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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 223 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 4441

Topic: 3. Adult Reconstruction (Hip & Knee)

A 35-year-old female with severe osteopetrosis requires a total hip arthroplasty for debilitating osteoarthritis. What is the primary surgical challenge encountered during femoral preparation in this patient population?

. Excessive intramedullary canal width, making stem sizing difficult.
. Increased risk of intraoperative femoral fracture during reaming and broaching.
. Difficulty achieving distal fixation due to poor bone quality.
. Rapid osseointegration of cementless stems, leading to stress shielding.
. Difficulty with soft tissue closure due to increased muscle bulk.

Correct Answer & Explanation

. Increased risk of intraoperative femoral fracture during reaming and broaching.

Explanation

Osteopetrosis is a rare genetic disorder characterized by abnormally dense, brittle bones due to defective osteoclast function. The primary surgical challenge in THA is the extreme bone density, which makes reaming and broaching the femoral canal extremely difficult. This hard, sclerotic bone increases the risk of intraoperative femoral fracture (B) due to the forces applied during preparation, and can lead to excessive heat generation. The intramedullary canal is typically narrowed, not excessively wide (A). While bone quality is poor in terms of brittleness, the density leads to different challenges than porous bone. Rapid osseointegration (D) and soft tissue issues (E) are not the primary concerns specific to osteopetrosis.

Question 4442

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male undergoes revision THA for severe polyethylene wear and associated periacetabular osteolysis around a well-fixed cementless acetabular shell. The acetabular shell itself appears well-integrated and stable. What is the most appropriate management strategy for this scenario?

. Full revision of both acetabular shell and polyethylene liner.
. Acetabular bone grafting for the osteolytic lesions and exchange of the polyethylene liner only.
. Cementing a new polyethylene liner into the existing worn liner.
. Observational management with serial radiographs to monitor osteolysis progression.
. Conversion to a constrained acetabular liner without addressing the osteolysis.

Correct Answer & Explanation

. Acetabular bone grafting for the osteolytic lesions and exchange of the polyethylene liner only.

Explanation

For well-fixed cementless acetabular shells with isolated polyethylene wear and associated osteolysis, the preferred management is acetabular bone grafting for the osteolytic lesions and exchange of the polyethylene liner only (B). This procedure, known as isolated liner exchange, avoids the morbidity of removing a well-fixed shell and has good success rates if the shell is truly stable. Full revision of the shell (A) is unnecessary and adds risk. Cementing a new liner into an old one (C) is not standard practice for a cementless shell. Observation (D) is inappropriate given active osteolysis. A constrained liner (E) is for instability, not wear or osteolysis, and would not address the underlying bone loss.

Question 4443

Topic: Total Hip Arthroplasty (THA)

Which of the following statements most accurately reflects the current understanding of robotic-assisted total hip arthroplasty (THA) compared to conventional manual THA?

. Robotic-assisted THA consistently results in significantly improved long-term clinical outcomes and implant survival compared to manual THA.
. Robotic-assisted THA universally leads to shorter operative times and reduced blood loss.
. Robotic-assisted THA has been shown to achieve more reproducible and accurate component positioning, particularly for acetabular inclination and anteversion.
. The learning curve for robotic-assisted THA is typically shorter than for conventional manual THA.
. Robotic-assisted THA eliminates the need for intraoperative fluoroscopy or conventional radiographic templating.

Correct Answer & Explanation

. Robotic-assisted THA has been shown to achieve more reproducible and accurate component positioning, particularly for acetabular inclination and anteversion.

Explanation

While long-term clinical superiority of robotic-assisted THA over conventional THA (A) is still being investigated, current evidence strongly supports that robotic systems achieve more reproducible and accurate component positioning, especially for acetabular inclination and anteversion (C). This precision can potentially reduce complications like dislocation and impingement. Operative times may initially be longer during the learning curve (B, D) and blood loss is not consistently reduced. Robotic assistance often complements, rather than eliminates, conventional templating and sometimes requires intraoperative imaging for registration (E).

Question 4444

Topic: Total Hip Arthroplasty (THA)

A 65-year-old active female undergoes primary THA. She has a high-riding greater trochanter and significant hip abductor weakness despite no overt abductor tear. The surgeon performs a direct anterior approach. What is a potential unique advantage of a modified direct anterior approach, specifically related to abductor function, in this patient compared to a standard posterior or lateral approach?

