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4. Pediatrics MCQs

Practice Set 258 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 5141

Topic: 4. Pediatrics

In a patient with Legg-Calve-Perthes disease, which of the following radiographic findings is considered a 'head-at-risk' sign according to Catterall?

. Gage sign
. Medial subluxation of the femoral head
. Vertical physeal line
. Decreased teardrop distance
. Presence of a subchondral fracture extending less than half of the epiphysis

Correct Answer & Explanation

. Gage sign

Explanation

Catterall identified specific 'head-at-risk' radiographic signs that indicate a poorer prognosis in Perthes disease. These include the Gage sign (a V-shaped radiolucency in the lateral portion of the epiphysis and adjacent metaphysis), lateral calcification, lateral subluxation of the femoral head, and a horizontal growth plate.

Question 5142

Topic: 4. Pediatrics

A 5-year-old boy with spastic quadriplegic cerebral palsy (GMFCS Level V) is evaluated in the orthopedic clinic. Pelvic radiographs demonstrate a migration percentage of 45% bilaterally. What is the most appropriate management strategy?

. Observation and repeat radiograph in 1 year
. Botulinum toxin injections to the hip adductors
. Bilateral adductor longus and gracilis tenotomies
. Bilateral varus derotational osteotomies (VDRO) with or without pelvic osteotomy
. Total hip arthroplasty

Correct Answer & Explanation

. Observation and repeat radiograph in 1 year

Explanation

In cerebral palsy patients, a Reimer's migration percentage >40% typically indicates progressive hip subluxation that is past the point of responding to soft tissue releases alone (which are usually indicated for migration percentages between 25-40%). Bony reconstructive surgery, such as a VDRO often combined with a pelvic osteotomy, is required to achieve stable reduction.

Question 5143

Topic: Pediatric Lower Extremity

Proximal focal femoral deficiency (PFFD) is most frequently associated with which of the following congenital anomalies?

. Tibial hemimelia
. Fibular hemimelia
. Congenital short femur
. Radioulnar synostosis
. Clubfoot

Correct Answer & Explanation

. Tibial hemimelia

Explanation

PFFD is highly associated with fibular hemimelia, occurring in approximately 50-70% of cases. Evaluation of a patient with PFFD must include careful assessment of the entire limb to check for fibular deficiency, absence of cruciate ligaments, and foot deformities.

Question 5144

Topic: Pediatric Hip

A 13-year-old boy undergoes in situ pinning with a single cannulated screw for a stable SCFE. Three months postoperatively, he presents with severe hip pain, stiffness, and significantly restricted range of motion in all planes. Radiographs reveal a global joint space of 2 mm. What is the most likely diagnosis?

. Avascular necrosis of the femoral head
. Chondrolysis
. Implant failure
. Femoral neck fracture
. Septic arthritis

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Chondrolysis is a severe complication of SCFE, presenting with acute onset of pain, global restriction of hip motion, and joint space narrowing (<3mm) on radiographs. It is strongly associated with unrecognized intra-articular hardware penetration during pinning.

Question 5145

Topic: 4. Pediatrics
A 13-year-old girl sustains a juvenile Tillaux fracture of the ankle. This fracture pattern occurs due to avulsion by which ligament, and represents a failure of which part of the distal tibial physis to close first?
. Anterior inferior tibiofibular ligament; failure of anterolateral physis to close
. Posterior inferior tibiofibular ligament; failure of posterolateral physis to close
. Anterior inferior tibiofibular ligament; failure of anteromedial physis to close
. Deltoid ligament; failure of medial physis to close
. Calcaneofibular ligament; failure of anterolateral physis to close

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament; failure of anterolateral physis to close

Explanation

A Tillaux fracture is a Salter-Harris III avulsion of the anterolateral distal tibial epiphysis caused by tension from the anterior inferior tibiofibular ligament (AITFL). It occurs in adolescents because the distal tibial physis closes asymmetrically (central, then anteromedial, then posteromedial), leaving the anterolateral portion open last and vulnerable to avulsion.

Question 5146

Topic: Pediatric Lower Extremity

Which of the following features accurately differentiates infantile Blount's disease from adolescent Blount's disease?

