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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 216 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 4301

Topic: 3. Adult Reconstruction (Hip & Knee)

To optimize patellar tracking in a patient with a mildly increased Q-angle undergoing primary total knee arthroplasty, which intraoperative adjustment of the femoral component is most appropriate?

. Internal rotation of the femoral component
. Lateral translation of the femoral component
. Medial translation of the femoral component
. Medialization of the patellar component
. Increasing the valgus cut angle of the distal femur

Correct Answer & Explanation

. Lateral translation of the femoral component

Explanation

Lateral translation of the femoral component shifts the trochlear groove laterally, effectively decreasing the Q-angle and improving patellar tracking. Internal rotation of the femoral component would worsen patellar maltracking by medializing the trochlea.

Question 4302

Topic: 3. Adult Reconstruction (Hip & Knee)

During the trial reduction phase of a posterior-stabilized total knee arthroplasty, the knee is found to be excessively tight in both full extension and 90 degrees of flexion. What is the most appropriate next step to balance the knee?

. Resect more distal femur
. Resect more posterior femur
. Resect more proximal tibia
. Release the posterior knee capsule
. Downsize the femoral component

Correct Answer & Explanation

. Resect more proximal tibia

Explanation

The proximal tibial cut affects both the flexion and extension gaps equally. Symmetrical tightness in both gaps is managed by resecting additional proximal tibia or using a thinner polyethylene insert.

Question 4303

Topic: 3. Adult Reconstruction (Hip & Knee)

When setting the rotation of the tibial component in a total knee arthroplasty, referencing off the medial third of the tibial tubercle rather than internally rotating the tray avoids which of the following complications?

. External rotation of the component causing medial patellar subluxation
. Internal rotation of the component causing lateral patellar maltracking
. Posteromedial baseplate overhang leading to pes anserinus bursitis
. Excessive external rotation causing popliteus tendon impingement
. Internal rotation leading to posterolateral corner attenuation

Correct Answer & Explanation

. Internal rotation of the component causing lateral patellar maltracking

Explanation

Internally rotating the tibial component relative to the medial third of the tibial tubercle effectively lateralizes the tibial tubercle relative to the trochlea. This increases the Q-angle and is a primary cause of lateral patellar subluxation and anterior knee pain.

Question 4304

Topic: 3. Adult Reconstruction (Hip & Knee)

In a cruciate-retaining total knee arthroplasty, paradoxical anterior translation of the femur on the tibia during deep flexion is most directly caused by:

. Over-resection of the distal femur
. An incompetent or attenuated posterior cruciate ligament
. An excessively tight flexion gap
. Coronal plane malalignment of the tibial component
. Anterior positioning of the tibial baseplate

Correct Answer & Explanation

. An incompetent or attenuated posterior cruciate ligament

Explanation

The normal function of the PCL is to drive femoral roll-back during knee flexion. If the PCL is incompetent or excessively lax, the femoral condyles paradoxically slide anteriorly on the tibia during flexion, severely limiting the maximum angle of flexion.

Question 4305

Topic: Total Hip Arthroplasty (THA)

A 25-year-old female with severe systemic JIA is undergoing bilateral total hip arthroplasties. Which of the following is the most likely intraoperative finding or technical challenge?

. Coxa valga
. A large medullary canal requiring oversized stems
. Excessive anteversion of the femoral neck
. Subchondral bone sclerosis with massive osteophytes
. Valgus knee deformity causing sciatic nerve palsy post-op

Correct Answer & Explanation

. Excessive anteversion of the femoral neck

Explanation

Patients with JIA commonly exhibit hypoplastic, narrow medullary canals (stovepipe appearance) and excessive femoral neck anteversion. Custom or modular small-sized implants are often required to accommodate the distorted anatomy.

Question 4306

Topic: 3. Adult Reconstruction (Hip & Knee)

A 16-year-old female with polyarticular JIA is scheduled for a bilateral total hip arthroplasty. She is currently managed with methotrexate and etanercept. To minimize the risk of postoperative infection while preventing a severe disease flare, what is the best perioperative medication management strategy?

. Discontinue both medications 4 weeks prior and resume immediately postoperatively
. Continue methotrexate, withhold etanercept 1-2 weeks prior, and resume etanercept after wound healing
. Withhold methotrexate and continue etanercept throughout the perioperative period
. Stop both medications immediately before surgery and resume at 6 weeks
. Continue both medications uninterrupted

Correct Answer & Explanation

. Continue methotrexate, withhold etanercept 1-2 weeks prior, and resume etanercept after wound healing

Explanation

Current ACR/AAHKS guidelines recommend continuing nonbiologic DMARDs like methotrexate perioperatively. Biologics (e.g., etanercept) should be withheld for one dosing cycle before surgery and resumed once the wound has healed.

