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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 108 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 2141

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with a painful total knee arthroplasty. A joint aspirate is grossly bloody. Which of the following rapid synovial fluid tests for periprosthetic joint infection is most likely to be unreliable or uninterpretable due to the presence of significant erythrocytes?

. Alpha-defensin immunoassay
. Leukocyte esterase colorimetric strip
. Synovial C-reactive protein (CRP)
. Synovial D-dimer
. Synovial fluid calprotectin

Correct Answer & Explanation

. Leukocyte esterase colorimetric strip

Explanation

The leukocyte esterase test utilizes a colorimetric strip that can be difficult to interpret or yield false results when obscured by grossly bloody synovial fluid. Centrifugation may help, but heavy hemolysis still severely limits visual interpretation.

Question 2142

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male undergoes revision reverse total shoulder arthroplasty for presumed aseptic loosening. On postoperative day 11, routine cultures grow Cutibacterium acnes. Which of the following best characterizes the typical histologic finding of the periprosthetic tissue in a C. acnes joint infection?

. Extensive neutrophil infiltration with >10 PMNs per high-power field
. Granulomatous inflammation with caseating necrosis
. A lack of acute inflammatory cells with a predominantly chronic mononuclear infiltrate
. Abundant eosinophilic infiltrate suggestive of an allergic response
. Birefringent particulate wear debris surrounded by foreign body giant cells

Correct Answer & Explanation

. A lack of acute inflammatory cells with a predominantly chronic mononuclear infiltrate

Explanation

Cutibacterium acnes PJI typically presents with a lack of acute inflammatory cells (neutrophils) on histology, instead showing a chronic mononuclear infiltrate or normal-appearing tissue. This makes traditional histological PMN criteria for PJI unreliable for diagnosing C. acnes.

Question 2143

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female presents with acute onset knee pain and swelling 14 days after an uncomplicated primary total knee arthroplasty. Aspiration yields 65,000 WBCs/mcL with 95% neutrophils. Which of the following is an absolute contraindication to performing a Debridement, Antibiotics, and Implant Retention (DAIR) procedure with polyethylene exchange?

. Symptoms presenting 3 weeks after the index procedure
. A well-fixed, cementless tibial component
. A sinus tract communicating with the joint space
. Growth of a methicillin-resistant organism
. Age greater than 60 years

Correct Answer & Explanation

. A sinus tract communicating with the joint space

Explanation

The presence of a sinus tract communicating with the prosthesis is an absolute contraindication to a DAIR procedure, as it represents a chronic infection with established mature biofilm. In such cases, component removal via a single- or two-stage exchange is required.

Question 2144

Topic: Total Hip Arthroplasty (THA)

A 62-year-old female with a total hip arthroplasty utilizing a large diameter cobalt-chromium head on a titanium stem presents with thigh pain. MRI with MARS reveals a large cystic mass adjacent to the hip. What biomechanical factor most increases the risk of mechanically assisted crevice corrosion (MACC) at the head-neck junction?

. Use of a ceramic femoral head
. Decreased femoral head diameter
. Increased femoral offset via a longer head-neck taper
. A fully porous-coated titanium stem
. A high clearance between the head and polyethylene liner

Correct Answer & Explanation

. Increased femoral offset via a longer head-neck taper

Explanation

Mechanically assisted crevice corrosion (trunnionosis) is exacerbated by increased bending moments at the head-neck junction. This increased stress typically occurs with increased femoral offset (longer head-neck tapers) and the use of larger diameter metal heads.

Question 2145

Topic: 3. Adult Reconstruction (Hip & Knee)

During a two-stage exchange for a chronic TKA periprosthetic joint infection, the surgeon notes massive femoral bone loss, severe collateral ligament insufficiency, and a deficient extensor mechanism. Which of the following is the most appropriate management regarding the antibiotic spacer?

