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4. Pediatrics MCQs

Practice Set 268 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 5341

Topic: Pediatric Hip

In a 12-year-old obese male presenting with a stable slipped capital femoral epiphysis (SCFE), what is the most significant iatrogenic risk factor for the development of chondrolysis following treatment?

. Failure to perform a prophylactic pinning of the contralateral hip
. Use of a single cannulated screw for fixation
. Unrecognized intra-articular hardware penetration
. Performing a subtrochanteric osteotomy
. Delay in surgical fixation greater than 24 hours

Correct Answer & Explanation

. Unrecognized intra-articular hardware penetration

Explanation

Chondrolysis is a devastating complication of SCFE, most commonly associated with unrecognized intra-articular penetration of hardware during in situ pinning. Meticulous fluoroscopic evaluation (approach-withdrawal technique) is required to ensure the screw has not breached the joint.

Question 5342

Topic: 4. Pediatrics

On an infant's hip ultrasound for suspected Developmental Dysplasia of the Hip (DDH), the alpha angle is measured. According to Graf's classification, a normal, mature hip (Type 1) is defined by an alpha angle of at least:

. 43 degrees
. 50 degrees
. 55 degrees
. 60 degrees
. 65 degrees

Correct Answer & Explanation

. 60 degrees

Explanation

In Graf's ultrasound classification of the infant hip, the alpha angle measures the bony roof of the acetabulum. An alpha angle of 60 degrees or greater defines a normal, mature hip (Type 1). The beta angle measures the cartilaginous roof.

Question 5343

Topic: Pediatric Hip

A 4-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During follow-up, the mother notes the child is no longer kicking her knee straight on the treated side. Which aspect of harness positioning is the most likely cause of this complication?

. Excessive abduction
. Excessive hyperflexion
. Inadequate abduction
. Excessive internal rotation
. Excessive extension

Correct Answer & Explanation

. Excessive hyperflexion

Explanation

Excessive hyperflexion in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to a femoral nerve palsy. This manifests as an inability to actively extend the knee.

Question 5344

Topic: Pediatric Hip

A 9-year-old male presents with a slipped capital femoral epiphysis (SCFE). Given his young age, an endocrine etiology is suspected. Which of the following endocrinopathies is most frequently associated with atypical SCFE?

. Hyperthyroidism
. Hypothyroidism
. Cushing's syndrome
. Addison's disease
. Hyperparathyroidism

Correct Answer & Explanation

. Hypothyroidism

Explanation

Hypothyroidism is the most common endocrine disorder associated with SCFE. An endocrine workup is strongly indicated in SCFE patients presenting outside the typical age range (under 10 or over 16) or with bilateral involvement.

Question 5345

Topic: Pediatric Hip

A 4-month-old infant is being treated for developmental dysplasia of the hip (DDH) with a Pavlik harness. At the 2-week follow-up, the parents report the infant has stopped kicking the affected leg. Examination reveals absent active knee extension and no response to plantar stimulation on that side. What is the most appropriate next step in management?

. Switch immediately to a rigid hip spica cast
. Discontinue the harness and observe
. Adjust the harness to increase hip flexion
. Perform an immediate diagnostic ultrasound
. Schedule for urgent open reduction

Correct Answer & Explanation

. Discontinue the harness and observe

Explanation

Femoral nerve palsy is a known complication of excessive hyperflexion in a Pavlik harness. The standard management is to remove the harness and observe; nerve function typically recovers spontaneously within days to a few weeks.

Question 5346

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents with a completely displaced (Gartland type III) supracondylar humerus fracture. On initial exam, his hand is pale and pulseless. Following closed reduction and percutaneous pinning, the hand becomes warm and pink with a capillary refill of 2 seconds, but the radial pulse remains unpalpable. What is the most appropriate next step in management?
. Immediate vascular exploration
. Perform a CT angiogram of the upper extremity
. Open reduction and internal fixation to decompress the artery
. Observation and close clinical monitoring
. Remove the pins and cast the arm in extension

Correct Answer & Explanation

. Observation and close clinical monitoring

Explanation

In a pediatric supracondylar humerus fracture presenting with a 'pink, pulseless' hand after a successful anatomical reduction and stabilization, the extremity is well-perfused via collateral circulation. The standard of care is observation and close monitoring, as routine vascular exploration is not indicated if perfusion is adequate.

Question 5347

Topic: Pediatric Hip

In evaluating a child with Legg-Calve-Perthes disease, the Herring lateral pillar classification is used during the fragmentation stage to predict long-term outcomes. Which group is associated with the poorest prognosis for achieving a spherical, congruent hip joint?

. Group A
. Group B
. Group B/C border
. Group C
. Group D

Correct Answer & Explanation

. Group C

Explanation

The Herring lateral pillar classification determines prognosis based on the height of the lateral portion of the capital femoral epiphysis. Group C, characterized by >50% collapse of the lateral pillar height, carries the poorest prognosis and highest risk of aspherical femoral head development.

