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4. Pediatrics MCQs

Practice Set 114 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 2261

Topic: Pediatric Hip

An 8-week-old female infant is treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). During a follow-up visit, the mother notes that the infant is no longer kicking her leg on the affected side. Examination reveals an absent patellar reflex and inability to actively extend the knee. What positioning error in the Pavlik harness most likely caused this complication?

. Excessive hip flexion
. Inadequate hip flexion
. Excessive hip abduction
. Inadequate hip abduction
. Excessive internal rotation

Correct Answer & Explanation

. Excessive hip flexion

Explanation

The clinical picture describes a femoral nerve palsy, a known complication of the Pavlik harness. It is typically caused by excessive hip flexion (often >120 degrees), which compresses the femoral nerve against the inguinal ligament. Excessive hip abduction, conversely, places the patient at a higher risk for avascular necrosis (AVN) of the femoral head.

Question 2262

Topic: Pediatric Hip

A 7-year-old boy is diagnosed with Legg-Calve-Perthes disease. According to the Herring Lateral Pillar Classification, which of the following describes a Group B hip, and what is its prognostic significance?

. No lucency in the lateral pillar; uniformly good prognosis
. Less than 50% loss of lateral pillar height; variable prognosis depending on age
. Greater than 50% loss of lateral pillar height; uniformly poor prognosis
. Complete collapse of the lateral pillar; invariably requires salvage surgery
. Central pillar collapse with an intact lateral pillar; uniformly good prognosis

Correct Answer & Explanation

. Less than 50% loss of lateral pillar height; variable prognosis depending on age

Explanation

The Herring Lateral Pillar Classification assesses the height of the lateral pillar of the femoral head on an AP radiograph during the fragmentation stage. Group A has no loss of height; Group B has >50% maintained (i.e., <50% loss of height); Group C has <50% of the height maintained. Group B hips generally have a good outcome in patients <8 years old but a less predictable/worse outcome in older patients.

Question 2263

Topic: Pediatric Hip

A 12-year-old boy presents with a left-sided severe slipped capital femoral epiphysis (SCFE). Which of the following factors provides the strongest indication for prophylactic pinning of the asymptomatic contralateral hip?

. Male gender
. Obesity (BMI > 95th percentile)
. Presence of an underlying endocrine disorder
. Age greater than 14 years at presentation
. African American ethnicity

Correct Answer & Explanation

. Presence of an underlying endocrine disorder

Explanation

Prophylactic pinning of the contralateral hip in SCFE is heavily debated, but there is broad consensus that patients with underlying endocrine disorders (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) or previous radiation therapy are at a remarkably high risk of developing a contralateral slip. Thus, prophylactic pinning is strongly indicated in these populations.

Question 2264

Topic: Pediatric Hip

A 3-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. At follow-up, the mother reports the infant has stopped kicking her left leg. On examination, the infant lacks active knee extension, but passive knee range of motion is normal. Which nerve is most likely compressed, and what positioning error causes this complication?

. Sciatic nerve; hyperflexion of the hip
. Femoral nerve; hyperflexion of the hip
. Obturator nerve; excessive abduction
. Femoral nerve; excessive abduction
. Sciatic nerve; excessive extension

Correct Answer & Explanation

. Femoral nerve; hyperflexion of the hip

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness and presents with decreased active knee extension. It is typically caused by excessive flexion of the hip. The treatment is temporarily loosening the anterior straps or discontinuing the harness until nerve function returns.

Question 2265

Topic: 4. Pediatrics

A 2-year-old child is being evaluated for bilateral tibia vara (bowlegs). The surgeon suspects infantile Blount's disease rather than physiologic bowing. Which of the following radiographic measurements strongly predicts the development of Blount's disease over physiologic bowing?

. Metaphyseal-diaphyseal angle (MDA) > 11 degrees
. Tibiofemoral angle > 15 degrees
. Metaphyseal-diaphyseal angle (MDA) < 11 degrees
. Epiphyseal widening on the lateral side of the knee
. Presence of a normal distal femoral physis

Correct Answer & Explanation

. Metaphyseal-diaphyseal angle (MDA) > 11 degrees

Explanation

The metaphyseal-diaphyseal angle (MDA) of Drennan is highly useful in distinguishing physiologic bowing from infantile Blount's disease. An MDA greater than 11 degrees is strongly predictive of progression to Blount's disease, whereas an angle less than 11 degrees usually resolves as physiologic bowing.

