AAOS & ABOS Hip & Knee Reconstruction MCQs | Set 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

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

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

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

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

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

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

During a total knee arthroplasty, trial reduction reveals a tight extension gap and a loose flexion gap. Which of the following surgical maneuvers is the most appropriate next step to balance the knee?

Explanation

Resecting more distal femur increases the extension gap without affecting the flexion gap. This will correct a tight extension gap while maintaining the current loose flexion gap, allowing for subsequent balancing with an appropriately sized polyethylene insert.

Question 27

A 68-year-old patient with a metal-on-polyethylene total hip arthroplasty presents with new-onset groin pain 6 years postoperatively. Radiographs show well-fixed components with no signs of osteolysis. Laboratory testing reveals elevated serum cobalt levels with normal serum chromium levels. What is the most likely cause of these findings?

Explanation

Femoral head-neck taper corrosion (trunnionosis) typically presents with a disproportionately high serum cobalt level relative to chromium. In contrast, bearing surface wear in a metal-on-metal articulation usually presents with roughly equal or slightly higher chromium elevations.

Question 28

Understanding spino-pelvic mechanics is crucial for preventing instability after total hip arthroplasty. In a normal patient, transitioning from a standing to a seated position causes the pelvis to tilt posteriorly. How does this normal posterior pelvic tilt affect the orientation of the acetabulum?

Explanation

During the transition from standing to sitting, the normal pelvis tilts posteriorly. This dynamic movement causes the acetabulum to both antevert and incline, providing clearance for the flexing femur and preventing anterior impingement.

Question 29

During a primary total hip arthroplasty utilizing the direct anterior approach (Hueter interval), the surgeon must routinely identify and ligate an ascending arterial branch traversing the surgical field to prevent excessive bleeding. This vessel is a branch of which of the following arteries?

Explanation

The ascending branch of the lateral femoral circumflex artery regularly crosses the internervous plane between the tensor fasciae latae and the sartorius. It must be identified and cauterized or ligated early in the direct anterior approach.

Question 30

During the femoral preparation of a total knee arthroplasty, the surgeon inadvertently places the femoral component in internal rotation relative to the transepicondylar axis. This error will most likely result in which of the following postoperative biomechanical issues?

Explanation

Internal rotation of the femoral component medializes the trochlear groove, which effectively increases the Q-angle and leads to lateral patellar subluxation or tracking. It also creates a tight medial flexion gap.

Question 31

Highly cross-linked polyethylene (HXLPE) is used in modern arthroplasty to reduce volumetric wear. During its manufacturing, irradiation is typically followed by a thermal treatment such as remelting or annealing. What is the primary purpose of the remelting process?

Explanation

Irradiation of polyethylene generates free radicals that can oxidize in vivo, leading to material degradation and embrittlement. Remelting the polyethylene above its melting point extinguishes these free radicals, preventing long-term oxidative degradation.

Question 32

A 70-year-old female presents with a painful catching sensation in her knee one year after undergoing a posterior-stabilized total knee arthroplasty. The catch occurs during active extension from a flexed position of approximately 40 degrees. What is the most likely diagnosis?

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized total knee designs. It is caused by the formation of a fibrous nodule at the superior pole of the patella that catches in the intercondylar box of the femur during active extension.

Question 33

A 75-year-old female sustains a fall 8 years after an uncomplicated cementless total hip arthroplasty.

Radiographs demonstrate a fracture around the distal aspect of the stem. The stem demonstrates evidence of subsidence and loosening, but the proximal femoral bone stock remains adequate. Based on the Vancouver classification, what is the most appropriate definitive management?

Explanation

This describes a Vancouver B2 periprosthetic femur fracture, characterized by a fracture around a loose stem with adequate bone stock. The standard treatment is revision to a longer uncemented stem that bypasses the fracture by at least two cortical diameters.

Question 34

During a primary total knee arthroplasty, the trial components are placed. The surgeon notes that the knee is tight in flexion but symmetrically balanced in extension. Which of the following is the most appropriate next step to balance the knee?

Explanation

A tight flexion gap with a balanced extension gap is best managed by downsizing the femoral component or increasing the posterior tibial slope. Resecting more distal femur would inappropriately alter the already balanced extension gap.

Question 35

A 65-year-old female with a metal-on-polyethylene total hip arthroplasty presents with new-onset groin pain. Radiographs show well-fixed components. Laboratory evaluation reveals elevated serum cobalt levels and normal chromium levels. Inflammatory markers are normal. What is the most likely diagnosis?

