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4. Pediatrics MCQs

Practice Set 236 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 4701

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy sustains a severe extension-type supracondylar humerus fracture. On examination, the hand is pink and warm with normal capillary refill, but the radial pulse is not palpable.

What is the most appropriate initial management?

. Immediate open vascular exploration
. Urgent closed reduction and percutaneous pinning, followed by reassessment of perfusion
. CT angiography to identify arterial injury before any fracture manipulation
. Application of a long arm cast in 120 degrees of flexion
. Observation in the emergency department for 24 hours to allow for vasospasm resolution

Correct Answer & Explanation

. Immediate open vascular exploration

Explanation

For a 'pulseless, pink hand' associated with a supracondylar humerus fracture, the standard of care is urgent closed reduction and percutaneous pinning (CRPP). If the hand remains pink and well-perfused post-reduction, routine vascular exploration is unnecessary.

Question 4702

Topic: Pediatric Lower Extremity

An infant born with idiopathic clubfoot is treated with the Ponseti method. After successful sequential casting and a percutaneous Achilles tenotomy, the foot is placed in a foot abduction orthosis. The parents ask what the most common cause of future deformity recurrence is. What is the correct response?

. Failure to perform an anterior tibial tendon transfer at age 2
. Incomplete initial correction of the equinus deformity
. Non-compliance with the post-correction bracing protocol
. An underlying undiagnosed neuromuscular disorder
. Premature initiation of weight-bearing and standing

Correct Answer & Explanation

. Failure to perform an anterior tibial tendon transfer at age 2

Explanation

The vast majority of clubfoot relapses following successful Ponseti casting and tenotomy are directly attributed to poor parental adherence to the foot abduction orthosis (Denis Browne splint) bracing protocol. Strict compliance significantly minimizes relapse rates.

Question 4703

Topic: 4. Pediatrics

A 4-year-old child with a history of multiple low-energy fractures, distinct blue sclerae, and dentinogenesis imperfecta is evaluated in the orthopedic clinic. Genetic testing reveals an autosomal dominant mutation. This systemic condition is primarily caused by a quantitative or qualitative defect in which of the following?

. Type II collagen
. Fibroblast growth factor receptor 3 (FGFR3)
. Type I collagen
. Cartilage oligomeric matrix protein (COMP)
. Core binding factor alpha 1 (CBFA1)

Correct Answer & Explanation

. Type II collagen

Explanation

Osteogenesis imperfecta (OI) is most commonly caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, leading to defective Type I collagen synthesis. This affects bone, sclera, and dentin, producing the classic clinical triad.

Question 4704

Topic: Pediatric Lower Extremity

A 4-year-old boy previously treated for idiopathic clubfoot with the Ponseti method presents with a dynamic supination deformity during the swing phase of gait. Passive ankle dorsiflexion is 15 degrees. What is the most appropriate surgical management?

. Repeat serial casting
. Tibialis anterior tendon transfer
. Achilles tendon lengthening
. Lateral column shortening
. Posteromedial soft tissue release

Correct Answer & Explanation

. Repeat serial casting

Explanation

Dynamic supination during the swing phase in a relapsed clubfoot, when passive dorsiflexion is adequate, is treated with a tibialis anterior tendon transfer to the lateral cuneiform.

Question 4705

Topic: Pediatric Hip
An 8-year-old boy is diagnosed with Legg-Calvé-Perthes disease. Anteroposterior radiographs demonstrate greater than 50% loss of the lateral pillar height. According to the Herring classification, which group does this represent and what is the expected outcome?
. Group A; excellent outcome with conservative care
. Group B; fair outcome, may benefit from surgery
. Group B/C; guarded outcome
. Group C; poor outcome, high risk of aspherical head
. Group C; excellent outcome if treated with immediate bracing

Correct Answer & Explanation

. Group C; poor outcome, high risk of aspherical head

Explanation

Herring Group C is characterized by >50% collapse of the lateral pillar height. This group is associated with poor prognostic outcomes and a high rate of aspherical femoral heads at maturity.

