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4. Pediatrics MCQs

Practice Set 176 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 3501

Topic: 4. Pediatrics
A 19-year-old male collegiate basketball player presents for evaluation of a knee injury. On physical examination, he is noted to have a tall stature, arachnodactyly, pectus excavatum, and generalized joint hypermobility. He also reports a history of lens dislocation. The defective protein in this underlying genetic condition is most critical for the structural integrity of which of the following?
. Type I collagen
. Type III collagen
. Elastin microfibrils
. Fibroblast growth factor receptor 3 (FGFR3)
. Cartilage oligomeric matrix protein (COMP)

Correct Answer & Explanation

. Elastin microfibrils

Explanation

The clinical features (tall stature, arachnodactyly, pectus excavatum, joint hypermobility, ectopia lentis) are hallmark signs of Marfan syndrome. Marfan syndrome is an autosomal dominant connective tissue disorder caused by mutations in the FBN1 gene, which encodes fibrillin-1. Fibrillin-1 is a glycoprotein that serves as the essential structural scaffold for elastin microfibrils in the extracellular matrix, most notably affecting the aorta, ligaments, and ciliary zonules. Defective Type I collagen causes Osteogenesis Imperfecta.

Question 3502

Topic: 4. Pediatrics

A 5-year-old child presents with disproportionate short stature, rhizomelic shortening of the limbs, and frontal bossing. Radiographs show narrowing of the interpedicular distances in the lumbar spine. Which of the following genetic mutations is primarily responsible for this condition?

. Defect in the COL1A1 gene
. Gain-of-function mutation in the FGFR3 gene
. Loss-of-function mutation in the RUNX2 gene
. Defect in the COMP gene
. Defect in the EXT1 gene

Correct Answer & Explanation

. Gain-of-function mutation in the FGFR3 gene

Explanation

Achondroplasia is caused by a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. This mutation leads to constitutional activation of the receptor, which subsequently inhibits chondrocyte proliferation and differentiation in the growth plate, primarily affecting endochondral ossification. COL1A1 mutations cause Osteogenesis Imperfecta; RUNX2 mutations cause Cleidocranial Dysplasia; COMP mutations are associated with Pseudoachondroplasia.

Question 3503

Topic: 4. Pediatrics



A 13-year-old boy with a BMI in the 99th percentile presents with hip pain and a diagnosis of a slipped capital femoral epiphysis (SCFE). The pathological mechanical failure in this condition occurs primarily through which specific histologic zone of the proximal femoral physis?

. Reserve (resting) zone
. Proliferative zone
. Hypertrophic zone
. Calcified zone
. Primary spongiosa

Correct Answer & Explanation

. Hypertrophic zone

Explanation

SCFE represents a type I Salter-Harris equivalent injury that typically fails through the hypertrophic zone of the physis. This zone is mechanically the weakest because it lacks substantial collagen and has a high matrix-to-cell volume ratio.

Question 3504

Topic: 4. Pediatrics

A 4-year-old boy presents with disproportionate short stature, rhizomelic shortening of the limbs, and frontal bossing. A mutation in which of the following genes is most likely responsible for his condition?

. COL1A1
. COMP
. FGFR3
. RUNX2
. SOX9

Correct Answer & Explanation

. FGFR3

Explanation

Achondroplasia is caused by an activating mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. This leads to the inhibition of chondrocyte proliferation in the proliferative zone of the physis.

Question 3505

Topic: 4. Pediatrics

A 2-year-old child presents with bowing of the lower extremities and widening of the wrists. Laboratory testing shows normal serum calcium, significantly decreased serum phosphate, and elevated alkaline phosphatase. Which zone of the physis is most significantly expanded in this condition?

. Reserve zone
. Proliferative zone
. Zone of maturation
. Zone of provisional calcification
. Zone of hypertrophy

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

In hypophosphatemic Rickets, there is a failure of mineralization in the zone of provisional calcification. This leads to a massive expansion and architectural disorganization of the zone of hypertrophy.

