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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 323 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 6441

Topic: 3. Adult Reconstruction (Hip & Knee)

In a complex revision total hip arthroplasty, the acetabular component is placed in a "high hip center" without lateralization. How does this specific placement affect hip biomechanics compared to an anatomic center?

. Decreases both abductor lever arm and body weight lever arm
. Increases abductor lever arm and decreases body weight lever arm
. Decreases abductor lever arm but maintains body weight lever arm relatively unchanged
. Increases both abductor lever arm and body weight lever arm
. Dramatically decreases the joint reaction force

Correct Answer & Explanation

. Decreases abductor lever arm but maintains body weight lever arm relatively unchanged

Explanation

A high hip center shifts the center of rotation superiorly. Because the greater trochanter moves relatively closer to the joint center, the abductor lever arm is shortened, requiring greater muscle force and thereby increasing the joint reaction force.

Question 6442

Topic: Total Hip Arthroplasty (THA)

A 12-year-old girl is calculated to have a projected leg length discrepancy of 1.5 cm at skeletal maturity. She is currently asymptomatic but her parents are highly concerned. What is the most appropriate management recommendation?

. Distal femoral epiphysiodesis
. Proximal tibial epiphysiodesis
. Distraction osteogenesis for femoral lengthening
. No operative intervention
. Proximal femoral shortening osteotomy

Correct Answer & Explanation

. No operative intervention

Explanation

Leg length discrepancies of less than 2.0 cm at skeletal maturity rarely cause functional impairment and are generally well tolerated. Non-operative management, such as observation or a simple shoe lift if symptomatic, is indicated.

Question 6443

Topic: Total Hip Arthroplasty (THA)

A distal femoral osteotomy is planned for a 12-degree valgus deformity. If a lateral opening wedge technique is executed, what associated structural change is inherent to this procedure?

. Significant shortening of the femur
. Lengthening of the femur
. Medial translation of the mechanical axis without angulation correction
. Increase in the anatomical femorotibial angle
. Decreased resting tension on the iliotibial band

Correct Answer & Explanation

. Lengthening of the femur

Explanation

Opening wedge osteotomies inherently add length to the bone segment due to the addition of space (and often a bone graft) at the osteotomy site. This can be beneficial if the valgus limb is also short, but may cause an unwanted leg length discrepancy if the limbs were equal preoperatively.

Question 6444

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with acute knee swelling, erythema, and severe pain 14 days after a primary total knee arthroplasty. Aspiration yields 65,000 WBCs/mcL with 95% neutrophils. What is the most appropriate surgical management?

. One-stage revision arthroplasty
. Two-stage revision arthroplasty with an antibiotic spacer
. Debridement, antibiotics, and implant retention (DAIR) with modular component exchange
. Intravenous antibiotics for 6 weeks followed by oral suppression
. Amputation

Correct Answer & Explanation

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

Explanation

In the setting of an acute early postoperative prosthetic joint infection (within 4 weeks), DAIR with exchange of modular components is the standard of care. This approach offers a reasonable chance of eradicating the infection while preserving the fixed implants.

Question 6445

Topic: 3. Adult Reconstruction (Hip & Knee)

According to the Musculoskeletal Infection Society (MSIS) criteria, which of the following synovial fluid leukocyte counts and polymorphonuclear (PMN) percentages is the established threshold for diagnosing a chronic prosthetic joint infection (PJI) in a total knee arthroplasty greater than 6 weeks postoperatively?

. > 1,500 cells/uL and > 65% PMNs
. > 3,000 cells/uL and > 80% PMNs
. > 10,000 cells/uL and > 90% PMNs
. > 25,000 cells/uL and > 95% PMNs
. > 50,000 cells/uL and > 75% PMNs

Correct Answer & Explanation

. > 3,000 cells/uL and > 80% PMNs

Explanation

The MSIS criteria state that for a chronic PJI (diagnosed >6 weeks post-surgery), a synovial fluid white blood cell count greater than 3,000 cells/uL with >80% PMNs is highly suggestive of infection. Acute infections or native joint septic arthritis utilize much higher thresholds.

