Orthopedic Hip MCQs 2026 | Board Review & Answers

Question 1

A 67-year-old man is requesting revision surgery because of continued pain in the knee after undergoing a total knee replacement 2 years ago. Examination reveals that the knee is not warm, the incision is well-healed, and the skin has normal coloration and hair formation. No varus or valgus instability is noted, and knee range of motion is 5 degrees to 100 degrees. Laboratory studies show an erythrocyte sedimentation rate of 15 mm/h and a WBC of 5,000/mm3. Aspiration of the knee reveals clear fluid that shows no growth on culture. Radiographs reveal an appropriately positioned cruciate-retaining cemented total knee arthroplasty that is well-fixed. What is the probability that the patient's pain will be improved with revision surgery?

Explanation

The patient has a well-fixed and aligned painful total knee replacement. The success rate of revision knee replacement for pain when no mechanical problem can be identified is approximately 40%. The critical step is to rule out the presence of infection with appropriate laboratory studies and aspiration. If no infection is detected, revision should be avoided. Rand JA: Planning for revision total knee arthroplasty, in Zuckerman JD (ed): Instructional Course Lectures 48. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 161-166.

Question 2

For patients undergoing a surgical procedure where the risk of requiring a transfusion is less than 10%, the International Committee of Effective Blood Usage suggests

Explanation

Recent studies have shown a high rate of waste of autologous blood. Therefore, the Committee does not recommend autologous blood donation for procedures that carry a transfusion risk of 10% or less. Toy P, Beattie C, Gould S, et al: Transfusion alert: Use of autologous blood. National Heart, Lung, and Blood Institute Expert Panel on the use of autologous blood. Transfusion 1992;35:703-711.

Question 3

Figure 12 shows the radiograph of a 55-year-old man who has severe, painful osteoarthritis of the left hip and is scheduled to undergo a left total hip arthroplasty. History reveals that he underwent a right total hip arthroplasty 5 years ago that remains pain-free. Based on the preoperative radiograph, the patient is at greatest risk for what complication?

Explanation

The patient is at increased risk for limb-length discrepancy because the radiograph shows that the left leg is already longer than the right leg. To restore the proper biomechanics of the left hip, the left leg may have to be lengthened, further increasing the limb-length discrepancy. Intraoperative fracture, deep vein thrombosis, sciatic nerve palsy, and thigh pain are commonly associated with total hip arthroplasty, but the patient is not at increased risk for these complications.

Question 4

Figures 13a and 13b show the preoperative radiographs of a 60-year-old woman who is scheduled to undergo total knee arthroplasty under epidural anesthesia. Postoperatively she reports a burning sensation on the dorsum of her foot despite the administration of IV analgesics through a patient-controlled analgesia (PCA) pump. Management should now include

Explanation

13b The patient has a significant flexion contracture and valgus deformity; therefore, the risk of peroneal nerve injury is increased. Idusuyi and Morrey noted that epidural anesthesia also increases the risk of peroneal nerve injury. The initial symptom can be a burning sensation on the foot, followed by pain and then motor weakness. Initial management should consist of release of the dressings and knee flexion. Idusuyi OB, Morrey BF: Peroneal nerve palsy after total knee arthroplasty: Assessment of predisposing and prognostic factors. J Bone Joint Surg Am 1996;78:177-184.

Question 5

Figures 14a and 14b show the plain radiographs of an 85-year-old woman who has had severe pain in the right knee for the past 4 months. Management should consist of

Explanation

14b The patient has osteonecrosis of the lateral femoral condyle with collapse of the articular surface. Because there is already collapse of the articular surface, a total knee arthroplasty is the treatment of choice. The results of total knee arthroplasty in these patients are usually excellent. However, knee replacement is only a resurfacing procedure, and some patients with global osteonecrosis of the distal femur may have residual pain after knee replacement. High tibial osteotomy may be indicated in younger patients who have a varus deformity and localized osteonecrosis. Arthroscopic surgery would provide minimal relief for this patient because there is already collapse of the articular surface. A hinged knee brace will not adequately unload the joint. An osteochondral allograft should be considered only for younger patients with localized osteonecrosis. Bergman NR, Rand JA: Total knee arthroplasty in osteonecrosis. Clin Orthop 1991;273:77-82.

Question 6

The failure of the acetabular component shown in Figure 15 is most likely the result of the use of a 32-mm head and

Explanation

Astion and associates analyzed 23 acetabular components, out of a total of 173 implanted, that had failed because of either migration or severe osteolysis. The radiographic appearance of osteolysis was positively associated with the duration that the implant had been in situ. The prevalence of osteolysis was also significantly greater in acetabular components with an outer diameter of 55 mm or less (a polyethylene thickness of 8.5 mm or less). Thirteen of the 23 components were revised at a mean of 70 months after the index operation. Examination of the retrieved acetabular components revealed extensive polyethylene damage on the articular and back surfaces of the liners. Cracks in the polyethylene rim of the liner and deformation of the antirotation notch in the polyethylene rim were common findings. The density of the polyethylene was greater than expected, and more particles than anticipated had not fused with the surrounding polyethylene. Factors related to both the design and the material contributed to the failure of these porous-coated anatomic acetabular components.

Question 7

The use of elevated rim acetabular liners and long femoral necks may result in

Explanation

Elevated rim acetabular liners may improve the anteversion of the acetabular component that, in turn, might improve the stability of the hip replacement through a range of motion. Long femoral necks with skirts will increase the abductor tension and may be necessary to equalize limb lengths. However, either of these measures may increase the likelihood of impingement of the femoral component on the acetabular rim and may lead to dislocation. The restricted range of motion secondary to impingement has been shown to lead to further polyethylene wear that may result in osteolysis. Cobb TK, Morrey BF, Ilstrup DM: The elevated rim acetabular liner in total hip arthroplasty: Relationship to postoperative dislocation. J Bone Joint Surg Am 1996;78:80-86.

Question 8

Cementation technique has a definite influence on the long-term survival of cemented femoral components. Both clinical and autopsy studies support the use of a cement mantle with a thickness of how many millimeters?

Explanation

Long-term radiographic analysis of cemented total hips supports the creation of a 2- to 5-mm cement mantle in the proximal medial region. Autopsy studies have shown that the incidence of crack formation was greatest when the cement mantle was less than 2 mm. Ebramzadeh E, Sarmiento A, McKellop HA, Llinas A, Gogan W: The cement mantle in total hip arthroplasty: Analysis of long-term radiographic results. J Bone Joint Surg Am 1994;76:77-87. Jasty M, Maloney WJ, Bragdon CR, O'Connor DO, Haire T, Harris WH: The initiation of failure in cemented femoral components of hip arthroplasty. J Bone Joint Surg Br 1991;73:551-558.

