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4. Pediatrics MCQs

Practice Set 117 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 2321

Topic: Pediatric Hip

A 13-year-old boy is diagnosed with a stable Slipped Capital Femoral Epiphysis (SCFE) of the left hip. He undergoes in situ percutaneous pinning. What is the ideal position of the single screw in the epiphysis to provide maximum stability and minimize the risk of joint penetration?

. Center-center
. Anterior-superior
. Posterior-inferior
. Anterior-inferior
. Posterior-superior

Correct Answer & Explanation

. Center-center

Explanation

The ideal starting point and trajectory for in situ pinning of a SCFE is on the anterior aspect of the femoral neck, directed perpendicular to the physis, to end in the center-center position of the epiphysis. This position reduces the risk of in-out-in joint penetration and provides the most biomechanically stable construct for the displaced epiphysis.

Question 2322

Topic: 4. Pediatrics

A 6-week-old infant is being treated with a Pavlik harness for developmental dysplasia of the left hip (DDH). At the routine 2-week follow-up, the parents report that the child has stopped kicking the left leg. On examination, the infant exhibits absent active knee extension on the left side, although foot and ankle movements are intact. What is the most likely iatrogenic cause of this complication?

. Hyperflexion of the hip in the harness
. Hyperextension of the hip in the harness
. Hyperabduction of the hip in the harness
. Hyperadduction of the hip in the harness
. Excessive tightening of the anterior chest strap

Correct Answer & Explanation

. Hyperflexion of the hip in the harness

Explanation

The clinical presentation describes a femoral nerve palsy, which is a known complication of the Pavlik harness. It is typically caused by excessive hyperflexion of the hips, which compresses the femoral nerve against the inguinal ligament. Treatment involves adjusting the harness to decrease hip flexion or temporarily discontinuing the harness until nerve function returns. Hyperabduction of the hips, conversely, is associated with avascular necrosis (AVN) of the femoral head.

Question 2323

Topic: Pediatric Upper Extremity & Spine

When evaluating an adolescent idiopathic scoliosis (AIS) patient using the Lenke classification system, structural characteristics of the curves dictate the curve type (1-6). If a patient has a structural main thoracic curve and a structural proximal thoracic curve, but the thoracolumbar curve bends out to 10 degrees on side-bending films (non-structural), what is the correct Lenke curve type?

. Lenke Type 1 (Main Thoracic)
. Lenke Type 2 (Double Thoracic)
. Lenke Type 3 (Double Major)
. Lenke Type 4 (Triple Major)
. Lenke Type 5 (Thoracolumbar/Lumbar)

Correct Answer & Explanation

. Lenke Type 5 (Thoracolumbar/Lumbar)

Explanation

The Lenke classification for AIS is based on identifying structural curves (defined as a curve >= 25 degrees on coronal side-bending films or > 20 degrees of kyphosis on the sagittal film). Lenke Type 1 is a structural main thoracic curve only. Lenke Type 2 (Double Thoracic) has a structural proximal thoracic curve and a structural main thoracic curve, while the thoracolumbar curve is non-structural. Lenke Type 3 is a structural MT and structural TL/L. Lenke 4 has all three structural. Lenke 5 is structural TL/L only.

Question 2324

Topic: Pediatric Hip

A 13-year-old obese male presents with left groin pain and a limp. Examination reveals obligate external rotation with hip flexion. Radiographs demonstrate a severe Slipped Capital Femoral Epiphysis (SCFE) on the left side. The right hip is asymptomatic and radiographically normal. Under which of the following circumstances is prophylactic in situ pinning of the contralateral (right) hip most strongly indicated?

. Severe displacement (>50%) on the symptomatic side
. Male sex and body mass index > 99th percentile
. Presence of an underlying endocrine disorder or renal osteodystrophy
. Age greater than 14 years at the time of presentation
. A history of previous physeal fractures

Correct Answer & Explanation

. Presence of an underlying endocrine disorder or renal osteodystrophy

Explanation

While the decision to perform prophylactic contralateral pinning in SCFE is debated in idiopathic cases, the absolute indication universally recognized is the presence of an underlying endocrine or metabolic disorder (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) or previous radiation therapy. These patients have an extremely high risk (>50-80%) of bilateral involvement. Other relative indications often include young age (e.g., <10 for boys) or inability to follow up reliably.

