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4. Pediatrics MCQs

Practice Set 175 of 334

This practice set contains high-yield board review questions covering key concepts in 4. Pediatrics. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 3481

Topic: Pediatric Hip

A 48-year-old female with bilateral Crowe Type IV developmental dysplasia of the hip (DDH) is undergoing a primary total hip arthroplasty. The preoperative plan is to place the acetabular component in the anatomic true acetabulum. The femoral head is currently dislocated 6 cm superior to the true acetabulum. Which adjunctive surgical technique is most critical to perform during this reconstruction to avoid a devastating postoperative neurologic complication?

. Prophylactic complete release of the sciatic nerve from the greater sciatic notch to the popliteal fossa
. A subtrochanteric femoral shortening osteotomy
. Release of the psoas tendon directly at the lesser trochanter
. Use of a constrained acetabular liner to prevent nerve-related instability
. Anterior transposition of the sciatic nerve over the anterior column

Correct Answer & Explanation

. A subtrochanteric femoral shortening osteotomy

Explanation

In Crowe Type IV DDH, the hip is completely dislocated superiorly. Restoring the hip center to the anatomic (true) acetabulum will require significant lengthening of the leg (in this case, >4-5 cm). This acute lengthening places profound stretch on the sciatic nerve, risking severe and potentially irreversible palsy. To prevent this, a subtrochanteric shortening osteotomy is typically necessary to safely reduce the hip without excessively stretching the sciatic nerve.

Question 3482

Topic: Pediatric Hip

A 45-year-old woman with Crowe type IV developmental dysplasia of the hip (DDH) is undergoing total hip arthroplasty. The femoral head is completely dislocated superiorly. During reconstruction, the surgeon intends to place the acetabular component in the true acetabulum. To safely reduce the hip and mitigate the risk of neurologic injury, which of the following surgical adjuncts is most frequently required?

. Acetabular roof structural bone grafting
. Femoral shortening subtrochanteric osteotomy
. Greater trochanteric advancement
. Adductor tenotomy alone
. Sciatic nerve release at the piriformis

Correct Answer & Explanation

. Femoral shortening subtrochanteric osteotomy

Explanation

In Crowe IV DDH, the hip has been dislocated superiorly for decades, leading to severe soft tissue contracture. Placing the cup in the true anatomic acetabulum requires bringing the femur down a significant distance. Attempting to reduce the hip without shortening the femur places excessive tension on the sciatic nerve. A subtrochanteric shortening osteotomy is frequently required to safely reduce the joint and prevent stretch-induced sciatic nerve palsy.

Question 3483

Topic: Pediatric Hip

A 13-year-old obese male presents with a 2-week history of right groin and knee pain. He walks with a noticeable limp but is able to bear weight. Physical examination reveals obligatory external rotation of the hip with passive flexion. Radiographs confirm a mild Slipped Capital Femoral Epiphysis (SCFE) (Figure 15). Following in situ single-screw fixation of the right hip, what is the primary clinical rationale for considering prophylactic fixation of the contralateral hip?

. To prevent the development of widespread chondrolysis
. To equalize leg lengths postoperatively by stunting contralateral growth
. To address a known 20-40% risk of contralateral slip, particularly in high-risk patients
. To reduce the risk of avascular necrosis in the ipsilateral affected hip
. To correct an underlying metabolic bone defect in the proximal femur

Correct Answer & Explanation

. To address a known 20-40% risk of contralateral slip, particularly in high-risk patients

Explanation

Patients presenting with a unilateral SCFE have a significant risk (approximately 20-40%) of developing a subsequent contralateral slip. This risk is notably higher in specific populations, including younger patients (<10 years for boys), obese patients, and those with underlying endocrinopathies (e.g., hypothyroidism). Prophylactic fixation is often discussed and implemented in these high-risk groups to prevent future displacement and the associated severe morbidity.

Question 3484

Topic: Pediatric Hip

Figure 2 shows the pelvis radiograph of a 45-year-old female with severe bilateral hip pain secondary to neglected developmental dysplasia of the hip (DDH).

She is planned for a primary right THA. The templating indicates a Crowe IV dislocation. To restore the hip's center of rotation to the true acetabulum without causing a nerve palsy, which surgical adjunct is most likely required?

