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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 15 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 281

Topic: Total Hip Arthroplasty (THA)

A 28-year-old male presents with a terrible triad injury. During the surgical approach, the surgeon utilizes the 'utility posterior approach' as described in the case. Which of the following anatomical structures is typically incised or elevated to gain access to the radial head and coronoid fractures via this approach?

. A. The common flexor origin from the medial epicondyle.
. B. The triceps tendon, which is then reflected distally.
. C. The anconeus muscle, which is elevated off the ulna.
. D. The anterior bundle of the medial collateral ligament.
. E. The brachialis muscle, which is split longitudinally.

Correct Answer & Explanation

. C. The anconeus muscle, which is elevated off the ulna.

Explanation

Correct Answer: CThe utility posterior approach, often referred to as the Kocher approach or a modification thereof, involves an incision centered over the lateral epicondyle. To access the radial head and coronoid (which is anterior), the interval between the anconeus and extensor carpi ulnaris (ECU) is typically utilized. The anconeus muscle is elevated off the ulna, and the lateral collateral ligament complex is identified and often repaired. This provides access to the radial head and, by flexing the elbow and pronating the forearm, allows visualization of the coronoid.Option A (The common flexor origin from the medial epicondyle)is incorrect. This is on the medial side and is not part of the utility posterior (lateral) approach.Option B (The triceps tendon, which is then reflected distally)is incorrect. While the triceps is posterior, reflecting it distally is part of a direct posterior approach, not typically the utility posterior approach which focuses on the lateral side for terrible triads.Option D (The anterior bundle of the medial collateral ligament)is incorrect. This is a medial structure and is not incised or elevated during a lateral-based utility posterior approach.Option E (The brachialis muscle, which is split longitudinally)is incorrect. The brachialis muscle is anterior to the elbow joint. Splitting it is part of an anterior approach, not a utility posterior approach.

Question 282

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male sustains a periprosthetic femur fracture around a total hip arthroplasty stem. The surgeon opts for plate and screw fixation. The use of locking screws in this context primarily enhances stability by:

. A. Increasing the frictional resistance between the screw head and the plate.
. B. Creating a monobloc effect between the screw, plate, and bone.
. C. Allowing for dynamic compression at the fracture site.
. D. Reducing the overall stiffness of the construct.
. E. Facilitating easier removal of bone debris during insertion.

Correct Answer & Explanation

. B. Creating a monobloc effect between the screw, plate, and bone.

Explanation

Correct Answer: BThe case states, 'The use of a locking screw can also create a monobloc effect for greater stability.' Locking screws thread into the plate, creating a fixed-angle construct that acts as a single unit (monobloc) with the bone, providing enhanced stability, especially in osteoporotic bone or comminuted fractures. They do not primarily rely on screw-plate friction (A) or provide dynamic compression (C) in the same way non-locking screws do. They increase, rather than reduce, the stiffness of the construct (D). Flutes, not locking screws, facilitate bone debris removal (E).

Question 283

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old poorly controlled diabetic patient presents with a severely swollen, erythematous, but painless midfoot. Radiographs show extensive joint destruction, bone fragmentation, and subluxation. What is the primary underlying pathogenesis of this destructive joint disease?

. Direct hematogenous bacterial seeding
. Peripheral neuropathy leading to repetitive unperceived microtrauma
. Autoimmune destruction of the synovial lining
. Uric acid crystal deposition in the joint space
. Primary avascular necrosis of the navicular bone

Correct Answer & Explanation

. Peripheral neuropathy leading to repetitive unperceived microtrauma

Explanation

The presentation is classic for Charcot neuroarthropathy. The neurotraumatic theory posits that profound peripheral neuropathy leads to a loss of protective sensation, allowing repetitive microtrauma to cause progressive joint destruction.

Question 284

Topic: 3. Adult Reconstruction (Hip & Knee)

A 30-year-old patient undergoes surgical stabilization for a Rockwood Type V AC joint injury. Six months postoperatively, he presents with persistent pain localized to the distal clavicle, particularly with overhead activities. Radiographs show lucency and erosion at the distal clavicle. Based on the case, what is the most likely complication and its appropriate management?

