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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 300 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 5981

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, trial components are placed. The surgeon notes that the knee is excessively tight in both full extension and 90 degrees of flexion. The patella tracks centrally but requires significant force to evert. What is the most appropriate next step in balancing this knee?

. Recut the proximal tibia to resect more bone
. Recut the distal femur to resect more bone
. Downsize the femoral component
. Release the posterior cruciate ligament
. Recut the posterior femoral condyles

Correct Answer & Explanation

. Recut the proximal tibia to resect more bone

Explanation

A knee that is tight in both flexion and extension indicates a symmetrically tight flexion and extension gap. The most appropriate correction is to increase both gaps equally. This is achieved by either resecting more proximal tibia or utilizing a thinner tibial polyethylene insert. Modifying the femur only affects one gap (distal femur affects extension; posterior femur affects flexion).

Question 5982

Topic: Total Hip Arthroplasty (THA)

A 62-year-old woman presents with an audible 'squeaking' sound coming from her total hip arthroplasty during ambulation. Review of the operative report indicates she has a ceramic-on-ceramic bearing. Which of the following component malpositions is most strongly associated with this phenomenon?

. Excessive anteversion and increased inclination of the acetabular cup
. Excessive retroversion of the femoral stem
. Inadequate offset of the femoral stem
. Decreased inclination (vertical orientation) of the acetabular cup
. Varus placement of the femoral stem

Correct Answer & Explanation

. Excessive anteversion and increased inclination of the acetabular cup

Explanation

Squeaking in ceramic-on-ceramic THA is a recognized complication. It is most strongly associated with edge loading of the ceramic bearings. Edge loading typically occurs due to acetabular component malposition, specifically excessive cup inclination (steep cup) and excessive anteversion, or due to impingement leading to microseparation.

Question 5983

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with acute onset of extreme left knee pain, swelling, and fevers over the last 3 days. He underwent an uncomplicated total knee arthroplasty of the left knee 4 years ago. Joint aspiration yields synovial fluid with a WBC count of 75,000 cells/ยตL and 92% neutrophils. The implant is radiographically well-fixed. What is the most appropriate surgical management?

. One-stage exchange arthroplasty
. Two-stage exchange arthroplasty with an antibiotic spacer
. Debridement, antibiotics, and implant retention (DAIR) with modular polyethylene exchange
. Long-term suppressive intravenous antibiotics without surgical intervention
. Knee arthrodesis

Correct Answer & Explanation

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

Explanation

This patient has an acute hematogenous periprosthetic joint infection (PJI), defined as acute onset of symptoms (usually < 3 weeks) in a previously asymptomatic, well-functioning, and well-fixed joint. The standard of care for acute hematogenous PJI is DAIR (Debridement, Antibiotics, and Implant Retention), which includes exchanging the modular polyethylene liner to thoroughly lavage the posterior joint space and reduce the biofilm burden.

Question 5984

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty, the knee is well-balanced and stable in full extension, but the flexion gap is unacceptably tight. Which of the following surgical steps is the most appropriate to increase the flexion gap without altering the extension gap?

. Resect more distal femur
. Use a thinner polyethylene insert
. Downsize the femoral component using a posterior referencing guide
. Release the posterior capsule
. Decrease the posterior slope of the tibial cut

Correct Answer & Explanation

. Downsize the femoral component using a posterior referencing guide

Explanation

A tight flexion gap with a balanced extension gap can be corrected by downsizing the femoral component. When using a posterior referencing system, downsizing the femur removes more posterior condylar bone, effectively increasing the flexion gap without affecting the distal femoral cut (which controls the extension gap). Increasing the posterior tibial slope also selectively increases the flexion gap, but 'decreasing' it would tighten it. A thinner PE insert would undesirably loosen the extension gap.

Question 5985

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the American Academy of Orthopaedic Surgeons (AAOS) guidelines, which of the following is the recommended duration for venous thromboembolism (VTE) prophylaxis following an elective total hip arthroplasty?

