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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 286 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 5701

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male presents with acute onset of extreme left knee pain, swelling, and fever (38.8ยฐC) 18 days after a primary TKA. Joint aspirate yields 65,000 WBC/ยตL with 92% neutrophils. The patient is taken for Debridement, Antibiotics, and Implant Retention (DAIR). Which of the following factors is most crucial for the success of this procedure?

. Exchange of the modular polyethylene insert
. Retaining the original polyethylene insert to preserve joint kinematics
. Administering intravenous antibiotics for 4 weeks before the debridement
. Use of a constrained condylar polyethylene liner
. Applying a hinged knee brace postoperatively

Correct Answer & Explanation

. Exchange of the modular polyethylene insert

Explanation

In the setting of acute periprosthetic joint infection (PJI) treated with DAIR, exchanging the modular components (polyethylene insert) is highly recommended and correlated with significantly higher infection eradication rates. It allows access to the posterior compartment for thorough debridement and removes bacteria adhering to the modular interface.

Question 5702

Topic: Total Hip Arthroplasty (THA)

A 70-year-old female experiences recurrent anterior dislocations of her THA. Operative notes and CT imaging indicate that the combined version (McKibbin index) of her acetabular and femoral components is significantly abnormal. Which of the following combinations of component version is most likely responsible for anterior dislocation?

. Excessive acetabular anteversion and excessive femoral anteversion
. Excessive acetabular retroversion and excessive femoral retroversion
. Normal acetabular anteversion and excessive femoral retroversion
. Decreased acetabular anteversion and decreased femoral anteversion
. Normal acetabular anteversion and normal femoral anteversion

Correct Answer & Explanation

. Excessive acetabular anteversion and excessive femoral anteversion

Explanation

Anterior dislocation of a THA is classically associated with excessive combined anteversion (excessive acetabular anteversion + excessive femoral anteversion). Conversely, posterior dislocation is associated with decreased combined anteversion (retroversion of the cup and/or stem). The combined version should ideally fall within the safe zone of 25 to 45 degrees to maintain stability.

Question 5703

Topic: Total Knee Arthroplasty (TKA)

During a primary TKA, a surgeon uses a reciprocating saw to complete the posterior condylar cuts and inadvertently injures the popliteal artery. Anatomically, at what level does the popliteal artery run closest to the posterior capsule of the knee joint, making it most vulnerable to injury during TKA?

. At the level of the joint line, directly posterior to the posterior cruciate ligament
. At the level of the distal femoral cut, lateral to the midline
. At the level of the tibial cut, just inferior to the joint line
. At the level of the adductor hiatus
. At the origin of the anterior tibial artery

Correct Answer & Explanation

. At the level of the tibial cut, just inferior to the joint line

Explanation

The popliteal artery is closest to the posterior capsule and bone at the level of the proximal tibial bone cut (just distal to the joint line). Studies show the distance from the posterior tibial cortex to the artery can be as little as 2-3 mm. Furthermore, it is tethered at the soleal arch, making it immobile and highly susceptible to injury from penetrating instruments (like a saw blade plunging past the posterior cortex) during the tibial resection.

Question 5704

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old female with severe rheumatoid arthritis presents for primary TKA. Intraoperatively, the medial collateral ligament (MCL) is found to be completely incompetent and cannot be primarily repaired or imbricated to achieve stability. Which of the following bearing designs is most appropriate?

. Posterior-stabilized (PS) articulation
. Cruciate-retaining (CR) articulation
. Varus-valgus constrained (VVC) non-hinged articulation
. Rotating-hinge articulation
. Unicompartmental knee arthroplasty

Correct Answer & Explanation

. Rotating-hinge articulation

Explanation

In the setting of a completely incompetent or deficient medial collateral ligament (MCL), a varus-valgus constrained (VVC) prosthesis is usually insufficient because it relies on functional collateral ligaments to prevent excessive stress on the stabilizing post (which can lead to post failure/breakage). A rotating-hinge knee prosthesis is indicated for severe collateral ligament deficiency (especially MCL), massive bone loss, or extensor mechanism deficiency with global instability, as the hinge mechanism intrinsically provides coronal plane stability without relying on the MCL.

