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4. Pediatrics MCQs

Practice Set 159 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 3161

Topic: 4. Pediatrics
A 2.5-year-old girl is brought in by her parents for evaluation of bowing of her legs. On standing full-length radiographs, the metaphyseal-diaphyseal angle (Drennan's angle) is measured at 18 degrees bilaterally. What is the most appropriate next step in management?
. Reassurance and observation for physiologic bowing
. Vitamin D, calcium, and phosphorus laboratory workup
. Prescription of knee-ankle-foot orthoses (KAFOs)
. Bilateral proximal tibial valgus osteotomies
. Epiphysiodesis of the lateral proximal tibia

Correct Answer & Explanation

. Prescription of knee-ankle-foot orthoses (KAFOs)

Explanation

A metaphyseal-diaphyseal angle (Drennan's angle) greater than 16 degrees strongly suggests early infantile Blount's disease (tibia vara) rather than physiologic bowing. In children under 3 years of age with early-stage infantile Blount's disease, a trial of bracing with Knee-Ankle-Foot Orthoses (KAFOs) is indicated. If bracing fails or if the child is older (e.g., >3-4 years) with advanced Langenskiöld stages, proximal tibial osteotomy is warranted.

Question 3162

Topic: 4. Pediatrics

A 4-year-old boy with a history of multiple low-energy long bone fractures, blue sclerae, and dentinogenesis imperfecta is evaluated. A genetic disorder is suspected. The pathophysiology of this condition is primarily related to a defect in the synthesis of which of the following?

. Type II collagen
. Type I collagen
. Osteoclastic carbonic anhydrase II
. Fibroblast growth factor receptor 3 (FGFR3)
. Core binding factor alpha-1 (CBFA1 / RUNX2)

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta is primarily caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, which encode the alpha chains of type I collagen. This leads to defective synthesis of type I collagen, manifesting as bone fragility, blue sclerae, hearing loss, and dentinogenesis imperfecta. Type II collagen defects are associated with spondyloepiphyseal dysplasia. Defective osteoclasts are seen in osteopetrosis. FGFR3 mutations cause achondroplasia. CBFA1 mutations cause cleidocranial dysplasia.

Question 3163

Topic: 4. Pediatrics
A 14-year-old girl sustains an ankle injury while playing soccer. Radiographs reveal a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. The mechanism of injury involves avulsion by which of the following structures?
. Anterior talofibular ligament
. Anterior inferior tibiofibular ligament
. Posterior inferior tibiofibular ligament
. Deltoid ligament
. Calcaneofibular 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 in adolescents due to the asymmetrical closure pattern of the distal tibial physis, which closes first centrally, then medially, and finally laterally. An external rotation force causes the anterior inferior tibiofibular ligament (AITFL) to avulse the anterolateral epiphysis, which is the last portion of the physis to close.

Question 3164

Topic: Pediatric Hip

A 13-year-old boy with a BMI of 35 presents to the emergency department unable to bear weight on his left leg after a minor slip. Radiographs confirm an acute, severe left slipped capital femoral epiphysis (SCFE). He cannot bear weight even with crutches. What is the current consensus regarding surgical treatment for this patient to minimize complications?

. In situ pinning should be delayed for 7 days to allow soft tissues to rest
. Urgent surgical stabilization with capsular decompression reduces the risk of avascular necrosis
. Closed reduction with forceful manipulation followed by spica casting
. Prophylactic pinning of the contralateral hip must be done before addressing the symptomatic hip
. Primary total hip arthroplasty

Correct Answer & Explanation

. Urgent surgical stabilization with capsular decompression reduces the risk of avascular necrosis

Explanation

The patient has an unstable SCFE (defined by the inability to bear weight with or without crutches). Unstable SCFE is associated with a high risk of avascular necrosis (AVN). Current evidence suggests that urgent or emergent surgical stabilization (often within 24 hours), combined with capsular decompression (to reduce intracapsular tamponade), minimizes the risk of AVN. Forceful closed reduction is contraindicated as it increases the risk of AVN.