Question 2325

Topic: 4. Pediatrics
A 4-year-old obese girl presents with bilateral genu varum. Radiographs reveal a distinct step-off and depression at the medial proximal tibial physis. She is diagnosed with Langenskiöld stage IV infantile Blount's disease. What is the most appropriate management?
. Observation and reassurance
. Treatment with Knee-Ankle-Foot Orthoses (KAFOs)
. Proximal tibial osteotomy with fibular osteotomy
. Hemiepiphysiodesis of the lateral proximal tibia
. Asymmetrical physeal distraction using an external fixator

Correct Answer & Explanation

. Proximal tibial osteotomy with fibular osteotomy

Explanation

Infantile Blount's disease presenting as Langenskiöld stage III or greater in a child older than 3 years is an absolute indication for surgery. Bracing is generally only effective for stages I and II in children under the age of 3. Proximal tibial osteotomy combined with a fibular procedure is required to correct the complex multiplanar deformity (varus, internal rotation, and procurvatum).

Question 2326

Topic: Pediatric Hip
In a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE), which of the following is considered the strongest indication for prophylactic in situ pinning of the asymptomatic contralateral hip?
. Patient age greater than 14 years in males
. Obesity (BMI > 95th percentile)
. Presence of an underlying endocrine disorder
. Severe (Grade III) slip on the affected side
. African American ethnicity

Correct Answer & Explanation

. Presence of an underlying endocrine disorder

Explanation

The risk of developing a contralateral SCFE is significantly elevated in patients with an underlying endocrine or metabolic disorder (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency). Bilateral involvement can approach 100% in these populations. Therefore, the presence of an endocrine disorder is a universally accepted indication for prophylactic pinning of the unaffected hip.

Question 2327

Topic: Pediatric Hip

A 3-month-old female is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). At her 2-week follow-up, the parents note that she has stopped kicking her left leg, and examination reveals a lack of active knee extension on the left side. This complication is most commonly caused by which of the following positioning errors?

. Excessive hip abduction
. Inadequate hip abduction
. Excessive hip flexion
. Inadequate hip flexion
. Excessive knee flexion

Correct Answer & Explanation

. Excessive hip flexion

Explanation

The infant is exhibiting signs of a femoral nerve palsy (lack of active knee extension/quadriceps function), which is a known complication of Pavlik harness treatment. It is caused by hyperflexion of the hips, which causes compression of the femoral nerve against the inguinal ligament. Excessive hip abduction, by contrast, is associated with avascular necrosis (AVN) of the femoral head.

Question 2328

Topic: Pediatric Hip

A 6-week-old female infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At her 2-week follow-up, the mother notes that the infant has stopped kicking her right leg. Examination reveals decreased active knee extension, but active hip flexion is maintained. What is the most appropriate next step in management?

. Adjust the anterior straps to increase hip flexion
. Order a stat MRI of the lumbar spine
. Continue the harness as this is a normal transient finding
. Discontinue the harness temporarily to allow nerve recovery
. Switch immediately to a closed reduction and spica casting

Correct Answer & Explanation

. Discontinue the harness temporarily to allow nerve recovery

Explanation

The infant has developed a femoral nerve palsy, a known complication of hyperflexion in a Pavlik harness. The diagnosis is clinical, marked by decreased active quadriceps function (lack of knee extension). The standard management is to temporarily discontinue the harness or significantly loosen the anterior straps to decrease hip flexion until nerve function returns, which typically resolves spontaneously.

Question 2329

Topic: Pediatric Lower Extremity

When utilizing the Ponseti method for the correction of idiopathic clubfoot, which of the following represents the correct sequence of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method corrects the components of clubfoot in a specific sequence, easily remembered by the acronym CAVE: Cavus, Adductus, Varus, and Equinus. The cavus is corrected first by elevating the first ray to align the forefoot with the hindfoot. Adductus and varus are then corrected simultaneously by abducting the foot around the talar head. Equinus is corrected last, frequently requiring a percutaneous Achilles tenotomy.

Question 2330

Topic: Pediatric Hip

A 13-year-old obese male presents with a 4-week history of right groin and thigh pain. Physical examination reveals obligatory external rotation of the right hip upon passive hip flexion. Radiographs confirm a stable Slipped Capital Femoral Epiphysis (SCFE). If single-screw in situ fixation is planned, what is the ideal position of the screw within the epiphysis to minimize complications?