Explanation

Elevated cobalt with normal chromium in the setting of a metal-on-polyethylene THA is highly characteristic of mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction.

Question 36

A patient with ankylosing spondylitis and a fused lumbar spine is planned for a THA. Spinopelvic mobility assessment demonstrates no change in pelvic tilt from standing to sitting. To prevent instability, how should the acetabular component positioning be adjusted?

Explanation

A stiff spinopelvic junction fails to dynamically increase acetabular anteversion during sitting, raising the risk of anterior impingement and posterior dislocation. The cup should be placed in increased anteversion and inclination to compensate for this stiffness.

Question 37

A 72-year-old female sustains a periprosthetic femur fracture around a cemented total hip arthroplasty. Radiographs reveal a fracture around the tip of the stem with radiolucent lines indicating a loose stem, but adequate femoral bone stock remains. According to the Vancouver classification, what is the most appropriate surgical management?

Explanation

This scenario describes a Vancouver B2 fracture (fracture around the stem, loose implant, good bone stock). The gold standard treatment is bypassing the fracture with a long, uncemented diaphyseal engaging revision stem.

Question 38

Four weeks following a primary total knee arthroplasty, a patient presents with sudden onset knee pain, erythema, and swelling. Synovial fluid analysis reveals a WBC count of 65,000 cells/uL with 92% neutrophils. Which of the following is the most appropriate initial surgical treatment?

Explanation

Acute periprosthetic joint infections occurring within 4 weeks of surgery or 3 weeks of hematogenous spread are best treated with open debridement, antibiotics, and implant retention (DAIR) along with a modular polyethylene exchange.

Question 39

Following a primary TKA, the surgeon observes that the patella subluxates laterally during deep knee flexion. Which of the following component malpositions is the most likely technical cause?

Explanation

Internal rotation of either the femoral or tibial components increases the Q-angle, which exacerbates lateral patellar maltracking. Correct external rotation of these components optimizes patellofemoral tracking.

Question 40

During a direct anterior approach for total hip arthroplasty, the surgeon develops the superficial surgical interval. Between which two nerve territories does this true internervous plane lie?

Explanation

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

Question 41

During a TKA for a patient with a 30-degree flexion contracture, the surgeon balances the flexion gap appropriately but finds the knee remains tight in extension despite adequate posterior capsular release. What is the most appropriate next step?

Explanation

A knee that is tight in extension but balanced in flexion requires enlargement of the extension gap only. Resecting additional distal femur achieves this isolated increase without altering the flexion gap.

Question 42

A 55-year-old active male with a ceramic-on-ceramic THA complains of an audible squeaking sound from his hip when walking. Which of the following is the most significant risk factor for this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, which often results from component malposition, such as a steeply abducted or excessively anteverted acetabular cup.

Question 43

During a primary posterior-stabilized total knee arthroplasty, trial components demonstrate a balanced and stable extension gap, but the knee is excessively tight in flexion. Which of the following is the most appropriate corrective action?

Explanation

Downsizing the femoral component decreases the anteroposterior dimension, selectively loosening the flexion gap. It does not affect the extension gap, making it the ideal correction for a knee that is tight in flexion but balanced in extension.

Question 44

A 65-year-old female presents with recurrent posterior dislocations following a primary total hip arthroplasty. Evaluation reveals a combined anteversion of 15 degrees. Which of the following is the primary mechanical cause of her instability?

Explanation

A combined anteversion of 15 degrees is abnormally low (retroverted). This leads to impingement of the anterior femoral neck against the anterior acetabular rim during flexion and internal rotation, levering the femoral head out posteriorly.

Question 45

A 60-year-old male presents with right hip pain 5 years after a metal-on-polyethylene THA. Aspiration yields a sterile effusion with normal inflammatory markers but an elevated serum cobalt level. MRI reveals a solid pseudotumor. What is the most likely source of the metal debris?

Explanation

In a metal-on-polyethylene THA with elevated cobalt and a pseudotumor, the source of metal ions is typically mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction.

Question 46

A 72-year-old patient sustains a periprosthetic femur fracture 10 years after a cementless THA. Radiographs show a fracture around the tip of the stem. The stem is radiographically loose, but the proximal bone stock is well preserved. According to the Vancouver classification, what is the most appropriate treatment?

