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4. Pediatrics MCQs

Practice Set 241 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 4801

Topic: Pediatric Hip

A 13-year-old boy who underwent in-situ pinning for a stable, severe slipped capital femoral epiphysis (SCFE) 6 months ago now presents with severe hip stiffness and a painful limp. Radiographs demonstrate a concentric loss of joint space in the affected hip of greater than 50% accompanied by periarticular osteopenia. What is the most likely diagnosis?

. Avascular necrosis (AVN) of the femoral head
. Chondrolysis
. Septic arthritis
. Hardware penetration into the joint
. Cam-type femoroacetabular impingement

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

Chondrolysis is a severe complication of SCFE, characterized clinically by progressive stiffness and pain, and radiographically by a concentric loss of joint space (greater than 50% compared to the contralateral side) and regional osteopenia. Risk factors include severe slips, unrecognised pin penetration, and spica cast immobilization. AVN typically presents with subchondral collapse and sclerosis rather than concentric joint space narrowing.

Question 4802

Topic: Pediatric Hip

An infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the 2-week follow-up, the mother notices that the infant is no longer kicking her right leg, and the quadriceps muscle appears flaccid. Which of the following harness positioning errors is the most likely cause of this complication?

. Excessive abduction of the hips
. Insufficient abduction of the hips
. Excessive flexion of the hips
. Insufficient flexion of the hips
. Excessive extension of the hips

Correct Answer & Explanation

. Excessive abduction of the hips

Explanation

A femoral nerve palsy in an infant treated with a Pavlik harness is typically caused by excessive flexion of the hips (hyperflexion), which compresses the femoral nerve against the inguinal ligament. Excessive abduction is associated with a different severe complication: avascular necrosis (AVN) of the femoral head.

Question 4803

Topic: Pediatric Hip

An infant is undergoing treatment for developmental dysplasia of the hip (DDH) with a Pavlik harness. During follow-up, the physician notices that the hips have been placed in approximately 130 degrees of flexion. Which of the following complications is most likely to result directly from this specific positioning error?

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

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

In a Pavlik harness, extreme or excessive hyperflexion (greater than 120 degrees) risks compressing the femoral nerve against the edge of the inguinal ligament, leading to transient femoral nerve palsy (manifesting as decreased active knee extension). Conversely, excessive abduction (not flexion) is the primary risk factor for avascular necrosis of the femoral head. Note: Inferior dislocation can also occur with extreme flexion, but femoral nerve palsy is a highly tested direct neurological consequence of hyperflexion.

Question 4804

Topic: Pediatric Upper Extremity & Spine
A 6-year-old girl falls from monkey bars and sustains a Gartland Type III extension-type supracondylar humerus fracture. On arrival, her hand is pink and warm, but she lacks a palpable radial pulse. Capillary refill is brisk (<2 seconds). Which of the following is the most appropriate initial management for this patient?
. Urgent closed reduction and percutaneous pinning, followed by reassessment of the pulse
. Immediate vascular surgical consultation for arterial exploration
. CT angiogram of the upper extremity
. Immediate open reduction through an anterior approach
. Observation in a splint overnight to allow swelling to decrease

Correct Answer & Explanation

. Urgent closed reduction and percutaneous pinning, followed by reassessment of the pulse

Explanation

A 'pink, pulseless' hand is a classic clinical scenario in pediatric supracondylar humerus fractures, commonly due to kinking, spasm, or tethering of the brachial artery. The accepted initial management is urgent closed reduction and percutaneous pinning. Often, the pulse returns once the fracture is reduced. If the hand remains well-perfused (pink) despite no palpable pulse after reduction, observation is acceptable. Immediate exploration is reserved for a 'white, pulseless' hand that does not improve after reduction.

Question 4805

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents with a completely displaced, extension-type (Gartland III) supracondylar humerus fracture. His hand is pink but pulseless. After prompt closed reduction and percutaneous pinning in the OR, his hand remains pink and pulseless. What is the most appropriate next step in management?
. Immediate vascular exploration
. CT angiography of the upper extremity
. Remove the pins, re-reduce, and repin
. Close observation with continuous pulse oximetry and serial exams
. Prophylactic forearm fasciotomy

Correct Answer & Explanation

. Close observation with continuous pulse oximetry and serial exams

Explanation

A 'pink, pulseless' hand after adequate reduction and pinning of a pediatric supracondylar humerus fracture indicates adequate collateral perfusion. The standard of care is close clinical observation, as the radial pulse typically returns within a few days.

