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4. Pediatrics MCQs

Practice Set 100 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 1981

Topic: Pediatric Hip



A 13-year-old boy with a BMI of 32 presents with right knee pain and an antalgic limp. Examination reveals obligatory external rotation with hip flexion. He is diagnosed with a slipped capital femoral epiphysis (SCFE). Which of the following is considered an indication for prophylactic pinning of the contralateral asymptomatic hip?

. Patient age greater than 15 years
. Severe degree of slip on the affected side
. Presence of an underlying endocrine disorder (e.g., hypothyroidism)
. Male sex
. Associated knee pain

Correct Answer & Explanation

. Presence of an underlying endocrine disorder (e.g., hypothyroidism)

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is generally indicated in patients with underlying endocrine disorders (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency), previous pelvic radiation, or highly skeletal immature patients (e.g., chronological age < 10 for boys, modified Oxford bone age < 16). These populations have a very high risk of bilateral involvement. Age > 15, male sex, and slip severity alone are not strict indications for prophylactic pinning.

Question 1982

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy sustains a completely displaced (Gartland Type III) supracondylar humerus fracture. Radiographs reveal that the distal fracture fragment is displaced posterolaterally. Given this specific displacement pattern, which nerve is at the highest risk of injury?
. Radial nerve
. Ulnar nerve
. Anterior interosseous nerve (AIN)
. Musculocutaneous nerve
. Axillary nerve

Correct Answer & Explanation

. Anterior interosseous nerve (AIN)

Explanation

In a posterolateral displaced supracondylar humerus fracture, the proximal fragment is driven anteromedially. This specific vector threatens the median nerve (and its anterior interosseous nerve branch) as well as the brachial artery. Conversely, in a posteromedial displacement pattern, the proximal fragment displaces anterolaterally, putting the radial nerve at the greatest risk.

Question 1983

Topic: Pediatric Hip

A 6-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 infant is no longer actively kicking her left leg, though she cries when the leg is manipulated. Examination shows absent active knee extension on the left. The harness strap positioning is likely causing compression of which structure?

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

Correct Answer & Explanation

. Femoral nerve

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically occurring when the anterior straps are pulled too tight, placing the hips in excessive hyperflexion. The infant presents with decreased active knee extension (decreased kicking). It is usually transient and resolves with temporary removal or adjustment of the harness to decrease hip flexion.

Question 1984

Topic: 4. Pediatrics

Within articular cartilage, which structural landmark separates the deep uncalcified zone from the calcified cartilage zone and serves as the physical barrier to the transport of nutrients from the subchondral bone?

. Lamina splendens
. Tidemark
. Cement line
. Physis
. Subchondral bone plate

Correct Answer & Explanation

. Tidemark

Explanation

The tidemark is the histological boundary that separates the deep zone of true, uncalcified articular cartilage from the calcified zone. It acts as a strict barrier to nutrient diffusion from the subchondral bone, meaning that the uncalcified zones of articular cartilage rely almost entirely on diffusion from synovial fluid for their nutritional demands. The cement line separates the calcified cartilage from the subchondral bone.

Question 1985

Topic: 4. Pediatrics

A 2-week-old male infant presents with idiopathic congenital talipes equinovarus (clubfoot).

The pediatric orthopedist plans to initiate Ponseti serial casting. According to the Ponseti method, what is the correct sequential order of deformity correction?

. Cavus, Adductus, Varus, Equinus
. Equinus, Varus, Adductus, Cavus
. Adductus, Cavus, Equinus, Varus
. Varus, Equinus, Cavus, Adductus
. Cavus, Varus, Adductus, Equinus

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method involves sequential correction of the deformities in congenital clubfoot following the mnemonic CAVE: Cavus (corrected first by elevating the first ray), Adductus (corrected by abducting the forefoot around the fixed head of the talus), Varus (which corrects simultaneously with forefoot abduction), and finally Equinus (which often requires a percutaneous Achilles tenotomy as the final step).

Question 1986

Topic: Pediatric Hip

An 11-year-old male with a body mass index (BMI) in the 99th percentile presents with left hip pain and an obligatory external rotation during hip flexion. He is diagnosed with a slipped capital femoral epiphysis (SCFE). Which of the following is considered an absolute indication for prophylactic pinning of the contralateral, asymptomatic hip?

