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4. Pediatrics MCQs

Practice Set 283 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 5641

Topic: 4. Pediatrics
The lateral pillar classification (Herring) is widely used to determine the prognosis in Legg-Calvรฉ-Perthes disease. This classification is based on the radiolucency and height of which anatomical structure on the AP pelvis radiograph?
. The medial third of the capital femoral epiphysis
. The central third of the capital femoral epiphysis
. The lateral third of the capital femoral epiphysis
. The lateral aspect of the physeal plate
. The superolateral aspect of the acetabulum

Correct Answer & Explanation

. The lateral third of the capital femoral epiphysis

Explanation

The Herring Lateral Pillar classification divides the capital femoral epiphysis into three pillars (medial, central, and lateral). The classification depends on the degree of height loss in the lateral third of the capital femoral epiphysis, as it is the most critical weight-bearing portion. Greater height loss (Groups B and C) correlates with a worse prognosis.

Question 5642

Topic: 4. Pediatrics

Adolescent Blount disease is an acquired disorder of the proximal tibial physis resulting in a progressive varus deformity. According to the Heuter-Volkmann principle, what is the primary pathophysiological driver of this condition?

. Tension across the lateral aspect of the physis stimulating excessive bone growth
. Excessive compressive forces across the medial aspect of the physis inhibiting growth
. A genetic defect in type X collagen causing premature physeal arrest
. Repetitive avulsion microtrauma at the tibial tubercle
. Avascular necrosis of the medial tibial epiphysis due to a compromised blood supply

Correct Answer & Explanation

. Excessive compressive forces across the medial aspect of the physis inhibiting growth

Explanation

The Heuter-Volkmann principle states that increased compressive forces inhibit physeal growth, while tension stimulates it. In Blount disease (especially in obese patients), excessive weight places extreme compressive loads on the medial proximal tibial physis, inhibiting its growth and resulting in progressive tibia vara.

Question 5643

Topic: 4. Pediatrics

A 12-year-old obese male presents with knee pain and obligatory external rotation during passive hip flexion, consistent with a slipped capital femoral epiphysis (SCFE). Why is in-situ pinning preferred over open anatomical reduction for standard, stable slips?

. To prevent postoperative chondrolysis
. To minimize the risk of avascular necrosis (AVN) of the femoral head
. To avoid premature physeal closure
. To decrease the risk of a contralateral slip
. To accelerate physiological remodeling of the femoral neck

Correct Answer & Explanation

. To minimize the risk of avascular necrosis (AVN) of the femoral head

Explanation

Forceful anatomical reduction stretches or kinks the delicate retinacular blood supply to the femoral epiphysis, significantly increasing the risk of avascular necrosis (AVN).

Question 5644

Topic: Pediatric Hip

In a patient presenting with a slipped capital femoral epiphysis (SCFE), what is the most typical direction of epiphyseal displacement relative to the femoral neck?

. Anterior and superior
. Posterior and inferior
. Anterior and inferior
. Posterior and superior
. Purely lateral

Correct Answer & Explanation

. Posterior and inferior

Explanation

In SCFE, the metaphysis (femoral neck) typically displaces anteriorly and superiorly. This results in the capital femoral epiphysis being anatomically positioned posterior and inferior relative to the neck.

Question 5645

Topic: 4. Pediatrics
In the evaluation of an infant for Developmental Dysplasia of the Hip (DDH), static ultrasound imaging is standard. Which specific ultrasound measurement quantifies the bony acetabular roof concavity and must be >60 degrees to be considered normal (Graf Type I)?
. Beta angle
. Alpha angle
. Center-edge angle
. Tonnis angle
. Neck-shaft angle

Correct Answer & Explanation

. Alpha angle

Explanation

In the Graf ultrasound classification for infant hips, the alpha angle measures the osseous roof of the acetabulum. An alpha angle of 60 degrees or greater indicates a normal, mature hip.

Question 5646

Topic: Pediatric Hip

A 13-year-old obese male presents with acute exacerbation of chronic knee pain and an inability to bear weight. The affected leg is held in external rotation. What is the most severe potential complication of the definitive surgical treatment for his underlying condition?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Premature closure of the triradiate cartilage
. Femoral shaft fracture
. Slipped contralateral epiphysis

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

The patient has an unstable Slipped Capital Femoral Epiphysis (SCFE) characterized by the inability to bear weight. The most devastating complication of an unstable SCFE and its surgical stabilization is avascular necrosis (AVN) of the femoral head.

Question 5647

Topic: Pediatric Hip

A 6-month-old female with developmental dysplasia of the hip (DDH) is treated with a Pavlik harness. During a follow-up visit, she demonstrates an inability to actively extend her knee. Which of the following is the most appropriate next step?

