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4. Pediatrics MCQs

Practice Set 256 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 5101

Topic: 4. Pediatrics
Osteogenesis imperfecta is characterized by recurrent fractures, blue sclera, and dentinogenesis imperfecta. This condition is primarily caused by an autosomal dominant genetic mutation affecting which of the following?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type X collagen

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta is primarily caused by mutations in the COL1A1 or COL1A2 genes, which encode for Type I collagen. Type I collagen is the predominant structural protein found in bone, sclera, and dentin.

Question 5102

Topic: 4. Pediatrics

A newborn is diagnosed with congenital scoliosis due to a unilateral unsegmented bar and a contralateral hemivertebra. Which of the following routine screening investigations is mandatory for this patient?

. Renal Ultrasound
. Pulmonary function tests
. Brain MRI with contrast
. Chromosomal microarray
. DEXA scan

Correct Answer & Explanation

. Renal Ultrasound

Explanation

Up to 30% of patients with congenital scoliosis have associated genitourinary anomalies due to shared embryological timing. A renal ultrasound is mandatory to rule out life-threatening anomalies like unilateral renal agenesis.

Question 5103

Topic: 4. Pediatrics
According to hip surveillance guidelines for children with cerebral palsy, what is the approximate risk of hip displacement (migration percentage > 30%) in a child functioning at GMFCS Level V?
. < 10%
. 20-30%
. 40-50%
. 60-70%
. 90%

Correct Answer & Explanation

. 90%

Explanation

The risk of progressive hip displacement in cerebral palsy is directly correlated with the Gross Motor Function Classification System (GMFCS) level. Children at GMFCS level V (non-ambulatory) have a 90% risk of hip displacement requiring rigorous radiographic surveillance.

Question 5104

Topic: Pediatric Hip

According to the Loder classification, which clinical finding strictly defines an "unstable" slipped capital femoral epiphysis (SCFE)?

. Slip angle > 50 degrees
. Symptom duration less than 3 weeks
. Inability to bear weight, even with crutches
. Presence of a hip effusion on ultrasound
. Radiographic evidence of epiphyseal sclerosis

Correct Answer & Explanation

. Slip angle > 50 degrees

Explanation

The Loder classification defines an unstable SCFE solely by the patient's inability to walk or bear weight on the affected limb, regardless of crutch use. Unstable slips carry a substantially higher risk of avascular necrosis compared to stable slips.

Question 5105

Topic: Pediatric Lower Extremity
A 4-year-old child previously treated for idiopathic clubfoot with the Ponseti method presents with a recurrent dynamic supination deformity during the swing phase of gait. Passive range of motion is full and the foot is plantigrade. Which of the following is the most appropriate surgical management?
. Repeat serial casting with percutaneous Achilles tenotomy
. Split anterior tibial tendon transfer (SPLATT)
. Full anterior tibial tendon transfer to the lateral cuneiform
. Extensive posteromedial soft tissue release
. Lateral column shortening osteotomy

Correct Answer & Explanation

. Full anterior tibial tendon transfer to the lateral cuneiform

Explanation

Dynamic supination in a relapsed clubfoot treated by the Ponseti method is usually caused by the overpull of a strong tibialis anterior against weak evertors. The standard treatment is transferring the entire tibialis anterior tendon to the third (lateral) cuneiform to balance foot biomechanics.

Question 5106

Topic: Pediatric Hip

An 8-year-old boy presents with a limp and hip pain. Radiographs reveal Legg-Calve-Perthes disease with greater than 50% loss of lateral pillar height. According to the Herring classification, what group does this represent and what is the associated prognosis?

. Herring Lateral Pillar A; excellent prognosis
. Herring Lateral Pillar B; fair prognosis
. Herring Lateral Pillar C; poor prognosis
. Catterall Group I; excellent prognosis
. Salter-Thompson B; poor prognosis

Correct Answer & Explanation

. Herring Lateral Pillar A; excellent prognosis

Explanation

The Herring Lateral Pillar classification strongly correlates with outcome in Perthes disease. Group C is defined by >50% collapse of the lateral pillar of the femoral head and consistently carries the worst prognosis for joint congruity.

Question 5107

Topic: Pediatric Hip

A 13-year-old boy presents to the emergency department unable to bear weight on his left leg even with crutches after a minor fall. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Which of the following is the most likely severe complication associated with this specific presentation?

. Chondrolysis
. Avascular necrosis (AVN)
. Femoroacetabular impingement
. Contralateral slip progression
. Septic arthritis

Correct Answer & Explanation

. Chondrolysis

Explanation

The inability to bear weight even with crutches defines an unstable SCFE. Unstable slips are associated with a high rate of avascular necrosis, with reported risks ranging from 20% to 50% due to acute vascular disruption.

