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4. Pediatrics MCQs

Practice Set 233 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 4641

Topic: 4. Pediatrics

A 6-month-old infant with a homozygous FGFR3 mutation (achondroplasia phenotype) presents with failure to thrive, hyperreflexia, and central sleep apnea. Which of the following is the most appropriate next step in management?

. Polysomnography followed by nocturnal CPAP
. MRI of the craniocervical junction
. Observation, as these symptoms typically resolve by age 2 with cranial growth
. Immediate suboccipital decompression with C1 laminectomy without further imaging
. High-dose Vitamin D and calcium supplementation

Correct Answer & Explanation

. Polysomnography followed by nocturnal CPAP

Explanation

Achondroplasia is caused by an activating mutation in FGFR3, inhibiting enchondral ossification. The most life-threatening complication in infants is cervicomedullary compression at the foramen magnum. Clinical signs include central sleep apnea, failure to thrive, brisk reflexes, and hypotonia. When these symptoms are present, prompt MRI of the craniocervical junction is mandatory to evaluate the severity of foramen magnum stenosis prior to surgical intervention (suboccipital decompression).

Question 4642

Topic: Pediatric Upper Extremity & Spine
A newborn is noted to have severe radial deviation of the right wrist, an absent right thumb, and shortening of the right forearm. Radiographs reveal an absent radius. To rule out the most life-threatening associated condition, which of the following screening tests should be ordered initially?
. Renal ultrasound
. Echocardiogram
. Chromosomal breakage test (Diepoxybutane test)
. Complete blood count (CBC) with peripheral smear
. Whole-spine MRI

Correct Answer & Explanation

. Chromosomal breakage test (Diepoxybutane test)

Explanation

Radial longitudinal deficiency (radial clubhand) is strongly associated with several systemic syndromes including VACTERL, TAR (Thrombocytopenia-Absent Radius), Holt-Oram, and Fanconi anemia. Fanconi anemia is the most life-threatening because it leads to fatal aplastic anemia and a high risk of malignancies (leukemia). The definitive screening test is chromosomal breakage analysis induced by diepoxybutane (DEB). A CBC may be normal in the neonatal period before marrow failure manifests, making it an insufficient screen.

Question 4643

Topic: 4. Pediatrics
A 13-year-old girl sustains an ankle injury. Radiographs demonstrate a Salter-Harris III fracture of the anterolateral distal tibia. Which of the following ligaments is responsible for the avulsion of this fracture fragment?
. Anterior talofibular ligament
. Calcaneofibular ligament
. Anterior inferior tibiofibular ligament
. Posterior inferior tibiofibular ligament
. Deltoid ligament

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. It occurs during adolescence due to the asymmetric closure pattern of the distal tibial physis (closes central -> anteromedial -> posteromedial -> lateral last). An external rotation force applied to the foot puts tension on the Anterior Inferior Tibiofibular Ligament (AITFL), which avulses the unfused anterolateral epiphysis.

Question 4644

Topic: Pediatric Lower Extremity

A newborn is diagnosed with Aitken Class A proximal focal femoral deficiency (PFFD). The predicted leg length discrepancy at maturity is 15 cm. The hip joint is present with a cartilaginous connection between the femoral head and shaft, and the foot is normal. Which of the following is the most appropriate long-term surgical strategy?

. Early knee fusion and Boyd amputation
. Ilizarov lengthening of the femur and tibia
. Van Nes rotationplasty
. Hip arthrodesis and Syme amputation
. Pelvic support osteotomy

Correct Answer & Explanation

. Early knee fusion and Boyd amputation

Explanation

Aitken Class A PFFD is characterized by the presence of a femoral head and acetabulum, with a cartilaginous connection to the shortened femoral shaft that typically ossifies later, providing a stable, functioning hip. For patients with stable hip and knee joints, a functional foot, and a predicted limb length discrepancy (LLD) of less than 20 cm, limb lengthening procedures (usually staged femoral and tibial lengthening) are indicated. Amputations and rotationplasties are reserved for more severe deficiencies (Aitken C and D, or LLD > 20 cm) where joints are unstable or absent.

