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4. Pediatrics MCQs

Practice Set 288 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 5741

Topic: Pediatric Hip
A 6-year-old boy is diagnosed with Legg-Calvé-Perthes disease. His orthopedic surgeon explains that his prognosis depends heavily on the extent of epiphyseal involvement. According to the lateral pillar (Herring) classification, which radiographic finding during the fragmentation stage is associated with the worst prognosis?
. >50% maintenance of lateral pillar height.
. <50% maintenance of lateral pillar height.
. Subchondral radiolucency (crescent sign).
. Calcification lateral to the epiphysis.
. Metaphyseal cysts.

Correct Answer & Explanation

. <50% maintenance of lateral pillar height.

Explanation

The Herring lateral pillar classification is utilized during the fragmentation stage of Legg-Calvé-Perthes disease to determine prognosis based on the height of the lateral portion of the capital femoral epiphysis. Group A has no lateral pillar involvement. Group B has >50% lateral pillar height maintained. Group C has <50% lateral pillar height maintained and is associated with the worst prognosis, often leading to aspherical congruency or incongruency of the hip joint and early-onset osteoarthritis.

Question 5742

Topic: 4. Pediatrics

A 4-year-old boy presents with a 3-day history of fever, irritability, and refusal to bear weight on his right leg. Laboratory studies show an elevated CRP and ESR. MRI reveals marrow edema in the distal femoral metaphysis with a small subperiosteal abscess. What anatomical feature of the pediatric long bone makes the metaphysis the most common site for acute hematogenous osteomyelitis?

. The presence of a highly vascularized secondary ossification center.
. Sluggish blood flow in the venous sinusoids adjacent to the physis.
. Direct communication between the metaphyseal and epiphyseal blood vessels.
. A lack of periosteal covering over the metaphyseal bone.
. High concentration of hematopoietic stem cells in the metaphyseal marrow.

Correct Answer & Explanation

. Sluggish blood flow in the venous sinusoids adjacent to the physis.

Explanation

Correct Answer: BIn children, acute hematogenous osteomyelitis most commonly affects the metaphysis of long bones. The terminal branches of the nutrient artery loop near the physis and empty into large, dilated venous sinusoids. The sluggish, turbulent blood flow in these sinusoids creates an ideal environment for bacterial deposition and proliferation. Furthermore, there is a relative lack of active phagocytic cells in this specific region, further contributing to the susceptibility to infection.

Question 5743

Topic: Pediatric Hip

A 13-year-old obese male presents with acute-on-chronic left hip pain. He is unable to bear weight on the affected limb, even with the assistance of crutches. Radiographs confirm a slipped capital femoral epiphysis (SCFE). According to the Loder classification, what is the most significant prognostic implication of his inability to bear weight?

. Increased risk of chondrolysis
. Increased risk of avascular necrosis (AVN)
. Increased risk of contralateral slip
. Decreased likelihood of requiring surgical pinning
. Increased risk of premature physeal closure

Correct Answer & Explanation

. Increased risk of avascular necrosis (AVN)

Explanation

Correct Answer: Increased risk of avascular necrosis (AVN)The Loder classification categorizes slipped capital femoral epiphysis (SCFE) into stable and unstable based on the patient's ability to bear weight. An unstable SCFE is defined by the inability to ambulate with or without crutches. This distinction is critical because it carries significant prognostic value regarding the development of avascular necrosis (AVN). Unstable SCFE has a high rate of AVN, historically reported between 24% and 47%, due to the acute disruption of the retinacular vessels supplying the femoral head. Stable SCFE, where the patient can bear weight, has an AVN rate of nearly 0%.

Question 5744

Topic: Pediatric Lower Extremity

A 12-year-old male basketball player presents with anterior knee pain that worsens with jumping and running. Physical examination reveals point tenderness localized strictly to the inferior pole of the patella, with no tenderness at the tibial tubercle. Radiographs demonstrate fragmentation and sclerosis at the inferior patellar pole. What is the most likely diagnosis?

