Question 11

A 64-year-old man undergoes a primary total knee arthroplasty. Three months after surgery he reports persistent pain, weakness, and difficulty ambulating. Postoperative radiographs are shown in Figures 6a through 6c. What is the best course of action at this time?

Explanation

6b 6c The Merchant view reveals subluxation of the patellar component. The etiology of maltracking of the patella includes internal rotation of the femoral component, internal rotation of the tibial component, excessive patellar height, and lateralization of the patella component. The treatment of choice in this patient is revision total knee arthroplasty with external rotation of the femoral component. Preoperatively the patient also may require a lateral release, revision of the tibial component if it is internally rotated, and possibly a soft-tissue realignment. Component malalignment needs to be addressed first. Kelly MA: Extensor mechanism complications in total knee arthroplasty. Instr Course Lect 2004;53:193-199. Malkani AL, Karandikar N: Complications following total knee arthroplasty. Sem Arthroplasty 2003;14:203-214.

Question 12

Compared to metal-on-polyethylene total hip bearing surfaces, the debris particles generated by metal-on-metal articulations are

Explanation

Retrieval studies have shown that the debris particles produced by metal-on-metal articulations in total hip arthroplasty are several orders of magnitude smaller and may be up to 100 times more numerous than those found with metal-on-polyethylene articulations. Davies AP, Willert HG, Campbell PA, et al: An unusual lymphocytic perivascular infiltration in tissues around contemporary metal-on-metal joint replacements. J Bone Joint Surg Am 2005;87:18-27.

Question 13

A 60-year-old patient had the procedure shown in Figure 7 performed 5 years ago. When converting this patient to a total knee arthroplasty (TKA), what patellar problem is commonly encountered intraoperatively?

Explanation

Patella baja is commonly encountered when converting a high tibial osteotomy (HTO) to a TKA. Patella baja most likely occurs because of scarring. Meding and associates' study did not show an increased rate of lateral release when converting a knee that had undergone a previous HTO. Yoshino N, Shinro T: Total knee arthroplasty after failed high tibial osteotomy, in Callaghan JJ, Rosenberg AG, Rubash HE, et al (eds): The Adult Knee. Philadelphia, PA, JB Lippincott, 2003, vol 2, pp 1265-1271.

Question 14

Antibiotic-loaded bone cement prostheses, such as that shown in Figure 8, are best created by using which of the following methods?

Explanation

In a review of the practical applications of antibiotic-loaded bone cement for the treatment of the infected total joint arthroplasties, Hanssen and Spangehl described commercially available antibiotic-loaded bone cement as low-dose antibiotic cements. These cements generally contained 0.5 g of either tobramycin or gentamicin per 40 g of cement. They are indicated for use in prophylaxis and not for treatment of infected total joint arthroplasties. High-dose antibiotic-loaded bone cements are described as those containing greater than 1.0 g of antibiotic per 40 g of cement. Effective elution levels have been documented with 3.6 g tobramycin and 1.0 g vancomycin per 40 g of bone cement. This was documented by Penner and associates. Furthermore, it was shown that the combination of the two antibiotics in the bone cement improved the elution of both antibiotics. Hanssen AD, Spangehl MJ: Practical applications of antibiotic-loaded bone cement for treatment of infected joint replacements. Clin Orthop 2004;427:79-85.

Question 15

Figures 9a and 9b show the radiographs of a 75-year-old man who underwent a revision total knee arthroplasty with a long-stemmed tibial component. In rehabilitation, he reports fullness and tenderness in the proximal medial leg (at the knee). The strategy that would best limit this postoperative problem is use of

Explanation

9b The problem with this reconstruction is the medial protrusion of the base plate. The use of a base plate with an offset stem can prevent the protrusion and thus the impingement and pain. Allograft bone or smoothing the outline with cement would be just as prominent and likely to cause pain. An ingrowth surface may improve soft-tissue attachment but would still leave the implant protruding medially and likely to cause pain. A nonstemmed tibial base plate would lead to less medial protrusion but at the expense of a smaller area for load carriage on the proximal tibia.

Question 16

Figure 10 shows the AP radiograph of an ambulatory 76-year-old patient. What is the most appropriate surgical treatment option for this patient?

Explanation

The patient has a periprosthetic fracture around a loose cemented femoral component. The proximal bone stock is poor; therefore, this fracture may be categorized as Vancouver 3-B. Hip arthrodesis and resection arthroplasty provide suboptimal results, particularly for ambulatory patients. Although impaction allografting may be an option to restore the bone stock in a younger patient, the latter procedure will be very difficult to perform when the proximal bone is poor in quality and fractured. Cementing another component into this wide femur is not an option. The best option for revision of the femoral component in this elderly patient is proximal femoral replacement arthroplasty. Malkani AL, Settecerri JJ, Sim FH, et al: Long-term results of proximal femoral replacement for non-neoplastic disorders. J Bone Joint Surg Br 1995;77:351-356.

Question 17

A 74-year-old woman has had acute medial right knee pain for the past 3 months. She denies any history of trauma or previous problems. Coronal and sagittal MRI scans are shown in Figures 11a and 11b. What is the most likely diagnosis?

Explanation

11b Spontaneous osteonecrosis of the medial femoral condyle is seen in the MRI scans, and is most common in women older than age 60 years. Although usually present in the weight-bearing portion of the medial femoral condyle, spontaneous osteonecrosis has also been described involving the lateral femoral condyle and patella. Most patients are seen postcollapse, and the treatment of choice is arthroplasty. Optimal treatment in precollapse stages is controversial. Kidwai AS, Hemphill SD, Griffiths HJ: Spontaneous osteonecrosis of the knee reclassified as insufficiency fracture. Orthopedics 2005;28:236,333-336. Soucacos PN, Xenakis TH, Beris AE, et al: Idiopathic osteonecrosis of the medial femoral condyle: Classification and treatment. Clin Orthop 1997;341:82-89.

Question 18

Patients with patellar clunk syndrome are best managed by which of the following methods?

Explanation

Patellar clunk syndrome is usually the result of a fibrous nodule that forms on the undersurface of the distal quadriceps tendon. It may get entrapped in the intercondylar notch of the femoral component during flexion, and lead to a sudden snap as the nodule is pulled out of the notch during active extension. Nonsurgical management is rarely successful. Surgical debridement is usually curative, with only rare recurrence. More aggressive procedures such as realignment, revision, or patellectomy are usually not necessary, and are reserved for cases resistant to soft-tissue debridement. Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, p 329. Diduch DR, Scuderi GR, Scott WN, et al: The efficacy of arthroscopy following total knee replacement. Arthroscopy 1997;13:166-171.

Question 19

Increasing articular conformity of the tibial polyethylene insert of a fixed-bearing total knee arthroplasty (TKA) prosthesis will have which of the following biomechanical effects?

Explanation

Increasing articular conformity increases the surface area for contact between the polyethylene and the femoral component. Advantages of this include lower peak contact stress within the polyethylene and less risk of polyethylene fatigue failure. Patellofemoral tracking is unchanged by increasing conformity unless gross component apposition is present. A potential disadvantage of increasing conformity includes some restriction in tibial rollback. Modest changes in conformity have not been shown to alter the rate of mechanical loosening. If conformity was increased to the extent of significant constraint, a potential increased risk of loosening would be expected, not a decrease. Design of modern TKAs includes a compromise in achieving enough constraint to lower polyethylene stress, without providing so much constraint as to limit kinematics and stress the fixation interfaces. D'Lima DD, Chen PC, Colwell CW Jr: Polyethylene contact stresses, articular congruity, and knee alignment. Clin Orthop 2001;392:232-238.

Question 20

A 63-year-old woman reports giving way of the knee and pain after undergoing primary total knee arthroplasty (TKA) 1 year ago. Examination reveals that the knee is stable in full extension but has gross anteroposterior instability at 90 degrees of flexion. The patient can fully extend her knee with normal quadriceps strength. Studies for infection are negative. AP and lateral radiographs are shown in Figures 12a and 12b, respectively. What is the appropriate management?