. 7 to 10 days
. 10 to 14 days
. Up to 35 days
. 8 weeks minimum
. Only required during the inpatient stay

Correct Answer & Explanation

. Up to 35 days

Explanation

AAOS and ACCP guidelines recommend extended VTE prophylaxis for up to 35 days following major orthopedic surgeries such as total hip arthroplasty (THA), as the risk of VTE remains elevated for several weeks post-operatively.

Question 5986

Topic: Total Hip Arthroplasty (THA)

A 65-year-old patient who underwent a primary total hip arthroplasty using a ceramic-on-ceramic bearing complains of an audible squeaking sound from the hip when walking. Which of the following biomechanical factors is most directly associated with the development of this complication?

. Excessive anteversion of the femoral component
. Edge loading due to acetabular component malposition
. Use of a 28-mm femoral head
. Galvanic corrosion at the trunnion
. Polyethylene oxidation

Correct Answer & Explanation

. Edge loading due to acetabular component malposition

Explanation

Squeaking is a well-known complication specific to ceramic-on-ceramic THA bearings. It is primarily associated with edge loading, which often results from cup malposition (especially excessive abduction or abnormal version), leading to stripe wear on the ceramic head and loss of fluid film lubrication.

Question 5987

Topic: 3. Adult Reconstruction (Hip & Knee)

When evaluating a painful total knee arthroplasty for potential periprosthetic joint infection (PJI), the synovial fluid alpha-defensin immunoassay is often utilized. Which of the following best describes the physiological origin of alpha-defensin in this context?

. It is an exotoxin secreted by Staphylococcus aureus biofilms.
. It is an acute-phase reactant produced by the liver in response to systemic IL-6.
. It is an antimicrobial peptide released by activated neutrophils.
. It is a degradation product of articular cartilage and polyethylene.
. It is a cytokine produced by osteoblasts during osteolysis.

Correct Answer & Explanation

. It is an antimicrobial peptide released by activated neutrophils.

Explanation

Alpha-defensin is a validated biomarker used in the diagnosis of PJI. It is a naturally occurring antimicrobial peptide that is released by host neutrophils into the synovial fluid in response to pathogens. Its levels are highly sensitive and specific for PJI and maintain diagnostic accuracy even in the presence of concurrent antibiotic administration.

Question 5988

Topic: 3. Adult Reconstruction (Hip & Knee)

In the diagnosis of periprosthetic joint infection (PJI), which synovial fluid biomarker has emerged as highly specific by reflecting an antimicrobial peptide released by neutrophils?

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

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin is a biomarker secreted by neutrophils in response to pathogens. It demonstrates exceptional sensitivity and specificity for diagnosing PJI, outperforming traditional synovial fluid markers.

Question 5989

Topic: 3. Adult Reconstruction (Hip & Knee)

In modern total hip arthroplasty, using highly cross-linked polyethylene drastically reduces volumetric wear. However, high-dose irradiation and subsequent thermal remelting to eliminate free radicals results in which mechanical trade-off?

. Increased in vivo oxidation
. Decreased yield strength and fatigue crack propagation resistance
. Increased adhesive wear
. Increased propensity for third-body wear
. Enhanced generation of reactive oxygen species

Correct Answer & Explanation

. Decreased yield strength and fatigue crack propagation resistance

Explanation

While remelting effectively quenches free radicals (reducing oxidation and wear), the thermal process alters the polymer's crystalline structure. This significantly reduces fatigue resistance, ultimate tensile strength, and yield strength.

Question 5990

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old undergoes a total hip arthroplasty. Ten years later, she develops osteolysis secondary to particulate wear debris. What is the predominant macrophage-activating cytokine responsible for initiating this osteolytic cascade?

. Interleukin-10 (IL-10)
. Tumor necrosis factor-alpha (TNF-alpha)
. Transforming growth factor-beta (TGF-beta)
. Osteoprotegerin
. Interferon-gamma

Correct Answer & Explanation

. Tumor necrosis factor-alpha (TNF-alpha)

Explanation

Macrophages phagocytose particulate wear debris and release pro-inflammatory cytokines, most notably TNF-alpha, IL-1, and IL-6. These cytokines stimulate osteoclastic bone resorption, leading to aseptic loosening.