. Placement of an extra-large 'jumbo' cup at the false acetabulum
. Subtrochanteric shortening osteotomy
. Prophylactic complete release of the sciatic nerve from the greater sciatic notch to the popliteal fossa
. Distal femoral extension osteotomy
. Greater trochanteric advancement

Correct Answer & Explanation

. Subtrochanteric shortening osteotomy

Explanation

Crowe Type IV DDH is characterized by a completely dislocated femoral head (>100% subluxation) with a false acetabulum formed high on the ilium. To restore normal biomechanics and leg length, the acetabular component should ideally be placed in the true acetabulum. However, pulling the femur down to this level risks stretching the sciatic nerve, potentially causing a stretch neuropraxia. Most authors recommend a subtrochanteric shortening osteotomy if the required distal translation of the femur exceeds 4 cm, mitigating the risk of sciatic nerve injury.

Question 3485

Topic: 4. Pediatrics

An 8-year-old boy presents with a limp and groin pain. Radiographs confirm the diagnosis of Legg-Calve-Perthes disease. Which of the following radiographic "head-at-risk" signs described by Catterall is considered the most significant predictor of a poor long-term outcome because of its association with mechanical hinge abduction?

. Metaphyseal cystic changes
. The Gage sign
. Calcification lateral to the epiphysis
. Horizontal physical growth plate
. Subchondral stress fracture (Crescent sign)

Correct Answer & Explanation

. Calcification lateral to the epiphysis

Explanation

Catterall's 'head-at-risk' signs indicate a worse prognosis in Legg-Calve-Perthes disease. They include lateral subluxation of the femoral head, calcification lateral to the epiphysis, Gage sign (V-shaped radiolucency in the lateral portion of the physis), metaphyseal cysts, and a horizontal physis. Calcification lateral to the epiphysis implies extrusion of the femoral head outside the acetabulum. This extruded segment can impinge on the lateral acetabular margin during abduction, leading to hinge abduction, progressive deformity, and early osteoarthritis, making it highly predictive of a poor outcome.

Question 3486

Topic: Pediatric Hip

A 13-year-old obese boy with an open triradiate cartilage undergoes in-situ pinning for a stable, moderate slipped capital femoral epiphysis (SCFE) using a single cannulated screw. Six months postoperatively, he complains of severe, unrelenting global hip pain and marked stiffness. Radiographs demonstrate a sudden, severe narrowing of the joint space. What is the most likely diagnosis?

. Osteonecrosis of the femoral head
. Chondrolysis
. Implant failure and hardware penetration
. Contralateral slipped capital femoral epiphysis
. Septic arthritis

Correct Answer & Explanation

. Chondrolysis

Explanation

Chondrolysis is a devastating complication of SCFE characterized by acute onset of severe pain, marked limitation of motion (stiffness), and rapid loss of articular cartilage space (typically > 50% loss or joint space < 3 mm) on radiographs. While it can occur idiopathically in SCFE, it is strongly associated with unrecognized intra-articular pin penetration. Osteonecrosis (AVN) is more commonly associated with unstable SCFEs and typically presents with segmental collapse and sclerosis, rather than acute global joint space loss.

Question 3487

Topic: Pediatric Hip

A 6-week-old female infant is diagnosed with developmental dysplasia of the hip. Ultrasound confirms a completely dislocated but reducible left hip. She is treated with a Pavlik harness. After 3 weeks of strict harness wear, a repeat ultrasound reveals that the left hip remains persistently dislocated. What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 3 weeks to allow for capsular stretching
. Adjust the Pavlik harness to increase flexion to 120 degrees and maximal abduction
. Abandon the Pavlik harness and transition to a rigid abduction orthosis or perform a closed reduction and spica casting
. Proceed immediately to an open reduction via an anterior approach
. Perform a percutaneous adductor tenotomy and immediately reapply the Pavlik harness

Correct Answer & Explanation

. Abandon the Pavlik harness and transition to a rigid abduction orthosis or perform a closed reduction and spica casting

Explanation

If a dislocated hip fails to reduce after 3 to 4 weeks of appropriate Pavlik harness wear, the harness must be abandoned. Prolonged use of the harness with a persistently dislocated hip can lead to 'Pavlik harness disease,' causing damage to the posterior lip of the acetabulum, worsening dysplasia, and increasing the risk of avascular necrosis. The next appropriate step is typically a trial of a rigid abduction orthosis (e.g., Ilfeld splint) or moving directly to a closed reduction and spica casting under anesthesia.

Question 3488

Topic: Pediatric Hip

A 28-year-old female presents with anterior groin pain that is exacerbated by sitting in a low chair. An AP pelvis radiograph is obtained.

The radiograph demonstrates the anterior rim of the acetabulum crossing over the posterior rim in the superior aspect of the joint. This specific radiographic finding is most strongly associated with which of the following pathomorphologies?