Question 3506

Topic: 4. Pediatrics

In a growing child, a slipped capital femoral epiphysis (SCFE) occurs predominantly through a mechanical failure in which distinct cellular zone of the growth plate?

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

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

The zone of hypertrophy is mechanically the weakest layer of the physis due to its high volume of large cells and lack of dense matrix calcification. Physeal fractures and conditions like SCFE typically shear through this zone.

Question 3507

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy sustains a displaced supracondylar humerus fracture. Post-reduction, he is unable to form an "OK" sign with his thumb and index finger. The affected nerve innervates which of the following muscle groups?

. Flexor pollicis longus, flexor digitorum profundus (index and middle), and pronator quadratus
. Flexor pollicis brevis, flexor digitorum superficialis, and pronator teres
. Flexor carpi radialis, flexor pollicis longus, and flexor digitorum profundus (ring and small)
. Abductor pollicis longus, extensor pollicis brevis, and supinator
. Flexor digitorum profundus (all digits) and pronator quadratus

Correct Answer & Explanation

. Flexor pollicis longus, flexor digitorum profundus (index and middle), and pronator quadratus

Explanation

The inability to form the "OK" sign indicates an Anterior Interosseous Nerve (AIN) palsy. The AIN is a motor branch of the median nerve that innervates the flexor pollicis longus, the radial half of the flexor digitorum profundus, and the pronator quadratus.

Question 3508

Topic: Pediatric Hip

In a 12-year-old boy undergoing in situ pinning for a slipped capital femoral epiphysis (SCFE), the surgeon must avoid the terminal branches of the medial femoral circumflex artery. These crucial retinacular vessels typically penetrate the proximal femur at which anatomic location?

. Inferomedial aspect of the femoral neck
. Posterosuperior aspect of the femoral neck
. Anterolateral aspect of the femoral neck
. Ligamentum teres
. Lesser trochanter

Correct Answer & Explanation

. Posterosuperior aspect of the femoral neck

Explanation

The primary blood supply to the femoral head comes from the lateral epiphyseal artery, a terminal branch of the medial femoral circumflex artery. These vessels penetrate the capsule and enter the bone at the posterosuperior aspect of the femoral neck.

Question 3509

Topic: 4. Pediatrics

An 11-year-old Little League baseball pitcher presents with vague, gradual onset shoulder pain in his throwing arm. Radiographs reveal widening of the proximal humeral physis compared to the contralateral shoulder. What is the most appropriate initial management?

. Arthroscopic labral repair
. Immediate physical therapy focusing on weighted plyometrics
. Corticosteroid injection into the subacromial space
. Complete cessation of throwing for 3 to 6 months
. Percutaneous pinning of the physis

Correct Answer & Explanation

. Complete cessation of throwing for 3 to 6 months

Explanation

Little Leaguer's shoulder is an epiphysiolysis of the proximal humerus caused by repetitive rotational microtrauma. The gold standard treatment is complete rest from throwing until symptoms resolve and the physis appears normal on radiographs.

Question 3510

Topic: Pediatric Upper Extremity & Spine

A 12-year-old Little League pitcher complains of progressively worsening medial elbow pain. Radiographs demonstrate widening of the medial epicondyle apophysis without significant displacement. What is the most appropriate initial management?

. Ulnar collateral ligament reconstruction
. Ulnar collateral ligament repair with internal bracing
. Complete cessation of throwing for 4 to 6 weeks
. Physical therapy with continued throwing at lower velocities
. Intra-articular corticosteroid injection

Correct Answer & Explanation

. Complete cessation of throwing for 4 to 6 weeks

Explanation

Medial epicondyle apophysitis (Little League Elbow) in a skeletally immature throwing athlete is an overuse injury. The most critical initial treatment is complete cessation of throwing (rest) for 4 to 6 weeks, followed by a gradual return-to-throwing program.

Question 3511

Topic: 4. Pediatrics

During a transphyseal anterior cruciate ligament (ACL) reconstruction in an 11-year-old patient with wide-open physes, placing the tibial tunnel too vertically increases the risk of injuring which structure, potentially leading to which deformity?