. Anterosuperior
. Anteroinferior
. Posterosuperior
. Posteroinferior
. Center-center

Correct Answer & Explanation

. Center-center

Explanation

The ideal starting point and trajectory for a single-screw in situ fixation of a SCFE is perpendicular to the physis, terminating in the 'center-center' position of the epiphysis. Screws placed in the anterosuperior quadrant risk cutout and joint penetration. Screws placed posterosuperiorly risk injury to the lateral epiphyseal vessels, leading to avascular necrosis.

Question 2331

Topic: 4. Pediatrics

A 13-year-old obese boy presents with left hip pain and an obligatory external rotation of the thigh during hip flexion. He is diagnosed with a stable slipped capital femoral epiphysis (SCFE). Which of the following is a recognized strong absolute or relative indication for prophylactic pinning of the asymptomatic contralateral hip?

. Patient age greater than 14 years at presentation
. Male gender
. Presence of an underlying endocrine disorder (e.g., hypothyroidism)
. Slip angle less than 30 degrees on the affected side
. History of Osgood-Schlatter disease

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 strongly indicated in patients with underlying endocrine or metabolic disorders (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency), as these patients have a much higher rate of bilateral involvement (approaching 100%). It is also considered in young patients (< 10 years old) or when follow-up is unreliable.

Question 2332

Topic: Pediatric Hip

A 6-month-old female with developmental dysplasia of the hip (DDH) has failed 6 weeks of treatment in a Pavlik harness, with the left hip remaining persistently dislocated on ultrasound. What is the most appropriate next step in management?

. Continue Pavlik harness for an additional 6 weeks
. Transition to a rigid abduction orthosis (e.g., Ilfeld splint) for 4 weeks
. Closed reduction and spica casting under general anesthesia with intraoperative arthrogram
. Open reduction via an anterior approach with a Salter innominate osteotomy
. Observation until age 1 year, followed by open reduction

Correct Answer & Explanation

. Closed reduction and spica casting under general anesthesia with intraoperative arthrogram

Explanation

Prolonged use of a Pavlik harness in a persistently dislocated hip increases the risk of 'Pavlik harness disease' (posterior acetabular wear) and avascular necrosis. If a hip is not reduced within 3 to 4 weeks, the harness should be abandoned. The standard next step for a 6-month-old is an examination under anesthesia, arthrogram, and closed reduction with spica casting.

Question 2333

Topic: 4. Pediatrics

A 2-year-old child presents with anterolateral bowing of the tibia and a pseudoarthrosis is identified on radiographs. Which of the following gene mutations is most strongly associated with this condition?

. Mutation in the FGFR3 gene on chromosome 4
. Mutation in the COL1A1 gene on chromosome 17
. Mutation in the NF1 gene on chromosome 17
. Mutation in the COMP gene on chromosome 19
. Mutation in the RUNX2 gene on chromosome 6

Correct Answer & Explanation

. Mutation in the NF1 gene on chromosome 17

Explanation

Congenital pseudarthrosis of the tibia (CPT) is strongly associated with Neurofibromatosis type 1 (NF1). Approximately 50% of patients with CPT have NF1. NF1 is caused by a mutation in the NF1 gene on chromosome 17q11.2, which encodes neurofibromin, a tumor suppressor protein that downregulates the Ras-MAPK pathway.

Question 2334

Topic: Pediatric Hip

A 13-year-old obese male underwent in situ single-screw fixation for a stable slipped capital femoral epiphysis (SCFE). Six months postoperatively, he complains of severe hip stiffness and pain. Examination reveals a rigid hip with severe loss of motion in all planes. Radiographs show a concentric joint space narrowing of the affected hip to less than 3 mm. What is the most likely diagnosis?

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

Correct Answer & Explanation

. Chondrolysis

Explanation

Chondrolysis is an acute dissolution of articular cartilage characterized by concentric joint space narrowing (typically < 3 mm) and severe global stiffness. It is a known complication of SCFE, particularly associated with unrecognized pin penetration into the joint space, severe slips, or prolonged immobilization.

Question 2335

Topic: Pediatric Hip

A 6-week-old female infant is being treated for developmental dysplasia of the hip (DDH) with a Pavlik harness. At a follow-up visit, the mother notes the baby is no longer kicking her right leg. On examination, the infant exhibits absent active knee extension on the right side. Which nerve is most likely compressed due to improper positioning in the harness?

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

Correct Answer & Explanation

. Femoral nerve

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment, usually caused by excessive hyperflexion of the hips. It presents clinically with absent active knee extension (decreased kicking). The treatment is to temporarily discontinue or loosen the harness to allow the hip to rest in less flexion until the nerve recovers.