. Coracoid fracture; requiring revision surgery with alternative fixation points.
. Loss of reduction; requiring revision to a robust biologic reconstruction.
. Distal clavicle osteolysis; managed by arthroscopic or open distal clavicle excision once CC ligaments have healed.
. Adhesive capsulitis; managed with aggressive physical therapy and corticosteroid injections.
. Infection; requiring aggressive irrigation and debridement with antibiotics.

Correct Answer & Explanation

. Distal clavicle osteolysis; managed by arthroscopic or open distal clavicle excision once CC ligaments have healed.

Explanation

Correct Answer: CThe patient's symptoms of persistent pain localized to the distal clavicle with lucency and erosion on radiographs six months postoperatively are classic signs of distal clavicle osteolysis. The 'Complications and Management' table in the case describes 'Distal Clavicle Osteolysis' with an etiology of 'Micro-motion, rigid fixation (hook plates), or unrecognized intra-articular damage.' The recommended salvage strategy is 'Arthroscopic or open distal clavicle excision (Mumford procedure) once the coracoclavicular ligaments have fully healed.' The other options describe different complications with distinct presentations and management strategies.

Question 285

Topic: 3. Adult Reconstruction (Hip & Knee)
A 40-year-old male with a history of a displaced femoral neck fracture treated with internal fixation 18 months ago presents with chronic, worsening hip pain. Radiographs show flattening and sclerosis of the femoral head with a subchondral crescent sign. The fracture appears united. What is the most likely complication, and what is the definitive treatment for this stage?
. Nonunion; revision internal fixation with bone grafting.
. Malunion; corrective intertrochanteric osteotomy.
. Avascular necrosis (AVN) with collapse; total hip arthroplasty (THA).
. Hardware-related pain; hardware removal.
. Infection; irrigation and debridement with antibiotics.

Correct Answer & Explanation

. Avascular necrosis (AVN) with collapse; total hip arthroplasty (THA).

Explanation

Correct Answer: C. The clinical presentation of chronic, worsening hip pain 18 months post-fixation, coupled with radiographic findings of flattening and sclerosis of the femoral head with a subchondral crescent sign, is highly indicative of advanced avascular necrosis (AVN) with femoral head collapse. For late, post-collapse (Ficat Stage III/IV) AVN, the definitive treatment is total hip arthroplasty (THA). Option A is incorrect: The question states the fracture appears united, ruling out nonunion. Revision internal fixation is for nonunion, not established AVN with collapse. Option B is incorrect: Malunion would involve a healed fracture in a deformed position, leading to pain and altered biomechanics, but not typically the specific radiographic signs of AVN with collapse. A corrective osteotomy is for symptomatic malunion. Option D is incorrect: While hardware removal is considered for symptomatic hardware after union, the described radiographic changes (flattening, sclerosis, crescent sign) point to a more severe underlying pathology (AVN) than just hardware irritation. Option E is incorrect: There are no signs of infection (fever, erythema, drainage, elevated inflammatory markers) mentioned in the vignette.

Question 286

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old male with a displaced femoral neck fracture is being prepared for surgery. The surgical team is discussing the management of the joint capsule. Based on the case, what is the current understanding regarding the role of capsulotomy in preventing avascular necrosis (AVN)?

. Capsulotomy is definitively proven to reduce the rate of AVN by decompressing the intracapsular hematoma and improving blood flow.
. Capsulotomy is contraindicated as it can further disrupt the retinacular vessels and increase the risk of AVN.
. The decision to close or leave the capsule open is debated, and current evidence does not conclusively support one approach over the other for independently reducing AVN.
. Capsulotomy is only performed if an open reduction is required, primarily to visualize the fracture, not for AVN prevention.
. Leaving the capsule open is universally recommended to facilitate drainage and prevent tamponade effect, thereby reducing AVN.

Correct Answer & Explanation

. The decision to close or leave the capsule open is debated, and current evidence does not conclusively support one approach over the other for independently reducing AVN.

