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4. Pediatrics MCQs

Practice Set 139 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 2761

Topic: 4. Pediatrics

A 14-year-old boy sustains a Salter-Harris type II fracture of the distal femur during a football game. He undergoes an anatomic closed reduction and casting. Which of the following complications is most commonly associated with this specific injury?

. Nonunion
. Osteomyelitis
. Physeal growth arrest
. Avascular necrosis of the femoral condyle
. Patellofemoral instability

Correct Answer & Explanation

. Nonunion

Explanation

Distal femur physeal fractures, particularly Salter-Harris II fractures, have a notoriously high rate of physeal growth arrest, reported to be up to 50% or more. This is due to the highly undulating nature of the distal femoral physis, which sustains significant crush injury (Salter-Harris V type damage) even during a shear or bending mechanism. Close radiographic follow-up is required to monitor for leg length discrepancies and angular deformities.

Question 2762

Topic: 4. Pediatrics
A 2-year-old boy presents with an anterolateral bowing of the tibia and a pseudoarthrosis. Physical examination reveals multiple café-au-lait spots on his trunk and axillary freckling. Which of the following conditions is most strongly associated with this orthopedic presentation?
. Osteogenesis imperfecta
. Neurofibromatosis type 1
. Fibrous dysplasia
. Cleidocranial dysplasia
. Achondroplasia

Correct Answer & Explanation

. Neurofibromatosis type 1

Explanation

Congenital pseudarthrosis of the tibia (CPT) with anterolateral bowing is highly associated with Neurofibromatosis type 1 (NF1). Approximately 50% of patients with CPT have NF1. The presence of multiple café-au-lait spots and axillary freckling further supports this diagnosis. Management is surgical and notoriously difficult, often requiring excision of the pseudarthrosis, bone grafting, and intramedullary stabilization.

Question 2763

Topic: Pediatric Lower Extremity

During the Ponseti casting technique for the treatment of idiopathic clubfoot, the foot is sequentially manipulated to correct the complex deformity. Which of the following describes the correct sequential order of deformity correction?

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

Correct Answer & Explanation

. Equinus, Varus, Adductus, Cavus

Explanation

The Ponseti method utilizes a specific sequence to correct clubfoot deformity, remembered by the acronym CAVE: Cavus, Adductus, Varus, and Equinus. The cavus is corrected first by supinating the forefoot and elevating the first ray to align it with the hindfoot. Then, the adductus and varus are corrected simultaneously by abducting the foot around the head of the talus. Finally, the equinus is corrected, often requiring a percutaneous Achilles tenotomy.

Question 2764

Topic: 4. Pediatrics

A 7-year-old girl with spastic quadriplegic cerebral palsy presents for routine surveillance. She is non-ambulatory (GMFCS Level V). Radiographs of the pelvis demonstrate a right hip migration percentage of 55%, coxa valga, and an intact Shenton's line on the left. She has mild pain with hip abduction. What is the most appropriate management?

. Observation and repeat radiographs in 6 months
. Adductor and iliopsoas tenotomies
. Proximal femoral varus derotation osteotomy (VDRO) and pelvic osteotomy
. Total hip arthroplasty
. Proximal femoral resection (Girdlestone procedure)

Correct Answer & Explanation

. Observation and repeat radiographs in 6 months

Explanation

In children with cerebral palsy, hip surveillance is critical. Soft tissue releases (adductor tenotomies) are prophylactic and most effective when the migration percentage (MP) is less than 30-40% and the child is young (typically <4-5 years). Once the migration percentage exceeds 40-50% in a 7-year-old, soft tissue releases alone have a high failure rate. Bony reconstructive surgery, specifically a proximal femoral varus derotation osteotomy (VDRO) combined with a pelvic osteotomy (such as a Dega or San Diego), is required to safely contain the hip and halt progression of subluxation to dislocation.

