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4. Pediatrics MCQs

Practice Set 104 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 2061

Topic: 4. Pediatrics
A pediatric patient presents with short stature, severe coxa vara, and a waddling gait. Radiographs show delayed epiphyseal ossification and platyspondyly. A mutation in the gene encoding which type of collagen is most likely responsible for this condition?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type X collagen

Correct Answer & Explanation

. Type II collagen

Explanation

The patient exhibits signs of multiple epiphyseal dysplasia or spondyloepiphyseal dysplasia, which are typical Type II collagenopathies. Type II collagen is the primary collagen type in articular cartilage and the nucleus pulposus.

Question 2062

Topic: 4. Pediatrics

A 3-year-old child presents with multiple long bone fractures and blue sclerae. A genetic test reveals a mutation in the COL1A1 gene. Which of the following best describes the fundamental defect at the molecular level in this condition?

. Impaired hydroxylation of proline residues
. Substitution of glycine with a bulkier amino acid in the triple helix
. Deficiency of tissue non-specific alkaline phosphatase
. Defective cross-linking by lysyl oxidase
. Impaired cleavage of procollagen C-terminal propeptides

Correct Answer & Explanation

. Substitution of glycine with a bulkier amino acid in the triple helix

Explanation

Osteogenesis Imperfecta is typically caused by a dominant mutation resulting in the substitution of glycine for a bulkier amino acid in the collagen type I triple helix. This prevents proper folding and assembly of the collagen molecule.

Question 2063

Topic: 4. Pediatrics

A neonate is diagnosed with achondroplasia. The genetic basis of this condition involves a mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. What is the specific pathophysiologic effect of this mutation on bone growth?

. Loss of function causing accelerated chondrocyte proliferation
. Gain of function resulting in constitutive inhibition of chondrocyte proliferation
. Impaired osteoblast differentiation at the primary spongiosa
. Defective formation of the secondary ossification center
. Accelerated osteoclastic resorption of the growth plate

Correct Answer & Explanation

. Gain of function resulting in constitutive inhibition of chondrocyte proliferation

Explanation

Achondroplasia is caused by a gain-of-function mutation in FGFR3. FGFR3 normally acts to inhibit chondrocyte proliferation in the physis; the constitutive activation of this receptor severely restricts endochondral ossification.

Question 2064

Topic: Pediatric Hip

A 6-month-old infant is diagnosed with developmental dysplasia of the hip (DDH) after failing conservative management in a Pavlik harness. The orthopaedic surgeon plans a closed reduction and spica casting. An arthrogram performed intraoperatively shows a medial dye pool of 7 mm. Which of the following structures is LEAST likely to block concentric reduction in this patient?

. Inverted limbus
. Hypertrophied pulvinar
. Ligamentum teres
. Psoas tendon
. Iliacus muscle

Correct Answer & Explanation

. Iliacus muscle

Explanation

Obstacles to concentric reduction in DDH include an inverted limbus, hypertrophied pulvinar, elongated ligamentum teres, constricted transverse acetabular ligament, and a tight psoas tendon. The iliacus muscle is not a recognized mechanical block to reduction in DDH.

Question 2065

Topic: 4. Pediatrics

Which of the following pediatric conditions is the strongest indication for prophylactic pinning of the contralateral, asymptomatic hip in Slipped Capital Femoral Epiphysis (SCFE)?

. Down syndrome
. Hypothyroidism
. Marfan syndrome
. Neurofibromatosis
. Achondroplasia

Correct Answer & Explanation

. Hypothyroidism

Explanation

Endocrine disorders, particularly hypothyroidism and renal osteodystrophy, highly predispose children to bilateral SCFE. Prophylactic pinning of the contralateral side is strongly recommended in these patients.

Question 2066

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy sustains a completely displaced supracondylar humerus fracture. After closed reduction and percutaneous pinning, the hand remains pink with a capillary refill of 1.5 seconds, but the radial pulse is absent. What is the most appropriate next step in management?

. Immediate exploration of the brachial artery
. Perform a brachial angiogram
. Remove the pins and re-reduce the fracture
. Observe and document neurovascular status
. Perform a sympathetic nerve block

Correct Answer & Explanation

. Observe and document neurovascular status

Explanation

In a well-perfused, pink hand with brisk capillary refill but an absent pulse after reduction, collateral circulation is sufficient. Immediate surgical exploration is only indicated if the hand is dysvascular (pale and pulseless).

Question 2067

Topic: Pediatric Hip

When treating developmental dysplasia of the hip (DDH) with a Pavlik harness, excessive hyperflexion (greater than 120 degrees) increases the risk of which complication?

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

Correct Answer & Explanation

. Transient femoral nerve palsy

Explanation

Hyperflexion in a Pavlik harness can compress the femoral nerve against the rim of the pelvis, leading to a transient femoral nerve palsy. Excessive abduction, conversely, increases the risk of avascular necrosis.

