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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 266 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 5301

Topic: Total Hip Arthroplasty (THA)

A 65-year-old female presents with an intractable Trendelenburg lurch and recurrent hip instability 2 years following a THA via a lateral approach. MRI confirms complete avulsion of the gluteus medius and minimus tendons with severe fatty infiltration and atrophy of the muscle bellies. What is the most reliable surgical salvage option for stability?

. Direct anatomical repair of the abductor tendons using bone anchors
. Gluteus maximus muscle transfer
. Revision to a constrained acetabular liner
. Revision to a dual mobility bearing articulation
. Fascia lata autograft augmentation of the deficient capsule

Correct Answer & Explanation

. Direct anatomical repair of the abductor tendons using bone anchors

Explanation

In the setting of chronic, irreparable abductor deficiency with severe fatty atrophy, direct repairs and muscle transfers have unacceptably high failure rates. To prevent dislocation while allowing a functional range of motion, revising the acetabular construct to a dual mobility bearing is highly reliable and preferred over constrained liners, which have higher rates of mechanical failure and loosening.

Question 5302

Topic: 3. Adult Reconstruction (Hip & Knee)

When evaluating a patient for a medial unicompartmental knee arthroplasty (UKA), which of the following clinical or radiographic findings is traditionally considered a strict contraindication according to the Kozinn and Scott criteria?

. Patient age greater than 60 years
. Isolated "bone-on-bone" medial compartment osteoarthritis
. An intact anterior cruciate ligament
. A preoperative flexion contracture of 25 degrees
. Patient weight over 80 kg

Correct Answer & Explanation

. Patient age greater than 60 years

Explanation

Classic Kozinn and Scott criteria established strict contraindications for UKA, including a flexion contracture >15 degrees, varus deformity >10 degrees, ROM <90 degrees, and inflammatory arthritis. An intact ACL is generally required for a mobile-bearing UKA. Weight and age limits have been largely expanded or eliminated in modern indications.

Question 5303

Topic: 3. Adult Reconstruction (Hip & Knee)

The introduction of highly crosslinked polyethylene (HXLPE) in total hip arthroplasty has drastically reduced volumetric wear rates and osteolysis. What is the primary mechanical trade-off associated with the high-dose gamma irradiation process used to create HXLPE?

. Increased susceptibility to in vivo oxidation
. Decreased yield strength, tensile strength, and fatigue resistance
. Increased ultimate tensile strength at the expense of elasticity
. Decreased elastic modulus leading to cold flow deformation
. Enhanced potential for rapid osteointegration

Correct Answer & Explanation

. Increased susceptibility to in vivo oxidation

Explanation

High-dose gamma irradiation breaks molecular chains to create free radicals, which then recombine to form crosslinks, significantly improving wear resistance. However, this process alters the crystalline structure, resulting in decreased mechanical properties, specifically lower yield strength, ultimate tensile strength, and fatigue resistance. This makes HXLPE more susceptible to fracture under high-stress conditions like rim loading.

Question 5304

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total hip arthroplasty, the surgeon opts to increase the femoral neck offset by selecting a different stem option, without changing the vertical neck length or the center of rotation. What is the primary biomechanical effect of this change?

. Increase abductor moment arm and decrease joint reaction force
. Decrease abductor moment arm and increase joint reaction force
. Increase leg length and increase joint reaction force
. Decrease leg length and decrease joint reaction force
. Have no effect on abductor moment arm or joint reaction force

Correct Answer & Explanation

. Increase abductor moment arm and decrease joint reaction force

Explanation

Increasing femoral offset laterally displaces the greater trochanter, which increases the lever arm (moment arm) of the abductor muscles. A longer abductor moment arm means less muscle force is required to maintain a level pelvis during single-leg stance, which consequently decreases the overall joint reaction force across the hip.