Question 4806

Topic: 4. Pediatrics

A 6-year-old boy falls off the monkey bars and sustains a widely displaced, extension-type supracondylar humerus fracture.

On examination, the hand is pink and capillary refill is normal, but the radial pulse is absent. What is the most appropriate next step in management?

. Immediate preoperative arteriogram
. Observation and arm elevation in the emergency department
. Urgent closed reduction and percutaneous pinning
. Immediate open vascular exploration by a vascular surgeon
. Continuous compartment pressure monitoring

Correct Answer & Explanation

. Immediate preoperative arteriogram

Explanation

A 'pulseless, pink' hand in the setting of a displaced pediatric supracondylar humerus fracture indicates that collateral circulation is adequate despite kinking or spasm of the brachial artery. The most appropriate immediate step is urgent closed reduction and percutaneous pinning. The pulse typically returns once the fracture is anatomically reduced and the artery is unkinked.

Question 4807

Topic: 4. Pediatrics

A 14-month-old non-ambulatory child is brought to the emergency department crying with a swollen right thigh. Radiographs demonstrate a displaced spiral fracture of the femoral shaft. The parents state the child caught his leg in the crib slats. What is the most appropriate next step in management?

. Immediate intramedullary nailing of the femur
. Application of a pavlik harness and discharge home
. Consult child protection services and obtain a skeletal survey
. Provide assurance and cast the leg in a single-leg spica
. Obtain a DEXA scan to evaluate for osteogenesis imperfecta

Correct Answer & Explanation

. Immediate intramedullary nailing of the femur

Explanation

Femoral shaft fractures (particularly spiral patterns) in non-ambulatory children are highly suspicious for non-accidental trauma (NAT) due to the torsional force required. Mandatory steps include admitting the child, consulting child protection services, and obtaining a full skeletal survey.

Question 4808

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy falls off monkey bars and sustains a widely displaced extension-type supracondylar humerus fracture (Gartland Type III). During neurological examination, he is unable to actively flex his thumb interphalangeal joint and the distal interphalangeal joint of his index finger. Which nerve is most likely injured?
. Radial nerve
. Ulnar nerve
. Anterior Interosseous Nerve (AIN)
. Posterior Interosseous Nerve (PIN)
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior Interosseous Nerve (AIN)

Explanation

The Anterior Interosseous Nerve (AIN), a purely motor branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures (often tented over the proximal fragment). Clinically, it presents with an inability to make the 'A-OK' sign due to weakness of the flexor pollicis longus (thumb IP flexion) and the flexor digitorum profundus to the index finger (index DIP flexion).

Question 4809

Topic: Pediatric Upper Extremity & Spine
A 12-year-old premenarchal female is evaluated for a right thoracic prominence. Standing radiographs reveal a main thoracic curve of 32 degrees. Her Risser stage is 0. Based on the Bracing in Adolescent Idiopathic Scoliosis Trial (BRAIST), which of the following factors has the most significant dose-dependent correlation with the success of bracing in preventing curve progression to surgical thresholds?
. The exact magnitude of the initial curve below 35 degrees
. The patient's Body Mass Index (BMI)
. The hours of daily brace wear
. The specific use of a Milwaukee brace over a TLSO
. The presence of an underlying positive family history

Correct Answer & Explanation

. The hours of daily brace wear

Explanation

The BRAIST trial established high-level evidence that bracing significantly decreases the progression of high-risk curves to the threshold for surgery. The success of bracing is highly correlated with compliance in a dose-dependent manner; greater hours of daily brace wear (especially >12.9 hours) yield significantly higher success rates.

Question 4810

Topic: 4. Pediatrics

A 12-year-old girl with cerebral palsy (GMFCS level V) has a rapidly progressing neuromuscular scoliosis measuring 85 degrees, with severe associated pelvic obliquity. She is non-ambulatory and has difficulty sitting in her wheelchair. Which surgical strategy is most critical for addressing her pelvic obliquity and restoring sitting balance?

. Anterior selective thoracic fusion only
. Posterior spinal fusion ending at L5
. Posterior spinal fusion extended to the pelvis (e.g., iliac/S2AI screws)
. Bilateral growing rod insertion ending at L4
. In situ sublaminar wiring without pedicle screws

Correct Answer & Explanation

. Anterior selective thoracic fusion only

Explanation

In non-ambulatory patients with severe neuromuscular scoliosis and pelvic obliquity (often causing "windswept" hips and seating difficulties), extending the posterior spinal fusion to the pelvis is crucial. Stopping at L5 fails to correct the pelvic obliquity and leaves a lever arm that often leads to hardware failure and recurrent deformity.

