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4. Pediatrics MCQs

Practice Set 27 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 521

Topic: Pediatric Hip

On an infant hip ultrasound used to evaluate developmental dysplasia of the hip (DDH), the alpha angle is defined by the intersection of the baseline (iliac wing) and which other structure?

. The bony roof of the acetabulum
. The cartilaginous roof (labrum)
. The femoral head center
. The triradiate cartilage
. The joint capsule

Correct Answer & Explanation

. The bony roof of the acetabulum

Explanation

The alpha angle measures the bony roof of the acetabulum and is formed by the intersection of the baseline (parallel to the iliac wing) and the bony roof line. An alpha angle greater than 60 degrees is considered normal.

Question 522

Topic: Pediatric Hip

According to the Herring lateral pillar classification for Legg-Calve-Perthes disease, a patient in Group C has what characteristic radiographic finding?

. No involvement of the lateral pillar
. >50% of the lateral pillar height maintained
. <50% of the lateral pillar height maintained
. Complete collapse of the central pillar only
. Extrusion of the femoral head beyond the acetabulum

Correct Answer & Explanation

. <50% of the lateral pillar height maintained

Explanation

In the Herring lateral pillar classification, Group C is characterized by the maintenance of less than 50% of the normal lateral pillar height. This group has the poorest prognosis and highest risk of secondary osteoarthritis.

Question 523

Topic: Pediatric Hip

While treating a 6-week-old infant with developmental dysplasia of the hip (DDH) using a Pavlik harness, you note the infant lacks active knee extension on the treated side. What is the most likely cause?

. Avascular necrosis of the femoral head
. Excessive hip abduction in the harness
. Excessive hip flexion in the harness
. Development of a septic hip
. Normal physiologic variant at this age

Correct Answer & Explanation

. Excessive hip flexion in the harness

Explanation

Excessive hip flexion in a Pavlik harness can lead to compression of the femoral nerve against the rim of the pelvis, causing a transient femoral nerve palsy. Excessive abduction, on the other hand, is classically associated with avascular necrosis.

Question 524

Topic: Pediatric Hip

Prophylactic pinning of the contralateral hip in a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE) is most strongly indicated in which of the following scenarios?

. A 14-year-old male with a BMI of 30
. A 10-year-old female with hypothyroidism
. An 11-year-old male with a history of minor trauma
. A 13-year-old female with an acute-on-chronic slip
. A 15-year-old male with a stable slip

Correct Answer & Explanation

. A 10-year-old female with hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in SCFE is recommended for patients with underlying endocrine or metabolic disorders (like hypothyroidism or renal osteodystrophy) due to the very high risk of bilateral involvement.

Question 525

Topic: Pediatric Hip

In Legg-Calve-Perthes disease, the Herring Lateral Pillar classification is used to determine prognosis. At what stage of the disease is this classification most accurately applied?

. Initial phase
. Fragmentation phase
. Reossification phase
. Healed phase
. Prior to symptom onset

Correct Answer & Explanation

. Fragmentation phase

Explanation

The Herring Lateral Pillar classification evaluates the height of the lateral third of the capital femoral epiphysis on an AP radiograph. It is most accurately and reliably applied during the early fragmentation phase.

Question 526

Topic: Pediatric Hip

A 13-year-old obese male presents with an unstable slipped capital femoral epiphysis (SCFE). Following in situ pinning, he develops severe, progressive restriction of hip motion without signs of infection. Radiographs show joint space narrowing. What is the most likely diagnosis?

. Avascular necrosis
. Chondrolysis
. Septic arthritis
. Implant failure
. Femoroacetabular impingement

Correct Answer & Explanation

. Chondrolysis

Explanation

Chondrolysis involves rapid, progressive destruction of the articular cartilage. It is a known complication of SCFE, particularly associated with unrecognized intra-articular pin penetration, presenting with painful restriction of motion.

Question 527

Topic: 4. Pediatrics

A 3-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip. During a follow-up visit, the infant is noted to have a femoral nerve palsy. What is the most appropriate next step in management?