Explanation

This is a Vancouver B2 fracture (fracture around the stem, loose stem, good proximal bone stock). The gold standard treatment is revision arthroplasty bypassing the fracture with a long diaphyseal-engaging stem.

Question 47

A 55-year-old male with a rigid lumbar spine fusion from L2 to the pelvis requires a primary THA. Compared to a patient with normal spinopelvic mobility, how should the acetabular component positioning be adjusted to minimize the risk of dislocation?

Explanation

A rigid lumbopelvic segment prevents compensatory posterior pelvic tilt during sitting. To prevent anterior impingement and subsequent posterior dislocation, the acetabular cup must be placed with increased anteversion and inclination.

Question 48

A patient presents 4 weeks post-TKA with acute onset of severe knee pain, erythema, and swelling. Synovial fluid aspiration shows 45,000 WBC/uL with 95% neutrophils. Which of the following is the most appropriate initial surgical management?

Explanation

For an acute postoperative periprosthetic joint infection (less than 90 days from index surgery), open debridement, antibiotics, and implant retention (DAIR) with modular component exchange is the treatment of choice.

Question 49

Which of the following implant design factors most significantly increases the risk of mechanically assisted crevice corrosion (trunnionosis) in a total hip arthroplasty?

Explanation

A larger femoral head diameter increases the lever arm and frictional torque at the modular head-neck junction. This exacerbates micromotion and increases the risk of trunnionosis.

Question 50

A patient who underwent a posterior-stabilized TKA one year ago complains of a painful "pop" when actively extending the knee from a flexed position. What is the most likely etiology of this symptom?

Explanation

This presentation is classic for patellar clunk syndrome, caused by a fibrous nodule forming on the superior pole of the patella that catches in the intercondylar box of a posterior-stabilized femoral component during extension.

Question 51

When utilizing the direct anterior approach for total hip arthroplasty, the internervous plane is established between muscles supplied by which of the following pairs of nerves?

Explanation

The direct anterior approach uses the internervous plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve).

Question 52

Highly cross-linked polyethylene is utilized in THA to reduce wear rates. What is the primary purpose of the post-irradiation melting or annealing process during its manufacture?

Explanation

Irradiation creates cross-links but also generates free radicals. Post-irradiation melting or annealing eliminates these residual free radicals, preventing in vivo oxidation and premature degradation of the polyethylene.

Question 53

A 65-year-old woman undergoes a total hip arthroplasty through a posterior approach. Postoperatively, she experiences recurrent posterior dislocations. Radiographs show the acetabular component is placed in 30 degrees of abduction and 5 degrees of retroversion. What is the primary cause of her posterior instability?

Explanation

The normal target for acetabular cup position is approximately 40 degrees of abduction and 15 to 20 degrees of anteversion. Retroversion heavily predisposes the hip to posterior dislocation, making insufficient anteversion the primary cause of instability in this patient.

Question 54

During a posterior-stabilized total knee arthroplasty, the posterior cruciate ligament is resected to accommodate the implant box. Which vascular structure is most directly at risk of injury during this specific step and frequently requires electrocautery?

Explanation

The middle genicular artery is a branch of the popliteal artery that enters the knee joint through the posterior capsule directly behind the posterior cruciate ligament. It is frequently encountered and requires cauterization during PCL resection.

Question 55

A 68-year-old woman presents with a painful catching sensation in her knee 9 months after a posterior-stabilized total knee arthroplasty. The catching occurs as she actively extends her knee from a flexed position, specifically around 30 to 40 degrees of flexion. What is the most likely etiology?

Explanation

Patellar clunk syndrome occurs in posterior-stabilized total knee arthroplasties when a fibrous nodule forms at the superior pole of the patella. This nodule catches in the intercondylar notch of the femoral component during extension from a flexed position.

Question 56

A 55-year-old man undergoes a total hip arthroplasty using a ceramic-on-ceramic bearing. Two years postoperatively, he complains of a loud, audible squeaking sound from his hip when walking. Which of the following factors is most strongly associated with this phenomenon?

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is highly associated with edge loading. This abnormal contact typically results from acetabular component malposition, leading to a loss of fluid film lubrication and high contact stresses.

Question 57

A 70-year-old man presents with a painful, swollen total knee arthroplasty 4 years after the index surgery. Radiographs show no component loosening. Aspiration of the knee yields synovial fluid with a white blood cell count of 15,000 cells/µL and 85% polymorphonuclear neutrophils. What is the most appropriate next step in management?