Question 9

A 73-year-old man is scheduled to have mature heterotopic bone resected from around his left total hip arthroplasty. The optimal management for prophylaxis against the return of heterotopic bone postoperatively is radiation therapy that consists of

Explanation

Patients require prophylaxis for heterotopic bone after resection to prevent recurrence. The optimal management has been found to be a dose of 700 cGy in one dose delivered either pre- or postoperatively. A dose of 2,000 to 3,000 cGy is considered excessive. Radiation therapy consisting of 1,000 cGy in five doses is an acceptable prophylaxis; however, it will require an extended hospital stay of 3 to 4 days and is more problematic for the patient who must be transported for radiation therapy for 5 days. A dose of 400 cGy is not as effective in prophylaxis for heterotopic bone formation. Healy WL, Lo TC, DeSimone AA, Rask B, Pfeifer BA: Single-dose irradiation for the prevention of heterotopic ossification after total hip arthroplasty: A comparison of doses of five hundred and fifty and seven hundred centigray. J Bone Joint Surg Am 1995;77:590-595. Pelligrini VD Jr, Gregoritch SJ: Preoperative irradiation for the prevention of heterotopic ossification following total hip arthroplasty. J Bone Joint Surg Am 1996;78:870-881.

Question 10

Which of the following is considered a potential advantage in prophylaxis for the prevention of deep venous thrombosis associated with the use of low-molecular weight heparin (LMWH) as compared with fixed-dose unfractionated heparin?

Explanation

One possible reason for improved efficacy of LMWHs is the relative improved bioavailability compared with that of unfractionated heparin. This is, in part, the result of a more predictable dose response and a longer half-life. There is no alteration of venous flow, and the rate of bleeding complications is the same or slightly higher than that of other prophylactic agents. Colwell CW Jr, Spiro TE, Trowbridge AA: Use of enoxaparin, a low-molecular weight heparin, and unfractionated heparin for the prevention of deep venous thrombosis after elective hip replacement: A clinical trial comparing efficacy and safety. J Bone Joint Surg Am 1994;76:3-14. Bara L, Billaud E, Kher A, Samama M: Increased anti-Xa bioavailability for a low-molecular weight heparin (PK 10169) compared with unfractionated heparin. Semin Thromb and Hemost 1985;11:316-317.

Question 11

Figure 16 shows the radiograph of a 75-year-old man who has progressive groin pain and a limp following total hip replacement. At revision surgery, the anterior and posterior columns of the acetabulum are noted to be intact. The optimal surgical technique for acetabular component reconstruction is a

Explanation

Large cementless acetabular components have been shown to perform well in revision acetabular reconstruction. The use of such components is predicated on the presence of adequate anterior and posterior column bone. If a good press-fit can be achieved between the anterior and posterior columns, typically, the remaining defects can be filled with morcellized bone graft. Protrusio cages are typically used in situations where it is not possible to obtain adequate fixation with a large acetabular component. The use of a high hip center with small sockets is more typical of primary arthroplasty in patients with developmental dysplasia of the hip. Bulk acetabular allografts for large segmental defects might be necessary in certain situations, although the use of bulk allografts has resulted in a high failure rate after 5 years. Early results of the use of protrusio cages and bone grafting for large segmental defects have been favorable. Petrera P, Rubash HE: Revision total hip arthroplasty: The acetabular component. J Am Acad Orthop Surg 1995;3:15-21.

Question 12

Which of the following is a recognized consequence of hip fusion?

Explanation

Low back pain is an expected long-term complication of fusion; ipsilateral knee laxity is frequently encountered, as is degeneration of the contralateral hip. Hip fusion is equally valuable for both men and women, with both genders reporting satisfactory sexual function. Female patients often deliver by elective Cesarean section, although vaginal deliveries are reported. Liechti R (ed): Hip Arthrodesis and Associated Problems. Berlin, Germany, Springer-Verlag, 1978, pp 109-117.

Question 13

Treatment of a cruciate-retaining total knee that is unstable in flexion is best accomplished by

Explanation

Pagnano and associates revised 25 painful primary posterior cruciate-retaining total knee arthroplasties for flexion instability. The patients shared typical clinical presentations that included a sense of instability without frank giving way, recurrent knee joint effusion, soft-tissue tenderness involving the pes anserine tendons and the retinacular tissue, posterior instability of 2+ or 3+ with a posterior drawer or a posterior sag sign at 90 degrees of flexion, and above-average motion of the total knee arthroplasty. Twenty-two of the knee replacements were revised to posterior stabilized implants, and three underwent tibial polyethylene liner exchange only. Nineteen of the 22 knee replacements revised to a posterior stabilized implant showed marked improvement after the revision surgery. Only one of the three knee replacements that underwent tibial polyethylene exchange was improved. Flexion instability can be a cause of persistent pain and functional impairment after posterior cruciate-retaining total knee arthroplasty. Revision surgery that focuses on balancing the flexion and extension spaces, in conjunction with a posterior stabilized knee implant, seems to be a reliable treatment for symptomatic flexion instability after posterior cruciate-retaining total knee arthroplasty.

Question 14

The stiffness of a 16-mm femoral stem is mostly influenced by the

Explanation

The stiffness is most influenced by the geometry, in particular the diameter of the stem. The bending rigidity increases to the fourth power of the radius. The elastic modulus of the material increases as a direct linear relationship. The surface coating does not affect the bending rigidity greatly unless it increases the diameter significantly.

Question 15

Figures 17a and 17b show the AP and lateral radiographs of a 75-year-old woman who reports giving way and shifting of the knee, particularly when she is descending stairs or ambulating on level surfaces. History reveals a total knee replacement 5 years ago. Treatment should consist of

Explanation

17b The radiographs show well-fixed components of a posterior cruciate-retaining total knee replacement. The relative position of the femoral component is anteriorly subluxated relative to the tibial component. The AP radiograph shows that the articular space is markedly asymmetric, indicating either failure or fracture of the polyethylene or subluxation of the femur relative to the tibia. The patient's symptoms suggest a failure of the posterior cruciate ligament that is consistent with the radiographic findings; therefore, the treatment of choice is revision to a posterior cruciate-substituting implant.

Question 16

Factors contributing to an increased risk of hip fracture include reduced bone mineral density of the femoral neck, cognitive status of the individual, and

Explanation

The etiology of hip fractures in the elderly is multifactorial, and intervention and prevention can occur at multiple points. Events leading to hip fracture from a fall include fall initiation (during which the individual's neuromuscular status, cognitive status, and vision come into play along with environmental hazards); fall descent (fall direction toward the side being the most influential, energy content of the fall, and fall height, along with muscle activity of the muscles of the thigh); impact (impact location, soft-tissue attenuation such as from trochanteric padding or from overlying fat, impact surface, and muscle activity); and the structural capacity of the femur (bone mineral density, bone geometry, and bone architecture). Hayes and Myers noted that striking the ground in a stiff state with the trunk muscles contracted actually increased the peak impact force, whereas falling in a relaxed state actually reduced peak impact force. Flexion of the trunk at impact had no bearing on the impact force. Direction of the fall was important; falls to the side, not forward, were associated with an increased risk of hip fracture. Increased muscle activity about the hip is thought to be associated with spontaneous fractures of the hip and may actually account for up to 25% of hip fractures; however, it is not related to fractures resulting from a fall.

Question 17

A healthy 70-year-old man has a swollen knee after undergoing a knee replacement 10 years ago. Aspiration of the knee reveals cloudy, viscous synovial fluid. Laboratory studies show an erythrocyte sedimentation rate of 10 mm/h and a C-reactive protein level of less than 0.5. What is the most likely diagnosis?

Explanation

Polyethylene wear debris can result in significant synovitis and subsequent cloudy appearing synovial fluid. Typically, laboratory studies show a WBC of less than 30,000/mm3 no left shift. Cytologic examination can reveal intra-articular polyethylene particles. Infected total knee arthroplasty is extremely uncommon in a healthy, immune-competent patient who has a normal preoperative erythrocyte sedimentation rate and C-reactive protein level.

