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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 265 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 5281

Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old male presents with aseptic loosening of a THA. Radiographs show a Paprosky Type IIIB femoral defect. The femoral isthmus has approximately 1.5 cm of diaphyseal scratch fit available. What is the most appropriate femoral revision strategy?
. Impaction bone grafting with a cemented stem
. Fully porous-coated cylindrical cementless stem
. Modular fluted tapered cementless stem
. Cemented long stem with cortical strut allografts
. Proximal femoral replacement

Correct Answer & Explanation

. Proximal femoral replacement

Explanation

A Paprosky Type IIIB femoral defect combined with less than 2-3 cm of diaphyseal scratch fit is highly prone to subsidence with standard diaphyseal-engaging stems. A proximal femoral replacement or an impaction grafting with specialized meshes is indicated when diaphyseal fixation is inadequate.

Question 5282

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, what is the most important manufacturing factor responsible for reducing the volumetric wear of highly cross-linked polyethylene?

. Increasing the thickness of the polyethylene liner
. Decreasing the femoral head size
. Increasing the radiation dose during cross-linking
. Sterilization via gamma irradiation in an oxygen-rich environment
. The addition of a metallic backing to the liner

Correct Answer & Explanation

. Increasing the thickness of the polyethylene liner

Explanation

The radiation dose used to cross-link the polyethylene is the primary determinant of its wear resistance. Higher radiation doses increase cross-linking between polymer chains, significantly decreasing volumetric wear. Remelting or annealing is done subsequently to eliminate free radicals.

Question 5283

Topic: Total Knee Arthroplasty (TKA)

In a total knee arthroplasty (TKA), which of the following component positioning errors is most likely to result in lateral patellar maltracking?

. External rotation of the femoral component
. Internal rotation of the femoral component
. External rotation of the tibial component
. Medial placement of the patellar button
. Lateralization of the femoral component

Correct Answer & Explanation

. External rotation of the femoral component

Explanation

Internal rotation of either the femoral or tibial components increases the Q angle, leading to lateral patellar maltracking and potential dislocation. External rotation of the components and medial placement of the patellar button generally improve patellar tracking.

Question 5284

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 Musculoskeletal Infection Society (MSIS) / International Consensus Meeting (ICM) criteria, which of the following establishes a definitive diagnosis of Periprosthetic Joint Infection (PJI) as a major criterion?

. Elevated serum CRP (>10 mg/L) and ESR (>30 mm/hr)
. Elevated synovial fluid PMN percentage (>80%)
. A single positive intraoperative tissue culture
. Positive synovial alpha-defensin test
. Two positive periprosthetic cultures with phenotypically identical organisms

Correct Answer & Explanation

. Elevated serum CRP (>10 mg/L) and ESR (>30 mm/hr)

Explanation

The 2018 ICM criteria establish two 'Major Criteria' for definitive PJI diagnosis: 1) A sinus tract communicating with the joint, or 2) Two positive periprosthetic cultures with phenotypically identical organisms. Options A, B, and D are minor criteria that contribute points toward a diagnosis but are not individually diagnostic. A single positive culture (Option C) is also a minor criterion, except in the case of highly virulent organisms where it may carry more weight, but two are definitive.

Question 5285

Topic: 3. Adult Reconstruction (Hip & Knee)
Historically, ultra-high-molecular-weight polyethylene (UHMWPE) components in total knee arthroplasty were prone to catastrophic fatigue wear and delamination. This mode of failure was most heavily associated with which manufacturing/sterilization process?
. Gamma irradiation in an inert gas (Argon) environment
. Gamma irradiation in air
. Ethylene oxide gas sterilization
. Gas plasma sterilization
. Electron beam irradiation in a vacuum

Correct Answer & Explanation

. Gamma irradiation in air

Explanation

Gamma irradiation of UHMWPE in an oxygen-rich environment (air) generates free radicals within the polymer chains. Over time (in-vivo or during shelf storage), these free radicals react with oxygen, leading to chain scission and oxidative degradation. This severely weakens the polyethylene, making it highly susceptible to subsurface fatigue cracking and massive delamination, particularly in TKA due to high sub-surface contact stresses.