. Osgood-Schlatter disease
. Sinding-Larsen-Johansson syndrome
. Patellar sleeve fracture
. Bipartite patella
. Prepatellar bursitis

Correct Answer & Explanation

. Sinding-Larsen-Johansson syndrome

Explanation

Correct Answer: Sinding-Larsen-Johansson syndromeSinding-Larsen-Johansson (SLJ) syndrome is an osteochondrosis or traction apophysitis occurring at the inferior pole of the patella, where the proximal patellar tendon originates. It is common in active adolescents aged 10-14 years and presents with activity-related anterior knee pain and localized tenderness at the inferior patellar pole. Radiographs often show fragmentation or calcification at this site. It is clinically distinct from Osgood-Schlatter disease, which is a similar traction apophysitis but occurs distally at the insertion of the patellar tendon on the tibial tubercle.

Question 5745

Topic: 4. Pediatrics

A 13-year-old obese male presents with a 3-week history of left knee pain and a limp. On physical examination, as the left hip is passively flexed, it obligatorily rotates externally. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Which of the following best describes the biomechanical failure and anatomical zone involved in this condition?

. Failure through the zone of provisional calcification of the physis due to shear stress
. Failure through the hypertrophic zone of the physis due to shear stress
. Failure through the resting zone of the physis due to compressive stress
. Failure through the proliferative zone of the physis due to tensile stress
. Failure through the primary spongiosa due to torsional stress

Correct Answer & Explanation

. Failure through the hypertrophic zone of the physis due to shear stress

Explanation

Correct Answer: B (Failure through the hypertrophic zone of the physis due to shear stress)Slipped capital femoral epiphysis (SCFE) is characterized by the displacement of the proximal femoral epiphysis relative to the metaphysis. Biomechanically, this occurs due to excessive shear stress across the physis, often exacerbated by obesity and the relatively vertical orientation of the physis during the adolescent growth spurt. Histologically, the mechanical failure occurs specifically through the hypertrophic zone of the physis. This zone lacks the structural integrity of the adjacent zones because the chondrocytes are enlarged and the extracellular matrix is relatively sparse, making it the weakest link under shear loading.

Question 5746

Topic: 4. Pediatrics
A 5-year-old boy falls from monkey bars and presents with a grossly deformed elbow. The hand is pale and pulseless, but capillary refill is 2 seconds. Radiographs show a Gartland type III extension-type supracondylar humerus fracture. The patient is taken emergently to the operating room. After closed reduction and percutaneous pinning, the hand remains pink and warm with brisk capillary refill, but the radial pulse is still not palpable. What is the most appropriate next step in management?
. Immediate exploration of the brachial artery
. Removal of pins and open reduction
. Observation and admission for close neurovascular monitoring
. Intra-operative angiogram
. Fasciotomy of the forearm

Correct Answer & Explanation

. Observation and admission for close neurovascular monitoring

Explanation

The management of a "pink, pulseless" hand following the reduction of a pediatric supracondylar humerus fracture is a classic board scenario. The initial absence of a pulse is often due to kinking, spasm, or tethering of the brachial artery over the proximal fracture fragment. If, after anatomical reduction and stabilization, the hand becomes well-perfused (pink, warm, capillary refill < 2 seconds) but the pulse remains impalpable, the standard of care is close observation. The collateral circulation around the pediatric elbow is robust enough to maintain viability. Immediate vascular exploration is indicated only for a "white, pulseless" hand that does not improve after reduction.

Question 5747

Topic: Pediatric Hip

A 9-month-old female is diagnosed with late-presenting developmental dysplasia of the hip (DDH). Radiographs confirm a laterally subluxated and superiorly migrated left femoral head with a dysplastic acetabulum. Which of the following is the most appropriate initial management?

. Pavlik harness application
. Closed reduction and spica casting
. Open reduction and femoral shortening osteotomy
. Pemberton pelvic osteotomy
. Observation until 1 year of age

Correct Answer & Explanation

. Closed reduction and spica casting

Explanation

For DDH presenting between 6 and 18 months of age, closed reduction and application of a hip spica cast is the initial treatment of choice. The Pavlik harness is typically reserved for reducible hips in infants younger than 6 months.

Question 5748

Topic: Pediatric Hip

A 6-week-old female is being treated with a Pavlik harness for developmental dysplasia of the hip. At her 2-week follow-up, the parents report she has stopped kicking her left leg. On exam, she lacks active knee extension on the left side but has normal sensation. What is the most likely cause of this clinical presentation?

. Hyperflexion of the hip in the harness
. Excessive abduction of the hip in the harness
. Excessive adduction of the hip in the harness
. Hyperextension of the knee due to strap malposition
. Inadequate flexion of the hip in the harness

Correct Answer & Explanation

. Hyperflexion of the hip in the harness

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment caused by hyperflexion of the hip. Excessive abduction, conversely, increases the risk of avascular necrosis of the femoral head.