Question 2266

Topic: Pediatric Hip

A 12-year-old obese male presents with a left-sided slipped capital femoral epiphysis (SCFE). Which of the following is the strongest indication for prophylactic in situ pinning of the contralateral right hip?

. Male gender
. African American ethnicity
. Presence of an underlying endocrine disorder
. Body mass index > 95th percentile
. Slip angle greater than 50 degrees on the affected side

Correct Answer & Explanation

. Presence of an underlying endocrine disorder

Explanation

Endocrinopathies (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy) are strong indications for prophylactic contralateral pinning in SCFE due to the very high risk (often >50%) of subsequent bilateral involvement. Age < 10 years or an open triradiate cartilage are also significant risk factors for bilaterality.

Question 2267

Topic: Pediatric Lower Extremity

In the Ponseti method for the treatment of congenital idiopathic clubfoot, what is the correct sequence of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method systematically corrects clubfoot deformities in a specific sequence, remembered by the acronym CAVE: Cavus, Adductus, Varus, and Equinus. The first cast supinates the forefoot to align it with the midfoot and hindfoot, correcting the cavus. Subsequent casts correct adductus and varus by abducting the supinated foot around the head of the talus. Equinus is corrected last, often requiring a percutaneous Achilles tenotomy.

Question 2268

Topic: Pediatric Hip

A 6-week-old female infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). She has been strictly in the harness for 4 weeks, but a repeat ultrasound demonstrates that the hip remains persistently dislocated. What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 3 weeks
. Discontinue the Pavlik harness and transition to a rigid abduction orthosis or schedule closed reduction
. Perform an immediate open reduction and spica casting
. Switch to double-diapering
. Perform a varus derotational osteotomy (VDRO)

Correct Answer & Explanation

. Discontinue the Pavlik harness and transition to a rigid abduction orthosis or schedule closed reduction

Explanation

Prolonged use of a Pavlik harness in a persistently dislocated hip leads to 'Pavlik harness disease', characterized by erosion of the posterior acetabular wall, which makes future reduction significantly more difficult. If a hip remains dislocated after 3 to 4 weeks of strict Pavlik harness wear, the harness must be discontinued. The accepted next step is transitioning to a rigid abduction brace (e.g., Ilfeld) or proceeding to closed reduction and spica casting.

Question 2269

Topic: Pediatric Hip

A 13-year-old obese male presents to the emergency department complaining of right hip and thigh pain after slipping on ice. He is completely unable to bear weight on the right leg, even with crutches. Radiographs demonstrate a displaced Slipped Capital Femoral Epiphysis (SCFE) of the right hip. Based on the Loder classification, what is his primary risk regarding the natural history of this specific injury pattern?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Coxa magna
. Femoroacetabular impingement (FAI)
. Premature physeal closure

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

According to the Loder classification, SCFE is divided into stable and unstable. 'Unstable' is defined clinically as the inability to ambulate, even with assistive devices (crutches). The incidence of avascular necrosis (AVN) in unstable SCFE is extremely high (up to 47%), whereas it is nearly 0% in stable SCFE.

Question 2270

Topic: 4. Pediatrics

What is the most frequently injured nerve in an extension-type supracondylar fracture of the humerus in a pediatric patient?

. Ulnar nerve
. Anterior interosseous nerve
. Posterior interosseous nerve
. Axillary nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior interosseous nerve

Explanation

The anterior interosseous nerve (AIN), a branch of the median nerve, is the most frequently injured nerve in extension-type supracondylar fractures of the humerus. This is typically due to traction over the proximal fragment. AIN palsy presents with the inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger (loss of the 'OK' sign).

Question 2271

Topic: Pediatric Hip

What is the most devastating and rapid complication specifically associated with the surgical pinning of an unstable Slipped Capital Femoral Epiphysis (SCFE)?