Explanation

A synovial WBC count > 3,000 cells/µL with > 80% PMNs is diagnostic for a chronic periprosthetic joint infection. The gold standard for eradicating a chronic PJI (occurring >4 weeks postoperatively) in North America is a two-stage revision arthroplasty.

Question 58

Following a total hip arthroplasty, the patient complains that the operative leg feels too long. Postoperative radiographs reveal the center of rotation of the femoral head is superior to the tip of the greater trochanter, and the teardrop-to-lesser trochanter distance is increased by 15 mm compared to the contralateral side. Which intraoperative adjustment would have best prevented this?

Explanation

Increasing the neck cut resection level lowers the seating of the femoral stem, effectively decreasing leg length without necessarily compromising femoral offset. While a shorter head would also decrease leg length, it would simultaneously decrease offset and potentially compromise stability.

Question 59

Polyethylene wear in total knee arthroplasty (TKA) often differs from that in total hip arthroplasty. Which of the following best describes the predominant wear mechanism that led to failure in historical flat-on-flat (non-conforming) TKA polyethylene inserts?

Explanation

Delamination and pitting are forms of fatigue wear, which were the predominant failure mechanisms in older, non-conforming flat-on-flat TKA designs. These occurred due to high subsurface cyclic shear stresses, contrasting with the adhesive and abrasive wear typical of THA.

Question 60

In a normal knee, femoral rollback refers to the posterior translation of the femoral contact point on the tibia during deep flexion. In a cruciate-retaining total knee arthroplasty, which of the following is essential to achieve appropriate femoral rollback?

Explanation

In a cruciate-retaining TKA, an intact and appropriately balanced posterior cruciate ligament (PCL) is required to drive posterior femoral rollback during knee flexion. This rollback improves maximal flexion and optimizes the quadriceps lever arm.

Question 61

During a primary total knee arthroplasty, the surgeon evaluates the flexion and extension gaps. The extension gap is symmetric and perfectly balanced, but the flexion gap is excessively tight. Which of the following maneuvers is the most appropriate to address this specific mismatch?

Explanation

A tight flexion gap with a balanced extension gap indicates the anteroposterior dimension of the femur is too large. Downsizing the femoral component (with an anterior referencing system) resects more posterior condylar bone, opening the flexion gap without affecting the extension gap.

Question 62

A 62-year-old man presents with groin pain and swelling 5 years after a primary metal-on-polyethylene total hip arthroplasty. MRI with metal artifact reduction shows a solid periprosthetic pseudotumor. Aspiration yields negative cultures. Which of the following implant factors is most strongly associated with this condition?

Explanation

Trunnionosis (mechanically assisted crevice corrosion) occurs at the modular head-neck junction. It is strongly associated with large-diameter cobalt-chrome heads and high-offset stems, which increase the torsional forces and fretting at the trunnion.

Question 63

Which of the following modifications in the manufacturing of ultra-high molecular weight polyethylene (UHMWPE) has been most effective in significantly reducing the incidence of periprosthetic osteolysis in total hip arthroplasty?

Explanation

Highly cross-linked polyethylene, treated with electron beam or gamma radiation and subsequently thermally treated (melted or annealed) to extinguish free radicals, has dramatically reduced volumetric wear rates and subsequent macrophage-mediated osteolysis.

Question 64

During a primary total knee arthroplasty for severe varus osteoarthritis, the surgeon inadvertently transects the superficial medial collateral ligament (MCL) at its mid-substance. Which of the following is the most appropriate intraoperative management?

Explanation

Intraoperative midsubstance transection of the MCL creates profound coronal plane instability. The standard of care is primary repair of the ligament combined with a constrained condylar knee (CCK) implant to protect the repair and provide immediate stability.

Question 65

A 58-year-old woman with a documented history of severe, blistering skin reactions to cheap jewelry is scheduled for a total knee arthroplasty. What is the most common metal sensitizer in orthopedic implants, and what is the most appropriate alternative implant choice for her?

Explanation

Nickel is the most common metal sensitizer implicated in hypersensitivity reactions. For patients with documented severe metal allergies, using a hypoallergenic implant such as oxidized zirconium (Oxinium) or an all-titanium component is recommended.

Question 66

A 75-year-old woman with a history of a long-segment lumbar spinal fusion (L2 to the sacrum) is undergoing a primary total hip arthroplasty. How does her spinal fusion alter her spinopelvic kinematics when moving from a standing to a seated position, and how should cup positioning be adjusted?

