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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 288 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 5741

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old woman presents with anterior knee pain and a "catching" sensation 18 months after a posterior-stabilized (PS) TKA. Clinical examination reveals a palpable and audible clunk as the knee moves actively from flexion into extension. What is the most likely etiology of this complication?

. Aseptic loosening of the tibial baseplate
. Undersized femoral component causing mid-flexion instability
. Fibrous nodule formation at the superior pole of the patella
. Excessive internal rotation of the tibial component
. Retained posterior cruciate ligament impingement

Correct Answer & Explanation

. Fibrous nodule formation at the superior pole of the patella

Explanation

Patellar clunk syndrome is a complication primarily associated with PS TKA designs. It occurs when a fibrous nodule forms on the undersurface of the distal quadriceps tendon or superior patellar pole, catching in the intercondylar box of the femur during extension.

Question 5742

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old active male is evaluated for a ceramic-on-ceramic THA. Which of the following acetabular component positioning errors is most strongly associated with the development of postoperative "squeaking" in this specific bearing surface?

. Excessive femoral anteversion
. Cup inclination greater than 50 degrees
. Decreased femoral offset
. Cup retroversion of 10 degrees
. Use of an undersized femoral head

Correct Answer & Explanation

. Cup inclination greater than 50 degrees

Explanation

High cup inclination (steep cup angle > 50 degrees) and malversion can lead to edge loading in ceramic bearings. Edge loading causes loss of fluid film lubrication, resulting in stripe wear and the characteristic squeaking phenomenon.

Question 5743

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old man presents with severe groin pain 5 years after receiving a metal-on-polyethylene THA utilizing a large-diameter cobalt-chromium head on a titanium alloy stem. Laboratory tests show elevated serum cobalt levels with normal serum chromium. What is the most likely diagnosis?

. Polyethylene wear-induced osteolysis
. Mechanically assisted crevice corrosion
. Adverse reaction to metal debris from edge loading
. Deep periprosthetic joint infection
. Aseptic loosening of the acetabular cup

Correct Answer & Explanation

. Mechanically assisted crevice corrosion

Explanation

Mechanically assisted crevice corrosion (trunnionosis) occurs at the modular head-neck junction. It classically presents with an isolated elevation of serum cobalt relative to chromium and can lead to adverse local tissue reactions.

Question 5744

Topic: Total Hip Arthroplasty (THA)

When placing acetabular screws during a primary THA, the surgeon must be aware of the pelvic safe zones to avoid catastrophic neurovascular injury. Placement of a screw in the anterior-inferior quadrant places which of the following structures at highest risk?

. External iliac artery
. Obturator nerve and vessels
. Sciatic nerve
. Superior gluteal artery
. Internal pudendal artery

Correct Answer & Explanation

. Obturator nerve and vessels

Explanation

The anterior-inferior quadrant is considered a "danger zone" during acetabular screw placement because it places the obturator nerve and vessels at high risk. The anterior-superior quadrant risks the external iliac vessels.

Question 5745

Topic: Total Knee Arthroplasty (TKA)

A surgeon is performing a cruciate-retaining TKA. With trial components in place, the knee is well-balanced in extension but exhibits excessive tightness and limited range of motion in flexion, along with paradoxical anterior tibial translation. What is the primary anatomical structure responsible for this finding?

. Medial collateral ligament
. Lateral collateral ligament
. Posterior capsule
. Posterior cruciate ligament
. Quadriceps tendon

Correct Answer & Explanation

. Posterior cruciate ligament

Explanation

In a cruciate-retaining TKA, an excessively tight posterior cruciate ligament prevents normal posterior femoral rollback. This causes the flexion gap to be excessively tight and leads to paradoxical anterior sliding of the femur on the tibia during flexion.

Question 5746

Topic: Total Knee Arthroplasty (TKA)

A patient with a failed TKA requires revision surgery. The surgeon identifies an AORI Type 3 defect, characterized by severe metaphyseal bone loss that compromises the origins of the collateral ligaments. Which of the following constraint levels is definitively required?

