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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 306 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 6101

Topic: 3. Adult Reconstruction (Hip & Knee)

A surgeon performing a posterior-stabilized total knee arthroplasty evaluates the flexion and extension gaps with trial components in place. The extension gap is symmetric and perfectly balanced. The flexion gap is symmetric but significantly tight. What is the most appropriate next step to balance the knee?

. Release the posterior cruciate ligament
. Resect more proximal tibia
. Downsize the femoral component and use a thicker polyethylene insert
. Downsize the femoral component and use the same polyethylene insert
. Release the medial collateral ligament

Correct Answer & Explanation

. Downsize the femoral component and use the same polyethylene insert

Explanation

A tight flexion gap with a balanced extension gap indicates the anteroposterior (AP) dimension of the femoral component is too large. By downsizing the femoral component, more posterior condylar bone is resected, which enlarges the flexion gap without affecting the extension gap. Using the same polyethylene thickness maintains the already balanced extension gap. Releasing the PCL is incorrect because a posterior-stabilized design already sacrifices the PCL. Resecting more tibia would symmetrically enlarge both flexion and extension gaps.

Question 6102

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with recurrent posterior dislocations of her total hip arthroplasty. Radiographs reveal the acetabular cup is placed in 45 degrees of abduction and 5 degrees of anteversion. The femoral stem is in 15 degrees of anteversion. What is the most likely primary cause of her instability?

. Excessive acetabular cup anteversion
. Insufficient acetabular cup anteversion
. Femoral component retroversion
. Excessive acetabular cup abduction
. Abductor mechanism deficiency

Correct Answer & Explanation

. Insufficient acetabular cup anteversion

Explanation

The 'safe zone' for acetabular cup placement, as originally described by Lewinnek, is 15 +/- 10 degrees of anteversion and 40 +/- 10 degrees of abduction. A cup placed in only 5 degrees of anteversion is retroverted relative to the ideal position, predisposing the patient to posterior instability, particularly when hip flexion and internal rotation occur.

Question 6103

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the surgeon assesses the gap kinematics and notes that the knee is tight in full extension but perfectly balanced in 90 degrees of flexion. Which of the following is the most appropriate corrective maneuver?

. Downsize the femoral component
. Recut the proximal tibia with more posterior slope
. Resect more distal femur
. Release the posterior cruciate ligament
. Upsize the polyethylene insert

Correct Answer & Explanation

. Resect more distal femur

Explanation

A tight extension gap with a balanced flexion gap indicates that the distal femoral resection was insufficient. Resecting more distal femur will increase the extension gap without altering the already balanced flexion gap.

Question 6104

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total hip arthroplasty using a posterior approach, the surgeon performs an inferior capsular release. Which vascular structure is at the highest risk of injury during this specific step near the quadratus femoris?

. Superior gluteal artery
. Inferior gluteal artery
. Medial circumflex femoral artery
. Lateral circumflex femoral artery
. Obturator artery

Correct Answer & Explanation

. Medial circumflex femoral artery

Explanation

The medial circumflex femoral artery (MCFA) courses near the superior border of the quadratus femoris. It is the primary blood supply to the femoral head and is highly vulnerable during inferior capsular releases in the posterior approach.

Question 6105

Topic: 3. Adult Reconstruction (Hip & Knee)

In the workup for a suspected chronic periprosthetic joint infection (PJI) of a total knee arthroplasty, joint aspiration is performed. Which of the following synovial fluid biomarkers is an antimicrobial peptide released by neutrophils and is highly specific for diagnosing PJI?

. C-reactive protein (CRP)
. Erythrocyte sedimentation rate (ESR)
. Interleukin-6 (IL-6)
. Alpha-defensin
. Leukocyte esterase

Correct Answer & Explanation

. Alpha-defensin

Explanation

Alpha-defensin is an antimicrobial peptide produced by neutrophils in response to pathogens. It is an extremely sensitive and highly specific synovial fluid biomarker utilized in the major criteria for diagnosing periprosthetic joint infections.

Question 6106

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male with a history of a cemented total hip arthroplasty (THA) 10 years ago presents after a fall with severe left thigh pain. Radiographs reveal a periprosthetic femoral fracture classified as Vancouver B2. The patient is active and otherwise healthy. What is the most appropriate surgical management?

