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4. Pediatrics MCQs

Practice Set 110 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 2181

Topic: Pediatric Hip

A 6-week-old female infant with developmental dysplasia of the hip (DDH) is placed in a Pavlik harness due to a positive Ortolani sign and an ultrasound alpha angle of 45 degrees. After 3 weeks of strictly compliant harness wear, ultrasound confirms the hip remains persistently dislocated. What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 3 weeks
. Switch immediately to a rigid hip abduction orthosis (e.g., Ilfeld brace)
. Perform a surgical open reduction via an anterior approach
. Perform a closed reduction and application of a hip spica cast
. Discontinue the harness and observe until the child is 6 months old

Correct Answer & Explanation

. Perform a closed reduction and application of a hip spica cast

Explanation

If a Pavlik harness fails to achieve reduction of a dislocated hip within 3 to 4 weeks, it must be discontinued to avoid 'Pavlik harness disease' (damage to the posterior acetabular wall) and to prevent femoral nerve palsy. The standard next step for a persistently dislocated hip failing Pavlik harness treatment in an infant is closed reduction under general anesthesia and application of a hip spica cast.

Question 2182

Topic: 4. Pediatrics

A 3-year-old girl is evaluated for worsening bilateral lower extremity bowing. Standing radiographs reveal a metaphyseal-diaphyseal angle (Drennan angle) of 18 degrees. Which specific radiographic feature is most pathognomonic for infantile Blount's disease (tibia vara)?

. Lateral metaphyseal beaking of the distal femur
. Medial metaphyseal beaking and fragmentation of the proximal tibia
. Premature closure of the entire proximal tibial physis
. Widening and irregularity of the distal femoral physis
. Lateral subluxation of the patellofemoral joint

Correct Answer & Explanation

. Medial metaphyseal beaking and fragmentation of the proximal tibia

Explanation

Infantile Blount's disease is characterized by an asymmetric suppression of growth at the medial aspect of the proximal tibial physis. The classic pathognomonic radiographic sign is prominent medial metaphyseal beaking (with eventual fragmentation and sloping), leading to progressive varus, procurvatum, and internal rotation deformities. A metaphyseal-diaphyseal angle > 16 degrees strongly differentiates it from physiologic bowing.

Question 2183

Topic: Pediatric Hip

A 12-year-old obese male presents with a 3-week history of left thigh pain and a limp. Examination shows obligatory external rotation of the hip with passive flexion. Radiographs demonstrate a mild slipped capital femoral epiphysis (SCFE). Which of the following is the most significant risk factor for developing chondrolysis in this patient?

. Prophylactic pinning of the contralateral hip
. Unrecognized penetration of the joint space with the fixation screw
. Performing an open subcapital realignment (modified Dunn procedure)
. The duration of symptoms prior to presentation
. Patient's BMI over the 95th percentile

Correct Answer & Explanation

. Unrecognized penetration of the joint space with the fixation screw

Explanation

Chondrolysis is a devastating complication of SCFE characterized by rapid destruction of the articular cartilage. While it can occur in unpinned SCFE, the most strongly associated iatrogenic risk factor is unrecognized pin penetration into the joint space. Approach and pinning technique must include multi-planar fluoroscopy (the 'approach-withdraw' technique) to ensure the screw threads stay entirely within the femoral head.

Question 2184

Topic: Pediatric Lower Extremity

When applying the Ponseti method for the correction of idiopathic clubfoot, which of the following describes the correct order of deformity correction?

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

Correct Answer & Explanation

. Cavus, equinus, adductus, varus

Explanation

The sequence of correction in the Ponseti method follows the acronym CAVE: Cavus (corrected first by supinating the forefoot and elevating the first ray to align it with the hindfoot), Adductus, Varus (corrected simultaneously by abducting the foot around the fixed talar head), and finally Equinus (which is corrected last and often requires a percutaneous Achilles tenotomy).

Question 2185

Topic: Pediatric Hip

A 12-year-old boy presents with left groin pain and an obligatory external rotation of the hip during flexion. Radiographs confirm a moderate, stable slipped capital femoral epiphysis (SCFE). Which of the following patient characteristics is the strongest absolute indication for prophylactic in-situ pinning of the contralateral, asymptomatic hip?

. BMI > 95th percentile
. Renal osteodystrophy
. Age greater than 14 years at presentation
. Family history of SCFE in a sibling
. African American descent

Correct Answer & Explanation

. Renal osteodystrophy

Explanation

Prophylactic pinning of the contralateral hip in unilateral SCFE remains controversial for idiopathic cases. However, it is strongly indicated (often considered an absolute indication) in patients with underlying metabolic bone diseases (such as renal osteodystrophy) or endocrinopathies (like hypothyroidism or growth hormone supplementation), as their risk of developing a contralateral slip approaches 100%.

