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4. Pediatrics MCQs

Practice Set 278 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 5541

Topic: Pediatric Hip

A 13-year-old overweight boy sustains an unstable slipped capital femoral epiphysis (SCFE) and is unable to bear weight. He undergoes urgent in-situ pinning. Which of the following complications is he at the highest risk for compared to a patient with a stable SCFE?

. Chondrolysis
. Avascular necrosis (AVN)
. Nonunion
. Heterotopic ossification
. Implant failure

Correct Answer & Explanation

. Avascular necrosis (AVN)

Explanation

An unstable SCFE (defined clinically as the inability to bear weight even with crutches) is associated with a much higher rate of avascular necrosis (AVN), historically reported up to 20-50%, compared to a stable SCFE where AVN is extremely rare (<1%).

Question 5542

Topic: Pediatric Hip

An infant is diagnosed with developmental dysplasia of the hip (DDH) and placed in a Pavlik harness. If the harness is applied with excessive hip flexion (greater than 120 degrees), which nerve is at greatest risk of palsy?

. Sciatic nerve
. Obturator nerve
. Femoral nerve
. Superior gluteal nerve
. Lateral femoral cutaneous nerve

Correct Answer & Explanation

. Femoral nerve

Explanation

Excessive flexion of the hip (> 120 degrees) in a Pavlik harness can impinge the femoral nerve against the inguinal ligament, leading to a compressive femoral nerve palsy. This manifests as an inability to extend the knee.

Question 5543

Topic: Pediatric Hip

A 9-month-old female is diagnosed with developmental dysplasia of the hip (DDH) after an abnormal physical exam. She has received no prior treatment. Radiographs confirm a dislocated left hip. What is the most appropriate initial management?

. Pavlik harness application
. Rigid abduction orthosis (e.g., Ilfeld brace)
. Closed reduction and spica casting
. Open reduction and spica casting
. Femoral derotational osteotomy

Correct Answer & Explanation

. Closed reduction and spica casting

Explanation

For a child presenting between 6 and 18 months of age with a dislocated hip, the standard initial treatment is an examination under anesthesia (EUA), arthrogram, and attempted closed reduction followed by spica casting. A Pavlik harness is typically reserved for infants under 6 months of age and has a high failure rate if initiated after 6 months. Open reduction is indicated if closed reduction fails to achieve a stable, concentric reduction.

Question 5544

Topic: Pediatric Hip

A 12-year-old male is treated for a slipped capital femoral epiphysis (SCFE). The risk of developing a contralateral SCFE is significantly elevated in patients with which of the following underlying conditions?

. Achondroplasia
. Hypothyroidism
. Type 1 Diabetes Mellitus
. Down syndrome
. Marfan syndrome

Correct Answer & Explanation

. Hypothyroidism

Explanation

Patients with endocrine disorders, particularly hypothyroidism, growth hormone deficiency, and panhypopituitarism, have a high incidence of atypical SCFE and a markedly elevated risk of bilateral involvement (up to 100% in some series of endocrine-related SCFE). Prophylactic pinning of the contralateral hip is strongly considered in patients with an underlying endocrinopathy.

Question 5545

Topic: Pediatric Hip

An overweight 13-year-old boy presents with groin pain and an obligate external rotation of the hip with passive flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). What is the classic direction of displacement of the femoral neck relative to the epiphysis?

. Anterior and superior
. Posterior and inferior
. Posterior and superior
. Anterior and inferior
. Medial and inferior

Correct Answer & Explanation

. Anterior and superior

Explanation

In SCFE, the epiphysis stays within the acetabulum while the femoral neck displaces anteriorly and superiorly. This anatomical shift results in the classic clinical finding of obligate external rotation upon hip flexion.

Question 5546

Topic: Pediatric Hip

A 6-week-old infant is treated with a Pavlik harness for developmental dysplasia of the hip. If the harness places the hip in excessive flexion, which nerve is at the greatest risk of compression neuropathy?

. Sciatic nerve
. Obturator nerve
. Femoral nerve
. Lateral femoral cutaneous nerve
. Superior gluteal nerve

Correct Answer & Explanation

. Femoral nerve

Explanation

Excessive hip flexion in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to a temporary palsy. Excessive abduction is avoided due to the higher risk of avascular necrosis of the femoral head.

Question 5547

Topic: Pediatric Hip

A 13-year-old obese male presents with acute worsening of chronic groin pain and inability to bear weight. Radiographs demonstrate a severe slipped capital femoral epiphysis (SCFE). If an unstable SCFE is aggressively anatomically reduced prior to fixation, the patient is at highest risk for developing which of the following complications?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Femoroacetabular impingement
. Leg length discrepancy
. Septic arthritis

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

Forceful or anatomic closed reduction of an unstable SCFE significantly increases the risk of avascular necrosis (AVN) due to disruption of the vulnerable retinacular blood supply. Gentle, in-situ fixation is generally preferred to minimize this risk.