. Proximal tibial physis; genu valgum
. Proximal tibial physis; genu varum
. Tibial tubercle apophysis; genu recurvatum
. Tibial tubercle apophysis; genu flexum
. Distal femoral physis; limb length discrepancy

Correct Answer & Explanation

. Proximal tibial physis; genu varum

Explanation

A steep, vertical tibial tunnel risks violating the anteriorly located tibial tubercle apophysis. Premature closure of the anterior aspect of the proximal tibial physis leads to a genu recurvatum deformity as the posterior physis continues to grow.

Question 3512

Topic: Pediatric Hip
A 26-year-old male hockey player presents with chronic groin pain exacerbated by hip flexion and internal rotation. Radiographs reveal a prominent alpha angle of 75 degrees on the modified Dunn view. This radiographic finding is characteristic of which pathology?
. Pincer impingement
. Cam impingement
. Acetabular dysplasia
. Slipped capital femoral epiphysis
. Legg-Calvรฉ-Perthes disease

Correct Answer & Explanation

. Cam impingement

Explanation

An increased alpha angle (typically >50-55 degrees) indicates an aspherical femoral head-neck junction. This is the anatomical hallmark of Cam-type femoroacetabular impingement (FAI).

Question 3513

Topic: Pediatric Hip

A 13-year-old boy presents with severe groin pain and inability to bear weight on his right leg after a minor fall 2 days ago. Radiographs reveal an unstable slipped capital femoral epiphysis (SCFE). To minimize the risk of avascular necrosis, what is the most appropriate management?

. Immediate closed reduction and spica casting.
. Delayed in situ single-screw fixation to allow swelling to subside.
. Urgent joint decompression and single-screw fixation.
. Skeletal traction for 2 weeks followed by percutaneous pinning.
. Multiple-pass pinning across the physis to ensure maximal stability.

Correct Answer & Explanation

. Urgent joint decompression and single-screw fixation.

Explanation

Unstable SCFE (inability to bear weight) carries a high risk of avascular necrosis. Current evidence supports urgent stabilization with joint capsulotomy (decompression) or an open reduction via a modified Dunn approach to relieve intracapsular pressure and preserve blood supply.

Question 3514

Topic: Pediatric Hip
An 8-year-old boy presents with a painless limp and is diagnosed with Legg-Calvรฉ-Perthes disease. Radiographs reveal that the lateral pillar of the femoral head is maintained at 60% of its normal height. According to the Herring classification, what is his group and recommended management?
. Group A; observation and symptomatic management.
. Group B; surgical containment is recommended given his age.
. Group C; surgical containment is recommended regardless of age.
. Group C; observation, as surgical outcomes are poor.
. Group B/C border; physical therapy and non-weight-bearing bracing.

Correct Answer & Explanation

. Group B; surgical containment is recommended given his age.

Explanation

A lateral pillar height of 60% places the patient in Herring Group B (50-100% maintenance). For children 8 years and older at the time of onset, Group B hips show significantly better outcomes with surgical containment compared to conservative management.

Question 3515

Topic: Pediatric Hip

A 4-week-old girl is being treated with a Pavlik harness for developmental dysplasia of the left hip. At her 2-week follow-up, she is noted to have decreased active extension of the left knee and an absent patellar reflex. What is the most likely cause of this finding?

. Avascular necrosis of the femoral head.
. Femoral nerve palsy from excessive hip flexion.
. Sciatic nerve palsy from excessive hip extension.
. Obturator nerve palsy from excessive hip abduction.
. Iatrogenic septic arthritis.

Correct Answer & Explanation

. Femoral nerve palsy from excessive hip flexion.

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by hyperflexion of the hip compressing the nerve against the inguinal ligament. Management involves temporary removal or loosening of the anterior straps.

Question 3516

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy sustains a completely displaced extension-type supracondylar humerus fracture. Prior to reduction, the hand is pink but pulseless. After closed reduction and percutaneous pinning, the hand remains pink and pulseless with capillary refill of 2 seconds. What is the next best step in management?