Question 2765

Topic: Pediatric Hip

A 9-month-old girl presents for an initial orthopedic evaluation. She has asymmetric thigh folds and limited abduction of the left hip. Ultrasound at 6 weeks of age was reportedly abnormal but the parents did not follow up. Current radiographs demonstrate a dislocated left hip with a dysplastic acetabulum. What is the most appropriate next step in management?

. Trial of Pavlik harness for 3 weeks
. Closed reduction and hip spica casting
. Open reduction and femoral shortening osteotomy
. Open reduction and pelvic osteotomy
. Observation until age 2, followed by open reduction

Correct Answer & Explanation

. Trial of Pavlik harness for 3 weeks

Explanation

The patient has late-presenting developmental dysplasia of the hip (DDH). The Pavlik harness is generally indicated for infants under 6 months of age; its success rate drops significantly and the risk of complications rises in older infants. For children aged 6 to 18 months, the gold standard initial treatment is closed reduction and application of a hip spica cast, often preceded by or performed concurrently with an adductor tenotomy. Open reduction with or without pelvic/femoral osteotomies is typically reserved for failures of closed reduction or primary treatment in children older than 18 months.

Question 2766

Topic: 4. Pediatrics
A 13-year-old girl sustains a twisting injury to her right ankle. Radiographs reveal a Salter-Harris III fracture of the anterolateral distal tibia. This specific fracture pattern (Juvenile Tillaux fracture) occurs as a direct result of the asymmetrical closure of the distal tibial physis. Which of the following describes the last portion of the distal tibial physis to close?
. Central
. Anteromedial
. Posteromedial
. Anterolateral
. Posterolateral

Correct Answer & Explanation

. Anterolateral

Explanation

The distal tibial physis closes in a predictable sequence over an 18-month period, typically between ages 12 and 15. The sequence begins centrally, progresses medially, then posteromedially, and finally closes anterolaterally. Because the anterolateral physis is the last to fuse, the anterior inferior tibiofibular ligament (AITFL) can avulse this open anterolateral portion of the epiphysis during an external rotation injury, leading to the classic juvenile Tillaux fracture (Salter-Harris III).

Question 2767

Topic: Pediatric Hip

An 11-year-old boy with a BMI in the 99th percentile presents with left knee pain and a limp for 4 weeks. Radiographs show a mild, stable slipped capital femoral epiphysis (SCFE) of the left hip. The parents ask about the risk to the other hip. Which of the following is the strongest indication for prophylactic pinning of the contralateral, asymptomatic right hip?

. Age of 11 years
. Obesity
. Male sex
. Underlying endocrine disorder
. Presence of knee pain rather than hip pain

Correct Answer & Explanation

. Age of 11 years

Explanation

The decision to perform prophylactic pinning of the contralateral hip in a unilateral SCFE patient requires balancing the risks of surgery against the risk of a subsequent slip. Patients with underlying endocrine disorders (such as hypothyroidism, growth hormone deficiency, or panhypopituitarism) or renal osteodystrophy have an extremely high risk (up to 100%) of bilateral involvement, making an underlying endocrine disorder a strong, widely accepted indication for prophylactic pinning. Other relative indications may include young age (<10 for girls, <11 for boys) or inability to follow up.

Question 2768

Topic: Pediatric Hip

An 8-year-old boy presents with a 2-month history of a painless limp. Radiographs demonstrate sclerosis and fragmentation of the proximal femoral epiphysis consistent with Legg-Calve-Perthes disease. Which of the following is considered the most important radiographic prognostic factor for determining the final outcome of the hip?

. Degree of metaphyseal cyst formation
. Extent of lateral pillar involvement
. Presence of a subchondral fracture line (Crescent sign)
. Degree of medial joint space widening
. Premature physeal closure

Correct Answer & Explanation

. Degree of metaphyseal cyst formation

Explanation

The Herring lateral pillar classification system evaluates the height of the lateral portion of the capital femoral epiphysis on an AP pelvis radiograph during the fragmentation stage of Legg-Calve-Perthes disease. It is widely recognized as the most reliable radiographic prognostic indicator for final hip outcome. Hips in Group A (no lateral pillar involvement) have the best prognosis, while Group C (<50% lateral pillar height maintained) have the poorest outcome. Age of onset (especially >8 years) is the most significant clinical prognostic factor.