Question 5749

Topic: Pediatric Hip

An 8-week-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up visit, the parents note the infant has stopped kicking her left leg. On examination, there is an absence of active knee extension on the left side, but ankle and toe movements are normal. The hip is positioned in 120 degrees of flexion. Which of the following is the most appropriate next step in management?

. Immediate closed reduction and spica casting
. Obtain an emergent MRI of the lumbar spine
. Decrease the degree of hip flexion in the harness
. Decrease the degree of hip abduction in the harness
. Switch to a rigid abduction orthosis

Correct Answer & Explanation

. Decrease the degree of hip flexion in the harness

Explanation

The clinical presentation is consistent with a femoral nerve palsy, the most common neurologic complication of a Pavlik harness, caused by hyperflexion of the hip. The appropriate management is to decrease the degree of hip flexion or temporarily remove the harness until nerve function returns.

Question 5750

Topic: 4. Pediatrics

The fundamental pathophysiology of achondroplasia involves a gain-of-function mutation in the FGFR3 gene. What is the specific effect of this mutation on the physeal growth plate?

. Excessive chondrocyte hypertrophy in the hypertrophic zone
. Inhibition of chondrocyte proliferation in the proliferative zone
. Defective mineralization of the primary spongiosa
. Increased osteoclast activity at the metaphysis
. Abnormal synthesis of Type II collagen in the resting zone

Correct Answer & Explanation

. Inhibition of chondrocyte proliferation in the proliferative zone

Explanation

The mutated FGFR3 receptor in achondroplasia is constitutively active, which paradoxically inhibits chondrocyte proliferation. This primarily affects the proliferative zone of the physis, leading to defective endochondral ossification and short-limbed dwarfism.

Question 5751

Topic: Pediatric Upper Extremity & Spine

A 14-year-old girl with adolescent idiopathic scoliosis has a progressive right thoracic curve that now measures 52 degrees. Her Risser stage is 4, and she has had menarche 2 years ago. What is the most appropriate management?

. Observation with radiographs every 6 months
. Full-time thoracolumbosacral orthosis (TLSO)
. Nighttime bending brace
. Posterior spinal fusion
. Anterior vertebral body tethering

Correct Answer & Explanation

. Posterior spinal fusion

Explanation

For adolescents with idiopathic scoliosis, a curve exceeding 50 degrees is highly likely to progress even after skeletal maturity. Posterior spinal fusion is the gold standard treatment for a 52-degree curve in a near-skeletally mature patient.

Question 5752

Topic: 4. Pediatrics

A 4-year-old child presents with frequent long bone fractures after minimal trauma, blue sclerae, and dentinogenesis imperfecta. Genetic testing confirms Osteogenesis Imperfecta. Which of the following describes the underlying molecular defect?

. Qualitative or quantitative defect in Type I collagen
. Qualitative defect in Type II collagen
. Mutation in the COMP gene
. Defect in Type X collagen synthesis
. Gain-of-function mutation in FGFR3

Correct Answer & Explanation

. Qualitative or quantitative defect in Type I collagen

Explanation

Osteogenesis Imperfecta is primarily caused by mutations in the COL1A1 or COL1A2 genes, leading to qualitative or quantitative defects in Type I collagen. Type I collagen is the major structural protein in bone, sclera, and dentin.

Question 5753

Topic: 4. Pediatrics

A newborn is evaluated for skeletal dysplasia. Physical examination reveals short-limbed dwarfism, bilateral rigid clubfeet, "hitchhiker" thumbs, and cystic swelling of the external ears (cauliflower ears). Which gene is most likely mutated in this patient?

. FGFR3
. COMP
. SLC26A2
. COL1A1
. RUNX2

Correct Answer & Explanation

. SLC26A2

Explanation

The clinical picture describes diastrophic dysplasia, which is inherited in an autosomal recessive manner. It is caused by a mutation in the SLC26A2 gene (also known as DTDST), which impairs sulfate transport leading to undersulfated proteoglycans in cartilage.

Question 5754

Topic: Pediatric Upper Extremity & Spine

In the Lenke classification system for adolescent idiopathic scoliosis, a lumbar modifier of "C" indicates the relationship between the center sacral vertical line (CSVL) and the apical lumbar vertebra. Which of the following defines a "C" modifier?