Question 4811

Topic: Pediatric Upper Extremity & Spine

A 14-year-old female with Adolescent Idiopathic Scoliosis is being evaluated for surgery.

Radiographs demonstrate a main thoracic curve of 55 degrees and a lumbar curve of 35 degrees. On lateral bending films, the main thoracic curve corrects to 30 degrees, while the lumbar curve corrects to 15 degrees. According to the Lenke classification, what type of curve is this?

. Lenke 1 (Main Thoracic)
. Lenke 2 (Double Thoracic)
. Lenke 3 (Double Major)
. Lenke 5 (Thoracolumbar/Lumbar)
. Lenke 6 (Thoracolumbar/Lumbar - Main Thoracic)

Correct Answer & Explanation

. Lenke 1 (Main Thoracic)

Explanation

In the Lenke classification, structural criteria define the curve type. A curve is non-structural if it bends to less than 25 degrees. Here, the lumbar curve bends to 15 degrees (non-structural), while the main thoracic curve remains > 25 degrees (structural). Thus, this is a Lenke 1 (Main Thoracic) curve.

Question 4812

Topic: 4. Pediatrics

A 3-year-old child is diagnosed with congenital scoliosis. Radiographs demonstrate a unilateral unsegmented bar with a contralateral hemivertebra at the same level. What is the expected natural history of this specific congenital spinal anomaly?

. Minimal progression; can be safely observed until skeletal maturity.
. Moderate progression; bracing is highly effective in halting the curve.
. Rapid and severe progression; early surgical intervention is usually required.
. Spontaneous improvement as the child's spinal column lengthens.
. Progression only occurs during the adolescent growth spurt.

Correct Answer & Explanation

. Minimal progression; can be safely observed until skeletal maturity.

Explanation

The combination of a unilateral unsegmented bar and a contralateral hemivertebra at the same level has the highest risk of rapid and severe curve progression among congenital scoliosis anomalies. Because growth is tethered on one side and accelerated on the other, early surgical intervention (often early fusion or excision) is almost universally required, as bracing is ineffective for congenital rigid curves.

Question 4813

Topic: Pediatric Hip

Which of the following is considered an absolute indication for prophylactic in situ pinning of the contralateral asymptomatic hip in a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE)?

. Age greater than 14 years in males
. Presence of an underlying endocrine disorder
. Grade I slip on the symptomatic side
. BMI greater than the 95th percentile
. Male gender

Correct Answer & Explanation

. Age greater than 14 years in males

Explanation

Prophylactic pinning of the contralateral hip is highly recommended in patients with endocrine disorders (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy) or prior pelvic radiation therapy, as these patients have a much higher risk of bilateral involvement (up to 100% in some endocrine cohorts) compared to idiopathic cases.

Question 4814

Topic: Pediatric Hip

An infant with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. If the anterior straps are adjusted too tightly, placing the hips in extreme hyperflexion, the infant is at highest risk for which complication?

. Avascular necrosis of the femoral head
. Femoral nerve palsy
. Obturator nerve palsy
. Sciatic nerve palsy
. Inferior dislocation of the femoral head

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Hyperflexion of the hips in a Pavlik harness (anterior straps too tight) can compress the femoral nerve against the inguinal ligament, leading to femoral nerve palsy. Excessive abduction (posterior straps too tight) increases the risk of avascular necrosis (AVN) of the femoral head.

Question 4815

Topic: Pediatric Hip

In the management of Slipped Capital Femoral Epiphysis (SCFE), prophylactic in situ fixation of the asymptomatic contralateral hip is widely debated. However, it is most strongly indicated and universally recommended in which of the following clinical scenarios?

. An 11-year-old boy with idiopathic SCFE
. A 10-year-old girl with primary hypothyroidism
. A 14-year-old boy with Down syndrome
. A 13-year-old girl with skeletal maturity (Risser 4)
. A 12-year-old boy with a BMI greater than the 95th percentile

Correct Answer & Explanation

. An 11-year-old boy with idiopathic SCFE

Explanation

Prophylactic pinning of the contralateral hip in SCFE is strongly recommended for patients with an underlying metabolic or endocrine disorder (e.g., hypothyroidism, renal osteodystrophy, growth hormone supplementation) due to the exceedingly high risk (up to 100%) of contralateral slip. Idiopathic obesity alone (Option E) increases risk but prophylactic pinning remains controversial and is evaluated on a case-by-case basis based on bone age and follow-up reliability.