Explanation

12b The radiographs show posterior flexion instability that is the result of a flexion-extension gap imbalance and posterior cruciate ligament incompetence after a posterior cruciate ligament-retaining TKA. The femur is anteriorly displaced on the tibia, with lift-off of the femoral component from the tibial polyethylene. Revision to a larger femoral component will address the larger flexion gap relative to the extension gap, and a posterior stabilized implant will address the posterior cruciate ligament insufficiency. Pagnano and associates, reporting on a series of painful TKAs previously diagnosed as pain of unknown etiology, showed that the pain was secondary to flexion instability. Pain relief was achieved by revision to a posterior stabilized implant. Pagnano MW, Hanssen AD, Lewallen DG, et al: Flexion instability after primary posterior cruciate retaining total knee arthroplasty. Clin Orthop 1998;356:39-46. Fehring TK, Valadie AL: Knee instability after total knee arthroplasty. Clin Orthop 1994;299:157-162.

Question 21

A 72-year-old woman who underwent right total hip arthroplasty 7 years ago now reports right hip pain and limb shortening. Studies for infection are negative. AP and lateral radiographs are shown in Figures 13a and 13b. What is the most appropriate management?

Explanation

13b Current literature supports the use of reinforcement cages for the reconstruction of failed, loosened acetabular components associated with major bone loss as seen in this patient. Although results of revision using the so-called jumbo cup with screws generally have been good, the amount of bone loss and medial wall penetration shown here and the likelihood of pelvic discontinuity precludes the use of that technique. With either technique, bone grafting of remaining defects is recommended. Sporer SM, O'Rourke M, Paprosky WG: The treatment of pelvic discontinuity during acetablular revision. J Arthroplasty 2005;20:79-84.

Question 22

What is the most prevalent adverse event associated with allogeneic blood transfusion?

Explanation

Clerical error leading to acute hemolysis and even death occurs in 1:12,000 to 1:50,000 transfusions. Bacterial contamination leading to sepsis/shock occurs in 1:1 million transfusions. HIV transmission is approximately 1:500,000 transfusions and hepatitis C is 1:103,000 transfusions. Anaphylactic reactions occur in 1:150,000 transfusions. Aubuchon JP, Birkmeyer JD, Busch MP: Safety of the blood supply in the United States: Opportunities and controversies. Ann Intern Med 1997;127:904-909.

Question 23

At the time of the revision surgery shown in Figure 14, the acetabular component was found to be stable. Polyethylene exchange with a standard ultra-high molecular weight polyethylene liner and grafting was performed. The patient is at significantly increased risk for

Explanation

Maloney and associates reported a 35% increased risk of pelvic osteolysis after total hip arthroplasty with a porous-coated acetabular component without cement. All components were stable at the time of revision. Only liners were exchanged and debridement of the granuloma with or without bone graft was performed. No defects progressed and one third of the lesions were no longer visible on radiographs, regardless of bone grafting. Unfortunately, despite the technical ease of many of these types of revisions, the dislocation rate for these cases is significant. Precautions should be taken postoperatively, and patients should be educated about this risk preoperatively. Vaccaro AR (ed): Orthopaedic Knowledge Update 8. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2005, pp 411-424. Boucher HR, Lynch C, Young AM, et al: Dislocation after polyethylene liner exchange in total hip arthroplasty. J Arthroplasty 2003;18:654-657.

Question 24

What is the most frequent complication of both lateral closing wedge high tibial osteotomy and medial opening wedge osteotomy?

Explanation

Scuderi and associates reported on patellar height after a high tibial osteotomy. Eighty-nine percent of the patellae, as measured by the Insall-Salvati index, and 76.3 percent, as measured by the Blackburne-Peel index, were observed to be lowered. More recently, Wright and associates reported a 64% incidence of patella baja in patients undergoing a medial opening wedge osteotomy. The incidence of intra-articular fracture during medial opening wedge osteotomy has been reported to be as high as 11% by Hernigou and associates, whereas the incidence of intra-articular fracture during lateral closing wedge high tibial osteotomy has been reported to be 10% to 20% by Matthews and associates. The incidence of peroneal nerve palsy with a lateral closing wedge high tibial osteotomy ranges from 0% to 20%, according to Marti and associates, whereas the incidence of peroneal palsy following a medial opening wedge osteotomy has been reported to be 15.7% by Flierl and associates. The exact incidence of compartment syndrome after a high tibial osteotomy is not known; however, it does not reach the level of patella baja. The incidence of deep infection after a lateral closing wedge high tibial osteotomy ranges from 0% to 4% according to Billings and associates. Scuderi GR, Windsor RE, Insall JN: Observations on patellar height after proximal tibial osteotomy. J Bone Joint Surg Am 1989;71:245-248. Wright JM, Crockett HC, Slawski DP, et al: High tibial osteotomy. J Am Acad Orthop Surg 2005;13:279-289. Hernigou P, Medevielle D, Debeyre J, et al: Proximal tibial osteotomy for osteoarthritis with varus deformity: A ten to thirteen-year follow-up study. J Bone Joint Surg Am 1987;69:332-354. Matthews LS, Goldstein SA, Malvitz TA, et al: Proximal tibial osteotomy: Factors that influence the duration of satisfactory function. Clin Orthop 1988;229:193-200. Marti CB, Gautier E, Wachtl SW, et al: Accuracy of frontal and sagittal plane correction in open-wedge high tibial osteotomy. Arthroscopy 2004;20:366-372. Marti RK, Verhigan RA, Kerkhoffs GM, et al: Proximal tibial varus osteotomy: Indications, technique, and five to twenty-one-year results. J Bone Joint Surg Am 2001;83:164-170. Flierl S, Sabo D, Hornig K, et al: Open wedge high tibial osteotomy using fractioned drill osteotomy: A surgical modification that lowers the complication rate. Knee Surg Sports Traumatol Arthrosc 1996;4:149-153.

Question 25

Stiffness can occur following total knee arthroplasty. What is the most appropriate management for a patient who has deteriorating arc of motion after undergoing a revision knee arthroplasty 9 months ago?

Explanation

Stiffness following total knee arthroplasty can be a disabling condition. There are many reasons for loss of knee motion following total knee arthroplasty. Technical errors, such as overstuffing of the patella, malpositioning of the components, and ligamentous imbalance, are all known to result in stiffness following total knee arthroplasty. In some patients with a possible genetic predisposition, aggressive arthrofibrosis may develop and result in loss of knee motion. In any patient who has deteriorating knee motion, particularly after revision arthroplasty, deep infection should be ruled out. Although on occasion surgical intervention may be required to address knee stiffness, the outcome of revision surgery is poor if no reason for stiffness can be determined. Kim J, Nelson CL, Lotke PA: Stiffness after total knee arthroplasty: Prevalence of the complication and outcomes of revision. J Bone Joint Surg Am 2004;86:1479-1484.

Question 26

A 65-year-old female presents with an inability to actively extend her knee 3 years following a TKA. Radiographs show patella baja and a broken patellar component. What is the most reliable reconstructive option for a chronic patellar tendon rupture following TKA?

Explanation

Chronic patellar tendon ruptures after TKA have a notoriously high failure rate with primary repair. Reconstruction using an extensor mechanism allograft (such as an Achilles tendon allograft with a calcaneal bone block or synthetic mesh) is the preferred and most reliable surgical option for restoring active extension.

Question 27

A 70-year-old female with a history of a solid multi-level lumbar spine fusion (L2-S1) presents for right THA for primary osteoarthritis. What modification regarding acetabular component positioning should be considered to minimize the risk of dislocation, compared to a patient with a normal mobile lumbar spine?

Explanation

Patients with a fused or stiff lumbar spine fail to increase their pelvic tilt when transitioning from standing to sitting. Normally, posterior pelvic tilt during sitting increases functional acetabular anteversion, preventing anterior impingement and posterior dislocation. Because these patients have reduced spinopelvic mobility, the acetabular component should be placed in slightly more anteversion than the standard 'safe zone' to compensate for the lack of functional anteversion during sitting.

Question 28

Highly cross-linked polyethylene (HXLPE) has significantly reduced wear rates in total hip arthroplasty. Which of the following manufacturing processes, used to eliminate free radicals, decreases the mechanical strength and fracture toughness of the polyethylene?

Explanation

Remelting involves heating the polyethylene above its melting point to extinguish free radicals created during irradiation. While effective at reducing oxidation, remelting decreases the crystallinity of the polyethylene, thereby reducing its fatigue strength and fracture toughness. Annealing heats the polyethylene below its melting point, better preserving mechanical properties but leaving some free radicals. Vitamin E infusion quenches free radicals without the need for thermal treatment.

Question 29

During a primary TKA, a surgeon utilizes spacer blocks to assess gap kinematics after performing standard bone cuts. The extension gap is symmetric but tight, requiring significant force to insert the block. The flexion gap is symmetric and rectangular, and accepts the spacer block with 2 mm of balanced laxity. What is the most appropriate next step to achieve balanced gaps?