. Continue the harness and observe for spontaneous recovery
. Discontinue the harness temporarily until nerve function returns
. Adjust the anterior straps to increase hip flexion
. Switch immediately to a rigid abduction orthosis
. Proceed to closed reduction and spica casting

Correct Answer & Explanation

. Discontinue the harness temporarily until nerve function returns

Explanation

Femoral nerve palsy in a Pavlik harness is typically caused by excessive hip flexion. The standard management is to remove the harness temporarily until the nerve recovers, which usually resolves spontaneously.

Question 528

Topic: Pediatric Hip

In a 12-year-old boy presenting with a unilateral slipped capital femoral epiphysis (SCFE), prophylactic pinning of the contralateral asymptomatic hip is most strongly indicated if the patient has which of the following concomitant conditions?

. Body mass index greater than the 95th percentile
. Hypothyroidism
. Male gender
. African American descent
. Retroverted acetabulum

Correct Answer & Explanation

. Hypothyroidism

Explanation

Endocrine disorders, such as hypothyroidism or renal osteodystrophy, significantly increase the risk of bilateral SCFE. Prophylactic pinning of the contralateral hip is strongly recommended in these atypical or syndromic cases.

Question 529

Topic: 4. Pediatrics

In a 6-year-old child with Legg-Calve-Perthes disease, which of the following radiographic "head-at-risk" signs is most indicative of a poor prognosis?

. Gage sign
. Coxa magna
. Medial joint space narrowing
. Sclerosis of the acetabulum
. Presence of a purely anterior physeal cyst

Correct Answer & Explanation

. Gage sign

Explanation

The Gage sign, a V-shaped radiolucency in the lateral portion of the epiphysis and adjacent metaphysis, is one of Catterall's "head-at-risk" signs. It indicates lateral extrusion and carries a poor prognosis.

Question 530

Topic: 4. Pediatrics

Platelet calmodulin levels correlate with which of the following phenomena:

. Progressive adolescent idiopathic scoliosis
. Progressive Scheuermann kyphosis
. Progressive slipped capital epiphysis
. Bilateral Legg-Perthes disease
. Progressive clubfoot

Correct Answer & Explanation

. Progressive adolescent idiopathic scoliosis

Explanation

Platelets contain actin and myosin and, therefore, have some features similar to skeletal muscle. C almodulin is a calcium-binding receptor protein that regulates intracellular calcium. Platelet calmodulin levels are increased in progressive adolescent idiopathic scoliosis.

Question 531

Topic: 4. Pediatrics

The majority of pediatric pedestrian-vehicle injuries occur in which time period:

. 12 AM to 5 AM
. 5 AM to 10 AM
. 10 AM to 3 PM
. 3 PM to 8 PM
. 8 PM to 12 PM

Correct Answer & Explanation

. 3 PM to 8 PM

Explanation

The majority (54%) of pediatric pedestrian-vehicle accidents occur from 3 pm to 8 pm. This time period may coincide with walks home from school, after-school play, and high traffic volume.

Question 532

Topic: 4. Pediatrics

Which of the following demographic factors places a child at increased risk of pedestrian vs vehicle trauma:

. Female gender
. Younger than 5 years old
. 5 to 9 years old
. 10 to 14 years old
. 15 to 19 years old

Correct Answer & Explanation

. 5 to 9 years old

Explanation

Male gender and age 5 to 9 years old are factors that place children at increased risk of being struck by a vehicle.

Question 533

Topic: 4. Pediatrics

Which of the following factors determines the treatment for a child with tibial hemimelia:

. The presence of a patella
. The length of the fibula
. The presence of a proximal tibial remnant
. The status of the cruciate ligaments
. The status of the menisci

Correct Answer & Explanation

. The presence of a proximal tibial remnant

Explanation

When treating a child with tibial hemimelia, the surgeon must decide whether to attempt to reconstruct the knee or perform a disarticulation. The determining factor is whether there is a proximal tibial remnant.

Question 534

Topic: Pediatric Hip

In which of the following clinical scenarios is prophylactic in situ pinning of the contralateral hip most strongly indicated in a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE)?

. A 14-year-old boy with a BMI of 30
. A 10-year-old girl with primary hypothyroidism
. A 13-year-old boy with a Southwick slip angle of 30 degrees
. A 12-year-old girl with an acute-on-chronic slip
. A 15-year-old boy with closed triradiate cartilages

Correct Answer & Explanation

. A 10-year-old girl with primary hypothyroidism

Explanation

Prophylactic contralateral pinning is highly recommended for patients with an endocrine disorder (like hypothyroidism or renal osteodystrophy) or those who are very young (<10 years), due to the high risk of contralateral slip.