. It allows for better visualization of the sciatic nerve, reducing nerve injury risk.
. It facilitates a more accurate leg length assessment during surgery.
. It preserves the abductor muscles by working between the sartorius and tensor fascia lata, potentially aiding in quicker recovery of abductor strength.
. It avoids the need for external rotation of the leg, reducing femoral head fracture risk.
. It provides superior exposure for acetabular reconstruction in complex revision cases.

Correct Answer & Explanation

. It preserves the abductor muscles by working between the sartorius and tensor fascia lata, potentially aiding in quicker recovery of abductor strength.

Explanation

The direct anterior approach (DAA) is unique in that it is an intermuscular and internervous interval approach, typically done between the tensor fascia lata (innervated by superior gluteal nerve) and the sartorius (innervated by femoral nerve). This approach largely preserves the hip abductor mechanism (gluteus medius and minimus) and their insertions, as well as the external rotators (C). This can be particularly advantageous in patients with pre-existing abductor weakness, potentially leading to quicker recovery of abductor strength and reduced risk of postoperative limp or abductor tears, compared to approaches that involve detaching or splitting these muscles (e.g., transtrochanteric, direct lateral, or posterior approach with repair). Visualization of the sciatic nerve (A) is typically better with a posterior approach. Leg length assessment (B) can be achieved with various approaches, often with aids. External rotation (D) is typically performed for femoral preparation in a DAA. Superior exposure for complex revision (E) is often better achieved with extensile posterior or lateral approaches.

Question 4445

Topic: 3. Adult Reconstruction (Hip & Knee)
A 58-year-old male presents for revision total hip arthroplasty (THA) due to aseptic loosening of his acetabular component. Intraoperative assessment reveals a Paprosky Type IIIB acetabular defect, characterized by significant segmental loss and superior migration beyond the tear drop. The anterior and posterior columns are compromised, but some host bone stock remains. What is the most appropriate reconstructive option for this acetabular defect?
. Standard uncemented hemispheric cup with multiple screws
. Reinforcement cage with bulk structural allograft and cemented polyethylene liner
. Highly porous uncemented cup with adjunctive augments and screws
. Impaction bone grafting with a cemented polyethylene cup
. Custom triflange acetabular component

Correct Answer & Explanation

. Highly porous uncemented cup with adjunctive augments and screws

Explanation

For Paprosky Type IIIB acetabular defects, which involve significant segmental loss and often column discontinuity, a standard hemispheric cup is insufficient. Impaction bone grafting is primarily for contained cavitary defects. While reinforcement cages with bulk allografts were historically used, they are associated with high non-union and infection rates. Custom triflange components are an option for very severe, irregular defects, but modern highly porous uncemented cups with adjunctive augments (trabecular metal or equivalent) and supplemental screws offer a robust and more frequently utilized solution. These augments restore bone stock and provide stable fixation, allowing for biologic ingrowth. The highly porous design maximizes surface area for integration and provides immediate stability even with compromised host bone. For Type IIIB, the combination of a highly porous cup and structural augments addresses both fixation and bone loss effectively.

Question 4446

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old patient with a well-fixed, cemented THA develops chronic groin pain, fatigue, and occasional low-grade fever two years post-surgery. A hip aspiration is performed, and multiple cultures consistently grow Cutibacterium acnes (formerly Propionibacterium acnes). Inflammatory markers (ESR, CRP) are mildly elevated. What is the most appropriate management strategy for this periprosthetic joint infection (PJI) based on the organism and presentation?

. Lifelong suppressive oral antibiotics without surgical intervention
. Debridement, antibiotics, and implant retention (DAIR) with prolonged, culture-specific antibiotics
. One-stage revision arthroplasty with cement containing antibiotics
. Two-stage revision arthroplasty, with explantation followed by delayed reimplantation
. Explantation of components without reimplantation (Girdlestone arthroplasty)

Correct Answer & Explanation

. Debridement, antibiotics, and implant retention (DAIR) with prolonged, culture-specific antibiotics

Explanation

Cutibacterium acnesis a low-virulence organism often associated with delayed-onset PJI. In cases of well-fixed components and a relatively acute presentation of chronic infection, DAIR (Debridement, Antibiotics, and Implant Retention) is a viable option, especially for low-virulence organisms. The key is thorough debridement, capsulectomy, exchange of modular components (femoral head and polyethylene liner), and prolonged (typically 3-6 months) organism-specific intravenous and then oral antibiotics. Two-stage revision is generally reserved for high-virulence infections or failed DAIR. One-stage revision might be considered but DAIR is often preferred for low-virulence organisms in well-fixed components to minimize surgical morbidity. Lifelong suppression is typically for patients who cannot undergo surgery, and explantation without reimplantation is a salvage procedure.