Explanation

Correct Answer: CThe 'Capsular Management' section states: 'After open reduction and fixation, the decision to close the capsule is debated... Current evidence does not definitively support one approach over the other for preventing AVN.' The 'Summary of Key Literature / Guidelines' further reinforces this: 'The practice of capsulotomy to decompress the intracapsular hematoma and potentially improve femoral head perfusion has been debated. While some studies suggest a benefit, current evidence is not conclusive that it independently reduces the rate of AVN.'Option A is incorrect:The case explicitly states that evidence is not conclusive regarding its independent role in reducing AVN.Option B is incorrect:Capsulotomy is often performed, especially in open reduction, and is not generally considered contraindicated. The concern is about further vascular disruption, but the anterior approach aims to protect vessels.Option D is incorrect:While capsulotomy is essential for visualization in open reduction, the debate specifically addresses its role in decompressing the hematoma to improve vascularity, which is directly related to AVN prevention.Option E is incorrect:While some advocate leaving the capsule open for decompression, the case clearly states that this is a debated topic and not universally recommended, as conclusive evidence is lacking.

Question 287

Topic: Total Hip Arthroplasty (THA)
A 68-year-old male presents with a two-year history of worsening left hip pain, progressive instability, and a 3.5 cm leg length discrepancy following a revision THA 5 years prior. Clinical examination reveals a profound Trendelenburg gait, severely restricted range of motion, and an audible/palpable mechanical clunk. Preoperative radiographs demonstrate catastrophic failure of the left acetabular construct with significant superior and medial migration, violation of Kohler's line, and extensive periacetabular osteolysis. The previously placed bulk femoral head allograft shows signs of advanced resorption and structural collapse. Based on these findings, which of the following is the most appropriate initial classification of the acetabular defect, prior to advanced imaging?
. Paprosky Type I
. Paprosky Type IIA
. Paprosky Type IIB
. Paprosky Type IIC
. Paprosky Type IIIB

Correct Answer & Explanation

. Paprosky Type IIIB

Explanation

Correct Answer: E. The AP pelvis radiograph clearly demonstrates significant superior migration of the acetabular component exceeding 3 cm, violation of Kohler's line (indicating medial wall deficiency), and extensive periacetabular osteolysis in all three DeLee and Charnley zones. The superior dome is entirely deficient, and the previously placed bulk allograft has failed. These findings are characteristic of a Paprosky Type IIIB defect, which involves severe bone loss with a non-supportive rim and significant column compromise, specifically superior bone loss greater than 3 cm, severe destruction of the teardrop, Kohler's line, and both columns. Paprosky Type I defects have minimal bone loss and an intact rim. Type IIA involves superior bone loss but intact columns. Type IIB involves superior and lateral bone loss. Type IIC involves a medial wall defect. None of these adequately describe the catastrophic bone loss and superior migration seen in the image and described in the vignette.

Question 288

Topic: 3. Adult Reconstruction (Hip & Knee)

Following the initial AP pelvis radiograph, Judet oblique views were obtained. The obturator oblique view revealed near-complete destruction of the anterior column and quadrilateral plate, while the iliac oblique view demonstrated severe posterior column osteolysis extending into the ischium. These findings, combined with the AP view, raised a high suspicion for pelvic discontinuity, as shown in the image below.

Which of the following statements best describes the biomechanical significance of a complete pelvic discontinuity in the context of acetabular revision surgery?

. It primarily indicates a deficiency of the superior dome, requiring only a jumbo hemispherical cup.
. It signifies a transverse fracture separating the superior and inferior hemipelves, leading to mechanical uncoupling and instability.
. It suggests isolated medial wall erosion, which can be managed with impaction bone grafting alone.
. It is a contraindication to any form of acetabular reconstruction, necessitating Girdlestone arthroplasty.
. It implies a contained cavitary defect that can be addressed with a standard cementless cup and screws.

Correct Answer & Explanation

. It signifies a transverse fracture separating the superior and inferior hemipelves, leading to mechanical uncoupling and instability.