Question 5705

Topic: Total Hip Arthroplasty (THA)

A 65-year-old male with a history of multiple revision THAs presents with severe groin pain. Radiographs demonstrate an acetabular component that has migrated 3 cm superomedially. A CT scan reveals discontinuity of the anterior and posterior columns of the hemipelvis. Which of the following reconstructive options provides the most rigid mechanical fixation for pelvic discontinuity in this setting?

. An oversized hemispherical porous cup with multiple screws
. A custom triflange acetabular component
. Impaction bone grafting with a cemented polyethylene cup
. A standard dual-mobility cup with a posterior column plate
. A constrained acetabular liner in the existing shell

Correct Answer & Explanation

. A custom triflange acetabular component

Explanation

Pelvic discontinuity (a separation of the superior pelvis/ilium from the inferior pelvis/ischium and pubis) is a severe complication in revision THA. Standard hemispherical cups cannot bridge the discontinuity effectively to provide stable long-term fixation. Reconstructive options include cup-cage constructs, custom triflange acetabular components (CTAC), or distraction using a trabecular metal jumbo cup (if adequate bone stock exists). Among the choices, the custom triflange acetabular component provides the most rigid and reliable mechanical fixation by spanning the defect and anchoring to the ilium, ischium, and pubis using patient-specific matching.

Question 5706

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old male presents with inability to perform a straight leg raise 6 months after a TKA. Examination and ultrasound reveal a chronic, complete rupture of the patellar tendon with a 4 cm gap. The tibial tubercle is intact, and the components are well-fixed. What is the most reliable surgical reconstruction method for this chronic defect?

. Primary end-to-end repair with non-absorbable suture
. Primary repair augmented with semitendinosus autograft
. Reconstruction using synthetic mesh or extensor mechanism allograft
. Gastrocnemius rotational flap
. Conversion to a fixed-hinge knee prosthesis

Correct Answer & Explanation

. Reconstruction using synthetic mesh or extensor mechanism allograft

Explanation

Chronic patellar tendon ruptures post-TKA with significant gap formation cannot be treated successfully with primary repair (tissue is poor quality, high failure rate). The gold standard treatments for chronic extensor mechanism disruption post-TKA are either an extensor mechanism allograft (using a block of tibial bone, patellar tendon, patella, and quadriceps tendon) or reconstruction using synthetic mesh (e.g., Marlex mesh). Both have shown comparable, reasonable salvage rates in modern literature, vastly outperforming primary repair or autograft augmentation in the setting of TKA.

Question 5707

Topic: Total Knee Arthroplasty (TKA)

In the context of kinematic alignment for primary TKA, the procedure aims to restore the pre-arthritic native joint lines. When compared to traditional mechanical alignment, what is the most characteristic coronal alignment profile of the final components in a patient with constitutional varus?

. A femoral component in valgus and a tibial component in valgus
. A femoral component in relative valgus and a tibial component in relative varus
. A femoral component in relative varus and a tibial component in relative valgus
. A femoral component in 0 degrees and a tibial component in 0 degrees to the mechanical axis
. A femoral component in relative varus and a tibial component in relative varus

Correct Answer & Explanation

. A femoral component in relative valgus and a tibial component in relative varus

Explanation

Constitutional varus usually arises from a combination of distal femoral valgus (relative to the mechanical axis) and proximal tibial varus (joint line obliquity). Kinematic alignment (KA) aims to co-align the axes of the components with the three kinematic axes of the knee, effectively restoring the patient's native joint line. In a patient with constitutional varus, this typically results in the femoral component being placed in slightly more valgus (compared to the mechanical axis cut of 0 degrees) and the tibial component being placed in varus to match the native proximal tibial joint line obliquity.

Question 5708

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female presents with worsening groin pain 8 years after a metal-on-metal total hip arthroplasty. A MARS MRI reveals a large, thick-walled cystic collection around the hip joint without sinus tracts. Aspiration is negative for acute infection. Which of the following is the hallmark histological finding of the capsular tissue in this condition?

