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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 219 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 4361

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male presents with chronic knee pain and a draining sinus tract 2 years after a total knee arthroplasty.

According to the Musculoskeletal Infection Society (MSIS) criteria, what is the next most appropriate step in diagnosing a periprosthetic joint infection (PJI)?

. Perform a joint aspiration for cell count and culture
. Order serum inflammatory markers (ESR and CRP)
. No further testing is required to confirm the diagnosis of PJI
. Obtain an intraoperative frozen section to assess for neutrophils
. Order a synovial alpha-defensin immunoassay

Correct Answer & Explanation

. No further testing is required to confirm the diagnosis of PJI

Explanation

According to MSIS criteria, the presence of a sinus tract communicating with the prosthesis is a major criterion and is considered definitive evidence of a PJI. No further diagnostic testing is required to establish the diagnosis.

Question 4362

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female with a well-functioning total hip arthroplasty (THA) placed 5 years ago develops sudden onset severe hip pain and fevers starting 5 days ago following a dental procedure. Radiographs show well-fixed components. What is the most appropriate management?

. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange
. One-stage component exchange
. Two-stage component exchange with an antibiotic spacer
. Long-term oral suppressive antibiotics alone
. Aspiration and 6 weeks of intravenous antibiotics without surgery

Correct Answer & Explanation

. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange

Explanation

DAIR is indicated for acute hematogenous PJI (symptoms <3-4 weeks) or acute postoperative PJI (within 4 weeks of index surgery) in patients with well-fixed implants and stable soft tissues. The modular components (e.g., polyethylene liner) must be exchanged during the procedure.

Question 4363

Topic: 3. Adult Reconstruction (Hip & Knee)

The synovial fluid alpha-defensin test is increasingly utilized in the diagnosis of periprosthetic joint infections. Which of the following cells is the primary source of alpha-defensin in the synovial fluid?

. Macrophages
. Synoviocytes
. Neutrophils
. T-lymphocytes
. Osteoblasts

Correct Answer & Explanation

. Neutrophils

Explanation

Alpha-defensin is an antimicrobial peptide released by activated neutrophils in response to infection. It is highly sensitive and specific for diagnosing PJI, even in the setting of concurrent antibiotic administration.

Question 4364

Topic: 3. Adult Reconstruction (Hip & Knee)

A 50-year-old female with known systemic sclerosis complains of progressive shortening and pain in her fingertips. Radiographs reveal significant resorption of the distal phalangeal tufts (acro-osteolysis). What is the primary underlying pathophysiology driving this skeletal finding?

. Primary osteoclastic overactivity due to hyperparathyroidism
. Invasion of the bone by synovial pannus
. Chronic digital ischemia secondary to microangiopathy
. Repetitive microtrauma from sensory neuropathy
. Ectopic deposition of calcium hydroxyapatite within the bone marrow

Correct Answer & Explanation

. Chronic digital ischemia secondary to microangiopathy

Explanation

Acro-osteolysis in systemic sclerosis is caused by chronic ischemia resulting from severe digital microangiopathy and Raynaud's phenomenon. The lack of blood flow leads to resorption of the distal phalangeal tufts.

Question 4365

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male is undergoing revision of a reverse total shoulder arthroplasty due to suspected indolent infection. Intraoperative cultures are sent. To maximize the yield for detecting Cutibacterium (Propionibacterium) acnes, how long should the microbiology laboratory hold the cultures?

. 3 to 5 days
. 7 to 10 days
. 14 to 21 days
. 28 to 35 days
. 48 to 72 hours

Correct Answer & Explanation

. 14 to 21 days

Explanation

Cutibacterium acnes is a slow-growing, Gram-positive anaerobic bacillus frequently implicated in shoulder PJI. Cultures must be held for 14 to 21 days to ensure accurate detection.

Question 4366

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a history of MRSA PJI of the knee is currently 6 weeks status-post first-stage resection and placement of an articulating antibiotic spacer. They have completed a 6-week course of IV antibiotics. What is the most reliable method to confirm eradication of infection prior to proceeding with the second-stage reimplantation?

. Normalization of serum ESR and CRP
. Aspiration of the joint space for synovial fluid cell count and culture
. Intraoperative frozen section showing less than 5 neutrophils per high-power field
. A negative 99mTc bone scan
. There is no single highly reliable test to definitively confirm eradication

Correct Answer & Explanation

. There is no single highly reliable test to definitively confirm eradication

Explanation

Diagnosing the eradication of infection between stages of a two-stage exchange remains challenging, and there is no single highly reliable test. Surgeons typically use a combination of declining inflammatory markers, clinical appearance, and joint aspiration, though all have high false-negative or false-positive rates in this specific setting.

Question 4367

Topic: 3. Adult Reconstruction (Hip & Knee)

A 82-year-old male with severe heart failure and a well-fixed total knee arthroplasty develops a coagulase-negative Staphylococcus PJI. Due to his prohibitive surgical risk, chronic suppressive oral antibiotic therapy is chosen. Which of the following is a strict prerequisite for the success of this treatment modality?