Question 4645

Topic: 4. Pediatrics

A 2.5-year-old overweight female presents with bilateral tibial bowing. Radiographs demonstrate medial metaphyseal beaking. The Drennan metaphyseal-diaphyseal angle (MDA) is measured at 18 degrees on the right and 10 degrees on the left. Which of the following is the most appropriate management?

. Reassurance and observation for both legs
. Knee-ankle-foot orthosis (KAFO) for the right leg, observe the left
. Bilateral proximal tibial valgus-producing osteotomies
. Right proximal tibial valgus-producing osteotomy, observe the left
. Guided growth with lateral tension band plates bilaterally

Correct Answer & Explanation

. Reassurance and observation for both legs

Explanation

Infantile Blount's disease is differentiated from physiologic bowing by an abnormal metaphyseal-diaphyseal angle (MDA) described by Drennan. An MDA > 16 degrees carries a high likelihood of progression, whereas an MDA < 10 degrees is likely physiologic and will resolve. Given the age (under 3 years) and an MDA of 18 degrees on the right, bracing with a KAFO (worn during weight-bearing) is the standard initial treatment to unload the medial compartment. Surgery is indicated if bracing fails or if the child presents with advanced disease > 3-4 years of age.

Question 4646

Topic: Pediatric Hip

A 12-year-old obese boy is brought to the emergency department unable to bear weight on his left leg after a minor fall 12 hours ago. He has a 3-week history of preceding left groin pain. Radiographs confirm a severe left slipped capital femoral epiphysis (SCFE). Which of the following accurately describes his risk of developing avascular necrosis (AVN) based on his presentation, and the appropriate urgency of treatment?

. High risk (up to 50%); urgent pinning or open reduction within 24 hours
. Low risk (<10%); elective pinning within 1 week
. High risk (up to 50%); closed reduction followed by spica casting
. Low risk (<10%); urgent open reduction and internal fixation
. Absolute risk (100%); primary proximal femoral osteotomy

Correct Answer & Explanation

. High risk (up to 50%); urgent pinning or open reduction within 24 hours

Explanation

The inability to bear weight even with crutches defines an unstable SCFE according to the Loder classification. Unstable SCFE has a very high risk of avascular necrosis (up to 47-50%), in stark contrast to stable SCFE (<10% risk).Current literature suggests that urgent decompression of the intracapsular hematoma and stable fixation (either pinning in situ or open reduction with a modified Dunn procedure) within 24 hours can mitigate the risk of AVN. Forceful closed reduction is contraindicated as it further increases AVN risk.

Question 4647

Topic: Pediatric Hip

A 4-year-old girl is undergoing surgical treatment for residual developmental dysplasia of the hip (DDH). The surgeon

plans an incomplete transiliac osteotomy that hinges on the triradiate cartilage, allowing primarily anterior and lateral coverage of the femoral head by changing the volume and shape of the acetabulum, without disrupting the sciatic notch. Which osteotomy is being described?

. Salter osteotomy
. Pemberton osteotomy
. Dega osteotomy
. Steel triple osteotomy
. Chiari osteotomy

Correct Answer & Explanation

. Salter osteotomy

Explanation

The Pemberton osteotomy is a pericapsular, incomplete osteotomy of the ilium that uses the flexible triradiate (Y) cartilage as a hinge. It redirects the acetabular roof to provide anterolateral coverage and effectively decreases acetabular volume. The Salter osteotomy is a complete transiliac cut that hinges at the pubic symphysis. The Dega is an incomplete transiliac osteotomy typically hinging on intact medial iliac cortex, used heavily in neuromuscular dysplasia to provide lateral, anterior, and posterior coverage without entering the sciatic notch.