Question 3165

Topic: 4. Pediatrics
A 4-year-old boy who was successfully treated for bilateral idiopathic clubfeet as an infant using the Ponseti method presents with returning deformity in the right foot. During the swing phase of gait, the right foot supinates dynamically. Passive range of motion demonstrates fully correctable deformities without residual equinus. What is the most appropriate next step in surgical management?
. Repeat Ponseti casting followed by an Achilles tendon lengthening
. Split anterior tibial tendon transfer (SPLATT)
. Transfer of the entire tibialis anterior tendon to the lateral cuneiform
. Lateral column lengthening (Evans osteotomy)
. Comprehensive posterior medial soft tissue release

Correct Answer & Explanation

. Transfer of the entire tibialis anterior tendon to the lateral cuneiform

Explanation

Relapse in clubfoot treated with the Ponseti method often presents as dynamic supination during the swing phase of gait due to relative overactivity of the tibialis anterior muscle compared to the evertors. When the foot is passively correctable, the treatment of choice is the transfer of the entire tibialis anterior tendon to the lateral cuneiform (often preceded by a brief period of corrective casting). Unlike in cerebral palsy, where a SPLATT is common, the entire tendon is transferred in clubfoot relapse.

Question 3166

Topic: Pediatric Hip

A 6-week-old female is being treated with a Pavlik harness for a developmental dysplasia of the hip (DDH) that was dislocated but reducible on exam. At her 1-week follow-up, the parents report she has stopped kicking her left leg. On clinical examination, she holds the left knee in extension and does not actively contract her quadriceps with tickling. Ultrasound confirms the hip is currently reduced. What is the most appropriate next step in management?

. Decrease hip abduction by loosening the posterior straps
. Increase hip flexion by tightening the anterior straps
. Discontinue the harness until active quadriceps function returns
. Transition immediately to a rigid hip abduction orthosis
. Schedule urgent closed reduction and spica casting under anesthesia

Correct Answer & Explanation

. Discontinue the harness until active quadriceps function returns

Explanation

The clinical scenario describes a femoral nerve palsy, a known complication of treating DDH with a Pavlik harness caused by hyperflexion of the hip. Presenting signs include absent active knee extension and loss of quadriceps function. The appropriate initial management is to discontinue the harness to relieve pressure on the femoral nerve and allow for neurologic recovery, which typically occurs over a few days to weeks. Tightening straps or ignoring the palsy risks permanent nerve injury.

Question 3167

Topic: 4. Pediatrics

A 7-year-old boy with spastic quadriplegic cerebral palsy (GMFCS Level IV) presents with a slowly progressing scissoring gait, pain with diaper changes, and difficulty sitting in his wheelchair. A recent AP pelvis radiograph demonstrates a right hip Reimers migration percentage of 55%. The acetabulum is dysplastic, but there is no evidence of degenerative arthritis. What is the most appropriate definitive management?

. Bilateral adductor and psoas tenotomies with Botulinum toxin injection
. Open reduction, femoral varus derotational osteotomy (VDRO), and pelvic osteotomy
. Proximal femoral resection (Castle procedure)
. Total hip arthroplasty
. Observation and optimization of wheelchair seating

Correct Answer & Explanation

. Open reduction, femoral varus derotational osteotomy (VDRO), and pelvic osteotomy

Explanation

In non-ambulatory children with cerebral palsy, a hip migration percentage greater than 40-50% indicates significant subluxation with a high risk of progression to painful dislocation. Soft tissue releases alone (tenotomies) are insufficient at this stage and age. In the absence of severe degenerative changes, comprehensive bony reconstruction consisting of a varus derotational osteotomy (VDRO), pelvic osteotomy (e.g., Dega or San Diego), and often open reduction is the gold standard to provide a painless, stable, and locatable hip.

Question 3168

Topic: Pediatric Hip

A 13-year-old boy with a BMI in the 99th percentile presents to the emergency department with acute left groin pain. He states he twisted his leg getting out of bed. On examination, he is completely unable to bear weight on the left leg, even with the use of crutches. Radiographs demonstrate a severe posterior and inferior displacement of the left capital femoral epiphysis. According to the Loder classification, his inability to bear weight puts him at highest risk for which of the following complications?