. Granulomatous foreign body reaction with numerous multinucleated giant cells
. Perivascular lymphocytic infiltrate with tissue necrosis and fibrin deposition
. Massive neutrophilic infiltrate with extracellular bacterial biofilms
. Abundant birefringent polyethylene wear debris within macrophages
. Neoplastic spindle cell proliferation with high mitotic activity

Correct Answer & Explanation

. Perivascular lymphocytic infiltrate with tissue necrosis and fibrin deposition

Explanation

The patient has an adverse local tissue reaction (ALTR) or ALVAL (Aseptic Lymphocytic Vasculitis-Associated Lesion) secondary to metal-on-metal wear. ALVAL is characterized by a delayed-type hypersensitivity reaction (Type IV) leading to a dense perivascular lymphocytic infiltrate, tissue necrosis, and fibrin exudation.

Question 5709

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female experiences a chronic, complete patellar tendon rupture following a primary total knee arthroplasty (TKA). She is planned for an extensor mechanism reconstruction utilizing synthetic Marlex mesh. What is the most critical technical step for a successful outcome regarding mesh tensioning?

. Tensioning the mesh with the knee in 90 degrees of flexion to allow postoperative ROM
. Tensioning the mesh tightly and suturing it with the knee in full extension
. Leaving the mesh slightly lax to prevent anterior tibial translation
. Securing the mesh exclusively to the medial retinaculum to prevent lateral subluxation
. Tensioning the mesh with the knee in 30 degrees of flexion to mimic the resting length

Correct Answer & Explanation

. Tensioning the mesh tightly and suturing it with the knee in full extension

Explanation

Extensor mechanism reconstruction post-TKA using Marlex mesh requires rigid, secure fixation to the tibial tubercle and patella/quadriceps, tensioned optimally with the knee in full, maximal extension. Any laxity or tensioning in flexion will reliably result in a clinically significant postoperative extensor lag.

Question 5710

Topic: Total Hip Arthroplasty (THA)

Dual mobility acetabular components are frequently used in revision THA to minimize the risk of dislocation. Which biomechanical principle provides the primary enhancement of stability in dual mobility constructs?

. A constrained liner locking mechanism that mechanically limits head dissociation
. Increased jump distance and greater effective head diameter
. Medialization of the center of rotation combined with decreased femoral offset
. Lateralization of the acetabular center of rotation
. Fixed retroversion of the polyethylene liner within the metal shell

Correct Answer & Explanation

. Increased jump distance and greater effective head diameter

Explanation

Dual mobility cups feature a standard femoral head that articulates within a large polyethylene liner, which in turn articulates within the metal acetabular shell. The large outer diameter of the mobile polyethylene liner increases the effective head size and the jump distance required for the hip to dislocate.

Question 5711

Topic: 3. Adult Reconstruction (Hip & Knee)

An 85-year-old low-demand female sustains a periprosthetic femur fracture around a cemented total hip arthroplasty. Radiographs demonstrate a fracture around the tip of the stem with a loose implant and severe proximal femoral bone loss (Vancouver B3). What is the most reliable surgical management to allow early weight-bearing?

. Open reduction and internal fixation with locking plate and strut allografts
. Revision to a standard-length uncemented diaphyseal-engaging stem
. Impaction bone grafting with a standard length cemented stem
. Revision to a proximal femoral replacement (megaprosthesis)
. Nonoperative management with skeletal traction

Correct Answer & Explanation

. Revision to a proximal femoral replacement (megaprosthesis)

Explanation

Vancouver B3 fractures are characterized by a loose stem and severely compromised proximal bone stock. In elderly, low-demand patients, a proximal femoral replacement bypasses the compromised bone and allows immediate full weight-bearing, offering a lower complication profile compared to complex impaction grafting in this population.

Question 5712

Topic: Total Knee Arthroplasty (TKA)

A patient presents with persistent lateral patellar subluxation and anterior knee pain after a primary TKA. A postoperative CT scan is obtained to evaluate component rotation. Which combination of component malrotation is the most common cause of iatrogenic lateral patellar tracking?