Question 2068

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents with a Gartland type III supracondylar humerus fracture. After closed reduction and percutaneous pinning, the hand is pink and well-perfused but the radial pulse is completely absent. What is the most appropriate next step in management?
. Immediate arteriogram
. Immediate vascular exploration
. Remove the pins and extend the elbow
. Local warming of the extremity
. Observation and pulse oximetry monitoring

Correct Answer & Explanation

. Observation and pulse oximetry monitoring

Explanation

A pulseless, pink hand after reduction of a pediatric supracondylar fracture indicates adequate collateral perfusion. Observation is the standard of care, as the pulse typically returns within a few days once swelling subsides.

Question 2069

Topic: Pediatric Hip

A 12-year-old boy presents with a unilateral Slipped Capital Femoral Epiphysis (SCFE). Which of the following is an absolute indication for prophylactic in-situ pinning of the contralateral, asymptomatic hip?

. Age greater than 14 years at presentation
. Body Mass Index greater than the 95th percentile
. Presentation with acute-on-chronic slip
. High primary slip angle (>50 degrees)
. Presence of an underlying endocrine disorder

Correct Answer & Explanation

. Presence of an underlying endocrine disorder

Explanation

Patients with underlying endocrine disorders (such as hypothyroidism or renal osteodystrophy) have a highly elevated risk of bilateral SCFE, often approaching 100%. Prophylactic fixation of the contralateral hip is universally recommended in these specific metabolic cases.

Question 2070

Topic: Pediatric Hip
In Legg-Calvรฉ-Perthes disease, the lateral pillar (Herring) classification is the most reliable predictor of long-term outcome. At what stage of the disease should this classification be applied to ensure accuracy?
. Initial (ischemic) stage
. Early fragmentation stage
. Late fragmentation stage
. Reossification stage
. Residual stage

Correct Answer & Explanation

. Late fragmentation stage

Explanation

The lateral pillar classification assesses the height of the lateral aspect of the femoral head to predict outcomes. It is most accurately and reliably applied during the late fragmentation stage, when the maximum extent of epiphyseal collapse is visible.

Question 2071

Topic: Pediatric Hip

A 6-week-old infant is undergoing treatment with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up visit, it is noted that the anterior straps are overly tightened, placing the hip in excessive flexion. What is the most likely iatrogenic complication of this specific malpositioning?

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

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

In Pavlik harness treatment, excessive hip flexion (over-tightened anterior straps) stretches the femoral nerve against the inguinal ligament, causing a femoral nerve palsy. Conversely, excessive abduction (over-tightened posterior straps) increases the risk of avascular necrosis.

Question 2072

Topic: 4. Pediatrics

A 12-year-old obese boy presents with a 2-week history of knee pain and an obligate external rotation of the hip during active flexion. An AP pelvis radiograph shows a widened physis. What is the most common long-term complication of the standard definitive surgical management?

. Chondrolysis
. Osteonecrosis of the femoral head
. Deep surgical site infection
. Loss of fixation and hardware failure
. Cam-type femoroacetabular impingement

Correct Answer & Explanation

. Cam-type femoroacetabular impingement

Explanation

In-situ pinning is the standard treatment for a stable slipped capital femoral epiphysis (SCFE). Because the deformity is not acutely corrected, patients commonly develop cam-type femoroacetabular impingement due to the prominent anterolateral metaphysis.

Question 2073

Topic: Pediatric Hip
A 4-month-old girl is diagnosed with developmental dysplasia of the hip (DDH). Ultrasound confirms a dislocated left hip that is reducible. Treatment with a Pavlik harness is initiated. Which complication is most likely if the hips are positioned in excessive hyperflexion (>120 degrees)?
. Avascular necrosis of the femoral head
. Femoral nerve palsy
. Inferior hip dislocation
. Persistent acetabular dysplasia
. Obturator nerve palsy

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Hyperflexion of the hips in a Pavlik harness compresses the femoral nerve against the inguinal ligament, leading to transient femoral nerve palsy. Conversely, excessive abduction significantly increases the risk of avascular necrosis of the femoral head.

Question 2074

Topic: Pediatric Hip

A 13-year-old obese male presents with a 2-week history of worsening groin pain and a sudden inability to bear weight on the right leg after a minor slip. Radiographs confirm a severe slipped capital femoral epiphysis (SCFE). Which of the following factors is the most significant predictor for the development of avascular necrosis (AVN) in this patient?

. Severity of the slip angle
. Duration of prodromal symptoms
. Inability to bear weight (instability)
. Body mass index
. Male gender

Correct Answer & Explanation

. Inability to bear weight (instability)

Explanation

Instability, defined clinically as the inability to bear weight even with crutches, is the most significant risk factor for AVN in SCFE. The rate of AVN in unstable SCFE can approach 50%, compared to near zero in stable slips.

Question 2075

Topic: Pediatric Hip

A 12-year-old obese boy presents with a 3-week history of left thigh pain and an antalgic gait. Radiographs confirm a slipped capital femoral epiphysis (SCFE). According to the modified Southwick classification, which of the following defines a "moderate" slip on a frog-leg lateral radiograph?