. Chondrolysis
. Contralateral slipped capital femoral epiphysis
. Avascular necrosis (AVN) of the femoral head
. Femoroacetabular impingement (FAI)
. Nonunion of the proximal femoral physis

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

The Loder classification divides Slipped Capital Femoral Epiphysis (SCFE) into stable and unstable based strictly on the ability to bear weight (with or without crutches). An unstable SCFE (inability to bear weight) has a significantly higher rate of avascular necrosis (up to 50%), whereas AVN is exceedingly rare in stable SCFE. Chondrolysis is more commonly associated with unrecognized hardware penetration into the joint space.

Question 3169

Topic: Pediatric Upper Extremity & Spine

A 6-year-old girl falls from monkey bars and sustains a widely displaced, extension-type supracondylar humerus fracture. On initial presentation, she has no palpable radial pulse, but the hand is warm, pink, and has a brisk capillary refill of less than 2 seconds. She is taken urgently to the operating room, where an anatomic closed reduction is achieved and stabilized with three divergent lateral pins. After pinning, the hand remains pink and warm, but the radial pulse remains absent. What is the most appropriate next step in management?

. Immediate vascular surgery consultation for brachial artery exploration
. Remove the pins and perform an open reduction of the fracture
. Observation and admission for close neurovascular monitoring
. Immediate CT angiography of the upper extremity
. Administration of intra-arterial vasodilators

Correct Answer & Explanation

. Observation and admission for close neurovascular monitoring

Explanation

The management of a 'pulseless, pink' hand following adequate reduction and pinning of a supracondylar humerus fracture is observation and close monitoring. The pink color and brisk capillary refill indicate that collateral circulation is providing adequate perfusion to the hand. Routine vascular exploration is not indicated unless the hand becomes cool, pale, and ischemic (a 'pulseless, white' hand) after reduction.

Question 3170

Topic: Pediatric Hip
An 8-year-old boy presents with a 4-month history of a painless limp. Radiographs demonstrate fragmentation and sclerosis of the left proximal femoral epiphysis consistent with Legg-Calvé-Perthes disease. The lateral one-third of the femoral head exhibits a 60% loss of height compared to the contralateral normal hip. According to the Herring lateral pillar classification, what is his expected prognosis without surgical intervention?
. Lateral Pillar A, excellent prognosis
. Lateral Pillar B, favorable prognosis
. Lateral Pillar B/C border, variable prognosis
. Lateral Pillar C, poor prognosis
. Lateral Pillar C, excellent prognosis

Correct Answer & Explanation

. Lateral Pillar C, poor prognosis

Explanation

The Herring lateral pillar classification predicts outcome in Perthes disease based on the height of the lateral column of the epiphysis during the fragmentation stage. Group C implies >50% collapse of the lateral pillar. Patients in Group C generally have a poor prognosis with a high likelihood of aspherical congruency and early osteoarthritis, especially in children older than 8 years, regardless of surgical containment.

Question 3171

Topic: Pediatric Upper Extremity & Spine

A 12-year-old female presents to the clinic with an adolescent idiopathic scoliosis (AIS) right thoracic curve of 28 degrees. When counseling her parents about the risk of curve progression, you explain the concept of peak height velocity (PHV). Which of the following maturity indicators most closely corresponds to the peak velocity of growth in a patient with AIS?

. Closure of the triradiate cartilage
. Onset of menarche
. Risser stage 3
. Sanders maturity stage 3 (digital skeletal age)
. Transition from Risser stage 4 to 5

Correct Answer & Explanation

. Sanders maturity stage 3 (digital skeletal age)

Explanation

The peak height velocity (PHV) represents the phase of maximum linear growth and is the period of highest risk for curve progression in AIS. It typically occurs just before menarche. The Sanders maturity scale, which assesses the ossification of hand epiphyses, identifies Stage 3 (adolescent rapid-early) and Stage 4 (adolescent rapid-late) as the exact periods correlating with PHV. Triradiate cartilage closure is closely associated but Sanders 3 is the most precise indicator of the peak.