. Placement of a static antibiotic-loaded PMMA spacer
. Placement of an articulating antibiotic-loaded PMMA spacer
. Immediate single-stage revision TKA with rotating hinge
. Debridement and isolated intravenous antibiotics for 6 weeks followed by delayed spacer
. Arthrodesis using a modular titanium intramedullary nail

Correct Answer & Explanation

. Placement of a static antibiotic-loaded PMMA spacer

Explanation

A static spacer is indicated in the setting of massive bone loss, severe collateral ligament incompetence, or a deficient extensor mechanism. An articulating spacer in this scenario risks dislocation, extensor mechanism damage, and further bone loss in a highly unstable joint.

Question 2146

Topic: 3. Adult Reconstruction (Hip & Knee)

In revision total knee arthroplasty, isolated distal femoral augmentation is utilized to lower the joint line. What is the expected biomechanical effect of lowering the joint line on the flexion and extension gaps?

. Tightens the flexion gap and loosens the extension gap
. Tightens the extension gap without affecting the flexion gap
. Loosens both the flexion and extension gaps equally
. Tightens both the flexion and extension gaps equally
. Tightens the flexion gap and tightens the extension gap

Correct Answer & Explanation

. Tightens the extension gap without affecting the flexion gap

Explanation

Distal femoral augmentation adds material to the distal aspect of the femur, which directly tightens the extension gap. Because it does not alter the geometry of the posterior femoral condyles, it does not significantly affect the flexion gap.

Question 2147

Topic: 3. Adult Reconstruction (Hip & Knee)
A 74-year-old female requires an acetabular revision for aseptic loosening. Radiographs demonstrate superior migration of the component >3 cm, a broken Kohler's line, and severe ischial osteolysis, representing a Paprosky Type IIIB defect. Which of the following reconstructive options is most appropriate?
. Hemispherical multi-hole jumbo cup with cancellous allograft
. Cup-cage construct or custom triflange acetabular component
. Cemented polyethylene liner into the existing stable fibrous membrane
. Impaction bone grafting with a standard cementless cup
. Bipolar hemiarthroplasty articulating with the native pelvis

Correct Answer & Explanation

. Cup-cage construct or custom triflange acetabular component

Explanation

A Paprosky IIIB defect involves massive bone loss with pelvic discontinuity or severe structural compromise of the anterior and posterior columns. A cup-cage construct or custom triflange component is required to provide immediate rigid fixation and span the discontinuity.

Question 2148

Topic: 3. Adult Reconstruction (Hip & Knee)

Highly cross-linked polyethylene (HXLPE) is widely used in total hip arthroplasty to reduce wear. After irradiation to create cross-links, the polyethylene is often subjected to either melting or annealing. Which of the following best describes the effect of remelting compared to annealing?

. It eliminates free radicals but decreases fatigue strength.
. It preserves fatigue strength but leaves residual free radicals.
. It increases ultimate tensile strength and elongation to failure.
. It increases the oxidation rate in vivo.
. It decreases the volumetric wear rate compared to non-crosslinked polyethylene but increases linear wear.

Correct Answer & Explanation

. It eliminates free radicals but decreases fatigue strength.

Explanation

Remelting polyethylene above its melting point eliminates free radicals, virtually stopping oxidation. However, it decreases crystallinity, which reduces yield strength and fatigue strength compared to annealing.

Question 2149

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with acute knee swelling and pain 4 weeks after a primary total knee arthroplasty. A joint aspiration is performed to rule out periprosthetic joint infection (PJI). According to current consensus guidelines, what synovial fluid white blood cell (WBC) count threshold is most suggestive of an acute PJI in this post-operative timeframe?

. > 1,500 cells/µL
. > 3,000 cells/µL
. > 10,000 cells/µL
. > 27,000 cells/µL
. > 50,000 cells/µL

Correct Answer & Explanation

. > 10,000 cells/µL

Explanation

In the acute post-operative period (typically defined as < 6 weeks), the normal inflammatory response causes elevated cell counts. The accepted synovial WBC threshold for diagnosing acute PJI is > 10,000 cells/µL, compared to > 3,000 cells/µL for chronic PJI.

Question 2150

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male develops an acute hematogenous periprosthetic joint infection of his total hip arthroplasty. He is considered for a debridement, antibiotics, and implant retention (DAIR) procedure. Which of the following factors is incorporated in the KLIC score and is most predictive of DAIR failure?