Question 5305

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the classic Lewinnek 'safe zone', what is the recommended target range for acetabular cup anteversion and inclination to minimize the risk of dislocation in a primary total hip arthroplasty?

. Anteversion 15° ± 10°, Inclination 40° ± 10°
. Anteversion 25° ± 10°, Inclination 45° ± 10°
. Anteversion 10° ± 5°, Inclination 30° ± 5°
. Anteversion 20° ± 5°, Inclination 50° ± 10°
. Anteversion 5° ± 5°, Inclination 35° ± 10°

Correct Answer & Explanation

. Anteversion 15° ± 10°, Inclination 40° ± 10°

Explanation

The Lewinnek safe zone for acetabular component placement in total hip arthroplasty is defined as an inclination of 40° ± 10° and anteversion of 15° ± 10°. Placing the cup within this zone has traditionally been associated with a lower risk of postoperative dislocation.

Question 5306

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with a painful total knee arthroplasty 2 years postoperatively. Joint aspiration yields a synovial fluid white blood cell (WBC) count of 2,500 cells/µL with 75% polymorphonuclear leukocytes (PMNs). Her serum CRP is 15 mg/L. According to the 2013/2018 Musculoskeletal Infection Society (MSIS) criteria, what is the next best step in diagnosis or management?

. Proceed directly to a two-stage exchange arthroplasty
. Perform a DAIR (Debridement, Antibiotics, and Implant Retention) procedure
. Order synovial alpha-defensin or synovial CRP, or perform a repeat aspiration
. Prescribe 6 weeks of oral antibiotics for presumed early infection
. Initiate lifelong suppressive antibiotic therapy

Correct Answer & Explanation

. Proceed directly to a two-stage exchange arthroplasty

Explanation

The patient's aspirate results (WBC 2,500 and 75% PMNs) are equivocal/indeterminate for a late periprosthetic joint infection (thresholds are typically WBC > 3,000 and PMN > 80%). In cases of indeterminate results, further testing such as synovial alpha-defensin, synovial CRP, or repeat aspiration is recommended to confirm or rule out infection.

Question 5307

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old male undergoes a total hip arthroplasty utilizing a ceramic-on-ceramic bearing surface. At his 2-year follow-up, he notes an audible squeaking sound from his hip during ambulation, though he denies any pain. Radiographs show well-fixed components in acceptable alignment. What is the most recognized mechanical etiology for squeaking in this specific bearing?

. Accelerated polyethylene wear
. Impingement of the femoral neck on the acetabular rim and edge loading
. A microscopic fracture of the ceramic liner
. Aseptic loosening of the femoral stem
. Low-grade periprosthetic joint infection

Correct Answer & Explanation

. Accelerated polyethylene wear

Explanation

Squeaking is a known phenomenon specific to hard-on-hard bearings, particularly ceramic-on-ceramic. It is most commonly associated with component malposition (e.g., steep cup angle) leading to edge loading, loss of fluid film lubrication, and micro-separation or impingement during the gait cycle.

Question 5308

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female with a history of a cementless total hip arthroplasty falls and sustains a periprosthetic femur fracture. Radiographs show a fracture around the stem tip. The stem is loose and has subsided, but the proximal femoral bone stock remains adequate.

Based on the Vancouver classification, what is the injury type and the most appropriate surgical treatment?

. Vancouver B1; Open reduction and internal fixation with cables and a plate
. Vancouver B2; Revision to a long uncemented diaphyseal-fitting stem
. Vancouver B3; Proximal femoral replacement
. Vancouver C; Open reduction and internal fixation
. Vancouver A; Non-operative management

Correct Answer & Explanation

. Vancouver B1; Open reduction and internal fixation with cables and a plate

Explanation

A fracture around the stem or just below it is a Vancouver type B. Because the stem is loose (subsided), it is not a B1. Because the proximal bone stock is adequate, it is a B2 (loose stem, good bone). The standard treatment for a Vancouver B2 fracture is revision arthroplasty using a longer stem (often a diaphyseal-engaging splined, tapered stem) that bypasses the fracture, frequently combined with cerclage wiring.

