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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 220 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 4381

Topic: 3. Adult Reconstruction (Hip & Knee)

When fabricating an articulating cement spacer for a two-stage revision total knee arthroplasty to treat a fungal PJI (Candida species), which of the following antimicrobial agents should be mixed into the polymethylmethacrylate (PMMA) bone cement?

. Fluconazole
. Amphotericin B
. Caspofungin
. Ketoconazole
. Micafungin

Correct Answer & Explanation

. Amphotericin B

Explanation

Amphotericin B and voriconazole are commonly used in PMMA for fungal PJI. Amphotericin B has a well-documented release profile and is heat-stable, making it the most suitable and traditional choice for cement spacers in fungal infections.

Question 4382

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male undergoes a revision anatomic total shoulder arthroplasty for presumed aseptic loosening. At 10 days, 3 out of 5 intraoperative cultures grow Cutibacterium acnes. Which of the following describes the most characteristic trait of this organism in periprosthetic shoulder infections?

. Aerobic gram-negative rod
. Rapidly growing on standard blood agar
. Resistant to penicillin and cephalosporins
. Anaerobic, slow-growing gram-positive bacillus
. Produces alpha-defensin independently

Correct Answer & Explanation

. Anaerobic, slow-growing gram-positive bacillus

Explanation

Cutibacterium (formerly Propionibacterium) acnes is an anaerobic, slow-growing, gram-positive bacillus commonly implicated in shoulder PJI. Cultures should be held for at least 14 days to maximize the detection of this indolent organism.

Question 4383

Topic: 3. Adult Reconstruction (Hip & Knee)

Chronic antibiotic suppression is most appropriate for which of the following patients with a confirmed periprosthetic joint infection?

. A 50-year-old with an acute postoperative MRSA infection and stable implants
. A 65-year-old with a radiographically loose femoral component and Enterococcus faecalis infection
. An 82-year-old with severe dementia, an unacceptably high surgical risk, and a well-fixed implant
. A 40-year-old with a chronic sinus tract and normal inflammatory markers
. A 70-year-old with acute hematogenous Candida PJI

Correct Answer & Explanation

. An 82-year-old with severe dementia, an unacceptably high surgical risk, and a well-fixed implant

Explanation

Chronic antibiotic suppression is reserved for patients who are medically unfit for surgery or refuse further operations, provided the implant is radiographically stable and the organism is susceptible to a tolerated oral antibiotic. A loose implant or a chronic sinus tract are relative contraindications.

Question 4384

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following radiographic findings in the hand is considered a classic hallmark of systemic sclerosis?

. Periarticular osteopenia and marginal erosions
. Pencil-in-cup deformities of the distal interphalangeal joints
. Resorption of the terminal phalangeal tufts (acro-osteolysis)
. Subchondral cysts and large osteophyte formation
. Chondrocalcinosis of the triangular fibrocartilage complex

Correct Answer & Explanation

. Resorption of the terminal phalangeal tufts (acro-osteolysis)

Explanation

Acro-osteolysis, which is the resorption of the terminal phalangeal tufts, is a classic radiographic feature of systemic sclerosis. It is often accompanied by soft tissue thinning and calcinosis cutis.

Question 4385

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following conditions is most likely to cause a false-positive synovial alpha-defensin test in the workup of a painful total hip arthroplasty?

. Gouty arthropathy
. Metallosis
. Polyethylene wear
. Rheumatoid arthritis
. Osteolysis

Correct Answer & Explanation

. Metallosis

Explanation

Metallosis and adverse local tissue reactions to metal debris can cause a false-positive alpha-defensin result. Although alpha-defensin is an antimicrobial peptide highly specific for PJI, severe metallic debris reactions mimic the inflammatory profile sufficiently to trigger false positives.

Question 4386

Topic: 3. Adult Reconstruction (Hip & Knee)

A 42-year-old woman with a history of systemic sclerosis presents with progressive shortening and pain in her fingertips. Radiographs show resorption of the distal phalangeal tufts.

