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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 302 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 6021

Topic: 3. Adult Reconstruction (Hip & Knee)
A patient develops a suspected metal hypersensitivity reaction following a total knee arthroplasty, presenting with a painful, swollen joint and overlying eczematous dermatitis. This reaction is primarily mediated by which of the following components of the immune system?
. B lymphocytes and IgE antibodies
. Neutrophils and immune complexes
. T lymphocytes
. Mast cell degranulation
. Eosinophils

Correct Answer & Explanation

. T lymphocytes

Explanation

Metal hypersensitivity (e.g., to nickel, cobalt, or chromium) is a Type IV (delayed-type) hypersensitivity reaction. Unlike Types I, II, and III, which are antibody-mediated, Type IV is a cell-mediated response driven primarily by sensitized T lymphocytes that release pro-inflammatory cytokines upon antigen re-exposure.

Question 6022

Topic: 3. Adult Reconstruction (Hip & Knee)

In total joint arthroplasty, which distinct type of wear is characterized by cyclic load transferring between two bearing surfaces resulting in subsurface microcracks and subsequent macroscopic delamination?

. Adhesive wear
. Abrasive wear
. Fatigue wear
. Third-body wear
. Corrosive wear

Correct Answer & Explanation

. Fatigue wear

Explanation

Fatigue wear occurs from repetitive cyclical loading that creates subsurface shear stresses, leading to microcracks that coalesce and cause macroscopic material delamination. This is classically seen in non-crosslinked polyethylene components.

Question 6023

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the AAOS clinical practice guidelines, which of the following is an acceptable strategy for VTE prophylaxis following an elective total hip arthroplasty in a patient with a standard risk profile?

. Aspirin alone
. Mechanical compression devices alone
. Early mobilization without pharmacologic or mechanical prophylaxis
. Warfarin with a target INR of 3.0-4.0
. Intravenous unfractionated heparin

Correct Answer & Explanation

. Aspirin alone

Explanation

AAOS guidelines state that for patients undergoing elective THA or TKA with standard risk, aspirin is an acceptable pharmacologic agent for VTE prophylaxis. Warfarin is an option but the target INR is strictly 2.0-3.0, not 3.0-4.0. Mechanical devices alone are generally reserved for those with high bleeding risks who cannot tolerate any chemical prophylaxis.

Question 6024

Topic: 3. Adult Reconstruction (Hip & Knee)

A 42-year-old female presents with hand pain. Radiographs reveal prominent subperiosteal bone resorption on the radial aspect of the middle phalanges and acro-osteolysis. What is the most likely laboratory profile for this patient?

. Elevated serum calcium and decreased PTH
. Decreased serum calcium and elevated PTH
. Elevated serum calcium and elevated PTH
. Normal serum calcium and normal PTH
. Decreased serum calcium and decreased PTH

Correct Answer & Explanation

. Elevated serum calcium and elevated PTH

Explanation

Subperiosteal resorption on the radial aspect of the middle phalanges is the pathognomonic radiographic sign of hyperparathyroidism. Primary hyperparathyroidism classically presents with both elevated parathyroid hormone (PTH) and elevated serum calcium.

Question 6025

Topic: 3. Adult Reconstruction (Hip & Knee)

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

. Ceramic-on-polyethylene
. Metal-on-polyethylene
. Ceramic-on-ceramic
. Metal-on-metal
. Oxinium-on-polyethylene

Correct Answer & Explanation

. Ceramic-on-ceramic

Explanation

Stripe wear is a linear pattern of wear unique to ceramic-on-ceramic articulations. It is caused by micro-separation of the femoral head from the acetabular liner during the swing phase of gait, leading to edge loading when the head re-engages the liner at heel strike.

Question 6026

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) criteria, which of the following is considered a major criterion for definitively diagnosing a periprosthetic joint infection (PJI)?

. Elevated serum CRP and ESR
. Purulence in the affected joint
. A single positive intraoperative tissue culture
. Elevated synovial fluid leukocyte esterase
. Two positive periprosthetic cultures with phenotypically identical organisms

Correct Answer & Explanation

. Two positive periprosthetic cultures with phenotypically identical organisms

Explanation

The two major criteria for PJI are the presence of a sinus tract communicating with the joint and two positive periprosthetic cultures with phenotypically identical organisms. Purulence alone is no longer considered a major definitive criterion.

Question 6027

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female undergoes a primary total hip arthroplasty via a posterior approach. Postoperatively, she experiences recurrent posterior dislocations. Which of the following component malpositioning errors most frequently contributes to this specific instability pattern?

. Excessive acetabular anteversion
. Excessive femoral anteversion
. Acetabular retroversion
. Excessive acetabular abduction
. Increased femoral offset

Correct Answer & Explanation

. Acetabular retroversion

Explanation

Acetabular retroversion (or insufficient anteversion) strongly predisposes the hip to posterior dislocation, particularly during hip flexion and internal rotation. Proper acetabular anteversion (usually 15-20 degrees) is critical for posterior stability.

Question 6028

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old patient presents with osteolysis 10 years after a total hip arthroplasty using a highly cross-linked polyethylene liner. What is the primary mechanism by which highly cross-linked polyethylene reduces wear compared to conventional polyethylene?