Question 4706

Topic: 4. Pediatrics

A 10-year-old girl with spastic diplegic cerebral palsy is found to have a Reimers migration percentage of 55% bilaterally. She is asymptomatic but has progressive subluxation. What is the most appropriate surgical intervention?

. Bilateral adductor tenotomies alone
. Bilateral proximal femoral varus derotational osteotomies (VDRO) and pelvic osteotomies
. Bilateral total hip arthroplasties
. Observation and serial bracing
. Open reduction and spica casting

Correct Answer & Explanation

. Bilateral adductor tenotomies alone

Explanation

In older children with cerebral palsy and a Reimers migration index >50%, soft tissue release alone is insufficient. Bony reconstruction with VDRO and a pelvic osteotomy is the standard of care to achieve stable coverage.

Question 4707

Topic: Pediatric Hip

A 14-year-old obese male presents with a stable slipped capital femoral epiphysis (SCFE) of the left hip. He undergoes in situ pinning. Which of the following conditions represents the strongest indication for prophylactic pinning of the asymptomatic contralateral hip?

. Obesity (BMI > 95th percentile)
. Age greater than 15 years
. Male gender
. Underlying hypothyroidism
. Family history of SCFE

Correct Answer & Explanation

. Obesity (BMI > 95th percentile)

Explanation

Endocrine disorders, such as hypothyroidism or panhypopituitarism, and renal osteodystrophy significantly increase the risk of bilateral SCFE, making prophylactic contralateral pinning highly recommended.

Question 4708

Topic: 4. Pediatrics
A 3-year-old boy presents with persistent bowing of the legs. Radiographs reveal medial metaphyseal beaking and a metaphyseal-diaphyseal angle of 18 degrees. What is the most appropriate initial management for this patient?
. Reassurance and observation
. High-dose Vitamin D supplementation
. Knee-ankle-foot orthosis (KAFO)
. Proximal tibial valgus-derotation osteotomy
. Guided growth with tension band plating

Correct Answer & Explanation

. Knee-ankle-foot orthosis (KAFO)

Explanation

A metaphyseal-diaphyseal angle >16 degrees is highly suggestive of infantile Blount disease. Initial treatment in a 3-year-old (Langenskiöld stage I or II) typically involves a trial of bracing with a KAFO.

Question 4709

Topic: Pediatric Hip

A 2.5-year-old girl presents with a limp. Clinical examination and radiographs confirm a unilaterally dislocated left hip (Developmental Dysplasia of the Hip). What is the most appropriate definitive management?

. Pavlik harness application
. Closed reduction and spica casting
. Open reduction and spica casting
. Open reduction with a concomitant pelvic osteotomy
. Observation until skeletal maturity

Correct Answer & Explanation

. Pavlik harness application

Explanation

In children older than 18-24 months with an untreated DDH, open reduction is generally required, often combined with a pelvic osteotomy to address acetabular dysplasia, and occasionally a femoral shortening osteotomy.

Question 4710

Topic: 4. Pediatrics

A 7-year-old boy sustains a completely displaced extension-type supracondylar humerus fracture. On neurological examination, he is unable to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Which nerve is injured?

. Ulnar nerve
. Radial nerve
. Posterior interosseous nerve
. Anterior interosseous nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Ulnar nerve

Explanation

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type pediatric supracondylar humerus fractures, resulting in the inability to form the 'A-OK' sign.

Question 4711

Topic: Pediatric Upper Extremity & Spine

In the Lenke classification system for Adolescent Idiopathic Scoliosis (AIS), a proximal thoracic curve is considered 'structural' if it meets which of the following radiographic criteria?

. Residual curve >= 10 degrees on side bending
. Residual curve >= 15 degrees on side bending
. Residual curve >= 25 degrees on side bending
. Residual curve >= 35 degrees on side bending
. Flexible curve resolving to 0 degrees on side bending

Correct Answer & Explanation

. Residual curve >= 10 degrees on side bending

Explanation

According to the Lenke classification for AIS, minor curves are considered 'structural' if they do not bend out to less than 25 degrees on supine maximum side-bending radiographs (i.e., residual curve >= 25 degrees). For a proximal thoracic curve, another criterion for being structural is a regional kyphosis (T2-T5) of >= 20 degrees.