Explanation

Correct Answer: BA complete pelvic discontinuity is defined as a transverse fracture through the acetabulum that separates the superior hemipelvis (ilium) from the inferior hemipelvis (ischium and pubis). This mechanical uncoupling leads to gross instability of the acetabulum, where the two halves of the pelvis move independently. This instability prevents biological ingrowth into a standard cementless cup and requires a reconstructive strategy that can mechanically bridge and stabilize this fracture, such as a reconstruction cage or a custom triflange component, to allow for fracture healing and provide a stable foundation for the acetabular component.Option A is incorrect because while superior dome deficiency often coexists, pelvic discontinuity is a distinct structural fracture, not just a bone loss pattern. A jumbo hemispherical cup alone cannot stabilize a discontinuity. Option C is incorrect; medial wall erosion is a component of severe defects, but discontinuity is a much more severe structural issue requiring robust mechanical bridging. Impaction bone grafting alone is insufficient for discontinuity. Option D is incorrect; while challenging, pelvic discontinuity is a well-recognized indication for advanced revision techniques like cup-cage constructs, not an absolute contraindication to reconstruction. Option E is incorrect; a contained cavitary defect is a Paprosky Type II defect, whereas discontinuity represents a much more severe, uncontained structural failure that cannot be managed with a standard cementless cup and screws alone.

Question 289

Topic: 3. Adult Reconstruction (Hip & Knee)
A high-resolution Computed Tomography (CT) scan of the pelvis with Metal Artifact Reduction Sequence (MARS) was obtained to precisely quantify volumetric bone loss and definitively diagnose pelvic discontinuity. The multi-planar reformatted images confirmed a massive Paprosky Type IIIB acetabular defect with complete absence of the superior dome, medial wall, and significant portions of both the anterior and posterior columns. Crucially, the axial and coronal cuts confirmed a frank pelvic discontinuity. Given the confirmed Paprosky Type IIIB defect with pelvic discontinuity, which of the following reconstructive strategies is biomechanically most appropriate for this patient?
. Impaction bone grafting with a standard cementless hemispherical cup.
. A large diameter cementless cup with multiple screws into the remaining host bone.
. A custom triflange acetabular component (CTAC).
. A cup-cage reconstruction utilizing a trabecular metal cup and an ilioischial reconstruction ring.
. A Girdlestone resection arthroplasty.

Correct Answer & Explanation

. A cup-cage reconstruction utilizing a trabecular metal cup and an ilioischial reconstruction ring.

Explanation

Correct Answer: D. For a Paprosky Type IIIB defect with an associated pelvic discontinuity, the cup-cage reconstruction is a highly effective and commonly utilized strategy. The trabecular metal cup provides a porous surface for biological ingrowth into the remaining host bone, while the ilioischial reconstruction ring (cage) mechanically bridges the pelvic discontinuity, providing immediate rigid stability by fixing to the intact bone of the ilium superiorly and the ischium inferiorly. This construct neutralizes shear forces across the discontinuity, allowing for fracture healing and protecting the biological ingrowth of the cup. Option A (Impaction bone grafting with a standard cementless cup) has a high failure rate in the presence of discontinuity due to a lack of initial mechanical stability. Option B (Large diameter cementless cup with multiple screws) is insufficient to stabilize a pelvic discontinuity, as the underlying bone is uncoupled. Option C (Custom triflange acetabular component) is a viable option for this defect, offering excellent stability. However, the question asks for the most appropriate given the context, and CTACs require extensive preoperative manufacturing time, are highly expensive, and offer limited intraoperative flexibility, making the cup-cage a more readily available and flexible solution that achieves similar biomechanical goals. Option E (Girdlestone resection arthroplasty) is a salvage procedure typically reserved for intractable infection or failed reconstructions where further attempts are deemed futile.

Question 290

Topic: 3. Adult Reconstruction (Hip & Knee)
Preoperative laboratory diagnostics were obtained to definitively rule out subacute periprosthetic joint infection (PJI) prior to undertaking a massive reconstructive procedure. The Erythrocyte Sedimentation Rate (ESR) was 12 mm/hr (normal <20 mm/hr), and the C-Reactive Protein (CRP) was 0.4 mg/dL (normal <1.0 mg/dL). Given these normal inflammatory markers and the classic radiographic appearance of aseptic mechanical failure, preoperative joint aspiration was deemed unnecessary. In a patient presenting with a painful THA, which combination of synovial fluid findings would most strongly suggest a periprosthetic joint infection (PJI) according to current diagnostic criteria?
. Synovial fluid WBC count < 1,000 cells/ยตL and < 50% PMNs.
. Synovial fluid WBC count > 3,000 cells/ยตL and > 70% PMNs.
. Synovial fluid WBC count > 10,000 cells/ยตL and < 60% PMNs.
. Synovial fluid WBC count < 2,000 cells/ยตL and > 80% PMNs.
. Synovial fluid WBC count between 1,000-3,000 cells/ยตL and 50-70% PMNs.