Question 4447

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old male with a 10-year-old uncemented THA sustains a fall, resulting in a periprosthetic femoral fracture. Radiographs show a Vancouver Type B3 fracture, characterized by a fracture around or distal to a loose femoral stem, with significant proximal femoral bone loss. What is the most appropriate surgical management for this fracture?

. Open reduction and internal fixation (ORIF) with plates and cerclage wires/cables
. Exchange of the femoral stem for a cemented short-stem prosthesis
. Revision to a long, extensively coated uncemented femoral stem, bypassing the fracture by at least two cortical diameters
. Girdlestone resection arthroplasty
. Removal of the femoral stem, leaving the fracture to heal spontaneously, followed by rehabilitation

Correct Answer & Explanation

. Revision to a long, extensively coated uncemented femoral stem, bypassing the fracture by at least two cortical diameters

Explanation

Vancouver Type B3 fractures imply a loose stem and compromised proximal femoral bone stock. ORIF with plates and wires/cables (Option A) is typically indicated for stable stems (Type B1). A short-stem prosthesis (Option B) would not provide adequate bypass of the fracture or stability given the bone loss. Girdlestone arthroplasty (Option D) is a salvage procedure for severe infection or medical comorbidities precluding reconstruction. The most appropriate treatment for a Vancouver B3 fracture is revision of the femoral component. This requires a long, extensively porous-coated or cemented stem (depending on surgeon preference and bone quality) that bypasses the fracture by at least two cortical diameters (typically 5-10 cm) to ensure stable fixation in healthy bone. Cerclage wires or cables are often used adjunctively to stabilize the fracture fragments to the new stem.

Question 4448

Topic: Total Hip Arthroplasty (THA)
A 60-year-old patient with rheumatoid arthritis presents with severe bilateral protrusio acetabuli, graded as Paprosky Type IIIA defects, with significant loss of the medial wall. Which of the following reconstructive strategies is most appropriate for the acetabulum?
. Standard uncemented hemispheric cup placed more medially to gain coverage
. Placement of a small-diameter cemented cup within the protruded region without bone graft
. Resection of the protruded bone to achieve a flush fit for a standard cup
. Medialization of the cup combined with a structural autograft or allograft and reinforcement plate/cage
. A custom triflange acetabular component

Correct Answer & Explanation

. Medialization of the cup combined with a structural autograft or allograft and reinforcement plate/cage

Explanation

Protrusio acetabuli involves medial displacement of the femoral head and acetabulum. For severe protrusio (Paprosky IIIA), characterized by significant medial wall bone loss, merely placing a standard cup or resecting bone will not adequately restore hip mechanics or provide durable fixation. A small cemented cup without grafting is insufficient for significant bone loss. The ideal approach often involves restoring the medial wall with a structural bone graft (autograft or allograft) to support the acetabular component, followed by medialization of the cup into a more anatomical position and often supported by an anti-protrusio cage or reinforcement plate to prevent further medial migration and achieve stability. Custom triflange implants (Option E) are typically reserved for much more complex and irregular defects than a Paprosky IIIA protrusio, though they could technically address it, they are often an overkill and more expensive option for this scenario. Medializing the cup into the true hip center with graft support is the reconstructive principle.

Question 4449

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female, 3 years post-THA with a cobalt-chromium femoral head and titanium acetabular shell, develops a chronic, diffuse eczematous rash and persistent, non-infectious hip pain. Patch testing reveals a significant hypersensitivity reaction to cobalt and chromium. All other work-up for infection and loosening is negative. What is the most appropriate next step in management?