Question 4712

Topic: 4. Pediatrics

A 6-year-old girl is evaluated for bilateral cavovarus foot deformities and back pain. Physical examination reveals a sacral dimple with a hairy patch. MRI of the spine confirms the diagnosis of a tethered cord. To meet the radiographic definition of a tethered cord, the conus medullaris must terminate below which vertebral level in a child of this age?

. Above T12
. At L1
. Below L2
. At S1
. At S3

Correct Answer & Explanation

. Above T12

Explanation

In normal embryological development, the conus medullaris ascends and typically reaches its adult position at the T12-L1 or L1-L2 disc space by 2 to 3 months of age. A tethered spinal cord is radiographically diagnosed when the conus medullaris terminates abnormally low, generally defined as below the L2-L3 disc space, often accompanied by a thickened filum terminale (>2 mm).

Question 4713

Topic: Pediatric Upper Extremity & Spine

In the Lenke classification system for Adolescent Idiopathic Scoliosis (AIS), determining whether a curve is 'structural' or 'non-structural' is crucial for deciding which curves must be included in the fusion construct. To classify the Proximal Thoracic (PT) curve as structural, which of the following radiographic criteria must be met?

. The side-bending Cobb angle must be > 10 degrees OR T10-L2 kyphosis > 10 degrees.
. The side-bending Cobb angle must be > 35 degrees OR T2-T5 kyphosis > 10 degrees.
. The side-bending Cobb angle must be >= 25 degrees OR T5-T12 kyphosis >= +20 degrees.
. The side-bending Cobb angle must be >= 25 degrees OR T2-T5 kyphosis >= +20 degrees.
. The side-bending Cobb angle must be >= 15 degrees OR T10-L2 kyphosis >= +15 degrees.

Correct Answer & Explanation

. The side-bending Cobb angle must be > 10 degrees OR T10-L2 kyphosis > 10 degrees.

Explanation

In the Lenke classification, a minor curve is considered structural if it lacks adequate flexibility or is regionally kyphotic. Specifically, for the Proximal Thoracic (PT) curve, the criteria to be structural are a residual Cobb angle of >= 25 degrees on maximum side-bending radiographs OR regional kyphosis between T2 and T5 of >= +20 degrees. If either criterion is met, the PT curve is structural and generally must be included in the fusion construct.

Question 4714

Topic: Pediatric Upper Extremity & Spine

A 12-year-old premenarchal female with a Risser 0 score presents with an adolescent idiopathic scoliosis right thoracic curve of 32 degrees. Based on the BrAIST trial, what is the most appropriate management?

. Observation with 6-month serial radiographs
. Nighttime-only bending brace
. Thoracolumbosacral orthosis (TLSO) bracing for a minimum of 18 hours per day
. Posterior spinal fusion
. Anterior vertebral body tethering

Correct Answer & Explanation

. Observation with 6-month serial radiographs

Explanation

The BrAIST trial definitively showed that bracing significantly decreases the progression of high-risk AIS curves to the surgical threshold. Wearing a TLSO brace for at least 18 hours daily was highly correlated with treatment success.

Question 4715

Topic: Pediatric Upper Extremity & Spine
A 12-year-old premenarchal female presents with an adolescent idiopathic scoliosis right thoracic curve of 25 degrees. Her Risser stage is 0. According to the Lonstein and Carlson criteria, what is her approximate risk of curve progression to a surgical magnitude (>50 degrees)?
. < 10%
. 20-30%
. 40-50%
. 68%
. > 90%

Correct Answer & Explanation

. 68%

Explanation

In a premenarchal female who is Risser 0 with an AIS curve between 20 and 29 degrees, the risk of curve progression is exceptionally high, calculated to be approximately 68% by Lonstein and Carlson.

Question 4716

Topic: 4. Pediatrics

A pediatric patient's histologic evaluation of the physis shows a specific defect.

If the defect is characterized by a widened, unmineralized zone of provisional calcification and a characteristic 'cupped and frayed' appearance on radiographs, what is the most likely diagnosis?