Explanation

The patient has a tight extension gap and an acceptable/balanced flexion gap. Resecting more distal femur will increase the extension gap without affecting the flexion gap. Resecting the proximal tibia would increase both gaps. Downsizing the femoral component or resecting more posterior femur would increase only the flexion gap.

Question 30

A 62-year-old male presents with groin pain 4 years after a primary metal-on-polyethylene THA. Radiographs show a well-fixed cementless acetabular shell and femoral stem. Laboratory testing reveals elevated serum cobalt levels (15 ppb) and mildly elevated chromium levels (2 ppb). A MARS MRI reveals a solid-cystic mass anterior to the hip joint. What is the most likely diagnosis?

Explanation

Elevated cobalt levels out of proportion to chromium (Co > Cr) in a metal-on-polyethylene THA are classic for mechanically assisted crevice corrosion (MACC) at the modular head-neck taper (trunnionosis). This can lead to an adverse local tissue reaction (ALTR), presenting as pain and a solid or cystic mass on MRI, mimicking a metal-on-metal pseudotumor but occurring at the trunnion.

Question 31

A 68-year-old female undergoes TKA for severe valgus osteoarthritis using a measured resection technique. After the distal femoral and proximal tibial cuts are made, the extension gap is rectangular. In flexion, the gap is asymmetric, being significantly tighter laterally than medially. Which of the following technical errors most likely occurred?

Explanation

Internal rotation of the femoral component moves the posterior lateral condyle relatively more distal/posterior, which decreases the size of the lateral flexion gap. In valgus knees, the lateral femoral condyle is often hypoplastic. If the surgeon sets femoral rotation at a standard 3 degrees of external rotation off the posterior condylar axis without accounting for this hypoplasia, it effectively leads to internal rotation of the femoral component relative to the surgical transepicondylar axis, resulting in a tight lateral flexion gap.

Question 32

A 78-year-old female sustains a fall 5 years after an uncemented primary THA. Radiographs reveal a spiral fracture of the proximal femur originating near the tip of the stem. The stem is radiographically loose and has subsided 5 mm. There is excellent bone stock distal to the fracture. According to the Vancouver classification, what is the most appropriate surgical management?

Explanation

This scenario describes a Vancouver B2 periprosthetic fracture (fracture around or just below the stem, with a loose stem, but adequate distal bone stock). The standard of care for Vancouver B2 fractures is revision arthroplasty using a long, uncemented, diaphyseal-engaging stem (such as a fluted tapered stem) that bypasses the fracture site by at least two cortical bone diameters.

Question 33

A 65-year-old male presents with acute onset of knee pain, swelling, and wound drainage 3 weeks after a primary TKA. Inflammatory markers are elevated. Knee aspiration yields 65,000 WBC/µL with 92% neutrophils. Cultures subsequently grow Staphylococcus aureus. Radiographs confirm the implants are well-fixed. What is the most appropriate surgical treatment?

Explanation

The patient has an acute post-operative periprosthetic joint infection (typically defined as occurring within 4 weeks of surgery). For acute post-operative infections with well-fixed implants and appropriate soft tissue coverage, Debridement, Antibiotics, and Implant Retention (DAIR) with modular polyethylene exchange is the standard of care.

Question 34

During a direct anterior approach for total hip arthroplasty, the surgeon develops the superficial internervous plane. Which of the following neurological structures is at greatest risk of injury during this specific stage of the dissection?

Explanation

The direct anterior approach (Smith-Petersen) utilizes the internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). The lateral femoral cutaneous nerve (LFCN) crosses this interval superficially and is at high risk of stretch or transection during the approach, which can lead to meralgia paresthetica.

Question 35

A 72-year-old male undergoes a primary total knee arthroplasty. Intraoperatively, the surgeon notes that the patella tracks laterally and tends to subluxate during flexion. Which of the following intraoperative technical errors is the most likely cause of this finding?

Explanation

Internal rotation of the femoral component and/or internal rotation of the tibial component increases the Q-angle, leading to lateral patellar tracking and potential subluxation. Internal rotation of the femoral component displaces the trochlear groove medially, exacerbating lateral tracking. To improve patellar tracking, the surgeon can externally rotate the femoral or tibial components, medialize the patellar component, or lateralize the femoral/tibial components.

Question 36

A 65-year-old female presents with a painful catching sensation when actively extending her knee from a flexed position, 1 year after undergoing a total knee arthroplasty (TKA). Operative reports indicate she received a posterior-stabilized implant. Which of the following is the most likely cause of her symptoms?

Explanation

Patellar clunk syndrome is a known complication most commonly associated with posterior-stabilized (PS) TKA designs. It is caused by the formation of a fibrous nodule at the superior pole of the patella or within the quadriceps tendon. During active extension from a flexed position (usually around 30-45 degrees), this nodule catches in the femoral intercondylar box and then 'clunks' out, causing pain and a catching sensation.

Question 37

A 72-year-old male is undergoing primary total hip arthroplasty (THA). Preoperative standing and sitting lateral radiographs reveal a fused lumbar spine from L2 to the sacrum, with no change in pelvic tilt between positions. Which of the following adjustments to the acetabular component position is recommended to minimize the risk of posterior dislocation when the patient sits?

Explanation

In a patient with a stiff lumbar spine, the pelvis fails to roll posteriorly (retrovert) when transitioning from standing to sitting. Normally, this posterior pelvic tilt dynamically increases functional acetabular anteversion, allowing clearance for hip flexion. A stiff spine removes this compensatory mechanism, significantly increasing the risk of anterior impingement and subsequent posterior dislocation during sitting. To compensate, the surgeon should implant the cup with increased anteversion and inclination (while remaining within safe zones) to mimic the missing dynamic clearance.

Question 38

In the manufacturing of highly cross-linked polyethylene (HXLPE) for total hip arthroplasty, the material is subjected to irradiation followed by thermal treatment (remelting or annealing). Compared to annealing, the remelting process has which of the following effects on the polyethylene?

Explanation

Remelting HXLPE (heating it above its melting point) effectively eliminates residual free radicals created during irradiation, significantly improving oxidation resistance compared to annealing (heating below the melting point). However, the remelting process permanently decreases the crystallinity of the polyethylene. This loss of crystallinity leads to a reduction in its mechanical properties, including decreased yield strength, ultimate tensile strength, and fatigue crack propagation resistance.

Question 39

A 68-year-old female undergoes a right TKA for severe valgus osteoarthritis with a 20-degree valgus deformity and a 15-degree flexion contracture. Postoperatively in the recovery room, she is noted to have a dense foot drop and numbness over the dorsum of her right foot. Which of the following is the most appropriate initial management?

Explanation

Peroneal nerve palsy is a dreaded complication following TKA for severe valgus and flexion deformities. It occurs due to traction/stretching of the nerve as the contracted lateral structures are corrected into extension and neutral alignment. The most critical initial step is to remove all compressive dressings (e.g., ACE wraps, continuous passive motion straps) and slightly flex the knee to relieve mechanical tension on the nerve. Immediate exploration is rarely indicated. EMG is useful only after 3 to 6 weeks if symptoms do not improve.

Question 40

During a total knee arthroplasty, the surgeon inadvertently places the femoral component in excessive internal rotation relative to the epicondylar axis. Which of the following biomechanical consequences is most likely to occur?

Explanation

Internal rotation of the femoral component in a TKA has two primary negative effects. First, it medializes the femoral trochlear groove, which effectively increases the Q-angle and leads to lateral patellar maltracking. Second, it shifts the posterior medial condyle distally/posteriorly relative to the lateral condyle, resulting in a tight medial flexion gap and a loose lateral flexion gap.

Question 41

A 55-year-old active male who underwent a total hip arthroplasty with a ceramic-on-ceramic bearing 3 years ago presents with an audible squeaking noise from his hip during deep flexion activities. He reports no pain, and serial radiographs show well-fixed components with no signs of osteolysis. Which of the following is the most significant biomechanical risk factor for this squeaking phenomenon?

Explanation

Squeaking is a well-documented phenomenon unique to hard-on-hard bearings, particularly ceramic-on-ceramic THA. The most significant biomechanical risk factor is edge loading, which often occurs secondary to acetabular component malposition (such as excessive inclination or inappropriate anteversion causing impingement and lift-off). Edge loading disrupts the critical fluid-film lubrication, causing the ceramic surfaces to rub directly against each other, creating a stripe of wear and a high-frequency squeaking sound.