Question 4648

Topic: Pediatric Hip
A 9-year-old boy presents with a painless limp. Radiographs demonstrate fragmentation of the right capital femoral epiphysis with >50% loss of lateral pillar height. Based on the Herring Lateral Pillar Classification, what is the assigned grade and the expected prognosis?
. Lateral Pillar B; good outcome with nonoperative treatment
. Lateral Pillar C; poor outcome regardless of treatment
. Lateral Pillar B/C; excellent outcome if contained surgically
. Lateral Pillar C; improved outcome with surgical containment compared to conservative
. Lateral Pillar A; good outcome without treatment

Correct Answer & Explanation

. Lateral Pillar C; poor outcome regardless of treatment

Explanation

According to the Herring Lateral Pillar classification for Legg-Calve-Perthes disease: Group A = no loss of lateral pillar height; Group B = <50% loss; Group C = >50% loss. This patient has Pillar C. The multicenter prospective study by Herring et al. demonstrated that patients over the age of 8 years at the time of disease onset who present with Pillar C hips have uniformly poor outcomes (development of non-spherical femoral heads and early osteoarthritis) regardless of whether they receive conservative or operative containment treatment.

Question 4649

Topic: 4. Pediatrics

A 3-year-old child presents with worsening bilateral tibia vara. You are evaluating the radiograph to differentiate between physiologic bowing and infantile Blount disease.

Which of the following radiographic parameters correctly points towards the diagnosis of infantile Blount disease?

. Tibiofemoral angle > 15 degrees
. Metaphyseal-diaphyseal angle (MDA) > 16 degrees
. Metaphyseal-diaphyseal angle (MDA) < 11 degrees
. Mechanical axis deviation (MAD) strictly in the lateral compartment
. A narrow distal femoral physis

Correct Answer & Explanation

. Tibiofemoral angle > 15 degrees

Explanation

The metaphyseal-diaphyseal angle (MDA), or Drennan's angle, is used to differentiate physiologic bowing from infantile Blount disease. An MDA greater than 16 degrees has a high likelihood of progressing to Blount disease, whereas an MDA of less than 11 degrees typically indicates physiologic bowing that will resolve spontaneously.

Question 4650

Topic: 4. Pediatrics
A neonate sustains multiple long bone fractures during delivery. Genetic testing reveals a qualitative defect in Type I collagen. According to the Sillence classification for Osteogenesis Imperfecta (OI), which type is characterized as perinatally lethal?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

Osteogenesis imperfecta (OI) is a connective tissue disorder typically caused by defects in the COL1A1 or COL1A2 genes. In the Sillence classification, Type II is perinatally lethal, often presenting with multiple rib and long bone fractures in utero and severe pulmonary hypoplasia. Type I is the most common and mildest form; Type III is progressively deforming; and Type IV is intermediate in severity.

Question 4651

Topic: 4. Pediatrics

A 2-year-old child presents with short stature, frontal bossing, and rhizomelic shortening of the limbs.

Which of the following best describes the molecular pathophysiology of this condition?

. Loss-of-function mutation in COL1A1
. Loss-of-function mutation in FGFR3
. Gain-of-function mutation in FGFR3
. Mutation in Cartilage Oligomeric Matrix Protein (COMP)
. Mutation in the CBFA1/RUNX2 transcription factor

Correct Answer & Explanation

. Loss-of-function mutation in COL1A1

Explanation

The patient has achondroplasia, the most common form of dwarfism, which is characterized by rhizomelic (proximal) limb shortening. It is inherited in an autosomal dominant fashion, though 80% are new mutations. The pathophysiology involves a gain-of-function mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene on chromosome 4, which abnormally inhibits chondrocyte proliferation in the proliferative zone of the physis.

Question 4652

Topic: 4. Pediatrics

You are evaluating a 6-year-old with spastic quadriplegic cerebral palsy as part of routine hip surveillance.

According to most hip surveillance guidelines, reconstructive bony surgery (e.g., varus derotational osteotomy and pelvic osteotomy) is generally indicated when the Reimers Migration Percentage (MP) exceeds what threshold?