. Prescribe oral antihistamines and topical corticosteroids for the rash
. Perform a diagnostic aspiration to rule out a delayed infection
. Revision arthroplasty, exchanging the cobalt-chromium components for titanium/ceramic bearing surfaces
. Continue with conservative management, including physical therapy and pain medication
. Obtain a bone scan to evaluate for occult loosening

Correct Answer & Explanation

. Revision arthroplasty, exchanging the cobalt-chromium components for titanium/ceramic bearing surfaces

Explanation

Given the positive patch tests for cobalt and chromium, and the clinical symptoms of dermatitis and persistent non-infectious hip pain, metal hypersensitivity is the most likely diagnosis. While conservative measures (A, D) might alleviate some symptoms temporarily, they do not address the underlying issue. A diagnostic aspiration (B) would be redundant if prior workup for infection was negative and symptoms are consistent with hypersensitivity. A bone scan (E) is generally not specific enough to diagnose hypersensitivity and typically looks for loosening or infection, which have already been ruled out. The definitive treatment for symptomatic metal hypersensitivity, when conservative measures fail, is revision arthroplasty to remove the offending metal components and replace them with hypoallergenic materials such as titanium or ceramic bearing surfaces.

Question 4450

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old male with a history of Parkinson's disease and two prior dislocations after a primary total hip arthroplasty (THA) is scheduled for revision surgery. The surgeon plans to use a dual mobility acetabular component. What is the primary biomechanical advantage offered by a dual mobility component in preventing recurrent dislocation?

. Increased contact area to reduce polyethylene wear
. Ability to use a smaller femoral head for easier reduction
. Significant increase in the 'jump distance' required for dislocation
. Enhanced biological fixation to host bone due to porous coating
. Increased tension in the surrounding soft tissues

Correct Answer & Explanation

. Significant increase in the 'jump distance' required for dislocation

Explanation

Dual mobility components incorporate two articulations: a small diameter femoral head articulates within a mobile polyethylene liner, which then articulates with a larger metal acetabular shell. This design significantly increases the 'jump distance' — the distance the femoral head must travel out of the acetabulum before dislocating. This larger jump distance provides a much greater barrier to dislocation compared to conventional THA, making it particularly beneficial in patients with high risk of instability, such as those with neuromuscular disorders, abductor insufficiency, or a history of recurrent dislocations. While dual mobility can be porous-coated (D) and may eventually reduce wear over long terms by larger articulation (A), the primary and immediate mechanical advantage for instability is the increased jump distance. It does not inherently increase soft tissue tension (E), and a smaller femoral head alone (B) would increase dislocation risk in conventional THA.

Question 4451

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female, one year after a total hip arthroplasty (THA) with a greater trochanteric osteotomy (GTO) for severe hip dysplasia, presents with persistent Trendelenburg gait, lateral hip pain, and weakness of hip abduction. Radiographs show a clear fibrous non-union of the osteotomized greater trochanter. What is the most appropriate management strategy?

. Prolonged non-weight bearing and observation
. Intensified physical therapy focusing on abductor strengthening
. Revision internal fixation of the greater trochanter with bone grafting and cables/wires
. Exploration and removal of hardware, followed by soft tissue release
. Conversion to a constrained acetabular component to compensate for abductor weakness

Correct Answer & Explanation

. Revision internal fixation of the greater trochanter with bone grafting and cables/wires

Explanation

A symptomatic fibrous non-union of a greater trochanteric osteotomy leads to persistent abductor weakness and pain due to the lack of a stable lever arm for the abductor muscles. Prolonged non-weight bearing (A) or physical therapy alone (B) will not address a structural non-union. Hardware removal (D) would further destabilize the trochanter. While a constrained acetabular component (E) might help with stability, it does not address the abductor deficiency or pain from the non-union. The most appropriate management is surgical repair. This typically involves revision internal fixation (e.g., using cables, screws, or plates) to achieve compression and stability, often augmented with bone graft to promote osteotomy union. This aims to restore the continuity of the abductor mechanism and improve function.

Question 4452

Topic: 3. Adult Reconstruction (Hip & Knee)

During a direct anterior approach for total hip arthroplasty, after placing the retractors, the surgeon notes a sudden, brisk, pulsatile hemorrhage deep and medial to the rectus femoris and lateral to the psoas. What is the most likely injured vessel?