Question 42

The direct anterior approach (DAA) for total hip arthroplasty has gained popularity due to its use of a true internervous and intermuscular plane. When compared to the posterior approach, the DAA is associated with a higher incidence of which of the following complications?

Explanation

The direct anterior approach utilizes the Hueter interval between the tensor fasciae latae (innervated by the superior gluteal nerve) and the sartorius (innervated by the femoral nerve). The lateral femoral cutaneous nerve (LFCN) courses superficially over the anterior aspect of the thigh and is at high risk of stretch or transection during this approach, leading to meralgia paresthetica. The posterior approach is historically associated with a higher risk of posterior dislocation, while the DAA has higher rates of LFCN injury and intraoperative proximal femoral fractures.

Question 43

A 70-year-old male presents with chronic pain and swelling in his left knee 2 years after a primary TKA. Joint aspiration yields synovial fluid with a white blood cell (WBC) count of 4,500 cells/μL and 85% polymorphonuclear leukocytes (PMNs). According to the 2018 International Consensus Meeting (ICM) criteria, which of the following additional findings would definitively confirm the diagnosis of a periprosthetic joint infection (PJI) without requiring further minor criteria?

Explanation

According to the 2018 ICM criteria for Periprosthetic Joint Infection (PJI), the presence of one of two major criteria is definitively diagnostic of PJI: 1) Two positive periprosthetic cultures with phenotypically identical organisms, or 2) A sinus tract communicating with the joint. The other options (elevated serum CRP/ESR, positive leukocyte esterase, positive alpha-defensin, elevated synovial WBC count/PMN %) are minor criteria, which must be tallied to reach a score of 6 or greater to confirm the diagnosis when a major criterion is absent.

Question 44

A 62-year-old female presents with groin pain and a feeling of fullness in her hip 6 years after a THA utilizing a metal-on-polyethylene bearing with a large (36 mm) cobalt-chromium femoral head on a titanium alloy stem. Laboratory testing reveals elevated serum cobalt levels, while chromium levels are normal. MRI with metal artifact reduction sequence (MARS) shows a thick-walled cystic mass adjacent to the greater trochanter. What is the most likely diagnosis?

Explanation

The clinical scenario is classic for mechanically assisted crevice corrosion (MACC), also known as trunnionosis, occurring at the modular head-neck junction. This complication is particularly prevalent when utilizing large diameter cobalt-chromium heads on titanium stems. The corrosion releases cobalt ions (resulting in elevated serum cobalt disproportionate to chromium) and triggers an adverse local tissue reaction (ALTR) or pseudotumor, visible on MARS MRI as a cystic or solid periarticular mass.

Question 45

During a primary total knee arthroplasty, the surgeon inadvertently elevates the joint line by 6 mm while balancing the flexion and extension gaps. How does this intraoperative error affect the knee's extensor mechanism and postoperative kinematics?

Explanation

Elevating the joint line in TKA results in a condition known as pseudo-patella baja (or relative patella baja). Because the distance from the patella to the tibial tubercle is fixed by the length of the patellar tendon, raising the articular surface of the femur and tibia effectively lowers the patella relative to the new joint line. This mismatch increases patellofemoral contact forces, can cause anterior knee pain, limits postoperative range of motion (reduced flexion), and may cause impingement of the patella against the anterior tibial polyethylene tray.

Question 46

A 68-year-old man presents with recurrent posterior instability of his THA. He has a history of L5-S1 fusion prior to his THA. What is the most likely biomechanical cause of his recurrent instability?

Explanation

Patients with stiff spinopelvic segments (e.g., prior lumbar fusion) lack the normal posterior pelvic tilt that occurs when moving from standing to sitting. Normally, posterior pelvic tilt increases functional anteversion to accommodate hip flexion and prevent anterior impingement. In patients with a stiff spine, the pelvis fails to tilt posteriorly during sitting, leaving the cup relatively retroverted and the hip prone to anterior impingement and posterior dislocation.

Question 47

A 72-year-old female presents 4 weeks after primary TKA with increasing knee pain, swelling, and erythema. Synovial fluid aspiration shows 45,000 WBCs/mcL with 92% PMNs. Cultures grow methicillin-sensitive Staphylococcus aureus (MSSA). Which of the following surgical interventions is most appropriate for this acute periprosthetic joint infection?

Explanation

This patient presents with an acute early periprosthetic joint infection (<90 days postoperatively, often defined as <4 weeks in classic literature). According to standard guidelines, DAIR with modular component (polyethylene) exchange is indicated for acute infections with a known, susceptible organism, stable implants, and an adequate soft tissue envelope.

Question 48

A 65-year-old male presents with groin pain 6 years after a primary THA using a metal-on-polyethylene bearing. Aspiration is negative for infection. MRI with metal artifact reduction sequence (MARS) shows a large solid pseudotumor adjacent to the hip joint. Cobalt levels are markedly elevated, while chromium levels are minimally elevated. What is the most likely diagnosis?

Explanation

An elevated cobalt level that is disproportionately higher than the chromium level (often > 3:1 ratio), along with a pseudotumor (ALTR) in the setting of a metal-on-polyethylene bearing, is classic for trunnionosis. This occurs due to mechanically assisted crevice corrosion at the modular head-neck junction. Metal-on-metal bearing wear typically produces more equal elevations of cobalt and chromium.

Question 49

A 68-year-old woman presents with an inability to actively extend her knee 3 years following a primary TKA. Radiographs demonstrate a high-riding patella with an intact tibial tubercle. Which of the following is the most reliable reconstructive option to restore extensor mechanism function?

Explanation

Rupture of the patellar tendon following TKA is a devastating complication. Direct primary repair has a very high failure rate and is generally not recommended. Reconstruction with a synthetic mesh (such as Marlex mesh) or a whole extensor mechanism allograft are the most reliable current options, with synthetic mesh showing excellent functional results and fewer risks of disease transmission or late allograft failure compared to allografts.

Question 50

During total hip arthroplasty performed through a posterior approach, the surgeon aims to place the acetabular component in the classic "Lewinnek safe zone." What are the target angles for inclination and anteversion?

Explanation

The classic Lewinnek safe zone for acetabular component positioning is 40° +/- 10° of inclination (abduction) and 15° +/- 10° of anteversion. Placement outside this zone has historically been associated with an increased risk of dislocation, though recent literature emphasizes the importance of spinopelvic mobility in functional component positioning.

Question 51

Following the implantation of trial components during a TKA, the surgeon notices that the patella tends to tilt and subluxate laterally during knee flexion. Which of the following adjustments to the components would exacerbate this problem?

Explanation

Lateral patellar subluxation is caused by an increased Q-angle or component malrotation. Internal rotation of the tibial component lateralizes the tibial tubercle relative to the femur, increasing the Q-angle and exacerbating lateral patellar tracking. External rotation of the femoral and tibial components, and medialization of the patellar button generally improve patellar tracking.

Question 52

Which of the following sterilization methods for ultra-high molecular weight polyethylene (UHMWPE) is most strongly associated with late oxidative degradation and accelerated wear in total joint arthroplasty?

Explanation

Historically, sterilizing UHMWPE by gamma irradiation in the presence of oxygen (air) generated free radicals that combined with oxygen, causing oxidative degradation over time. This led to embrittlement, delamination, and accelerated wear. Modern highly cross-linked polyethylenes are irradiated to induce cross-linking, melted or annealed to extinguish free radicals, and sterilized in a vacuum or inert gas to prevent oxidation.

Question 53

During a posterior-stabilized TKA, the knee is found to be symmetrically tight in flexion and well-balanced in extension. Which of the following modifications is the most appropriate step to balance the knee?

Explanation

A knee that is symmetrically tight in flexion and balanced in extension has an isolated tight flexion gap. Downsizing the femoral component reduces the posterior condylar offset, thereby increasing the flexion gap without affecting the extension gap. Recutting the distal femur would increase the extension gap. Decreasing the posterior tibial slope would further tighten the flexion gap.

Question 54

A 45-year-old active male underwent a metal-on-metal hip resurfacing 6 weeks ago. He now complains of sudden onset groin pain and inability to bear weight. Radiographs show a femoral neck fracture. Which of the following is the most significant intraoperative risk factor for this complication?

Explanation

Femoral neck fracture is a well-known early complication of hip resurfacing arthroplasty. The most significant surgical risk factor is varus malalignment of the femoral component, which significantly increases sheer stress on the femoral neck. Other risk factors include superior femoral neck notching, female gender, poor bone quality, and unrecognized osteonecrosis.