. External rotation of the femoral component and external rotation of the tibial component
. External rotation of the femoral component and internal rotation of the tibial component
. Internal rotation of the femoral component and external rotation of the tibial component
. Internal rotation of the femoral component and internal rotation of the tibial component
. Neutral rotation of the femoral component and external rotation of the tibial component

Correct Answer & Explanation

. Internal rotation of the femoral component and internal rotation of the tibial component

Explanation

Internal rotation of the femoral component shifts the trochlear groove medially, while internal rotation of the tibial component effectively lateralizes the tibial tubercle relative to the trochlea. Both of these rotational errors increase the Q-angle, exacerbating lateral patellar maltracking and anterior knee pain.

Question 5713

Topic: 3. Adult Reconstruction (Hip & Knee)

The alpha-defensin immunoassay has become a highly accurate diagnostic test for periprosthetic joint infection (PJI). What is the biological origin of alpha-defensin in the synovial fluid of an infected joint?

. An acute-phase reactant protein synthesized by hepatocytes
. An antimicrobial peptide released by activated neutrophils
. A cytokine secreted by resident macrophages in the synovium
. An enzyme directly produced by planktonic staphylococcal species
. A degradation byproduct of bacterial biofilm exopolysaccharides

Correct Answer & Explanation

. An antimicrobial peptide released by activated neutrophils

Explanation

Alpha-defensin is a naturally occurring antimicrobial peptide that is released from the granules of activated host neutrophils in response to the presence of pathogens. It serves as an excellent synovial fluid biomarker for periprosthetic joint infection due to its high sensitivity and specificity.

Question 5714

Topic: 3. Adult Reconstruction (Hip & Knee)
A 62-year-old male who underwent an isolated medial unicompartmental knee arthroplasty (UKA) 8 years ago presents with new-onset generalized knee pain. Radiographs show a well-fixed medial implant. What is the most common cause of late failure (>5 years) in a medial UKA?
. Aseptic loosening of the tibial tray
. Progressive polyethylene wear and osteolysis
. Progression of osteoarthritis in the unresurfaced lateral compartment
. Unexplained anterior knee pain
. Periprosthetic joint infection

Correct Answer & Explanation

. Progression of osteoarthritis in the unresurfaced lateral compartment

Explanation

While early and midterm failures of UKA are often due to aseptic loosening or technical errors (e.g., overcorrection), late failure (occurring >5 years postoperatively) is most commonly caused by the natural progression of osteoarthritis in the unresurfaced lateral or patellofemoral compartments.

Question 5715

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male complains of a high-pitched squeaking noise from his hip when walking, 3 years after a primary THA with a ceramic-on-ceramic bearing. What is the primary biomechanical risk factor associated with this phenomenon?

. Use of a larger diameter femoral head
. Inadequate femoral stem offset
. Acetabular cup malposition leading to edge loading and stripe wear
. impingement of the psoas tendon over the anterior capsule
. Aseptic loosening of the femoral stem

Correct Answer & Explanation

. Acetabular cup malposition leading to edge loading and stripe wear

Explanation

Squeaking is a known complication of ceramic-on-ceramic bearings. It is strongly correlated with micro-separation, edge loading, and resultant stripe wear on the ceramic head. The most common underlying cause of edge loading is acetabular cup malposition (e.g., excessive steep inclination or inappropriate version).

Question 5716

Topic: 3. Adult Reconstruction (Hip & Knee)

A 40-year-old active female presents with symptomatic, isolated lateral compartment knee osteoarthritis. Standing alignment radiographs demonstrate a mechanical valgus deformity of 14 degrees originating from the distal femur. Which surgical intervention is most appropriate?

. Medial opening wedge high tibial osteotomy
. Lateral closing wedge high tibial osteotomy
. Medial closing wedge distal femoral osteotomy
. Lateral unicompartmental knee arthroplasty
. Total knee arthroplasty

Correct Answer & Explanation

. Medial closing wedge distal femoral osteotomy

Explanation

For isolated lateral compartment osteoarthritis in a young, active patient with a significant valgus deformity originating from the femur, a distal femoral osteotomy (DFO) is indicated. A medial closing wedge DFO (or lateral opening wedge DFO) effectively corrects the mechanical axis away from the lateral compartment.