Question 3172

Topic: 4. Pediatrics

A 4-year-old girl whose weight is above the 95th percentile presents with a waddling gait and progressive bowing of both legs. Standing long-leg radiographs show medial metaphyseal beaking of the proximal tibiae and a metaphyseal-diaphyseal angle of 18 degrees. What physiological principle best explains the progression of her proximal medial tibial physeal deformity?

. Wolff's Law of bone remodeling
. The Heuter-Volkmann principle
. The tension-band biomechanical concept
. Galileo's principle of scaling
. Endochondral ossification failure due to vitamin D deficiency

Correct Answer & Explanation

. The Heuter-Volkmann principle

Explanation

The patient has infantile Blount's disease (tibia vara), which is characterized by a high metaphyseal-diaphyseal angle (>16 degrees) and progressive varus deformity. The underlying mechanism is explained by the Heuter-Volkmann principle, which states that excessive compressive forces across a physis inhibit longitudinal growth, whereas tensile forces stimulate it. In obese or early-walking children, excessive mechanical compression on the posteromedial proximal tibial physis inhibits its growth, exacerbating the varus deformity.

Question 3173

Topic: Pediatric Hip

A 3-month-old infant with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a follow-up visit, the parents report that the infant is not moving the right leg as much as the left. On physical examination, the right knee is held in extension, and the patellar reflex is absent on the right side. What is the most likely cause of this clinical finding?

. Femoral nerve palsy due to hyperflexion
. Obturator nerve palsy due to excessive abduction
. Sciatic nerve palsy due to hyperflexion
. Osteonecrosis of the femoral head
. Transient synovitis of the hip

Correct Answer & Explanation

. Femoral nerve palsy due to hyperflexion

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by excessive flexion of the hip which compresses the femoral nerve against the inguinal ligament. Clinical signs include an inability to actively extend the knee and an absent patellar reflex. The treatment is adjusting the harness to decrease the amount of flexion or temporarily removing it until nerve function recovers.

Question 3174

Topic: Pediatric Hip

A 12-year-old boy presents with right hip pain and an antalgic gait. He is diagnosed with a severe right slipped capital femoral epiphysis (SCFE). His weight is greater than the 95th percentile for his age. You plan to perform in situ pinning of the right hip. Which of the following is considered the strongest indication for prophylactic pinning of the contralateral asymptomatic hip?

. Male gender
. Age greater than 14 years
. Presence of an endocrine disorder (e.g., hypothyroidism)
. Severe slip angle on the affected side
. Presentation during the summer months

Correct Answer & Explanation

. Presence of an endocrine disorder (e.g., hypothyroidism)

Explanation

Prophylactic pinning of the contralateral hip is heavily debated, but universally accepted indications include the presence of an underlying endocrine disorder (e.g., hypothyroidism, renal osteodystrophy, panhypopituitarism) or a history of radiation therapy, as these patients have an exceptionally high risk of developing a contralateral slip. Other factors that lower the threshold for prophylactic pinning include an inability to reliably follow up, open triradiate cartilage, and young chronological age at presentation.

Question 3175

Topic: 4. Pediatrics
A 3-year-old girl is evaluated for progressive bowing of both lower extremities. She is at the 95th percentile for weight. Standing long-leg radiographs show significant genu varum with a metaphyseal-diaphyseal angle (Drennan angle) of 18 degrees bilaterally, as well as prominent medial metaphyseal beaking. What is the most appropriate initial management for this patient?
. Reassurance and annual observation
. High-dose Vitamin D supplementation
. Knee-ankle-foot orthoses (KAFOs) worn during weight-bearing
. Bilateral proximal tibial valgus-producing osteotomies
. Guided growth via medial tension band plating

Correct Answer & Explanation

. Knee-ankle-foot orthoses (KAFOs) worn during weight-bearing

Explanation

The patient's presentation and radiographic findings (metaphyseal-diaphyseal angle >16 degrees, medial metaphyseal beaking) are diagnostic of infantile Blount's disease (tibia vara). For a 3-year-old child (typically Langenskiöld stage I or II), the initial treatment consists of a trial of bracing with Knee-ankle-foot orthoses (KAFOs) worn during ambulation or waking hours. Surgical intervention (tibial osteotomy) is generally reserved for children who fail bracing or present after 4 years of age.