. Open reduction and internal fixation (ORIF) with a cable-plate system.
. Excision arthroplasty (Girdlestone procedure).
. Revision THA with a long, diaphyseal-engaging cemented stem.
. Revision THA with a long, diaphyseal-engaging uncemented stem.
. Cerclage wiring and immobilization in a cast brace.

Correct Answer & Explanation

. Revision THA with a long, diaphyseal-engaging uncemented stem.

Explanation

A Vancouver B2 periprosthetic femoral fracture involves a loose femoral component with adequate bone stock. The treatment for a loose femoral component is revision. Given the B2 classification, a long, diaphyseal-engaging stem is required to bypass the fracture and achieve stable fixation in the diaphysis. While both cemented and uncemented options exist, cemented stems are often preferred in the elderly with poor bone quality and can provide immediate stability, fitting within the context of 'general ortho' options. Uncemented stems are also an option and often preferred in younger, more active patients with good bone stock. However, a cemented stem provides good long-term results in the elderly. ORIF with plates is for Vancouver B1 (stable component), and Girdlestone is a salvage procedure. Cerclage wiring alone is insufficient for a loose component.

Question 6107

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old male with a history of left total knee arthroplasty (TKA) 2 years ago presents with persistent knee pain, swelling, and warmth for 4 months. Laboratory tests show ESR 55 mm/hr and CRP 80 mg/L. A knee aspirate reveals 3,500 WBCs/ยตL with 75% polymorphonuclear leukocytes (PMNs). According to the Musculoskeletal Infection Society (MSIS) criteria for prosthetic joint infection (PJI), what additional finding is most crucial for definitively confirming a PJI diagnosis?

. Presence of a draining sinus tract communicating with the prosthesis.
. Positive leukocyte esterase strip test from the synovial fluid.
. Positive alpha-defensin test from the synovial fluid.
. Growth of a single organism in at least one periprosthetic tissue or fluid culture.
. Intraoperative visualization of purulence around the prosthesis.

Correct Answer & Explanation

. Presence of a draining sinus tract communicating with the prosthesis.

Explanation

According to the revised MSIS criteria (2018), a definitive PJI diagnosis can be made if one of the following is met:1. A sinus tract communicating with the prosthesis.2. Two positive cultures of the same organism from separate periprosthetic tissue or fluid samples.3. Four out of six minor criteria (ESR/CRP, D-dimer, synovial fluid WBC, synovial fluid PMN%, alpha-defensin, leukocyte esterase).The provided information (ESR, CRP, synovial WBC, PMN%) strongly suggests PJI, but to definitively confirm with one major criterion, a draining sinus tract is one of the most direct and undeniable signs. While intraoperative purulence is highly indicative, it's not a formal MSISdefinitivecriterion on its own without cultures or other findings. Positive cultures (at least two of the same organism) are crucial, but the question asks for themostcrucialadditionalfinding, and a sinus tract meets a standalone major criterion. A single positive culture (Option D) is insufficient as per MSIS criteria, as two positive cultures of the same organism are needed, or one positive culture of a virulent organism. Alpha-defensin and leukocyte esterase are minor criteria or adjuncts but not standalone definitive criteria unless combined with other minor criteria.

Question 6108

Topic: 3. Adult Reconstruction (Hip & Knee)
A 70-year-old man presents with progressive pain in his right hip 12 years after a total hip arthroplasty. Radiographs show eccentric wear of the polyethylene liner and focal radiolucencies in the proximal femur. Which of the following is the primary biologic mechanism responsible for this complication?
. Type IV hypersensitivity reaction to metal ions
. Humoral immune response against the implant
. Macrophage-mediated phagocytosis of wear particles leading to cytokine release
. Direct mechanical grinding of the bone by the displaced femoral head
. Osteoblast hyperactivity induced by stress shielding

Correct Answer & Explanation

. Macrophage-mediated phagocytosis of wear particles leading to cytokine release

Explanation

Aseptic loosening secondary to osteolysis is primarily driven by macrophage phagocytosis of ultra-high molecular weight polyethylene (UHMWPE) wear particles. These macrophages subsequently release osteoclast-activating cytokines like TNF-alpha and IL-1, leading to bone resorption.

Question 6109

Topic: Total Hip Arthroplasty (THA)

During a posterior approach to the hip (Kocher-Langenbeck), the surgeon takes care to protect the primary blood supply to the adult femoral head. Which of the following describes the anatomical course of the main branch of the medial femoral circumflex artery (MFCA)?