Question 5286

Topic: Total Hip Arthroplasty (THA)

A 72-year-old woman experiences recurrent posterior dislocations following a primary total hip arthroplasty via a posterior approach. Radiographs show a well-fixed cup with 20 degrees of anteversion and 40 degrees of abduction, and a well-fixed stem with 5 degrees of retroversion. What is the most appropriate surgical intervention?

. Revision of the acetabular component to increase anteversion
. Revision of the femoral stem to increase anteversion
. Application of a constrained acetabular liner
. Trochanteric advancement
. Prescribing an abduction brace for 6 weeks

Correct Answer & Explanation

. Revision of the acetabular component to increase anteversion

Explanation

The femoral stem is retroverted (5 degrees), which significantly predisposes the patient to posterior instability. Since the acetabular component is already in an optimal position, revision of the femoral stem to correct the version is the definitive treatment.

Question 5287

Topic: 3. Adult Reconstruction (Hip & Knee)

Three weeks following a primary total knee arthroplasty, a patient presents with sudden onset of progressive pain, erythema, and a large effusion. Joint aspiration yields synovial fluid with a WBC count of 35,000 cells/mcL and 92% neutrophils. What is the most appropriate surgical treatment?

. Single-stage revision arthroplasty
. Two-stage revision arthroplasty with an antibiotic spacer
. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange
. Intravenous antibiotics alone for 6 weeks
. Suppressive oral antibiotics indefinitely

Correct Answer & Explanation

. Single-stage revision arthroplasty

Explanation

For acute periprosthetic joint infections occurring within 4 weeks of the index surgery, DAIR with modular component exchange is indicated. It offers the best chance of retaining the well-fixed implants while mechanically clearing the acute infection before a mature biofilm can form.

Question 5288

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient develops a "foot drop" following a primary total hip arthroplasty (THA). Intraoperative records note significant limb lengthening. Which specific neural component is most anatomically vulnerable to this stretch injury?

. The tibial division of the sciatic nerve
. The common peroneal division of the sciatic nerve
. The sural nerve division
. The anterior branch of the obturator nerve
. The posterior femoral cutaneous nerve

Correct Answer & Explanation

. The tibial division of the sciatic nerve

Explanation

The common peroneal division of the sciatic nerve is uniquely susceptible to stretch injuries during THA lengthening. It has less protective connective tissue (epineurium) than the tibial division and is firmly tethered distally at the fibular head.

Question 5289

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with groin pain 15 years after a primary cementless total hip arthroplasty. Radiographs show eccentric wear of the femoral head within the acetabular cup and focal osteolysis around the proximal femur. Which of the following cells is the primary effector of the osteolysis cascade triggered by the wear debris?

. Osteoblasts
. T-lymphocytes
. Macrophages
. Polymorphonuclear leukocytes
. Chondrocytes

Correct Answer & Explanation

. Osteoblasts

Explanation

Polyethylene wear particles are phagocytosed by macrophages, which then release proinflammatory cytokines (such as TNF-alpha, IL-1, IL-6). These cytokines activate osteoclasts via the RANKL pathway, leading to periprosthetic osteolysis and aseptic loosening.

Question 5290

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the 2018 International Consensus Meeting (ICM) criteria, which of the following is considered a major criterion, diagnostic in isolation, for periprosthetic joint infection (PJI)?

. Elevated serum CRP > 10 mg/L and ESR > 30 mm/hr
. A single positive intraoperative tissue culture with a virulent organism
. A sinus tract communicating with the joint
. Positive leukocyte esterase on synovial fluid dipstick
. Synovial fluid PMN percentage > 80%

Correct Answer & Explanation

. Elevated serum CRP > 10 mg/L and ESR > 30 mm/hr

Explanation

Major criteria for PJI (which are definitive for diagnosis on their own) include a sinus tract communicating directly with the joint, or two positive periprosthetic cultures with phenotypically identical organisms. A single positive culture or elevated biomarkers represent minor criteria.