Question 2186

Topic: Pediatric Hip

A 6-week-old infant with developmental dysplasia of the hip (DDH) is placed in a Pavlik harness. Two weeks later at a follow-up appointment, the parents report the infant is no longer actively kicking the right leg. On examination, the infant has active ankle and toe movement but cannot actively extend the knee. Patellar reflex is diminished. What is the most likely iatrogenic cause of this presentation?

. Avascular necrosis of the femoral head due to excessive abduction
. Sciatic nerve palsy due to inadequate hip flexion
. Femoral nerve palsy due to excessive hip flexion
. Obturator nerve palsy due to excessive external rotation
. Peroneal nerve palsy due to a tight foot strap

Correct Answer & Explanation

. Femoral nerve palsy due to excessive hip flexion

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically resulting from hyperflexion of the hips, which causes compression of the femoral nerve against the inguinal ligament. It manifests as an inability to actively extend the knee. The appropriate action is to temporarily loosen the anterior straps or remove the harness to allow the nerve to recover.

Question 2187

Topic: Pediatric Hip

A 3-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a follow-up visit, the parents report that the child has stopped extending her knee on the treated side. On examination, the patellar reflex is absent, and the hip is positioned in 125 degrees of flexion. Which of the following is the most likely cause of this complication?

. Hyperflexion causing femoral nerve palsy
. Hyperabduction causing avascular necrosis
. Hyperextension causing sciatic nerve palsy
. Hyperabduction causing obturator nerve palsy
. Strap loosening leading to recurrent dislocation

Correct Answer & Explanation

. Hyperflexion causing femoral nerve palsy

Explanation

Excessive hip flexion (typically >120 degrees) in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy. This presents clinically as a loss of active knee extension and an absent patellar reflex. The treatment is to temporarily adjust the anterior straps to decrease hip flexion or remove the harness until nerve function returns. Excessive abduction, on the other hand, is associated with avascular necrosis.

Question 2188

Topic: Pediatric Hip

Which of the following eponymous radiographic signs describes a crescent-shaped area of increased radiodensity in the proximal femoral metaphysis on an AP pelvis radiograph in a patient with a Slipped Capital Femoral Epiphysis (SCFE)?

. Gage's sign
. Trethowan's sign
. Blanch sign of Steel
. Waldenstrom's sign
. Sagging rope sign

Correct Answer & Explanation

. Blanch sign of Steel

Explanation

The Blanch sign of Steel is a crescent-shaped double density seen on the AP radiograph of a SCFE, caused by the superimposition of the posteriorly displaced femoral epiphysis on the metaphysis. Trethowan's sign refers to Klein's line passing completely superior to the epiphysis. Waldenstrom's sign is an increased distance between the medial epiphysis and the pelvic teardrop (effusion). The sagging rope sign is a thin sclerotic line running transversely across the metaphysis indicating severe deformity.

Question 2189

Topic: 4. Pediatrics

A 6-year-old boy with spastic quadriplegic cerebral palsy is evaluated for hip surveillance. His Gross Motor Function Classification System (GMFCS) level is V. An anteroposterior pelvis radiograph shows a Reimers' migration percentage of 45% bilaterally with early uncovering of the femoral heads, but the femoral heads are spherical and the cartilage space is preserved. What is the most appropriate management?

. Observation with repeat radiographs in 12 months
. Bilateral adductor and psoas tenotomies alone
. Bilateral varus derotational proximal femoral osteotomies and pelvic osteotomies
. Bilateral total hip arthroplasties
. Botulinum toxin injection into the hip adductors

Correct Answer & Explanation

. Bilateral varus derotational proximal femoral osteotomies and pelvic osteotomies

Explanation

In children with severe CP (GMFCS IV or V), the risk of progressive hip displacement is very high. A Reimers' migration percentage (MP) > 30% defines subluxation, and an MP > 40-50% in a 6-year-old typically requires reconstructive bony surgery to prevent painful dislocation. Soft tissue releases alone (adductor/psoas tenotomies) are generally reserved for early subluxation (MP 30-40%) in younger children (<4 years) with no bony deformity. Once significant subluxation (MP >40%) with bony dysplasia is present, bony reconstruction (VDRO +/- pelvic osteotomy, such as Dega or San Diego) is the gold standard.

Question 2190

Topic: Pediatric Hip

A 4-month-old female is diagnosed with developmental dysplasia of the hip (DDH) after an ultrasound shows an alpha angle of 40 degrees and 20% coverage. She is placed in a Pavlik harness. Which complication is most closely associated with excessive hip flexion in the harness?