Explanation

In patients with spinopelvic stiffness (e.g., lumbar fusion), the pelvis fails to posteriorly tilt when moving from standing to sitting. This lack of functional acetabular anteversion during sitting increases the risk of anterior impingement and posterior dislocation, necessitating greater cup anteversion.

Question 67

In a revision total hip arthroplasty, the preoperative radiograph demonstrates severe acetabular bone loss with upward migration of the hip center by 3.5 cm, teardrop osteolysis, and destruction of the Kohler line. According to the Paprosky classification, this bone loss pattern is best described as:

Explanation

Paprosky Type IIIB defects are characterized by severe structural bone loss with greater than 3 cm of superior migration of the hip center and disruption of the Kohler line (medial migration). This implies an unsupportive superior dome and medial wall, often requiring a custom triflange or cup-cage construct.

Question 68

During a total knee arthroplasty, the surgeon uses trial components to assess ligamentous balancing. The extension gap is found to be symmetric and well-balanced, but the flexion gap is excessively tight both medially and laterally. Which of the following is the most appropriate surgical step to achieve a balanced knee?

Explanation

Downsizing the femoral component reduces its anteroposterior (AP) dimension. This effectively increases the size of the flexion gap without altering the balanced extension gap.

Question 69

A 68-year-old man presents with insidious onset of pain 3 years after a total hip arthroplasty. Laboratory evaluation shows an ESR of 45 mm/hr and a CRP of 18 mg/L. Joint aspiration yields a white blood cell count of 4,800 cells/uL with 88% neutrophils. Based on current consensus guidelines, what is the most appropriate definitive management?

Explanation

The synovial fluid analysis meets the major criteria for a chronic periprosthetic joint infection (WBC >3000, PMN >80%). Two-stage exchange arthroplasty remains the gold standard for chronic PJI in North America.

Question 70

A 65-year-old man with a history of an L2-S1 spinal fusion is undergoing a primary total hip arthroplasty. Due to his ankylosed lumbar spine, his pelvis fails to retrovert when transitioning from a standing to a seated position. What is the primary instability risk, and how should the acetabular cup positioning be modified intraoperatively?

Explanation

A stiff spine prevents the normal compensatory pelvic retroversion that occurs during sitting, which leads to anterior impingement and subsequent posterior dislocation. To compensate, the acetabular component should be placed with increased anteversion.

Question 71

In the manufacturing process of highly cross-linked polyethylene (HXLPE) for total hip arthroplasty, post-irradiation melting above the melting temperature (135 degrees Celsius) alters the material's properties. Which of the following statements best describes the result of this thermal treatment?

Explanation

Remelting HXLPE above its melting point extinguishes all residual free radicals, preventing future oxidation. However, the process reduces the polymer's crystallinity, which decreases its mechanical yield strength and fatigue resistance.

Question 72

A 68-year-old woman presents with a painful, audible clunking sensation when extending her knee from a flexed position. She underwent a primary posterior-stabilized total knee arthroplasty 14 months ago. What is the most appropriate surgical management for this condition?

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized knees due to a fibrosynovial nodule forming at the superior pole of the patella, which catches in the intercondylar box during extension. Arthroscopic debridement of the nodule is highly effective.

Question 73

During a direct anterior approach for a total hip arthroplasty, the surgeon develops the superficial internervous plane. Which of the following nerves innervates the muscle that forms the medial boundary of this surgical interval?

Explanation

The superficial interval for the direct anterior (Smith-Petersen) approach is between the tensor fasciae latae (laterally) and the sartorius (medially). The sartorius is innervated by the femoral nerve.

Question 74

A 72-year-old woman sustains a periprosthetic femur fracture 8 years after a cemented total hip arthroplasty. Radiographs demonstrate a fracture spiral around the tip of the stem, accompanied by stem subsidence and focal osteolysis in the proximal femur, though distal bone stock is robust. What is the most appropriate treatment?

Explanation

This scenario describes a Vancouver B2 fracture (fracture around the stem, loose component, adequate bone stock). The standard of care is revision arthroplasty using a long stem that bypasses the fracture by at least two cortical diameters, such as a fluted tapered modular stem.

Question 75

During the femoral preparation of a total knee arthroplasty, the surgeon inadvertently places the femoral component in excessive internal rotation. Which of the following intraoperative findings is the direct result of this specific error?