What vascular phenomenon is most characteristically associated with the pathogenesis of this skeletal finding?

. Septic microemboli
. Exaggerated sympathetic vasoconstriction
. Small vessel necrotizing vasculitis
. Arteriovenous malformations
. Atherosclerotic occlusion

Correct Answer & Explanation

. Exaggerated sympathetic vasoconstriction

Explanation

The radiograph demonstrates acro-osteolysis, which in systemic sclerosis is driven by chronic ischemia. This ischemia results from Raynaud's phenomenon (an exaggerated sympathetic vasoconstrictive response) coupled with progressive digital microvasculopathy.

Question 4387

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male develops a delayed periprosthetic joint infection 1 year following a reverse total shoulder arthroplasty. Cultures eventually grow Cutibacterium acnes. Which of the following best describes the microbiological characteristics of this organism?

. Gram-negative obligate aerobe
. Gram-positive aerobic coccus
. Gram-positive anaerobic bacillus
. Gram-negative facultative anaerobe
. Acid-fast branching bacillus

Correct Answer & Explanation

. Gram-positive anaerobic bacillus

Explanation

Cutibacterium (formerly Propionibacterium) acnes is a slow-growing, Gram-positive, anaerobic (or microaerophilic) bacillus commonly found in the sebaceous glands of the shoulder. Extended culture incubation (up to 14 days) is required to maximize detection.

Question 4388

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with acute onset knee pain and swelling 3 weeks after an uncomplicated total knee arthroplasty. Aspiration yields 55,000 WBC/uL with 95% neutrophils. What is the most appropriate surgical management?

. One-stage exchange arthroplasty
. Two-stage exchange arthroplasty
. Suppressive antibiotics only
. Irrigation and debridement with polyethylene exchange (DAIR)
. Knee arthrodesis

Correct Answer & Explanation

. Irrigation and debridement with polyethylene exchange (DAIR)

Explanation

Irrigation and debridement with modular exchange (DAIR) is indicated for acute postoperative periprosthetic joint infections, typically defined as occurring within 4 weeks of the index surgery. It is also indicated for acute hematogenous infections with well-fixed implants.

Question 4389

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following synovial fluid biomarkers is an antimicrobial peptide produced by neutrophils and serves as an important adjunctive test for diagnosing periprosthetic joint infection due to its high accuracy, even in the setting of concurrent systemic inflammatory diseases?

. C-reactive protein (CRP)
. Interleukin-6 (IL-6)
. Alpha-defensin
. Procalcitonin
. Leukocyte esterase

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin is a biomarker released by neutrophils in response to pathogens. It demonstrates high sensitivity and specificity for diagnosing PJI, remaining reliable even if the patient has received prior antibiotics or has an underlying inflammatory arthropathy.

Question 4390

Topic: 3. Adult Reconstruction (Hip & Knee)

A 50-year-old woman with a history of systemic sclerosis presents with worsening fingertip pain.

Radiographs show resorption of the terminal phalangeal tufts. What is this radiographic finding termed?

. Calcinosis cutis
. Acro-osteolysis
. Periostitis
. Osteopoikilosis
. Melorheostosis

Correct Answer & Explanation

. Acro-osteolysis

Explanation

Acro-osteolysis refers to the resorption of the distal phalangeal tufts, a finding commonly seen in scleroderma, Raynaud's phenomenon, and secondary hyperparathyroidism. In scleroderma, it is primarily driven by chronic digital ischemia.

Question 4391

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient is undergoing revision of a loose total hip arthroplasty. Preoperative aspirates were culture-negative despite elevated serum inflammatory markers. To improve diagnostic yield, the explanted components are subjected to sonication. What is the primary mechanism by which sonication increases the sensitivity of cultures?

. It concentrates planktonic bacteria from the synovial fluid
. It physically disrupts the bacterial cell wall to release DNA
. It dislodges biofilm-associated organisms from the implant surface
. It neutralizes residual systemic antibiotics
. It selectively destroys normal host flora

Correct Answer & Explanation

. It dislodges biofilm-associated organisms from the implant surface

Explanation

Sonication uses low-frequency ultrasound to physically disrupt and dislodge biofilms adhering to explanted hardware. This process releases sessile bacteria into the fluid, significantly improving culture sensitivity in PJI.

