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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 238 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 4741

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty utilizing an anterior referencing system, the surgeon decides to upsize the femoral component. What is the most likely biomechanical consequence of this adjustment?

. Increased flexion gap
. Decreased flexion gap
. Anterior overstuffing of the patellofemoral joint
. Notching of the anterior femoral cortex
. Tight extension gap

Correct Answer & Explanation

. Decreased flexion gap

Explanation

In an anterior referencing system, the anterior cut is fixed. Upsizing the femoral component shifts the posterior condylar cut posteriorly, which adds bone to the posterior condyles and decreases (tightens) the flexion gap.

Question 4742

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female presents with recurrent anterior dislocations of her total hip arthroplasty. Radiographs reveal the acetabular component is placed in 45 degrees of abduction and 40 degrees of anteversion. The femoral stem is in 15 degrees of anteversion. What is the most appropriate surgical management?

. Revise the acetabular component to decrease anteversion
. Revise the acetabular component to increase anteversion
. Revise the femoral stem to decrease anteversion
. Exchange the modular head to a longer neck
. Perform an isolated soft tissue capsular plication

Correct Answer & Explanation

. Revise the acetabular component to decrease anteversion

Explanation

Anterior dislocation is typically caused by excessive combined anteversion or excessive extension. The acetabular cup here has excessive anteversion (40 degrees); revising it to a more neutral anteversion is required.

Question 4743

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient develops a foot drop and numbness over the first web space of the foot immediately following a primary total knee arthroplasty for a severe valgus deformity (25 degrees). What is the most likely etiology of this complication?

. Traction injury to the common peroneal nerve
. Direct laceration of the deep peroneal nerve
. Compartment syndrome of the anterior leg
. Tourniquet-induced neurapraxia
. Thermal injury from bone cement

Correct Answer & Explanation

. Traction injury to the common peroneal nerve

Explanation

Correction of a severe valgus deformity in TKA stretches the contracted lateral structures. This leads to a high risk of traction neuropraxia to the common peroneal nerve, presenting as foot drop.

Question 4744

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with a draining sinus tract on the anterior knee 8 weeks after a primary total knee arthroplasty. According to the Musculoskeletal Infection Society (MSIS) criteria, what is the next best step to confirm the diagnosis of a periprosthetic joint infection?

. No further testing is needed to confirm the diagnosis
. Obtain a serum C-reactive protein (CRP) level
. Perform a joint aspiration for cell count and differential
. Order a labeled white blood cell scan
. Measure alpha-defensin levels in the synovial fluid

Correct Answer & Explanation

. No further testing is needed to confirm the diagnosis

Explanation

According to the MSIS criteria, the presence of a sinus tract communicating with the prosthesis is a major criterion. It is definitively diagnostic for a periprosthetic joint infection (PJI) on its own.

Question 4745

Topic: 3. Adult Reconstruction (Hip & Knee)

During a complex primary total knee arthroplasty, the medial collateral ligament (MCL) is completely avulsed from its femoral origin and cannot be reliably repaired. The joint exhibits gross instability in coronal opening. Which of the following implant designs is strictly indicated?

. Constrained condylar knee (CCK) or rotating hinge
. Posterior-stabilized (PS) knee
. Cruciate-retaining (CR) knee
. Mobile-bearing knee
. Unicompartmental knee arthroplasty

Correct Answer & Explanation

. Constrained condylar knee (CCK) or rotating hinge

Explanation

Complete incompetence of the MCL results in a lack of primary coronal stability. A constrained condylar knee (CCK) or a rotating hinge device is required to substitute for the deficient collateral ligament.

Question 4746

Topic: Total Hip Arthroplasty (THA)

When exposing the hip via the posterior approach (Moore), which of the following vascular structures is at greatest risk of injury during the release of the short external rotators and the quadratus femoris?

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

Correct Answer & Explanation

. Medial femoral circumflex artery

Explanation

The ascending branch of the medial femoral circumflex artery crosses the upper border of the quadratus femoris. It is at high risk of injury during the release of the short external rotators and must be carefully coagulated.

Question 4747

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the flexion gap is assessed and found to be excessively tight, while the extension gap is perfectly balanced. Which of the following is the most appropriate surgical step to balance the knee?

. Increase the distal femoral resection
. Decrease the anteroposterior size of the femoral component
. Release the posterior capsule
. Upsize the tibial polyethylene insert
. Recess the superficial medial collateral ligament

Correct Answer & Explanation

. Decrease the anteroposterior size of the femoral component

Explanation

A tight flexion gap with a balanced extension gap requires decreasing the anteroposterior dimension of the femur. This is achieved by downsizing the femoral component and resecting more posterior condylar bone.