Correct Answer & Explanation

. Synovial fluid WBC count > 3,000 cells/ยตL and > 70% PMNs.

Explanation

Correct Answer: B. According to the Musculoskeletal Infection Society (MSIS) criteria and other widely accepted guidelines, a synovial fluid white blood cell (WBC) count greater than 3,000 cells/ยตL and a polymorphonuclear neutrophil (PMN) percentage greater than 70% are highly suggestive of periprosthetic joint infection (PJI). The case specifically mentions these thresholds in its differential diagnosis table for PJI. Option A represents findings typically associated with aseptic loosening. Option C has a high WBC count but a low PMN percentage, which would be atypical for PJI. Option D has a low WBC count despite a high PMN percentage, which would not meet PJI criteria. Option E represents an indeterminate zone, where further investigation (e.g., alpha-defensin, cultures) would be necessary, but it is not the most strongly suggestive combination for PJI.

Question 291

Topic: 3. Adult Reconstruction (Hip & Knee)
During the surgical intervention for this patient's massive Paprosky Type IIIB defect with pelvic discontinuity, an extended posterior approach was utilized. Extensive scar tissue from previous surgeries was encountered. Careful dissection was performed to identify and protect the sciatic nerve, which was found to be encased in dense fibrous tissue and tethered medially due to the superior migration of the acetabular construct. A formal sciatic nerve neurolysis was performed from the greater sciatic notch down to the proximal thigh. What is the primary reason for the sciatic nerve being tethered medially in this specific clinical scenario?
. Direct impingement by the well-fixed femoral stem.
. Compression from a large pseudotumor due to metallosis.
. Superior and medial migration of the acetabular component, pulling the nerve towards the true pelvis.
. Post-surgical scarring from the prior posterolateral approach alone.
. Anatomical variation of the sciatic nerve exiting above the piriformis.

Correct Answer & Explanation

. Superior and medial migration of the acetabular component, pulling the nerve towards the true pelvis.

Explanation

Correct Answer: C. The case explicitly states that the sciatic nerve was found to be encased in dense fibrous tissue and tethered medially due to the superior migration of the acetabular construct. When the acetabular component migrates superiorly and medially into the true pelvis, it effectively shortens the distance between the greater sciatic notch (where the nerve exits) and the medial aspect of the pelvis, thereby pulling and tethering the sciatic nerve medially. This places the nerve at high risk of injury during subsequent revision surgery, necessitating careful neurolysis. Option A is incorrect; the femoral stem was noted to be well-fixed and not implicated in nerve tethering. Option B is incorrect; while metallosis can cause pseudotumors and nerve compression, the case denies ALTR/metallosis as the primary issue and attributes the tethering to component migration. Option D is a contributing factor to scar tissue, but the primary mechanical cause of medial tethering is the component migration. Option E is an anatomical variation but does not explain the acquired medial tethering in the context of a failed THA.

Question 292

Topic: Total Hip Arthroplasty (THA)
During the cup-cage reconstruction, a jumbo, highly porous trabecular metal multi-hole acetabular shell was selected and impacted into the prepared defect. Due to the massive bone loss, host bone contact was estimated at approximately 30-40%, primarily located superiorly against the ilium and inferiorly against the ischium. Multiple locking and non-locking screws were placed through the cup into the superior ilium and the posterior column to achieve initial press-fit stability. Despite the screws, the cup alone did not provide sufficient rigidity to neutralize the pelvic discontinuity, necessitating the cage construct. What is the primary biomechanical role of the highly porous trabecular metal cup in this specific cup-cage construct for a Paprosky IIIB defect with pelvic discontinuity?
. To provide immediate, rigid mechanical fixation across the pelvic discontinuity.
. To serve as a scaffold for biological ingrowth and long-term osseointegration.
. To act as a spacer, filling the void created by the bone defect.
. To provide a smooth articulating surface for the femoral head.
. To prevent medialization of the femoral component into the true pelvis.