Question 2336

Topic: Pediatric Hip

In a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE), which of the following is considered the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Male sex
. Age greater than 14 years at presentation
. Presence of an underlying endocrine disorder
. Mild degree of slip on the symptomatic side
. Body Mass Index (BMI) greater than the 95th percentile

Correct Answer & Explanation

. Presence of an underlying endocrine disorder

Explanation

Patients with endocrine disorders (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy) or those undergoing prior radiation have a significantly higher risk of developing bilateral SCFE (up to 100% in some series). Prophylactic pinning of the contralateral hip is highly recommended in these atypical presentations.

Question 2337

Topic: Pediatric Lower Extremity

In the Ponseti method for the treatment of idiopathic clubfoot, sequential correction of the deformity components must be strictly followed to avoid creating a 'rocker-bottom' deformity. 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, Varus, Adduction, Equinus

Correct Answer & Explanation

. Cavus, Adduction, Varus, Equinus

Explanation

The mnemonic CAVE describes the correct sequence of correction in the Ponseti method: Cavus (by supinating the forefoot to align it with the hindfoot), Adduction, Varus, and finally Equinus (often requiring a percutaneous Achilles tenotomy). Premature correction of equinus leads to a rocker-bottom foot.

Question 2338

Topic: Pediatric Hip

A 4-month-old infant with Developmental Dysplasia of the Hip (DDH) has been treated with a Pavlik harness for 4 weeks. Ultrasound reveals a persistently dislocated left hip. What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 4 weeks
. Switch to a rigid abduction orthosis (e.g., Ilfeld splint)
. Perform an immediate open reduction and spica casting
. Discontinue the Pavlik harness and proceed with closed reduction and spica casting
. Perform a femoral derotation osteotomy

Correct Answer & Explanation

. Discontinue the Pavlik harness and proceed with closed reduction and spica casting

Explanation

If a dislocated hip fails to reduce after 3 to 4 weeks of proper Pavlik harness treatment, the harness must be discontinued to prevent complications such as 'Pavlik harness disease' (erosion of the posterior acetabular wall). The next standard step is closed reduction and application of a hip spica cast under general anesthesia, usually with an arthrogram.

Question 2339

Topic: Pediatric Hip

A 5-week-old female infant is treated with a Pavlik harness for developmental dysplasia of the hip (DDH) of the left side (Graf Type IV). After 4 weeks of compliant harness wear, an ultrasound demonstrates that the left hip remains completely dislocated. What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 4 weeks
. Transition to a rigid abduction orthosis (e.g., Ilfeld or von Rosen splint)
. Perform an immediate closed reduction and spica casting under general anesthesia
. Perform an open reduction via an anterior approach
. Recommend observation without bracing until the infant is 6 months old

Correct Answer & Explanation

. Transition to a rigid abduction orthosis (e.g., Ilfeld or von Rosen splint)

Explanation

If a Pavlik harness fails to achieve reduction after 3 to 4 weeks of compliant use in a young infant, it must be abandoned to prevent 'Pavlik harness disease' (damage to the posterior acetabular wall from the harness pushing the hip posteriorly). The next recommended step is typically a trial of a rigid abduction orthosis. If that fails, closed reduction and spica casting under anesthesia is indicated.

Question 2340

Topic: 4. Pediatrics

A 9-year-old Tanner stage I boy sustains a midsubstance anterior cruciate ligament (ACL) tear. He complains of recurrent instability despite 3 months of aggressive physical therapy. You recommend surgical reconstruction. Which of the following techniques minimizes the risk of physeal growth arrest in this patient?

. Transphyseal reconstruction with an 8-mm bone-patellar tendon-bone autograft
. Transphyseal reconstruction using interference screw fixation at the level of the physis
. Physeal-sparing all-epiphyseal reconstruction or an over-the-top extra-articular iliotibial band tenodesis
. Standard transphyseal hamstring graft with suspensory cortical fixation
. Primary repair of the ACL stump with rigid internal brace augmentation across the physes

Correct Answer & Explanation

. Physeal-sparing all-epiphyseal reconstruction or an over-the-top extra-articular iliotibial band tenodesis

Explanation

In prepubescent children with significant remaining growth (Tanner stage I or II, wide-open physes), physeal-sparing techniques are recommended to avoid growth arrest, leg length discrepancy, and angular deformities. These include the all-epiphyseal technique or extra-articular procedures like the modified MacIntosh (over-the-top IT band). Transphyseal techniques are typically reserved for older adolescents nearing skeletal maturity.

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