Question 5108

Topic: 4. Pediatrics

A 14-year-old patient with spastic diplegic cerebral palsy presents with progressive crouch gait. Physical examination reveals hamstring tightness and evidence of a prior iatrogenic over-lengthening of the Achilles tendon. What is the primary kinematic driver of this gait pattern?

. Hip flexor contracture
. Plantarflexor weakness
. Rectus femoris spasticity
. Gluteus medius weakness
. Tibialis anterior spasticity

Correct Answer & Explanation

. Hip flexor contracture

Explanation

Crouch gait in cerebral palsy is frequently precipitated by over-lengthening the Achilles tendon, which leads to iatrogenic plantarflexor weakness. Without strong plantarflexors to control tibial advancement, the knee and hip collapse into flexion during the stance phase.

Question 5109

Topic: 4. Pediatrics

A 2-year-old child presents with a history of multiple low-energy fractures and blue sclerae. A diagnosis of osteogenesis imperfecta is made. This condition is most commonly caused by a mutation affecting which of the following genes?

. FGFR3
. COMP
. COL1A1
. COL2A1
. SOX9

Correct Answer & Explanation

. FGFR3

Explanation

Osteogenesis imperfecta is most commonly an autosomal dominant disorder caused by mutations in the COL1A1 or COL1A2 genes. This results in defective type 1 collagen production, leading to bone fragility and classic blue sclerae.

Question 5110

Topic: Pediatric Lower Extremity

A newborn is diagnosed with fibular hemimelia characterized by anteromedial bowing of the tibia and absent lateral rays of the foot. Which of the following ligamentous anomalies of the knee is most likely present?

. Absent anterior cruciate ligament
. Absent posterior cruciate ligament
. Absent medial collateral ligament
. Absent lateral collateral ligament
. Congenital patellar tendon avulsion

Correct Answer & Explanation

. Absent anterior cruciate ligament

Explanation

Fibular hemimelia is a longitudinal deficiency spectrum that is strongly associated with an absent or hypoplastic anterior cruciate ligament (ACL). Other common associations include a ball-and-socket ankle joint and tarsal coalition.

Question 5111

Topic: 4. Pediatrics
A 14-year-old boy sustains a Salter-Harris III fracture of the anterolateral distal tibial epiphysis while playing soccer. What is the most common mechanism of injury for this specific fracture pattern?
. Supination-adduction
. External rotation
. Axial loading
. Plantarflexion
. Pronation-abduction

Correct Answer & Explanation

. External rotation

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibia caused by an external rotation force. The anterior inferior tibiofibular ligament (AITFL) avulses the anterolateral epiphysis, which is the last portion of the physis to fuse.

Question 5112

Topic: 4. Pediatrics
A 3-year-old boy presents with severe, progressive tibia vara. Radiographs demonstrate Langenskiold stage III infantile Blount's disease. What is the primary pathoanatomical mechanism driving this deformity?
. Overgrowth of the medial proximal tibial physis
. Premature closure of the lateral proximal tibial physis
. Disruption of normal endochondral ossification of the medial proximal tibial physis
. Hypertrophy of the medial collateral ligament
. Congenital posterolateral bowing of the tibia

Correct Answer & Explanation

. Disruption of normal endochondral ossification of the medial proximal tibial physis

Explanation

Infantile Blount's disease results from mechanical overloading of the posteromedial proximal tibial physis, consistent with the Heuter-Volkmann principle. This excessive compression disrupts normal endochondral ossification, leading to growth suppression and progressive varus.

Question 5113

Topic: 4. Pediatrics

A 6-year-old non-ambulatory child with spastic quadriplegic cerebral palsy (GMFCS Level V) is evaluated in the hip surveillance clinic. Radiographs reveal a Reimers migration percentage of 45% bilaterally. What is the recommended definitive management?

. Observation with radiographs every 6 months
. Bilateral adductor and iliopsoas tenotomies
. Varus derotational osteotomy (VDRO) and pelvic osteotomies
. Bilateral total hip arthroplasties
. Proximal femoral resection arthroplasty (Castle procedure)

Correct Answer & Explanation

. Observation with radiographs every 6 months

Explanation

In a child with CP and a hip migration percentage approaching or exceeding 40-50%, soft tissue releases alone are inadequate and carry a high failure rate. Bony reconstruction with a proximal femoral VDRO and a pelvic osteotomy (e.g., Dega) is indicated to restore concentric reduction.

Question 5114

Topic: Pediatric Upper Extremity & Spine

A 14-year-old girl is evaluated for Adolescent Idiopathic Scoliosis (AIS). Her main thoracic curve measures 55 degrees, and her thoracolumbar curve measures 20 degrees but bends out to 5 degrees on side-bending films. The center sacral vertical line (CSVL) falls between the pedicles of the apical lumbar vertebra. What is her Lenke classification?

