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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 191 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 3801

Topic: Total Hip Arthroplasty (THA)

A 65-year-old woman experiences recurrent anterior dislocations after a primary total hip arthroplasty performed via a posterior approach. Radiographs demonstrate that the acetabular component is placed in 35 degrees of anteversion and 50 degrees of inclination. The femoral stem is placed in 25 degrees of anteversion. What is the most appropriate definitive management?

. Revision of the acetabular component to decrease anteversion and inclination
. Revision of the femoral stem to increase anteversion
. Application of a hip abduction brace for 6 weeks
. Revision to a constrained liner without changing cup position
. Soft tissue reefing of the anterior capsule

Correct Answer & Explanation

. Revision of the acetabular component to decrease anteversion and inclination

Explanation

The patient's combined anteversion (cup 35 degrees + stem 25 degrees = 60 degrees) is excessively high, predisposing her to anterior dislocation. The cup is also excessively abducted (50 degrees). Normal combined anteversion should be approximately 25-35 degrees (e.g., cup 15-20 degrees, stem 10-15 degrees) according to the widely accepted Lewinnek or combined safe zones. To correct this mechanical instability, the acetabular component needs to be revised to decrease both anteversion and inclination.

Question 3802

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old man presents with progressive groin pain 7 years after a primary total hip arthroplasty with a large diameter metal head on a highly cross-linked polyethylene liner.

Serum cobalt levels are significantly elevated compared to chromium. Joint aspiration yields sterile, cloudy fluid. What is the most likely source of the elevated metal ions?

. Polyethylene wear debris
. Fretting and corrosion at the modular head-neck junction
. Impingement of the neck on the acetabular rim
. Unrecognized metal-on-metal articulation
. Galvanic corrosion at the stem-cement interface

Correct Answer & Explanation

. Fretting and corrosion at the modular head-neck junction

Explanation

Elevated serum cobalt levels (often with Cobalt > Chromium) in the setting of a metal-on-polyethylene THA point toward mechanically assisted crevice corrosion (MACC), also known as trunnionosis, at the modular head-neck taper junction. This adverse local tissue reaction (ALTR) is increasingly recognized, particularly with large metal heads which exert higher torque forces on the trunnion.

Question 3803

Topic: 3. Adult Reconstruction (Hip & Knee)
A 72-year-old woman is undergoing revision total hip arthroplasty for aseptic loosening of her acetabular component. Intraoperatively, the superior and inferior hemipelvis are found to move independently. Which of the following reconstruction techniques provides the most reliable long-term biologic fixation and stability for this specific defect?
. Placement of a jumbo hemispherical highly porous titanium cup with multiple screws
. Impaction bone grafting with a cemented polyethylene cup
. A custom triflange acetabular component or a cup-cage construct
. Bipolar hemiarthroplasty articulating with the native bone
. Standard cementless cup with structural allograft

Correct Answer & Explanation

. A custom triflange acetabular component or a cup-cage construct

Explanation

The finding of independent movement between the superior and inferior hemipelvis defines a pelvic discontinuity (Paprosky type IIIb). Achieving durable fixation requires rigid stabilization of the discontinuity. Standard hemispherical cups (even jumbo or highly porous ones) have high failure rates unless the discontinuity is bridged and compressed. Custom triflange acetabular components or cup-cage constructs (distraction approach) offer the most reliable stability and promote healing or durable bridging of the discontinuity.

Question 3804

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following patients is the most appropriate candidate for a metal-on-metal hip resurfacing arthroplasty?