Question 5309

Topic: 3. Adult Reconstruction (Hip & Knee)
During a primary total knee arthroplasty, the surgeon assesses patellar tracking and notes lateral subluxation of the patella as the knee is flexed. Which of the following intraoperative technical errors is LEAST likely to cause this lateral maltracking?
. Internal rotation of the femoral component
. Internal rotation of the tibial component
. Medialization of the femoral component
. Medialization of the patellar button
. Lateralization of the patellar button

Correct Answer & Explanation

. Medialization of the patellar button

Explanation

Lateral maltracking of the patella is caused by an increased Q-angle or component malrotation. Internal rotation of the femoral or tibial components, medialization of the femoral component, and lateralization of the patellar button all effectively increase the Q-angle and promote lateral subluxation. Conversely, placing the patellar button slightly medially on the native patella lateralizes the bony patella relative to the trochlea, which improves tracking. Thus, medialization of the patellar button is the exception.

Question 5310

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with a metal-on-metal total hip arthroplasty presents with groin pain and swelling 6 years postoperatively. Blood cobalt and chromium levels are significantly elevated. An MRI with MARS reveals a large cystic mass.

What histological finding is most characteristic of this adverse local tissue reaction (ALVAL)?

. Massive sheets of polymorphonuclear leukocytes
. Perivascular lymphocytic infiltrate and extensive tissue necrosis
. Extensive multinucleated giant cells with birefringent particles
. Non-caseating granulomas with epithelioid histiocytes
. Malignant spindle cells with a high mitotic index

Correct Answer & Explanation

. Massive sheets of polymorphonuclear leukocytes

Explanation

Aseptic Lymphocyte-dominated Vasculitis-Associated Lesion (ALVAL) is a type IV delayed hypersensitivity reaction seen in metal-on-metal hip arthroplasty. Histologically, it is characterized by a dense perivascular infiltrate of T-lymphocytes, macrophage accumulation, and varying degrees of tissue necrosis (forming pseudotumors). Multinucleated giant cells with birefringent particles describe polyethylene wear debris, not ALVAL.

Question 5311

Topic: 3. Adult Reconstruction (Hip & Knee)

Highly cross-linked polyethylene (HXLPE) is widely used in modern total hip arthroplasty to reduce volumetric wear. Which of the following is a recognized biomechanical trade-off resulting from the increased radiation dose used to cross-link the polyethylene?

. Decreased oxidation resistance
. Decreased yield strength and fatigue resistance
. Increased volumetric wear rate over time
. Increased risk of audible squeaking
. Decreased adhesive wear resistance

Correct Answer & Explanation

. Decreased oxidation resistance

Explanation

While high doses of gamma radiation improve the wear resistance of polyethylene by creating cross-links, it negatively affects its mechanical properties, resulting in decreased yield strength, ultimate tensile strength, and fatigue resistance. This can make the liner more susceptible to fracture or rim damage, particularly in thin liners or edge-loading situations.

Question 5312

Topic: 3. Adult Reconstruction (Hip & Knee)

Dual mobility articulations in total hip arthroplasty are primarily utilized for patients at high risk of dislocation. Which of the following is a unique complication specifically associated with dual mobility constructs?

. Trunnionosis at the head-neck junction
. Intraprosthetic dislocation
. Audible squeaking during gait
. ALVAL pseudotumor formation
. Corrosion of the acetabular shell

Correct Answer & Explanation

. Trunnionosis at the head-neck junction

Explanation

Intraprosthetic dislocation is a complication unique to dual mobility cups. It occurs when the small inner prosthetic head dissociates from the larger, mobile polyethylene liner. This can occur due to wear of the polyethylene retention rim over time or iatrogenic damage during closed reduction attempts.