. Femoral nerve palsy
. Sciatic nerve palsy
. Obturator nerve palsy
. Avascular necrosis of the femoral head
. Inferior dislocation of the hip

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Excessive hip flexion (>120 degrees) in a Pavlik harness can impinge the femoral nerve against the inguinal ligament, leading to femoral nerve palsy. Excessive abduction is strongly associated with avascular necrosis (AVN) of the femoral head.

Question 2191

Topic: Pediatric Hip

A 13-year-old obese boy presents with a 3-week history of right groin and thigh pain, and a limp. Examination reveals obligate external rotation of the right hip during passive flexion. Radiographs confirm a mild Slipped Capital Femoral Epiphysis (SCFE). What is the most appropriate initial management?

. Immediate weight-bearing as tolerated
. Closed reduction and spica casting
. In situ percutaneous pinning
. Open reduction and internal fixation
. Proximal femoral osteotomy

Correct Answer & Explanation

. In situ percutaneous pinning

Explanation

The gold standard treatment for a stable SCFE is in situ percutaneous pinning with a single cannulated screw to prevent further slip. Attempted closed reduction is strongly contraindicated due to the high risk of causing avascular necrosis (AVN) of the femoral head.

Question 2192

Topic: Pediatric Hip
A 6-year-old boy is diagnosed with Legg-Calvé-Perthes disease. Which of the following radiographic signs is considered a 'head at risk' sign according to Catterall, indicating a potentially poorer prognosis?
. Gage sign
. Crescent sign
. Waldenström sign
. Sagging rope sign
. Metaphyseal blanch sign

Correct Answer & Explanation

. Gage sign

Explanation

Catterall 'head at risk' signs for Legg-Calvé-Perthes disease indicate impending collapse and poor prognosis. They include the Gage sign (a small V-shaped radiolucency in the lateral portion of the epiphysis and adjacent metaphysis), lateral calcification, lateral subluxation, a horizontal physis, and metaphyseal cysts.

Question 2193

Topic: Pediatric Hip

An 18-month-old child presents with an untreated developmental dysplasia of the hip (DDH) and undergoes an open reduction and spica casting. Intraoperatively, the surgeon carefully positions the hip. Which of the following maneuvers is the most critical intraoperative factor to prevent avascular necrosis (AVN) of the femoral head?

. Extensive capsulorrhaphy technique
. Routine proximal femoral shortening osteotomy
. Complete resection of the ligamentum teres
. Avoidance of extreme abduction during casting
. Routine release of the iliopsoas tendon

Correct Answer & Explanation

. Avoidance of extreme abduction during casting

Explanation

Extreme abduction (the traditional 'frog-leg' position) causes increased mechanical pressure on the vulnerable capital femoral epiphysis and its blood supply, significantly increasing the risk of iatrogenic AVN. The safe zone of Ramsey mandates immobilizing the hip in the 'human position' (moderate abduction and flexion).

Question 2194

Topic: Pediatric Hip

A 13-year-old obese boy presents with a 3-week history of left knee pain and a limp. Examination reveals obligatory external rotation of the left hip with passive flexion. Radiographs confirm a stable Slipped Capital Femoral Epiphysis (SCFE). Which of the following best describes the true anatomical displacement occurring in a SCFE?

. The epiphysis displaces anteriorly and laterally relative to the metaphysis.
. The epiphysis displaces anteriorly and medially relative to the metaphysis.
. The metaphysis displaces anteriorly and laterally relative to the epiphysis.
. The metaphysis displaces posteriorly and medially relative to the epiphysis.
. The epiphysis displaces superiorly relative to the metaphysis.

Correct Answer & Explanation

. The metaphysis displaces anteriorly and laterally relative to the epiphysis.

Explanation

In a SCFE, the capital femoral epiphysis remains essentially in its normal position within the acetabulum. The true pathology is the displacement of the femoral neck (metaphysis), which translates anteriorly and laterally (externally rotates) relative to the epiphysis. On standard radiographs, this makes the epiphysis appear to have slipped posteriorly and medially.

Question 2195

Topic: Pediatric Hip

Which of the following patients presenting with a unilateral slipped capital femoral epiphysis (SCFE) has the strongest clinical indication for prophylactic pinning of the contralateral, asymptomatic hip?

. A 14-year-old boy with a BMI in the 90th percentile
. A 10-year-old girl with primary hypothyroidism
. A 13-year-old boy with a 45-degree unilateral slip
. An 11-year-old girl with a sudden onset of symptoms after jumping
. A 15-year-old boy with a BMI in the 99th percentile

Correct Answer & Explanation

. A 10-year-old girl with primary hypothyroidism

Explanation

Endocrine disorders (such as hypothyroidism, renal osteodystrophy, and growth hormone deficiency) carry a very high risk (up to 100% in some series) for the development of bilateral SCFE. Patients with these underlying conditions or very young patients (<10 years old) have the strongest indication for prophylactic contralateral pinning.