Question 55

When performing a total knee arthroplasty using an extramedullary (EM) femoral alignment guide, which anatomic landmark is essential for determining the proximal point of the mechanical axis of the femur?

Explanation

The mechanical axis of the femur is defined as a line drawn from the center of the femoral head to the center of the knee joint. When using an extramedullary guide or computer navigation without intramedullary access, identifying the center of the femoral head is critical to accurately reproduce the mechanical axis and ensure proper coronal alignment of the femoral component.

Question 56

A 55-year-old active man underwent a total hip arthroplasty (THA) with a ceramic-on-ceramic bearing 3 years ago. He presents with a new onset of audible squeaking from the hip during activity, without significant pain. Radiographs demonstrate a well-fixed implant with cup anteversion of 10 degrees and an abduction angle of 55 degrees. What is the most likely pathophysiologic cause of the squeaking?

Explanation

Ceramic-on-ceramic bearings have very low wear rates but can be associated with audible squeaking. Squeaking is strongly correlated with component malposition, specifically high abduction angles (vertical cups) and extremes of anteversion, which lead to edge loading, stripe wear, and microseparation.

Question 57

A 68-year-old woman presents 1 year after a primary posterior-stabilized total knee arthroplasty (TKA) with complaints of the knee 'giving way' when going down stairs and rising from a low chair. On examination, the knee has a range of motion of 0 to 130 degrees. The knee is stable to varus and valgus stress at 0 degrees but has marked anteroposterior translation at 90 degrees of flexion. Radiographs show a well-fixed prosthesis. What is the most likely surgical error that caused her symptoms?

Explanation

Flexion instability is characterized by a stable knee in extension but gross instability in flexion. This typically results from an oversized flexion gap relative to the extension gap. Common causes include undersizing the femoral component (leading to excessive posterior femoral resection) or an excessive posterior tibial slope.

Question 58

A 62-year-old man who underwent a posterior-stabilized TKA 9 months ago presents with an anterior knee catch and an audible 'clunk' when extending his knee actively from 45 degrees of flexion to full extension. What is the primary pathophysiologic mechanism of this complication?

Explanation

Patellar clunk syndrome typically occurs after posterior-stabilized TKA and is caused by the formation of a fibrosynovial nodule at the superior pole of the patella. During knee flexion, the nodule engages the intercondylar box of the femoral component. As the knee extends, the nodule forcibly pops out of the box (typically between 30 to 45 degrees of flexion), producing a palpable and audible clunk.

Question 59

A 72-year-old man is evaluated for a painful total hip arthroplasty placed 4 years ago. Inflammatory markers show an ESR of 45 mm/hr and a CRP of 22 mg/L. Joint aspiration yields synovial fluid with a white blood cell (WBC) count of 4,500 cells/µL and 85% polymorphonuclear neutrophils (PMNs). An alpha-defensin test is positive. According to the MSIS criteria, what is the most appropriate next step in management?

Explanation

The patient meets the criteria for a chronic periprosthetic joint infection (PJI), demonstrated by elevated inflammatory markers, positive alpha-defensin, and synovial WBC >3000 cells/µL with >80% PMNs. For a chronic PJI (diagnosed years after index surgery), the gold standard treatment in North America is a two-stage exchange arthroplasty. DAIR is contraindicated because the biofilm is fully mature.

Question 60

A 55-year-old man presents with isolated medial compartment osteoarthritis of the knee and is considering a medial unicompartmental knee arthroplasty (UKA). Which of the following is considered an absolute contraindication to performing a medial UKA?

Explanation

Absolute contraindications to unicompartmental knee arthroplasty (UKA) include inflammatory arthropathy (such as rheumatoid arthritis), as the disease process inherently involves the entire joint. ACL deficiency was traditionally a strict contraindication but is now considered relative. Age, moderate obesity, and correctable varus deformities up to 15 degrees are acceptable indications.

Question 61

A 65-year-old woman presents with worsening groin pain and swelling 5 years after a primary THA utilizing a dual-mobility construct with a cobalt-chromium (CoCr) modular neck and titanium stem. MRI with metal artifact reduction sequence (MARS) demonstrates a thick-walled cystic mass communicating with the joint space. Laboratory evaluation shows highly elevated serum cobalt levels with normal chromium. What is the primary mechanism of implant failure in this patient?

Explanation

The scenario describes trunnionosis or mechanically assisted crevice corrosion (MACC) at the modular neck-stem junction, leading to an adverse local tissue reaction (ALTR) or pseudotumor. This is particularly noted in mixed-metal modular junctions (e.g., CoCr neck on Ti stem). The elevated serum cobalt levels further isolate MACC of the CoCr component as the source.

Question 62

An 80-year-old woman falls and sustains a periprosthetic femur fracture 10 years after a cemented THA. Radiographs show a transverse fracture around the tip of the stem. The stem demonstrates significant subsidence, and the cement mantle is fractured, but the proximal femoral bone stock remains robust. What is the most appropriate surgical management?

Explanation

The patient has a Vancouver B2 periprosthetic fracture, which is defined as a fracture around or just below the stem, with a loose implant, but with adequate remaining bone stock. The standard of care for a Vancouver B2 fracture is revision of the loose stem to a bypass stem (such as a long, extensively porous-coated or modular fluted tapered stem) that bypasses the fracture site by at least 2 cortical diameters.

Question 63

A 59-year-old woman is scheduled for a TKA. During her preoperative evaluation, she reports a severe allergic blistering reaction to cheap jewelry. Skin patch testing is positive for nickel. Which of the following femoral component materials is most appropriate for this patient to minimize the risk of a hypersensitivity reaction while maintaining optimal biomechanical wear?

Explanation

Patients with severe metal hypersensitivity, particularly to nickel, are at risk for complications if standard cobalt-chromium (CoCr) implants are used, as CoCr contains trace amounts of nickel. Oxidized zirconium (Oxinium) lacks nickel and is the preferred alternative bearing surface for the femoral component in TKA for patients with metal hypersensitivity. Titanium is an option but has inferior wear characteristics when articulating against polyethylene.

Question 64

A 72-year-old woman presents with persistent lateral hip pain and a positive Trendelenburg sign 2 years after a primary THA done via a direct lateral approach. An MRI demonstrates complete avulsion and severe fatty atrophy (Goutallier grade 4) of the gluteus medius and minimus tendons. Nonoperative management has failed. Which of the following surgical options offers the most reliable improvement in gait and pain?

Explanation

Chronic abductor deficiency with severe fatty infiltration (Goutallier grade 3 or 4) indicates irreversible muscle damage, making primary repair or allograft reconstruction prone to failure. A gluteus maximus or vastus lateralis muscle transfer is considered the most reliable option to restore dynamic abductor function and improve gait. Constrained liners address instability but do not restore active abduction.

Question 65

A 78-year-old man presents with knee pain and swelling 15 years after a primary TKA. Radiographs show significant eccentric wear of the polyethylene bearing. Intraoperatively, the polyethylene insert exhibits large flakes of material separated from the articular surface. Which wear mechanism is primarily responsible for this appearance?

Explanation

Delamination wear is characterized by large flakes of polyethylene separating from the articular surface. This is caused by subsurface fatigue due to cyclic loading and is historically associated with oxidation of the polyethylene (often seen in legacy gamma-irradiated-in-air polyethylene components). Abrasive wear involves scratching, while adhesive wear involves microscopic transfer of polyethylene to the metal surface.

Question 66

A 65-year-old male with end-stage medial compartment osteoarthritis of the knee is scheduled for a total knee arthroplasty (TKA). He underwent a closing wedge high tibial osteotomy (HTO) 15 years ago. Which of the following is the most likely anatomic challenge encountered during this TKA as a consequence of the prior HTO?

Explanation

Closing or opening wedge high tibial osteotomies often lead to secondary patella baja. This occurs either due to relative elevation of the joint line (in opening wedge) or scarring and contracture of the patellar tendon. This can make eversion of the patella and exposure during subsequent TKA extremely difficult, often requiring a more extensive surgical approach such as a tibial tubercle osteotomy.

Question 67

A 55-year-old woman undergoes a cementless total hip arthroplasty (THA) with a ceramic-on-ceramic bearing. One year postoperatively, she complains of an audible 'squeaking' sound with walking, though she is otherwise pain-free. Which of the following factors is most strongly associated with the development of squeaking in ceramic-on-ceramic THA?