. Obesity with BMI > 95th percentile
. Hypothyroidism
. Age of 11 years
. Male sex
. African American race

Correct Answer & Explanation

. Hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is generally indicated in patients with underlying endocrine disorders (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy), patients undergoing previous radiation therapy, and in very young patients (typically less than 10 years of age for boys). Obesity, while a risk factor for SCFE, is not an absolute indication for prophylactic contralateral pinning.

Question 1987

Topic: 4. Pediatrics
A 2-year-old girl is brought to the pediatric orthopedic clinic by her parents due to worsening bilateral bowlegs. Radiographs reveal a metaphyseal-diaphyseal angle of 18 degrees on the right and 19 degrees on the left, along with medial physeal beaking. She is diagnosed with infantile Blount disease (tibia vara). What is the most appropriate initial management?
. Observation and reassurance
. Knee-ankle-foot orthoses (KAFOs)
. Proximal tibial valgus osteotomy
. Hemiepiphysiodesis of the lateral proximal tibia
. Guided growth using tension band plates

Correct Answer & Explanation

. Knee-ankle-foot orthoses (KAFOs)

Explanation

In infantile Blount disease, a metaphyseal-diaphyseal angle (MDA) greater than 16 degrees predicts progression of the deformity, distinguishing it from physiologic bowing. For children under the age of 3 with Langenskiöld Stage I or II and an MDA > 16 degrees, bracing with a knee-ankle-foot orthosis (KAFO) is the recommended initial management. Surgical intervention (osteotomy or guided growth) is indicated if bracing fails, or typically if the child is over 3-4 years old with advanced stages.

Question 1988

Topic: Pediatric Hip
A 6-year-old boy presents with a 3-month history of a painless limp. Radiographs demonstrate fragmentation and increased sclerosis of the capital femoral epiphysis, consistent with Legg-Calvé-Perthes disease. The lateral pillar classification (Herring) is widely utilized to determine the prognosis of this condition. This classification system relies on evaluating the height of which specific portion of the capital femoral epiphysis on an anteroposterior (AP) radiograph?
. The anterior third
. The central third
. The lateral third
. The posterior third
. The medial third

Correct Answer & Explanation

. The lateral third

Explanation

The Herring Lateral Pillar Classification is assessed on the AP radiograph during the fragmentation stage of Legg-Calvé-Perthes disease. It evaluates the height of the lateral third of the capital femoral epiphysis compared to the contralateral normal side. Group A has no lateral pillar involvement; Group B has >50% lateral pillar height maintained; Group C has <50% of the lateral pillar height maintained. The condition of the lateral pillar is the most significant prognostic factor for late femoral head deformity.

Question 1989

Topic: Pediatric Hip

A 13-year-old obese boy presents with left thigh pain and an obligatory external rotation of the left hip during flexion.

He is diagnosed with a Slipped Capital Femoral Epiphysis (SCFE). Which of the following is considered an absolute indication for prophylactic pinning of the contralateral asymptomatic hip?

. Endocrine disorder (e.g., hypothyroidism)
. Age greater than 15 years
. Male gender
. Obesity (BMI greater than 95th percentile)
. Modified Klein line intersection on the normal hip

Correct Answer & Explanation

. Endocrine disorder (e.g., hypothyroidism)

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but generally recommended in patients with a high risk of developing a contralateral slip. Absolute indications or strong recommendations include the presence of an underlying endocrine disorder (hypothyroidism, panhypopituitarism, renal osteodystrophy) or prior radiation therapy, as these patients have a much higher rate of bilateral involvement.

Question 1990

Topic: 4. Pediatrics

You are treating an infant with idiopathic congenital talipes equinovarus using the Ponseti method.

What is the correct sequence of deformity correction?

. Equinus, Varus, Adduction, Cavus
. Cavus, Adduction, Varus, Equinus
. Adduction, Cavus, Varus, Equinus
. Varus, Cavus, Adduction, Equinus
. Cavus, Equinus, Adduction, Varus

Correct Answer & Explanation

. Cavus, Adduction, Varus, Equinus

Explanation

The Ponseti method corrects clubfoot deformities in the mnemonic order CAVE: Cavus (corrected first by elevating the first ray to supinate the forefoot and align it with the hindfoot), followed by Adduction, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy).