Question 4748

Topic: 3. Adult Reconstruction (Hip & Knee)

In total hip arthroplasty, successfully increasing the femoral offset without significantly changing the leg length will have which of the following primary biomechanical effects?

. Increase the overall joint reaction force
. Decrease the abductor moment arm
. Increase the required abductor muscle tension to maintain a level pelvis
. Decrease the risk of bony impingement and increase the abductor moment arm
. Medialize the functional center of rotation

Correct Answer & Explanation

. Decrease the risk of bony impingement and increase the abductor moment arm

Explanation

Increasing femoral offset lateralizes the proximal femur, which increases the abductor moment arm. This improves abductor efficiency, decreases the overall joint reaction force, and reduces the risk of bony impingement.

Question 4749

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male presents with new-onset groin pain 5 years after a primary metal-on-polyethylene total hip arthroplasty. Radiographs show a well-fixed stem and cup. Serum laboratory analysis reveals significantly elevated cobalt levels with normal chromium levels. What is the most likely diagnosis?

. Polyethylene wear osteolysis
. Periprosthetic joint infection
. Trunnionosis
. Metallosis from acetabular cup loosening
. Adverse local tissue reaction from head-liner impingement

Correct Answer & Explanation

. Trunnionosis

Explanation

Elevated serum cobalt with normal chromium in the setting of a metal-on-polyethylene bearing strongly indicates mechanically assisted crevice corrosion at the head-neck junction (trunnionosis). It often presents with groin pain and can lead to adverse local tissue reactions.

Question 4750

Topic: 3. Adult Reconstruction (Hip & Knee)

A 75-year-old female sustains a periprosthetic femur fracture 8 years after a total hip arthroplasty.

Radiographs reveal a fracture extending just distal to the tip of the stem. The stem demonstrates subsidence and is clinically loose, but the proximal femoral bone stock remains adequate. According to the Vancouver classification, what is the most appropriate management?

. Open reduction and internal fixation with a lateral locking plate
. Revision to a standard length cemented stem
. Revision to a long fully porous-coated or fluted tapered stem
. Cortical strut allografting alone
. Proximal femoral replacement

Correct Answer & Explanation

. Revision to a long fully porous-coated or fluted tapered stem

Explanation

This describes a Vancouver B2 fracture (loose stem with adequate surrounding bone stock). The gold standard treatment is bypassing the fracture with a long, distally engaging (fluted tapered or fully porous) uncemented revision stem.

Question 4751

Topic: 3. Adult Reconstruction (Hip & Knee)

During a complex revision total knee arthroplasty, the surgeon notes complete incompetence of the medial collateral ligament (MCL). Which level of prosthetic constraint is most appropriate to ensure coronal plane stability?

. Cruciate-retaining (CR)
. Posterior-stabilized (PS)
. Constrained condylar knee (CCK)
. Rotating hinge knee (RHK)
. Medial pivot knee replacement

Correct Answer & Explanation

. Rotating hinge knee (RHK)

Explanation

A rotating hinge knee (RHK) is indicated when there is global instability or complete disruption of the collateral ligaments (MCL or LCL). A CCK device requires at least one competent collateral ligament to function properly.

Question 4752

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with a painful total knee arthroplasty 2 years postoperatively. Diagnostic synovial fluid aspiration reveals a white blood cell count of 45,000 cells/mcL with 92% polymorphonuclear leukocytes. According to current MSIS criteria, what is the most appropriate definitive management?

. Intravenous antibiotics for 6 weeks followed by lifetime oral suppression
. Debridement, antibiotics, and implant retention (DAIR)
. Arthroscopic joint lavage and synovectomy
. Two-stage revision arthroplasty
. Observation and repeat aspiration in 2 weeks

Correct Answer & Explanation

. Two-stage revision arthroplasty

Explanation

Synovial fluid WBC > 3,000 cells/mcL or PMN > 80% strongly indicates chronic periprosthetic joint infection in a knee >4 weeks post-op. The standard of care for chronic PJI in North America is a two-stage revision.

Question 4753

Topic: 3. Adult Reconstruction (Hip & Knee)

Excessive internal rotation of the femoral component during a primary total knee arthroplasty is most likely to result in which of the following biomechanical complications?

. Medial patellar subluxation
. Lateral patellar tracking and tilt
. Excessive flexion gap laxity
. Decreased femoral rollback
. Patella baja

Correct Answer & Explanation

. Lateral patellar tracking and tilt

Explanation

Internal rotation of the femoral or tibial components dynamically increases the Q-angle during flexion. This leads to lateral patellar tracking, tilt, and an increased risk of patellar subluxation or dislocation.