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, microseparation, and component impingement. Acetabular component malposition, specifically retroversion or excessive inclination, leads to edge loading and the loss of fluid film lubrication, which produces the characteristic squeaking phenomenon. Neck-socket impingement can also cause squeaking by transferring metal onto the ceramic head.

Question 68

A 68-year-old man presents with a painful total hip arthroplasty 4 years after the index procedure. His ESR is 45 mm/hr and CRP is 2.5 mg/dL. A hip aspiration yields synovial fluid with a white blood cell count of 3,500 cells/µL and 85% neutrophils. Alpha-defensin testing is positive. According to the 2018 International Consensus Meeting (ICM) criteria, what is the next best step in management?

Explanation

The patient has a definitive chronic periprosthetic joint infection (PJI) based on elevated inflammatory markers, synovial WBC > 3,000 cells/µL, PMN > 80%, and a positive alpha-defensin test. For chronic PJI (symptoms > 3 weeks or occurring > 4 weeks postoperatively), a two-stage revision arthroplasty remains the gold standard in North America to completely eradicate the infection. DAIR is strictly indicated only for acute infections with well-fixed implants.

Question 69

A 72-year-old female undergoes a right total knee arthroplasty. During the trial reduction, the patella tracks laterally and tends to dislocate with deep flexion. The surgeon suspects component malrotation. Which of the following combinations of component positioning would most likely cause this patellar maltracking?

Explanation

Internal rotation of either the femoral or tibial components increases the Q-angle, exacerbating lateral patellar tracking. Internal rotation of the femoral component mediatizes the trochlear groove, while internal rotation of the tibial component lateralizes the tibial tubercle relative to the trochlea. Therefore, combined internal rotation of both components synergistically worsens lateral patellar subluxation.

Question 70

A 66-year-old man who underwent an L4-S1 posterior spinal fusion three years ago now requires a total hip arthroplasty for severe osteoarthritis. Which of the following biomechanical considerations is most critical when planning his acetabular component positioning to minimize the risk of posterior dislocation?

Explanation

Patients with prior lower lumbar and sacral fusions suffer from spinopelvic stiffness. Normally, when moving from a standing to a sitting position, the pelvis retroverts, effectively opening the acetabulum (increasing anteversion) to accommodate hip flexion without impingement. A stiff spine with a fixed anterior pelvic tilt prevents this compensatory retroversion. As a result, the patient is at a high risk for anterior impingement and subsequent posterior dislocation during hip flexion. Surgeons must typically increase the target anteversion of the acetabular cup to compensate for this lack of dynamic mobility.

Question 71

A 60-year-old male presents with persistent groin pain two years after a primary metal-on-polyethylene total hip arthroplasty. Radiographs show a well-fixed cementless stem and cup. Serum cobalt levels are markedly elevated, while serum chromium levels are within normal limits. Which of the following is the most likely underlying cause of his symptoms and laboratory findings?

Explanation

An isolated marked elevation of serum cobalt with normal or only slightly elevated chromium in a patient with a metal-on-polyethylene THA strongly suggests mechanically assisted crevice corrosion (MACC) at the head-neck junction, commonly referred to as trunnionosis. This corrosion primarily releases cobalt ions from the cobalt-chromium femoral head where it interacts with the titanium stem taper.

Question 72

When evaluating a patient for unicompartmental knee arthroplasty (UKA), which of the following is generally considered an acceptable indication rather than a contraindication?

Explanation

Modern criteria for medial unicompartmental knee arthroplasty (UKA) permit the procedure in the presence of asymptomatic, incidental patellofemoral chondromalacia or cartilage wear. Classic contraindications include inflammatory arthritis, an absent or incompetent ACL (which causes abnormal kinematics and early failure), fixed varus or valgus deformities that are not passively correctable, and flexion contractures greater than 15 degrees.

Question 73

A 65-year-old female undergoes total knee arthroplasty utilizing a posterior stabilized (PS) implant. During trial range of motion, the surgeon notes that the tibial post impinges on the anterior aspect of the femoral cam/box when the knee is brought into full extension. What is the most appropriate intraoperative step to correct this?

Explanation

Anterior impingement of the tibial post on the femoral box or cam in full extension with a posterior stabilized TKA is typically caused by excessive posterior tibial slope. Excessive slope effectively pitches the tibial post forward relative to the femur when the knee extends. Decreasing the posterior slope of the tibial cut or using an insert that corrects this will resolve the impingement.

Question 74

A 72-year-old woman is evaluated for a painful total hip arthroplasty. Radiographs demonstrate massive osteolysis around the acetabular component with 4 cm of superior migration. During revision surgery, a large cavitary and segmental bone defect is noted in the superior acetabulum with intact Kohler's line (Paprosky Type IIIA). Which of the following reconstruction methods is most appropriate to achieve durable, long-term fixation?

Explanation

Paprosky IIIA defects involve >30% bone loss with significant superior migration of the hip center (>3 cm) while Kohler's line remains intact. These severe defects are best managed with highly porous metal components and structural trabecular metal augments. This construct provides excellent immediate mechanical stability and the potential for long-term biologic fixation (osteointegration), which has proven superior to traditional anti-protrusio cages that rely purely on mechanical fixation.

Question 75

A 60-year-old patient presents 6 weeks after a primary total knee arthroplasty with complaints of stiffness. Her range of motion is 15 degrees to 75 degrees. Radiographs demonstrate that the prosthetic joint line is elevated by 8 mm compared to her preoperative films. Which of the following intraoperative technical errors is the most likely cause of this elevated joint line?

Explanation

Joint line elevation in TKA commonly occurs when the surgeon over-resects the distal femur. This widens the extension gap. To achieve stability in extension, the surgeon is then forced to use a thicker polyethylene insert. The combination of a resected distal femur and a thicker poly insert pushes the entire tibiofemoral articulation proximally, elevating the joint line. Under-resecting the proximal tibia further contributes to joint line elevation by failing to lower the base upon which the thick insert sits.

Question 76

A 45-year-old active man underwent a cementless total hip arthroplasty with a ceramic-on-ceramic bearing 3 years ago. He presents complaining of a new squeaking noise emanating from his hip during activities such as bending to tie his shoes or climbing stairs. He denies pain, feelings of instability, or constitutional symptoms. Radiographs show well-fixed components with no evidence of osteolysis. What is the most likely biomechanical cause of the squeaking in this patient?

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is a well-documented phenomenon. It is most strongly associated with edge loading of the bearing surfaces, which typically occurs due to suboptimal positioning of the acetabular component (such as excessive inclination or abnormal version) or due to component impingement. This leads to a loss of fluid film lubrication and high friction, producing the characteristic squeak. Since the patient is asymptomatic and radiographs show well-fixed components, aseptic loosening or catastrophic failure (fracture) are unlikely.

Question 77

During a primary total knee arthroplasty, a surgeon utilizes trial components to assess the gap kinematics. With the trials in place, the knee is well-balanced and symmetric in extension. However, the knee is symmetrically tight in 90 degrees of flexion, limiting the range of motion and preventing full flexion. Which of the following intraoperative maneuvers is the most appropriate next step to balance the knee?

Explanation

The clinical scenario describes a knee that is balanced in extension but tight in flexion (tight flexion gap, normal extension gap). To address a tight flexion gap without altering the extension gap, the surgeon must remove more bone from areas that articulate exclusively in flexion. Increasing the posterior slope of the tibial cut lowers the posterior tibia, effectively increasing the flexion gap while minimally affecting the extension gap. Alternatively, downsizing the femoral component using an anterior referencing system (which increases the posterior femoral resection) would also work, but posterior referencing preserves the posterior cut and would not increase the flexion gap. Releasing the posterior capsule or resecting more distal femur would alter the extension gap. Resecting more proximal tibia would equally enlarge both the flexion and extension gaps.

Question 78

A 65-year-old woman presents with persistent right hip pain 2 years after a primary total hip arthroplasty. Her erythrocyte sedimentation rate (ESR) is 45 mm/hr and C-reactive protein (CRP) is 2.5 mg/dL. Aspiration of the hip yields synovial fluid with a white blood cell (WBC) count of 3,500 cells/uL and 75% polymorphonuclear leukocytes (PMNs). According to recent guidelines, which of the following synovial fluid biomarkers provides the highest specificity for confirming the diagnosis of a periprosthetic joint infection (PJI)?