Question 5717

Topic: 3. Adult Reconstruction (Hip & Knee)

Modern total hip arthroplasty frequently utilizes highly cross-linked polyethylene (HXLPE) to reduce wear. After gamma irradiation to create cross-links, the polyethylene is often subjected to a thermal process called remelting. What is the primary purpose of remelting?

. To increase the overall yield strength and fatigue resistance of the material
. To promote the alignment of the crystalline lattice structure
. To extinguish residual free radicals and prevent long-term oxidative degradation
. To improve the surface wettability for better synovial fluid lubrication
. To eliminate residual monomer toxicity from the manufacturing process

Correct Answer & Explanation

. To extinguish residual free radicals and prevent long-term oxidative degradation

Explanation

Gamma irradiation generates cross-links that improve wear resistance, but it also cleaves polymer chains, leaving behind free radicals. If left untreated, these free radicals react with oxygen over time, causing oxidative degradation and embrittlement. Remelting the polyethylene above its melting point extinguishes these free radicals, though it slightly decreases the material's fatigue strength.

Question 5718

Topic: 3. Adult Reconstruction (Hip & Knee)

During a complex revision THA for aseptic loosening in a 70-year-old female, the surgeon intraoperatively identifies severe acetabular bone loss. The superior hemipelvis moves completely independently of the inferior hemipelvis. Which of the following reconstructive options provides the necessary stability for this specific defect?

. A jumbo uncemented hemispherical titanium cup alone
. Impaction bone grafting with a standard cemented polyethylene cup
. A cup-cage construct or a custom triflange acetabular component
. A high hip center reconstruction using a standard multi-hole cup
. A bilobed uncemented acetabular component

Correct Answer & Explanation

. A cup-cage construct or a custom triflange acetabular component

Explanation

The patient has pelvic discontinuity, defined as a complete uncoupling of the superior (ilium) and inferior (ischium/pubis) halves of the pelvis. Standard hemispherical cups cannot bridge and stabilize this defect. Rigid fixation bridging the discontinuity is required, best achieved with a cup-cage construct, a custom triflange acetabular component, or a pelvic distraction approach with a highly porous jumbo cup.

Question 5719

Topic: Total Hip Arthroplasty (THA)

A surgeon is templating a primary total hip arthroplasty and decides to utilize a high-offset femoral stem to restore the patient's native anatomy without increasing the leg length. Biomechanically, what is the primary consequence of successfully increasing the femoral offset?

. Increases the joint reaction force across the hip
. Decreases the resting tension of the iliotibial band
. Increases the abductor moment arm, thereby decreasing the total joint reaction force
. Decreases the abductor moment arm, requiring more force to maintain a level pelvis
. Medializes the mechanical axis of the femur, increasing knee valgus strain

Correct Answer & Explanation

. Increases the abductor moment arm, thereby decreasing the total joint reaction force

Explanation

Increasing femoral offset moves the femur laterally relative to the center of rotation of the hip. This directly increases the length of the lever arm for the abductor muscles (abductor moment arm). Because the abductors have a greater mechanical advantage, they require less force to balance the pelvis, which consequently decreases the overall joint reaction force across the hip joint.

Question 5720

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary posterior-stabilized total knee arthroplasty (TKA), the surgeon utilizes spacer blocks to assess gap kinematics. The knee is found to be well-balanced and symmetric in extension, but symmetrically tight in 90 degrees of flexion. Which of the following intraoperative maneuvers is the most appropriate next step to correct this mismatch?

. Resect more distal femur
. Release the posterior cruciate ligament
. Downsize the femoral component and use posterior referencing
. Release the posterior capsule
. Increase the thickness of the polyethylene insert

Correct Answer & Explanation

. Downsize the femoral component and use posterior referencing

Explanation

A knee that is balanced in extension but tight in flexion requires an increase in the flexion gap without altering the extension gap. Downsizing the femoral component (when using a posterior referencing system) takes more bone off the posterior condyles, which increases the flexion gap without affecting the distal femoral cut (extension gap). Resecting more distal femur or releasing the posterior capsule would affect the extension gap.

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