Question 4392

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old diabetic male is diagnosed with a Candida albicans periprosthetic joint infection of the knee. What is the generally recommended surgical and medical management strategy for a chronic fungal PJI?

. One-stage exchange arthroplasty with fluconazole-impregnated cement
. DAIR followed by lifelong oral fluconazole
. Two-stage exchange arthroplasty with systemic antifungal therapy
. Suppressive therapy with amphotericin B alone
. Knee arthrodesis using an intramedullary nail

Correct Answer & Explanation

. Two-stage exchange arthroplasty with systemic antifungal therapy

Explanation

Fungal PJIs are notoriously difficult to eradicate due to robust biofilm formation and lack of approved antifungal-loaded cements for spacers. A two-stage exchange, typically combined with extended systemic antifungal therapy, is the gold standard for treatment.

Question 4393

Topic: 3. Adult Reconstruction (Hip & Knee)

A 42-year-old female with systemic sclerosis presents with severe flexion contractures of the proximal interphalangeal (PIP) joints and limited hand function.

Which of the following best describes the pathogenesis of her joint contractures?

. Primary synovial hypertrophy and pannus formation
. Progressive fibrosis of the skin and subcutaneous tissues
. Crystal deposition in the articular cartilage
. Avascular necrosis of the phalangeal heads
. Recurrent hemarthrosis

Correct Answer & Explanation

. Progressive fibrosis of the skin and subcutaneous tissues

Explanation

Joint contractures in systemic sclerosis primarily result from the progressive fibrosis, thickening, and tightening of the skin and periarticular soft tissues. This contrasts with rheumatoid arthritis, where primary synovial pannus drives joint destruction.

Question 4394

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the Musculoskeletal Infection Society (MSIS) criteria, a diagnosis of "culture-negative" periprosthetic joint infection can be established definitively if which of the following is present?

. Elevated serum CRP and ESR without other criteria
. The presence of a sinus tract communicating with the joint
. Positive sonication fluid culture of an adjacent joint
. Patient report of fevers and chills
. Elevated serum white blood cell count

Correct Answer & Explanation

. The presence of a sinus tract communicating with the joint

Explanation

A communicating sinus tract is a definitive major criterion for PJI. Its presence alone confirms the diagnosis, establishing a "culture-negative" PJI even if intraoperative cultures fail to grow an organism.

Question 4395

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with long-standing diabetes and documented loss of protective sensation via monofilament testing develops a warm, swollen, and erythematous foot without an open wound. Radiographs show early fragmentation of the tarsometatarsal joints. According to the neurovascular theory of this condition's pathogenesis, which of the following physiologic changes is the primary driver of bone resorption?

. Decreased peripheral blood flow leading to avascular necrosis
. Autonomic neuropathy causing arteriovenous shunting and hyperemia
. Repetitive microtrauma from an insensate extremity
. Direct bacterial invasion of the midfoot joints
. Glycosylation of collagen within the joint capsule

Correct Answer & Explanation

. Autonomic neuropathy causing arteriovenous shunting and hyperemia

Explanation

Correct Answer: Autonomic neuropathy causing arteriovenous shunting and hyperemiaThe condition described is acute neuropathic (Charcot) arthropathy. There are two primary theories for its pathogenesis. The neurovascular theory (French theory) posits that autonomic neuropathy leads to a loss of sympathetic tone, resulting in arteriovenous shunting, increased local blood flow (hyperemia), and subsequent active bone resorption (osteopenia), making the bone susceptible to fracture. The neurotraumatic theory (German theory) suggests that repetitive microtrauma in an insensate foot leads to joint destruction.

Question 4396

Topic: 3. Adult Reconstruction (Hip & Knee)

A 25-year-old male presents with recurrent transverse femur fractures. He exhibits short stature, prominent eyes, delayed closure of cranial sutures, and acro-osteolysis of the distal phalanges. Deficiency of which enzyme is the root cause?