. Cruciate-retaining (CR)
. Posterior-stabilized (PS)
. Constrained condylar knee (CCK)
. Rotating-hinge prosthesis
. Unicompartmental knee

Correct Answer & Explanation

. Rotating-hinge prosthesis

Explanation

AORI Type 3 defects involve massive bone loss that compromises the medial and lateral collateral ligament attachments. A rotating-hinge implant provides linked stability and is required to substitute for profound collateral ligament deficiency.

Question 5747

Topic: Total Hip Arthroplasty (THA)

A 55-year-old female presents with recurrent posterior dislocations following a primary THA. Radiographs demonstrate the acetabular component is placed in 10 degrees of retroversion. What is the primary biomechanical mechanism of dislocation in this specific setting?

. Impingement of the greater trochanter against the ilium
. Loss of anterior femoral offset
. Excessive soft tissue laxity of the short external rotators
. Impingement of the anterior femoral neck against the anterior acetabular rim
. Psoas tendon contracture preventing full extension

Correct Answer & Explanation

. Impingement of the anterior femoral neck against the anterior acetabular rim

Explanation

Acetabular retroversion causes early bony impingement of the anterior femoral neck against the prominent anterior rim of the cup during internal rotation and flexion. This impingement serves as a fulcrum, levering the femoral head out of the cup posteriorly.

Question 5748

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the Musculoskeletal Infection Society (MSIS) and International Consensus Meeting criteria, which of the following is considered an absolute major criterion for diagnosing a periprosthetic joint infection (PJI)?

. Elevated serum C-reactive protein (CRP) > 10 mg/L
. Purulence observed in the affected joint intraoperatively
. A sinus tract communicating directly with the prosthesis
. Synovial fluid white blood cell count > 3,000 cells/uL
. Positive synovial fluid alpha-defensin test

Correct Answer & Explanation

. A sinus tract communicating directly with the prosthesis

Explanation

The absolute major criteria for definitive diagnosis of a PJI are either a sinus tract communicating with the prosthesis or two positive periprosthetic cultures with phenotypically identical organisms. The other options are considered minor criteria.

Question 5749

Topic: 3. Adult Reconstruction (Hip & Knee)

In evaluating a patient for a potential unicompartmental knee arthroplasty (UKA), which of the following scenarios is traditionally considered an absolute contraindication?

. Age greater than 60 years
. Body mass index (BMI) of 32
. Inflammatory arthropathy (e.g., Rheumatoid arthritis)
. Isolated medial compartment osteoarthritis with a 5-degree varus deformity
. Intact anterior cruciate ligament

Correct Answer & Explanation

. Inflammatory arthropathy (e.g., Rheumatoid arthritis)

Explanation

Inflammatory arthropathies, such as rheumatoid arthritis, involve the entire synovial lining of the joint. They are an absolute contraindication for UKA because the underlying systemic disease will aggressively progress in the unresurfaced compartments.

Question 5750

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty (TKA), the surgeon evaluates the trial components and finds the knee is tight in full extension but symmetric and perfectly balanced at 90 degrees of flexion. What is the most appropriate surgical step to achieve balance?

. Recut the proximal tibia
. Upsize the femoral component
. Resect additional distal femur
. Release the posterior cruciate ligament
. Downsize the femoral component

Correct Answer & Explanation

. Resect additional distal femur

Explanation

Resecting more distal femur increases the size of the extension gap without affecting the flexion gap. Recutting the tibia would inappropriately increase both gaps, making the knee loose in flexion.

Question 5751

Topic: Total Hip Arthroplasty (THA)

A 45-year-old active male underwent a THA with a ceramic-on-ceramic bearing. Three years later, he complains of an audible squeaking sound during movement but denies pain. What is the most likely biomechanical etiology of this phenomenon?