Question 5348

Topic: Pediatric Hip

In the evaluation and management of Legg-Calve-Perthes disease, which of the following represents the most significant prognostic factor for the long-term congruency of the hip joint?

. Age of the patient at the onset of the disease
. Gender of the patient
. Duration of the initial limp
. Body mass index
. Presence of bilateral involvement

Correct Answer & Explanation

. Age of the patient at the onset of the disease

Explanation

The age at disease onset is the most critical prognostic factor in Perthes disease. Children under the age of 6 at onset have a greater potential for remodeling and generally achieve better long-term outcomes than older children.

Question 5349

Topic: Pediatric Hip

During an anterolateral (Smith-Petersen) open reduction of a developmental dysplasia of the hip (DDH) in an 18-month-old child, the surgeon encounters an extra-articular block to reduction. Which structure must be formally isolated and released to safely expose the inferior capsule?

. Ligamentum teres
. Transverse acetabular ligament
. Iliopsoas tendon
. Reflected head of the rectus femoris
. Gluteus medius

Correct Answer & Explanation

. Iliopsoas tendon

Explanation

The iliopsoas tendon crosses the anterior joint capsule and restricts inferior access and reduction. It must be released or lengthened to allow adequate exposure of the capsule and to facilitate a concentric reduction.

Question 5350

Topic: 4. Pediatrics

A 15-year-old male develops tachycardia, hypercarbia, and severe muscle rigidity shortly after the administration of succinylcholine during induction for fracture fixation. Which genetic mutation is most commonly responsible for this life-threatening condition?

. COL1A1 gene mutation
. FGFR3 gene mutation
. RYR1 gene mutation
. COMP gene mutation
. FBN1 gene mutation

Correct Answer & Explanation

. RYR1 gene mutation

Explanation

Malignant hyperthermia is an autosomal dominant pharmacogenetic disorder primarily caused by a mutation in the RYR1 (ryanodine receptor) gene. This mutation leads to massive intracellular calcium release in skeletal muscle when exposed to triggering agents like succinylcholine or volatile anesthetics.

Question 5351

Topic: 4. Pediatrics

In a Salter-Harris type II fracture, the fracture line travels through the physis and exits through the metaphysis. Which histologic zone of the physis does the fracture line typically propagate through before exiting?

. Reserve zone
. Proliferative zone
. Zone of hypertrophy
. Zone of provisional calcification
. Primary spongiosa

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

Fractures through the physis typically propagate through the zone of hypertrophy because it is the weakest area due to the lack of collagen and large volume of extracellular matrix. The fracture then exits through the metaphysis in a Salter-Harris II pattern.

Question 5352

Topic: 4. Pediatrics

A 3-year-old boy is diagnosed with the most common form of short-limb dwarfism. Radiographs show narrowing of the interpedicular distances in the lumbar spine. This condition is caused by a mutation in the gene encoding for which of the following?

. Cartilage oligomeric matrix protein (COMP)
. Fibroblast growth factor receptor 3 (FGFR3)
. Type I collagen (COL1A1)
. Core-binding factor subunit alpha-1 (CBFA1)
. Diastrophic dysplasia sulfate transporter (DTDST)

Correct Answer & Explanation

. Fibroblast growth factor receptor 3 (FGFR3)

Explanation

Achondroplasia is an autosomal dominant condition caused by a gain-of-function mutation in FGFR3, which inhibits chondrocyte proliferation in the proliferative zone of the physis. This results in rhizomelic dwarfism and narrowing of interpedicular distances from L1 to L5.

Question 5353

Topic: 4. Pediatrics
A 10-year-old sustains a severe axial load injury to the ankle. Initial radiographs appear unremarkable, but the child develops premature closure of the distal tibial physis over the following year. This injury pattern best corresponds to which Salter-Harris classification?
. Salter-Harris I
. Salter-Harris II
. Salter-Harris III
. Salter-Harris IV
. Salter-Harris V

Correct Answer & Explanation

. Salter-Harris V

Explanation

Salter-Harris V injuries involve a crush or compression of the growth plate (physis). They are notoriously difficult to diagnose acutely because initial radiographs often appear normal. They carry a high risk of premature physeal closure and growth arrest.

Question 5354

Topic: 4. Pediatrics
A 6-year-old child presents with anterolateral bowing of the tibia and a pseudoarthrosis. Physical examination reveals multiple hyperpigmented macules on the trunk. This underlying genetic condition is inherited in what pattern?
. Autosomal recessive
. X-linked recessive
. Autosomal dominant
. X-linked dominant
. Mitochondrial inheritance

Correct Answer & Explanation

. Autosomal dominant

Explanation

The presentation of anterolateral bowing of the tibia, congenital pseudoarthrosis, and café-au-lait spots is highly characteristic of Neurofibromatosis type 1 (NF1). NF1 is an autosomal dominant disorder caused by a mutation in the neurofibromin gene on chromosome 17.

