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4. Pediatrics MCQs

Practice Set 274 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 5461

Topic: Pediatric Hip

A 4-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a follow-up, she exhibits decreased active knee extension on the affected side. What is the most likely cause?

. Avascular necrosis of the femoral head
. Obturator nerve palsy from excessive abduction
. Femoral nerve palsy from excessive hyperflexion
. Sciatic nerve palsy from excessive extension
. Common peroneal nerve compression from the anterior strap

Correct Answer & Explanation

. Femoral nerve palsy from excessive hyperflexion

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by excessive hip hyperflexion that compresses the nerve. It presents as decreased active knee extension.

Question 5462

Topic: Pediatric Hip

An obese 13-year-old boy presents with an inability to bear weight on his right leg after a minor fall. Radiographs confirm an acute, unstable slipped capital femoral epiphysis (SCFE). If the surgeon attempts a forceful, anatomic closed reduction prior to internal fixation, the patient is at highest risk for which of the following complications?

. Chondrolysis
. Coxa magna
. Femoral neck fracture
. Avascular necrosis (AVN)
. Premature physeal closure

Correct Answer & Explanation

. Avascular necrosis (AVN)

Explanation

Forceful or anatomic reduction of an unstable SCFE dramatically increases the risk of avascular necrosis. This occurs due to disruption or tensioning of the fragile posterior retinacular blood supply to the femoral head.

Question 5463

Topic: Pediatric Hip

A 6-week-old female infant undergoes a screening ultrasound of the hip due to a family history of developmental dysplasia of the hip (DDH). The sonographer reports an alpha angle of 50 degrees. According to the Graf classification, what does this alpha angle represent?

. Normal acetabular bony roof
. Dysplastic acetabular bony roof
. Normal cartilaginous roof coverage
. A completely dislocated hip resting outside the labrum
. A mature hip requiring no further follow-up

Correct Answer & Explanation

. Dysplastic acetabular bony roof

Explanation

In the Graf ultrasound evaluation for DDH, the alpha angle measures the concavity of the bony acetabular roof. An alpha angle less than 60 degrees (such as 50 degrees) indicates a dysplastic or shallow bony roof, typically classifying as a Graf Type II hip.

Question 5464

Topic: 4. Pediatrics

A pediatric orthopedic surgeon initiates treatment for a 2-week-old infant with an idiopathic clubfoot (talipes equinovarus) using the Ponseti casting method. Which of the following represents the correct sequential order of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method requires sequential correction of the clubfoot deformities following the CAVE mnemonic: Cavus (corrected first by elevating the first ray), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy).

Question 5465

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents to the emergency department following a fall from monkey bars. Radiographs reveal an extension-type Gartland III supracondylar humerus fracture. After closed reduction and percutaneous pinning, the patient's radial pulse is absent, but the hand is pink, warm, and has a capillary refill time of less than 2 seconds. What is the most appropriate next step in management?
. Observation with close neurovascular monitoring
. Immediate exploration of the brachial artery
. Removal of the pins and extension of the elbow to 20 degrees
. CT angiography of the upper extremity
. Prophylactic forearm fasciotomy

Correct Answer & Explanation

. Observation with close neurovascular monitoring

Explanation

A pulseless, pink, and well-perfused hand following reduction and pinning of a supracondylar humerus fracture should be observed, as collateral circulation is adequate. Arterial exploration is strictly indicated only if the hand is pulseless, pale, and poorly perfused (ischemic) after reduction.

Question 5466

Topic: Pediatric Hip

A 13-year-old obese male presents with a 3-week history of right-sided groin pain and an antalgic gait. Physical examination reveals an obligatory external rotation of the right hip during passive hip flexion. Radiographs confirm a mild, stable slipped capital femoral epiphysis (SCFE). What is the most appropriate definitive management?

. Spica cast immobilization
. Closed reduction and internal fixation
. In situ single screw fixation
. Proximal femoral osteotomy
. Observation with strict non-weight bearing

Correct Answer & Explanation

. In situ single screw fixation

Explanation

The gold standard treatment for a stable slipped capital femoral epiphysis (SCFE) is in situ fixation using a single partially threaded cannulated screw. Attempting a closed reduction is contraindicated as it severely increases the risk of avascular necrosis of the femoral head.