Question 5291

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty utilizing a gap balancing technique, the surgeon evaluates the joint after initial resections and finds that the knee is tight in flexion and perfectly balanced in extension. Which of the following is the most appropriate next step to correct this mismatch?

. Downsize the femoral component and augment the posterior condyles
. Increase the posterior slope of the tibial cut
. Resect 2 mm more of the distal femur
. Upsize the femoral component
. Release the posterior capsule

Correct Answer & Explanation

. Downsize the femoral component and augment the posterior condyles

Explanation

A tight flexion gap with a balanced extension gap can be addressed by increasing the posterior slope of the proximal tibial cut (which increases the flexion space without significantly affecting extension) or by downsizing the femoral component to decrease the AP dimension. Resecting more distal femur or releasing the posterior capsule only affects the extension gap.

Question 5292

Topic: Total Hip Arthroplasty (THA)

A 72-year-old female sustains a fall 5 years after an uncemented THA. Radiographs reveal a periprosthetic fracture around the femoral stem extending from the distal aspect of the lesser trochanter to just proximal to the tip of the stem. The stem is radiographically loose, but the surrounding cortical bone stock is thick and adequate. How is this fracture classified according to the Vancouver system?

. Vancouver A
. Vancouver B1
. Vancouver B2
. Vancouver B3
. Vancouver C

Correct Answer & Explanation

. Vancouver A

Explanation

Vancouver B fractures occur around or just below the tip of the stem. B1 indicates a well-fixed stem; B2 indicates a loose stem but adequate bone stock; B3 indicates a loose stem with severely deficient bone stock. Since the stem is loose with adequate bone, it is a Vancouver B2 fracture, which typically requires revision using a long-stem prosthesis.

Question 5293

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with a painful "catch" and a palpable pop at the anterior aspect of her knee when extending from a flexed position, one year after a posterior-stabilized total knee arthroplasty. What is the primary etiology of this phenomenon?

. An oversized patellar button impinging on the lateral trochlea
. Formation of a fibrous nodule at the superior pole of the patella catching in the intercondylar box
. Excessive internal rotation of the femoral component
. Excessive posterior tibial slope causing instability
. Asymmetric polyethylene wear leading to subluxation

Correct Answer & Explanation

. An oversized patellar button impinging on the lateral trochlea

Explanation

Patellar clunk syndrome primarily occurs in posterior-stabilized total knees. It is caused by the formation of a fibrous nodule at the superior pole of the patella that engages the intercondylar box of the femoral component during deep flexion and "clunks" out as the knee extends (typically around 30-45 degrees).

Question 5294

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is the hallmark histologic feature of adverse local tissue reaction (ALTR/ALVAL) associated with a failed metal-on-metal total hip arthroplasty?

. Extensive sheet-like infiltration of polymorphonuclear leukocytes
. Abundant foreign body giant cells with birefringent particles under polarized light
. Diffuse perivascular lymphocytic infiltration
. Extensive bone marrow edema and fat necrosis
. Caseating granulomas with Langhans giant cells

Correct Answer & Explanation

. Extensive sheet-like infiltration of polymorphonuclear leukocytes

Explanation

ALVAL (Aseptic Lymphocytic Vasculitis-Associated Lesions) is characterized histologically by a prominent perivascular lymphocytic infiltrate. This represents a Type IV delayed hypersensitivity reaction to metal ions (cobalt and chromium) generated by the bearing surface.

Question 5295

Topic: 3. Adult Reconstruction (Hip & Knee)

To minimize the risk of dislocation following a total hip arthroplasty via a posterior approach, the acetabular component should optimally be placed within Lewinnek's safe zone. What are the parameters of this zone?

. 15 degrees of abduction and 15 degrees of anteversion
. 40 degrees of abduction and 15 degrees of anteversion
. 40 degrees of abduction and 40 degrees of anteversion
. 60 degrees of abduction and 15 degrees of retroversion
. 30 degrees of abduction and 0 degrees of version

Correct Answer & Explanation

. 15 degrees of abduction and 15 degrees of anteversion

Explanation

Lewinnek's safe zone for the acetabular cup is described as 40 ± 10 degrees of abduction (inclination) and 15 ± 10 degrees of anteversion. Implants placed outside this zone have a significantly higher risk of both anterior and posterior dislocation depending on the specific malposition.