Question 1991

Topic: Pediatric Hip

A 13-year-old female undergoes in situ percutaneous pinning for a stable slipped capital femoral epiphysis (SCFE). Six months postoperatively, she presents with progressive hip stiffness, pain, and a severely restricted range of motion. Anteroposterior radiographs of the pelvis demonstrate concentric joint space narrowing of the affected hip to less than 3 mm. What is the most likely diagnosis?

. Avascular necrosis of the femoral head
. Chondrolysis
. Hardware failure
. Femoroacetabular impingement
. Septic arthritis

Correct Answer & Explanation

. Chondrolysis

Explanation

Chondrolysis is a devastating complication of SCFE, characterized by acute cartilage necrosis resulting in progressive joint space narrowing (typically defined as <3 mm), severe stiffness, and pain. It is strongly associated with unrecognized intra-articular pin penetration during fixation. While avascular necrosis (AVN) is another severe complication, it typically presents with segmental collapse and sclerosis of the femoral head rather than isolated symmetric joint space narrowing.

Question 1992

Topic: 4. Pediatrics

When applying the Ponseti casting method for the conservative management of congenital talipes equinovarus (clubfoot), the deformity is corrected in a specific sequential order. Which component of the deformity is corrected LAST?

. Cavus
. Adductus
. Varus
. Equinus

Correct Answer & Explanation

. Equinus

Explanation

The Ponseti method utilizes serial casting to gradually stretch contracted tissues. The sequence of correction follows the acronym CAVE: Cavus (corrected first by supinating the forefoot and elevating the first ray to align with the hindfoot), Adductus, Varus, and finally Equinus. Equinus is corrected last to prevent a rocker-bottom deformity, and it frequently requires a percutaneous Achilles tenotomy to achieve adequate dorsiflexion.

Question 1993

Topic: Pediatric Hip

A 9-year-old boy with panhypopituitarism and a BMI of 32 presents with right knee pain and a limp. He is diagnosed with a right slipped capital femoral epiphysis (SCFE).

Which of the following is the strongest indication for prophylactic in situ pinning of his contralateral asymptomatic left hip?

. His BMI greater than 30.
. His age at presentation and endocrine disorder.
. The degree of slip on the symptomatic right side.
. The presence of right knee pain instead of hip pain.
. His male gender.

Correct Answer & Explanation

. His age at presentation and endocrine disorder.

Explanation

Prophylactic pinning of the contralateral hip in SCFE is recommended for patients at very high risk for a subsequent bilateral slip. High-risk factors include underlying endocrine disorders (e.g., hypothyroidism, panhypopituitarism, renal osteodystrophy) and young age at presentation (typically <10 years old for boys or <11 for girls).

Question 1994

Topic: Pediatric Hip

In a 7-year-old boy diagnosed with Legg-Calve-Perthes disease (LCPD), AP pelvis radiographs are obtained during the fragmentation phase.

The lateral pillar of the femoral head maintains exactly 40% of its normal height. According to the Herring lateral pillar classification, what group does this patient fall into, and what is the general prognosis?

. Group A; good prognosis without surgical intervention.
. Group B; fair prognosis, may benefit from containment surgery.
. Group C; poor prognosis, high risk of aspherical head and premature arthritis.
. Group B/C border; excellent prognosis.
. Group A; poor prognosis requiring immediate osteotomy.

Correct Answer & Explanation

. Group C; poor prognosis, high risk of aspherical head and premature arthritis.

Explanation

The Herring lateral pillar classification evaluates the height of the lateral third of the femoral head on an AP radiograph during the fragmentation stage. Group A: no loss of height. Group B: >50% lateral pillar height maintained. Group C: <50% lateral pillar height maintained. Group C patients have a poor prognosis, frequently resulting in an aspherical head and early-onset osteoarthritis.

Question 1995

Topic: 4. Pediatrics

A 13-year-old boy presents with left knee pain and a limp for 3 weeks. Examination reveals obligatory external rotation of the left hip with passive hip flexion. Radiographs demonstrate a mild slip.

He is scheduled for in situ pinning. What is the primary goal of this procedure?

. To anatomically reduce the slip
. To prevent further slippage
. To restore normal hip biomechanics
. To prevent avascular necrosis
. To delay the onset of chondrolysis

Correct Answer & Explanation

. To prevent further slippage

Explanation

The primary goal of in situ pinning for SCFE is to stabilize the physis and prevent further slippage, allowing the physis to close. Attempting to reduce a chronic slip increases the risk of avascular necrosis.