Question 18

The insurance carrier of a patient who underwent total knee arthroplasty 4 days ago is now demanding that the patient be discharged from the hospital. However, examination reveals that the patient has a range of motion of only 10 degrees to 55 degrees, and the patient is concerned whether she will ever move her knee normally. The insurance company representative should be advised that

Explanation

Examination findings that show flexion of only 55 degrees at discharge should alert the surgeon that the patient will require close scrutiny and follow-up. Mauerhan and associates examined the records of 745 patients who had a primary total knee arthroplasty from 1993 to 1996. At their institution, development and implementation of clinical pathways resulted in a significant decrease in the average length of stay, beginning in 1993 with 6.4 days +/- 1.8 days and progressively decreasing to 4.4 days +/- 1.0 days in 1996. The rate of manipulation (patients manipulated at 6 weeks/total number of patients receiving total knee arthroplasty) was 6.0% in 1993, 11.3% in 1994, 13.5% in 1995, and 12.0% in 1996. In the period of 1993 to 1996, patients requiring manipulation consistently had a lower range of motion of 69.0 degrees +/- 10 degrees at the time of discharge compared with patients not requiring manipulation who had a range of motion of 80.7 degrees +/- 10.6 degrees. In this era of outpatient services, however, another solution would be to arrange for outpatient physical therapy on a more frequent basis and to see the patient more frequently in the office until an acceptable range of motion is established.

Question 19

Figure 18 shows the radiograph of a patient with a total hip arthroplasty dislocation. During revision, increasing the diameter of the femoral head while maintaining the ratio of head-to-neck diameter constant has the effect of

Explanation

Although there is strong clinical and laboratory evidence that suggests smaller head size is linked with lower rates of polyethylene wear, moving to the use of 22-mm heads from larger sizes would tend to increase the dislocation rate. The key premise to this argument is that the absolute size of the femoral neck remains unchanged. While neck diameters were appropriate for the early monoblock femoral components, the use of modular femoral stems allows the surgeon to place 22-mm heads onto the same neck and trunion as used by larger heads. This has the effect of lessening the head-to-neck diameter ratio, which then accentuates the rate of impingement and dislocation. Reducing the neck diameter in proportion to the head diameter would eliminate the range-of-motion penalty accompanying head size reduction. Scifert and associates used a three-dimensional finite element model to study various combinations of femoral head size and neck ratios. They found that increasing the diameter of the femoral head while maintaining a constant head-to-neck diameter had the effect of significantly increasing the resisting moment necessary to induce a dislocation. The higher the head-to-neck ratio, the greater the range of motion until impingement and the greater the range of motion to dislocation.

Question 20

During primary total knee arthroplasty with trial implants in place, the surgeon notes technically satisfactory patellar resurfacing and restoration of a physiologic mechanical axis but excessively lateral patellar tracking. Treatment should now include

Explanation

The most common causes of patellar instability after total knee arthroplasty are valgus malalignment, internal rotation of the femoral or tibial component, medialization of the femoral component, errors in patellar preparation and resurfacing, and failure to perform a lateral release. These factors should be addressed before considering capsular closure. Distal extensor mechanism realignment should be avoided because of the complication rate. The proximal extensor mechanism would not adequately compensate for implant malrotation. Barnes CL, Scott RD: Patellofemoral complications of total knee replacement, in Heckman JD (ed): Instructional Course Lectures 42. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1993, pp 309-314.

Question 21

Figure 19 shows the current radiograph of a 48-year-old man who reports hip pain and marked difficulty walking after undergoing revision of a failed total hip replacement 2 years ago. What is the mechanism of failure?

Explanation

Fatigue from repetitive loading of the stem with the distal aspect well-fixed resulted in stem failure. If the stem had loosened, it would not have broken. Crevice corrosion occurs at a taper interface; galvanic corrosion occurs at the junction of two metals of differing electrochemical potentials, not along a uniform portion of the implant. Simon SR (ed): Orthopaedic Basic Science. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 449-486.

Question 22

Torsional moments about the longitudinal axis of a total hip arthroplasty show what change during stair climbing compared with walking?

Explanation

The magnitudes of out-of-plane loads on a total hip replacement during activities of daily living can be substantial. Bergmann and associates studied these forces about two instrumented hip prostheses. They noted that the torsional moment about the hip during stair climbing is twice as high as during slow walking and that similar moments are generated during slow jogging. Higher loads were noted when the patients stumbled without falling. They also noted that the torsional moments observed in vivo were close to or even exceeded the experimentally determined limits of the torsional strength of implant fixations. Hurwitz DE, Andriacchi TP: Biomechanics of the hip, in Callaghan JJ, Rosenberg AG, Rubash HE (eds): The Adult Hip. Philadelphia, PA, Lippincott Raven, 1998, pp 75-85.

Question 23

When converting the knee shown in Figure 20 to a total knee arthroplasty, satisfactory outcome can be expected in what percent of patients?

Explanation

Naranja and associates reviewed 37 knees (35 patients, with 28 women and 7 men) without any motion that were converted to total knee arthroplasties. After an average follow-up of 90 months, the patients lacked an average of 7 degrees of extension and had 62 degrees of flexion. Results showed a short-term complication rate of 24% (stiffness requiring manipulation, delayed wound healing, and recurrent hemarthrosis), a major complication rate of 35% (patellar tendon or tibial tubercle avulsion, persistent pain requiring arthrodesis, loosening, and joint stiffness requiring arthrotomy for excision of scar tissue), and an infection rate of 14%. The total complication rate was 57%. A satisfactory outcome (no pain and an unlimited ambulation distance) was obtained in only 10 patients (29%). There was no relationship between results and the angle at which the knee was ankylosed preoperatively. This study revealed that although success in reconstructing a previously ankylosed or arthrodesed knee is possible, the lack of consistent adequate motion and the complication rate may suggest that the surgeon reconsider the risks and benefits of this difficult procedure.

Question 24

The specificity of intraoperative frozen sections obtained for the evaluation of infected total hip arthroplasty may be improved by