. The CSVL passes between the pedicles of the apical lumbar vertebra
. The CSVL touches the medial border of the apical pedicle
. The CSVL does not touch any part of the apical lumbar vertebral body
. The CSVL bisects the apical vertebral body exactly
. The CSVL passes lateral to the convex border of the apical vertebra

Correct Answer & Explanation

. The CSVL does not touch any part of the apical lumbar vertebral body

Explanation

In the Lenke classification, a lumbar C modifier means the center sacral vertical line (CSVL) falls completely outside the apical lumbar vertebra (i.e., it does not touch any part of the vertebral body). This implies a significant structural lumbar curve.

Question 5755

Topic: Pediatric Upper Extremity & Spine

In the Lenke classification for adolescent idiopathic scoliosis, a curve characterized by a structural proximal thoracic curve, a structural main thoracic curve, and a non-structural thoracolumbar/lumbar curve is classified as which type?

. Type 1
. Type 2
. Type 3
. Type 4
. Type 5

Correct Answer & Explanation

. Type 2

Explanation

Lenke Type 2 is a 'Double Thoracic' curve. This means both the proximal thoracic and main thoracic curves are structural, while the thoracolumbar/lumbar curve remains non-structural.

Question 5756

Topic: 4. Pediatrics

What is the underlying genetic mutation and its functional effect in a patient presenting with achondroplasia?

. FGFR3 activating mutation
. FGFR3 inactivating mutation
. COL1A1 activating mutation
. COMP gene mutation
. CBFA1 (RUNX2) deletion

Correct Answer & Explanation

. FGFR3 activating mutation

Explanation

Achondroplasia is caused by an activating (gain-of-function) mutation in the FGFR3 gene. This leads to constitutive inhibition of chondrocyte proliferation in the proliferative zone of the physis, resulting in rhizomelic dwarfism.

Question 5757

Topic: 4. Pediatrics

A 2-year-old child presents with congenital scoliosis due to a fully segmented hemivertebra at T8. The curve has progressed 15 degrees over the last 6 months. What is the most appropriate surgical treatment?

. Observation until age 5
. Hemivertebra excision and short segment fusion
. Growing rod construct
. VEPTR insertion
. Bracing with a custom TLSO

Correct Answer & Explanation

. Hemivertebra excision and short segment fusion

Explanation

A fully segmented hemivertebra has high growth potential on one side and typically causes rapid, unrelenting curve progression. Early hemivertebra excision with short-segment fusion is the treatment of choice to halt progression and minimize the number of fused vertebral segments.

Question 5758

Topic: 4. Pediatrics
Which type of Osteogenesis Imperfecta is characterized by profound bone fragility, multiple in utero fractures, and is typically lethal in the perinatal period?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

Osteogenesis Imperfecta Type II is the most severe and lethal form of the disease. Infants typically die in the perinatal period due to severe pulmonary hypoplasia and massive trauma from multiple fractures.

Question 5759

Topic: 4. Pediatrics

A 7-year-old child presents with a waddling gait, knee pain, and short stature. Radiographs show delayed, irregular ossification of multiple epiphyses, but the spine is radiographically normal. Which gene mutation is most commonly associated with the autosomal dominant form of this condition?

. FGFR3
. COMP
. COL1A1
. COL2A1
. CBFA1 (RUNX2)

Correct Answer & Explanation

. COMP

Explanation

Multiple Epiphyseal Dysplasia (MED) affects the epiphyses with a normal spine, distinguishing it from spondyloepiphyseal dysplasia. Mutations in the Cartilage Oligomeric Matrix Protein (COMP) gene are the most common cause of autosomal dominant MED.

Question 5760

Topic: Pediatric Upper Extremity & Spine

A 13-year-old girl with adolescent idiopathic scoliosis has a 35-degree right thoracic curve. Pelvic radiographs show ossification over the lateral 50% of the iliac apophysis, with no fusion to the ilium. What is her Risser stage?

. Risser 1
. Risser 2
. Risser 3
. Risser 4
. Risser 5

Correct Answer & Explanation

. Risser 2

Explanation

Risser 2 indicates ossification of the lateral 25% to 50% of the iliac apophysis without fusion. This implies significant spinal growth still remains, placing her at high risk for curve progression and making her an ideal candidate for bracing.

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