. Adolescent Blount's is more commonly bilateral
. Infantile Blount's is associated with lateral thrust and joint laxity
. Infantile Blount's primarily affects the distal femur
. Adolescent Blount's responds well to orthotic management
. Infantile Blount's is less likely to require surgical intervention if diagnosed early

Correct Answer & Explanation

. Adolescent Blount's is more commonly bilateral

Explanation

Infantile Blount's disease is often bilateral (up to 80%) and classically presents with a prominent lateral thrust during gait due to severe proximal medial tibial metaphyseal beaking and associated ligamentous laxity. Adolescent Blount's is usually unilateral, lacks the pronounced lateral thrust, and does not respond to orthotics.

Question 5147

Topic: 4. Pediatrics

A 5-year-old boy with myelomeningocele at the L4 level is being evaluated for lower extremity deformities. Based strictly on his neurologic level, which deformity of the foot and ankle is he most likely to develop?

. Equinovarus
. Calcaneovalgus
. Equinovalgus
. Cavovarus
. Planovalgus

Correct Answer & Explanation

. Equinovarus

Explanation

In an L4 myelomeningocele, the anterior tibialis (L4) is functioning, leading to strong dorsiflexion. However, the triceps surae (S1-S2) is paralyzed, resulting in an absent plantarflexion counterforce. This classic muscle imbalance produces a calcaneus or calcaneovalgus foot deformity over time.

Question 5148

Topic: 4. Pediatrics

An infant is diagnosed with congenital muscular torticollis of the right sternocleidomastoid (SCM) muscle. What is the typical resting posture of the infant's head and neck?

. Head tilted to the right and chin rotated to the right
. Head tilted to the right and chin rotated to the left
. Head tilted to the left and chin rotated to the right
. Head tilted to the left and chin rotated to the left
. Head extended and chin rotated to the right

Correct Answer & Explanation

. Head tilted to the right and chin rotated to the right

Explanation

The sternocleidomastoid muscle functions to laterally flex (tilt) the neck to the ipsilateral side and rotate the chin to the contralateral side. Therefore, a contracture of the right SCM results in the head tilting toward the right shoulder and the chin rotating toward the left shoulder.

Question 5149

Topic: 4. Pediatrics

A 6-year-old child with spastic quadriplegic cerebral palsy undergoes radiographic screening of the pelvis. The Reimers' migration percentage is calculated to be 45% bilaterally. What is the most appropriate management for this patient?

. Observation with repeat radiographs in 1 year
. Botulinum toxin A injections to the hip adductors
. Proximal femoral varus derotational osteotomy (VDRO) and pelvic osteotomy
. Bilateral hip arthrodesis
. Selective dorsal rhizotomy

Correct Answer & Explanation

. Observation with repeat radiographs in 1 year

Explanation

In children with cerebral palsy, hip displacement is common due to muscle imbalance. A Reimers' migration percentage (MP) greater than 40-50% in a spastic patient is generally an indication for reconstructive surgery to prevent a painful, dislocated hip. This is typically achieved with a proximal femoral varus derotational osteotomy (VDRO) combined with a pelvic osteotomy (e.g., Dega or San Diego) to improve acetabular coverage.

Question 5150

Topic: 4. Pediatrics
Sillence Type I Osteogenesis Imperfecta (OI) typically presents with milder skeletal fragility and blue sclerae. Which of the following best describes the underlying genetic and molecular defect in this type of OI?
. Quantitative defect in type I collagen due to a premature stop codon in COL1A1
. Qualitative defect in type I collagen due to a glycine substitution in COL1A2
. Gain-of-function mutation in the FGFR3 gene
. Defect in the COMP gene causing abnormal cartilage matrix
. Mutation in the CBFA1 (RUNX2) transcription factor

Correct Answer & Explanation

. Quantitative defect in type I collagen due to a premature stop codon in COL1A1

Explanation

Sillence Type I OI is the most common and mildest form. It is generally caused by a quantitative defect—specifically, decreased synthesis of structurally normal type I collagen, most often due to a premature stop codon (null allele) in the COL1A1 gene. Types II, III, and IV are typically caused by qualitative defects (abnormal collagen structure), usually from glycine substitutions in COL1A1 or COL1A2.