Question 5467

Topic: 4. Pediatrics
A 24-year-old male presents with recurrent fractures and a 'bone-in-bone' appearance on radiographs. His condition is caused by a failure of osteoclasts to resorb bone. Which of the following mutations is most commonly responsible for the autosomal dominant form of this disease?
. TCIRG1
. CLCN7
. COL1A1
. FGFR3
. RUNX2

Correct Answer & Explanation

. CLCN7

Explanation

Autosomal dominant osteopetrosis (Albers-Schönberg disease) is most commonly caused by a mutation in the CLCN7 gene, which encodes a chloride channel necessary for acidifying the resorption pit. TCIRG1 causes the severe autosomal recessive form. COL1A1 causes Osteogenesis Imperfecta. FGFR3 causes achondroplasia. RUNX2 is associated with cleidocranial dysplasia.

Question 5468

Topic: Pediatric Hip

A 12-year-old obese male presents with left groin pain and an obligatory external rotation of the hip during active flexion. Radiographs show a posterior and inferior displacement of the proximal femoral epiphysis. Which of the following is the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Age greater than 14 years
. Endocrine disorder (e.g., hypothyroidism)
. Moderate displacement (Southwick angle 30-50 degrees)
. BMI > 35
. Presentation with acute on chronic symptoms

Correct Answer & Explanation

. Endocrine disorder (e.g., hypothyroidism)

Explanation

Prophylactic pinning of the contralateral hip in Slipped Capital Femoral Epiphysis (SCFE) is highly recommended in patients with endocrine disorders (such as hypothyroidism, renal osteodystrophy, or growth hormone deficiency) and in children presenting at a very young age (< 10 years), due to the high risk of bilateral involvement.

Question 5469

Topic: 4. Pediatrics

A 4-year-old child presents with rhizomelic short stature, frontal bossing, and midface hypoplasia. Radiographs show narrowing of the interpedicular distances in the lumbar spine and 'champagne glass' pelvis. The genetic mutation responsible for this condition causes an abnormality in which zone of the physis?

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

Correct Answer & Explanation

. Proliferative zone

Explanation

Achondroplasia is caused by an activating mutation in the FGFR3 gene, which inhibits chondrocyte proliferation. This directly affects the proliferative zone of the physis, leading to defective endochondral ossification.

Question 5470

Topic: Pediatric Hip

A 13-year-old obese male presents with a stable slipped capital femoral epiphysis (SCFE) of the left hip. Prophylactic pinning of the contralateral, asymptomatic hip is most strongly recommended for patients with which of the following underlying conditions?

. Obesity greater than the 99th percentile
. Type 2 diabetes mellitus
. Endocrine disorders (e.g., hypothyroidism or panhypopituitarism)
. Previous history of significant hip trauma
. Nutritional Vitamin D deficiency

Correct Answer & Explanation

. Endocrine disorders (e.g., hypothyroidism or panhypopituitarism)

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial for typical patients but is highly recommended in patients with an underlying endocrinopathy (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency), as their risk for a contralateral slip approaches 50-100%.

Question 5471

Topic: Pediatric Lower Extremity

The Ponseti method is the gold standard for the conservative management of idiopathic clubfoot (talipes equinovarus). What is the correct sequence of deformity correction during serial casting?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method requires sequential correction of the clubfoot deformities using the mnemonic CAVE: first Cavus (by elevating the first ray to supinate the forefoot), then Adductus, then Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy).

Question 5472

Topic: Pediatric Hip

A 3-month-old infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). At follow-up, the parents report the infant is not kicking the affected leg. Physical exam reveals absent active knee extension, but active ankle dorsiflexion is intact. Which complication of the harness has most likely occurred?

. Obturator nerve palsy
. Sciatic nerve palsy
. Femoral nerve palsy
. Avascular necrosis of the femoral head
. Superior gluteal nerve palsy

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Hyperflexion of the hips in a Pavlik harness can compress the femoral nerve against the rim of the pelvis or inguinal ligament, leading to a femoral nerve palsy. This manifests clinically as an inability to actively extend the knee. The treatment is temporary discontinuation or adjustment of the harness.

Question 5473

Topic: Pediatric Hip

A 4-week-old female infant is diagnosed with developmental dysplasia of the hip (DDH) and placed in a Pavlik harness. While monitoring the patient, what is the most common neurological complication resulting from excessive hip flexion in this device?

. Sciatic nerve palsy
. Femoral nerve palsy
. Obturator nerve palsy
. Superior gluteal nerve palsy
. Pudendal nerve palsy

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Excessive hip flexion in a Pavlik harness can cause impingement leading to a femoral nerve palsy. This typically presents as a loss of active knee extension. Conversely, excessive abduction in the harness places the patient at high risk for avascular necrosis (AVN) of the femoral head.

Question 5474

Topic: Pediatric Hip

A 12-year-old overweight boy presents with left knee pain and a limp. Examination reveals obligate external rotation of the left hip during passive hip flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Which of the following is the typical direction of the epiphyseal displacement relative to the femoral neck?