Question 535

Topic: Pediatric Hip

According to the Herring Lateral Pillar classification for Legg-Calve-Perthes disease, which of the following radiographic findings defines a Group C hip?

. No involvement of the lateral pillar
. Greater than 50% of lateral pillar height maintained
. Less than 50% of lateral pillar height maintained
. Extensive metaphyseal cysts
. Presence of a subchondral crescent sign

Correct Answer & Explanation

. Less than 50% of lateral pillar height maintained

Explanation

The Herring classification assesses the height of the lateral pillar on the AP pelvis radiograph during the fragmentation stage. Group C is defined by the lateral pillar maintaining less than 50% of its original height, indicating a poor prognosis.

Question 536

Topic: Pediatric Hip

A 3-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the follow-up visit, the infant exhibits an absence of active knee extension. Which of the following is the most appropriate next step in management?

. Perform a closed reduction and spica casting
. Adjust the harness to increase hip flexion
. Discontinue the Pavlik harness immediately
. Add a hip abduction brace
. Continue current treatment as this is a transient normal finding

Correct Answer & Explanation

. Discontinue the Pavlik harness immediately

Explanation

Absence of active knee extension indicates a femoral nerve palsy, a known complication of excessive hip flexion in a Pavlik harness. The harness must be discontinued or significantly adjusted immediately to prevent permanent damage.

Question 537

Topic: Pediatric Lower Extremity

When utilizing the Ponseti method for the correction of idiopathic clubfoot, which deformity should be addressed first?

. Equinus
. Varus
. Adductus
. Cavus
. Internal tibial torsion

Correct Answer & Explanation

. Cavus

Explanation

The Ponseti method follows the CAVE sequence: Cavus, Adductus, Varus, Equinus. Cavus is corrected first by elevating the first ray to supinate the forefoot, aligning it with the midfoot.

Question 538

Topic: 4. Pediatrics

A 6-year-old child sustains a displaced extension-type supracondylar humerus fracture. After closed reduction and percutaneous pinning, the hand remains pink and warm, but the radial pulse is absent on Doppler. What is the most appropriate management?

. Immediate exploration of the brachial artery
. Observation and hospital admission for serial neurovascular checks
. Remove the pins and perform an open reduction
. Perform a sympathetic ganglion block
. Obtain an emergent CT angiogram

Correct Answer & Explanation

. Observation and hospital admission for serial neurovascular checks

Explanation

A "pulseless, pink hand" following adequate reduction and stabilization of a supracondylar humerus fracture is generally observed closely. Collateral circulation is sufficient for viability, and the pulse often returns within days.

Question 539

Topic: 4. Pediatrics

A neonate is diagnosed with Osteogenesis Imperfecta Type II. This lethal condition is most commonly caused by a mutation resulting in the substitution of which of the following amino acids in the collagen triple helix?

. Proline
. Lysine
. Glycine
. Hydroxyproline
. Glutamate

Correct Answer & Explanation

. Glycine

Explanation

Osteogenesis Imperfecta is typically caused by mutations in the COL1A1 or COL1A2 genes. The most severe forms involve a substitution for glycine, the smallest amino acid, which disrupts the tight coiling of the collagen type I triple helix.

Question 540

Topic: 4. Pediatrics

A 5-year-old child with spastic quadriplegic cerebral palsy is found to have a migration percentage of 45% on a screening AP pelvis radiograph. Which of the following is the most appropriate surgical intervention?

. Adductor tenotomy alone
. Varus derotational osteotomy (VDRO) with or without pelvic osteotomy
. Observation and repeat radiograph in 6 months
. Botulinum toxin injection to the adductors
. Total hip arthroplasty

Correct Answer & Explanation

. Varus derotational osteotomy (VDRO) with or without pelvic osteotomy

Explanation

In cerebral palsy, a migration percentage >40% typically indicates a progressive hip subluxation that will not resolve with soft tissue releases alone. Bony reconstruction with a VDRO, often combined with a pelvic osteotomy, is the standard of care.

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