Explanation

Internal rotation of the femoral component lowers the medial posterior condyle and elevates the lateral posterior condyle relative to the tibial cut. This creates a tight medial flexion gap and induces lateral patellar maltracking.

Question 76

Tranexamic acid (TXA) is now routinely administered in total joint arthroplasty to reduce perioperative blood loss. Which of the following best describes its mechanism of action?

Explanation

Tranexamic acid is a synthetic analog of the amino acid lysine. It reversibly and competitively binds to the lysine-binding sites on plasminogen, preventing its conversion to plasmin and thus inhibiting fibrinolysis.

Question 77

A 55-year-old active man who underwent a total hip arthroplasty with a ceramic-on-ceramic bearing 2 years ago presents with a loud, audible squeaking from his hip during ambulation. Radiographic evaluation is most likely to reveal which of the following acetabular component malpositions as the primary contributor?

Explanation

Squeaking in ceramic-on-ceramic hips is highly associated with edge loading and subsequent stripe wear. This complication most frequently occurs when the acetabular cup is positioned with steep inclination or excessive anteversion.

Question 78

A 58-year-old man with isolated medial compartment osteoarthritis is being evaluated for a unicompartmental knee arthroplasty (UKA). Which of the following findings on clinical and radiographic evaluation represents a strict contraindication to a mobile-bearing UKA?

Explanation

An anterior cruciate ligament (ACL) deficiency alters the kinematic rollback of the knee, which dramatically increases the risk of bearing spin-out and premature failure in a mobile-bearing unicompartmental knee arthroplasty.

Question 79

A 64-year-old man presents with a painful groin mass 5 years after receiving a metal-on-polyethylene total hip arthroplasty using a large 36-mm cobalt-chromium femoral head. Joint aspiration reveals thick, sterile fluid with a low WBC count. Serum cobalt levels are significantly higher than chromium levels. What is the most likely diagnosis?

Explanation

Trunnionosis is a form of mechanically assisted crevice corrosion that occurs at the modular head-neck junction, commonly seen with large metal heads. It is characterized by adverse local tissue reactions, sterile effusions, and serum cobalt levels that disproportionately exceed chromium levels.

Question 80

During a total hip arthroplasty, the surgeon meticulously restores the patient's native femoral offset. Which of the following biomechanical advantages is achieved by this specific surgical goal?

Explanation

Restoring or increasing femoral offset increases the moment arm of the abductor muscles. This improves their mechanical advantage, reducing the muscle force required to maintain pelvic stability and consequently lowering the joint reaction force across the hip.

Question 81

A patient reports persistent knee instability and giving way when descending stairs 1 year after a total knee arthroplasty. On examination, the knee is completely stable at 0 degrees and 90 degrees of flexion, but exhibits profound laxity at 45 degrees of flexion. Radiographs demonstrate significant joint line elevation. What is the most likely underlying cause?

Explanation

Mid-flexion instability classically results from joint line elevation. If the distal femur is over-resected, a thicker tibial insert is used to balance extension and 90-degree flexion, but this leaves the collateral ligaments lax in the mid-arc of motion.

Question 82

A 55-year-old active male presents with an audible squeaking sound from his hip 2 years after a ceramic-on-ceramic total hip arthroplasty. Which of the following component positions is most highly associated with this complication?

Explanation

Squeaking in ceramic-on-ceramic total hip arthroplasty is most commonly associated with component malposition, specifically excessive acetabular cup inclination and anteversion. Edge loading due to these malpositions causes microseparation and squeaking.

Question 83

During a total knee arthroplasty, the surgeon evaluates the gaps and notes a symmetric, balanced flexion gap but an extension gap that is tight symmetrically. Which of the following is the most appropriate surgical maneuver to balance the knee?

Explanation

A knee that is tight in extension but balanced in flexion requires increasing the extension gap without affecting the flexion gap. This is achieved by resecting more bone from the distal femur.

Question 84

A 60-year-old female complains of new-onset anterior groin pain 6 months following an uncomplicated primary total hip arthroplasty. Pain is reproducible with active straight leg raise and resisted hip flexion. Radiographs demonstrate an un-cemented acetabular cup with 10 degrees of anteversion and 40 degrees of inclination. What is the most likely cause of her symptoms?

Explanation

Anterior groin pain exacerbated by active hip flexion or straight leg raise following THA is classic for iliopsoas impingement. This is often caused by an anteriorly prominent acetabular component or insufficient cup anteversion.