Question 5548

Topic: Pediatric Hip

An infant with developmental dysplasia of the hip (DDH) is being treated in a Pavlik harness. During a follow-up visit, the infant is noted to have decreased active extension of the knee on the treated side. What is the most likely iatrogenic cause?

. Obturator nerve palsy due to excessive abduction
. Femoral nerve palsy due to excessive hyperflexion
. Sciatic nerve palsy due to excessive extension
. Avascular necrosis of the femoral head
. Normal transient developmental reflex

Correct Answer & Explanation

. Femoral nerve palsy due to excessive hyperflexion

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness if the hip is maintained in excessive hyperflexion. It presents as an inability to actively extend the knee, and the harness should be adjusted or temporarily discontinued.

Question 5549

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents with a displaced Gartland type III supracondylar humerus fracture. The hand is pink but pulseless. After closed reduction and percutaneous pinning, the hand remains pink and pulseless. What is the most appropriate next step in management?
. Immediate vascular exploration
. Observation and admission for close neurovascular monitoring
. Angiography to localize the arterial injury
. Fasciotomy of the forearm
. Removal of pins and open reduction

Correct Answer & Explanation

. Observation and admission for close neurovascular monitoring

Explanation

A pink, pulseless hand after adequate reduction and pinning indicates sufficient collateral circulation. The standard of care is close observation and admission, as the radial pulse often returns within 48 hours without the need for vascular exploration.

Question 5550

Topic: Pediatric Hip

A 13-year-old obese male presents with left hip pain and an obligatory external rotation of the hip during active flexion. Radiographs confirm a severe Slipped Capital Femoral Epiphysis (SCFE). Which of the following is the most significant risk factor for the development of avascular necrosis (AVN) in this patient?

. Severity of the slip angle
. Duration of symptoms prior to presentation
. Instability of the SCFE (inability to bear weight)
. Patient's body mass index (BMI)
. Use of a single screw for fixation

Correct Answer & Explanation

. Instability of the SCFE (inability to bear weight)

Explanation

The stability of the slip is the most critical prognostic factor for developing AVN. Unstable SCFE, defined as the inability to bear weight even with crutches, has a significantly higher rate of AVN compared to stable slips.

Question 5551

Topic: Pediatric Hip

A 3-month-old infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). Hyperflexion of the hips in the harness puts the patient at greatest risk for which of the following complications?

. Avascular necrosis of the femoral head
. Femoral nerve palsy
. Sciatic nerve palsy
. Inferior hip dislocation
. Acetabular dysplasia

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Hyperflexion of the hips in a Pavlik harness (greater than 120 degrees) can compress the femoral nerve against the inguinal ligament, leading to transient femoral nerve palsy. Conversely, excessive abduction places the child at higher risk for avascular necrosis.

Question 5552

Topic: Pediatric Hip
An infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At follow-up, the treating physician notes that the anterior straps are overly tightened, forcing the hips into hyperflexion (>120 degrees). The infant is at greatest risk for developing which of the following complications?
. Avascular necrosis of the femoral head
. Femoral nerve palsy
. Sciatic nerve palsy
. Inferior hip dislocation
. Coxa vara

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

In Pavlik harness treatment, excessive hip flexion (> 120 degrees) can impinge the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy (manifesting as a loss of active knee extension). Conversely, excessive forced abduction places the child at high risk for avascular necrosis of the femoral head.

Question 5553

Topic: Pediatric Hip

On an anteroposterior radiograph of the pelvis, Kleinโ€™s line is drawn to evaluate for a Slipped Capital Femoral Epiphysis (SCFE). In a normal, healthy pediatric hip, how should Kleinโ€™s line interact with the femoral head?

. It should pass completely superior to the femoral head without touching it
. It should intersect the superior (lateral) portion of the femoral epiphysis
. It should pass directly through the fovea capitis
. It should bisect the exact center of the epiphysis
. It should intersect the inferior (medial) portion of the femoral epiphysis

Correct Answer & Explanation

. It should intersect the superior (lateral) portion of the femoral epiphysis

Explanation

Klein's line is drawn along the superior border of the femoral neck on an AP radiograph. In a normal hip, this line must intersect a portion of the superior/lateral aspect of the femoral epiphysis. In a SCFE, the epiphysis slips posteriorly and inferiorly, meaning the line will pass superior to the epiphysis or intersect less of it compared to the contralateral side (Trethowan's sign).

Question 5554

Topic: 4. Pediatrics

A 4-year-old child presents with bowing of the lower extremities and widening of the physes on radiographs. Laboratory evaluation shows low serum calcium, low serum phosphate, and elevated alkaline phosphatase. Which of the following is the most likely diagnosis?

