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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 320 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 6381

Topic: Total Knee Arthroplasty (TKA)



A patient with a significant post-traumatic valgus deformity of the proximal tibia is undergoing a primary TKA. Through a standard medial parapatellar arthrotomy, which structure is most commonly released first to balance the fixed valgus knee?

. Superficial medial collateral ligament
. Deep medial collateral ligament
. Posteromedial corner
. Iliotibial band and posterolateral capsule
. Patellar tendon

Correct Answer & Explanation

. Iliotibial band and posterolateral capsule

Explanation

In a fixed valgus knee, the lateral side is tight. Soft tissue balancing requires a sequential release of the tight lateral structures, most commonly starting with the iliotibial band and posterolateral capsule, followed by the popliteus and LCL if needed.

Question 6382

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old patient with a 25-degree coronal plane extra-articular bowing deformity of the midshaft femur presents for a Total Knee Arthroplasty. Which of the following is the most appropriate management?

. Standard TKA with an intra-articular constrained hinge
. Standard TKA with aggressive soft tissue release
. Simultaneous or staged femoral osteotomy and TKA
. TKA using a customized patient-specific cutting block for an intra-articular cut
. TKA with a lateral opening wedge osteotomy at the joint line

Correct Answer & Explanation

. Simultaneous or staged femoral osteotomy and TKA

Explanation

For extra-articular deformities >20 degrees in the coronal plane, intra-articular compensatory bone cuts will compromise collateral ligament attachments. A staged or simultaneous extra-articular osteotomy is indicated.

Question 6383

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total hip arthroplasty for a patient with Crowe IV developmental dysplasia of the hip, a subtrochanteric shortening osteotomy is planned. Which nerve is at the highest risk of injury during the reduction of the hip into the true acetabulum?

. Superior gluteal nerve
. Femoral nerve
. Obturator nerve
. Sciatic nerve
. Lateral femoral cutaneous nerve

Correct Answer & Explanation

. Sciatic nerve

Explanation

The sciatic nerve is highly susceptible to stretch injury when lengthening the limb during THA for severe hip dysplasia. A subtrochanteric shortening osteotomy is often performed to mitigate this risk and allow reduction without excessive tension.

Question 6384

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old female with a metal-on-metal total hip arthroplasty presents with groin pain and a pseudotumor. Histological examination of the periprosthetic tissue is most likely to reveal which of the following?

. Abundant neutrophils and bacteria
. Aseptic lymphocytic vasculitis-associated lesions (ALVAL)
. Extensive polyethylene wear debris with macrophage infiltration
. Giant cell tumor of bone
. Caseating granulomas

Correct Answer & Explanation

. Aseptic lymphocytic vasculitis-associated lesions (ALVAL)

Explanation

Adverse local tissue reactions (ALTR) in metal-on-metal implants are histologically characterized by Aseptic Lymphocytic Vasculitis-Associated Lesions (ALVAL). This represents a type IV delayed hypersensitivity reaction.

Question 6385

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old patient presents with a painful total knee arthroplasty 3 years postoperatively. Joint aspiration yields synovial fluid with a WBC count of 4,500 cells/uL and 85% PMNs. According to the MSIS criteria, how should this be interpreted?

. Normal finding, rule out aseptic loosening
. Inconclusive, repeat aspiration in 6 weeks
. Diagnostic for Periprosthetic Joint Infection (PJI)
. Suggestive of metallosis
. Diagnostic for crystalline arthropathy

Correct Answer & Explanation

. Diagnostic for Periprosthetic Joint Infection (PJI)

Explanation

According to the Musculoskeletal Infection Society (MSIS) criteria for late PJI (>90 days post-op), a synovial fluid WBC count > 3,000 cells/uL or > 80% PMNs is considered a major diagnostic indicator for infection.

Question 6386

Topic: 3. Adult Reconstruction (Hip & Knee)

When placing the acetabular component during a Total Hip Arthroplasty, what is the Lewinnek 'safe zone' to minimize the risk of dislocation?

. 10° ± 10° abduction, 5° ± 10° anteversion
. 20° ± 10° abduction, 30° ± 10° anteversion
. 40° ± 10° abduction, 15° ± 10° anteversion
. 50° ± 10° abduction, 25° ± 10° anteversion
. 45° ± 10° abduction, 0° ± 10° anteversion

Correct Answer & Explanation

. 40° ± 10° abduction, 15° ± 10° anteversion

Explanation

The Lewinnek safe zone for acetabular cup placement is defined as 40° ± 10° of inclination (abduction) and 15° ± 10° of anteversion. Placement outside this zone is associated with a significantly higher risk of impingement and dislocation.