Explanation

Lonner and associates conducted a prospective study to determine the reliability of analysis of intraoperative frozen sections for the identification of infection during 175 consecutive revision total joint arthroplasties (142 hips and 33 knees). The mean interval between the primary arthroplasty and the revision arthroplasty was 7.3 years (range, 3 months to 23 years). Of the 175 patients, 23 had at least 5 polymorphonuclear leukocytes per high-powered field on analysis of the frozen sections and were considered to have an infection. Of these 23 patients, five had 5 to 9 polymorphonuclear leukocytes per high-powered field and 18 had at least 10 polymorphonuclear leukocytes per high-powered field. The frozen sections for the remaining 152 patients were considered negative. On the basis of cultures of specimens obtained at the time of the revision surgery, 19 of the 175 patients were considered to have an infection. Of the 152 patients who had negative frozen sections, three were considered to have an infection on the basis of the results of the final cultures. Of the 23 patients who had positive frozen sections, 16 were considered to have an infection on the basis of the results of the final cultures; all 16 had frozen sections that showed at least 10 polymorphonuclear leukocytes per high-powered field. The sensitivity and specificity of the frozen sections were similar regardless of whether an index of 5 or 10 polymorphonuclear leukocytes per high-powered field was used. Analysis of the frozen sections had a sensitivity of 84% for both indices, whereas the specificity was 96% when the index was 5 polymorphonuclear leukocytes and 99% when it was 10 polymorphonuclear leukocytes. However, the positive predictive value of the frozen sections increased significantly (P < 0.05), from 70% to 89%, when the index increased from 5 to 10 polymorphonuclear leukocytes per high-powered field. The negative predictive value of the frozen sections was 98% for both indices. At least 10 polymorphonuclear leukocytes per high-powered field was predictive of infection, while 5 to 9 polymorphonuclear leukocytes per high-powered field was not necessarily consistent with infection. Less than 5 polymorphonuclear leukocytes per high-powered field reliably indicated the absence of infection. Feldman DS, Lonner JH, Desai P, Zuckerman JD: The role of intraoperative frozen sections in revision total joint arthroplasty. J Bone Joint Surg Am 1995;77:1807-1813. Lonner JH, Desai P, Dicesare PE, Steiner G, Zuckerman JD: The reliability of analysis of intraoperative frozen sections for identifying active infection during revision hip or knee arthroplasty. J Bone Joint Surg Am 1996;78:1553-1558. Spangehl MJ, Younger AS, Masri BA, Duncan CP: Diagnosis of infection following total hip arthroplasty, in Cannon WD Jr (ed): Instructional Course Lectures 47. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 285-295.

Question 25

Figures 21a through 21c show the radiographs of a 70-year-old woman who has persistent pain with activity after undergoing hip revision 6 months ago. Treatment should now consist of

Explanation

21b 21c The radiographs show disruption of the posterior column of the acetabulum with radiolucencies about the component. Because the patient requires a stable construct to allow the bone to heal, the treatment of choice is an antiprotrusio cage and a graft. Gill TJ, Sledge JB, Muller ME: The Burch-Schneider anti-protrusio cage in revision total hip arthroplasty: Indications, principles, and long-term results. J Bone Joint Surg Br 1998;80:946-953.

Question 26

A 60-year-old woman presents with persistent groin pain two years after undergoing an uncomplicated cementless total hip arthroplasty. Radiographs show a well-fixed acetabular component with an overhanging anterior edge. An injection of local anesthetic into the hip joint does not relieve her pain, but an injection into the psoas sheath provides complete relief. What is the most appropriate next step in management?

Explanation

Anterior overhang of the acetabular component can cause iliopsoas impingement. If conservative measures fail and a diagnostic injection confirms the source, iliopsoas release is the treatment of choice before considering cup revision.

Question 27

Which of the following bearing surface combinations in total hip arthroplasty is most closely associated with the phenomenon of "stripe wear"?

Explanation

Stripe wear is a characteristic finding in ceramic-on-ceramic bearings. It occurs when the ceramic head contacts the edge of the ceramic liner, often due to microseparation during the swing phase of gait.

Question 28

A 72-year-old man sustains a periprosthetic femur fracture around a cemented femoral stem. Radiographs demonstrate a fracture around the tip of the stem, with the stem remaining well-fixed and no cement mantle fracture. According to the Vancouver classification, what is the most appropriate surgical management?

Explanation

This is a Vancouver Type B1 fracture (fracture around the stem, well-fixed prosthesis). The standard of care is open reduction and internal fixation using a lateral locked plate and cables/screws.

Question 29

A 45-year-old man with a metal-on-metal total hip arthroplasty presents with progressive groin pain and swelling. Blood metal ion testing shows elevated cobalt and chromium levels. MARS MRI demonstrates a large cystic mass communicating with the joint. What histologic finding is most characteristic of this condition?

Explanation

Adverse local tissue reactions (ALTR) or pseudotumors in metal-on-metal hips are characterized histologically by aseptic lymphocytic vasculitis-associated lesions (ALVAL). This represents a delayed-type hypersensitivity reaction to metal wear debris.

Question 30

A 25-year-old professional hockey player presents with gradual onset of anterior hip pain exacerbated by hip flexion and internal rotation. Radiographs reveal an alpha angle of 68 degrees and a prominent bump at the anterolateral femoral head-neck junction. What is the most likely diagnosis?

Explanation

An elevated alpha angle (>50-55 degrees) and a bump at the head-neck junction (pistol grip deformity) are diagnostic of Cam-type FAI. This is commonly seen in young, active males.

Question 31

A 68-year-old woman is scheduled for a total hip arthroplasty via a direct anterior approach. Which of the following neurologic structures is at greatest risk of injury during the superficial surgical dissection?

Explanation

The direct anterior approach to the hip uses the internervous plane between the tensor fasciae latae (superior gluteal nerve) and the sartorius (femoral nerve). The lateral femoral cutaneous nerve is at highest risk during the superficial dissection.

Question 32

In the context of total hip arthroplasty, the use of highly cross-linked polyethylene (HXLPE) compared to conventional ultra-high-molecular-weight polyethylene (UHMWPE) has been shown to significantly reduce:

Explanation

Highly cross-linked polyethylene (HXLPE) is manufactured using irradiation to create cross-links, which significantly decreases volumetric wear rates and subsequent osteolysis compared to conventional polyethylene.

Question 33

A 30-year-old woman is diagnosed with Ficat stage II avascular necrosis (AVN) of the right femoral head. Radiographs show mixed sclerosis and cysts without subchondral collapse (crescent sign). What is the most appropriate initial surgical intervention if conservative management fails?

Explanation

Ficat stage II AVN involves bone remodeling (sclerosis/cysts) but no subchondral collapse or joint space narrowing. Core decompression is indicated to relieve intraosseous pressure and promote revascularization in pre-collapse stages.

Question 34

During templating for a total hip arthroplasty, increasing the femoral head neck length (e.g., using a +4 mm head instead of a +0 mm head) without changing the stem size or position will have what effect on hip biomechanics?

Explanation

Increasing the head neck length increases both the vertical height (leg length) and the horizontal distance (femoral offset). The exact proportion depends on the neck-shaft angle of the selected femoral stem.

Question 35

A 55-year-old man presents with an acute periprosthetic joint infection 2 weeks after a total hip arthroplasty. He is systemically well, and the implant is well-fixed. According to current guidelines, what is the most appropriate surgical treatment?

Explanation

DAIR is indicated for acute postoperative periprosthetic joint infections (typically within 3-4 weeks of index surgery) when implants are well-fixed and there is no sinus tract. Modular components (e.g., femoral head and polyethylene liner) should be exchanged.

Question 36

A 75-year-old woman with osteoporosis undergoes an uncomplicated cementless total hip arthroplasty. Six weeks postoperatively, she presents with severe thigh pain and inability to bear weight. Radiographs show a displaced, spiral fracture of the proximal femur originating at the distal tip of the stem. The stem has subsided by 2 cm. What is the appropriate Vancouver classification and treatment?

Explanation

A fracture around the stem with a loose prosthesis is a Vancouver B2 fracture. The treatment of choice is revision arthroplasty using a long, diaphyseal-engaging cementless stem to bypass the fracture, along with fracture fixation.

Question 37

What is the primary advantage of utilizing a dual mobility articulation in total hip arthroplasty?

Explanation

Dual mobility constructs feature a large polyethylene head that articulates within a metal shell, while a smaller standard head articulates within the polyethylene. This increases the effective jump distance and safe range of motion, reducing dislocation risk.