. Alkaline phosphatase
. Cathepsin K
. Glucocerebrosidase
. Carbonic anhydrase II
. Tissue-nonspecific alkaline phosphatase

Correct Answer & Explanation

. Cathepsin K

Explanation

Pycnodysostosis is an autosomal recessive lysosomal storage disease caused by Cathepsin K deficiency. Key features include osteosclerosis, acro-osteolysis, delayed suture closure, and brittle bones.

Question 4397

Topic: 3. Adult Reconstruction (Hip & Knee)

A 30-year-old man presents with a femur fracture after a minor fall. He has short stature, prominent eyes, an obtuse mandibular angle, and acro-osteolysis of the distal phalanges. Radiographs show generalized osteosclerosis. What is the underlying enzyme deficiency?

. Alkaline phosphatase
. Cathepsin K
. Glucocerebrosidase
. Arylsulfatase B
. Alpha-L-iduronidase

Correct Answer & Explanation

. Cathepsin K

Explanation

Pycnodysostosis is an autosomal recessive lysosomal storage disease caused by a deficiency in Cathepsin K. This enzyme is crucial for osteoclast-mediated degradation of type I collagen, resulting in osteosclerosis and characteristic acro-osteolysis.

Question 4398

Topic: 3. Adult Reconstruction (Hip & Knee)

A 12-year-old male with short stature presents with a clavicle fracture after a minor fall. Examination reveals open cranial sutures, a prominent forehead, and short, broad hands. Radiographs display generalized osteosclerosis and distinct acro-osteolysis of the distal phalanges. What is the most likely enzymatic defect?

. Alkaline phosphatase
. Carbonic anhydrase II
. Lysyl oxidase
. Alpha-L-iduronidase
. Cathepsin K

Correct Answer & Explanation

. Cathepsin K

Explanation

Pycnodysostosis is a lysosomal storage disease of the bone caused by a deficiency in Cathepsin K, which osteoclasts need to degrade type I collagen. It causes osteosclerosis, delayed suture closure, and pathognomonic acro-osteolysis of the distal phalanges.

Question 4399

Topic: 3. Adult Reconstruction (Hip & Knee)

A 15-year-old male with recurrent fractures presents with short stature, a prominent forehead, delayed cranial suture closure, and acro-osteolysis of the distal phalanges. Radiographs reveal generalized osteosclerosis. This condition is caused by a mutation affecting which of the following?

. Cathepsin K
. Type I Collagen
. CBFA1
. TCIRG1
. GNAS1

Correct Answer & Explanation

. Cathepsin K

Explanation

This is pycnodysostosis, an autosomal recessive lysosomal storage disease caused by a mutation in Cathepsin K. Key features distinguishing it from osteopetrosis include delayed suture closure, normal medullary canals, and acro-osteolysis.

Question 4400

Topic: Total Hip Arthroplasty (THA)

In an irreducible posterior elbow dislocation due to entrapment of the medial epicondyle, what is the MOST appropriate surgical approach to retrieve the entrapped structure and reduce the elbow?

. Posterior approach with olecranon osteotomy.
. Lateral approach (Kocher interval).
. Anterior approach to decompress neurovascular structures.
. Medial approach through the interval between the triceps and brachialis.
. Transarticular external fixator application.

Correct Answer & Explanation

. Medial approach through the interval between the triceps and brachialis.

Explanation

When the medial epicondyle is entrapped, it typically implies that the joint has dislocated laterally. To retrieve the entrapped medial epicondyle and reduce the elbow, a medial approach (Option D) is the most appropriate. This allows direct visualization and retrieval of the entrapped epicondyle. Posterior (Option A) or lateral (Option B) approaches would not provide direct access. An anterior approach (Option C) is for neurovascular decompression, not for retrieving an entrapped epicondyle. External fixator (Option E) is a stabilization method, not for reduction of an entrapped structure.

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