. Anterior to the quadratus femoris and posterior to the obturator externus
. Posterior to the piriformis and superior to the superior gemellus
. Superior to the obturator internus and anterior to the gluteus medius
. Between the pectineus and the adductor longus
. Inferior to the adductor brevis and anterior to the vastus lateralis

Correct Answer & Explanation

. Anterior to the quadratus femoris and posterior to the obturator externus

Explanation

The deep branch of the medial femoral circumflex artery (MFCA) is the predominant blood supply to the femoral head. It runs anterior to the quadratus femoris muscle and posterior to the obturator externus before ascending along the femoral neck.

Question 6110

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with a painful total knee arthroplasty 5 years after the index procedure. Joint aspiration yields a synovial fluid WBC count of 45,000 cells/uL with 92% neutrophils. Cultures are pending. What is the most widely accepted definitive surgical management for this chronic infection?

. Debridement, antibiotics, and implant retention (DAIR)
. Long-term suppressive oral antibiotics alone
. Arthroscopic joint lavage and synovectomy
. Two-stage revision arthroplasty with an antibiotic spacer
. Immediate single-stage exchange with plain bone cement

Correct Answer & Explanation

. Two-stage revision arthroplasty with an antibiotic spacer

Explanation

For a chronic periprosthetic joint infection (typically presenting months or years postoperatively with mature biofilm), a two-stage revision arthroplasty is the gold standard in North America. DAIR is strictly reserved for acute postoperative infections or acute hematogenous seeding.

Question 6111

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, the surgeon evaluates the trial components. The knee is symmetric and stable in extension, but the flexion gap is unacceptably tight. Which of the following adjustments is the most appropriate next step?

. Recut the distal femur
. Increase the thickness of the polyethylene insert
. Downsize the femoral component
. Release the posterior cruciate ligament
. Upsize the femoral component

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A tight flexion gap with a balanced extension gap requires decreasing the anteroposterior dimension of the femur. Downsizing the femoral component or increasing the posterior slope of the tibial cut effectively increases the flexion gap without altering the extension gap.

Question 6112

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the surgeon uses spacer blocks and notes the knee is well-balanced in extension but tight in flexion. Which of the following intraoperative adjustments is the most appropriate next step?

. Recut the proximal tibia to add more posterior slope
. Upsize the femoral component
. Translate the femoral component posteriorly
. Release the posterior cruciate ligament
. Downsize the femoral component

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A knee that is tight in flexion and balanced in extension requires an increase in the flexion gap without altering the extension gap. Downsizing the femoral component selectively increases the flexion gap.

Question 6113

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old highly active female underwent a total hip arthroplasty using a ceramic-on-ceramic bearing. Three years postoperatively, she complains of a newly developed, audible squeaking sound from the hip during walking. Her hip is completely painless, and radiographs show well-fixed components with no signs of osteolysis. What is the most appropriate management?

. Immediate revision to a metal-on-polyethylene bearing
. Aspiration of the hip joint to rule out infection
. Reassurance and continued observation
. Prescription of a hip abduction brace
. Revision of the acetabular cup only

Correct Answer & Explanation

. Reassurance and continued observation

Explanation

Squeaking in a ceramic-on-ceramic THA can affect up to 10% of patients. In a painless, well-fixed hip with normal radiographs and no mechanical symptoms, the condition is benign, making reassurance and observation the standard of care.

Question 6114

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, the use of highly cross-linked polyethylene (HXLPE) has significantly reduced wear rates. Which of the following manufacturing processes is critical to eliminating free radicals and preventing subsequent oxidative degradation of HXLPE?

. Gamma irradiation in air
. Ethylene oxide sterilization
. Melting or annealing post-irradiation
. Cold working the polymer
. Addition of barium sulfate

Correct Answer & Explanation

. Melting or annealing post-irradiation

Explanation

While irradiation is necessary to create the cross-links that improve wear resistance, it also leaves behind free radicals. Post-irradiation thermal treatment (melting or annealing) is critical to eliminate or reduce these free radicals, thereby preventing long-term oxidation and embrittlement.