. An epiphyseal-shaft angle difference of less than 30 degrees compared to the normal side
. An epiphyseal-shaft angle difference of 30 to 50 degrees compared to the normal side
. An epiphyseal-shaft angle difference of greater than 50 degrees compared to the normal side
. Translation of less than 33% of the femoral neck diameter
. Translation of 33% to 50% of the femoral neck diameter

Correct Answer & Explanation

. An epiphyseal-shaft angle difference of 30 to 50 degrees compared to the normal side

Explanation

The Southwick classification uses the difference in the epiphyseal-shaft angle between the affected and normal hips on a frog-leg lateral radiograph. A difference of less than 30 degrees is mild, 30-50 degrees is moderate, and greater than 50 degrees is severe. Translation percentages refer to the Wilson classification.

Question 2076

Topic: 4. Pediatrics

In pediatric orthopedic assessment, which of the following signs is most indicative of developmental dysplasia of the hip (DDH) in an infant under 3 months of age?

. Significant limb length discrepancy.
. Trendelenburg gait.
. Positive Galeazzi sign.
. Limited hip abduction.
. Pain on hip movement.

Correct Answer & Explanation

. Limited hip abduction.

Explanation

Limited hip abduction is the most consistent and reliable clinical sign of DDH in an infant under 3 months of age. The Ortolani and Barlow maneuvers are used to assess reducibility and dislocatability, respectively. A significant limb length discrepancy and positive Galeazzi sign (unequal knee height with hips and knees flexed) suggest a unilateral hip dislocation, but might be less evident or reliable in the very young infant. A Trendelenburg gait is seen in older children who are walking, and pain is generally not a prominent feature of DDH in infants.

Question 2077

Topic: 4. Pediatrics

In the context of musculoskeletal pharmacology, which class of antibiotics is absolutely contraindicated in children due to the risk of cartilage damage?

. Penicillins.
. Cephalosporins.
. Macrolides.
. Fluoroquinolones.
. Tetracyclines.

Correct Answer & Explanation

. Fluoroquinolones.

Explanation

Fluoroquinolones (e.g., ciprofloxacin, levofloxacin) are generally contraindicated in children due to the risk of damage to growing cartilage, specifically arthropathy. While they may be used in exceptional, life-threatening circumstances where no other effective alternative exists, their routine use is avoided. Tetracyclines are avoided due to dental staining and bone growth inhibition in young children, but the specific cartilage damage risk makes fluoroquinolones particularly noteworthy in orthopedics. Penicillins, cephalosporins, and macrolides are commonly used in pediatric infections.

Question 2078

Topic: Pediatric Hip

An infant is undergoing treatment for Developmental Dysplasia of the Hip (DDH) using a Pavlik harness. During a follow-up, you notice decreased active knee extension on the affected side. What is the most likely cause of this complication?

. Excessive flexion of the hip causing femoral nerve compression
. Excessive abduction of the hip causing obturator nerve stretch
. Excessive extension causing sciatic nerve stretch
. Avascular necrosis of the femoral head
. Normal physiological response to the harness

Correct Answer & Explanation

. Excessive flexion of the hip causing femoral nerve compression

Explanation

Decreased active knee extension indicates a femoral nerve palsy, the most common nerve injury associated with the Pavlik harness. It is caused by hyperflexion of the hip and usually resolves upon adjusting the anterior straps.

Question 2079

Topic: Pediatric Upper Extremity & Spine
In a Paediatric Trauma scenario, a 6-year-old presents with a Gartland Type III supracondylar humeral fracture. The hand is pink but pulseless. Following closed reduction and percutaneous pinning, the hand remains pink and pulseless. What is the most appropriate next step?
. Immediate exploration of the brachial artery
. Observe and admit for 24 hours with elevation
. Perform an immediate forearm fasciotomy
. Remove the pins and attempt open reduction
. Order a CT angiogram before deciding on further management

Correct Answer & Explanation

. Observe and admit for 24 hours with elevation

Explanation

For a 'pink, pulseless' hand after satisfactory reduction and stabilization of a paediatric supracondylar fracture, the standard protocol is close observation. Collateral circulation is adequate for tissue viability, and the pulse often returns within 24-48 hours.

Question 2080

Topic: Pediatric Hip

A 13-year-old obese boy presents with an acute-on-chronic exacerbation of groin pain and an inability to bear weight. Radiographs confirm an unstable slipped capital femoral epiphysis (SCFE). Which of the following complications has the highest incidence following surgical management of this specific injury pattern?

. Chondrolysis
. Avascular necrosis (AVN)
. Femoroacetabular impingement
. Leg length discrepancy
. Hardware failure

Correct Answer & Explanation

. Avascular necrosis (AVN)

Explanation

Unstable SCFE, defined clinically by an inability to bear weight, carries a high risk of avascular necrosis (up to 47%). Urgent decompression and stabilization are debated, but the AVN risk remains inherently tied to the initial vascular insult of the unstable slip.

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