. A 40-year-old woman with developmental dysplasia of the hip and a 2.5 cm leg length discrepancy
. A 45-year-old man with primary osteoarthritis and large subchondral cysts (>1.5 cm) in the femoral head
. A 50-year-old man with primary osteoarthritis, normal femoral geometry, and solid bone stock
. A 55-year-old woman with rheumatoid arthritis and osteopenia
. A 60-year-old man with avascular necrosis and 40% head involvement

Correct Answer & Explanation

. A 50-year-old man with primary osteoarthritis, normal femoral geometry, and solid bone stock

Explanation

The ideal candidate for a metal-on-metal hip resurfacing is a young, active male (<55-60 years old) with primary osteoarthritis, normal proximal femoral geometry, and good bone quality. Women, patients with significant leg length discrepancy, large subchondral cysts (>1 cm), AVN with >30% head involvement, or poor bone quality (e.g., RA, osteopenia) have unacceptably high failure rates (due to femoral neck fracture or adverse local tissue reactions) and are generally considered contraindicated for this procedure.

Question 3805

Topic: 3. Adult Reconstruction (Hip & Knee)
A 38-year-old man on chronic corticosteroids for systemic lupus erythematosus presents with a 4-month history of progressive right groin pain. Radiographs of the right hip show a subchondral radiolucent line (crescent sign), but no flattening of the femoral head. What is the most appropriate initial management for this patient?
. Core decompression with or without bone grafting
. Total hip arthroplasty
. Restricted weight-bearing and bisphosphonates
. Vascularized free fibular transfer
. Non-vascularized structural allograft

Correct Answer & Explanation

. Total hip arthroplasty

Explanation

The presence of a crescent sign indicates subchondral collapse (Ficat stage III / Steinberg stage III). Once subchondral collapse has occurred, head-preserving procedures like core decompression have an unacceptably high failure rate. Total hip arthroplasty is the most appropriate, reliable, and definitive treatment for symptomatic, collapsed avascular necrosis (Stage III or IV) in this setting.

Question 3806

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old woman sustains a fall and presents with a periprosthetic femur fracture around her cemented polished taper-slip total hip arthroplasty stem.

Radiographs show a fracture at the tip of the stem. The stem appears subsided and loose within the cement mantle, but the surrounding proximal femoral bone stock is of good quality. How should this fracture be classified and managed?

. Vancouver A; treated with cerclage wiring alone
. Vancouver B1; treated with open reduction and internal fixation with a locking plate
. Vancouver B2; treated with revision to a long, fluted, tapered cementless stem
. Vancouver B3; treated with a proximal femoral replacement
. Vancouver C; treated with open reduction and internal fixation

Correct Answer & Explanation

. Vancouver B2; treated with revision to a long, fluted, tapered cementless stem

Explanation

The fracture is around the tip of the stem, making it a Vancouver B. The stem is loose (subsided), which differentiates B2/B3 from B1 (where the stem is well-fixed). Since the proximal bone stock is described as good quality, it is classified as a Vancouver B2 fracture. The standard of care for a B2 periprosthetic fracture is revision of the femoral component, typically using a long, fluted, tapered cementless stem that bypasses the fracture distally by at least two cortical diameters.

Question 3807

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old man presents to the emergency department after a ground-level fall. He underwent a primary cementless total hip arthroplasty 5 years ago. Radiographs demonstrate a displaced fracture around the femoral stem extending just distal to the lesser trochanter. The stem appears subsided by 2 cm compared to previous radiographs. What is the most appropriate definitive management?

. Open reduction and internal fixation with a lateral locking plate and cerclage wires
. Revision to a fully porous-coated cylindrical long stem
. Revision to a fluted, tapered, modular titanium stem
. Cortical strut allografting alone
. Closed reduction and spica casting

Correct Answer & Explanation

. Revision to a fluted, tapered, modular titanium stem

Explanation

This is a Vancouver B2 periprosthetic femur fracture, characterized by a fracture around a loose stem with adequate distal bone stock. The standard of care for a B2 fracture is revision of the femoral component to bypass the fracture, typically using a fluted, tapered, titanium stem (modular or non-modular) to achieve rigid distal diaphyseal fixation. ORIF alone is contraindicated due to the loose implant.

Question 3808

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man presents with progressive right groin pain 6 years after a metal-on-polyethylene total hip arthroplasty utilizing a cobalt-chrome modular head on a titanium alloy stem. Inflammatory markers are normal and aspiration yields no growth. A MARS MRI reveals a solid and cystic mass communicating with the joint. Serum cobalt is 12 ppb, and chromium is 2 ppb. What is the most likely etiology of this patient's symptoms?