Question 2769

Topic: Pediatric Lower Extremity

A newborn male is evaluated for bilateral idiopathic clubfeet (talipes equinovarus). The treating orthopedic surgeon initiates the Ponseti method of serial casting. What is the correct physiological sequence in which the components of the deformity are systematically corrected?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method addresses the components of the clubfoot deformity in a specific sequence, easily remembered by the mnemonic CAVE: Cavus, Adductus, Varus, Equinus. The first cast corrects the cavus by supinating the forefoot to align it with the hindfoot. Subsequent casts correct the adductus and varus by gradually abducting the foot around the head of the talus. Finally, the equinus is corrected, which often requires a percutaneous Achilles tenotomy before the final cast is applied.

Question 2770

Topic: Pediatric Hip

A 12-year-old boy with a BMI of 35 presents with an acute on chronic slipped capital femoral epiphysis (SCFE) of the left hip. He undergoes uneventful in situ pinning. When considering prophylactic pinning of the contralateral right hip, which of the following is the most important risk factor for developing a subsequent SCFE?

. Male sex
. Age > 10 years at the time of presentation
. Initial slip angle > 50 degrees
. Endocrine disorder
. Family history of SCFE

Correct Answer & Explanation

. Male sex

Explanation

Prophylactic pinning of the contralateral hip in patients with a unilateral SCFE is indicated in patients with endocrine disorders (e.g., hypothyroidism, growth hormone supplementation, renal osteodystrophy), prior radiation therapy, and an age of presentation less than 10 years in boys or 11 years in girls. Male sex and family history alone do not mandate prophylactic pinning. Slip angle determines severity but not automatically contralateral risk in the absence of other specific factors.

Question 2771

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy presents with a completely displaced posteromedial supracondylar humerus fracture. Based on the direction of displacement, which nerve is at highest risk of injury?

. Median nerve
. Ulnar nerve
. Radial nerve
. Anterior interosseous nerve
. Posterior interosseous nerve

Correct Answer & Explanation

. Median nerve

Explanation

Supracondylar humerus fractures are the most common elbow fractures in children. Posteromedial displacement is the most common pattern of an extension-type supracondylar humerus fracture. In this pattern, the distal fragment goes posteromedially, causing the proximal fragment to displace anterolaterally. The radial nerve is located anterolaterally and is tethered at the lateral intermuscular septum, making it the most vulnerable structure to injury by the proximal fragment spike. The anterior interosseous nerve (AIN) is most commonly injured in posterolateral displacement.

Question 2772

Topic: Pediatric Hip

An infant is placed in a Pavlik harness for treatment of developmental dysplasia of the hip (DDH). During a follow-up visit, the parents report that the child has stopped kicking the leg. Examination reveals an absence of active knee extension on the affected side, but intact ankle dorsiflexion and plantar flexion. What is the most appropriate next step in management?

. Adjust the posterior straps to decrease hip abduction
. Adjust the anterior straps to decrease hip flexion
. Immediate surgical exploration
. Switch to a rigid abduction orthosis
. Continue harness as this is a transient normal finding

Correct Answer & Explanation

. Adjust the posterior straps to decrease hip abduction

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment for DDH. It is caused by excessive hip flexion, which can compress the femoral nerve against the rim of the pelvis. The diagnosis is made clinically by a loss of active knee extension (decreased quadriceps function) while ankle motion remains intact. Management consists of either adjusting the anterior straps to reduce hip flexion or removing the harness entirely until nerve function returns. Continuing the harness without adjustment risks permanent nerve injury.