. Continue the harness but decrease the hip flexion angle
. Immediate removal of the Pavlik harness
. Apply a rigid hip spica cast
. Perform a closed reduction under general anesthesia
. Perform an open reduction with a pelvic osteotomy

Correct Answer & Explanation

. Immediate removal of the Pavlik harness

Explanation

An inability to actively extend the knee indicates a femoral nerve palsy, a severe complication of the Pavlik harness typically caused by excessive hip flexion. Its occurrence requires the immediate cessation of harness treatment to allow the nerve to recover.

Question 5648

Topic: Pediatric Hip

A 13-year-old obese male presents with left groin pain and a limp for 3 weeks. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE). Which of the following physical exam findings is most characteristic of this condition?

. Obligatory internal rotation of the hip with passive flexion
. Obligatory external rotation of the hip with passive flexion
. Increased hip abduction in extension
. Severe pain with passive ankle dorsiflexion
. Positive Trendelenburg sign on the contralateral side

Correct Answer & Explanation

. Obligatory external rotation of the hip with passive flexion

Explanation

Patients with SCFE typically demonstrate obligatory external rotation as the affected hip is passively flexed. This occurs because the femoral neck displaces anteriorly and externally rotates relative to the capital femoral epiphysis.

Question 5649

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy sustains a completely displaced supracondylar humerus fracture. After closed reduction and percutaneous pinning, the radial pulse remains unpalpable, but the hand is warm, pink, and has a capillary refill of less than 2 seconds. What is the most appropriate next step in management?

. Immediate exploration of the brachial artery
. Administration of intra-arterial vasodilators
. Observation and admission for close neurovascular monitoring
. Removal of pins and open reduction
. Compartment fasciotomies of the forearm

Correct Answer & Explanation

. Observation and admission for close neurovascular monitoring

Explanation

A 'pulseless but pink' and well-perfused hand following a properly reduced supracondylar humerus fracture typically indicates adequate collateral circulation. The standard of care is close inpatient observation rather than immediate vascular exploration.

Question 5650

Topic: 4. Pediatrics

A 12-year-old child presents with multiple fractures, diffuse sclerosis on radiographs (bone-within-bone appearance), and mild anemia. The pathophysiology of this disease most likely involves a defect in which of the following?

. Type I collagen triple helix formation
. Fibroblast growth factor receptor 3 (FGFR3)
. Carbonic anhydrase II leading to defective osteoclast ruffled borders
. Cartilage oligomeric matrix protein (COMP)
. Fibrillin-1

Correct Answer & Explanation

. Carbonic anhydrase II leading to defective osteoclast ruffled borders

Explanation

The patient has osteopetrosis (marble bone disease). The primary defect is failure of osteoclastic bone resorption due to an inability to acidify the Howship lacuna. This is frequently caused by a mutation in Carbonic Anhydrase II or TCIRG1, resulting in osteoclasts that lack a functioning ruffled border.

Question 5651

Topic: 4. Pediatrics

In the growing pediatric skeleton, through which specific histological zone of the physis do typical Salter-Harris fractures most commonly propagate?

. Reserve (resting) zone
. Proliferative zone
. Zone of maturation
. Zone of provisional calcification
. Zone of hypertrophy

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

Salter-Harris fractures typically propagate through the zone of hypertrophy in the physis. This zone is mechanically the weakest because the chondrocytes undergo massive enlargement (hypertrophy), leaving very little intercellular matrix to resist applied shearing forces.

Question 5652

Topic: 4. Pediatrics

A 5-year-old boy with spastic quadriplegic cerebral palsy (GMFCS level V) is evaluated for hip displacement. His pelvic radiograph shows a Reimer's migration index of 45% bilaterally. What is the most appropriate management?

. Observation and repeat radiograph in 1 year
. Bilateral adductor and iliopsoas tenotomies
. Bilateral varus derotational osteotomies (VDRO) with pelvic osteotomies
. Bilateral proximal femoral resection (Girdlestone)
. Botulinum toxin injections to the adductors

Correct Answer & Explanation

. Bilateral varus derotational osteotomies (VDRO) with pelvic osteotomies

Explanation

In cerebral palsy, a Reimer's migration percentage >40-50% in a child generally warrants bony reconstructive surgery (VDRO and often a pelvic osteotomy like Dega or San Diego) to prevent painful dislocation. Soft tissue releases alone are typically reserved for migration <30-40% in younger children (under 4-5 years).

Question 5653

Topic: 4. Pediatrics

A child with short-limbed dwarfism, frontal bossing, and midface hypoplasia presents to the clinic. Radiographs reveal narrowing of the interpedicular distances in the lumbar spine. Which region of the growth plate is primarily affected by the genetic mutation underlying this condition?

. Resting zone
. Proliferative zone
. Hypertrophic zone
. Zone of provisional calcification
. Primary spongiosa

Correct Answer & Explanation

. Proliferative zone

Explanation

Achondroplasia is caused by a gain-of-function mutation in the FGFR3 gene. Overactivity of FGFR3 severely inhibits chondrocyte proliferation. Therefore, the proliferative zone of the physis is the primarily affected layer in this disorder.