Question 4754

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents with progressive left thigh and knee pain for the last year. 5 years ago she sustained a femoral neck fracture treated with a cementless hemiarthroplasty. The thigh pain is worse with weight-bearing. CRP and ESR are within normal limits. Based on her clinical presentation and radiographs, what is the most likely cause of her pain?

. Acetabular erosion
. Aseptic loosening
. Periprosthetic joint infection
. Abductor tendon tear
. Heterotopic ossification

Correct Answer & Explanation

. Aseptic loosening

Explanation

The presentation of progressive thigh pain with weight-bearing, normal inflammatory markers, and a cementless stem points to aseptic loosening. Radiographic signs often include progressive radiolucent lines and distal pedestal formation.

Question 4755

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old man undergoes a primary total hip arthroplasty via a posterior approach. Six weeks postoperatively, he sustains a posterior dislocation while bending forward. What is the most common cause of early posterior dislocation following THA?

. Component malposition
. Infection
. Abductor deficiency
. Polyethylene wear
. Aseptic loosening

Correct Answer & Explanation

. Component malposition

Explanation

Component malposition (especially acetabular retroversion or inadequate femoral anteversion) is the most common cause of early instability and dislocation following total hip arthroplasty.

Question 4756

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is considered an absolute contraindication for a unicompartmental knee arthroplasty (UKA)?

. Age greater than 60 years
. Inflammatory arthritis
. Isolated medial compartment osteoarthritis
. Intact anterior cruciate ligament (ACL)
. Body mass index (BMI) over 30

Correct Answer & Explanation

. Inflammatory arthritis

Explanation

Inflammatory arthritis (such as rheumatoid arthritis) affects the entire joint uniformly and is a strict contraindication to UKA, as the remaining compartments will continue to degenerate rapidly.

Question 4757

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty (TKA), after making the initial bone cuts, the surgeon notes that the extension gap is tight but the flexion gap is perfectly balanced. What is the most appropriate surgical step to correct this mismatch?

. Resect more distal femur
. Resect more proximal tibia
. Downsize the femoral component
. Upsize the polyethylene insert
. Release the posterior cruciate ligament (PCL)

Correct Answer & Explanation

. Resect more distal femur

Explanation

A tight extension gap with a balanced flexion gap requires an intervention that affects only extension. Resecting more distal femur opens the extension gap without altering the flexion gap. Resecting more tibia would loosen both gaps.

Question 4758

Topic: Total Knee Arthroplasty (TKA)

Conversely, if during TKA the extension gap is perfectly balanced but the flexion gap is excessively tight, which of the following maneuvers is the most appropriate corrective action?

. Resect more distal femur
. Resect more proximal tibia
. Downsize the femoral component (more posterior resection)
. Release the medial collateral ligament
. Use a thicker polyethylene insert

Correct Answer & Explanation

. Downsize the femoral component (more posterior resection)

Explanation

To correct a tight flexion gap with a balanced extension gap, you must intervene on the posterior femoral condyles. Downsizing the femoral component increases the posterior femoral resection, thus opening up the flexion gap exclusively. Alternatively, increasing the posterior tibial slope can also achieve this.

Question 4759

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents 1 year after posterior-stabilized (PS) total knee arthroplasty complaining of an audible and painful "pop" when extending the knee from a flexed position. What is the most likely diagnosis?

. Aseptic loosening of the tibial tray
. Patellar component dissociation
. Patellar clunk syndrome
. Polyethylene wear
. Iliotibial band friction syndrome

Correct Answer & Explanation

. Patellar clunk syndrome

Explanation

Patellar clunk syndrome is characterized by a painful catch or pop during active knee extension (typically around 30-45 degrees of flexion). It is caused by a fibrotic nodule forming at the superior pole of the patella that catches in the intercondylar box of a posterior-stabilized (PS) femoral component.

Question 4760

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a large diameter metal-on-metal total hip arthroplasty presents with groin pain and a large cystic mass. Aspiration reveals thick, grayish fluid. Histological analysis of the periprosthetic tissue will most likely demonstrate:

. Neutrophil-rich acute inflammatory exudate
. Extensive perivascular lymphocytic infiltrate (ALVAL)
. Sheets of giant cells containing polyethylene particles
. Caseating granulomas
. Avascular necrosis of bone with empty lacunae

Correct Answer & Explanation

. Extensive perivascular lymphocytic infiltrate (ALVAL)

Explanation

Metal-on-metal implants can generate metal ions that incite a Type IV delayed hypersensitivity reaction, known as Aseptic Lymphocytic Vasculitis Associated Lesion (ALVAL). This is characterized histologically by a dense perivascular lymphocytic infiltrate and presents clinically as a pseudotumor.

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