Question 6387

Topic: 3. Adult Reconstruction (Hip & Knee)

A 64-year-old man presents with a painful swelling in his right groin 5 years after a primary total hip arthroplasty using a titanium stem, cobalt-chromium modular head, and highly cross-linked polyethylene liner. Aspiration yields sterile, cloudy, yellowish fluid. Blood tests reveal elevated serum cobalt levels with normal chromium levels. Which of the following is the most likely source of the problem?

. Polyethylene wear
. Trunnionosis at the head-neck junction
. Galvanic corrosion at the stem-cement interface
. Ceramic liner fracture
. Extravasation of intra-articular debris

Correct Answer & Explanation

. Trunnionosis at the head-neck junction

Explanation

Elevated serum cobalt out of proportion to chromium in a metal-on-polyethylene THA is highly indicative of mechanically assisted crevice corrosion (trunnionosis) at the modular head-neck junction. This can cause adverse local tissue reactions (ALTR) presenting as groin masses.

Question 6388

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty, the surgeon evaluates the gaps and finds the knee is well-balanced and stable in extension, but exceptionally tight in 90 degrees of flexion. Which of the following maneuvers is the most appropriate next step to balance the knee?

. Recess the superficial medial collateral ligament
. Downsize the femoral component
. Resect an additional 2 mm of distal femur
. Downsize the tibial polyethylene insert
. Release the posterior capsule

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A knee that is tight in flexion but balanced in extension requires increasing the flexion gap without altering the extension gap. Downsizing the femoral component (utilizing anterior referencing) effectively increases the flexion gap without affecting the extension gap.

Question 6389

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient develops patellar subluxation postoperatively following a total knee arthroplasty. On CT scan evaluation, which of the following component malpositions is most likely responsible for lateral patellar maltracking?

. External rotation of the femoral component
. External rotation of the tibial component
. Lateral translation of the tibial tray
. Internal rotation of the femoral component
. Excessive valgus alignment of the femoral component

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of either the femoral or tibial components effectively lateralizes the tibial tubercle relative to the trochlear groove, increasing the Q-angle. This exacerbates lateral patellar maltracking and subluxation.

Question 6390

Topic: 3. Adult Reconstruction (Hip & Knee)

During a posterior-stabilized total knee arthroplasty, the surgeon notes that the joint is symmetrically balanced in extension but excessively tight in flexion. Which of the following is the most appropriate next step to balance the knee?

. Recut the proximal tibia with increased posterior slope
. Release the posterior capsule
. Downsize the femoral component and use a thicker polyethylene insert
. Downsize the femoral component and use the same polyethylene insert
. Upsize the femoral component and recut the distal femur

Correct Answer & Explanation

. Downsize the femoral component and use the same polyethylene insert

Explanation

A knee that is tight in flexion but balanced in extension requires an increase in the flexion gap without altering the extension gap. Downsizing the femoral component (using anterior referencing) decreases the posterior condylar offset, thereby opening the flexion gap.

Question 6391

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old female with a metal-on-polyethylene total hip arthroplasty presents with new-onset groin pain 5 years postoperatively. Radiographs show well-fixed components. Laboratory workup reveals an elevated serum cobalt-to-chromium ratio of 5:1. What is the most likely source of the elevated metal ions?

. Bearing surface wear
. Mechanically assisted crevice corrosion at the head-neck junction
. Impingement of the neck on the acetabular shell
. Galvanic corrosion at the modular neck-body junction
. Polyethylene debris-induced osteolysis

Correct Answer & Explanation

. Mechanically assisted crevice corrosion at the head-neck junction

Explanation

An elevated cobalt-to-chromium ratio (often >2:1 or 3:1) in a metal-on-polyethylene THA strongly suggests mechanically assisted crevice corrosion (MACC) at the modular head-neck junction, known as trunnionosis. Bearing wear in MoP would not cause selective cobalt elevation.