Correct Answer & Explanation

. To serve as a scaffold for biological ingrowth and long-term osseointegration.

Explanation

Correct Answer: B. The case explicitly states that the highly porous trabecular metal cup is impacted into the remaining viable host bone, and its high coefficient of friction and osteoconductive properties promote rapid biological ingrowth, eventually providing long-term, durable fixation. This is the primary role of the porous cup: to achieve biological fixation and osseointegration with the host bone. The cage, not the cup, provides the immediate mechanical stability across the discontinuity. Option A is incorrect; the cage provides the immediate rigid mechanical fixation across the discontinuity, protecting the cup. Option C is a secondary effect, but not its primary biomechanical role. Option D is incorrect; the polyethylene liner, cemented into the cage, provides the articulating surface, not the metal cup itself. Option E is a function of the entire construct, but the specific role of the porous cup is biological fixation.

Question 293

Topic: 3. Adult Reconstruction (Hip & Knee)

Following the curing of the cement, a trial reduction was performed using a dual-mobility femoral head on the existing well-fixed femoral stem. The hip was taken through a full range of motion, demonstrating remarkable stability with no impingement or tendency for dislocation. Leg length was assessed and found to be restored to within 5mm of the contralateral side, correcting the preoperative 3.5cm discrepancy. Intraoperative fluoroscopy was utilized to confirm the final component position.

The postoperative AP radiograph above demonstrates excellent restoration of the hip center of rotation, secure fixation of the ilioischial cage bridging the discontinuity, and appropriate seating of the cemented dual-mobility liner. Which of the following radiographic features on this image confirms the successful bridging of the pelvic discontinuity?

. The presence of a dual-mobility articulation.
. The restoration of the hip center of rotation.
. The screws extending from the cage into the ilium and ischium, crossing the fracture line.
. The well-fixed femoral stem without radiolucent lines.
. The absence of a superior dome defect.

Correct Answer & Explanation

. The screws extending from the cage into the ilium and ischium, crossing the fracture line.

Explanation

Correct Answer: CThe primary purpose of the ilioischial reconstruction cage in the setting of pelvic discontinuity is to mechanically bridge the transverse fracture separating the superior and inferior hemipelves. This is achieved by securing the cage with screws into the intact bone of the ilium superiorly and the ischium inferiorly, effectively spanning and stabilizing the discontinuity. On the postoperative radiograph, the visible screws extending from the cage into both the ilium and ischium, crossing the presumed fracture line, are the direct radiographic evidence of this bridging and stabilization.Option A (dual-mobility articulation) is a feature of the bearing surface, not the discontinuity stabilization. Option B (restoration of hip center of rotation) is a goal of the reconstruction but does not specifically confirm bridging of the discontinuity. Option D (well-fixed femoral stem) refers to the femoral side, which was not the primary focus of the acetabular reconstruction. Option E (absence of a superior dome defect) is a result of the reconstruction, but thebridgingof the discontinuity is specifically confirmed by the cage's fixation to both hemipelves.

Question 294

Topic: 3. Adult Reconstruction (Hip & Knee)

Postoperatively, the patient was placed on a strict rehabilitation protocol. For the initial 8 weeks, the patient was restricted to Toe-Touch Weight Bearing (TTWB) or Flat-Foot Weight Bearing (FFWB) on the operative extremity. This restriction was deemed absolutely critical, despite the immediate mechanical stability provided by the cup-cage construct.

What is the primary rationale for strict weight-bearing restrictions during the early postoperative phase (Weeks 0-8) following a cup-cage reconstruction for pelvic discontinuity?

. To prevent dislocation of the dual-mobility articulation.
. To allow for the healing of the posterior soft tissue repair.
. To minimize stress on the femoral stem-bone interface.
. To promote biological bone ingrowth into the trabecular metal cup by preventing micromotion.
. To reduce the risk of deep vein thrombosis (DVT).