. The infecting organism must be highly virulent
. The prosthesis must be mechanically well-fixed
. The patient must first complete a two-stage exchange
. The suppressive antibiotic must be bactericidal and administered intravenously
. The presence of a chronic draining sinus tract

Correct Answer & Explanation

. The prosthesis must be mechanically well-fixed

Explanation

For chronic suppressive antibiotic therapy to be a viable option, the implant must be well-fixed, the organism must be of low virulence and susceptible to oral antibiotics, and the patient must be able to tolerate the medication. A draining sinus tract is a relative contraindication.

Question 4368

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female with a long-standing history of severe Rheumatoid Arthritis (RA) presents with acute knee pain 3 years after a total knee arthroplasty. Her baseline serum ESR and CRP are chronically elevated due to her RA. Which synovial fluid marker is the most accurate diagnostic tool for distinguishing PJI from an acute RA flare?

. Alpha-defensin
. Synovial fluid leukocyte esterase
. Synovial fluid white blood cell (WBC) count
. Synovial fluid polymorphonuclear (PMN) percentage
. Gram stain

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin maintains highly accurate sensitivity and specificity for diagnosing PJI even in the setting of systemic inflammatory diseases like rheumatoid arthritis, whereas synovial WBC counts and serum inflammatory markers may be falsely elevated by the underlying disease.

Question 4369

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the updated 2018 Evidence-Based Definition of Periprosthetic Joint Infection, which of the following combinations satisfies the criteria for definitively diagnosing a PJI?

. One positive synovial fluid culture and elevated serum CRP
. Elevated synovial WBC count and positive leukocyte esterase
. Two positive periprosthetic cultures yielding the exact same organism
. Purulence in the joint without positive cultures
. Elevated serum D-dimer and ESR

Correct Answer & Explanation

. Two positive periprosthetic cultures yielding the exact same organism

Explanation

The isolation of the exact same organism from two separate periprosthetic tissue or fluid cultures is a major criterion and definitively establishes the diagnosis of PJI.

Question 4370

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with long-standing systemic sclerosis presents with severe, fixed flexion contractures of the PIP joints. Non-operative management has failed.

If surgery is deemed absolutely necessary despite the high risks, what is the preferred surgical procedure to provide stable, pain-free digits?

. Volar plate arthroplasty
. Arthrodesis of the PIP joints in a functional position
. Extensive soft tissue release and Z-plasty of the skin
. Silicone implant arthroplasty
. Flexor digitorum superficialis to profundus tendon transfer

Correct Answer & Explanation

. Arthrodesis of the PIP joints in a functional position

Explanation

In systemic sclerosis, PIP joint contractures are driven by the unyielding, fibrotic skin envelope rather than primary articular disease. Soft tissue releases and arthroplasties have high failure rates; therefore, PIP joint arthrodesis in a functional position is the most reliable surgical option if conservative care fails.

Question 4371

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old man presents with a painful total knee arthroplasty 3 years post-op. Serum CRP is 15 mg/L and ESR is 45 mm/hr. Joint aspiration yields a WBC count of 2,800 cells/uL with 75% PMNs. Which of the following synovial fluid biomarkers provides the highest specificity for diagnosing a periprosthetic joint infection?

. Interleukin-6
. Alpha-defensin
. Leukocyte esterase
. C-reactive protein
. Procalcitonin

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin is an antimicrobial peptide released by neutrophils that has demonstrated >95% specificity and sensitivity for diagnosing PJI. It outperforms other markers in equivocal cases and is now a key minor criterion in modern diagnostic algorithms.

Question 4372

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents 3 weeks after a primary total hip arthroplasty with acute onset of hip pain, erythema, and a draining sinus tract. Radiographs show well-fixed components. What is the most appropriate surgical management?

. 1-stage revision
. 2-stage revision with articulating spacer
. Debridement, antibiotics, and implant retention (DAIR) with modular exchange
. Suppressive oral antibiotics
. Girdlestone resection arthroplasty

Correct Answer & Explanation

. Debridement, antibiotics, and implant retention (DAIR) with modular exchange

Explanation

DAIR is indicated for acute postoperative infections (within 4 weeks of surgery) with well-fixed implants and an intact soft-tissue envelope. Modular components should be exchanged to disrupt forming biofilms and allow thorough joint washout.

Question 4373

Topic: 3. Adult Reconstruction (Hip & Knee)

A 50-year-old female with systemic sclerosis presents with progressive shortening of her distal fingers and painful, chalky subcutaneous nodules. Radiographs demonstrate resorption of the distal phalangeal tufts. What autoantibody is most commonly associated with her localized disease variant?

. Anti-Scl-70
. Anti-dsDNA
. Anti-centromere
. Anti-Ro (SSA)
. Rheumatoid factor

Correct Answer & Explanation

. Anti-centromere

Explanation

Anti-centromere antibodies are strongly associated with limited cutaneous systemic sclerosis (CREST syndrome), which classically presents with calcinosis cutis and acro-osteolysis. Anti-Scl-70 is associated with diffuse systemic sclerosis and a higher risk of interstitial lung disease.

Question 4374

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the Musculoskeletal Infection Society (MSIS) criteria, which of the following is considered a major (definitive) criterion for diagnosing a periprosthetic joint infection?