Question 38

A 60-year-old male with a history of bilateral total hip arthroplasties presents with new-onset squeaking from his left hip during ambulation. He has a ceramic-on-ceramic bearing on the left. Radiographs reveal a well-fixed cup with an abduction angle of 65 degrees. What is the most likely cause of the squeaking?

Explanation

Squeaking in ceramic-on-ceramic THA is highly correlated with edge loading, which typically occurs due to acetabular cup malposition (e.g., steep inclination angle >50 degrees or excessive anteversion), leading to microseparation and stripe wear.

Question 39

In evaluating a painful total hip arthroplasty, an elevated synovial fluid alpha-defensin test is highly specific for:

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. It is a highly sensitive and specific synovial fluid biomarker for diagnosing periprosthetic joint infection (PJI).

Question 40

A 40-year-old woman undergoes a periacetabular osteotomy (PAO) for symptomatic developmental dysplasia of the hip. During the procedure, the ilioischial osteotomy is performed. Which of the following nerves is at greatest risk of injury during this specific osteotomy cut?

Explanation

The sciatic nerve lies in close proximity to the posterior column of the acetabulum. It is at highest risk of injury during the ilioischial (posterior) osteotomy phase of a Bernese periacetabular osteotomy if the osteotome penetrates too deeply.

Question 41

A 58-year-old man presents with persistent lateral hip pain and a positive Trendelenburg sign one year after a total hip arthroplasty via a direct lateral (Hardinge) approach. MRI demonstrates a complete avulsion of the anterior third of the gluteus medius and minimus tendons without significant fatty infiltration. Management should consist of:

Explanation

Postoperative abductor tears can occur after a direct lateral approach. Given the complete avulsion, functional deficit (Trendelenburg sign), and lack of fatty degeneration, surgical repair is indicated for restoring hip mechanics.

Question 42

Which of the following radiographic findings is most characteristic of Pincer-type femoroacetabular impingement?

Explanation

Pincer impingement is caused by focal or global acetabular overcoverage. The "crossover sign" on an AP pelvis radiograph indicates cranial retroversion of the acetabulum, a common cause of Pincer-type FAI.

Question 43

A 62-year-old man who underwent a metal-on-polyethylene total hip arthroplasty 5 years ago presents with spontaneous groin pain. Radiographs are unremarkable. Metal artifact reduction sequence (MARS) MRI shows a solid/cystic mass in the iliopsoas bursa. Serum cobalt levels are 8.5 ppb and chromium levels are 1.2 ppb. What is the most likely etiology?

Explanation

In a metal-on-polyethylene THA, significantly elevated cobalt levels disproportionate to chromium levels, along with a pseudotumor, strongly suggest trunnionosis (corrosion at the modular head-neck junction) rather than bearing wear.

Question 44

The "safe zone" for acetabular cup placement in total hip arthroplasty, originally described by Lewinnek, suggests which of the following target angles to minimize dislocation risk?

Explanation

Lewinnek's safe zone for acetabular component positioning is defined as an inclination (abduction) angle of 40° ± 10° and an anteversion angle of 15° ± 10°. Placements outside this zone traditionally correlate with a higher risk of dislocation.

Question 45

A 65-year-old man presents with equivocal signs of periprosthetic joint infection 3 years after THA. Synovial fluid aspiration yields a WBC count of 2,500/uL with 75% PMNs. Which of the following synovial fluid biomarkers provides the highest specificity for diagnosing a periprosthetic joint infection in this scenario?

Explanation

Synovial fluid alpha-defensin is a highly specific and sensitive biomarker for PJI. It is particularly useful in scenarios where traditional aspiration cell counts are equivocal.

Question 46

A 55-year-old man with a metal-on-polyethylene total hip arthroplasty presents with new-onset groin pain 6 years postoperatively. Radiographs show a well-fixed stem and cup. Serum cobalt is 12 ppb and chromium is 1.5 ppb. What is the most likely etiology of his pain?

Explanation

Mechanically assisted crevice corrosion (trunnionosis) in metal-on-polyethylene THA is characterized by elevated serum cobalt levels out of proportion to chromium. This is distinct from metal-on-metal bearing wear, which typically elevates both ions equally.

Question 47

A 70-year-old man with ankylosing spondylitis and a fused lumbar spine is scheduled for a primary THA. His pelvis remains in a neutrally tilted position and fails to retrovert when he transitions from standing to sitting. To prevent posterior instability, how should the acetabular component positioning be adjusted?

Explanation

Normally, the pelvis retroverts during sitting to accommodate hip flexion by functionally increasing acetabular anteversion. In patients with a stiff spine who cannot retrovert, the surgeon must increase the cup anteversion to prevent posterior impingement and dislocation.

Question 48

A 72-year-old woman with a history of an L2 to pelvis spinal fusion presents for a total hip arthroplasty. How does her multi-level spinal fusion alter her spinopelvic mechanics, and what modification in acetabular component positioning is recommended to prevent dislocation?

Explanation

In a normal spine, sitting induces posterior pelvic tilt, which increases functional acetabular anteversion and clears the anterior impingement plane. A rigid lumbopelvic fusion prevents posterior tilt, increasing the risk of anterior impingement and posterior dislocation when sitting; thus, the cup should be placed in more anteversion and inclination.

Question 49

A 65-year-old man presents with chronic pain 3 years after a total hip arthroplasty. His CRP is 45 mg/L and ESR is 50 mm/hr. Hip aspiration yields cloudy fluid with 4,500 WBCs/µL and 85% polymorphonuclear leukocytes. According to the 2018 ICM criteria, what is the most appropriate management?

Explanation

The patient meets the 2018 ICM criteria for chronic periprosthetic joint infection (elevated CRP, ESR, synovial WBC >3000, PMN >80%). The standard of care for a chronic PJI is a two-stage revision arthroplasty.

Question 50

A 78-year-old woman falls and sustains a periprosthetic femur fracture 8 years after a THA. Radiographs show a fracture around the distal aspect of the femoral stem. The stem is subsided by 1.5 cm and appears loose, but the medial and lateral diaphyseal cortices have excellent bone stock. What is the Vancouver classification and appropriate treatment?

Explanation

A fracture around a loose stem with adequate remaining bone stock is classified as Vancouver B2. The appropriate treatment is bypassing the fracture with a long, porous-coated diaphyseal engaging stem to achieve stability.

Question 51

A 25-year-old male athlete presents with deep groin pain worsened by hip flexion and internal rotation. A cross-table lateral radiograph demonstrates an alpha angle of 65 degrees. What is the primary pathomechanical process occurring in this patient's hip?

Explanation

An elevated alpha angle (>55 degrees) is indicative of Cam-type femoroacetabular impingement (FAI). This results from abnormal contact between an aspherical femoral head-neck junction and the acetabular rim, causing chondral delamination and labral tears.

Question 52

A 6-week-old female is being treated with a Pavlik harness for developmental dysplasia of the hip. After 2 weeks, her parents note that she is no longer actively kicking or extending the knee on the treated side. What is the most appropriate next step in management?

Explanation

Decreased active knee extension in a Pavlik harness indicates a femoral nerve palsy, typically caused by excessive hip flexion. The harness must be removed to prevent permanent nerve damage, and the palsy usually resolves with observation.