Question 5151

Topic: 4. Pediatrics

A newborn is evaluated for an absent right radius and an absent thumb (radial longitudinal deficiency). The consulting orthopedic surgeon recommends a thorough pediatric and genetics workup. Which of the following cardiac conditions is most classically associated with this musculoskeletal deformity?

. Tetralogy of Fallot
. Atrial Septal Defect (ASD)
. Transposition of the Great Arteries
. Coarctation of the aorta
. Patent ductus arteriosus

Correct Answer & Explanation

. Tetralogy of Fallot

Explanation

Radial longitudinal deficiency is associated with several syndromes, notably Holt-Oram syndrome (autosomal dominant, TBX5 mutation). Holt-Oram is classically characterized by radial-sided upper extremity anomalies and congenital heart defects, most commonly Atrial Septal Defects (ASDs) and Ventricular Septal Defects (VSDs).

Question 5152

Topic: 4. Pediatrics

Achondroplasia is the most common form of short-limbed dwarfism. Which of the following accurately describes the molecular pathogenesis and inheritance pattern of this condition?

. Gain-of-function mutation in FGFR3; Autosomal dominant
. Loss-of-function mutation in FGFR3; Autosomal recessive
. Defect in COL2A1; X-linked dominant
. Defect in COMP; Autosomal dominant
. Mutation in CBFA1; Autosomal recessive

Correct Answer & Explanation

. Gain-of-function mutation in FGFR3; Autosomal dominant

Explanation

Achondroplasia is caused by a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene, which paradoxically inhibits chondrocyte proliferation in the proliferative zone of the physis. It is inherited in an autosomal dominant pattern, although ~80% of cases occur as spontaneous new mutations.

Question 5153

Topic: Pediatric Hip

A 12-year-old boy with a BMI of 35 presents with acute-on-chronic hip pain. He is diagnosed with a slipped capital femoral epiphysis (SCFE). According to the Loder classification, which clinical finding classifies his SCFE as 'unstable'?

. Slip angle > 50 degrees
. Presence of an intra-articular effusion on ultrasound
. Inability to bear weight on the affected limb, even with crutches
. Duration of symptoms less than 3 weeks
. Displacement of more than 50% of the femoral neck width

Correct Answer & Explanation

. Slip angle > 50 degrees

Explanation

The Loder classification divides SCFE into stable and unstable categories based entirely on the clinical ability to bear weight. An unstable SCFE is defined as the inability to bear weight, even with assistive devices. Unstable SCFEs carry a much higher risk of avascular necrosis (AVN), historically up to 47%.

Question 5154

Topic: 4. Pediatrics

Congenital pseudarthrosis of the tibia (CPT) typically presents with anterolateral bowing of the tibia and subsequent fracture that fails to heal. This condition is most strongly associated with which of the following genetic syndromes?

. Neurofibromatosis type 1
. Osteogenesis Imperfecta
. Tuberous Sclerosis
. Marfan syndrome
. McCune-Albright syndrome

Correct Answer & Explanation

. Neurofibromatosis type 1

Explanation

Congenital pseudarthrosis of the tibia (CPT) is strongly associated with Neurofibromatosis type 1 (NF1). Approximately 50% of patients with CPT have clinical stigmata of NF1, and the condition is notoriously difficult to treat, often requiring excision of the pseudarthrosis, bone grafting, and rigid internal fixation.

Question 5155

Topic: Pediatric Upper Extremity & Spine

When evaluating a patient with Adolescent Idiopathic Scoliosis (AIS), which of the following parameters is the strongest clinical predictor for the risk of curve progression?

. Apical vertebral rotation
. Thoracic kyphosis > 40 degrees
. Peak height velocity
. Lumbar curve location
. Positive family history

Correct Answer & Explanation

. Apical vertebral rotation

Explanation

The risk of curve progression in AIS is highly dependent on the remaining growth potential. The period of highest risk for progression corresponds to the adolescent growth spurt, known as peak height velocity. Markers of skeletal immaturity (e.g., Risser 0, open triradiate cartilage) indicate that the child is entering or currently in this high-risk phase.

Question 5156

Topic: 4. Pediatrics

A 13-year-old boy twists his ankle and sustains a Tillaux fracture (avulsion fracture of the anterolateral distal tibial epiphysis). This specific fracture pattern is dictated by the physiological closure sequence of the distal tibial physis. Which of the following describes the correct sequence of closure?