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to infection. It has been extensively studied and validated as a highly specific and sensitive biomarker for periprosthetic joint infection (PJI). While leukocyte esterase is a useful and inexpensive point-of-care test, alpha-defensin (measured via laboratory immunoassay) demonstrates superior specificity and is incorporated into the 2018 International Consensus Meeting (ICM) criteria as a major definitive marker for PJI.

Question 79

A 62-year-old woman presents 8 months after a primary posterior-stabilized total knee arthroplasty with a complaint of a painful 'catching' or 'popping' sensation in her knee. This reliably occurs as she extends her knee from a flexed position, specifically around 30 to 45 degrees of flexion. Physical examination reveals a palpable clunk during active extension. Radiographs show well-positioned components without loosening. What is the most appropriate definitive management for this condition?

Explanation

The patient is describing patellar clunk syndrome, a recognized complication following posterior-stabilized total knee arthroplasty. It is caused by the formation of a fibrous nodule at the superior pole of the patella. As the knee extends from deep flexion, this nodule catches in the intercondylar box of the femoral component, popping out with a palpable and painful 'clunk' at approximately 30-45 degrees of flexion. The definitive and most effective treatment is excision of the fibrotic nodule, which can be performed arthroscopically or open.

Question 80

A surgeon is performing a primary total hip arthroplasty using the direct anterior approach, utilizing the internervous plane between the tensor fasciae latae and the sartorius. During the superficial dissection, a sensory nerve crossing the operative field is inadvertently transected. Damage to this specific nerve will most likely result in sensory loss to which of the following dermatomal distributions?

Explanation

The direct anterior (Smith-Petersen) approach utilizes the internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). The lateral femoral cutaneous nerve (LFCN) is at significant risk during the superficial dissection of this approach, as it frequently branches across the operative field. Injury to the LFCN results in numbness, paresthesia, or dysesthesia over the anterolateral aspect of the thigh.

Question 81

A 72-year-old man is brought to the emergency department after sustaining a fall. He underwent a primary total knee arthroplasty 5 years ago. Radiographs reveal a displaced, short oblique supracondylar femur fracture located entirely proximal to the femoral component. The femoral component shows no radiographic signs of loosening and remains well-fixed. Which of the following is the most appropriate surgical treatment for this periprosthetic fracture?

Explanation

This is a Lewis-Rorabeck Type II periprosthetic distal femur fracture, characterized by a displaced fracture with a well-fixed femoral component. The standard of care for a Type II fracture is surgical stabilization, typically achieved with open reduction and internal fixation (ORIF) utilizing a locked lateral plate or a retrograde intramedullary nail (if the femoral component design allows for nail passage). Revision arthroplasty (e.g., distal femoral replacement) is generally reserved for Type III fractures, where the femoral component is loose.

Question 82

During a primary total hip arthroplasty, the surgeon opts to use a high-offset femoral stem, effectively increasing the femoral offset by 10 mm compared to the patient's native anatomy, while maintaining equal leg lengths. What is the primary biomechanical effect of this increase in femoral offset?

Explanation

Femoral offset is the horizontal distance from the center of rotation of the femoral head to the anatomical axis of the femur. Increasing the femoral offset increases the lever arm of the abductor mechanism. This restores or increases tension on the abductor musculature, which improves their mechanical advantage. As a result, less abductor muscle force is required to maintain a level pelvis during single-leg stance, which paradoxically decreases the overall joint reaction force across the hip joint. It also moves the femur laterally, reducing the risk of bony impingement and improving the range of motion.

Question 83

A 62-year-old woman is evaluated for persistent hip pain 8 years after receiving a metal-on-metal total hip arthroplasty. Radiographs reveal an acetabular inclination angle of 58 degrees. Laboratory testing demonstrates significantly elevated serum cobalt and chromium levels. Which of the following systemic conditions is a known, severe manifestation of cobalt toxicity (cobaltism) stemming from a failing metal-on-metal implant?

Explanation

Elevated serum cobalt levels from failing metal-on-metal implants can lead to systemic cobalt toxicity, or 'cobaltism.' This syndrome is characterized by a constellation of systemic effects, most notably a dilated cardiomyopathy, which can be fatal if the source is not removed. Other systemic manifestations of cobaltism include neuro-ocular toxicity (visual and hearing impairment), peripheral neuropathy, and thyroid dysfunction (hypothyroidism).

Question 84

A 55-year-old man presents with progressive groin pain and swelling in his left hip 6 years after a primary total hip arthroplasty utilizing a titanium stem, a modular cobalt-chromium (CoCr) femoral head, and a highly cross-linked polyethylene liner. An MRI with metal artifact reduction sequence (MARS) reveals a thick-walled cystic mass communicating with the joint space. Aspiration yields cloudy, sterile fluid. What is the primary pathophysiologic mechanism responsible for this presentation?

Explanation

The clinical scenario describes an adverse local tissue reaction (ALTR) or aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) occurring in a metal-on-polyethylene total hip arthroplasty. In the absence of a metal-on-metal bearing surface, this reaction is typically triggered by mechanically assisted crevice corrosion (MACC) and fretting at the modular head-neck junction (trunnionosis) between the titanium stem and CoCr head. The release of metal ions and wear debris incites a Type IV delayed hypersensitivity reaction, leading to pseudotumor formation and tissue necrosis.

Question 85

Periprosthetic osteolysis is the leading cause of late aseptic loosening following total joint arthroplasty, primarily driven by a biologic response to particulate wear debris. Following the phagocytosis of wear particles by macrophages, which of the following receptor-ligand interactions represents the terminal obligate pathway for the differentiation and activation of osteoclasts?

Explanation

The biologic cascade of periprosthetic osteolysis begins when macrophages phagocytose particulate wear debris (most commonly polyethylene). The activated macrophages release pro-inflammatory cytokines such as TNF-alpha, IL-1, and IL-6. These cytokines stimulate osteoblasts and other cells to upregulate Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL). The terminal and obligate step for osteoclastogenesis and subsequent bone resorption is the binding of RANKL to its receptor, RANK, which is located on the surface of osteoclast precursors. Osteoprotegerin (OPG) acts as a decoy receptor that binds to RANKL, inhibiting this process.

Question 86

A 45-year-old active male undergoes a primary total hip arthroplasty (THA). A ceramic-on-ceramic bearing is chosen. At 2-year follow-up, he complains of a squeaking noise from his hip during deep bending and walking. What is the most significant surgeon-controlled risk factor for this complication?

Explanation

Squeaking is a specific complication associated with ceramic-on-ceramic bearings. Risk factors include component malposition, specifically high acetabular cup inclination and/or version that leads to edge loading, loss of fluid film lubrication, and stripe wear. While patient factors (like high BMI or young age) play a role, surgeon-controlled factors primarily revolve around avoiding excessive inclination (>50 degrees) and malversion.

Question 87

A 65-year-old female presents with a painful catching sensation in her left knee 14 months after a posterior-stabilized total knee arthroplasty (TKA). She reports a 'clunk' that is both heard and felt when extending her knee from a flexed position, typically occurring between 30 and 45 degrees of flexion. Which of the following is the most likely etiology of her symptoms?

Explanation

Patellar clunk syndrome is characterized by a painful catch or clunk when extending the knee from a flexed position. It occurs in posterior-stabilized (PS) knee designs when a fibrovascular nodule develops at the superior pole of the patella and catches in the intercondylar notch of the femoral component. Treatment typically involves arthroscopic resection of the nodule.

Question 88

A 68-year-old male presents with a feeling of 'giving way' when descending stairs 1 year after a primary TKA. On examination, the knee is well-aligned, fully extends, and flexes to 125 degrees. There is a 2 mm symmetric opening to varus and valgus stress in extension. However, at 90 degrees of flexion, there is marked anterior-posterior translation and 6 mm of opening to varus and valgus stress. Which of the following surgical errors most likely contributed to this presentation?

Explanation

The patient is experiencing flexion instability, characterized by a balanced extension gap but a loose flexion gap. Undersizing the femoral component in the anteroposterior (AP) dimension (especially when using anterior referencing, which resects more posterior condyle) increases the flexion gap without affecting the extension gap, leading to isolated flexion instability.

Question 89

A 55-year-old male presents with groin pain and a progressive limp 6 years after an uncomplicated metal-on-polyethylene THA using a large-diameter cobalt-chromium head on a titanium stem. Radiographs show a well-fixed prosthesis. Aspiration yields fluid with a normal cell count and negative cultures. Serum cobalt levels are markedly elevated, while serum chromium levels are mildly elevated. What is the most likely source of the elevated metal ions?