. Increased crystallinity
. Decreased free radicals
. Increased covalent bonds between polymer chains
. Addition of vitamin E
. Decreased molecular weight

Correct Answer & Explanation

. Increased covalent bonds between polymer chains

Explanation

Cross-linking introduces covalent bonds between adjacent polyethylene chains, significantly reducing adhesive and abrasive wear. Post-irradiation melting or annealing eliminates free radicals to prevent oxidation, but the cross-linking itself primarily reduces wear.

Question 6029

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female presents with acute onset of knee pain and swelling 3 years after a total knee arthroplasty. Joint aspiration yields 60,000 WBCs/uL with 95% neutrophils. Which of the following is the most appropriate initial surgical management?

. Arthroscopic irrigation and debridement
. Open debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange
. Single-stage revision arthroplasty
. Two-stage revision arthroplasty with an antibiotic spacer
. Suppressive oral antibiotic therapy

Correct Answer & Explanation

. Two-stage revision arthroplasty with an antibiotic spacer

Explanation

For a late, acute hematogenous prosthetic joint infection (or chronic PJI), a two-stage revision with an antibiotic spacer is the gold standard. DAIR is generally reserved for early postoperative infections within 4 weeks of surgery or acute symptom duration less than 3 weeks.

Question 6030

Topic: 3. Adult Reconstruction (Hip & Knee)

According to current AAOS and ACCP guidelines, which of the following is the recommended maximum duration of venous thromboembolism (VTE) prophylaxis following an elective total hip arthroplasty in a patient with standard risk?

. 7 to 10 days
. 10 to 14 days
. 14 to 21 days
. Up to 35 days
. 60 days

Correct Answer & Explanation

. Up to 35 days

Explanation

Current guidelines recommend extending VTE prophylaxis for up to 35 days following elective total hip and knee arthroplasty. The risk of thromboembolic events remains elevated during this extended postoperative period.

Question 6031

Topic: 3. Adult Reconstruction (Hip & Knee)
What is the primary biologic mechanism of osteolysis following total hip arthroplasty with ultra-high-molecular-weight polyethylene (UHMWPE) wear?
. Neutrophil-mediated respiratory burst
. Macrophage phagocytosis of 0.1 to 1.0 micrometer particles
. Osteoblast apoptosis triggered by metal ions
. T-cell mediated delayed hypersensitivity
. Direct chemical toxicity of polyethylene degradation products

Correct Answer & Explanation

. Macrophage phagocytosis of 0.1 to 1.0 micrometer particles

Explanation

Polyethylene wear debris in the size range of 0.1 to 1.0 micrometers is phagocytosed by macrophages. This triggers an inflammatory cascade releasing cytokines (IL-1, TNF-alpha) that activate osteoclasts, leading to periprosthetic osteolysis.

Question 6032

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old active male undergoes total hip arthroplasty using a ceramic-on-ceramic bearing. Three years postoperatively, he complains of a reproducible squeaking noise during gait. Which of the following component position factors is most strongly associated with this phenomenon?

. Femoral stem retroversion
. Edge loading due to acetabular cup malpositioning
. Impingement from a large-diameter femoral head
. Third-body wear from retained cement
. Galvanic corrosion at the trunnion

Correct Answer & Explanation

. Edge loading due to acetabular cup malpositioning

Explanation

Squeaking in ceramic-on-ceramic THA is heavily associated with edge loading of the bearing surfaces. This edge loading typically results from component malpositioning, such as excessive steepness or abnormal version of the acetabular cup.

Question 6033

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty, trial reduction reveals that the knee is equally tight in both flexion and extension. Overall limb alignment and component rotations are correct. What is the most appropriate next step to balance the knee?

. Downsize the femoral component
. Recut the proximal tibia to remove more bone
. Release the posterior cruciate ligament
. Resect more distal femur
. Increase the thickness of the polyethylene insert

Correct Answer & Explanation

. Recut the proximal tibia to remove more bone

Explanation

When a knee is symmetrically tight in both flexion and extension, equivalent resection of bone is required to increase both gaps globally. Recutting the proximal tibia effectively enlarges both the flexion and extension spaces by the same amount.

Question 6034

Topic: 3. Adult Reconstruction (Hip & Knee)

Osteolysis surrounding a total hip arthroplasty with a highly cross-linked polyethylene liner is primarily driven by an inflammatory response to particulate debris. Which of the following cells is the primary mediator of this osteolytic process?

. Osteoblasts
. T-lymphocytes
. Macrophages
. Polymorphonuclear leukocytes
. Fibroblasts

Correct Answer & Explanation

. Macrophages

Explanation

Macrophages phagocytose polyethylene wear particles and release inflammatory cytokines like TNF-alpha and IL-6. This cascade stimulates osteoclast differentiation and activity via the RANK/RANKL pathway, leading to periprosthetic osteolysis.

Question 6035

Topic: 3. Adult Reconstruction (Hip & Knee)

A new diagnostic test for periprosthetic joint infection is evaluated against the gold standard. Out of 100 infected cases, the test correctly identifies 90. Out of 100 uninfected cases, the test falsely identifies 20 as infected. What is the negative predictive value of this test?