. Coxa profunda
. Cam-type femoroacetabular impingement
. Acetabular retroversion
. Excessive femoral anteversion
. Developmental dysplasia of the hip (DDH)

Correct Answer & Explanation

. Acetabular retroversion

Explanation

The finding described is the 'crossover sign,' which is the hallmark radiographic indicator of acetabular retroversion. In a normal acetabulum (anteverted), the anterior rim line lies medial to the posterior rim line. When the anterior rim crosses lateral to the posterior rim, it indicates focal or global retroversion, leading to anterior overcoverage and pincer-type femoroacetabular impingement.

Question 3489

Topic: Pediatric Hip

A 12-year-old obese male presents with an unstable left slipped capital femoral epiphysis (SCFE). Which of the following is an absolute indication for prophylactic pinning of the contralateral hip?

. Obesity (BMI > 95th percentile)
. Age less than 10 years at presentation
. Endocrine disorder such as hypothyroidism
. Family history of SCFE
. Male sex

Correct Answer & Explanation

. Endocrine disorder such as hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip is strongly indicated in patients with underlying endocrine or metabolic disorders (e.g., hypothyroidism). These conditions carry an extremely high risk of bilateral involvement.

Question 3490

Topic: Pediatric Hip

On a pelvic radiograph of a 6-month-old female with developmental dysplasia of the hip, the proximal femoral metaphysis is located superior to Hilgenreiner's line and lateral to Perkin's line. What is the interpretation of Shenton's line in this patient?

. It will be continuous and intact
. It will be broken
. It evaluates the anterior-posterior displacement
. It is formed by the superior border of the obturator foramen and the lateral border of the ilium
. It is only visible on a frog-leg lateral view

Correct Answer & Explanation

. It will be broken

Explanation

Shenton's line is a radiographic arc drawn along the inferior border of the superior pubic ramus and the medial border of the proximal femur. In a dislocated hip, Shenton's line is disrupted or broken.

Question 3491

Topic: Pediatric Hip
A 7-year-old boy is diagnosed with Legg-Calvรฉ-Perthes disease. According to the Herring classification, he has >50% loss of height of the lateral pillar. What is his Herring classification and corresponding prognosis?
. Herring Group A; Excellent prognosis
. Herring Group B; Good prognosis with containment
. Herring Group C; Poor prognosis, high risk of aspherical head
. Herring Group B/C; Intermediate prognosis
. Herring Group D; Severely delayed bone age

Correct Answer & Explanation

. Herring Group C; Poor prognosis, high risk of aspherical head

Explanation

The Herring classification assesses the remaining height of the lateral pillar of the femoral head. Group C indicates >50% loss of lateral pillar height and carries a poor prognosis, frequently resulting in an aspherical head.

Question 3492

Topic: Pediatric Hip

A 12-year-old obese boy is diagnosed with a severe, chronic slipped capital femoral epiphysis (SCFE) on the left side. What is the primary indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Body mass index > 95th percentile
. Open triradiate cartilage
. Southwick slip angle > 50 degrees on the affected side
. Presence of underlying endocrine disorder
. Age < 10 years

Correct Answer & Explanation

. Presence of underlying endocrine disorder

Explanation

The presence of an underlying endocrine disorder (e.g., hypothyroidism) or renal failure is an absolute indication for prophylactic pinning of the contralateral hip in SCFE due to the high risk of bilateral involvement.

Question 3493

Topic: Pediatric Hip

Which of the following conditions is considered an absolute contraindication to metal-on-metal hip resurfacing arthroplasty?

. Male gender
. End-stage osteoarthritis
. Chronic renal failure
. Body mass index > 35
. History of Legg-Calve-Perthes disease

Correct Answer & Explanation

. Chronic renal failure

Explanation

Hip resurfacing utilizes metal-on-metal bearings which release cobalt and chromium ions. Chronic renal failure is an absolute contraindication because these metal ions are primarily excreted by the kidneys, risking severe systemic toxicity.

Question 3494

Topic: Pediatric Hip

A 4-month-old infant with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. The parents incorrectly tighten the anterior straps, resulting in hyperflexion of the hips beyond 120 degrees. This positioning most significantly increases the risk of which complication?

. Acetabular dysplasia
. Femoral nerve palsy
. Sciatic nerve palsy
. Avascular necrosis of the femoral head
. Inferior hip dislocation

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Hyperflexion of the hips in a Pavlik harness can severely compress the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy. Excessive abduction, conversely, is the primary risk factor for avascular necrosis of the femoral head.