Question 2773

Topic: Pediatric Lower Extremity

When treating idiopathic clubfoot using the Ponseti method, what is the proper sequence of deformity correction?

. Cavus, adduction, varus, equinus
. Cavus, varus, adduction, equinus
. Adduction, varus, cavus, equinus
. Equinus, cavus, adduction, varus
. Varus, cavus, adduction, equinus

Correct Answer & Explanation

. Cavus, adduction, varus, equinus

Explanation

The Ponseti method for the treatment of idiopathic clubfoot relies on a specific sequence of deformity correction summarized by the acronym CAVE: Cavus, Adduction, Varus, and Equinus. First, the cavus is corrected by elevating the first ray to align the forefoot with the hindfoot. Then, the forefoot is abducted to correct the adduction and varus simultaneously while counter-pressure is applied to the lateral aspect of the talar head. Finally, the equinus is corrected, most often requiring a percutaneous Achilles tenotomy.

Question 2774

Topic: Pediatric Hip
Which of the following is the most important prognostic factor for long-term outcome in a child with Legg-Calvé-Perthes disease?
. Age at onset of symptoms
. Degree of medial pillar collapse
. Catterall classification
. Gender of the patient
. Presence of an effusion on MRI

Correct Answer & Explanation

. Age at onset of symptoms

Explanation

In Legg-Calvé-Perthes disease, the age at the onset of symptoms is the most consistently reliable prognostic factor for final hip outcome. Children who present at less than 6 years of age have a better prognosis because they have greater potential for remodeling of the femoral head. Children presenting after 8 years of age have a worse prognosis. The other most important prognostic factor is the degree of lateral (not medial) pillar involvement according to the Herring classification.

Question 2775

Topic: 4. Pediatrics

A 5-year-old child with spastic quadriplegic cerebral palsy is evaluated in the clinic. The patient has a Gross Motor Function Classification System (GMFCS) level of V. What is the most appropriate radiographic screening protocol for hip displacement in this patient?

. AP pelvis radiograph only if the patient becomes symptomatic
. AP pelvis radiograph every 6 to 12 months
. Pelvic MRI annually
. Hip ultrasound every 6 months
. No routine screening is indicated

Correct Answer & Explanation

. AP pelvis radiograph only if the patient becomes symptomatic

Explanation

Children with cerebral palsy (CP) are at a high risk for progressive hip displacement (subluxation and dislocation) due to muscle spasticity and imbalance. The risk of hip displacement is directly correlated with the Gross Motor Function Classification System (GMFCS) level. A child with GMFCS level V is non-ambulatory and has the highest risk (over 90%) of hip displacement. Therefore, rigorous surveillance is required. The recommended screening protocol for a GMFCS level V child includes an anteroposterior (AP) pelvis radiograph every 6 to 12 months.

Question 2776

Topic: Pediatric Hip

An 11-year-old girl with a history of renal osteodystrophy presents with a 3-week history of left groin and knee pain. She is diagnosed with a moderate slipped capital femoral epiphysis (SCFE) on the left side. Her right hip is completely asymptomatic, and radiographs of the right hip are normal. What is the most appropriate management regarding the contralateral right hip?

. Observation until symptoms develop
. Prophylactic in situ pinning
. Application of a hip spica cast
. Magnetic resonance imaging to assess for a pre-slip
. Bilateral proximal femoral osteotomies

Correct Answer & Explanation

. Observation until symptoms develop

Explanation

Prophylactic in situ pinning of the contralateral hip is highly recommended in patients with SCFE associated with an underlying endocrinopathy or metabolic bone disease (such as renal osteodystrophy, hypothyroidism, or growth hormone deficiency). These patients have an extremely high rate of bilateral involvement (up to 100% in some metabolic conditions) compared to idiopathic cases. Observation is generally reserved for idiopathic cases with a reliable follow-up.