. Absence of an exchanging modular head
. Preoperative CRP greater than 115 mg/L
. Polymicrobial infection
. Body mass index greater than 35
. Duration of symptoms less than 7 days

Correct Answer & Explanation

. Preoperative CRP greater than 115 mg/L

Explanation

The KLIC score predicts DAIR failure in early PJI. Its components include Kidney disease, Liver cirrhosis, Index surgery type (revision vs primary), Cemented prosthesis, and CRP > 115 mg/L.

Question 2151

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, trial components are inserted. The knee demonstrates appropriate mediolateral stability but is found to be tight in extension and loose in flexion. Which of the following surgical adjustments is the best definitive option to balance this knee?

. Decrease the size of the femoral component
. Recut the distal femur to remove more bone
. Release the posterior cruciate ligament
. Insert a thicker polyethylene insert
. Translate the femoral component anteriorly

Correct Answer & Explanation

. Recut the distal femur to remove more bone

Explanation

A tight extension gap with a loose flexion gap indicates the distal femoral cut is insufficient relative to the posterior cut. Removing more distal femur will open the extension gap without affecting the flexion gap.

Question 2152

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old male with a conventional metal-on-polyethylene total hip arthroplasty presents with unexplained groin pain. Workup reveals an adverse local tissue reaction (ALTR) due to mechanically assisted crevice corrosion (MACC) at the head-neck junction. Which combination of implant characteristics confers the highest risk for this complication?

. Small diameter femoral head on a 12/14 trunnion
. Ceramic femoral head on a titanium stem
. Large diameter cobalt-chrome head on a high-offset titanium stem
. Small diameter cobalt-chrome head on a standard-offset titanium stem
. Large diameter ceramic head on a cobalt-chrome stem

Correct Answer & Explanation

. Large diameter cobalt-chrome head on a high-offset titanium stem

Explanation

Mechanically assisted crevice corrosion (trunnionosis) is driven by increased fretting and micromotion. The highest risk occurs with a large, heavy cobalt-chrome head on a high-offset titanium stem, which maximizes torsional forces at the taper junction.

Question 2153

Topic: 3. Adult Reconstruction (Hip & Knee)
A patient undergoes revision total hip arthroplasty for a painful metal-on-metal bearing. Intraoperatively, extensive soft tissue necrosis and a large cystic mass are noted. Histological examination of the periprosthetic tissue demonstrates an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). This finding is characteristic of which type of immune response?
. Type I anaphylactic reaction
. Type II cytotoxic hypersensitivity
. Type III immune complex reaction
. Type IV delayed-type hypersensitivity
. Innate macrophage-mediated foreign body reaction

Correct Answer & Explanation

. Type IV delayed-type hypersensitivity

Explanation

ALVAL is characterized by perivascular lymphocytic infiltration, indicative of a Type IV delayed-type hypersensitivity response to metal wear debris, specifically cobalt and chromium ions.

Question 2154

Topic: 3. Adult Reconstruction (Hip & Knee)

Fluoroscopic kinematic analysis of a patient with a posterior cruciate-retaining (CR) total knee arthroplasty demonstrates paradoxical anterior sliding of the femur on the tibia during deep flexion. This kinematic abnormality is most strongly associated with which of the following?

. Excessive posterior tibial slope
. Insufficient posterior tibial slope
. Oversized femoral component
. Over-released medial collateral ligament
. Patella baja

Correct Answer & Explanation

. Insufficient posterior tibial slope

Explanation

In a CR TKA, an insufficient posterior tibial slope (or a tight PCL) can restrict normal posterior femoral rollback. This kinematic mismatch leads to paradoxical anterior translation of the femur on the tibia during flexion.

Question 2155

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with a Candida albicans periprosthetic joint infection of his total knee arthroplasty. If the surgeon plans a two-stage exchange using an antimicrobial-loaded spacer, which of the following antifungal agents is heat-stable and most appropriate for incorporation into the PMMA?