Question 53

A 32-year-old man presents with a 4-month history of groin pain. Radiographs demonstrate patchy sclerosis in the superolateral femoral head, but the contour of the head is perfectly spherical with no crescent sign. MRI confirms a localized area of osteonecrosis. What is the most appropriate initial surgical intervention?

Explanation

The patient has pre-collapse avascular necrosis (Ficat Stage II) of the femoral head. Core decompression is indicated to reduce intraosseous pressure, relieve pain, and potentially halt progression of the disease.

Question 54

A 45-year-old active man undergoes a total hip arthroplasty (THA). The surgeon selects a ceramic-on-ceramic bearing surface. Which of the following is a recognized unique complication associated with this specific bearing choice?

Explanation

Ceramic-on-ceramic bearings offer excellent wear properties but are uniquely associated with audible squeaking in up to 10% of patients. Trunnionosis and elevated cobalt are associated with metal components.

Question 55

A 72-year-old woman presents to the emergency department after a mechanical fall. She had a THA 10 years ago. Radiographs reveal a periprosthetic femur fracture around the stem. The fracture is at the level of the stem tip, the stem is loose, and there is poor proximal bone stock. According to the Vancouver classification, what is the most appropriate management?

Explanation

This describes a Vancouver B3 fracture (loose stem, poor proximal bone stock). The most reliable treatment is bypassing the deficient proximal bone and achieving fixation distally using a fluted, tapered cementless stem.

Question 56

A 60-year-old man with a metal-on-metal THA placed 8 years ago presents with worsening groin pain. Inflammatory markers are normal. Serum cobalt and chromium levels are significantly elevated. MARS MRI shows a large cystic mass communicating with the joint. What is the most appropriate next step in management?

Explanation

The patient has an adverse local tissue reaction (ALVAL/pseudotumor) secondary to metal-on-metal wear. Definitive treatment requires revision of the bearing surface to a non-metal-on-metal articulation.

Question 57

A 65-year-old woman undergoes a direct anterior approach THA. Postoperatively, she reports a patch of numbness over the anterolateral aspect of her proximal thigh. Motor function is intact. Which nerve was most likely injured during the surgical exposure?

Explanation

The lateral femoral cutaneous nerve is at risk during the direct anterior approach (Smith-Petersen interval) to the hip, leading to sensory loss over the anterolateral thigh without motor deficits.

Question 58

A 50-year-old man presents with persistent anterior groin pain 1 year after an uncomplicated THA. The pain is reproducible with active straight leg raise and resisted hip flexion. Radiographs demonstrate a well-fixed cup with 5 degrees of retroversion and prominent anterior overhang. A diagnostic injection of local anesthetic into the psoas sheath provides complete temporary relief. If conservative management fails, what is the best surgical intervention?

Explanation

The patient has iliopsoas impingement secondary to a malpositioned (retroverted) and prominent acetabular cup. While tenotomy can be tried, the definitive treatment for symptomatic significant component malposition is cup revision.

Question 59

A 30-year-old woman with systemic lupus erythematosus on chronic corticosteroids presents with severe left hip pain. Radiographs reveal a crescent sign and early flattening of the femoral head. An MRI confirms osteonecrosis with 3 mm of depression. What is the most appropriate definitive management?

Explanation

Once structural collapse of the femoral head has occurred (Ficat stage III, >2mm depression), joint-preserving procedures like core decompression are highly likely to fail. THA is the most reliable treatment in this setting.

Question 60

A 68-year-old man develops recurrent posterior dislocations of his THA. He has a well-fixed cementless cup positioned in 45 degrees of inclination and 20 degrees of anteversion, and a well-fixed cementless stem. His abductor musculature is severely degenerated on MRI. Which of the following is the most appropriate surgical strategy to restore stability?

Explanation

In the setting of recurrent instability with well-positioned components and severe abductor deficiency, a constrained acetabular liner or a dual mobility construct is the most appropriate surgical option to prevent further dislocations.

Question 61

A 42-year-old man presents with deep groin pain worsened by deep hip flexion and internal rotation. AP pelvis radiograph demonstrates a prominent crossover sign and a lateral center edge angle of 45 degrees. Alpha angle is 45 degrees. Which of the following best describes the pathomechanics of his condition?

Explanation

A crossover sign and elevated lateral center edge angle (>39 degrees) are indicative of pincer-type femoroacetabular impingement (FAI), which is characterized by focal or global overcoverage of the femoral head by the acetabulum.

Question 62

Which of the following intervals is utilized during the direct lateral (Hardinge) approach to the hip?

Explanation

The direct lateral (Hardinge) approach splits the anterior third of the gluteus medius and the vastus lateralis. This approach places the superior gluteal nerve at risk if the split extends more than 5 cm proximal to the greater trochanter.

Question 63

A 55-year-old man undergoes a standard primary THA using a non-cemented femoral stem. Six months postoperatively, he complains of reproducible mid-thigh pain that occurs only with weight-bearing and resolves with rest. Radiographs show a well-positioned stem with reactive cortical hypertrophy at the stem tip and no radiolucent lines. What is the most likely diagnosis?

Explanation

End-of-stem thigh pain typically occurs with cementless, stiff, extensively porous-coated stems due to a modulus of elasticity mismatch between the rigid metal stem and the flexible femoral diaphysis.

Question 64

A 78-year-old man presents with an acute periprosthetic joint infection of his THA. His index surgery was 3 weeks ago. He is medically stable. Aspiration yields purulent fluid with a WBC count of 85,000 cells/uL. What is the most appropriate management?

Explanation

Acute postoperative periprosthetic joint infections (occurring within 4 weeks of the index procedure) with well-fixed components are best managed with aggressive open debridement, modular exchange (DAIR), and IV antibiotics.

Question 65

A 35-year-old woman with a history of untreated developmental dysplasia of the hip (DDH) is planned for a THA. Preoperative planning reveals a Crowe Type IV dysplasia. Which of the following surgical techniques is most likely required to successfully reconstruct this hip and avoid sciatic nerve palsy?

Explanation

Crowe Type IV DDH features a high dislocation of the femoral head. Bringing the hip down to the true acetabulum often requires a subtrochanteric shortening osteotomy to safely reduce the joint and prevent stretching the sciatic nerve.

Question 66

A 62-year-old man presents with left hip pain 5 years after a conventional metal-on-polyethylene THA. Radiographs show well-fixed components. Serum cobalt level is markedly elevated, but chromium is normal. MRI shows a large periprosthetic fluid collection. What is the most likely source of the elevated metal ions?

Explanation

Elevated cobalt levels out of proportion to chromium in a patient with a metal-on-polyethylene bearing strongly suggests mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction.

Question 67

In the setting of primary THA, which of the following best describes the principle advantage of a dual-mobility construct compared to a standard unconstrained bearing?

Explanation

Dual-mobility cups utilize a small femoral head captive within a larger mobile polyethylene liner. This creates a larger effective head size, increasing the jump distance and significantly reducing the risk of dislocation.

Question 68

A patient who received a metal-on-polyethylene THA 15 years ago demonstrates eccentric wear of the polyethylene liner and massive expansile osteolytic lesions in the proximal femur. The stem remains well-fixed. What is the primary biological mediator initiating this osteolytic process?

Explanation

Aseptic loosening and osteolysis in conventional polyethylene bearings are driven by macrophage phagocytosis of submicron polyethylene wear particles. This triggers an inflammatory cascade resulting in bone resorption.