Question 5991

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with recurrent posterior dislocation following a posterior approach Total Hip Arthroplasty (THA). Standing lateral radiographs reveal a flatback deformity with a significantly decreased lumbar lordosis. What is the most likely mechanism contributing to her recurrent instability?

. Increased pelvic tilt and decreased acetabular anteversion in standing position
. Decreased pelvic tilt and increased acetabular anteversion in standing position
. Loss of anterior pelvic tilt during sitting, causing posterior impingement
. Failure of the pelvis to retrovert during sitting, leading to anterior impingement
. Increased spinopelvic mobility leading to hyperlordosis in the seated position

Correct Answer & Explanation

. Failure of the pelvis to retrovert during sitting, leading to anterior impingement

Explanation

Patients with stiff spinopelvic deformity (e.g., flatback syndrome or decreased lumbar lordosis) fail to normally retrovert their pelvis when transitioning from standing to sitting. Because the pelvis does not retrovert, the acetabulum fails to open up anteriorly, leading to anterior impingement of the femoral neck on the acetabulum and subsequent posterior dislocation.

Question 5992

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, the surgeon notes that the knee is tight in flexion but symmetric and perfectly balanced in extension. Which of the following adjustments is most appropriate to balance the knee?

. Release the posterior cruciate ligament (PCL) or increase the posterior femoral slope
. Downsize the tibial polyethylene insert
. Recut the distal femur to remove more bone
. Release the superficial medial collateral ligament (sMCL)
. Translate the femoral component anteriorly

Correct Answer & Explanation

. Release the posterior cruciate ligament (PCL) or increase the posterior femoral slope

Explanation

A knee that is tight in flexion but balanced in extension has a flexion gap that is smaller than the extension gap. To increase the flexion gap without affecting the extension gap, the surgeon can increase the posterior slope of the tibial cut, downsize the femoral component (anterior referencing) or use a thinner femoral component (posterior referencing), or release the PCL. Downsizing the tibial insert would increase both gaps, leading to instability in extension.

Question 5993

Topic: 3. Adult Reconstruction (Hip & Knee)

Ceramic-on-ceramic (CoC) bearing surfaces in Total Hip Arthroplasty are known for excellent wear characteristics. However, they are associated with a unique set of complications. Which of the following is a recognized complication specific to CoC bearings?

. Trunnionosis due to galvanic corrosion
. Stripe wear from edge loading leading to squeaking
. Accelerated osteolysis from massive particulate debris
. Elevated serum cobalt and chromium levels
. Polyethylene oxidation and delamination

Correct Answer & Explanation

. Stripe wear from edge loading leading to squeaking

Explanation

Squeaking is a well-documented complication unique to ceramic-on-ceramic (CoC) bearings. It is often associated with edge loading, stripe wear, component malposition (e.g., extreme anteversion or retroversion), or third-body wear. Trunnionosis and elevated metal ions are associated with metal-on-metal or metal-on-polyethylene (at the head-neck junction).

Question 5994

Topic: 3. Adult Reconstruction (Hip & Knee)
In the cascade of aseptic loosening following a total hip arthroplasty, the primary biological response to ultra-high-molecular-weight polyethylene (UHMWPE) wear debris is initiated by which of the following cell types?
. Osteoblasts
. Osteoclasts
. Macrophages
. T-lymphocytes
. Fibroblasts

Correct Answer & Explanation

. Macrophages

Explanation

The primary effector cells in the biological cascade of particle-induced osteolysis (aseptic loosening) are tissue macrophages. Macrophages phagocytose particulate UHMWPE wear debris (especially particles 0.1 to 1.0 micrometers in size). This triggers the release of pro-inflammatory cytokines such as TNF-alpha, IL-1, and IL-6, which subsequently upregulate RANKL expression, leading to osteoclast activation and bone resorption.

Question 5995

Topic: Total Knee Arthroplasty (TKA)

A surgeon is performing a total knee arthroplasty (TKA). After making the initial bone cuts and inserting trial components, she notes that the knee is tight in extension (with a lack of full extension) but perfectly balanced in 90 degrees of flexion. What is the most appropriate next step to balance the knee?