. Central -> Posteromedial -> Anteromedial -> Anterolateral
. Central -> Anteromedial -> Posteromedial -> Anterolateral
. Anterolateral -> Central -> Posteromedial -> Anteromedial
. Posteromedial -> Anterolateral -> Central -> Anteromedial
. Anteromedial -> Anterolateral -> Posteromedial -> Central

Correct Answer & Explanation

. Central -> Posteromedial -> Anteromedial -> Anterolateral

Explanation

The distal tibial physis closes asymmetrically over approximately 18 months. The closure begins centrally, proceeds anteromedially, then posteromedially, and finishes anterolaterally. Because the anterolateral physis remains open the longest, it is susceptible to avulsion by the anterior inferior tibiofibular ligament (AITFL), resulting in a Tillaux fracture.

Question 5157

Topic: Pediatric Hip

An 8-year-old boy is diagnosed with Legg-Calve-Perthes disease. Which of the following radiographic findings is one of Catterall's 'head-at-risk' signs, indicating a poorer prognosis and a higher likelihood of femoral head deformation?

. Medial subluxation of the femoral head
. Gage sign (V-shaped radiolucency in the lateral epiphysis/metaphysis)
. Narrowing of the teardrop distance
. Sclerosis of the central acetabulum
. Premature closure of the greater trochanteric apophysis

Correct Answer & Explanation

. Medial subluxation of the femoral head

Explanation

Catterall described five 'head-at-risk' signs that portend a poor prognosis in Perthes disease: 1) Gage sign (a V-shaped radiolucency in the lateral epiphysis and adjacent metaphysis), 2) Lateral calcification, 3) Lateral subluxation of the femoral head, 4) Metaphyseal cysts, and 5) A horizontal growth plate.

Question 5158

Topic: 4. Pediatrics

A newborn is evaluated for congenital constriction rings around multiple digits, with an auto-amputation of the right index finger. This is diagnosed as Amniotic Band Syndrome. Which of the following congenital orthopedic anomalies is most commonly associated with this condition?

. Developmental dysplasia of the hip (DDH)
. Clubfoot (Talipes equinovarus)
. Sprengel deformity
. Congenital vertical talus
. Tarsal coalition

Correct Answer & Explanation

. Developmental dysplasia of the hip (DDH)

Explanation

Amniotic band syndrome is caused by the entrapment of fetal parts (usually limbs or digits) in fibrous amniotic bands. It is highly associated with clubfoot, occurring in up to 30% of these patients. It is also associated with cleft lip/palate and acrosyndactyly.

Question 5159

Topic: Pediatric Hip

A 13-year-old boy presents with right hip pain and inability to bear weight for 2 days. X-rays confirm a slipped capital femoral epiphysis. According to the Loder classification, what is the primary prognostic significance of his inability to bear weight?

. High risk of chondrolysis
. High risk of avascular necrosis (AVN)
. Mandates prophylactic contralateral pinning
. Indicates an underlying endocrine disorder
. Predicts a stable, non-progressive course

Correct Answer & Explanation

. High risk of chondrolysis

Explanation

According to the Loder classification, an unstable SCFE is defined by the inability to bear weight even with crutches. Unstable slips carry a significantly higher risk of avascular necrosis (up to nearly 50%) compared to stable slips.

Question 5160

Topic: Pediatric Lower Extremity

A 4-year-old boy previously treated for clubfoot with the Ponseti method presents with a relapsed deformity. He exhibits dynamic supination of the foot during the swing phase of gait. What is the most appropriate definitive management?

. Repeat percutaneous Achilles tenotomy
. Transfer of the tibialis anterior to the lateral cuneiform
. Split tibialis posterior tendon transfer
. Triple arthrodesis
. Calcaneal sliding osteotomy

Correct Answer & Explanation

. Repeat percutaneous Achilles tenotomy

Explanation

Dynamic supination during the swing phase of gait is a common sign of a relapsed clubfoot treated with the Ponseti method. It is best managed by transferring the whole tibialis anterior tendon to the lateral cuneiform to balance eversion and inversion forces.

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