Question 69

A 45-year-old active man complains of a painless squeaking sound from his ceramic-on-ceramic total hip arthroplasty (THA) placed 2 years ago. Radiographs show a well-fixed cup with 60 degrees of abduction and 25 degrees of anteversion. What is the most likely cause of this acoustic phenomenon?

Explanation

Squeaking in ceramic-on-ceramic hips is highly correlated with component malposition, particularly excessive cup abduction or anteversion leading to edge loading. If painless and without signs of wear or fracture, reassurance and observation are typically recommended.

Question 70

A 55-year-old man presents with groin pain 6 years after a metal-on-polyethylene THA utilizing a 36-mm cobalt-chrome head on a titanium alloy stem. MRI shows a solid cystic mass with thick walls. Serum cobalt levels are markedly elevated compared to chromium. What is the most likely diagnosis?

Explanation

MACC, or trunnionosis, occurs at the modular head-neck junction, often seen with large cobalt-chrome heads on titanium stems. It classically presents with a higher ratio of serum cobalt to chromium and can cause an adverse local tissue reaction (pseudotumor).

Question 71

A 72-year-old woman with Parkinson's disease presents with her third posterior dislocation of a primary THA within 6 months. Her abductor mechanism is grossly intact. Radiographs show acceptable component positioning. What is the most appropriate surgical intervention?

Explanation

Dual mobility constructs provide excellent stability and are the preferred option for recurrent instability in patients with an intact abductor mechanism, particularly in high-risk neuromuscular patients. Constrained liners have a higher failure rate and are generally reserved for deficient abductors.

Question 72

A 65-year-old man is evaluated for a painful THA 3 years postoperatively. He has been taking oral antibiotics for a presumed urinary tract infection. Serum ESR and CRP are equivocal. Joint aspiration yields a WBC count of 2,500 cells/microL with 70% PMNs. Which of the following synovial fluid biomarkers is most specific for diagnosing a periprosthetic joint infection in this setting?

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils that is a highly specific biomarker for periprosthetic joint infection. Its accuracy remains robust and is minimally affected by concurrent systemic antibiotic administration.

Question 73

A 24-year-old male hockey player presents with gradual onset of deep groin pain exacerbated by hip flexion and internal rotation. Radiographs reveal an alpha angle of 65 degrees and normal acetabular coverage. Which of the following pathologic mechanisms is most likely responsible for his symptoms?

Explanation

Cam impingement is characterized by an abnormal femoral head-neck junction (high alpha angle) that forcefully enters the acetabulum during flexion. This creates tremendous shear forces that lead to anterosuperior chondral delamination and inside-out labral tears.

Question 74

During preoperative planning for a revision THA, radiographs demonstrate an acetabular defect with superior migration of the hip center greater than 3 cm, severe ischial lysis, and destruction of the teardrop. According to the Paprosky classification, what type of defect is present, and what is the optimal reconstructive option?

Explanation

Paprosky 3B defects involve severe bone loss with destruction of the teardrop, Kohler's line, and ischium, often with pelvic discontinuity. Management typically requires custom triflange implants, cup-cage constructs, or massive structural allografts to achieve stability.

Question 75

A 62-year-old woman undergoes a primary THA via a direct anterior approach. Postoperatively, she reports numbness and a burning sensation over the anterolateral aspect of her operative thigh. Which anatomic interval was most likely utilized, leading to this specific nerve injury risk?

Explanation

The direct anterior (Smith-Petersen) approach exploits the internervous plane between the sartorius (femoral nerve) and tensor fasciae latae (superior gluteal nerve). The lateral femoral cutaneous nerve crosses this interval and is at risk for iatrogenic injury.

Question 76

A 50-year-old man who underwent a metal-on-metal THA 8 years ago presents for a routine follow-up. He is completely asymptomatic and highly active. Radiographs show well-fixed components. Serum cobalt levels are 8.5 ppb (normal <1 ppb). What is the most appropriate next step in management?

Explanation

For patients with metal-on-metal THA and significantly elevated metal ion levels (>7 ppb), current guidelines recommend advanced cross-sectional imaging, ideally a MARS MRI. This evaluates for asymptomatic adverse local tissue reactions (ALTR) or pseudotumors.

Question 77

A 35-year-old man on chronic corticosteroids presents with acute bilateral hip pain. MRI demonstrates diffuse bone marrow edema in the right proximal femur with a subchondral band-like lesion, and no collapse. What is the most appropriate initial management for the right hip?

Explanation

For symptomatic, pre-collapse osteonecrosis of the femoral head (Ficat Stage I or II), core decompression is the standard initial joint-preserving surgical treatment. It reduces intraosseous pressure and aims to prevent progression to subchondral collapse.

Question 78

A 12-year-old boy with hypothyroidism and a BMI of 35 presents with an unstable slipped capital femoral epiphysis (SCFE) of the left hip. Radiographs show a moderate slip. Which of the following factors is the strongest indication for prophylactic in situ pinning of the contralateral right hip?

Explanation

Prophylactic pinning of the contralateral hip is strongly recommended in patients with SCFE who have an underlying endocrinopathy, such as hypothyroidism or renal osteodystrophy. These conditions drastically increase the risk of developing a bilateral slip.

Question 79

A 22-year-old woman presents with activity-related anterior hip pain. Radiographs reveal a lateral center-edge angle of 15 degrees, an intact Shenton's line, and a congruent joint space without advanced osteoarthritis. The triradiate cartilages are closed. What is the most appropriate surgical intervention?

Explanation

Periacetabular osteotomy (PAO) is the gold standard treatment for symptomatic acetabular dysplasia in young adults with closed triradiate cartilages. It allows significant multidirectional reorientation of the acetabulum while preserving the posterior column.

Question 80

A 30-year-old man sustains a completely displaced, high-angle (Pauwels Type III) femoral neck fracture. He is medically stable. What fixation method provides the most biomechanically stable construct to resist the high shear forces inherent in this fracture pattern?

Explanation

Pauwels Type III fractures have a vertical fracture line (angle >50 degrees) subjected to high shear forces. A fixed-angle device, such as a sliding hip screw combined with a derotational screw, provides superior biomechanical stability compared to multiple parallel cancellous screws.

Question 81

A 68-year-old woman complains of chronic lateral hip pain and a new Trendelenburg lurch. She has failed physical therapy and corticosteroid injections for presumed greater trochanteric pain syndrome. MRI confirms a full-thickness retraction of the gluteus medius tendon without fatty infiltration. What is the most appropriate next step in management?

Explanation

A full-thickness gluteus medius tear (often termed "rotator cuff tear of the hip") without severe fatty degeneration that fails conservative management is a strong indication for surgical repair. This effectively restores abductor mechanics and resolves the Trendelenburg gait.

Question 82

A healthy 65-year-old man is scheduled for an elective THA for primary osteoarthritis. He has no personal or family history of venous thromboembolism. According to the AAOS clinical practice guidelines, which of the following regimens is highly utilized and acceptable for VTE prophylaxis in this patient?

Explanation

Current AAOS guidelines support the use of aspirin for VTE prophylaxis in standard-risk patients undergoing total joint arthroplasty. Aspirin provides adequate protection against VTE while minimizing the risk of postoperative bleeding complications.