Question 85

A patient presents with a painful popping sensation in the anterior knee 1 year after a posterior stabilized total knee arthroplasty. The pop occurs consistently as the knee moves from flexion to extension, typically around 30 to 40 degrees of flexion. What is the most appropriate initial surgical management?

Explanation

Patellar clunk syndrome occurs in posterior-stabilized TKAs when a fibrous nodule forms at the superior pole of the patella and catches in the femoral intercondylar notch. Arthroscopic excision of the nodule provides excellent and predictable relief of symptoms.

Question 86

During a direct anterior approach for a total hip arthroplasty, the surgeon utilizes the internervous plane between which of the following muscles?

Explanation

The direct anterior (Smith-Petersen) approach to the hip exploits the internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). This allows access to the joint without detaching muscle insertions.

Question 87

In an effort to optimize hip biomechanics during total hip arthroplasty, a surgeon plans to medialize the center of rotation of the acetabulum. Which of the following best describes the mechanical effect of this maneuver?

Explanation

Medializing the center of rotation of the acetabulum decreases the body weight moment arm. This reduces the amount of abductor force required to maintain a level pelvis, thereby decreasing the overall joint reactive force.

Question 88

A 72-year-old male presents with acute thigh pain and inability to bear weight after a minor fall. Radiographs demonstrate a periprosthetic femur fracture around a cemented total hip arthroplasty stem. The fracture is located at the tip of the stem, the stem is radiographically loose, and there is good proximal femoral bone stock. Which classification and treatment are most appropriate?

Explanation

This is a Vancouver B2 periprosthetic fracture, characterized by a fracture around or just below the stem, a loose prosthesis, and adequate bone stock. The standard of care is revision arthroplasty using a long, uncemented, diaphyseal-engaging stem.

Question 89

During a total knee arthroplasty for a severe fixed valgus deformity, the surgeon proceeds with a lateral soft tissue release. According to the standard inside-out technique, which structure is typically released first after osteophytes are removed?

Explanation

In correcting a fixed valgus deformity during TKA, after removing osteophytes, the iliotibial (IT) band is typically the first structure released. This is followed sequentially by the popliteus, posterolateral capsule, and lateral collateral ligament if necessary.

Question 90

Highly cross-linked polyethylene (HXLPE) is widely used in total hip arthroplasty to reduce wear rates. Which of the following manufacturing steps is primarily responsible for eliminating free radicals to prevent in vivo oxidation?

Explanation

After irradiation generates cross-linking in polyethylene, residual free radicals are left behind that can cause oxidation and degradation. Remelting or annealing is performed to extinguish these free radicals and stabilize the material.

Question 91

A surgeon performs a lateral retinacular release during a total knee arthroplasty to improve patellar tracking. Which vessel is at greatest risk of injury during this procedure, potentially leading to patellar avascular necrosis?

Explanation

The superior lateral genicular artery is the primary blood supply to the patella and is at significant risk during a lateral retinacular release. Injury to this vessel can lead to patellar avascular necrosis, especially if the medial supply is compromised.

Question 92

A patient develops a foot drop and decreased sensation over the dorsum of the foot immediately following a primary total hip arthroplasty via a posterior approach. Which specific nerve division is most commonly injured in this scenario?

Explanation

Sciatic nerve injury during a posterior THA most frequently involves the peroneal (fibular) division because its fibers are more lateral and tightly tethered. This results in weakness of ankle dorsiflexion and altered dorsal foot sensation.

Question 93

A patient presents with a painful total knee arthroplasty 3 years postoperatively. Synovial fluid analysis reveals an elevated alpha-defensin level. What is the primary source of alpha-defensin in the setting of a periprosthetic joint infection?

Explanation

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

Question 94

A 65-year-old female with a documented severe type IV hypersensitivity reaction to nickel requires a primary total knee arthroplasty. Which of the following femoral component materials is most appropriate to use in this patient?

Explanation

For patients with significant metal allergies, an oxidized zirconium or entirely titanium implant is preferred. Oxidized zirconium femoral components provide a durable articular surface with minimal release of allergenic metal ions.

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

AAOS & ABOS Hip & Knee Reconstruction MCQs (Set 1) | Arthroplasty Board Review

Key Takeaway

AAOS & ABOS Hip & Knee Reconstruction MCQs (Set 1) | Arthroplasty Board Review

Chapter Index