Question 4307

Topic: 3. Adult Reconstruction (Hip & Knee)

The pathogenesis of neuropathic (Charcot) arthropathy is traditionally described by two main theories: the neurotraumatic theory and the neurovascular theory. Which of the following best describes the core tenet of the neurovascular theory?

. Repetitive unrecognized microtrauma leads to joint destruction.
. Loss of autonomic sympathetic control leads to hyperemia and active bone resorption.
. Microvascular thrombosis causes avascular necrosis of subchondral bone.
. Diabetic microangiopathy directly causes chondrocyte apoptosis.
. Ectopic nerve sprouting induces severe inflammatory pannus.

Correct Answer & Explanation

. Loss of autonomic sympathetic control leads to hyperemia and active bone resorption.

Explanation

The neurovascular theory postulates that autonomic neuropathy leads to a loss of sympathetic tone, causing intense regional hyperemia. This increased blood flow stimulates active osteoclastic bone resorption, weakening the bone.

Question 4308

Topic: 3. Adult Reconstruction (Hip & Knee)

A 35-year-old man presents with chronic knee pain, swelling, and mechanical locking. Imaging demonstrates multiple calcified loose bodies of relatively uniform size within the joint space.

Which of the following is the most appropriate definitive management?

. Observation and NSAIDs
. Arthroscopic loose body removal only
. Arthroscopic loose body removal and synovectomy
. Total knee arthroplasty
. Intra-articular radiation therapy

Correct Answer & Explanation

. Arthroscopic loose body removal and synovectomy

Explanation

Primary synovial chondromatosis requires both loose body removal and complete synovectomy to minimize the risk of recurrence. Removing only the loose bodies leaves the diseased synovium intact, leading to unacceptably high recurrence rates.

Question 4309

Topic: 3. Adult Reconstruction (Hip & Knee)

A 40-year-old male presents with chronic hip pain and decreased range of motion. Radiographs show numerous calcified loose bodies of similar size within the hip joint capsule.

What is the best initial surgical management if conservative treatment fails?

. Total hip arthroplasty
. Surgical hip dislocation and synovectomy
. Arthroscopic loose body removal without synovectomy
. Core decompression
. Radiation therapy

Correct Answer & Explanation

. Surgical hip dislocation and synovectomy

Explanation

Primary synovial chondromatosis features metaplasia of the synovial lining into cartilage, producing uniform loose bodies. Treatment requires loose body removal combined with extensive synovectomy to minimize recurrence, often facilitated by surgical dislocation in the hip.

Question 4310

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient undergoes a total knee arthroplasty. To optimize the fixation of the femoral component, a stem is used. What type of stem cross-section, assuming similar cross-sectional area, would provide the most biomechanical resistance to bending and torsional forces encountered during knee motion?

. A solid circular stem
. A hollow circular stem with a large outer diameter
. A solid square stem
. A solid rectangular stem, oriented along the primary bending plane
. A tapered solid circular stem

Correct Answer & Explanation

. A hollow circular stem with a large outer diameter

Explanation

A hollow circular stem with a large outer diameter, for the same cross-sectional area, provides the most biomechanical resistance to bending and torsional forces. This design maximizes the Area Moment of Inertia and Polar Moment of Inertia by distributing the material furthest from the neutral axis, making it highly efficient in resisting multi-directional loads common in joint arthroplasty. While a rectangular stem can be optimized for specific bending planes, the hollow circular design offers more balanced, omni-directional resistance for a given material amount.

Question 4311

Topic: 3. Adult Reconstruction (Hip & Knee)

A surgeon is performing plate fixation of a periprosthetic femur fracture around a total hip arthroplasty stem. What is a key consideration for screw placement in the fragment containing the femoral stem?

. Always use bicortical screws to ensure maximum purchase.
. Ensure screws are parallel to the long axis of the stem to avoid impingement.
. Screws must not engage the femoral stem to prevent loosening of the implant.
. Prioritize locking screws over conventional screws due to compromised bone quality.
. Only monocortical screws should be used to avoid damage to the stem.

Correct Answer & Explanation

. Screws must not engage the femoral stem to prevent loosening of the implant.

Explanation

When fixing a periprosthetic fracture, a critical consideration is to ensure that the screwsdo not engage or contact the pre-existing femoral stem. Screws impacting the stem can damage the stem, loosen the stem's cement mantle, or cause screw bending/failure. Therefore, screws must be carefully placed monocortically or bicortically (if there is enough bone lateral to the stem) to avoid the implant. While locking screws are often used due to potential osteopenia, theavoidanceof the stem is paramount. Screw angulation and depth are carefully controlled, often with variable-angle locking plates, to achieve this.