Correct Answer & Explanation

. To promote biological bone ingrowth into the trabecular metal cup by preventing micromotion.

Explanation

Correct Answer: DThe case explicitly states: 'The initial stability of the construct relies on the mechanical fixation of the cage. However, long-term success requires biological bone ingrowth into the trabecular metal cup. Excessive early axial loading can cause micromotion, leading to fibrous encapsulation rather than osseointegration.' Therefore, the primary rationale for strict weight-bearing restrictions is to protect the biological fixation of the trabecular metal cup. Micromotion at the bone-implant interface inhibits osteointegration and promotes the formation of a fibrous interface, which can lead to early aseptic loosening.Option A is less critical with a dual-mobility articulation, which significantly mitigates dislocation risk. Option B is a secondary benefit but not the primary reason for such strict weight-bearing restrictions. Option C is incorrect; the femoral stem was noted to be well-fixed preoperatively. Option E (DVT risk reduction) is addressed by pharmacological and mechanical prophylaxis, not by weight-bearing restrictions.

Question 295

Topic: 3. Adult Reconstruction (Hip & Knee)

The patient's past surgical history included a primary THA 15 years prior, followed by a revision THA 5 years ago due to aseptic loosening of the primary acetabular component. The prior revision involved the implantation of a larger, multi-hole cementless acetabular component supplemented with multiple trans-acetabular screws and a bulk femoral head structural allograft to address a significant uncontained superior dome defect. The current failure is attributed to the insidious mechanism of particulate debris-induced osteolysis and subsequent massive periacetabular bone loss, with the structural allograft showing signs of advanced resorption and collapse.

Considering the patient's history of a failed structural allograft, which of the following is the most significant long-term disadvantage of using bulk structural allografts in acetabular reconstruction for massive defects?

. Increased risk of acute periprosthetic joint infection.
. Difficulty in achieving initial mechanical stability.
. High rates of late resorption, non-union, and structural collapse.
. Limited availability and high cost compared to synthetic options.
. Increased risk of nerve injury during implantation.

Correct Answer & Explanation

. High rates of late resorption, non-union, and structural collapse.

Explanation

Correct Answer: CThe case explicitly highlights the known risk of late failure with structural allografts: 'Structural allografts frequently undergo creeping substitution, which can be incomplete, leading to central necrosis, structural collapse, and subsequent loss of component support.' This inherent biological limitation, where the allograft may not fully integrate or may resorb over time, is the most significant long-term disadvantage, leading to loss of support for the acetabular component and subsequent failure.Option A (acute PJI) is a risk with any implant, but not a specific long-term disadvantage unique to structural allografts compared to other options. Option B (difficulty in achieving initial mechanical stability) can be a challenge, but with proper fixation (e.g., reconstruction rings), initial stability can often be achieved. The long-term issue is biological. Option D (limited availability and high cost) can be practical concerns but are not biomechanical or biological disadvantages related to their long-term performance. Option E (increased risk of nerve injury) is a surgical risk associated with complex revision surgery but not a specific long-term disadvantage of the allograft material itself.

Question 296

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old, active, community-ambulating female presents with a displaced intracapsular femoral neck fracture. She has no significant cognitive deficits. What is the primary advantage of performing a total hip arthroplasty (THA) compared to a hemiarthroplasty in this specific patient population?

. Lower postoperative dislocation rate
. Reduced operative time and blood loss
. Lower risk of deep vein thrombosis
. Better long-term functional outcomes and lower revision rates
. Decreased incidence of heterotopic ossification

Correct Answer & Explanation

. Better long-term functional outcomes and lower revision rates

Explanation

In active, lucid, and independent elderly patients with displaced femoral neck fractures, THA is preferred over hemiarthroplasty because it provides superior long-term functional outcomes, less pain, and lower revision rates, despite carrying a slightly higher initial risk of dislocation.

Question 297

Topic: 3. Adult Reconstruction (Hip & Knee)

An 82-year-old female sustains a periprosthetic femur fracture around a cemented total hip arthroplasty following a mechanical fall. Radiographs demonstrate a fracture at the tip of the stem. The stem is clinically and radiographically loose, but there is adequate proximal bone stock. According to the Vancouver classification, what is the most appropriate surgical treatment?