. Immediate open vascular exploration.
. CT angiography of the upper extremity.
. Observation with close clinical monitoring.
. Removal of the pins and attempting a second closed reduction.
. Prophylactic volar forearm fasciotomy.

Correct Answer & Explanation

. Observation with close clinical monitoring.

Explanation

A 'pink, pulseless' hand following an anatomic reduction of a supracondylar humerus fracture indicates adequate collateral perfusion. Close observation is indicated, as routine vascular exploration is unnecessary unless the hand becomes pale and poorly perfused.

Question 3517

Topic: Pediatric Upper Extremity & Spine

A 12-year-old premenarchal girl is evaluated for adolescent idiopathic scoliosis. Radiographs demonstrate a 35-degree right thoracic curve, and her Risser stage is 0. What is the most appropriate management?

. Observation with repeat standing radiographs in 6 months.
. Schroth physical therapy as the primary standalone treatment.
. Thoracolumbosacral orthosis (TLSO) bracing.
. Posterior spinal fusion with pedicle screw instrumentation.
. Vertebral body tethering.

Correct Answer & Explanation

. Thoracolumbosacral orthosis (TLSO) bracing.

Explanation

In a skeletally immature patient (Risser 0-2, premenarchal) with an adolescent idiopathic scoliosis curve between 25 and 40 degrees, rigid bracing (TLSO) is the standard of care to halt curve progression and reduce the need for surgery.

Question 3518

Topic: 4. Pediatrics

A 6-year-old boy with spastic quadriplegic cerebral palsy (GMFCS Level V) is undergoing routine hip surveillance. Radiographs show a migration percentage of 45% bilaterally. He has no pain but exhibits limited hip abduction. What is the most appropriate surgical intervention?

. Bilateral adductor and iliopsoas tenotomies alone.
. Bilateral varus derotational osteotomies (VDRO) with pelvic osteotomies.
. Bilateral proximal femoral resection interposition arthroplasties.
. Observation and bilateral botulinum toxin injections.
. Selective dorsal rhizotomy.

Correct Answer & Explanation

. Bilateral varus derotational osteotomies (VDRO) with pelvic osteotomies.

Explanation

In children with cerebral palsy, a hip migration percentage >40% typically indicates failing soft-tissue containment. Bony reconstruction with a proximal femoral VDRO and a pelvic osteotomy (e.g., Dega or San Diego) is required to stabilize the hip.

Question 3519

Topic: 4. Pediatrics
A 3-year-old girl with recurrent fractures, blue sclerae, and dentinogenesis imperfecta has severe anterolateral bowing of her femurs preventing ambulation. She is diagnosed with osteogenesis imperfecta type III. What is the surgical treatment of choice for her deformities?
. Bilateral circular external fixation.
. Prolonged spica casting to induce remodeling.
. Multiple corrective osteotomies with intramedullary telescopic rodding.
. Unilateral rigid locked antegrade nailing.
. Submuscular bridge plating of the femurs.

Correct Answer & Explanation

. Multiple corrective osteotomies with intramedullary telescopic rodding.

Explanation

In osteogenesis imperfecta, severe long bone deformities are best treated with realignment via multiple osteotomies (Sofield-Millar procedure). Fixation with telescopic intramedullary rods (e.g., Fassier-Duval) is preferred as they accommodate patient growth.

Question 3520

Topic: Pediatric Hip

A 12-year-old obese boy presents with acute left hip pain and inability to bear weight after a minor fall. Radiographs show a severe slipped capital femoral epiphysis. He is unable to walk even with crutches. What is the most significant complication associated with this specific presentation compared to a patient who can bear weight?

. Chondrolysis
. Avascular necrosis
. Premature osteoarthritis
. Limb length discrepancy
. Infection

Correct Answer & Explanation

. Avascular necrosis

Explanation

An unstable SCFE is defined by the inability to bear weight. This presentation carries a significantly higher risk of avascular necrosis (up to 47%) compared to stable SCFE.

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