Explanation

The clinical scenario describes trunnionosis, which involves fretting and crevice corrosion at the modular head-neck taper junction (trunnion). It is increasingly recognized in metal-on-polyethylene implants, particularly when large-diameter cobalt-chromium heads are used on titanium stems. This leads to disproportionately elevated serum cobalt levels compared to chromium and can cause an adverse local tissue reaction (ALTR).

Question 90

According to the 2018 International Consensus Meeting (ICM) criteria, which of the following findings serves as a definitive major criterion that firmly establishes the diagnosis of a periprosthetic joint infection (PJI)?

Explanation

According to the 2018 ICM criteria for PJI, the presence of a sinus tract communicating with the joint OR two positive periprosthetic cultures with phenotypically identical organisms are considered major criteria. Either of these is definitive evidence of PJI on its own. The other listed options represent minor criteria that must be scored cumulatively to reach a diagnosis.

Question 91

A surgeon is performing a primary THA using the direct anterior approach (Smith-Petersen) on a standard operating table. The internervous plane is developed between the tensor fasciae latae and sartorius. To safely expose the anterior joint capsule without causing a postoperative hematoma, which of the following vascular structures typically must be identified and ligated?

Explanation

During the direct anterior approach to the hip, the internervous plane between the sartorius (femoral nerve) and tensor fasciae latae (superior gluteal nerve) is utilized. Deeply, the plane is between the rectus femoris and gluteus medius. The ascending branches of the lateral circumflex femoral artery cross this interval horizontally and must be carefully cauterized or ligated to prevent substantial bleeding and hematoma formation.

Question 92

An 82-year-old female falls and sustains a periprosthetic fracture of the right femur around her cemented THA, which was placed 15 years ago. Radiographs reveal a spiral fracture around the tip of the stem. The stem appears subsided and loose, but there is adequate bone stock proximally and distally. According to the Vancouver classification, what is the most appropriate management?

Explanation

This is a Vancouver B2 periprosthetic femur fracture (fracture around the stem, loose stem, good bone stock). The gold standard treatment for a Vancouver B2 fracture is revision arthroplasty using a long uncemented, extensively porous-coated, or fluted tapered modular stem to bypass the fracture by at least two cortical diameters, combined with appropriate fracture fixation (e.g., cerclage cables) if necessary. ORIF alone is reserved for Vancouver B1 fractures (well-fixed stem).

Question 93

In a posterior-stabilized (PS) total knee arthroplasty, the interaction between the femoral cam and the tibial post is designed to substitute for a native ligamentous structure. What is the primary biomechanical function of this cam-post engagement?

Explanation

In a posterior-stabilized (PS) TKA, the cam on the femoral component engages the post on the tibial polyethylene insert during knee flexion. This mechanism substitutes for the resected posterior cruciate ligament (PCL). Its primary function is to enforce posterior femoral rollback (preventing anterior translation of the femur on the tibia) during deep flexion, which improves maximal flexion and optimizes the quadriceps lever arm.

Question 94

Elevation of the joint line during a revision total knee arthroplasty, which often occurs due to the use of an oversized femoral component and a thick tibial polyethylene insert to fill gaps, is most likely to result in which of the following specific complications?

Explanation

Elevating the joint line during TKA alters the kinematics of the knee. The distance from the tibial tubercle to the joint line decreases, leading to relative or 'pseudo' patella baja. This can result in impingement of the patella against the anterior tibial polyethylene or tibial tray, decreased range of motion, altered patellofemoral mechanics, and anterior knee pain.

Question 95

During preoperative templating for a total hip arthroplasty, the surgeon plans to increase the femoral offset by 10 mm compared to the contralateral normal hip, without changing the leg length. What is an expected biomechanical consequence of this planned alteration?

Explanation

Increasing femoral offset increases the lever arm of the abductor muscles, which decreases the force required by the abductors to maintain a level pelvis and decreases the overall joint reaction force (making A and B incorrect). However, excessive offset lateralizes the greater trochanter, increasing tension on the iliotibial band, which dramatically increases the risk of trochanteric bursitis. It also increases the bending moment (stress) on the femoral stem.

Question 96

A 62-year-old male presents with new-onset right groin pain and a sensation of fullness 6 years after undergoing a primary total hip arthroplasty. The implant utilizes a titanium stem, a cobalt-chromium modular head, and a highly cross-linked polyethylene liner. Radiographs show a well-fixed stem and cup with no evidence of osteolysis. Laboratory evaluation reveals a normal ESR and CRP, but serum cobalt levels are markedly elevated at 14 mcg/L, while serum chromium is normal at 1.5 mcg/L. What is the most likely diagnosis?

Explanation

The clinical scenario of a metal-on-polyethylene total hip arthroplasty with an elevated serum cobalt out of proportion to serum chromium is the hallmark of mechanically assisted crevice corrosion (MACC), also known as trunnionosis. This occurs at the modular head-neck junction. Metallosis from an adverse local tissue reaction (ALTR) can result, leading to groin pain and a cystic mass (pseudotumor) causing a sensation of fullness. Unlike metal-on-metal bearing wear, which typically presents with elevated levels of both cobalt and chromium, trunnionosis heavily favors cobalt elevation.

Question 97

In evaluating the kinematics of a cruciate-retaining (CR) total knee arthroplasty (TKA) compared to a native knee, which of the following kinematic patterns is most frequently observed during deep flexion?

Explanation

In a native knee, the femur undergoes posterior rollback during flexion, which is largely driven by the anterior cruciate ligament (ACL) and the geometry of the condyles. In a cruciate-retaining (CR) TKA, the ACL is sacrificed, and the posterior cruciate ligament (PCL) is retained. Because the intricate balance of the native ACL and joint geometry is altered, the femur commonly undergoes paradoxical anterior translation during mid-to-deep flexion instead of the native posterior rollback. This can lead to decreased maximal flexion and increased polyethylene wear.

Question 98

A 24-year-old female presents with symptomatic developmental dysplasia of the hip (DDH) characterized by a lateral center-edge angle of 15 degrees and a Tönnis angle of 18 degrees. She is scheduled to undergo a Bernese periacetabular osteotomy (PAO). Which of the following represents a primary biomechanical or structural advantage of the Bernese PAO compared to the Salter innominate osteotomy?

Explanation

The Bernese periacetabular osteotomy (PAO) involves a series of osteotomies (ischial, pubic, and iliac) that completely free the acetabulum while leaving the posterior column of the hemipelvis intact. This is a major advantage because it preserves intrinsic pelvic stability, allowing for earlier mobilization without the need for prolonged casting. Furthermore, because the posterior column is intact, it does not alter the shape or dimensions of the true pelvis, making it advantageous for women of childbearing age regarding future vaginal deliveries.

Question 99

An 82-year-old female sustains a mechanical fall 8 years following a primary total knee arthroplasty. Radiographs demonstrate a displaced periprosthetic distal femur fracture. Careful radiographic and clinical evaluation reveals that the femoral component is definitively loose and has migrated proximally. According to the Lewis-Rorabeck classification, which of the following is the most appropriate definitive management?

Explanation

This patient has a Lewis-Rorabeck Type III periprosthetic distal femur fracture, defined as a fracture with a loose prosthesis. The definitive management for a loose femoral component in the setting of a periprosthetic fracture is revision arthroplasty (utilizing stems, augments, or a distal femoral replacement depending on bone stock). Open reduction and internal fixation (ORIF) and retrograde nailing are appropriate for Lewis-Rorabeck Type II fractures, where the fracture is displaced but the prosthesis remains solidly fixed.

Question 100

During a direct anterior approach (DAA) for a primary total hip arthroplasty, the surgeon utilizes the Hueter interval to access the hip joint. Which of the following statements accurately describes the neurologic risk during the superficial dissection of this approach?

Explanation

The direct anterior approach (DAA) utilizes the true internervous Hueter interval between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve). The lateral femoral cutaneous nerve (LFCN) typically courses over the sartorius or in the fascial layer just medial to the tensor fasciae latae. It is at significant risk of iatrogenic injury (stretching or transection) during the superficial dissection and retractor placement. Surgeons must stay carefully within the fascial sleeve of the TFL to minimize LFCN injury.

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

Orthopedic Hip & Knee 2026 MCQs: Board Review Questions & Answers (Part 1)

Key Takeaway

Orthopedic Hip & Knee 2026 MCQs: Board Review Questions & Answers (Part 1)

Chapter Index