. Trunnionosis at the head-neck junction
. Edge loading secondary to acetabular component malposition
. Third-body wear from retained cement mantle fragments
. Galvanic corrosion between dissimilar metals
. Delayed Type IV hypersensitivity reaction

Correct Answer & Explanation

. Edge loading secondary to acetabular component malposition

Explanation

Squeaking in ceramic-on-ceramic THA is highly associated with edge loading, often secondary to acetabular cup malposition (steep inclination or severe malversion). Edge loading results in stripe wear, disruption of fluid film lubrication, and subsequent noise.

Question 5752

Topic: Total Knee Arthroplasty (TKA)

Following implantation of trial components in a TKA, the surgeon notes a tendency for lateral patellar subluxation. Both the flexion and extension gaps are symmetric and balanced. Which of the following technical errors is most likely responsible?

. External rotation of the tibial component
. Internal rotation of the femoral component
. Lateral translation of the femoral component
. Medializing the patellar button
. Excessive valgus cut of the distal femur

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of either the femoral or tibial components increases the Q-angle, leading to lateral patellar tracking. Externally rotating the components or medializing the patellar dome improves central patellar tracking.

Question 5753

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with a painful TKA 2 years postoperatively. Joint aspiration yields a synovial WBC count of 4,500 cells/mcL with 75% PMNs, and serum CRP is 15 mg/L. Which additional test provides the highest specificity for confirming periprosthetic joint infection (PJI)?

. Synovial fluid alpha-defensin
. Serum erythrocyte sedimentation rate (ESR)
. Technetium-99m bone scan
. Intraoperative frozen section of periarticular tissue
. Synovial fluid leukocyte esterase colorimetric strip

Correct Answer & Explanation

. Synovial fluid alpha-defensin

Explanation

Synovial alpha-defensin is a highly specific biomarker for PJI, released by neutrophils in response to pathogens. It maintains high specificity regardless of systemic inflammatory conditions or prior antibiotic use.

Question 5754

Topic: Total Hip Arthroplasty (THA)

During acetabular shell fixation in a primary THA, a screw is placed in the anterosuperior quadrant of the acetabulum (based on the Wasielewski quadrant system). Which vascular structure is at greatest risk of iatrogenic injury?

. External iliac artery and vein
. Obturator artery and vein
. Superior gluteal artery and vein
. Internal pudendal artery
. Deep femoral artery

Correct Answer & Explanation

. External iliac artery and vein

Explanation

The anterosuperior quadrant places the external iliac vessels at high risk if screws penetrate the inner cortex. The posterosuperior quadrant is considered the safe zone, although excessively long screws can injure the superior gluteal vessels.

Question 5755

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old female complains of a painful catching sensation and a palpable "clunk" when extending her knee from a flexed position, one year after receiving a posterior-stabilized (PS) TKA. What is the underlying pathology?

. Aseptic loosening of the tibial tray with subsidence
. A fibrosynovial nodule in the suprapatellar pouch engaging the intercondylar box
. Polyethylene wear of the tibial spine (cam-post mechanism)
. An oversized patellar button impinging on the lateral trochlear ridge
. Popliteus tendon impingement on the posterolateral femoral condyle

Correct Answer & Explanation

. A fibrosynovial nodule in the suprapatellar pouch engaging the intercondylar box

Explanation

Patellar clunk syndrome occurs in posterior-stabilized (PS) knees when a fibrosynovial nodule forms at the superior pole of the patella. During active knee extension, this nodule catches in the femoral intercondylar box, producing a painful clunk.

Question 5756

Topic: Total Hip Arthroplasty (THA)

In preoperative templating for a primary THA, medializing the center of rotation of the acetabulum without altering femoral offset achieves which distinct biomechanical advantage?