Question 6392

Topic: 3. Adult Reconstruction (Hip & Knee)
A 55-year-old male with a metal-on-metal total hip arthroplasty presents with a palpable groin mass and neuropathic pain radiating down the anterior thigh. MARS-MRI demonstrates a large cystic mass. Intraoperatively, the mass shows extensive tissue necrosis and an aseptic lymphocytic infiltrate. This reaction is best classified as:
. Type I hypersensitivity
. Type II hypersensitivity
. Type III hypersensitivity
. Type IV hypersensitivity
. Foreign body granulomatous reaction

Correct Answer & Explanation

. Type IV hypersensitivity

Explanation

Adverse local tissue reactions (ALTR) or pseudotumors in metal-on-metal hips are characterized histologically by an aseptic lymphocytic vasculitis-associated lesion (ALVAL). This represents a delayed Type IV (cell-mediated) hypersensitivity reaction to metal ions.

Question 6393

Topic: Total Hip Arthroplasty (THA)

A 15-year-old male presents with a predicted leg length discrepancy of 6.5 cm at skeletal maturity secondary to a physeal arrest of the distal femur. What is the most appropriate definitive management to equalize leg lengths?

. Contralateral distal femoral and proximal tibial epiphysiodesis
. Ipsilateral femoral lengthening
. Contralateral femoral shortening osteotomy
. Use of a permanent 6.5 cm shoe lift
. Ipsilateral proximal tibial lengthening

Correct Answer & Explanation

. Ipsilateral femoral lengthening

Explanation

For predicted leg length discrepancies greater than 5 cm, surgical lengthening of the affected limb is the standard of care. Contralateral epiphysiodesis or shortening is generally reserved for discrepancies of 2-5 cm to avoid unacceptable loss of overall adult height.

Question 6394

Topic: 3. Adult Reconstruction (Hip & Knee)

A 62-year-old female presents with groin pain and a palpable anterior mass 6 years after a metal-on-polyethylene total hip arthroplasty utilizing a large-diameter cobalt-chromium femoral head on a titanium stem. Blood tests reveal elevated serum cobalt levels with normal chromium levels. What is the most likely etiology of her symptoms?

. Polyethylene wear and osteolysis
. Mechanically assisted crevice corrosion at the head-neck junction
. Galvanic corrosion at the stem-cement interface
. Late periprosthetic joint infection
. Edge loading from acetabular cup retroversion

Correct Answer & Explanation

. Mechanically assisted crevice corrosion at the head-neck junction

Explanation

Trunnionosis (mechanically assisted crevice corrosion) occurs at the modular head-neck junction. It is characterized by elevated serum cobalt disproportionate to chromium and adverse local tissue reactions (ALTR) in metal-on-polyethylene implants, particularly those utilizing large-diameter heads.

Question 6395

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female sustains a fall 5 years after an uncemented total hip arthroplasty. Radiographs show a spiral periprosthetic femur fracture occurring around the stem. The stem is visibly subsided by 1 cm compared to previous films, but there is excellent bone stock proximally and distally. What is the appropriate Vancouver classification and standard treatment?

. Vancouver B1; Open reduction and internal fixation with a lateral locking plate
. Vancouver B2; Revision to a long uncemented diaphyseal-engaging stem
. Vancouver B3; Revision with a proximal femoral replacement
. Vancouver C; Open reduction and internal fixation with a lateral locking plate
. Vancouver A; Observation with protected weight-bearing

Correct Answer & Explanation

. Vancouver B2; Revision to a long uncemented diaphyseal-engaging stem

Explanation

A fracture around the stem with a loose implant but adequate bone stock is classified as a Vancouver B2 fracture. The standard of care is revision of the femoral component to a longer diaphyseal-engaging stem (typically fluted and tapered) to bypass the fracture and provide stability.

Question 6396

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male presents with inability to perform a straight leg raise 3 months following a primary total knee arthroplasty. Ultrasound confirms a complete avulsion of the patellar tendon from the tibial tubercle. Given the chronic nature of the tear and poor native tissue quality, reconstructive surgery is planned. Which of the following techniques provides the most reliable long-term functional outcome?

. Direct primary repair with heavy non-absorbable suture
. Primary repair augmented with a single autologous hamstring tendon
. Extensor mechanism allograft reconstruction
. Gastrocnemius rotational flap without fascial augmentation
. Arthroscopic debridement and prolonged cast immobilization

Correct Answer & Explanation

. Extensor mechanism allograft reconstruction

Explanation

Chronic patellar tendon disruptions post-TKA have notoriously high failure rates with direct repair. Extensor mechanism allograft reconstruction (or synthetic mesh reconstruction) provides the most reliable robust fixation and long-term functional restoration when native tissue is compromised.

