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4. Pediatrics MCQs

Practice Set 126 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 2501

Topic: Pediatric Hip

A 12-year-old boy undergoes in-situ screw fixation for a unilateral SCFE. Which of the following patient profiles represents an absolute indication for prophylactic pinning of the asymptomatic contralateral hip?

. Presence of an endocrinopathy or renal osteodystrophy
. Unilateral unstable SCFE in a 14-year-old
. Patient weight greater than the 95th percentile alone
. Male sex and tall stature
. Presence of a mild, chronic slip

Correct Answer & Explanation

. Presence of an endocrinopathy or renal osteodystrophy

Explanation

Prophylactic pinning of the contralateral hip is strongly indicated in patients with endocrine disorders (e.g., hypothyroidism) or renal osteodystrophy due to the extremely high risk of bilateral involvement. Other indications often include age less than 10 or inability to follow up.

Question 2502

Topic: 4. Pediatrics

A 4-month-old infant with DDH has been treated in a Pavlik harness for 3 weeks. At the current visit, the mother notes that the child is not kicking the left leg as much. On exam, the infant lacks active knee extension on the left. Injury to which nerve is the most likely cause?

. Sciatic nerve
. Obturator nerve
. Superior gluteal nerve
. Femoral nerve
. Inferior gluteal nerve

Correct Answer & Explanation

. Femoral nerve

Explanation

Femoral nerve palsy in a Pavlik harness is caused by excessive hip flexion. It presents with absent active knee extension, and the harness should be adjusted or temporarily discontinued until nerve function recovers.

Question 2503

Topic: Pediatric Hip

In a typical patient with a slipped capital femoral epiphysis (SCFE), the relative displacement of the proximal femoral epiphysis in relation to the femoral neck is most accurately described as:

. Anterior and superior
. Posterior and superior
. Medial and anterior
. Anterior and inferior
. Posterior and inferior

Correct Answer & Explanation

. Posterior and inferior

Explanation

In SCFE, the epiphysis remains structurally housed within the acetabulum while the femoral neck displaces anteriorly and superiorly. Thus, the relative position of the epiphysis to the neck is posterior and inferior.

Question 2504

Topic: 4. Pediatrics

A 9-year-old child with a BMI in the 10th percentile presents with bilateral, insidious-onset hip pain. Radiographs confirm bilateral mild SCFE. Given the patient's atypical presentation, which of the following laboratory tests is most critical to obtain?

. Complete blood count with differential
. Hemoglobin A1c
. Rheumatoid factor
. Thyroid-stimulating hormone and free T4
. Serum calcium and phosphorus

Correct Answer & Explanation

. Thyroid-stimulating hormone and free T4

Explanation

Atypical SCFE (patients < 10 years old, thin habitus, or bilateral simultaneous presentation) strongly suggests an underlying endocrine or metabolic disorder. Hypothyroidism is the most common endocrine etiology, requiring evaluation of TSH and free T4.

Question 2505

Topic: 4. Pediatrics

A newborn presents in the nursery with bilateral severe clubfeet, knee recurvatum, and rigid, irreducible dislocated hips. Evaluation reveals multiple joint contractures and decreased muscle mass. Which of the following is the most likely diagnosis?

. Ehlers-Danlos syndrome
. Marfan syndrome
. Arthrogryposis multiplex congenita
. Achondroplasia
. Osteogenesis imperfecta

Correct Answer & Explanation

. Arthrogryposis multiplex congenita

Explanation

Arthrogryposis multiplex congenita (amyoplasia) is characterized by multiple rigid congenital joint contractures, including teratologic hip dislocations that are typically irreducible without extensive soft tissue release.

Question 2506

Topic: Pediatric Upper Extremity & Spine

A 15-year-old girl is diagnosed with adolescent idiopathic scoliosis (Lenke Type 1). Her main thoracic curve measures 58 degrees and is flexible on side-bending. Her pulmonary function tests are normal. What is the standard of care for this patient?

. Anterior spinal fusion
. Posterior spinal fusion
. Observation
. Thoracolumbosacral orthosis (TLSO)
. Vertebral body tethering

Correct Answer & Explanation

. Posterior spinal fusion

Explanation

In a skeletally mature or nearly mature patient with a thoracic AIS curve exceeding 50 degrees, posterior spinal fusion with segmental instrumentation is the standard surgical treatment to halt progression and correct deformity.

Question 2507

Topic: Pediatric Hip

When evaluating an anteroposterior (AP) pelvis radiograph for a suspected SCFE, a line is drawn along the superior border of the femoral neck. In a normal hip, this line should intersect a portion of the lateral epiphysis. What is the name of this line?

. Perkin's line
. Hilgenreiner's line
. Klein's line
. Shenton's line
. Ilioischial line

Correct Answer & Explanation

. Klein's line

Explanation

Klein's line is drawn along the superior margin of the femoral neck on the AP radiograph. In a normal hip, it intersects the lateral portion of the femoral head epiphysis; in SCFE, it often passes superior to the epiphysis (Trethowan's sign).