. Chondrolysis
. Osteonecrosis (Avascular Necrosis) of the femoral head
. Femoroacetabular impingement
. Progressive leg length discrepancy
. Premature osteoarthritis

Correct Answer & Explanation

. Osteonecrosis (Avascular Necrosis) of the femoral head

Explanation

Osteonecrosis (AVN) is the most devastating complication of SCFE, occurring at a significantly higher rate in unstable SCFE (reported up to 47%) compared to stable SCFE (almost 0%). It is typically caused by disruption of the retinacular vessels, which can be exacerbated by forceful closed reduction or hematoma accumulation.

Question 2272

Topic: Pediatric Hip

When treating an infant for Developmental Dysplasia of the Hip (DDH) using a Pavlik harness, hyperflexion of the hips beyond 120 degrees places the child at significant risk for which specific complication?

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

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Excessive hip flexion (typically >120 degrees) in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to an iatrogenic femoral nerve palsy. Excessive hip abduction, on the other hand, compromises the medial circumflex femoral artery and leads to avascular necrosis.

Question 2273

Topic: Pediatric Hip

A 6-week-old female infant is undergoing an ultrasound evaluation for Developmental Dysplasia of the Hip (DDH). According to the Graf classification, what does the alpha angle measure and what is considered a normal value (Type I hip)?

. Measures the cartilaginous roof; normal is > 60 degrees
. Measures the cartilaginous roof; normal is < 55 degrees
. Measures the bony acetabular roof; normal is > 60 degrees
. Measures the bony acetabular roof; normal is < 55 degrees
. Measures the femoral head coverage; normal is > 50%

Correct Answer & Explanation

. Measures the bony acetabular roof; normal is > 60 degrees

Explanation

In the Graf classification for DDH ultrasound, the alpha angle measures the bony roof of the acetabulum (formed by the ilium). A normal alpha angle (Graf Type I) is > 60 degrees. The beta angle measures the cartilaginous roof.

Question 2274

Topic: Pediatric Hip

A 12-year-old obese male presents with a unilateral left-sided Slipped Capital Femoral Epiphysis (SCFE) and undergoes in situ pinning. When evaluating the risk of a contralateral slip to determine the need for prophylactic pinning, which of the following radiographic parameters is the strongest predictor of a future contralateral slip?

. Initial left-sided slip angle > 50 degrees
. Southwick slip angle of the normal right hip > 10 degrees
. Klein's line intersecting less than 20% of the epiphysis on the right
. Modified Oxford bone age score of 16 or less at initial presentation
. Widening of the right proximal femoral physis > 5 mm

Correct Answer & Explanation

. Modified Oxford bone age score of 16 or less at initial presentation

Explanation

The modified Oxford bone age score uses AP pelvis radiographs to evaluate the maturation of the ilium and the triradiate cartilage. A score of 16 or less indicates significant remaining skeletal growth and has been proven in multiple studies (such as those by Stasikelis et al. and Popejoy et al.) to be a strong independent predictor of subsequent contralateral slip, thus strongly supporting the decision for prophylactic pinning.

Question 2275

Topic: Pediatric Hip

On an anteroposterior (AP) radiograph of the pelvis in a 6-month-old infant being evaluated for Developmental Dysplasia of the Hip (DDH), Hilgenreiner's line and Perkin's line are drawn to assess the position of the femoral head. In a normal, non-dysplastic hip, the ossific nucleus of the proximal femur should be located in which of the following quadrants?

. Superomedial quadrant
. Superolateral quadrant
. Inferomedial quadrant
. Inferolateral quadrant
. Centered directly on the intersection of the two lines

Correct Answer & Explanation

. Inferomedial quadrant

Explanation

Hilgenreiner's line is drawn horizontally through the triradiate cartilages. Perkin's line is drawn perpendicularly downwards from the lateral margin of the acetabulum. In a normal hip, the ossific nucleus of the femoral head (or the medial beak of the metaphysis if unossified) sits in the inferomedial quadrant.