. Type 1A
. Type 2B
. Type 3C
. Type 4A
. Type 5C

Correct Answer & Explanation

. Type 1A

Explanation

A main thoracic curve >40 degrees with a flexible thoracolumbar curve that bends out to <25 degrees defines a Lenke Type 1 (Main Thoracic) pattern. Because the CSVL bisects the apical lumbar vertebra, she is assigned a lumbar modifier A.

Question 5115

Topic: Pediatric Hip

A 3-year-old girl presents with a painless limp. She has never been treated for developmental dysplasia of the hip (DDH). Radiographs show a chronically dislocated left hip with a false acetabulum. What is the most appropriate surgical intervention?

. Closed reduction and spica casting
. Open reduction alone
. Open reduction, femoral shortening derotational osteotomy, and pelvic osteotomy
. Application of a Pavlik harness
. Shelf arthroplasty

Correct Answer & Explanation

. Closed reduction and spica casting

Explanation

In a child older than 2 to 3 years with a neglected DDH dislocation, open reduction alone is insufficient and carries a high risk of AVN and redislocation. Femoral shortening (to decompress the joint) and a pelvic osteotomy (to correct acetabular dysplasia) are concurrently required.

Question 5116

Topic: 4. Pediatrics

An 8-year-old boy presents with a limp and hip pain. Radiographs reveal fragmentation of the capital femoral epiphysis. According to the Herring classification, which radiographic feature is the most important prognostic factor in this disease process?

. Extrusion of the femoral head
. Involvement of the lateral pillar of the femoral head
. Presence of a metaphyseal cyst
. Closure of the physis
. Sclerosis of the medial pillar

Correct Answer & Explanation

. Extrusion of the femoral head

Explanation

The Herring Lateral Pillar classification is the most reliable prognostic indicator in Legg-Calve-Perthes disease. It assesses the height of the lateral pillar on the AP radiograph during the fragmentation stage.

Question 5117

Topic: Pediatric Lower Extremity

During the Ponseti method for treating idiopathic clubfoot, what is the first step in the manipulative correction process?

. Correction of ankle equinus
. Abduction of the midfoot
. Elevation of the first ray to correct cavus
. Correction of heel varus
. Internal rotation of the forefoot

Correct Answer & Explanation

. Correction of ankle equinus

Explanation

The first step in the Ponseti method is correcting the cavus by elevating the first ray and supinating the forefoot to align it with the hindfoot. Further corrections follow the CAVE sequence: Cavus, Adductus, Varus, and Equinus.

Question 5118

Topic: 4. Pediatrics

A 6-year-old boy with spastic quadriplegic cerebral palsy is undergoing hip surveillance. Which muscle group's spasticity is the primary driver of the posterosuperior hip subluxation commonly seen in these patients?

. Abductors and external rotators
. Adductors and flexors
. Gluteus maximus and hamstrings
. Quadriceps and sartorius
. Iliopsoas and rectus femoris alone

Correct Answer & Explanation

. Abductors and external rotators

Explanation

Hip displacement in cerebral palsy is primarily driven by the overactivity and contracture of the hip adductors and flexors (iliopsoas). This creates a posterosuperior vector of force, leading to subluxation and eventually dislocation.

Question 5119

Topic: 4. Pediatrics
A 13-year-old girl sustains an ankle injury. Radiographs show a Salter-Harris III fracture of the anterolateral distal tibia. Which ligament's avulsion force is responsible for this specific fracture pattern?
. Deltoid ligament
. Posterior inferior tibiofibular ligament
. Anterior talofibular ligament
. Anterior inferior tibiofibular ligament (AITFL)
. Calcaneofibular ligament

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament (AITFL)

Explanation

The juvenile Tillaux fracture is a Salter-Harris III avulsion fracture of the anterolateral distal tibial epiphysis. It is caused by an external rotation force with tension transmitted through the anterior inferior tibiofibular ligament (AITFL).

Question 5120

Topic: 4. Pediatrics

A 4-year-old boy with blue sclerae and a history of multiple fractures is diagnosed with Osteogenesis Imperfecta. What is the fundamental genetic defect associated with the most common forms of this condition?

. Mutation in the FGFR3 gene
. Defect in the synthesis of Type II collagen
. Mutations in the COL1A1 or COL1A2 genes
. Deficiency of the enzyme tissue-nonspecific alkaline phosphatase
. Mutation in the COMP gene

Correct Answer & Explanation

. Mutation in the FGFR3 gene

Explanation

Osteogenesis Imperfecta is predominantly caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes. This leads to quantitative or qualitative defects in Type I collagen, the major structural protein in bone.

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