. Deep femoral artery
. Superficial femoral artery
. Lateral circumflex femoral artery
. External iliac artery
. Obturator artery

Correct Answer & Explanation

. External iliac artery

Explanation

In the direct anterior approach, the surgical interval is between the tensor fascia lata (superior gluteal nerve) and the sartorius/rectus femoris (femoral nerve). The femoral neurovascular bundle lies medial to the rectus femoris. Retraction of the rectus femoris and psoas medially can place the external iliac artery (which becomes the common femoral artery distal to the inguinal ligament) at risk, particularly with medial retractors or during acetabular reaming. The deep femoral artery and superficial femoral artery are more distal branches. The lateral circumflex femoral artery is a branch of the deep femoral, typically seen more laterally. The obturator artery is deep within the pelvis and less likely to be injured during standard anterior approach exposure unless there is significant medial breach of the acetabulum. Therefore, the external iliac artery (or its immediate continuation, the common femoral artery) is the most vulnerable vessel in this position.

Question 4453

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male presents with persistent pain, instability, and recurrent drainage from his hip, 5 years after undergoing a Girdlestone resection arthroplasty for a previous infected THA. He is medically fit for further surgery and desires improved function. What is the most appropriate definitive surgical management to attempt a functional reconstruction?

. Lifelong suppressive antibiotics and a custom brace
. Repeat Girdlestone resection arthroplasty to debride chronically infected tissues
. Hip fusion (arthrodesis) to stabilize the joint
. Staged reimplantation with a proximal femoral allograft-prosthesis composite
. Single-stage revision with a constrained acetabular component and a standard uncemented stem

Correct Answer & Explanation

. Staged reimplantation with a proximal femoral allograft-prosthesis composite

Explanation

A Girdlestone arthroplasty is a salvage procedure that results in a flail, painful, and often unstable hip with significant limb shortening and severe bone loss, particularly in the proximal femur. While lifelong antibiotics (A) may suppress infection, they do not address the functional deficit. A repeat Girdlestone (B) provides no functional improvement. Hip fusion (C) is a possibility, but given modern reconstructive options, a Girdlestone is often an intermediate step for a planned staged reimplantation. For a patient who desires improved function and is medically fit, a staged reimplantation with a proximal femoral allograft-prosthesis composite (APC) is often the preferred and most effective option. This involves radical debridement, antibiotic treatment, and then at a later stage, reconstruction using a large structural allograft combined with prosthetic components to restore bone stock, length, and stability. Single-stage revision (E) with a standard stem is generally not feasible due to the massive bone loss following Girdlestone.

Question 4454

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old patient with a long history of poorly controlled diabetes presents with rapidly progressive, painless destruction of the right hip joint, significant instability, and profound bone loss evident on radiographs, consistent with a Charcot arthropathy. He is otherwise medically optimized for surgery. What is the most appropriate surgical management for end-stage neuropathic arthropathy of the hip?

. Conservative management with a long-leg brace and non-weight bearing
. Total hip arthrodesis (fusion) to provide stability
. Girdlestone resection arthroplasty to remove the source of pain and infection
. Constrained total hip arthroplasty with cementation
. Standard uncemented total hip arthroplasty with bone grafting

Correct Answer & Explanation

. Constrained total hip arthroplasty with cementation

Explanation

End-stage Charcot arthropathy of the hip is characterized by severe joint destruction, significant bone loss, and profound instability. Standard uncemented or even cemented THA (E) often fails due to the poor bone quality, fragmentation, and persistent instability. Arthrodesis (B) is technically very challenging in the presence of severe bone loss and may not be feasible. Girdlestone (C) is a salvage procedure, but in a medically fit patient with severe instability and bone loss, it may be indicated when other options are not viable. However, the most appropriatereconstructiveoption to restore function and stability is often a constrained total hip arthroplasty (D). Constrained liners provide mechanical stability, compensating for the severe capsular and bone destruction and chronic instability inherent in Charcot joints, reducing the risk of dislocation. Cementation is often preferred due to compromised bone stock. Conservative management (A) is rarely effective for end-stage disease.

Question 4455

Topic: 3. Adult Reconstruction (Hip & Knee)

A 35-year-old active male requires a total hip arthroplasty for post-traumatic arthritis. He has high activity demands and a long life expectancy. He values longevity and minimizing the risk of revision. Which bearing surface combination is generally considered most appropriate for this patient, offering the lowest wear rates and optimal longevity?