Question 2276

Topic: Pediatric Hip
A 7-year-old boy is diagnosed with Legg-Calvรฉ-Perthes disease. During the fragmentation stage, an AP pelvis radiograph demonstrates that the lateral pillar of the affected femoral head maintains 40% of its original height. According to the Herring Lateral Pillar classification, which group does this hip fall into?
. Group A
. Group B
. Group C
. Group B/C border
. Group D

Correct Answer & Explanation

. Group C

Explanation

The Herring Lateral Pillar classification assesses the height of the lateral pillar of the femoral head on an AP radiograph during the fragmentation stage. Group A has no loss of height. Group B maintains > 50% of lateral pillar height. Group C maintains < 50% of the lateral pillar height. A height of 40% clearly places the hip in Group C, which is associated with a poor prognosis regardless of treatment, especially in older children (> 8 years).

Question 2277

Topic: 4. Pediatrics

Which of the following genetic or molecular factors is most strongly associated with the pathogenesis of Ossification of the Posterior Longitudinal Ligament (OPLL)?

. Mutations in the FGFR3 gene
. Overexpression of TGF-beta and BMP-2
. Defect in type I collagen synthesis
. Sclerostin deficiency
. VHL gene mutation

Correct Answer & Explanation

. Overexpression of TGF-beta and BMP-2

Explanation

OPLL pathogenesis is heavily linked to genetic and mechanical factors, with overexpression of bone morphogenetic protein-2 (BMP-2) and transforming growth factor-beta (TGF-beta) playing a key role in the enchondral ossification of the posterior longitudinal ligament. FGFR3 is related to achondroplasia, type I collagen to osteogenesis imperfecta, and sclerostin deficiency to sclerosteosis/van Buchem disease.

Question 2278

Topic: Pediatric Hip

A 12-year-old overweight boy presents with an antalgic gait. Radiographs confirm a mild left Slipped Capital Femoral Epiphysis (SCFE). Which of the following is an accepted and strongly supported indication for prophylactic in situ pinning of the contralateral right hip?

. Male gender
. Obesity alone
. Modified Oxford bone age score of 16 or lower
. Southwick angle greater than 50 degrees on the affected side
. Open triradiate cartilage

Correct Answer & Explanation

. Open triradiate cartilage

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but widely indicated in patients at high risk for a subsequent slip. Known strong risk factors for a contralateral slip include an open triradiate cartilage (indicating significant skeletal immaturity), underlying endocrine disorders (e.g., hypothyroidism), and very young age (girls <10, boys <12).

Question 2279

Topic: 4. Pediatrics

A 4-week-old infant with developmental dysplasia of the hip (DDH) is treated with a Pavlik harness. Two weeks later, the parents notice the infant is no longer actively extending the knee on the affected side, although ankle and toe movements are normal. What is the most likely diagnosis and the most appropriate next step in management?

. Sciatic nerve palsy; loosen the posterior straps
. Obturator nerve palsy; switch to a rigid abduction orthosis
. Spastic diplegia; urgent referral to pediatric neurology
. Femoral nerve palsy; remove the harness and observe until recovery
. Femoral nerve palsy; tighten the anterior straps to maximize hip flexion

Correct Answer & Explanation

. Femoral nerve palsy; remove the harness and observe until recovery

Explanation

The most common neurologic complication of a Pavlik harness is a femoral nerve palsy, typically resulting from hyperflexion of the hip which stretches or compresses the nerve. Clinical signs include a loss of active quadriceps function (knee extension). The standard management is to immediately remove the harness or significantly reduce hip flexion to allow the nerve to recover before resuming DDH treatment.

Question 2280

Topic: Pediatric Hip

A 12-year-old male is diagnosed with a unilateral slipped capital femoral epiphysis (SCFE) and undergoes in situ pinning. Which of the following represents the strongest absolute indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Age greater than 14 years at presentation
. A slip angle of less than 30 degrees (Grade 1) on the affected side
. Closure of the triradiate cartilage
. Male sex and athletic participation
. Presence of underlying endocrine disorders (e.g., hypothyroidism)

Correct Answer & Explanation

. Presence of underlying endocrine disorders (e.g., hypothyroidism)

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is universally recommended for patients with underlying endocrinopathies (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy), previous radiation therapy, or presentation at an atypically young age (< 10 years). These populations have an exceptionally high risk of developing a contralateral slip.

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