Question 5296

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male with a metal-on-polyethylene THA returns 8 years postoperatively with vague groin pain. Joint aspiration yields a sterile, gray-tinged fluid. Serum cobalt is markedly elevated, while chromium levels are normal. Radiographs show no cup loosening. Which of the following is the most likely source of the problem?

. Excessive wear of the highly crosslinked polyethylene liner
. Mechanically assisted crevice corrosion at the head-neck taper junction
. Asymptomatic loosening of the acetabular shell
. Delayed hypersensitivity to the titanium stem
. Occult periprosthetic joint infection

Correct Answer & Explanation

. Excessive wear of the highly crosslinked polyethylene liner

Explanation

Elevated serum cobalt out of proportion to chromium in the setting of a non-metal-on-metal bearing strongly suggests mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck taper junction. This results in local adverse tissue reactions.

Question 5297

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty for a fixed, severe valgus deformity, soft tissue balancing is required. Which structure is typically the first to be released on the lateral side to correct a tight extension gap?

. Lateral collateral ligament
. Popliteus tendon
. Iliotibial band
. Biceps femoris tendon
. Lateral head of the gastrocnemius

Correct Answer & Explanation

. Lateral collateral ligament

Explanation

In a valgus knee, the iliotibial band (ITB) is typically the primary tight structure in extension. The standard sequence of lateral release for a fixed valgus deformity usually begins with the ITB (or posterolateral capsule), followed by the LCL and popliteus depending on whether the tightness persists in flexion or extension.

Question 5298

Topic: 3. Adult Reconstruction (Hip & Knee)

A 40-year-old female underwent a ceramic-on-ceramic THA 3 years ago and now complains of a loud squeaking noise from her hip during gait, without significant pain. Which of the following factors most strongly correlates with the development of squeaking in this bearing surface?

. Profound acetabular cup retroversion
. Edge loading from component malposition
. Use of a large diameter femoral head (>36mm)
. Short femoral neck offset
. Excessive femoral component anteversion

Correct Answer & Explanation

. Profound acetabular cup retroversion

Explanation

Squeaking in ceramic-on-ceramic hips is a multifactorial phenomenon, but it is most strongly associated with edge loading caused by component malposition (such as excessive cup inclination or retroversion) and microseparation, which disrupt normal fluid film lubrication.

Question 5299

Topic: 3. Adult Reconstruction (Hip & Knee)

In total knee arthroplasty, inadvertent internal rotation of the femoral component during bone preparation leads to which of the following kinematic complications?

. Patellar subluxation laterally
. Tight lateral flexion gap
. Symmetrical extension gap widening
. Decreased Q-angle and medial patellar tracking
. Genu recurvatum

Correct Answer & Explanation

. Patellar subluxation laterally

Explanation

Internal rotation of the femoral component shifts the trochlear groove medially relative to the extensor mechanism, effectively increasing the Q-angle. This predisposes the patient to lateral patellar maltracking and subluxation. It also results in a tight medial flexion gap.

Question 5300

Topic: 3. Adult Reconstruction (Hip & Knee)

When planning the surgical management of a chronic periprosthetic joint infection (PJI) of the knee, which of the following is considered an absolute contraindication to a single-stage (direct exchange) revision?

. Infection with methicillin-sensitive Staphylococcus aureus (MSSA)
. Lack of an identified organism from preoperative aspirations
. The presence of a healthy, well-vascularized soft tissue envelope
. Patient age greater than 80 years
. Intact collateral ligaments

Correct Answer & Explanation

. Infection with methicillin-sensitive Staphylococcus aureus (MSSA)

Explanation

A successful single-stage revision heavily relies on the use of targeted, organism-specific antibiotics loaded into the bone cement. If the infecting organism is unknown preoperatively, or if it is a highly resistant pathogen (e.g., MRSA, VRE, fungal), a single-stage exchange is contraindicated, and a two-stage revision with an antibiotic spacer is standard of care.

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