. Metal-on-polyethylene (MoP)
. Ceramic-on-polyethylene (CoP) with highly cross-linked polyethylene
. Metal-on-metal (MoM)
. Ceramic-on-ceramic (CoC)
. Polyethylene-on-polyethylene (PoP)

Correct Answer & Explanation

. Ceramic-on-ceramic (CoC)

Explanation

For young, active patients with long life expectancies, minimizing wear and maximizing longevity are paramount. Metal-on-polyethylene (A) has historically high wear rates and osteolysis risk. Metal-on-metal (C) was once considered for young patients due to low wear, but concerns about metal ion release, pseudotumors, and hypersensitivity have largely led to its abandonment. Polyethylene-on-polyethylene (E) is not a standard bearing. Ceramic-on-polyethylene with highly cross-linked polyethylene (B) offers excellent wear characteristics, but ceramic-on-ceramic (D) currently boasts the lowest reported in vivo wear rates, making it a very attractive option for young, active patients, despite potential risks like squeaking or ceramic fracture (which are increasingly rare with modern ceramics). The decision often weighs CoC's lowest wear against the slightly higher fracture risk and noise, versus CoP with highly cross-linked poly which also has excellent wear and negligible fracture risk.

Question 4456

Topic: 3. Adult Reconstruction (Hip & Knee)

A 40-year-old male sustained a displaced femoral neck fracture, which was treated with cannulated screws. One year post-op, he develops persistent groin pain and radiographic evidence of femoral head collapse and avascular necrosis (AVN). He has no signs of infection. What is the most appropriate definitive surgical intervention for this active patient?

. Repeat internal fixation with a dynamic hip screw
. Hemiarthroplasty (femoral head replacement)
. Total hip arthroplasty (THA)
. Girdlestone resection arthroplasty
. Core decompression and bone grafting

Correct Answer & Explanation

. Total hip arthroplasty (THA)

Explanation

For a 40-year-old active male with painful femoral head collapse due to avascular necrosis after failed femoral neck fracture fixation, the femoral head is no longer viable. Repeat internal fixation (A) or core decompression (E) would be ineffective as the head is already necrotic and collapsed. Hemiarthroplasty (B) is generally considered less ideal for active younger patients due to the risk of acetabular cartilage erosion and the potential need for revision to THA in the future. Given his age and activity level, a total hip arthroplasty (C) is the most appropriate definitive intervention, as it replaces both the femoral head and the acetabular socket, providing durable pain relief and restoration of function. Girdlestone (D) is a salvage procedure and not suitable for this patient.

Question 4457

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with groin pain and hip instability 12 years after a primary THA. Radiographs show a well-fixed femoral stem but extensive periacetabular osteolysis and a large contained Paprosky Type IIB acetabular defect caused by polyethylene wear, with the acetabular component still in place. There are no signs of infection. What is the most appropriate management strategy for the acetabulum?

. Liner exchange only
. Observation with serial radiographs and conservative management
. Revision of the acetabular component with bone grafting for the defect and a new liner
. Revision of both the acetabular and femoral components
. Explantation and Girdlestone arthroplasty

Correct Answer & Explanation

. Revision of the acetabular component with bone grafting for the defect and a new liner

Explanation

Extensive periacetabular osteolysis with a Paprosky Type IIB defect indicates significant bone loss that compromises the stability and integrity of the acetabular component. A liner exchange only (A) would address the wear source but would not treat the underlying osteolysis or restore the bone defect, leading to continued progression and potential catastrophic failure. Observation (B) is inappropriate for progressive osteolysis. Revision of both components (D) is unnecessary if the femoral component is well-fixed. Explantation (E) is a salvage procedure. The most appropriate management is revision of the acetabular component (C). This involves removing the old acetabular shell, debriding the osteolytic lesions, grafting the bone defect (often with morselized allograft), and implanting a new acetabular component, typically an uncemented porous-coated shell, to allow for bone ingrowth and long-term stability.

Question 4458

Topic: Total Hip Arthroplasty (THA)

During a primary total hip arthroplasty via a posterior approach, the patient is noted to have a preoperative leg length discrepancy of 2.5 cm, with the operative leg being shorter. The surgeon plans to restore leg length to within 5 mm of the contralateral side. What is a crucial intraoperative maneuver or consideration to minimize the risk of sciatic nerve injury during this limb lengthening?