Question 3495

Topic: Pediatric Hip

In a child diagnosed with Legg-Calve-Perthes disease, which of the following is clinically recognized as the most important prognostic factor for long-term hip joint survival?

. Gender of the patient
. Age at the onset of symptoms
. Family history of the disease
. Patient's body mass index
. Sidedness of hip involvement

Correct Answer & Explanation

. Age at the onset of symptoms

Explanation

Age at the onset of symptoms is the most significant prognostic factor in Legg-Calve-Perthes disease. Children who develop the condition before the age of 6 to 8 years have a significantly better prognosis due to a greater remaining potential for biological remodeling.

Question 3496

Topic: Pediatric Hip

Prophylactic pinning of the contralateral, asymptomatic hip is most strongly indicated in a patient with a slipped capital femoral epiphysis (SCFE) who presents with which of the following concurrent conditions?

. Body mass index greater than the 95th percentile
. An underlying endocrine disorder such as hypothyroidism
. Age greater than 14 years at presentation
. African American descent
. Male gender

Correct Answer & Explanation

. An underlying endocrine disorder such as hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip is highly recommended in patients with SCFE associated with an underlying endocrine disorder or metabolic condition (e.g., hypothyroidism, renal osteodystrophy). These patients have an exceptionally high risk of developing bilateral disease.

Question 3497

Topic: 4. Pediatrics

A 13-year-old male baseball pitcher complains of right shoulder pain during the acceleration phase of throwing. He has tenderness over the proximal humerus. Radiographs show widening of the proximal humeral physis compared to the contralateral side. What is the most appropriate initial treatment?

. Corticosteroid injection into the subacromial space
. Immediate surgical pinning of the physis
. Physical therapy focusing on aggressive capsular stretching
. Absolute rest from throwing for 6-12 weeks
. Diagnostic shoulder arthroscopy

Correct Answer & Explanation

. Absolute rest from throwing for 6-12 weeks

Explanation

Little League shoulder is a stress fracture (epiphysiolysis) of the proximal humeral physis. Treatment consists of complete cessation of throwing (rest) for 6 to 12 weeks, followed by a gradual return-to-throwing program.

Question 3498

Topic: 4. Pediatrics

A 13-year-old elite baseball pitcher presents with worsening right shoulder pain occurring strictly during the cocking phase of throwing. AP radiographs reveal widening and irregularity of the proximal humeral physis. What is the underlying pathophysiology?

. Avascular necrosis of the humeral head
. Diaphyseal stress fracture of the humerus
. Salter-Harris I stress fracture of the proximal humeral physis
. Subacromial impingement syndrome
. Degenerative SLAP tear

Correct Answer & Explanation

. Salter-Harris I stress fracture of the proximal humeral physis

Explanation

Little League shoulder is a fatigue failure of the proximal humeral physis, representing a Salter-Harris I stress fracture. It is caused by repetitive rotational and distraction forces exerted during the throwing motion.

Question 3499

Topic: 4. Pediatrics

A 13-year-old highly competitive baseball pitcher presents with insidious onset of proximal shoulder pain in his throwing arm. Radiographs reveal widening of the proximal humeral physis and sclerosis of the metaphysis. What is the definitive initial management?

. Immediate surgical epiphysiodesis
. Corticosteroid injection into the physis
. Complete rest from throwing for up to 3 months
. Physical therapy emphasizing aggressive rotator cuff strengthening while continuing to pitch
. Diagnostic arthroscopy

Correct Answer & Explanation

. Complete rest from throwing for up to 3 months

Explanation

Little League Shoulder (proximal humeral epiphysiolysis) is an overuse injury caused by repetitive rotational torque. The standard of care is absolute cessation of throwing for typically 3 months until symptoms resolve and the physis shows radiographic healing.

Question 3500

Topic: 4. Pediatrics

A 13-year-old Little League pitcher presents with gradually worsening lateral shoulder pain. Radiographs demonstrate widening and irregularity of the proximal humeral physis. What is the most appropriate initial management?

. Surgical epiphysiodesis
. Open reduction and internal fixation
. Absolute rest from throwing for 3 months
. Corticosteroid injection into the subacromial space
. Arthroscopic superior labral repair

Correct Answer & Explanation

. Absolute rest from throwing for 3 months

Explanation

Little League Shoulder is a stress fracture of the proximal humeral physis. The definitive initial treatment is strict cessation of throwing for typically 3 months, followed by a gradual return-to-throw program once asymptomatic.

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