Question 5313

Topic: Total Hip Arthroplasty (THA)

During a standard posterior approach to the hip (Moore or Southern approach), the short external rotators are sharply released. Which of the following vessels provides the primary blood supply to the adult femoral head and is at significant risk of injury if dissection is carried too close to the intertrochanteric crest or quadratus femoris?

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

Correct Answer & Explanation

. Medial femoral circumflex artery

Explanation

The medial femoral circumflex artery (MFCA), specifically its deep branch, provides the main arterial blood supply to the adult femoral head. It crosses posterior to the obturator externus tendon and anterior to the quadratus femoris. Dissection or release of the quadratus femoris too close to the femur can injure this crucial vessel.

Question 5314

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old female undergoes a revision total hip arthroplasty for massive aseptic loosening. Intraoperatively, the surgeon notes that the superior half of the acetabulum moves completely independently of the inferior half, indicating a transverse fracture line through the cotyloid fossa. What is the most appropriate acetabular reconstruction technique to address this specific pathology?

. Standard hemispherical multi-hole cup with multiple superior screws
. Impaction bone grafting with an all-poly cemented cup
. Acetabular distraction utilizing a custom triflange or cup-cage construct
. Bipolar hemiarthroplasty to allow for pseudoarthrosis
. Resection arthroplasty (Girdlestone procedure)

Correct Answer & Explanation

. Standard hemispherical multi-hole cup with multiple superior screws

Explanation

The intraoperative finding of the superior and inferior halves of the pelvis moving independently defines pelvic discontinuity. Reconstruction requires stabilizing the two halves of the pelvis. This is typically achieved with a construct that bridges the defect and provides rigid fixation, such as a cup-cage construct, custom triflange acetabular component, or a highly porous shell used with structural allograft/distraction techniques.

Question 5315

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old male is 8 months post-primary total knee arthroplasty. He complains of posterolateral knee pain that is particularly exacerbated by active knee flexion and walking downhill. Examination reveals localized tenderness over the posterolateral joint line. Radiographs reveal a properly sized and aligned femoral component, but there is prominent overhang of the femoral component laterally. What is the most likely diagnosis?

. Iliotibial band friction syndrome
. Popliteus tendon impingement
. Lateral collateral ligament strain
. Fabella syndrome
. Biceps femoris tendinopathy

Correct Answer & Explanation

. Iliotibial band friction syndrome

Explanation

Popliteus tendon impingement is a recognized complication in TKA, often caused by an oversized femoral component or prominent posterolateral overhang of the femoral or tibial tray. The popliteus tendon rubs against the prominent edge during flexion, causing posterolateral knee pain.

Question 5316

Topic: Total Knee Arthroplasty (TKA)

Which of the following statements best describes the surgical principle of true 'kinematic alignment' in total knee arthroplasty?

. Both the femoral and tibial components are placed strictly perpendicular to the overall mechanical axis of the lower extremity.
. The joint line is engineered to remain parallel to the floor during all phases of the normal gait cycle.
. The components are positioned to restore the patient's specific pre-arthritic native joint lines and individual axes of rotation, irrespective of the mechanical axis.
. The femoral component is universally placed in exactly 3 degrees of external rotation relative to the posterior condylar axis.
. Extensive ligamentous soft tissue releases are mandated to ensure perfectly equal rectangular flexion and extension gaps.

Correct Answer & Explanation

. Both the femoral and tibial components are placed strictly perpendicular to the overall mechanical axis of the lower extremity.

Explanation

Kinematic alignment in TKA aims to co-align the axes of the components with the three kinematic axes of the normal knee, thereby restoring the patient's pre-arthritic native anatomy and joint lines. This approach often results in a joint line that is in mild varus compared to traditional mechanical alignment, and typically relies on measured resections with minimal to no soft tissue releases.