. Aseptic loosening of the acetabular component
. Polyethylene wear-induced osteolysis
. Mechanically assisted crevice corrosion at the head-neck junction
. Undiagnosed low-grade periprosthetic joint infection
. Impingement of the iliopsoas tendon

Correct Answer & Explanation

. Mechanically assisted crevice corrosion at the head-neck junction

Explanation

The scenario describes an adverse local tissue reaction (ALTR) secondary to mechanically assisted crevice corrosion (MACC) at the head-neck junction, also known as trunnionosis. This is characterized by disproportionately elevated cobalt relative to chromium (often > 10:1 ratio) in metal-on-polyethylene THA with a CoCr head and Ti stem. MARS MRI typically shows a pseudotumor.

Question 3809

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old woman with a history of recurrent instability underwent revision total hip arthroplasty to a modular dual mobility articulation 3 years ago. She now presents with new-onset clicking and groin pain. Radiographs demonstrate an asymmetric, eccentric position of the femoral head within the radiolucent polyethylene bubble, but the large polyethylene liner remains located within the metal acetabular shell. What is the mechanism of this specific complication?

. Failure of the locking mechanism between the metal shell and the polyethylene liner
. Disengagement of the inner prosthetic head from the mobile polyethylene liner
. Wear of the backside of the metal shell
. Subluxation of the entire dual-mobility construct out of the acetabular shell
. Impingement of the greater trochanter on the ischium

Correct Answer & Explanation

. Disengagement of the inner prosthetic head from the mobile polyethylene liner

Explanation

The scenario describes an intraprosthetic dislocation (IPD), a complication specific to dual mobility (DM) constructs. It occurs when the inner (smaller) prosthetic head disengages from the captive mobile polyethylene liner. This is often caused by wear or failure of the polyethylene retentive rim, allowing the head to escape. Radiographically, it appears as an asymmetric 'bubble' sign where the femoral head is no longer concentric within the polyethylene liner.

Question 3810

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old woman complains of anterior groin pain when rising from a seated position, 1 year after an uncomplicated primary total hip arthroplasty. Her symptoms are reproducible with active straight leg raise and resisted hip flexion. An image from her cross-sectional study is shown.

Diagnostic injection of the iliopsoas bursa provides complete, temporary relief. Which acetabular component position is the most common cause of this pathology?

. Excessive retroversion
. Excessive anteversion
. Insufficient inclination
. Anterior overhang of the cup
. Posterior overhang of the cup

Correct Answer & Explanation

. Anterior overhang of the cup

Explanation

Iliopsoas impingement after THA typically presents with anterior groin pain that is worse with active hip flexion. It is most commonly caused by an anteriorly prominent or overhanging acetabular component. An anterior overhang greater than 8mm is highly predictive of irritating the iliopsoas tendon as it crosses the joint.

Question 3811

Topic: Total Hip Arthroplasty (THA)

A 50-year-old active man with a ceramic-on-ceramic total hip arthroplasty reports a high-pitched squeaking noise from his hip during deep flexion activities. He is otherwise asymptomatic. Which of the following factors has been most strongly associated with squeaking in ceramic-on-ceramic THA?

. Femoral stem retroversion
. Edge loading due to component malposition
. Micro-separation during the swing phase
. Inadequate taper impaction
. Third-body wear from retained cement

Correct Answer & Explanation

. Edge loading due to component malposition

Explanation

Squeaking in ceramic-on-ceramic (CoC) total hip arthroplasty is a well-documented phenomenon. It is most strongly associated with edge loading, which typically results from component malposition (e.g., excessive cup inclination or version). This leads to impingement, stripe wear on the ceramic head, and subsequent loss of fluid film lubrication.