Question 83

During revision of a metal-on-metal THA for a symptomatic pseudotumor, tissue samples are sent for histopathology. Which of the following histologic findings is characteristic of an adverse local tissue reaction (ALTR/ALVAL) associated with this bearing surface?

Explanation

Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesions (ALVAL), a form of ALTR seen in metal-on-metal implants, classically present with a perivascular lymphocytic infiltrate and areas of extensive macroscopic tissue necrosis on histology.

Question 84

A 60-year-old woman is 6 weeks post-primary THA. She complains her operative leg feels 1 cm longer. Clinical examination and standing radiographs confirm a 1 cm lengthening on the operative side. Her hip is completely stable. What is the most appropriate initial management?

Explanation

Perceived leg length discrepancy is very common in the early postoperative period after THA, often due to pelvic obliquity and resolving muscle contractures. Reassurance and observation for 3-6 months is appropriate, as most patients accommodate over time.

Question 85

A 65-year-old man with a solid L2-S1 spinal fusion undergoes a total hip arthroplasty. Preoperative standing and sitting lateral radiographs demonstrate less than 5 degrees of change in pelvic tilt. Based on his spinopelvic mechanics, what is the most appropriate acetabular component positioning strategy?

Explanation

Patients with a stiff lumbosacral spine fail to increase pelvic tilt during sitting, creating a high risk of anterior impingement and posterior dislocation. Compensating by increasing acetabular cup anteversion and inclination helps accommodate the fixed pelvis and prevents posterior instability during flexion.

Question 86

A 72-year-old woman presents to the emergency department after a fall. Radiographs show a displaced fracture around the distal aspect of a cemented femoral stem placed 8 years ago. The cement mantle is fractured, and the stem has subsided 2 cm. What is the most appropriate management?

Explanation

This is a Vancouver B2 periprosthetic femur fracture, characterized by a fracture around or just below a loose stem with adequate bone stock. The standard of care is revision arthroplasty using a diaphyseal-engaging, long cementless stem with cables or cerclage wires.

Question 87

A 68-year-old man presents with progressive groin pain and a palpable mass 6 years after a metal-on-polyethylene total hip arthroplasty. Laboratory testing reveals normal ESR and CRP, but elevated serum cobalt levels with normal chromium levels. MRI demonstrates a large cystic fluid collection. What is the most likely etiology of his symptoms?

Explanation

Trunnionosis results from mechanically assisted crevice corrosion at the modular head-neck junction (taper), releasing cobalt out of proportion to chromium. It can cause an adverse local tissue reaction (ALTR) presenting as a pseudotumor, even in metal-on-polyethylene implants.

Question 88

During a direct anterior approach for a total hip arthroplasty, the surgeon develops the internervous plane between the tensor fasciae latae and the sartorius. Which of the following neurologic structures is at greatest risk of injury during the superficial dissection?

Explanation

The direct anterior approach utilizes the internervous plane between the sartorius (femoral nerve) and tensor fasciae latae (superior gluteal nerve). The lateral femoral cutaneous nerve courses superficially over the sartorius and is highly vulnerable to traction or transection during the superficial dissection.

Question 89

A 28-year-old man sustains a highly vertical (Pauwels type III) basicervical femoral neck fracture following a motor vehicle collision. Which of the following internal fixation constructs provides the highest biomechanical stability against vertical shear forces?

Explanation

Vertical femoral neck fractures (Pauwels III) in young adults experience high shear forces leading to varus collapse. A fixed-angle device, such as a sliding hip screw with a derotation screw, provides superior biomechanical stability against vertical shear compared to multiple cancellous screws.

Question 90

A 12-year-old boy with a BMI in the 98th percentile is diagnosed with a severe, slipped capital femoral epiphysis (SCFE) of the left hip. Radiographs of the right hip are normal. According to current evidence, which of the following is the strongest indication for prophylactic in situ pinning of his contralateral asymptomatic right hip?

Explanation

The status of the triradiate cartilage is a primary indicator of skeletal maturity and the risk of a contralateral slip. Open triradiate cartilages indicate significant remaining growth, making it the strongest indication for prophylactic contralateral pinning in SCFE.

Question 91

A 62-year-old woman is evaluated for a painful total hip arthroplasty. Hip aspiration yields synovial fluid with a WBC count of 2,800 cells/mcL and 60% polymorphonuclear cells. The synovial fluid alpha-defensin immunoassay is positive. Which of the following accurately describes the utility of the alpha-defensin test in this setting?

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. In the setting of periprosthetic joint infection (PJI), the synovial fluid alpha-defensin test is highly sensitive and specific, and it is not adversely affected by the prior use of antibiotics or bloody aspirates.

Question 92

A 24-year-old male athlete presents with chronic groin pain exacerbated by hip flexion and internal rotation. An AP pelvis radiograph demonstrates a pistol grip deformity of the proximal femur. Which of the following radiographic parameters is most likely to be abnormal in this patient?

Explanation

A pistol grip deformity is classic for Cam-type femoroacetabular impingement (FAI), which is caused by reduced femoral head-neck offset. The alpha angle measures this deformity, with an angle greater than 50-55 degrees indicating abnormal Cam morphology.

Question 93

A 35-year-old woman with a history of chronic corticosteroid use presents with insidious onset of anterior hip pain. MRI reveals a well-demarcated subchondral lesion in the anterosuperior femoral head with a double-line sign on T2-weighted images, without evidence of subchondral collapse. What is the most appropriate initial surgical intervention?

Explanation

The patient has pre-collapse avascular necrosis (AVN) of the femoral head (Ficat Stage I or II). Core decompression is the most appropriate surgical treatment to relieve intraosseous pressure and promote revascularization prior to the development of subchondral collapse.

Question 94

A 45-year-old woman with Crowe Type IV developmental dysplasia of the hip is scheduled for a total hip arthroplasty. Her femoral head is completely dislocated superior to the true acetabulum. If the acetabular component is placed in the true acetabulum, which of the following is most likely required to achieve reduction and prevent nerve injury?

Explanation

In Crowe IV dysplasia, the femoral head is dislocated proximally. Bringing the hip down to the true acetabulum significantly lengthens the leg, placing the sciatic nerve at high risk for traction injury, which necessitates a subtrochanteric femoral shortening osteotomy.

Question 95

A 70-year-old man underwent a primary right total hip arthroplasty via a direct lateral (Hardinge) approach. Postoperatively, he exhibits a pronounced Trendelenburg lurch and inability to actively abduct the right hip against gravity. Injury to which of the following structures most likely occurred during the surgical exposure?

Explanation

The direct lateral (Hardinge) approach involves splitting the gluteus medius and minimus. Proximal extension of this split greater than 3 to 5 cm from the greater trochanter places the superior gluteal nerve at risk, potentially leading to abductor paralysis and a Trendelenburg gait.

Question 96

A 42-year-old woman with advanced primary osteoarthritis of the hip desires a metal-on-metal hip resurfacing arthroplasty to maintain her high-impact athletic lifestyle. Which of the following patient factors represents an absolute contraindication to this specific procedure?

Explanation

Metal-on-metal hip resurfacing requires a bearing surface containing cobalt and chromium. Known metal hypersensitivity, advanced chronic kidney disease, and severe osteopenia/osteoporosis are absolute contraindications to this procedure.

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

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

Key Takeaway

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

Chapter Index