. 10%
. 20%
. 40%
. 80%
. 100%

Correct Answer & Explanation

. 10%

Explanation

In cerebral palsy hip surveillance, Reimers Migration Percentage (MP) is the key radiographic parameter. An MP > 30% indicates subluxation. While soft tissue releases (adductors/psoas) may be indicated for an MP of 30-40%, reconstructive bony surgery (VDRO and often pelvic osteotomy) is formally indicated when the MP exceeds 40% with architectural dysplasia, as non-operative or soft tissue management alone is likely to fail.

Question 4653

Topic: 4. Pediatrics

A newborn presents with a shortened right lower extremity, an anteromedial bowing of the tibia, and an absent lateral ray (toe) of the right foot.

Radiographs confirm fibular hemimelia. Which of the following soft-tissue anomalies of the knee is almost universally present in this condition?

. Absent anterior cruciate ligament
. Absent posterior cruciate ligament
. Absent medial collateral ligament
. Congenital bipartite patella
. Medial patellofemoral ligament hypoplasia

Correct Answer & Explanation

. Absent anterior cruciate ligament

Explanation

Fibular hemimelia is the most common congenital longitudinal deficiency of the long bones. It is almost universally associated with an absent or hypoplastic anterior cruciate ligament (ACL), a ball-and-socket ankle joint, absent lateral rays of the foot, and variable femoral shortening (often linked with PFFD).

Question 4654

Topic: Pediatric Lower Extremity

In a patient with Proximal Focal Femoral Deficiency (PFFD), the Aitken classification is widely used to guide treatment.

Which Aitken type is characterized by the complete absence of a femoral head and an absent or severely dysplastic acetabulum, precluding joint reconstruction?

. Type A
. Type B
. Type C
. Type D
. Type E

Correct Answer & Explanation

. Type A

Explanation

The Aitken classification of PFFD includes four types (A-D). Type D represents the most severe form, characterized by an absent acetabulum, absent femoral head, and severely shortened femoral shaft without a proximal tuft. Types A and B have an existing femoral head with an osseous or cartilaginous connection to the shaft, while Type C has an absent femoral head but a present acetabulum.

Question 4655

Topic: 4. Pediatrics

A 9-year-old boy presents with a progressive angular deformity of the distal femur following a distal femoral physeal fracture two years prior.

Advanced imaging confirms a bony physeal bar. What are the generally accepted criteria for attempting a surgical physeal bar excision?

. Bar involves > 50% of the physis, and at least 2 cm of growth remaining
. Bar involves < 50% of the physis, and at least 2 cm of growth remaining
. Bar involves < 50% of the physis, and less than 1 year of growth remaining
. Only peripheral bars, regardless of size or growth remaining
. Only central bars, regardless of size or growth remaining

Correct Answer & Explanation

. Bar involves > 50% of the physis, and at least 2 cm of growth remaining

Explanation

Surgical excision of a physeal bar (with interposition of fat or cranioplast) is generally indicated if the bar encompasses less than 50% of the cross-sectional area of the physis AND the patient has at least 2 years or 2 cm of growth remaining. Exceeding 50% carries a very high rate of failure, and limited remaining growth makes the procedure futile, warranting corrective osteotomy or epiphysiodesis instead.

Question 4656

Topic: Pediatric Lower Extremity

You are treating an infant with an idiopathic clubfoot using the Ponseti method. The first step involves correcting the cavus deformity. What specific manipulation is required to achieve this first step?

. Supination of the forefoot with depression of the first metatarsal
. Pronation of the forefoot with depression of the first metatarsal
. Elevation of the first metatarsal to supinate the forefoot
. Abduction of the midfoot with counter-pressure on the medial malleolus
. Forced dorsiflexion of the ankle

Correct Answer & Explanation

. Supination of the forefoot with depression of the first metatarsal

Explanation

In the Ponseti method, the acronym CAVE guides the sequence of correction: Cavus, Adductus, Varus, and Equinus. The cavus is corrected first. Because the cavus in a clubfoot is caused by a plantarflexed first ray, correction is achieved by supinating the forefoot to match the hindfoot, which specifically requires elevating the first metatarsal.