. 80%
. 81.8%
. 88.8%
. 90%
. 95%

Correct Answer & Explanation

. 88.8%

Explanation

Negative Predictive Value (NPV) is True Negatives / (True Negatives + False Negatives). TN = 80 (100-20), FN = 10 (100-90). NPV = 80 / (80 + 10) = 80/90 = 88.8%.

Question 6036

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male underwent a total knee arthroplasty 8 years ago. He now presents with increasing knee pain, swelling, and warmth for 3 months, without preceding trauma. His ESR is 75 mm/hr and CRP is 85 mg/L. Joint aspiration yields a cloudy fluid. Which of the following synovial fluid analyses is most indicative of a chronic periprosthetic joint infection?

. White Blood Cell count < 1,000 cells/ยตL with 50% neutrophils.
. White Blood Cell count 3,500 cells/ยตL with 65% neutrophils.
. White Blood Cell count 15,000 cells/ยตL with 80% neutrophils.
. White Blood Cell count 80,000 cells/ยตL with 95% neutrophils.
. Positive crystal identification for calcium pyrophosphate dihydrate (CPPD).

Correct Answer & Explanation

. White Blood Cell count 15,000 cells/ยตL with 80% neutrophils.

Explanation

For diagnosing chronic periprosthetic joint infection (PJI) of the knee, the Musculoskeletal Infection Society (MSIS) criteria (and similar guidelines) generally define PJI based on a synovial fluid white blood cell (WBC) count of >3,000 cells/ยตL and/or a neutrophil percentage of >60-80%. Option C (15,000 cells/ยตL with 80% neutrophils) clearly meets these criteria, indicating a high likelihood of infection. Option B is borderline and might be considered suspicious but less definitive. Option A suggests an aseptic process. Option D is more indicative of an acute septic arthritis or acute PJI. Option E suggests crystal-induced arthropathy, which can mimic infection but is not PJI.

Question 6037

Topic: Total Hip Arthroplasty (THA)

A 65-year-old male presents with groin pain 5 years after a primary total hip arthroplasty using a metal-on-polyethylene bearing with a modular titanium stem and cobalt-chromium head. Abrasive wear at the head-neck junction (trunnionosis) is suspected. Which of the following serum markers is most likely to be elevated?

. Titanium
. Cobalt
. Chromium
. Molybdenum
. Vanadium

Correct Answer & Explanation

. Cobalt

Explanation

Mechanically assisted crevice corrosion (MACC) at the modular head-neck junction (trunnionosis) typically produces disproportionately elevated serum cobalt levels compared to chromium. This differs from metal-on-metal bearing wear, which typically produces roughly equal elevations.

Question 6038

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with groin pain 5 years after receiving a metal-on-metal total hip arthroplasty. Aspiration yields sterile, thick, grey fluid. MRI with metal artifact reduction sequence (MARS) shows a solid and cystic mass communicating with the joint space. What is the most likely diagnosis?

. Periprosthetic joint infection
. Adverse local tissue reaction (ALTR)
. Polyethylene wear debris osteolysis
. Pigmented villonodular synovitis (PVNS)
. Synovial chondromatosis

Correct Answer & Explanation

. Adverse local tissue reaction (ALTR)

Explanation

ALTR or pseudotumor is a known complication of metal-on-metal hip bearings due to a delayed type IV hypersensitivity reaction to metal debris. MARS MRI is the imaging modality of choice to characterize these soft tissue masses.

Question 6039

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female undergoes a routine primary total knee arthroplasty for severe valgus osteoarthritis. In the recovery room, she reports numbness in the dorsum of her foot and is unable to actively dorsiflex her ankle. Vascular exam is normal. What is the most likely cause of this complication?

. Intraoperative popliteal artery injury
. Tourniquet-induced sciatic nerve palsy
. Direct injury or stretch to the common peroneal nerve
. Spinal anesthesia complication
. Postoperative compartment syndrome

Correct Answer & Explanation

. Direct injury or stretch to the common peroneal nerve

Explanation

Foot drop following TKA is most commonly due to a common peroneal nerve injury, often resulting from stretch during the correction of severe valgus deformities. Immediate management typically involves loosening dressings and positioning the knee in slight flexion to relieve nerve tension.

Question 6040

Topic: Total Hip Arthroplasty (THA)

A 65-year-old woman undergoes a primary total hip arthroplasty. Six weeks postoperatively, she dislocates her hip while tying her shoe in a seated position. Which surgical approach was most likely utilized, and which structure's insufficiency contributes most to this specific instability?

. Anterior approach; rectus femoris
. Anterior approach; iliofemoral ligament
. Posterior approach; short external rotators and capsule
. Lateral approach; gluteus medius
. Anterolateral approach; gluteus minimus

Correct Answer & Explanation

. Posterior approach; short external rotators and capsule

Explanation

Dislocation while tying a shoe requires deep flexion, adduction, and internal rotation, which classically provokes posterior dislocation. The posterior approach is associated with this instability due to disruption of the posterior capsule and short external rotators.

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