. Open reduction and internal fixation with a lateral locking plate
. Revision to a long uncemented diaphyseal-fitting stem
. Proximal femoral replacement
. Cortical strut allograft only
. Skeletal traction and prolonged bed rest

Correct Answer & Explanation

. Revision to a long uncemented diaphyseal-fitting stem

Explanation

This clinical scenario describes a Vancouver Type B2 fracture (fracture around the stem, loose implant, good bone stock). The gold standard treatment is revision arthroplasty using a long, uncemented, diaphyseal-fitting stem to bypass the fracture.

Question 298

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male is undergoing a total hip arthroplasty (THA) for post-traumatic osteoarthritis 3 years after nonoperative management of a transverse acetabular fracture. Intraoperatively, a nonunion of the posterior column with pelvic discontinuity is identified. Which of the following acetabular reconstruction techniques is most appropriate?

. Standard cementless hemispherical cup
. Jumbo cementless cup to bridge the defect
. Impaction bone grafting with a cemented cup
. Trabecular metal cup with multi-hole screw fixation and a cage/reinforcement ring
. Resection arthroplasty (Girdlestone procedure)

Correct Answer & Explanation

. Trabecular metal cup with multi-hole screw fixation and a cage/reinforcement ring

Explanation

In the setting of pelvic discontinuity or column nonunion during THA, a highly porous (trabecular metal) cup with multi-hole screw fixation, often combined with a cup-cage construct or reinforcement ring, is required to achieve stable fixation and bridge the mechanical discontinuity.

Question 299

Topic: 3. Adult Reconstruction (Hip & Knee)

An 82-year-old female presents with thigh pain and inability to bear weight after a mechanical fall. Radiographs demonstrate a spiral fracture around the stem of her uncemented total hip arthroplasty. The fracture extends just distal to the tip of the stem. Radiographic evaluation shows stem subsidence of 10 mm, but the remaining femoral bone stock is adequate. According to the Vancouver classification, how should this be managed?

. Open reduction and internal fixation (ORIF) with a locking plate and cerclage cables
. Revision to a long uncemented fully porous-coated or fluted modular stem
. Revision to a cemented long stem
. Nonoperative management with a hinged knee brace
. Strut allografting alone

Correct Answer & Explanation

. Revision to a long uncemented fully porous-coated or fluted modular stem

Explanation

This is a Vancouver B2 fracture (fracture around the stem, loose implant, good remaining bone stock). The standard of care is revision arthroplasty using a long, uncemented, extensively porous-coated or fluted tapered modular stem to bypass the fracture by at least two cortical diameters.

Question 300

Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old male presents with a 5-year history of progressive left hip pain, significantly limiting his ability to walk more than 100 meters and perform activities of daily living. He has undergone multiple courses of NSAIDs, physical therapy, and a single intra-articular corticosteroid injection 18 months prior, which provided only 3 months of partial relief. Radiographs confirm Kellgren-Lawrence Grade IV osteoarthritis. He is medically optimized with controlled hypertension, hyperlipidemia, and diet-controlled Type 2 Diabetes Mellitus. He is motivated for surgical intervention. Based on this patient's presentation, what is the most compelling indication for proceeding with Total Hip Arthroplasty (THA)?
. His age of 68 years, making him an ideal candidate for elective surgery.
. His BMI of 29 kg/mยฒ, which is within an acceptable range for THA.
. The failure of comprehensive non-operative management to provide sustained symptomatic relief and functional improvement.
. His well-controlled medical comorbidities, minimizing anesthetic risk.
. His strong desire to return to gardening and occasional cycling.

Correct Answer & Explanation

. The failure of comprehensive non-operative management to provide sustained symptomatic relief and functional improvement.

Explanation

The most compelling indication for Total Hip Arthroplasty (THA) in this patient is the failure of comprehensive non-operative management to provide sustained symptomatic relief and functional improvement. This, combined with severe functional limitations and radiographic evidence of advanced osteoarthritis, are the primary drivers for surgical intervention.

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