Question 2196

Topic: Pediatric Hip
In the management of Legg-Calvé-Perthes disease, the Herring lateral pillar classification is widely used to determine prognosis and guide treatment. During which stage of the disease must this classification be assessed to accurately predict outcome?
. Initial (Necrosis) stage
. Fragmentation stage
. Reossification stage
. Remodeling stage
. Healed stage

Correct Answer & Explanation

. Fragmentation stage

Explanation

The Herring lateral pillar classification is most accurate and prognostically significant when assessed during the early fragmentation stage of Legg-Calvé-Perthes disease, as it determines the height of the preserved lateral pillar which is crucial to preventing femoral head extrusion.

Question 2197

Topic: Pediatric Upper Extremity & Spine

In the Lenke classification system for adolescent idiopathic scoliosis, a Type 1 (Main Thoracic) curve pattern is defined strictly by which of the following parameters regarding structurality?

. The main thoracic curve is structural; proximal thoracic and thoracolumbar/lumbar curves are non-structural.
. The double thoracic curves are both structural; the thoracolumbar/lumbar curve is non-structural.
. The main thoracic and thoracolumbar/lumbar curves are both structural.
. All three curves (proximal thoracic, main thoracic, thoracolumbar/lumbar) are structural.
. The thoracolumbar/lumbar curve is the major structural curve; the main thoracic curve is non-structural.

Correct Answer & Explanation

. The main thoracic curve is structural; proximal thoracic and thoracolumbar/lumbar curves are non-structural.

Explanation

According to the Lenke classification, a Type 1 curve is defined by a main thoracic major curve that is structural, while the proximal thoracic and the thoracolumbar/lumbar curves are minor and non-structural (bending out to < 25 degrees).

Question 2198

Topic: Pediatric Hip

A 6-week-old infant with developmental dysplasia of the hip (DDH) is placed in a Pavlik harness. Two weeks later, the parents report the infant is not kicking the affected leg. On exam, the anterior straps are noted to be excessively tight, positioning the hip in greater than 120 degrees of flexion. Which complication has most likely occurred?

. Avascular necrosis of the femoral head
. Femoral nerve palsy
. Sciatic nerve palsy
. Inferior hip dislocation
. Obturator nerve palsy

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Excessive flexion in a Pavlik harness (typically > 120 degrees) can compress the femoral nerve against the inguinal ligament, leading to a temporary femoral nerve palsy (manifested by decreased knee extension/kicking). Excessive abduction (tight posterior straps) increases the risk of avascular necrosis.

Question 2199

Topic: Pediatric Hip

Which of the following clinical scenarios is the most widely accepted indication for prophylactic in situ pinning of the contralateral, asymptomatic hip in a patient with a slipped capital femoral epiphysis (SCFE)?

. A 12-year-old boy with a stable SCFE and a normal body mass index
. A 14-year-old boy with an acute, unstable SCFE
. An 11-year-old girl with renal osteodystrophy and a stable SCFE
. A 13-year-old girl with idiopathic unilateral SCFE and bilateral knee pain
. A 10-year-old boy with a post-traumatic SCFE

Correct Answer & Explanation

. An 11-year-old girl with renal osteodystrophy and a stable SCFE

Explanation

Prophylactic pinning of the contralateral hip is generally recommended for patients with underlying endocrine or metabolic disorders (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy) due to an exceedingly high risk (up to 100% in some series) of bilateral involvement. Routine prophylactic pinning in idiopathic SCFE remains controversial, though it is sometimes considered in very young patients (e.g., <10 years old) or those likely to be non-compliant.

Question 2200

Topic: Pediatric Lower Extremity

According to the Ponseti method for the treatment of idiopathic clubfoot, the initial casting phase prioritizes the correction of the cavus deformity. Which specific manipulation is required to achieve this correction?

. Pronating the forefoot to align with the hindfoot
. Dorsiflexing the first ray with direct pressure under the metatarsal head
. Elevating the first ray to supinate the forefoot and align it with the hindfoot
. Abducting the forefoot with counter-pressure on the lateral calcaneus
. Plantarflexing the ankle to correct the equinus first

Correct Answer & Explanation

. Elevating the first ray to supinate the forefoot and align it with the hindfoot

Explanation

The deformities in clubfoot are remembered by the acronym CAVE (Cavus, Adductus, Varus, Equinus). Cavus is the first deformity to be corrected. It is caused by a plantarflexed first ray relative to the hindfoot. To correct this, the first ray must be elevated, which effectively supinates the forefoot so that it is in alignment with the supinating hindfoot. Pronating the forefoot (a common mistake) worsens the cavus.

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