Question 6446

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with a history of severe Brooker class IV heterotopic ossification following a right total hip arthroplasty (THA) is scheduled for a left THA. Which of the following is the most effective prophylactic regimen for this high-risk patient?

. High-dose oral corticosteroids for 2 weeks
. Continuous passive motion starting immediately post-op
. Oral Alendronate for 3 months postoperatively
. Single dose of 700 cGy radiation administered within 24-48 hours postoperatively
. Intravenous tranexamic acid during the procedure

Correct Answer & Explanation

. Single dose of 700 cGy radiation administered within 24-48 hours postoperatively

Explanation

For high-risk patients (prior severe HO), prophylaxis with a single fraction of 700-800 cGy radiation within 24-48 hours postoperatively is the standard of care. A 6-week course of indomethacin is also effective but may have gastrointestinal side effects.

Question 6447

Topic: 3. Adult Reconstruction (Hip & Knee)
Following a total hip arthroplasty, a patient's 6-month follow-up pelvic radiograph demonstrates heterotopic ossification with bone islands extending between the pelvis and proximal femur, leaving less than 1 cm of space between opposing bone surfaces. What is the Brooker classification for this HO?
. Grade I
. Grade II
. Grade III
. Grade IV
. Grade V

Correct Answer & Explanation

. Grade IV

Explanation

The Brooker classification of HO designates Grade I as islands of bone, Grade II as >1 cm between opposing bone surfaces, Grade III as <1 cm between opposing surfaces, and Grade IV as true ankylosis.

Question 6448

Topic: 3. Adult Reconstruction (Hip & Knee)

A 30-year-old male presents with chronic shoulder pain and weakness. Radiographs demonstrate complete resorption of the humeral head and glenoid without any signs of reactive bone formation or sclerosis.

What is the expected initial laboratory profile?

. Elevated alkaline phosphatase, normal calcium
. Markedly elevated parathyroid hormone (PTH)
. Elevated serum ACE levels
. Normal calcium, phosphorus, and alkaline phosphatase
. Monoclonal spike on serum protein electrophoresis

Correct Answer & Explanation

. Normal calcium, phosphorus, and alkaline phosphatase

Explanation

Gorham-Stout disease causes massive osteolysis strictly due to vascular proliferation, not from a systemic metabolic derangement. Therefore, routine laboratory values, including calcium, phosphorus, and alkaline phosphatase, are characteristically within normal limits.

Question 6449

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old male undergoes a right total hip arthroplasty. He has a history of severe Brooker class IV heterotopic ossification (HO) following a previous left THA. Which of the following is the most appropriate pharmacologic prophylaxis to prevent HO in this patient?

. Ibuprofen 400 mg TID for 7 days
. Indomethacin 75 mg sustained-release daily for 3 to 6 weeks
. Celecoxib 200 mg daily for 3 days
. Alendronate 70 mg weekly for 6 months
. Intravenous pamidronate single dose postoperatively

Correct Answer & Explanation

. Indomethacin 75 mg sustained-release daily for 3 to 6 weeks

Explanation

Indomethacin is the standard and most extensively studied pharmacologic prophylactic agent for heterotopic ossification following THA. It is typically given as 75 mg sustained-release daily for 3 to 6 weeks postoperatively.

Question 6450

Topic: 3. Adult Reconstruction (Hip & Knee)

A 38-year-old female presents with intractable pelvic pain and progressive deformity. Radiographs demonstrate massive osteolysis of the left hemipelvis.

Which of the following statements is true regarding the natural history of this disease?

. Spontaneous arrest of the osteolysis is common after a variable period of progression
. Wide local excision and endoprosthetic reconstruction provide excellent long-term survival
. The disease process strictly respects the articular cartilage and joint spaces
. Systemic cytotoxic chemotherapy is required to eradicate the malignant cells
. The condition is typically driven by an underlying primary hyperparathyroidism

Correct Answer & Explanation

. Spontaneous arrest of the osteolysis is common after a variable period of progression

Explanation

Gorham-Stout disease (massive osteolysis) is a rare, unpredictable condition that often progresses to destroy entire bones but commonly undergoes spontaneous arrest after a variable period. It does not respect joint spaces and can cross joints to involve adjacent bones.