Question 3812

Topic: 3. Adult Reconstruction (Hip & Knee)

A 66-year-old woman is evaluated for a loose acetabular component 15 years after total hip arthroplasty. Pelvic radiographs demonstrate superior migration of the hip center by 3.5 cm, complete absence of the teardrop, and disruption of the Kohler line.

During revision surgery, there is less than 30% host bone contact for a hemispherical cup. Which of the following is the most appropriate reconstruction option?

. Jumbo hemispherical porous-coated cup with multiple screws
. Cup-cage construct or custom triflange acetabular component
. Standard hemispherical cup with particulate allograft
. Impaction bone grafting with a cemented polyethylene cup
. Anti-protrusio cage with a cemented polyethylene cup

Correct Answer & Explanation

. Cup-cage construct or custom triflange acetabular component

Explanation

The clinical and radiographic description (superior migration >3cm, disrupted Kohler line, destroyed teardrop, <30% host bone contact) indicates a Paprosky type 3B acetabular defect, representing severe pelvic discontinuity or near-discontinuity. A standard or jumbo uncemented cup will not achieve adequate initial stability or biologic fixation (<50% host bone contact). Reliable durable options for a 3B defect include a cup-cage construct, custom triflange acetabular component, or pelvic distraction with a highly porous metal construct.

Question 3813

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old man presents with acute onset of right hip pain and fever 3 weeks after an uncomplicated primary total hip arthroplasty. The incision is erythematous and draining purulent fluid. Joint aspiration reveals a synovial fluid white blood cell count of 85,000 cells/µL with 92% neutrophils. The implant is radiographically well-fixed. Which of the following is the most appropriate initial surgical management?

. One-stage revision with antibiotic-loaded cement
. Two-stage revision with an articulating spacer
. Debridement, antibiotics, and implant retention (DAIR) with modular head and liner exchange
. Suppressive oral antibiotics and observation
. Resection arthroplasty (Girdlestone procedure)

Correct Answer & Explanation

. Debridement, antibiotics, and implant retention (DAIR) with modular head and liner exchange

Explanation

This patient has an acute early periprosthetic joint infection (within 4 weeks of index surgery). The implants are well-fixed. The most appropriate initial management is a thorough Debridement, Antibiotics, and Implant Retention (DAIR), which MUST include the exchange of modular components (femoral head and polyethylene liner) to access the joint spaces fully and remove biofilm. Two-stage revision is reserved for chronic infections, loose implants, or failure of a prior DAIR.

Question 3814

Topic: 3. Adult Reconstruction (Hip & Knee)

A 69-year-old woman complains of a severe limp and lateral hip pain 18 months after a primary total hip arthroplasty performed via a direct lateral (Hardinge) approach. Physical examination reveals a profound Trendelenburg sign and weakness with resisted hip abduction. MRI with MARS artifact reduction shows a full-thickness avulsion of the gluteus medius and minimus from the greater trochanter with severe fatty infiltration. Which of the following is the most appropriate surgical treatment?

. Primary direct repair with transosseous sutures
. Revision to a constrained acetabular liner
. Gluteus maximus muscle transfer or Achilles tendon allograft reconstruction
. Endoscopic debridement of the peritrochanteric space
. Conversion to a dual mobility articulation

Correct Answer & Explanation

. Gluteus maximus muscle transfer or Achilles tendon allograft reconstruction

Explanation

Chronic, massive abductor mechanism tears post-THA with severe fatty atrophy are generally not amenable to primary direct repair due to tissue retraction and poor muscle quality. Reconstruction options for massive, irreparable tears include a gluteus maximus flap transfer or an Achilles tendon allograft with a bone block to bridge the gap and restore abductor tension. Simply changing the bearing does not restore abductor strength or resolve the Trendelenburg gait.