Question 5317

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old male requires a revision total knee arthroplasty due to a failed implant complicated by severe varus-valgus instability. Intraoperatively, the medial collateral ligament (MCL) is completely deficient, but femoral and tibial metaphyseal bone stock is adequate. What is the most appropriate implant constraint choice for this patient?

. Posterior stabilized (PS) knee
. Cruciate retaining (CR) knee
. Constrained condylar knee (CCK)
. Rotating hinge knee
. Fixed hinge knee

Correct Answer & Explanation

. Posterior stabilized (PS) knee

Explanation

A Constrained Condylar Knee (CCK) implant provides substantial varus-valgus stability through a tall, thick tibial post, but it requires competent collateral ligaments (primarily the MCL) to function without premature failure. When the MCL is completely deficient or absent, a rotating hinge knee is required to provide the necessary coronal plane stability and prevent dislocation.

Question 5318

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty in a patient with a severe preoperative flexion contracture, the surgeon performs the routine bony cuts, removes posterior femoral osteophytes, and drops in trial components. A 15-degree flexion contracture (tight extension gap) persists, while the flexion gap is well-balanced. What is the next most appropriate step to achieve full extension?

. Recut the proximal tibia to resect an additional 2 mm of bone
. Release the posterior capsule from its femoral attachment
. Downsize the femoral component and use a thicker polyethylene insert
. Release the deep medial collateral ligament
. Recut the posterior femoral condyles

Correct Answer & Explanation

. Recut the proximal tibia to resect an additional 2 mm of bone

Explanation

The treatment algorithm for a persistent flexion contracture (isolated tight extension gap) after standard cuts and removal of posterior osteophytes is to sequentially release the posterior capsule from the posterior femur. If capsular release is insufficient, the surgeon should then recut the distal femur to resect more bone. Recutting the proximal tibia would enlarge both the flexion and extension gaps, requiring a thicker poly, leaving the relative mismatch unchanged.

Question 5319

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with severe lateral hip pain and a profound Trendelenburg gait 3 years following a primary total hip arthroplasty. MRI reveals a massive, retracted tear of the gluteus medius and minimus tendons with fatty infiltration, deemed irreparable. The THA components are well-fixed and optimally positioned.

What is the most recognized salvage muscle transfer procedure to reconstruct the abductor mechanism in this setting?

. Tensor fasciae latae advancement
. Gluteus maximus muscle transfer
. Rectus femoris transfer
. Iliopsoas tendon transfer
. Sartorius muscle transfer

Correct Answer & Explanation

. Tensor fasciae latae advancement

Explanation

For massive, irreparable abductor tears following THA, transfer of the anterior third of the gluteus maximus (often along with the tensor fasciae latae) to the greater trochanter is the most widely recognized and reliable salvage procedure to improve gait mechanics, reduce pain, and restore active abduction.

Question 5320

Topic: 3. Adult Reconstruction (Hip & Knee)

In the diagnostic workup of a painful total knee arthroplasty, the synovial fluid alpha-defensin test is frequently utilized. What is the precise biological nature of alpha-defensin that makes it a highly specific biomarker for periprosthetic joint infection?

. It is an acute-phase reactant synthesized by the liver in direct response to Interleukin-6.
. It is an antimicrobial peptide released by neutrophils in response to the presence of pathogens.
. It is an inflammatory cytokine released by T-lymphocytes during metal hypersensitivity reactions.
. It is a proteolytic enzyme responsible for endogenous cartilage matrix degradation.
. It is a complex polysaccharide produced as a byproduct of bacterial biofilm metabolism.

Correct Answer & Explanation

. It is an acute-phase reactant synthesized by the liver in direct response to Interleukin-6.

Explanation

Alpha-defensin is an antimicrobial peptide that is naturally produced and secreted by host neutrophils in response to infection by pathogens. Because it is part of the innate immune response specifically targeting microbes, its concentration in synovial fluid is highly sensitive and specific for detecting periprosthetic joint infection, distinguishing it from aseptic inflammation.

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