Question 2508

Topic: Pediatric Hip

A 6-week-old female with developmental dysplasia of the hip (DDH) has been treated with a Pavlik harness for 4 weeks. Repeat ultrasound reveals a persistent dislocation with an alpha angle of 35 degrees. What is the most appropriate next step in management?

. Continue Pavlik harness for 4 more weeks
. Switch to a rigid abduction orthosis or perform a closed reduction
. Perform immediate open reduction
. Perform a varus derotational osteotomy
. Discontinue bracing and observe until 6 months of age

Correct Answer & Explanation

. Switch to a rigid abduction orthosis or perform a closed reduction

Explanation

If a Pavlik harness fails to reduce a dislocated hip after 3 to 4 weeks, it should be discontinued to avoid "Pavlik harness disease" (posterior acetabular wall damage). The next appropriate step is a trial of a rigid abduction orthosis (e.g., Ilfeld) or proceeding to closed reduction and spica casting.

Question 2509

Topic: Pediatric Hip

Which of the following patients diagnosed with a unilateral slipped capital femoral epiphysis (SCFE) is most strongly indicated for prophylactic pinning of the contralateral hip?

. A 12-year-old boy with a BMI in the 95th percentile
. A 14-year-old girl with an acute, unstable slip
. A 10-year-old boy with renal osteodystrophy
. A 13-year-old boy with a 40-degree chronic slip
. A 15-year-old girl who has begun menstruating

Correct Answer & Explanation

. A 10-year-old boy with renal osteodystrophy

Explanation

Prophylactic contralateral pinning is highly recommended for patients with underlying endocrinopathies, metabolic disorders (like renal osteodystrophy), or previous radiation therapy due to the extremely high risk of bilateral involvement. Idiopathic cases have a lower risk, and contralateral pinning is assessed on a case-by-case basis.

Question 2510

Topic: Pediatric Upper Extremity & Spine

A 12-year-old girl presents with adolescent idiopathic scoliosis (AIS). Her radiographs demonstrate a right thoracic curve of 35 degrees. She is premenarchal and Risser 0. Which of the following is the most appropriate management?

. Observation with repeat radiographs in 6 months
. Physical therapy and core strengthening
. Full-time TLSO bracing
. Posterior spinal fusion
. Anterior spinal tethering

Correct Answer & Explanation

. Full-time TLSO bracing

Explanation

In a premenarchal, Risser 0 patient with an AIS curve between 25 and 40 degrees, the risk of progression is very high (often >60%). Full-time bracing (e.g., TLSO) is indicated to alter the natural history and prevent progression to the surgical range.

Question 2511

Topic: Pediatric Hip

A 13-year-old boy presents to the emergency department unable to bear weight on his left leg after a minor fall. Radiographs confirm a severe slipped capital femoral epiphysis (SCFE). Which of the following complications is he at the highest risk for developing compared to a patient with a stable SCFE?

. Chondrolysis
. Femoroacetabular impingement
. Osteonecrosis
. Leg length discrepancy
. Premature osteoarthritis

Correct Answer & Explanation

. Osteonecrosis

Explanation

An unstable SCFE (defined by the inability to bear weight even with crutches) has a significantly higher risk of osteonecrosis (up to 50%) compared to a stable SCFE. Urgent but careful reduction and fixation, or a modified Dunn procedure, is often required.

Question 2512

Topic: 4. Pediatrics

During the ultrasound evaluation of a 4-week-old infant suspected of having DDH, the alpha angle is measured. This angle is formed by the intersection of the iliac bone line and which of the following structures?

. The triradiate cartilage
. The cartilaginous acetabular roof
. The bony acetabular roof
. The femoral head center
. The labrum

Correct Answer & Explanation

. The bony acetabular roof

Explanation

The alpha angle is formed by the intersection of the baseline (ilium) and the bony acetabular roof. It represents the bony coverage of the femoral head and should normally be greater than 60 degrees.

Question 2513

Topic: Pediatric Hip

A 12-year-old boy with a BMI of 32 complains of left knee pain for 2 months. Knee examination is normal. When his left hip is passively flexed to 90 degrees, the thigh deviates into obligatory external rotation. What is the pathomechanics of the underlying disorder?

. Anterior and superior displacement of the femoral neck relative to the epiphysis
. Posterior and inferior displacement of the femoral neck relative to the epiphysis
. Anterior and superior displacement of the epiphysis relative to the femoral neck
. Posterior and superior displacement of the epiphysis relative to the acetabulum
. Anterolateral displacement of the epiphysis relative to the femoral neck

Correct Answer & Explanation

. Anterior and superior displacement of the femoral neck relative to the epiphysis

Explanation

In a Slipped Capital Femoral Epiphysis (SCFE), the epiphysis remains securely positioned in the acetabulum while the metaphysis (femoral neck) displaces anteriorly and superiorly. This spatial shift results in the characteristic obligatory external rotation during hip flexion.