Question 6397

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old female presents to the emergency department after a mechanical fall. Her right lower extremity is shortened and externally rotated. Radiographs confirm a displaced intracapsular femoral neck fracture. The high risk of avascular necrosis in this injury pattern is primarily due to disruption of which of the following vascular structures?

. Artery of the ligamentum teres
. Medial femoral circumflex artery
. Lateral femoral circumflex artery
. Inferior gluteal artery
. First perforating branch of the profunda femoris

Correct Answer & Explanation

. Medial femoral circumflex artery

Explanation

Correct Answer: Medial femoral circumflex arteryDisplaced femoral neck fractures carry a high risk of avascular necrosis (AVN) of the femoral head. The primary blood supply to the adult femoral head is derived from the ascending cervical branches of the medial femoral circumflex artery (MFCA). These vessels travel along the femoral neck and are highly susceptible to tearing or kinking when the femoral neck is displaced.

Question 6398

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old male undergoes a primary total hip arthroplasty via a posterior approach for severe osteoarthritis. According to epidemiological data, what is the most common early postoperative complication he is at risk for, and what combined patient position most frequently precipitates it?

. Aseptic loosening; excessive weight-bearing
. Infection; prolonged supine positioning
. Dislocation; hip flexion, adduction, and internal rotation
. Dislocation; hip extension, abduction, and external rotation
. Periprosthetic fracture; sudden rotational torque

Correct Answer & Explanation

. Dislocation; hip flexion, adduction, and internal rotation

Explanation

Correct Answer: Dislocation; hip flexion, adduction, and internal rotationPostoperative dislocation is the most common early complication following total hip arthroplasty. When a posterior surgical approach is utilized, the posterior soft tissue envelope is violated, making the hip most unstable in a position of flexion, adduction, and internal rotation. Patients are typically placed on 'posterior hip precautions' to avoid this specific combination of movements.

Question 6399

Topic: 3. Adult Reconstruction (Hip & Knee)
An active 68-year-old woman sustains a displaced femoral neck fracture (Garden IV) after a mechanical fall. She undergoes a total hip arthroplasty. If she had instead been treated with closed reduction and percutaneous pinning (CRPP), which of the following complications would she be at the highest risk for compared to arthroplasty?
. Postoperative hip dislocation
. Avascular necrosis of the femoral head
. Deep vein thrombosis
. Sciatic nerve palsy
. Heterotopic ossification

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Displaced femoral neck fractures (Garden III and IV) disrupt the tenuous blood supply to the femoral head (primarily the medial femoral circumflex artery). Treating a displaced femoral neck fracture with internal fixation (like CRPP or sliding hip screw) carries a high risk of avascular necrosis (AVN) and nonunion, particularly in older adults. Therefore, arthroplasty (hemiarthroplasty or total hip arthroplasty) is generally preferred in the elderly to allow immediate weight-bearing and avoid the complications of AVN and nonunion. Arthroplasty, however, carries a higher risk of dislocation compared to internal fixation.

Question 6400

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old man undergoes a primary total hip arthroplasty via a standard posterior approach. Six weeks postoperatively, he presents to the emergency department with severe hip pain and a shortened, internally rotated leg after bending over to tie his shoes. What is the most likely diagnosis, and what is the primary anatomical structure whose repair during surgery helps mitigate this specific complication?

. Anterior hip dislocation; anterior capsule
. Posterhip dislocation; short external rotators and posterior capsule
. Periprosthetic femur fracture; vastus lateralis
. Aseptic loosening; gluteus medius
. Iliopsoas impingement; iliopsoas tendon

Correct Answer & Explanation

. Posterhip dislocation; short external rotators and posterior capsule

Explanation

Correct Answer: BThe patient's presentation of a shortened, internally rotated leg after bending (flexion, adduction, internal rotation) is classic for a posterior hip dislocation, which is the most common early complication following a posterior approach THA. To minimize this risk, surgeons meticulously perform a posterior soft tissue repair, which involves reattaching the short external rotators (piriformis, superior gemellus, obturator internus, inferior gemellus) and the posterior capsule to the greater tuberosity.

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