Question 4816

Topic: Pediatric Hip

During ultrasonographic evaluation of an infant for Developmental Dysplasia of the Hip (DDH) using the Graf classification, the alpha angle is measured. This angle represents:

. The angle between the ilium and the osseous roof of the acetabulum
. The angle between the ilium and the cartilaginous roof of the acetabulum
. The angle between the femoral neck and the femoral shaft
. The percentage of femoral head coverage by the acetabulum
. The angle between the labrum and the joint capsule

Correct Answer & Explanation

. The angle between the ilium and the osseous roof of the acetabulum

Explanation

In the Graf ultrasound classification for DDH, the alpha angle represents the osseous roof of the acetabulum. It is formed by the intersection of the baseline (drawn along the ilium) and the osseous roof line. A normal alpha angle is greater than 60 degrees. The beta angle measures the cartilaginous roof of the acetabulum.

Question 4817

Topic: 4. Pediatrics

In the management of spasticity in children with Cerebral Palsy, Botulinum toxin type A injections are commonly utilized. The specific mechanism of action at the neuromuscular junction involves:

. Inhibiting voltage-gated calcium channels at the motor endplate
. Cleaving SNAP-25 to prevent presynaptic vesicle fusion and release of acetylcholine
. Irreversibly blocking postsynaptic nicotinic acetylcholine receptors
. Acting as a GABA agonist in the dorsal horn of the spinal cord
. Decreasing muscle fiber sensitivity to intracellular calcium release

Correct Answer & Explanation

. Inhibiting voltage-gated calcium channels at the motor endplate

Explanation

Botulinum toxin type A produces flaccid paralysis by binding to presynaptic cholinergic nerve terminals. It is internalized and acts as a zinc-endopeptidase that cleaves SNAP-25 (a SNARE protein). This permanently prevents the fusion of synaptic vesicles to the presynaptic membrane, halting the release of acetylcholine into the neuromuscular junction. Function only recovers when new nerve terminals sprout.

Question 4818

Topic: 4. Pediatrics

Achondroplasia is the most common form of short-limb dwarfism. It is caused by an activating mutation in the FGFR3 gene. What is the downstream cellular effect of this specific mutation on bone growth?

. Increased proliferation of chondrocytes in the resting zone
. Failure of osteoclast function leading to excessively dense bone
. Inhibition of chondrocyte proliferation in the growth plate
. Defective synthesis and folding of Type I collagen
. Excessive and rapid mineralization of the primary spongiosa

Correct Answer & Explanation

. Increased proliferation of chondrocytes in the resting zone

Explanation

Achondroplasia results from an autosomal dominant, gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. In the normal physis, FGFR3 signaling acts as a negative regulator of bone growth. The mutation leads to constitutive activation of this receptor, resulting in profound suppression of chondrocyte proliferation and hypertrophy in the proliferative and hypertrophic zones of the growth plate, leading to impaired endochondral ossification.

Question 4819

Topic: Pediatric Hip

A 6-week-old infant is diagnosed with developmental dysplasia of the hip (DDH) and placed in a Pavlik harness. After 3 weeks of strict, monitored harness wear, ultrasound confirms the hip remains entirely dislocated. What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 3 weeks
. Transition to a rigid abduction orthosis (e.g., Ilfeld brace)
. Perform immediate closed reduction and spica casting
. Perform open reduction and capsulorrhaphy
. Discontinue harness and observe until the child is 6 months old

Correct Answer & Explanation

. Continue the Pavlik harness for an additional 3 weeks

Explanation

If a hip remains dislocated after 3 to 4 weeks of proper Pavlik harness treatment, the harness must be discontinued to prevent damage to the posterior acetabular wall (Pavlik harness disease). Transitioning to a rigid abduction orthosis is a recognized next step before attempting closed reduction under anesthesia.

Question 4820

Topic: Pediatric Hip

A 6-month-old infant in a Pavlik harness for developmental dysplasia of the hip (DDH) is noted to have decreased active knee extension. Which of the following harness adjustments or complications is most likely responsible?

. Excessive hip abduction causing obturator nerve palsy
. Excessive hip flexion causing femoral nerve palsy
. Inadequate hip flexion causing sciatic nerve palsy
. Excessive hip adduction causing avascular necrosis
. Tight shoulder straps causing brachial plexopathy

Correct Answer & Explanation

. Excessive hip abduction causing obturator nerve palsy

Explanation

Hyperflexion of the hip in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to transient femoral nerve palsy. This manifests as decreased quadriceps function, requiring temporary adjustment or removal of the harness.

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