Question 3815

Topic: 3. Adult Reconstruction (Hip & Knee)
A 55-year-old man underwent a metal-on-metal total hip arthroplasty 10 years ago. He presents with new-onset swelling and a palpable mass in his anterior thigh. Laboratory tests show elevated serum cobalt and chromium levels (>20 ppb). Histological examination of the periprosthetic tissue during revision surgery is most likely to show which of the following?
. Abundant polymorphonuclear leukocytes and fibrin exudate
. Macrophages densely packed with polyethylene wear debris
. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)
. Multinucleated giant cells with extensive caseating granulomas
. Spindle cell proliferation with high mitotic activity

Correct Answer & Explanation

. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL)

Explanation

The patient has a pseudotumor secondary to adverse reaction to metal debris (ARMD) from a metal-on-metal THA. The characteristic histological finding for this type of metal hypersensitivity and toxicity reaction is ALVAL (aseptic lymphocyte-dominated vasculitis-associated lesion). This features a perivascular lymphocytic infiltrate, tissue necrosis, and macrophages containing metal particles, which is distinct from the macrophage-dominated reaction seen with polyethylene particulate disease.

Question 3816

Topic: Total Hip Arthroplasty (THA)

A 65-year-old man presents with recurrent posterior dislocations following a primary total hip arthroplasty (THA) performed via a posterior approach 6 months ago. He has no signs of infection and neurologic exam is intact. Radiographic evaluation and subsequent CT scan demonstrate that the acetabular component is placed in 10 degrees of anteversion and 40 degrees of abduction. The femoral component is noted to be in 10 degrees of retroversion. Which of the following component adjustments during revision surgery would most effectively reduce his risk of future posterior dislocations?

. Decrease acetabular anteversion
. Increase acetabular abduction to 55 degrees
. Increase femoral anteversion
. Decrease femoral offset
. Exchange to a smaller femoral head diameter

Correct Answer & Explanation

. Increase femoral anteversion

Explanation

This patient has recurrent posterior dislocations due to inadequate combined anteversion. The widely accepted target for combined anteversion (acetabular anteversion + femoral anteversion) is approximately 25 to 45 degrees (Widmer's or McKibbin's principles adapted for THA). In this scenario, the acetabular component has 10 degrees of anteversion, and the femoral component has 10 degrees of retroversion (which acts as -10 degrees). Therefore, the combined anteversion is 0 degrees. To restore stability and prevent posterior dislocation, the combined anteversion must be increased. This can be achieved by increasing either the acetabular anteversion or the femoral anteversion. Decreasing offset, decreasing head size, or increasing abduction would either worsen instability or have minimal effect on the underlying version mismatch.

Question 3817

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old man falls and sustains a periprosthetic femur fracture around his cementless femoral stem that was placed 8 years ago.

Radiographs demonstrate a fracture at the tip of the stem. Upon intraoperative evaluation, the femoral stem is grossly loose, but the proximal femoral bone stock remains adequate and supportive. Based on the Vancouver classification system, what is the most appropriate definitive management?

. Open reduction internal fixation (ORIF) with locking plates and cerclage wires
. Revision to a fluted, tapered, cementless stem bypassing the fracture by 2 cortical diameters
. Revision to a standard-length cemented stem
. Proximal femoral replacement
. Cortical strut allografting alone without stem revision

Correct Answer & Explanation

. Revision to a fluted, tapered, cementless stem bypassing the fracture by 2 cortical diameters

Explanation

The scenario describes a Vancouver B2 periprosthetic femur fracture. The Vancouver classification is based on fracture location, implant stability, and bone stock. Type B fractures occur around or just below the stem. A Vancouver B1 fracture has a stable stem; B2 has a loose stem with adequate proximal bone stock; and B3 has a loose stem with poor proximal bone stock. The standard of care for a Vancouver B2 fracture is revision arthroplasty using a long-stemmed implant (typically a fluted, tapered, cementless diaphyseal-engaging stem) that bypasses the most distal aspect of the fracture by at least two cortical diameters, often supplemented with cables or a plate for the fracture itself. ORIF alone (Option A) is reserved for Vancouver B1 fractures. Proximal femoral replacement (Option D) is reserved for Vancouver B3 fractures with non-reconstructable proximal bone.