Question 6451

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following patient profiles is at the highest risk for developing heterotopic ossification following a total hip arthroplasty?

. A 65-year-old female with developmental dysplasia of the hip
. A 70-year-old male with a history of ipsilateral heterotopic ossification
. A 55-year-old female with rheumatoid arthritis
. A 60-year-old male with avascular necrosis of the femoral head
. A 75-year-old female with osteoporosis

Correct Answer & Explanation

. A 70-year-old male with a history of ipsilateral heterotopic ossification

Explanation

A prior history of heterotopic ossification (HO) in the ipsilateral hip is the most significant risk factor for HO following total hip arthroplasty. Other high-risk groups include men with hypertrophic osteoarthritis, ankylosing spondylitis, and diffuse idiopathic skeletal hyperostosis (DISH).

Question 6452

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old male with a history of ankylosing spondylitis undergoes a primary total hip arthroplasty. He is scheduled for prophylactic radiation therapy to prevent heterotopic ossification. What is the optimal dose and timing for this intervention?

. 700 cGy as a single fraction within 24 hours preoperatively or 72 hours postoperatively
. 1000 cGy divided over 5 days preoperatively
. 700 cGy as a single fraction given 1 week postoperatively
. 2000 cGy in divided doses starting 24 hours postoperatively
. 700 cGy given exclusively 48 hours preoperatively

Correct Answer & Explanation

. 700 cGy as a single fraction within 24 hours preoperatively or 72 hours postoperatively

Explanation

Radiation therapy for HO prophylaxis is highly effective when given as a single 700 cGy fraction. It must be administered within 24 hours prior to surgery or within 72 hours postoperatively to effectively prevent mesenchymal stem cell differentiation into osteoblasts.

Question 6453

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following patient scenarios carries the highest risk for developing heterotopic ossification following a total hip arthroplasty if prophylactic measures are not utilized?

. A 65-year-old female with primary osteoarthritis
. A 40-year-old male with a history of ankylosing spondylitis
. A 70-year-old female with developmental dysplasia of the hip
. A 55-year-old male with avascular necrosis of the femoral head
. A 60-year-old female with rheumatoid arthritis

Correct Answer & Explanation

. A 40-year-old male with a history of ankylosing spondylitis

Explanation

High-risk factors for heterotopic ossification (HO) following THA include a history of ankylosing spondylitis, previous HO in the ipsilateral or contralateral hip, diffuse idiopathic skeletal hyperostosis (DISH), Paget's disease, and post-traumatic arthritis.

Question 6454

Topic: 3. Adult Reconstruction (Hip & Knee)

A 16-year-old male presents with progressive swelling and pain in his left forearm. Radiographs demonstrate near-complete osteolysis of the radius. Biopsy confirms Gorham-Stout disease. Which of the following serum laboratory profiles (Calcium, Phosphorus, Alkaline Phosphatase) is most characteristic of this condition?

. Elevated Calcium, Decreased Phosphorus, Elevated Alkaline Phosphatase
. Normal Calcium, Normal Phosphorus, Elevated Alkaline Phosphatase
. Decreased Calcium, Elevated Phosphorus, Normal Alkaline Phosphatase
. Normal Calcium, Normal Phosphorus, Normal Alkaline Phosphatase
. Elevated Calcium, Normal Phosphorus, Normal Alkaline Phosphatase

Correct Answer & Explanation

. Normal Calcium, Normal Phosphorus, Normal Alkaline Phosphatase

Explanation

Gorham-Stout disease (massive osteolysis) is a localized condition of abnormal lymphatic and vascular proliferation leading to progressive bone resorption. Unlike metabolic bone diseases, systemic laboratory values (calcium, phosphorus, and alkaline phosphatase) are typically completely normal.