Question 4312

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary concern when implanting screws into cortical bone at high rotational speeds?

. Risk of stripping the screw threads.
. Increased likelihood of screw breakage.
. Thermal necrosis of surrounding bone tissue.
. Reduced pullout strength due to bone compaction.
. Difficulty in achieving appropriate screw depth.

Correct Answer & Explanation

. Thermal necrosis of surrounding bone tissue.

Explanation

High rotational speeds during screw insertion, especially without adequate cooling, can generate significant heat. This heat can cause thermal necrosis (death) of the surrounding bone tissue, compromising the screw-bone interface, leading to aseptic loosening, and potentially impeding bone healing. While stripping threads or breakage are possible with excessive torque, thermal necrosis is a specific concern related to high speed and lack of cooling during drilling and screwing.

Question 4313

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient undergoes fixation of a proximal humeral fracture with a locking plate. Postoperatively, you notice a lucency around several locking screws. What is the most likely cause of this lucency in the absence of infection?

. Stress shielding leading to localized bone resorption.
. Excessive interfragmentary compression at the screw-bone interface.
. Inadequate primary stability, leading to micromotion and osteolysis.
. Migration of metallic debris from the screw into the surrounding bone.
. Normal physiological response to the presence of an implant.

Correct Answer & Explanation

. Stress shielding leading to localized bone resorption.

Explanation

Lucency around locking screws in a locking plate construct, in the absence of infection, is often attributed to stress shielding. Locking plates create a very rigid construct, which can shield the underlying bone from physiological loads. This lack of stress can lead to localized bone resorption around the screws, known as stress shielding osteopenia, or can be a sign of inadequate load transfer through the bone, rather than through the implant. In non-locking screws, lucency typically indicates loosening due to micromotion. However, locking screws are designed to prevent micromotion at the screw-plate interface, so lucency around locking screws suggests a different biomechanical phenomenon, often related to stress shielding.

Question 4314

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is a potential complication specifically associated with the long-term presence of bioabsorbable screws?

. Stress shielding of the adjacent bone.
. Persistent pain due to screw head prominence.
. Aseptic osteolysis or sterile effusion.
. Fatigue fracture of the implant.
. Corrosion and metal ion release.

Correct Answer & Explanation

. Aseptic osteolysis or sterile effusion.

Explanation

While bioabsorbable screws avoid permanent implant presence, a known complication is the potential for an inflammatory response, leading to aseptic osteolysis (bone resorption) or sterile effusion (fluid collection) as the material degrades. This reaction is usually benign and self-limiting but can sometimes require intervention. Stress shielding, prominence, fatigue fracture, and corrosion/metal ion release are typically associated with metallic implants.

Question 4315

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following total hip arthroplasty bearing surfaces is associated with the lowest volumetric wear rate but carries the specific complication risk of stripe wear and squeaking?

. Cobalt-chrome on highly cross-linked polyethylene
. Ceramic on highly cross-linked polyethylene
. Ceramic on ceramic
. Metal on metal
. Oxinium on highly cross-linked polyethylene

Correct Answer & Explanation

. Ceramic on ceramic

Explanation

Ceramic-on-ceramic bearings have the lowest volumetric wear rates of all modern bearing surfaces and produce biologically inert wear debris. However, they carry unique risks including catastrophic brittle fracture, squeaking (due to edge loading or loss of fluid film lubrication), and stripe wear.

Question 4316

Topic: Total Knee Arthroplasty (TKA)

In mechanical alignment principles for total knee arthroplasty (TKA), the femoral component should typically be placed in what degree of external rotation relative to the posterior condylar axis to ensure symmetric flexion gaps?

. 0 degrees
. 3 degrees
. 5 degrees
. 7 degrees
. 10 degrees

Correct Answer & Explanation

. 3 degrees

Explanation

In standard mechanical alignment for TKA, the femoral component is typically externally rotated 3 degrees relative to the posterior condylar axis. This compensates for the natural 3-degree varus angle of the proximal tibia (which is cut perpendicularly in mechanical alignment), helping to create a rectangular, balanced flexion gap.

Question 4317

Topic: 3. Adult Reconstruction (Hip & Knee)

In conventional metal-on-polyethylene total hip arthroplasty, osteolysis and aseptic loosening are primarily driven by a macrophage-mediated response to particulate debris. What is the size range of polyethylene wear particles that is most biologically active in stimulating this macrophage-mediated osteolytic response?