. Decreases the abductor muscle moment arm
. Increases the overall joint reaction force
. Decreases the joint reaction force by shortening the body weight lever arm
. Increases the body weight lever arm acting on the hip joint
. Increases the risk of early anterior impingement

Correct Answer & Explanation

. Decreases the joint reaction force by shortening the body weight lever arm

Explanation

Medializing the acetabular center of rotation decreases the body weight lever arm. This mechanical advantage reduces the force required by the abductors to maintain a level pelvis, substantially decreasing the hip joint reaction force.

Question 5757

Topic: Total Knee Arthroplasty (TKA)

When choosing between a cruciate-retaining (CR) and a posterior-stabilized (PS) TKA design, the surgeon must consider implant kinematics. A PS TKA relies on the cam-post mechanism to specifically substitute for which native function?

. Posterior femoral rollback during deep flexion
. Varus-valgus stability in full extension
. Prevention of anterior tibial translation in extension
. Medial pivot rotation during early flexion
. Patellar tracking in the proximal trochlear groove

Correct Answer & Explanation

. Posterior femoral rollback during deep flexion

Explanation

The intact posterior cruciate ligament (PCL) drives posterior femoral rollback during deep knee flexion to maximize flexion angle and clear the posterior anatomy. In a PS TKA, the PCL is excised, and the cam-post mechanism engages to recreate this essential rollback.

Question 5758

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old man underwent a primary TKA 14 days ago. He now presents with 3 days of severe knee pain, erythema, and a draining sinus tract. Synovial aspiration grows Staphylococcus aureus. What is the most appropriate initial surgical management?

. One-stage revision arthroplasty with antibiotic-loaded cement
. Two-stage revision arthroplasty with an articulating antibiotic spacer
. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange
. Suppressive intravenous antibiotics alone without surgery
. Arthroscopic joint lavage and targeted synovectomy

Correct Answer & Explanation

. Debridement, antibiotics, and implant retention (DAIR) with polyethylene exchange

Explanation

Debridement, antibiotics, and implant retention (DAIR) with a modular polyethylene exchange is the standard of care for acute postoperative periprosthetic joint infections occurring within 4 weeks of the index surgery when the implants remain stable.

Question 5759

Topic: 3. Adult Reconstruction (Hip & Knee)

A 60-year-old male presents with unexplained groin pain 7 years after a THA utilizing a large-diameter cobalt-chrome head on a titanium stem. Imaging shows no osteolysis. Serum cobalt levels are significantly elevated, while chromium levels are normal. What is the most likely diagnosis?

. Aseptic loosening of the femoral stem
. Polyethylene disease
. Chronic subclinical PJI
. Metallosis from acetabular shell wear
. Mechanically assisted crevice corrosion (MACC) at the head-neck taper

Correct Answer & Explanation

. Mechanically assisted crevice corrosion (MACC) at the head-neck taper

Explanation

Trunnionosis, or mechanically assisted crevice corrosion (MACC), occurs at the modular head-neck taper junction, especially with large metal heads on titanium stems. It typically presents with disproportionately elevated serum cobalt relative to chromium.

Question 5760

Topic: 3. Adult Reconstruction (Hip & Knee)

A 35-year-old male with a history of high-dose corticosteroid use is diagnosed with osteonecrosis of the femoral head. MRI reveals subchondral edema but no subchondral collapse (Ficat Stage II). What is the primary physiological rationale for performing a core decompression?

. To provide immediate structural support to the subchondral plate
. To decrease intraosseous pressure and promote vascular ingrowth
. To replace the entire necrotic segment with structurally viable allograft
. To mechanically alter the weight-bearing axis of the proximal femur
. To induce targeted osteolysis of the necrotic bone segment

Correct Answer & Explanation

. To decrease intraosseous pressure and promote vascular ingrowth

Explanation

Core decompression aims to physically drill into the necrotic lesion to reduce the elevated intraosseous pressure characteristic of early-stage AVN. This pressure relief alleviates pain and creates a channel to facilitate the ingrowth of new vascular tissue.

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