Question 5355

Topic: 4. Pediatrics

A 6-week-old infant is placed in a Pavlik harness for developmental dysplasia of the hip. At the 2-week follow-up, the mother notes the child no longer kicks the affected leg. On examination, the infant lacks active knee extension. What is the most appropriate next step in management?

. Immediately transition to a rigid hip spica cast
. Loosen the anterior straps to decrease hip flexion
. Loosen the posterior straps to decrease hip abduction
. Perform a hip ultrasound to check for a septic effusion
. Discontinue the harness temporarily and observe for return of function

Correct Answer & Explanation

. Discontinue the harness temporarily and observe for return of function

Explanation

The infant has developed a femoral nerve palsy, a known complication of hyperflexion in a Pavlik harness. The most appropriate immediate management is to discontinue the harness until motor function fully returns (which typically occurs within a few days to weeks), after which alternative treatment or modified harness therapy can be reassessed.

Question 5356

Topic: Pediatric Hip

Prophylactic in situ pinning of the contralateral, asymptomatic hip in a patient with a unilateral Slipped Capital Femoral Epiphysis (SCFE) is most strongly indicated in which of the following scenarios?

. A 12-year-old obese male with idiopathic SCFE
. A 14-year-old female with a strong family history of SCFE
. An 11-year-old male with renal osteodystrophy
. A 15-year-old male competitive athlete
. A 10-year-old female with an acute-on-chronic slip

Correct Answer & Explanation

. An 11-year-old male with renal osteodystrophy

Explanation

Prophylactic pinning of the contralateral hip in SCFE is strongly recommended for patients with underlying endocrine or metabolic disorders (e.g., hypothyroidism, renal osteodystrophy, previous radiation therapy, growth hormone deficiency), as these patients have a much higher risk (approaching 100% in some conditions) of developing a contralateral slip.

Question 5357

Topic: 4. Pediatrics

In the evaluation of a child with Legg-Calve-Perthes disease, the presence of Catterall 'head-at-risk' signs indicates a higher likelihood of femoral head deformation and a poorer prognosis. Which of the following is considered one of these classic signs?

. Medial joint space narrowing
. Gage sign
. Subchondral fracture line confined to the anterior half of the epiphysis
. Enlargement of the femoral head (coxa magna)
. Intact lateral pillar

Correct Answer & Explanation

. Gage sign

Explanation

Catterall 'head-at-risk' signs are radiographic indicators of a poor prognosis in Legg-Calve-Perthes disease. They include the Gage sign (a V-shaped radiolucent defect in the lateral epiphysis and adjacent metaphysis), calcification lateral to the epiphysis, lateral subluxation of the femoral head, horizontal orientation of the physis, and the presence of a metaphyseal cyst.

Question 5358

Topic: 4. Pediatrics

A patient with achondroplasia presents for orthopedic evaluation. The condition is caused by a dominant mutation in the FGFR3 gene. What is the precise cellular effect of this mutation on the physeal growth plate?

. Inhibition of chondrocyte proliferation in the proliferative zone
. Failure of chondrocyte hypertrophy in the hypertrophic zone
. Accelerated osteoblast apoptosis in the primary spongiosa
. Overproduction of type X collagen in the resting zone
. Premature vascular invasion of the epiphysis

Correct Answer & Explanation

. Inhibition of chondrocyte proliferation in the proliferative zone

Explanation

Achondroplasia is caused by a gain-of-function mutation in FGFR3, which paradoxically leads to excessive inhibition of chondrocyte proliferation in the proliferative zone of the physis, resulting in decreased endochondral ossification and characteristic rhizomelic dwarfism.

Question 5359

Topic: 4. Pediatrics

A 5-year-old child with blue sclerae, dentinogenesis imperfecta, and multiple fractures is diagnosed with Osteogenesis Imperfecta (Type I). This condition is primarily caused by a quantitative defect in which of the following structural proteins?

. Type II collagen
. Type I collagen
. Fibrillin-1
. Elastin
. Aggrecan

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis Imperfecta (OI) is caused by mutations in the COL1A1 or COL1A2 genes, leading to qualitative or quantitative defects in Type I collagen. Type I OI is the most common and mildest form, typically characterized by a quantitative deficiency of normal Type I collagen.

Question 5360

Topic: 4. Pediatrics

A 4-year-old child presents with frequent fractures, blue sclerae, and dentinogenesis imperfecta. Genetic testing reveals a mutation in the COL1A1 gene. Which of the following structural proteins is primarily defective in this condition?

. Type I collagen
. Type II collagen
. Type X collagen
. Fibroblast growth factor receptor 3
. Cartilage oligomeric matrix protein

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta is most commonly caused by mutations in the COL1A1 or COL1A2 genes, resulting in defective or decreased type I collagen. Type I collagen is the primary organic component of bone.

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