. Downsize the femoral component
. Increase the posterior slope of the tibial cut
. Resect more bone from the distal femur
. Resect more bone from the proximal tibia
. Release the posterior cruciate ligament (PCL)

Correct Answer & Explanation

. Resect more bone from the distal femur

Explanation

In TKA gap balancing, if the extension gap is tight (knee lacks full extension) but the flexion gap is well-balanced, the appropriate step is to resect more bone from the distal femur. Distal femoral resection increases the extension gap without affecting the flexion gap. Resecting more proximal tibia would erroneously increase both the flexion and extension gaps. Downsizing the femoral component increases the flexion gap.

Question 5996

Topic: 3. Adult Reconstruction (Hip & Knee)
Delamination of ultra-high-molecular-weight polyethylene (UHMWPE) components in total knee arthroplasty is predominantly a consequence of which type of wear mechanism?
. Adhesive wear
. Abrasive wear
. Fatigue wear
. Third-body wear
. Corrosive wear

Correct Answer & Explanation

. Fatigue wear

Explanation

Fatigue wear occurs due to cyclic loading that generates maximum shear stresses slightly below the articulating surface. Over time, these subsurface stresses cause microcracks that propagate and coalesce, eventually leading to gross delamination and pitting of the polyethylene component. This is common in TKA due to non-conforming surface contact stresses.

Question 5997

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following wear mechanisms is primarily responsible for the generation of polyethylene debris in total hip arthroplasty, ultimately leading to osteolysis?

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

Correct Answer & Explanation

. Adhesive wear

Explanation

Adhesive wear occurs when two surfaces slide against each other, forming microscopic welds that subsequently break off to form particulate debris. This is the primary mode of wear generating polyethylene particles in THA, leading to macrophage activation and osteolysis.

Question 5998

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female undergoes a primary total hip arthroplasty via a posterior approach. Six weeks postoperatively, she sustains a posterior dislocation. Which of the following acetabular cup orientations most significantly increases the risk of posterior dislocation?

. Increased anteversion and increased abduction
. Decreased anteversion and decreased abduction
. Increased anteversion and decreased abduction
. Decreased anteversion and increased abduction
. Neutral version and 45 degrees of abduction

Correct Answer & Explanation

. Decreased anteversion and decreased abduction

Explanation

Poster dislocation in THA is strongly associated with acetabular retroversion (decreased anteversion) and inadequate abduction. The safe zone generally targets 15 (+/- 10) degrees of anteversion and 40 (+/- 10) degrees of abduction.

Question 5999

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male presents with a painful total knee arthroplasty 2 years after index surgery. Synovial fluid aspiration reveals a WBC count of 45,000 cells/uL with 92% neutrophils. He is hemodynamically stable with well-fixed implants on radiographs. Which is the most appropriate definitive management?

. Suppressive oral antibiotics
. Arthroscopic irrigation and debridement
. Open irrigation and debridement with polyethylene exchange
. Single-stage revision arthroplasty
. Two-stage revision arthroplasty

Correct Answer & Explanation

. Two-stage revision arthroplasty

Explanation

Chronic periprosthetic joint infections (presenting >4 weeks postoperatively or >3 weeks from symptom onset) with well-fixed components are definitively managed with a two-stage revision arthroplasty. Open irrigation and debridement with poly exchange is reserved for acute infections.

Question 6000

Topic: 3. Adult Reconstruction (Hip & Knee)

The alpha-defensin immunoassay is a highly sensitive and specific diagnostic test for periprosthetic joint infection (PJI). Alpha-defensin is an antimicrobial peptide primarily secreted by which of the following cells?

. Macrophages
. Osteoblasts
. Fibroblasts
. Neutrophils
. T-lymphocytes

Correct Answer & Explanation

. Neutrophils

Explanation

Alpha-defensin is released by activated neutrophils in response to infection. Its presence in synovial fluid serves as an accurate biomarker for PJI, remaining reliable even in the presence of systemic antibiotics.

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