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

Correct Answer & Explanation

. Posterior and inferior

Explanation

In a slipped capital femoral epiphysis (SCFE), the femoral epiphysis typically displaces posteriorly and inferiorly relative to the femoral neck. Conversely, the metaphysis (femoral neck) translates anteriorly and superiorly.

Question 5475

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents with a 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?
. Immediate vascular exploration
. Observation and hospital admission
. Perform an intra-operative angiogram
. Remove the pins and open the fracture
. Administer intra-arterial vasodilators

Correct Answer & Explanation

. Observation and hospital admission

Explanation

A "pink, pulseless" hand after successful reduction and pinning of a supracondylar fracture usually signifies adequate collateral circulation. Observation is indicated, as the palpable radial pulse often returns within 24-48 hours.

Question 5476

Topic: Pediatric Hip

A 6-week-old female is treated with a Pavlik harness for developmental dysplasia of the hip. At the one-week follow-up, she exhibits decreased active knee extension on the treated side. What is the most likely cause?

. Hyperflexion of the hip in the harness
. Excessive abduction of the hip in the harness
. Avascular necrosis of the femoral head
. Transient synovitis
. Improperly sized chest strap

Correct Answer & Explanation

. Hyperflexion of the hip in the harness

Explanation

Hyperflexion of the hip in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy. This manifests clinically as decreased active knee extension.

Question 5477

Topic: Pediatric Hip

A 14-year-old boy is diagnosed with an unstable slipped capital femoral epiphysis (SCFE). Which of the following describes the most critical consequence differentiating an unstable SCFE from a stable SCFE?

. Higher risk of chondrolysis
. Inability to ambulate with or without crutches
. Higher risk of avascular necrosis (AVN)
. Requirement for an open reduction
. Increased incidence of contralateral slip

Correct Answer & Explanation

. Higher risk of avascular necrosis (AVN)

Explanation

The Loder classification distinguishes stable from unstable SCFE based on the ability to bear weight. Unstable slips carry a drastically higher risk of avascular necrosis (up to 50%), dictating urgency and care in surgical management.

Question 5478

Topic: Pediatric Hip

A 3-month-old infant is currently being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the routine weekly follow-up, the infant is noted to have an absence of active knee extension on the treated side. What is the most likely cause of this physical finding?

. Obturator nerve palsy from excessive abduction
. Sciatic nerve palsy from excessive extension
. Femoral nerve palsy from excessive flexion
. Avascular necrosis of the femoral head
. Inferior dislocation of the hip

Correct Answer & Explanation

. Femoral nerve palsy from excessive flexion

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment, usually caused by excessive hip flexion (typically >120 degrees). It presents as decreased or absent active knee extension. The harness must be adjusted to reduce flexion or temporarily discontinued if the palsy persists. Excessive abduction in a Pavlik harness is associated with an increased risk of avascular necrosis (AVN) of the femoral head.

Question 5479

Topic: Pediatric Hip

Which of the following clinical scenarios serves as the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip in a patient who presents with a unilateral slipped capital femoral epiphysis (SCFE)?

. Patient age of 14 years at initial presentation
. Male gender
. Obesity (BMI > 95th percentile for age)
. Presence of an endocrine disorder such as hypothyroidism
. A Southwick angle greater than 50 degrees on the symptomatic side

Correct Answer & Explanation

. Presence of an endocrine disorder such as hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in unilateral SCFE is highly recommended in patients with specific risk factors that predispose them to bilateral involvement. The strongest indications include an underlying endocrine disorder (e.g., hypothyroidism, panhypopituitarism, renal osteodystrophy), previous pelvic radiation, and very young age at presentation (typically < 10 years for boys and < 9 for girls). Endocrine disorders carry an extremely high risk of bilateral SCFE, justifying prophylactic fixation.

Question 5480

Topic: Pediatric Hip

Prophylactic in situ pinning of the asymptomatic contralateral hip in a patient with a slipped capital femoral epiphysis (SCFE) is most strongly indicated in a patient with which of the following underlying conditions?

. Obesity (> 95th percentile BMI)
. Trisomy 21
. Renal osteodystrophy
. Marfan syndrome
. Sickle cell trait

Correct Answer & Explanation

. Renal osteodystrophy

Explanation

Prophylactic pinning of the contralateral hip in SCFE is indicated for patients with a high risk of subsequent bilateral slip. Endocrine and metabolic disorders, such as renal osteodystrophy, hypothyroidism, and prior pelvic radiation, are strong indications for prophylactic fixation due to the high incidence of bilaterality.

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