. 0.1 to 1.0 micrometers
. 5 to 10 micrometers
. 15 to 25 micrometers
. 50 to 100 micrometers
. 100 to 500 micrometers

Correct Answer & Explanation

. 0.1 to 1.0 micrometers

Explanation

Submicron polyethylene particles, specifically in the size range of 0.1 to 1.0 micrometers (often averaging ~0.5 microns), are the most biologically active. Macrophages readily phagocytose particles of this size but cannot digest them, leading to cellular activation and the release of pro-inflammatory cytokines (TNF-alpha, IL-1, IL-6), which subsequently stimulate osteoclastogenesis and periprosthetic osteolysis.

Question 4318

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male, 6 months post-total knee arthroplasty, presents with acute onset of severe knee pain, warmth, swelling, and fever (38.5°C). Aspiration of the knee joint yields cloudy fluid with a white blood cell count of 120,000 cells/µL, 95% neutrophils, and positive gram stain for Gram-positive cocci in clusters. He is hemodynamically stable. What is the most appropriate management?

. Oral antibiotics and observation.
. Intravenous antibiotics and urgent debridement, antibiotics, and implant retention (DAIR).
. Two-stage revision arthroplasty.
. Arthrodesis.
. Above-knee amputation.

Correct Answer & Explanation

. Intravenous antibiotics and urgent debridement, antibiotics, and implant retention (DAIR).

Explanation

This patient presents with an acute prosthetic joint infection (PJI) within the 'acute hematogenous' window (typically up to 6 months, though sometimes longer). The key indicators for DAIR (Debridement, Antibiotics, and Implant Retention) are: acute onset (symptoms <3 weeks), a well-fixed implant, and a susceptible organism, in a stable patient. The high WBC count and Gram-positive cocci confirm active infection. DAIR aims to eradicate the infection while preserving the functional implant. Oral antibiotics alone (A) are insufficient for acute PJI. Two-stage revision (C) is typically reserved for chronic PJI or failed DAIR. Arthrodesis (D) or amputation (E) are salvage procedures for failed multiple revisions or intractable infection.

Question 4319

Topic: Total Hip Arthroplasty (THA)

A 75-year-old female, 3 weeks post-posterior approach total hip arthroplasty, presents to the ER after a fall with sudden, severe hip pain and inability to bear weight. Physical examination reveals a shortened, internally rotated, and adducted left lower extremity. Radiographs confirm posterior dislocation of the prosthetic femoral head. After successful closed reduction under sedation, what is the most appropriate next step in management to prevent recurrence?

. Immediate revision surgery of the femoral head and acetabular liner.
. Application of a hip abduction brace for 6-8 weeks.
. Initiation of physical therapy focusing on strengthening hip abductors.
. Prescribe extended bed rest.
. Observation with strict non-weight bearing.

Correct Answer & Explanation

. Application of a hip abduction brace for 6-8 weeks.

Explanation

This patient experienced an acute, first-time posterior dislocation after THA. Following successful closed reduction, the immediate priority is to prevent recurrence while soft tissues heal. A hip abduction brace (B) is commonly used for 6-8 weeks to restrict extreme hip flexion, adduction, and internal rotation, which are the positions of instability for a posterior approach. Immediate revision surgery (A) is typically reserved for recurrent dislocations, component malposition, or failed non-operative management. While physical therapy (C) is important, it needs to be protected in the immediate post-reduction period. Bed rest (D) is not beneficial and can lead to complications. Observation with non-weight bearing (E) alone is insufficient to prevent recurrence.

Question 4320

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female with a well-fixed, cemented femoral stem (dating back 15 years) sustains a fall and develops sudden right thigh pain and inability to bear weight. Radiographs show a Vancouver B1 periprosthetic femoral fracture. Which of the following is the most appropriate management?

. Revision arthroplasty with a longer, cemented stem.
. Open reduction and internal fixation with plates and screws, preserving the existing stem.
. Non-weight bearing and observation for 6 weeks.
. Excision arthroplasty.
. Cementless revision stem with distal fixation.

Correct Answer & Explanation

. Open reduction and internal fixation with plates and screws, preserving the existing stem.

Explanation

A Vancouver B1 periprosthetic femoral fracture indicates a fracture around a well-fixed femoral stem, with no radiographic or intraoperative evidence of stem loosening or failure. The treatment of choice for a B1 fracture is open reduction and internal fixation (ORIF) with plates and screws (often utilizing cables and a long plate that bypasses the fracture and extends beyond the tip of the existing stem), thereby preserving the existing, well-fixed prosthesis. Revision arthroplasty with a new stem (Options A and E) is indicated for B2 (loose stem) or B3 (poor bone stock) fractures, where the original stem is either loose or cannot provide adequate fixation. Non-weight bearing and observation (Option C) are insufficient for this type of fracture, which requires stable fixation to heal. Excision arthroplasty (Option D) is a salvage procedure reserved for severe infection or unfixable cases.

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