. Performing a staged lengthening over several weeks with an external fixator
. Intraoperative neuromonitoring (e.g., somatosensory evoked potentials or electromyography)
. Positioning the hip in extreme external rotation during reduction
. Administering a bolus of intravenous steroids immediately prior to lengthening
. Avoiding any soft tissue releases around the hip capsule

Correct Answer & Explanation

. Intraoperative neuromonitoring (e.g., somatosensory evoked potentials or electromyography)

Explanation

Restoring significant leg length discrepancy (e.g., >2-3 cm) during THA carries a notable risk of sciatic nerve palsy due to excessive tension. While a femoral shortening osteotomy (not an option here) is a definitive way to prevent excessive lengthening, in this scenario, options to mitigate risk are crucial. Intraoperative neuromonitoring (B) is a critical tool to detect impending nerve compromise. It provides real-time feedback on nerve function, allowing the surgeon to adjust lengthening or perform additional soft tissue releases if nerve signals diminish. Staged lengthening (A) is for very extreme cases or where nerve function cannot be monitored or salvaged. Extreme external rotation (C) may temporarily reduce tension but is not a primary protective maneuver. Steroids (D) are not proven prophylactic. Avoiding soft tissue releases (E) increases nerve tension. Therefore, neuromonitoring is key for safe lengthening.

Question 4459

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient undergoes revision THA through a direct lateral approach. Postoperatively, they develop severe abductor weakness, and radiographs reveal a complete detachment of the greater trochanter, including the reattached abductor muscles. What is the most appropriate management for this acute complete trochanteric detachment?

. Observation, strict non-weight bearing, and hip abduction bracing
. Intensified physical therapy to strengthen accessory abductors
. Immediate surgical repair with wires or cables and possibly a revision of the abductor attachment
. Referral for chronic pain management, as surgical repair is rarely successful
. Conversion to a Girdlestone arthroplasty to remove painful hardware

Correct Answer & Explanation

. Immediate surgical repair with wires or cables and possibly a revision of the abductor attachment

Explanation

A complete detachment of the greater trochanter with the abductors, especially in the acute setting, is a severe complication that results in significant abductor insufficiency, Trendelenburg gait, and often pain. This requires operative management. Observation (A) or physical therapy alone (B) will not allow the bony fragment to heal or restore abductor function. Surgical repair (C) is the most appropriate management. This typically involves re-attaching the greater trochanter to the proximal femur using strong internal fixation, such as cerclage wires, cables, or plates, often with an emphasis on recreating a stable tension band. Early and stable repair is crucial for functional recovery. Referral for chronic pain (D) would be premature, and Girdlestone (E) is a salvage procedure for profound failure, not an acute traumatic detachment amenable to repair.

Question 4460

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old female experiences persistent, non-specific pain in the buttock and posterior thigh 6 months after an uncomplicated primary THA performed via a posterior approach. Radiographs are normal, inflammatory markers (ESR, CRP) are within normal limits, and a nuclear medicine scan shows no evidence of loosening or infection. Physical examination reveals tenderness over the piriformis muscle and pain with resisted external rotation and abduction. What is the most likely diagnosis?

. Aseptic loosening of the femoral component
. Low-grade periprosthetic joint infection (PJI)
. Piriformis syndrome
. Osteolysis secondary to polyethylene wear
. Iliopsoas impingement

Correct Answer & Explanation

. Piriformis syndrome

Explanation

Given the normal radiographs, inflammatory markers, and nuclear medicine scan, aseptic loosening (A), PJI (B - though a low-grade infection cannot be entirely ruled out without aspiration, the exam points elsewhere), and osteolysis (D) are less likely. Iliopsoas impingement (E) typically presents as anterior groin pain, often worse with hip flexion. The symptoms of buttock and posterior thigh pain, tenderness over the piriformis, and pain with resisted external rotation and abduction, particularly after a posterior approach (which can involve manipulation of the piriformis), are highly suggestive of piriformis syndrome (C). This is a common cause of persistent pain after THA, related to irritation or inflammation of the piriformis muscle or sciatic nerve entrapment by the muscle, and is a non-arthroplasty-related issue.

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