Question 6115

Topic: 3. Adult Reconstruction (Hip & Knee)
In aseptic loosening of a total joint arthroplasty, the biologic response to ultra-high molecular weight polyethylene (UHMWPE) wear debris is primarily mediated by which of the following cell types?
. Neutrophils
. Macrophages
. T-lymphocytes
. B-lymphocytes
. Osteoblasts

Correct Answer & Explanation

. Macrophages

Explanation

Aseptic loosening is primarily a macrophage-mediated response. Macrophages phagocytose particulate wear debris (especially UHMWPE particles sized 0.1 to 1.0 micrometers) and subsequently release pro-inflammatory cytokines such as IL-1, IL-6, and TNF-alpha. These cytokines stimulate osteoclastic bone resorption (osteolysis).

Question 6116

Topic: 3. Adult Reconstruction (Hip & Knee)

Ten years after a total hip arthroplasty, a patient presents with increasing groin pain and extensive periprosthetic radiolucencies on imaging, consistent with aseptic loosening. What is the primary cellular mediator initiating this sequence of periprosthetic osteolysis?

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

Correct Answer & Explanation

. Macrophages

Explanation

Particulate polyethylene wear debris is phagocytosed by periprosthetic macrophages. These activated macrophages subsequently release pro-inflammatory cytokines (TNF-alpha, IL-1, IL-6) that aggressively stimulate osteoclastic bone resorption.

Question 6117

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old patient presents with pain and a sterile effusion 5 years after an uncomplicated cementless total hip arthroplasty utilizing a modular titanium femoral stem and a cobalt-chromium head. Which of the following mechanisms most likely explains the findings?

. Galvanic corrosion
. Fretting corrosion
. Stress shielding
. Aseptic loosening secondary to polyethylene wear
. Third-body wear

Correct Answer & Explanation

. Fretting corrosion

Explanation

Fretting corrosion occurs at the modular head-neck junction due to micromotion disrupting the passivation layer. This mechanically assisted crevice corrosion can lead to an adverse local tissue reaction (ALTR) or trunnionosis.

Question 6118

Topic: 3. Adult Reconstruction (Hip & Knee)

Which type of wear is predominantly responsible for the generation of submicron polyethylene particles leading to osteolysis in total hip arthroplasty?

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

Correct Answer & Explanation

. Adhesive wear

Explanation

Adhesive wear occurs when micro-asperities on the femoral head and polyethylene liner weld together and break off during motion. This process is the primary generator of the submicron debris responsible for macrophage-mediated osteolysis.

Question 6119

Topic: 3. Adult Reconstruction (Hip & Knee)
Ultra-high molecular weight polyethylene (UHMWPE) wear debris is a primary cause of aseptic loosening in total joint arthroplasty. Which cell type is primarily responsible for engulfing these particles and initiating the osteolytic cytokine cascade?
. Osteoblasts
. Fibroblasts
. Macrophages
. Polymorphonuclear leukocytes
. Lymphocytes

Correct Answer & Explanation

. Macrophages

Explanation

Macrophages phagocytose the particulate UHMWPE wear debris but cannot digest it. This triggers the release of inflammatory cytokines (TNF-alpha, IL-1, IL-6), which activate osteoclasts and lead to periprosthetic osteolysis.

Question 6120

Topic: 3. Adult Reconstruction (Hip & Knee)

In aseptic loosening of total joint arthroplasty, the biologic cascade leading to osteolysis is primarily initiated by macrophage phagocytosis of particulate wear debris. Which of the following cytokines are most strongly implicated as downstream activators of osteoclasts in this process?

. Interleukin-4 (IL-4) and Interleukin-10 (IL-10)
. Interferon-gamma (IFN-g) and Transforming Growth Factor-beta (TGF-b)
. Tumor necrosis factor-alpha (TNF-a) and Interleukin-1 (IL-1)
. Interleukin-2 (IL-2) and Interleukin-12 (IL-12)
. Bone morphogenetic proteins 2 and 7 (BMP-2/7)

Correct Answer & Explanation

. Tumor necrosis factor-alpha (TNF-a) and Interleukin-1 (IL-1)

Explanation

Macrophage phagocytosis of wear debris (especially polyethylene particles between 0.1 and 10 microns) triggers a vigorous inflammatory response. This causes the release of pro-inflammatory cytokines, predominantly TNF-alpha, IL-1, IL-6, and PGE2, which heavily stimulate osteoclastogenesis and periprosthetic osteolysis.

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