. Achondroplasia
. Hypophosphatasia
. Nutritional rickets
. Osteogenesis imperfecta
. Renal osteodystrophy

Correct Answer & Explanation

. Nutritional rickets

Explanation

Nutritional rickets (Vitamin D deficiency) presents with low or normal calcium, low phosphate, elevated alkaline phosphatase, and elevated PTH. Radiographs classically show widening, cupping, and fraying of the metaphyses due to unmineralized osteoid.

Question 5555

Topic: 4. Pediatrics

Osteogenesis imperfecta is primarily caused by a genetic mutation affecting the production of which specific extracellular matrix component?

. Type I collagen
. Type II collagen
. Type X collagen
. Aggrecan
. Decorin

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta is most commonly caused by mutations in the COL1A1 or COL1A2 genes, resulting in defective synthesis of Type I collagen. Type I collagen is the predominant structural protein in bone, skin, tendons, and sclera.

Question 5556

Topic: Pediatric Lower Extremity

During the Ponseti method for correcting idiopathic clubfoot, the sequential correction of the deformity must strictly follow which of the following orders?

. Cavus, Adductus, Varus, Equinus
. Equinus, Varus, Adductus, Cavus
. Adductus, Varus, Cavus, Equinus
. Varus, Cavus, Adductus, Equinus
. Cavus, Varus, Adductus, Equinus

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method corrects the components of clubfoot in a specific sequence remembered by the acronym CAVE: Cavus, Adductus, Varus, and finally Equinus. The first cast elevates the first ray to correct the cavus by supinating the forefoot to match the hindfoot.

Question 5557

Topic: Pediatric Hip

A 12-year-old boy is diagnosed with a stable Slipped Capital Femoral Epiphysis (SCFE). Prophylactic pinning of the asymptomatic contralateral hip is most strongly indicated in patients presenting with which of the following profiles?

. Male gender and chronological age greater than 14 years
. Underlying endocrinopathy (e.g., hypothyroidism or panhypopituitarism)
. Body mass index consistently in the 85th percentile
. An initial slip angle of less than 30 degrees
. Strong family history of developmental dysplasia of the hip

Correct Answer & Explanation

. Underlying endocrinopathy (e.g., hypothyroidism or panhypopituitarism)

Explanation

Prophylactic pinning of the contralateral asymptomatic hip is widely recommended for SCFE patients with underlying endocrine disorders or a history of radiation therapy. These specific patients possess a significantly elevated risk of developing a subsequent bilateral slip.

Question 5558

Topic: Pediatric Hip

A 12-year-old boy presents with an acute-on-chronic slipped capital femoral epiphysis (SCFE). Which of the following is an absolute indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Patient age less than 10 years
. Male gender with a BMI over 95th percentile
. Underlying endocrine disorder such as hypothyroidism
. Slip angle greater than 50 degrees on the affected side
. Presence of a metaphyseal blanch sign of Steel

Correct Answer & Explanation

. Underlying endocrine disorder such as hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip is strongly recommended in patients with an underlying endocrinopathy (e.g., hypothyroidism, renal osteodystrophy) or prior radiation therapy. These conditions carry a much higher risk of bilateral disease compared to idiopathic SCFE.

Question 5559

Topic: Pediatric Hip

A 6-week-old infant with developmental dysplasia of the hip (DDH) is being treated in a Pavlik harness. During follow-up, the infant shows absent active knee extension on the affected side. What is the most appropriate next step in management?

. Increase the hip flexion of the harness
. Increase the hip abduction of the harness
. Switch immediately to a rigid spica cast
. Loosen the anterior straps to decrease hip flexion
. Perform an immediate ultrasound-guided closed reduction

Correct Answer & Explanation

. Loosen the anterior straps to decrease hip flexion

Explanation

Absent active knee extension indicates a femoral nerve palsy, a known complication of excessive hip flexion in a Pavlik harness. The appropriate initial management is to loosen the anterior straps or temporarily discontinue the harness to relieve pressure on the femoral nerve.

Question 5560

Topic: Pediatric Hip

A 12-year-old obese male presents with a left-sided Slipped Capital Femoral Epiphysis (SCFE). Which of the following factors represents the strongest indication for prophylactic pinning of the contralateral, asymptomatic hip?

. Male gender
. Body Mass Index > 95th percentile
. Underlying endocrine disorder (e.g., hypothyroidism)
. Age of 12 years at presentation
. Initial slip angle > 50 degrees

Correct Answer & Explanation

. Underlying endocrine disorder (e.g., hypothyroidism)

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is strongly indicated in patients with underlying endocrine or metabolic disorders (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency), as well as in patients outside the typical age range (girls <10, boys <11, or older teens), because they have a significantly higher rate of subsequent bilateral involvement.

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