Question 1996

Topic: 4. Pediatrics

An 18-month-old girl presents with a painless limp and leg length discrepancy. Radiographs show a dislocated left hip with a pseudoacetabulum. What is the most appropriate treatment?

. Pavlik harness
. Closed reduction and spica casting
. Open reduction, pelvic osteotomy, and femoral shortening osteotomy
. Observation
. Physical therapy

Correct Answer & Explanation

. Open reduction, pelvic osteotomy, and femoral shortening osteotomy

Explanation

In a walking child over 18 months of age with a completely dislocated hip, open reduction is almost always required. A femoral shortening osteotomy reduces pressure on the cartilage to prevent AVN, and a pelvic osteotomy (e.g., Salter or Pemberton) is usually needed to correct acetabular dysplasia.

Question 1997

Topic: 4. Pediatrics

The Ponseti method for the treatment of congenital idiopathic clubfoot (talipes equinovarus) dictates a specific sequence of deformity correction. Which of the following represents the correct sequence of correction?

. Equinus, varus, adductus, cavus
. Cavus, adductus, varus, equinus
. Adductus, varus, cavus, equinus
. Cavus, varus, equinus, adductus
. Varus, cavus, adductus, equinus

Correct Answer & Explanation

. Cavus, adductus, varus, equinus

Explanation

The acronym CAVE is used to remember the sequence of correction in the Ponseti method: Cavus (by elevating the first ray), Adductus, Varus, and finally Equinus (often requiring a percutaneous Achilles tenotomy).

Question 1998

Topic: Pediatric Hip

A 12-year-old obese male presents with left thigh pain and obligatory external rotation during hip flexion.

What is the most widely accepted absolute indication for prophylactic in situ pinning of the asymptomatic contralateral hip in the setting of Slipped Capital Femoral Epiphysis (SCFE)?

. Modified Oxford bone age of 14
. Acute, unstable slip on the affected side
. Underlying endocrinopathy or renal osteodystrophy
. Patient weight greater than the 95th percentile
. Southwick slip angle greater than 50 degrees on the affected side

Correct Answer & Explanation

. Underlying endocrinopathy or renal osteodystrophy

Explanation

While the decision to prophylactically pin the contralateral hip in SCFE is often debated, absolute indications generally include patients with a known endocrinopathy (such as hypothyroidism or growth hormone deficiency) or renal osteodystrophy, as they have a significantly higher risk of a sequential slip. Other relative indications include young age (e.g., modified Oxford bone age < 16) or an inability to follow up, but endocrine disorders represent the most universally accepted absolute indication.

Question 1999

Topic: Pediatric Lower Extremity

An infant is treated with serial casting for idiopathic clubfoot using the Ponseti method.

During the manipulative correction of the adductus and varus deformities, the physician's thumb must apply counter-pressure to which specific osseous structure to serve as a fulcrum?

. Medial aspect of the navicular
. Lateral aspect of the calcaneocuboid joint
. Head of the talus
. Sustentaculum tali
. Lateral malleolus

Correct Answer & Explanation

. Head of the talus

Explanation

In the Ponseti method, the key to successful manipulation is applying counter-pressure with the thumb on the lateral aspect of the head of the talus. Pressure on the calcaneocuboid joint or lateral malleolus blocks abduction of the calcaneus, preventing correction of the heel varus and forefoot adductus.

Question 2000

Topic: Pediatric Hip

A 2-month-old female is diagnosed with Developmental Dysplasia of the Hip (DDH). Ultrasound confirms a dislocated but reducible left hip. The orthopedist elects to initiate treatment with a Pavlik harness rather than rigid spica casting. What is the primary physiological advantage of using a Pavlik harness in this scenario?

. Lower risk of femoral nerve palsy
. Decreased risk of avascular necrosis of the femoral head
. Superior correction of acetabular version
. Faster rate of concentric reduction
. Prevention of residual pelvic obliquity

Correct Answer & Explanation

. Decreased risk of avascular necrosis of the femoral head

Explanation

The primary advantage of the Pavlik harness over rigid immobilization (like a spica cast) in an infant is a significantly decreased risk of avascular necrosis (AVN) of the femoral head. The harness maintains the hip in the 'safe zone' of Ramsey (flexion and limited, non-forced abduction) while allowing active motion. Rigid casting, especially in excessive abduction (frog-leg position), forces the medial circumflex femoral artery against the labrum, leading to ischemia and AVN.

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