. Micafungin
. Caspofungin
. Amphotericin B
. Fluconazole
. Terbinafine

Correct Answer & Explanation

. Amphotericin B

Explanation

Amphotericin B and voriconazole are heat-stable and can be safely incorporated into PMMA cement for local elution in fungal PJI. Echinocandins and many azoles degrade during the exothermic polymerization process.

Question 2156

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old female undergoes joint aspiration for a suspected PJI, showing elevated synovial WBC counts, but multiple cultures are negative at 14 days. Which of the following diagnostic technologies detects microbial cell-free DNA directly from the synovial fluid and is best utilized in this culture-negative scenario?

. Alpha-defensin immunoassay
. Leukocyte esterase colorimetric strip
. Synovial fluid CRP
. Metagenomic next-generation sequencing (mNGS)
. Matrix-assisted laser desorption/ionization (MALDI-TOF)

Correct Answer & Explanation

. Metagenomic next-generation sequencing (mNGS)

Explanation

Metagenomic next-generation sequencing (mNGS) detects microbial cell-free DNA directly from synovial fluid, offering high sensitivity for identifying pathogens in culture-negative PJI. MALDI-TOF requires a positive culture to identify the grown organism.

Question 2157

Topic: 3. Adult Reconstruction (Hip & Knee)

A diabetic patient presents for a primary total hip arthroplasty. Her Hemoglobin A1c is 8.5%. The surgery is delayed for optimization. Which of the following laboratory markers best reflects her glycemic control over the preceding 2 to 3 weeks and is most useful to confirm recent improvement?

. Fasting blood glucose
. Hemoglobin A1c
. Fructosamine
. C-peptide
. Glycated albumin

Correct Answer & Explanation

. Fructosamine

Explanation

Fructosamine reflects glycemic control over the preceding 2 to 3 weeks, making it highly useful for assessing short-term preoperative optimization in diabetic patients. Hemoglobin A1c reflects longer-term control over 2 to 3 months.

Question 2158

Topic: 3. Adult Reconstruction (Hip & Knee)

During a revision total knee arthroplasty for suspected PJI, the explanted components are sent for sonication. What is the primary mechanism by which sonication improves the yield of microbiological cultures?

. Denaturation of bacterial DNA
. Lysis of human leukocytes
. Disruption of extracellular polymeric substance (biofilm)
. Neutralization of systemic antibiotics
. Enhancement of bacterial replication rates

Correct Answer & Explanation

. Disruption of extracellular polymeric substance (biofilm)

Explanation

Sonication uses low-frequency acoustic waves to disrupt the extracellular polymeric substance of the biofilm. This dislodges persister cells and planktonic bacteria from explanted hardware, significantly improving culture yield.

Question 2159

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male presents with acute hematogenous PJI of a total hip arthroplasty. Which of the following is considered an absolute contraindication to attempting a Debridement, Antibiotics, and Implant Retention (DAIR) procedure?

. Symptom duration of 10 days
. A well-fixed uncemented stem
. A loose femoral component
. Infection with methicillin-resistant Staphylococcus aureus (MRSA)
. Serum CRP > 100 mg/L

Correct Answer & Explanation

. A loose femoral component

Explanation

A loose implant is an absolute contraindication for a DAIR procedure because the infection cannot be cleared from the unstable interface. Successful DAIR requires well-fixed components and ideally a short symptom duration.

Question 2160

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents with a loose cemented total hip arthroplasty and massive proximal osteolysis. Radiographs reveal absence of the medial calcar and extensive metaphyseal bone loss, with only 3 cm of intact diaphyseal bone at the isthmus. What is the most appropriate femoral component choice for revision?

. Standard porous-coated metaphyseal fitting stem
. Fully porous-coated cylindrical stem
. Modular fluted tapered stem
. Standard length cemented stem with impaction bone grafting
. Uncemented proximally coated wedge-tapered stem

Correct Answer & Explanation

. Modular fluted tapered stem

Explanation

This describes a Paprosky 3B femoral defect, characterized by extensive metaphyseal and diaphyseal bone loss with less than 4 cm of intact diaphyseal isthmus. A modular fluted tapered stem relies on rigid distal diaphyseal fixation, making it the optimal choice.

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