Question 5654

Topic: 4. Pediatrics

A 2-year-old child presents with multiple fractures of varying ages, blue sclerae, and hearing loss. A defect in which of the following cellular processes is primarily responsible for the pathophysiology of Osteogenesis Imperfecta?

. Synthesis of type II collagen
. Cleavage of type I procollagen C-propeptides
. Assembly of the type I collagen triple helix
. Mineralization of osteoid by osteoblasts
. Differentiation of mesenchymal stem cells into osteoblasts

Correct Answer & Explanation

. Assembly of the type I collagen triple helix

Explanation

Osteogenesis Imperfecta is most commonly caused by mutations in the COL1A1 or COL1A2 genes, which result in the substitution of glycine by bulkier amino acids. This substitution disrupts the proper assembly and folding of the type I collagen triple helix inside the rough endoplasmic reticulum.

Question 5655

Topic: 4. Pediatrics

Achondroplasia is the most common form of short-limbed dwarfism. The underlying pathophysiology of this condition is primarily associated with a mutation in which of the following genes, and what zone of the physis is most affected?

. COMP gene; resting zone
. COL1A1 gene; hypertrophic zone
. FGFR3 gene; proliferative zone
. SOX9 gene; zone of provisional calcification
. PTHrP gene; reserve zone

Correct Answer & Explanation

. FGFR3 gene; proliferative zone

Explanation

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

Question 5656

Topic: 4. Pediatrics
A 4-year-old child presents with a history of multiple low-energy fractures, blue sclerae, and normal teeth. According to the Sillence classification, this patient most likely has Osteogenesis Imperfecta (OI) Type I. Which of the following best describes the collagen defect in this specific type of OI?
. Quantitative defect (decreased amount) of normal type I collagen
. Qualitative defect (abnormal structure) of type I collagen
. Absence of type II collagen production
. Defect in the enzymatic cross-linking of type I collagen
. Mutation in the fibrillin-1 gene

Correct Answer & Explanation

. Quantitative defect (decreased amount) of normal type I collagen

Explanation

Osteogenesis Imperfecta Type I is the mildest and most common form, caused by a quantitative defect resulting in decreased production of structurally normal type I collagen. Type II, III, and IV OI generally involve qualitative defects (structural abnormalities) in the collagen molecule.

Question 5657

Topic: 4. Pediatrics

A 25-year-old athlete undergoes a meniscal repair. The primary structural collagen type providing tensile strength in the normal healthy meniscus is also the predominant collagen found in which of the following tissues?

. Articular cartilage
. Tendon
. Nucleus pulposus
. Hypertrophic zone of physis
. Basement membrane

Correct Answer & Explanation

. Tendon

Explanation

The normal meniscus is primarily composed of Type I collagen, which provides tensile strength. Tendons, ligaments, and bone are also predominantly Type I collagen, whereas articular cartilage contains mainly Type II.

Question 5658

Topic: 4. Pediatrics

In a pediatric patient presenting with a slipped capital femoral epiphysis (SCFE), the mechanical failure primarily occurs through which histological zone of the growth plate?

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

Correct Answer & Explanation

. Hypertrophic zone

Explanation

Slipped capital femoral epiphysis (SCFE) and most Salter-Harris fractures classically occur through the hypertrophic zone of the physis. This zone lacks the structural support of collagen and calcified matrix, making it the weakest point under shear stress.

Question 5659

Topic: 4. Pediatrics

A neonate is evaluated for rhizomelic dwarfism, frontal bossing, and midface hypoplasia. Radiographs show narrowing of the interpedicular distances in the lumbar spine. This condition is caused by a gain-of-function mutation in the FGFR3 gene, which primarily inhibits which of the following processes?

. Intramembranous ossification
. Proliferation of chondrocytes in the physis
. Osteoclast-mediated bone resorption
. Synthesis of Type I collagen
. Mineralization of osteoid

Correct Answer & Explanation

. Proliferation of chondrocytes in the physis

Explanation

Achondroplasia is caused by an autosomal dominant gain-of-function mutation in the FGFR3 gene. This overactivity effectively inhibits chondrocyte proliferation in the proliferative zone of the physis, severely impairing endochondral ossification.

Question 5660

Topic: Pediatric Hip
A 4-month-old female is diagnosed with Developmental Dysplasia of the Hip (DDH). Ultrasound confirms a dislocated right hip, and treatment with a Pavlik harness is initiated. Which of the following complications is most likely if the hip is maintained in excessive hyperflexion (>120 degrees) in the harness?
. Avascular necrosis of the femoral head
. Femoral nerve palsy
. Obturator nerve palsy
. Sciatic nerve palsy
. Inferior dislocation of the hip

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

In a Pavlik harness, excessive hyperflexion (>120 degrees) is classically associated with femoral nerve palsy due to compression of the nerve against the inguinal ligament. Excessive abduction is associated with avascular necrosis of the femoral head.

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