Question 3818

Topic: 3. Adult Reconstruction (Hip & Knee)
A 59-year-old woman with a metal-on-metal total hip arthroplasty presents with new-onset groin pain and a palpable mass in her anterior thigh. Laboratory studies reveal a serum cobalt level of 14 ppb and chromium of 11 ppb (normal < 1 ppb). An MRI with metal artifact reduction sequence (MARS) demonstrates a large, thick-walled cystic collection communicating with the joint space and extensive tearing of the gluteus medius and minimus tendons. During revision surgery, which of the following component choices and strategies is most appropriate to achieve a stable and functional outcome?
. Isolated exchange of the femoral head and liner
. Revision of acetabular and femoral components utilizing a dual-mobility or constrained articulation
. Synovectomy and retention of all metal hardware
. Two-stage revision with an antibiotic-loaded cement spacer
. Revision to a larger diameter metal-on-metal bearing

Correct Answer & Explanation

. Revision of acetabular and femoral components utilizing a dual-mobility or constrained articulation

Explanation

This patient is presenting with an Adverse Local Tissue Reaction (ALTR), also known as an adverse reaction to metal debris (ARMD) or pseudotumor, secondary to a failing metal-on-metal (MoM) THA. The elevated serum metal ions and MARS MRI findings (cystic mass, abductor destruction) confirm the diagnosis. Because of the extensive soft-tissue damage, particularly to the abductor mechanism, these patients are at a remarkably high risk for postoperative instability and dislocation following revision. The standard of care is a complete revision of the MoM bearing surfaces (both acetabular and femoral components if they are proprietary/monoblock or if the trunnion is damaged) to a non-MoM bearing (e.g., ceramic-on-polyethylene). To manage the high risk of dislocation secondary to abductor deficiency, the use of a dual-mobility construct or constrained liner is highly recommended. Retaining the hardware or exchanging to another MoM bearing is contraindicated.

Question 3819

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man undergoes an uncomplicated primary total hip arthroplasty. During templating and the procedure, the surgeon decides to increase the femoral offset by 10 mm compared to the contralateral native hip, while perfectly equalizing leg lengths. What is the expected biomechanical consequence of this specific modification?

. Increased joint reaction force at the hip
. Increased tension on the greater trochanter leading to trochanteric bursitis
. Decreased abductor muscle moment arm
. Decreased overall joint reaction force
. Medialization of the center of rotation

Correct Answer & Explanation

. Decreased overall joint reaction force

Explanation

Increasing the femoral offset increases the moment arm of the abductor muscles. Because the abductor moment arm is longer, the abductor muscles must generate less force to balance the pelvis during the single-leg stance phase of gait. Since the total joint reaction force is primarily composed of body weight and abductor muscle force, reducing the required abductor force significantly decreases the overall joint reaction force on the hip. It does not medialize the center of rotation (that is determined by the acetabular component).

Question 3820

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with acute severe left hip pain and fever 3 weeks after a prolonged dental procedure. She underwent a left total hip arthroplasty 6 years ago. Aspiration of the hip yields purulent fluid with 70,000 WBC/uL and 94% neutrophils. Radiographs show well-fixed components with no osteolysis. What is the most appropriate management strategy?

. One-stage total revision arthroplasty
. Two-stage revision arthroplasty using an articulating spacer
. Debridement, antibiotics, and implant retention (DAIR) with modular component exchange
. Intravenous antibiotics for 6 weeks followed by lifetime oral suppression
. Resection arthroplasty (Girdlestone procedure)

Correct Answer & Explanation

. Debridement, antibiotics, and implant retention (DAIR) with modular component exchange

Explanation

This patient presents with an acute hematogenous periprosthetic joint infection (symptoms typically <4 weeks in a previously well-functioning, asymptomatic joint). In the setting of an acute hematogenous infection with well-fixed components and intact soft-tissue envelopes, Debridement, Antibiotics, and Implant Retention (DAIR) with exchange of modular components (polyethylene liner and femoral head) is the standard of care. Two-stage revision is indicated for chronic infections or if the components are loose.

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