. Elevated serum CRP and ESR
. Purulence in the affected joint
. A single positive culture of synovial fluid
. A communicating sinus tract to the prosthesis
. Elevated synovial fluid leukocyte esterase

Correct Answer & Explanation

. A communicating sinus tract to the prosthesis

Explanation

The major criteria for PJI are either a sinus tract communicating with the prosthesis or the isolation of identical pathogens from at least two separate tissue or fluid samples. All other listed options represent minor criteria.

Question 4375

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old woman with a 15-year history of diffuse systemic sclerosis requires a total knee arthroplasty for severe secondary osteoarthritis. Which of the following perioperative complications is she at significantly higher risk for compared to the general population?

. Heterotopic ossification
. Aseptic loosening
. Wound necrosis and delayed healing
. Periprosthetic fracture
. Metal hypersensitivity

Correct Answer & Explanation

. Wound necrosis and delayed healing

Explanation

Systemic sclerosis is characterized by microvascular obliteration and dense dermal collagen deposition. This compromises local skin perfusion, leading to a markedly increased risk of wound dehiscence and necrosis following surgical incisions.

Question 4376

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male is 8 weeks out from the first stage of a 2-stage revision for a total hip PJI. His spacer is in place, and he has completed 6 weeks of IV antibiotics. His ESR and CRP have normalized, and his hip is clinically benign. What is the most appropriate next step?

. Proceed immediately to the second stage reimplantation
. Obtain a hip aspiration and proceed to second stage if culture is negative at 48 hours
. Wait an additional 2-4 weeks off antibiotics before checking inflammatory markers and considering reimplantation
. Prescribe lifelong suppressive oral antibiotics without reimplantation
. Exchange the current spacer for a new antibiotic spacer

Correct Answer & Explanation

. Wait an additional 2-4 weeks off antibiotics before checking inflammatory markers and considering reimplantation

Explanation

Following completion of IV antibiotics during a 2-stage revision, an "antibiotic holiday" of at least 2 to 4 weeks is recommended. This allows for clinical observation and re-evaluation of inflammatory markers to ensure the infection remains suppressed off therapy prior to reimplantation.

Question 4377

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 diagnosing a periprosthetic joint infection?

. Elevated serum CRP > 10 mg/L
. Synovial fluid WBC > 3,000 cells/µL
. A single positive intraoperative tissue culture
. A sinus tract communicating with the prosthesis
. Positive synovial fluid leukocyte esterase

Correct Answer & Explanation

. A sinus tract communicating with the prosthesis

Explanation

A sinus tract communicating with the prosthesis or two positive periprosthetic cultures with phenotypically identical organisms are the only major criteria for PJI. The others represent minor criteria.

Question 4378

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following scenarios is the most appropriate indication for Debridement, Antibiotics, and Implant Retention (DAIR) in the setting of periprosthetic joint infection?

. A sinus tract present for 2 weeks in a 1-year-old TKA
. A 3-week post-operative THA infection with a well-fixed stem and exchangeable head/liner
. A 6-month post-operative THA with a newly identified Cutibacterium acnes infection
. An acute hematogenous infection with symptoms for 6 weeks
. A well-fixed TKA with radiographic evidence of osteolysis and acute pain

Correct Answer & Explanation

. A 3-week post-operative THA infection with a well-fixed stem and exchangeable head/liner

Explanation

DAIR is most successful for acute postoperative infections (<4 weeks from index surgery) or acute hematogenous infections (<3 weeks of symptoms) with well-fixed implants and exchangeable modular parts. A sinus tract is a contraindication to DAIR.

Question 4379

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) criteria for periprosthetic joint infection, which of the following serum markers is heavily weighted as a minor criterion alongside C-reactive protein (CRP)?

. Serum D-dimer
. Serum procalcitonin
. Serum interleukin-6 (IL-6)
. Serum tumor necrosis factor-alpha (TNF-alpha)
. Serum ferritin

Correct Answer & Explanation

. Serum D-dimer

Explanation

The 2018 ICM criteria introduced serum D-dimer as a minor criterion for PJI diagnosis. It is weighted with 2 points, equivalent to an elevated CRP, making it a highly useful adjunct in the diagnostic workup.

Question 4380

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male presents with acute onset of severe right knee pain and swelling 3 weeks after a dental procedure. He underwent a right total knee arthroplasty 5 years ago. Aspiration yields 65,000 WBCs/uL with 95% neutrophils.

What is the most appropriate surgical management?

. One-stage revision arthroplasty
. Two-stage revision arthroplasty with an antibiotic spacer
. DAIR (Debridement, antibiotics, and implant retention) with polyethylene exchange
. Suppressive oral antibiotic therapy
. Above-knee amputation

Correct Answer & Explanation

. DAIR (Debridement, antibiotics, and implant retention) with polyethylene exchange

Explanation

Acute hematogenous PJI (symptoms lasting less than 3-4 weeks) in a well-fixed prosthesis is best managed with DAIR and modular component exchange. This strategy provides a high likelihood of eradicating the infection while preserving the well-fixed implants.

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