Question 6455

Topic: 3. Adult Reconstruction (Hip & Knee)
A 60-year-old female presents with restricted hip range of motion 1 year after a right total hip arthroplasty. Radiographs reveal heterotopic ossification extending from the pelvis to the proximal femur, leaving a radiolucent gap of 0.5 cm between the opposing bone surfaces. According to the Brooker classification, what is the grade of her heterotopic ossification?
. Class I
. Class II
. Class III
. Class IV
. Class V

Correct Answer & Explanation

. Class III

Explanation

In the Brooker classification for HO, Class III is defined as bone islands extending from the pelvis or femur that reduce the space between opposing bone surfaces to less than 1 cm. Class IV represents true bony ankylosis.

Question 6456

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with advanced Paget's disease is scheduled for a total knee arthroplasty due to severe secondary osteoarthritis. Which of the following is a recognized surgical challenge specific to this condition?

. High risk of intraoperative joint dislocation
. Severe osteopenia leading to component subsidence
. Increased bleeding and difficulty preparing sclerotic bone
. High incidence of postoperative heterotopic ossification
. Rapid postoperative osteolysis

Correct Answer & Explanation

. Increased bleeding and difficulty preparing sclerotic bone

Explanation

Total joint arthroplasty in Pagetic bone is challenged by hypervascularity (increased bleeding) in the lytic/mixed phases and extreme hardness of the bone in the sclerotic phase, making reaming and cuts difficult.

Question 6457

Topic: 3. Adult Reconstruction (Hip & Knee)

An orthopedic surgeon is planning open reduction and internal fixation for a displaced subtrochanteric femur fracture in a 35-year-old patient with osteopetrosis. Which of the following technical challenges is most likely to be encountered during surgery?

. Massive, uncontrollable intraoperative hemorrhage
. Rapid implant loosening due to severe localized osteolysis
. Frequent drill bit breakage and excessively hard, brittle bone
. Inability to achieve adequate regional anesthesia
. Extremely rapid fracture callus formation causing joint contractures

Correct Answer & Explanation

. Frequent drill bit breakage and excessively hard, brittle bone

Explanation

Bone in osteopetrosis is extremely dense, hard, and brittle ('marble bone'), making internal fixation technically difficult. Surgeons frequently encounter drill bit breakage, overheating of equipment, and iatrogenic fracturing during hardware placement.

Question 6458

Topic: Total Hip Arthroplasty (THA)

A patient uses a cane in the contralateral hand to relieve pain from unilateral hip osteoarthritis. By what biomechanical mechanism does this intervention primarily decrease the hip joint reaction force on the affected side?

. Increasing the moment arm of the hip abductor musculature
. Creating a counter-moment that reduces the required force of the affected hip abductors
. Directly decreasing the body weight moment arm by shifting the center of gravity laterally
. Increasing the total compressive force through the pelvis
. Shifting the center of mass towards the affected hip

Correct Answer & Explanation

. Creating a counter-moment that reduces the required force of the affected hip abductors

Explanation

Using a cane in the contralateral hand creates an upward ground reaction force with a long moment arm to the affected hip. This generates a counter-moment that significantly reduces the force required by the affected hip abductors, thereby exponentially decreasing the total hip joint reaction force.

Question 6459

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total hip arthroplasty, the surgeon decides to use a femoral stem with increased lateral offset. What is the primary biomechanical consequence of this adjustment?

. Decreases the resting tension of the abductor musculature
. Increases the joint reaction force across the hip joint
. Increases the moment arm of the hip abductors
. Shifts the center of gravity of the body medially
. Increases the risk of bony impingement during abduction

Correct Answer & Explanation

. Increases the moment arm of the hip abductors

Explanation

Increasing femoral offset extends the distance from the center of rotation to the line of action of the abductor muscles. This increased moment arm improves abductor mechanical advantage, thereby reducing the required muscle force and decreasing overall joint reaction forces.

Question 6460

Topic: Total Hip Arthroplasty (THA)

A 10-year-old girl is evaluated for a leg length discrepancy (LLD). According to standard growth charts and multiplier methods, at approximately what age do normal girls achieve 50% of their mature lower extremity length?

. 1 year
. 2 years
. 3 years
. 4 years
. 5 years

Correct Answer & Explanation

. 3 years

Explanation

Girls typically reach 50% of their final mature lower extremity length at approximately 3 years of age, whereas boys reach this milestone at approximately 4 years of age.

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