Question 2514

Topic: Pediatric Hip

An infant treated with a Pavlik harness for DDH develops a femoral nerve palsy. Which of the following positioning errors is the most likely cause?

. Excessive abduction
. Inadequate abduction
. Excessive flexion
. Inadequate flexion
. Excessive internal rotation

Correct Answer & Explanation

. Excessive flexion

Explanation

Excessive flexion in a Pavlik harness (typically >120 degrees) can cause compression of the femoral nerve against the inguinal ligament, leading to a temporary palsy. Excessive abduction is associated with a different severe complication: avascular necrosis.

Question 2515

Topic: Pediatric Hip

A 4-week-old female infant is diagnosed with developmental dysplasia of the hip (DDH) and placed in a Pavlik harness. During a follow-up visit, the parents report that the child is not actively kicking her left leg. On examination, the knee lacks active extension, but ankle motion is intact. What is the most likely cause of this finding?

. Avascular necrosis of the femoral head
. Femoral nerve palsy due to hyperflexion
. Obturator nerve palsy due to hyperabduction
. Sciatic nerve palsy due to extreme extension
. Inferior dislocation of the hip

Correct Answer & Explanation

. Femoral nerve palsy due to hyperflexion

Explanation

Hyperflexion of the hip in a Pavlik harness can compress the femoral nerve against the rim of the pelvis, leading to transient femoral nerve palsy. Hyperabduction is historically associated with avascular necrosis.

Question 2516

Topic: Pediatric Hip

Which of the following conditions is considered an absolute indication for prophylactic in situ pinning of the contralateral asymptomatic hip in a patient presenting with unilateral Slipped Capital Femoral Epiphysis (SCFE)?

. Obesity with a BMI > 95th percentile
. Age greater than 14 years at presentation
. Renal osteodystrophy
. Male gender
. African American descent

Correct Answer & Explanation

. Renal osteodystrophy

Explanation

Endocrinopathies and metabolic disorders, such as renal osteodystrophy and hypothyroidism, carry a nearly 100% risk of bilateral SCFE. Prophylactic pinning of the contralateral hip is highly recommended in these populations.

Question 2517

Topic: 4. Pediatrics
A 2-year-old child presents with a congenital scoliosis secondary to a fully segmented hemivertebra at T8. Which of the following is the most critical screening test to perform in this patient?
. Pulmonary function tests
. Renal ultrasound
. CT of the chest
. Brain MRI
. DEXA scan

Correct Answer & Explanation

. Renal ultrasound

Explanation

Congenital scoliosis is frequently associated with VACTERL anomalies. A renal ultrasound and an MRI of the entire spine are essential to rule out genitourinary anomalies and intraspinal dysraphism.

Question 2518

Topic: Pediatric Hip

A 12-year-old obese boy presents to the emergency department with severe groin pain after a minor fall and is completely unable to bear weight. Radiographs confirm a slipped capital femoral epiphysis. According to the Loder classification, what is the primary complication associated with his inability to bear weight?

. Chondrolysis
. Avascular necrosis
. Femoroacetabular impingement
. Premature physeal closure
. Coxa vara

Correct Answer & Explanation

. Avascular necrosis

Explanation

The inability to bear weight defines an unstable SCFE in the Loder classification. Unstable slips carry a much higher risk of avascular necrosis (up to 50%) compared to stable slips.

Question 2519

Topic: Pediatric Upper Extremity & Spine

A 13-year-old female presents with adolescent idiopathic scoliosis. She is pre-menarchal and Risser 0. Her right thoracic curve measures 32 degrees on standing PA radiographs. What is the most appropriate management?

. Observation and follow-up in 6 months
. Physical therapy and core strengthening
. Thoracolumbosacral orthosis (TLSO) bracing
. Posterior spinal fusion
. Vertical Expandable Prosthetic Titanium Rib (VEPTR) insertion

Correct Answer & Explanation

. Thoracolumbosacral orthosis (TLSO) bracing

Explanation

TLSO bracing is indicated for growing children (Risser 0-2, pre-menarchal) with curves between 25 and 45 degrees to prevent curve progression.

Question 2520

Topic: Pediatric Hip

On a coronal ultrasound of a 6-week-old infant's hip, the alpha angle measures 48 degrees and the beta angle measures 70 degrees. According to the Graf classification, what does this alpha angle indicate?

. Normal hip development
. Shallow acetabular roof (dysplasia)
. Superior subluxation
. Irreducible dislocation
. Labral inversion

Correct Answer & Explanation

. Shallow acetabular roof (dysplasia)

Explanation

An alpha angle less than 60 degrees indicates a shallow bony acetabular roof, typical of developmental dysplasia. A normal alpha angle is 60 degrees or greater.

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