Question 4657

Topic: Pediatric Hip

A 3-month-old infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). During follow-up, the parents note the child is not kicking the affected leg. On examination, there is decreased spontaneous extension of the knee on the affected side. What is the most likely cause?

. Sciatic nerve palsy due to hyperflexion
. Obturator nerve palsy due to hyperabduction
. Femoral nerve palsy due to hyperflexion
. Avascular necrosis of the femoral head
. Transient synovitis

Correct Answer & Explanation

. Sciatic nerve palsy due to hyperflexion

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by excessive hip flexion (usually >100-110 degrees). It presents as an inability to extend the knee (quadriceps weakness). The treatment involves relaxing the anterior straps to decrease hip flexion, which usually leads to spontaneous recovery. Hyperabduction, on the other hand, puts the hip at risk for avascular necrosis (AVN).

Question 4658

Topic: Pediatric Hip

A 12-year-old boy requires in-situ fixation for a severe, stable slipped capital femoral epiphysis (SCFE).

Which of the following clinical profiles is a strong, widely accepted indication for prophylactic pinning of the contralateral, asymptomatic hip?

. A 12-year-old obese male with an acute unstable SCFE
. A 10-year-old with panhypopituitarism and a history of cranial radiation therapy
. A 14-year-old female with a chronic stable SCFE
. An 11-year-old male with a positive family history of SCFE
. A 13-year-old male with an isolated slip angle of 45 degrees

Correct Answer & Explanation

. A 12-year-old obese male with an acute unstable SCFE

Explanation

Prophylactic pinning of the contralateral hip in SCFE remains controversial for typical idiopathic cases. However, it is strongly indicated in patients with underlying endocrine disorders (such as hypothyroidism, panhypopituitarism), renal osteodystrophy, previous pelvic/cranial radiation, or very young age at presentation (<10 years old), because their risk of developing a contralateral slip can exceed 50-100%.

Question 4659

Topic: Pediatric Hip
A 6-year-old boy is undergoing treatment for Legg-Calvรฉ-Perthes disease. You are grading the severity using the Herring Lateral Pillar classification. During the fragmentation phase, the radiograph shows that approximately 60% of the lateral pillar height is maintained. How is this classified?
. Lateral Pillar Group A
. Lateral Pillar Group B
. Lateral Pillar Group B/C
. Lateral Pillar Group C
. Catterall Group IV

Correct Answer & Explanation

. Lateral Pillar Group B

Explanation

The Herring Lateral Pillar classification is assessed during the early fragmentation phase. Group A: no involvement of the lateral pillar (100% height). Group B: >50% of lateral pillar height maintained. Group C: <50% of lateral pillar height maintained. Group B/C is a border category with intermediate findings (thin lateral pillar, exactly 50%). Since 60% is maintained, it is Group B.

Question 4660

Topic: 4. Pediatrics
A 13-year-old girl presents with an ankle fracture involving the anterolateral distal tibial epiphysis, following an external rotation injury. What physiological closure pattern of the distal tibial physis explains the biomechanics of a juvenile Tillaux fracture?
. Central closes first, followed by anterolateral, then posteromedial
. Central closes first, followed by posteromedial, then anterolateral
. Posteromedial closes first, followed by anterolateral, then central
. Anterolateral closes first, followed by central, then posteromedial
. The physis closes symmetrically from medial to lateral

Correct Answer & Explanation

. Central closes first, followed by posteromedial, then anterolateral

Explanation

The distal tibial physis begins closing around age 12-14 in an asymmetric pattern: it closes first centrally, then spreads to the anteromedial and posteromedial aspects, and finally closes the anterolateral aspect. Because the anterolateral physis remains open last, an external rotation force avulses the anterolateral epiphysis via the anterior inferior tibiofibular ligament (AITFL), producing a Salter-Harris III fracture (Tillaux fracture).

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