Question 2777

Topic: 4. Pediatrics

A 3-month-old infant with developmental dysplasia of the hip is being treated with a Pavlik harness. At a routine 2-week follow-up, the mother reports that the child is no longer kicking her right leg. On examination, there is an absence of active knee extension on the right side, but foot and ankle motion are preserved. What is the most likely cause of this finding?

. Avascular necrosis of the femoral head
. Femoral nerve palsy secondary to excessive hip flexion
. Sciatic nerve palsy secondary to a tight posterior strap
. Obturator nerve palsy secondary to excessive hip abduction
. Undiagnosed septic arthritis

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment and is typically caused by excessive flexion of the hips, which compresses the femoral nerve against the inguinal ligament. It manifests as a loss of active knee extension. The appropriate management is to temporarily loosen the anterior straps to decrease hip flexion, which usually allows for complete recovery of nerve function. Excessive abduction places the hip at risk for avascular necrosis (AVN).

Question 2778

Topic: 4. Pediatrics

A 7-year-old child with spastic quadriplegic cerebral palsy is evaluated for progressive left hip dysplasia. Current anteroposterior pelvis radiographs show a migration percentage of 65%, a neck-shaft angle of 155 degrees, and an intact triradiate cartilage. The articular cartilage appears well-preserved on MRI. What is the most appropriate surgical intervention?

. Bilateral adductor tenotomies alone
. Observation with botulinum toxin injections
. Varus derotational osteotomy (VDRO) of the proximal femur combined with a pelvic osteotomy
. Proximal femoral resection (Castle procedure)
. Total hip arthroplasty

Correct Answer & Explanation

. Bilateral adductor tenotomies alone

Explanation

In children with cerebral palsy and a subluxated but reconstructable hip (migration percentage > 50% and preserved cartilage), the gold standard surgical treatment is a combined one-stage reconstruction. This typically involves a varus derotational osteotomy (VDRO) of the proximal femur to correct coxa valga and excessive anteversion, combined with a pelvic osteotomy (such as a Dega or San Diego osteotomy) to correct acetabular dysplasia. Soft tissue releases are also performed concurrently. Salvage procedures like the Castle procedure are reserved for painful, chronically dislocated, and non-reconstructable hips.

Question 2779

Topic: Pediatric Hip
A 7-year-old boy is diagnosed with Legg-Calvé-Perthes disease. According to the Herring classification system, which of the following radiographic parameters evaluated during the fragmentation stage is the most reliable predictor of long-term outcome?
. The degree of metaphyseal cyst formation
. The maintenance of the height of the lateral pillar of the capital femoral epiphysis
. The presence of a subchondral fracture (crescent sign)
. The extent of lateral epiphyseal extrusion
. The early closure of the capital femoral physis

Correct Answer & Explanation

. The maintenance of the height of the lateral pillar of the capital femoral epiphysis

Explanation

The Herring Lateral Pillar Classification is based on AP radiographs during the fragmentation stage of Legg-Calvé-Perthes disease. It divides the femoral head into three pillars (medial, central, and lateral). The height of the lateral pillar is the most reliable prognostic indicator. Group A (>100% height maintained) has the best outcome, Group B (>50% maintained) has an intermediate outcome, and Group C (<50% maintained) has the worst outcome regarding future joint congruency and arthritis risk.

Question 2780

Topic: Pediatric Lower Extremity

When correcting an infant's idiopathic clubfoot deformity using the Ponseti casting technique, the deformities must be sequentially addressed. What is the correct chronological order of correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method dictates a specific sequence for the correction of the clubfoot deformity, easily remembered by the acronym CAVE: Cavus, Adductus, Varus, Equinus. The cavus is corrected first by elevating the first ray to align the forefoot with the hindfoot. Then, the adductus and varus are corrected simultaneously by abducting the midfoot around the fixed head of the talus. Finally, the equinus is corrected, often requiring a percutaneous Achilles tenotomy.

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