. Slipped Capital Femoral Epiphysis (SCFE)
. Achondroplasia
. Rickets
. Salter-Harris type I fracture
. Mucopolysaccharidosis

Correct Answer & Explanation

. Slipped Capital Femoral Epiphysis (SCFE)

Explanation

Rickets is characterized by a defect in mineralization affecting the zone of provisional calcification in the physis. This leads to the accumulation of unmineralized osteoid and a classic 'cupped and frayed' metaphyseal appearance on radiographs. In contrast, achondroplasia affects the proliferative zone, and SCFE typically fails through the hypertrophic zone.

Question 4717

Topic: 4. Pediatrics

A 4-year-old boy presents with short stature, frontal bossing, and disproportionate rhizomelic shortening of his limbs. Genetic testing reveals a gain-of-function mutation in the FGFR3 gene. This mutation directly inhibits the normal function of which cellular layer in the growth plate?

. Resting zone
. Proliferative zone
. Hypertrophic zone (maturation)
. Hypertrophic zone (degeneration)
. Zone of provisional calcification

Correct Answer & Explanation

. Resting zone

Explanation

Achondroplasia is an autosomal dominant disorder caused by a gain-of-function mutation in Fibroblast Growth Factor Receptor 3 (FGFR3). This constitutively active receptor abnormally inhibits the proliferation of chondrocytes in the proliferative zone of the physis, leading to decreased endochondral ossification and rhizomelic dwarfism.

Question 4718

Topic: 4. Pediatrics

Achondroplasia is the most common recognizable form of short-limb dwarfism in orthopedic practice. The underlying genetic defect involves a mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. Which of the following accurately describes the molecular mechanism and classic inheritance pattern of this disorder?

. Loss-of-function mutation, autosomal recessive
. Loss-of-function mutation, autosomal dominant
. Gain-of-function mutation, autosomal recessive
. Gain-of-function mutation, autosomal dominant
. Dominant negative mutation, X-linked dominant

Correct Answer & Explanation

. Loss-of-function mutation, autosomal recessive

Explanation

Achondroplasia is caused by a gain-of-function mutation in the FGFR3 gene (most commonly a G to A transition at nucleotide 1138). Under normal conditions, FGFR3 inhibits chondrocyte proliferation. The gain-of-function mutation causes constitutive, unregulated inhibition of chondrocyte proliferation in the proliferative zone of the physis. It is inherited in an autosomal dominant manner (although 80% are de novo mutations).

Question 4719

Topic: 4. Pediatrics

Achondroplasia is the most common skeletal dysplasia and is inherited in an autosomal dominant pattern. It is caused by a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. How does this mutation specifically affect the growth plate (physis)?

. It accelerates apoptosis in the resting zone.
. It decreases chondrocyte proliferation in the proliferative zone.
. It inhibits type X collagen production in the hypertrophic zone.
. It impairs provisional calcification in the primary spongiosa.
. It prevents the formation of the secondary ossification center.

Correct Answer & Explanation

. It accelerates apoptosis in the resting zone.

Explanation

FGFR3 normally functions as a negative regulator of bone growth. A gain-of-function mutation causes constitutive, unchecked activation of the receptor, which severely inhibits chondrocyte proliferation and differentiation in the proliferative zone of the physis. This leads to a profound quantitative defect in longitudinal endochondral ossification, resulting in short-limb dwarfism.

Question 4720

Topic: 4. Pediatrics

Osteogenesis imperfecta typically results from a genetic mutation affecting Type I collagen synthesis. Which specific amino acid substitution is most commonly responsible for disrupting the triple helix structure?

. Proline substituted for Lysine
. Glycine substituted by a bulkier amino acid
. Hydroxyproline substituted for Glycine
. Lysine substituted for Arginine
. Glutamate substituted for Valine

Correct Answer & Explanation

. Proline substituted for Lysine

Explanation

Type I collagen forms a triple helix composed of repeating Glycine-X-Y sequences. Glycine is the smallest amino acid and must occupy every third position to fit inside the helix core; bulkier substitutions disrupt the helix.

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