Question 3176

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy falls from the monkey bars and sustains a widely displaced, extension-type supracondylar humerus fracture. On presentation to the emergency department, his hand is pink and warm with brisk capillary refill, but the radial pulse is absent. Neurological examination reveals weakness in flexing the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. What is the most appropriate next step in management?

. Immediate open reduction and internal fixation
. Closed reduction and percutaneous pinning, followed by mandatory vascular exploration if the pulse remains absent
. Closed reduction and percutaneous pinning; if the hand remains pink and warm, observation is indicated
. CT angiography of the affected upper extremity
. Urgent vascular bypass grafting

Correct Answer & Explanation

. Closed reduction and percutaneous pinning; if the hand remains pink and warm, observation is indicated

Explanation

This patient has a "pink, pulseless" hand associated with a displaced supracondylar humerus fracture, along with an anterior interosseous nerve (AIN) palsy. The standard of care is urgent closed reduction and percutaneous pinning (CRPP). If the hand remains pink and well-perfused (warm with good capillary refill) after reduction, observation without vascular exploration is the accepted management, even if the radial pulse does not immediately return. Vascular exploration is indicated only if the hand becomes or remains white/ischemic after reduction.

Question 3177

Topic: 4. Pediatrics
An 8-year-old boy is diagnosed with Legg-Calvé-Perthes disease (LCPD). While evaluating his plain radiographs, you are assessing the "head-at-risk" signs described by Catterall, which are indicative of a poorer prognosis. Which of the following radiographic findings represents a Catterall "head-at-risk" sign?
. Medial subluxation of the femoral head
. Gage sign
. Central physeal arrest
. Narrowing of the medial joint space
. Hypertrophy of the greater trochanter

Correct Answer & Explanation

. Gage sign

Explanation

Catterall described five "head-at-risk" signs for Legg-Calvé-Perthes disease, which portend a poorer prognosis due to the increased risk of femoral head deformation. These include the Gage sign (a V-shaped radiolucency in the lateral epiphysis and adjacent metaphysis), lateral subluxation of the femoral head, calcification lateral to the epiphysis, horizontal growth plate, and metaphyseal cysts. Medial subluxation and central physeal arrest are not part of the Catterall risk criteria.

Question 3178

Topic: Pediatric Lower Extremity

A 2-week-old infant is undergoing serial casting for a severe right idiopathic clubfoot using the Ponseti method. After 5 weeks of weekly cast changes, the cavus, adductus, and varus deformities have been fully corrected, but there is residual equinus of 15 degrees. What is the most appropriate next step in management?

. Continue serial casting until the equinus is fully corrected
. Percutaneous Achilles tendon lengthening followed by a final cast for 3 weeks
. Posteromedial soft tissue release
. Immediate application of a Denis Browne bar and shoes
. Anterior tibial tendon transfer

Correct Answer & Explanation

. Percutaneous Achilles tendon lengthening followed by a final cast for 3 weeks

Explanation

In the Ponseti method, the components of the clubfoot deformity are corrected sequentially: Cavus, Adductus, Varus, and finally Equinus. Once the forefoot and midfoot are fully abducted (typically ~70 degrees) and the heel is in valgus, residual equinus is usually present and cannot be fully corrected with casting alone without causing a iatrogenic rocker-bottom foot deformity. The standard treatment for this residual equinus is a percutaneous Achilles tenotomy, followed by the application of a final long-leg cast with the foot in maximum dorsiflexion and abduction for 3 weeks.

Question 3179

Topic: 4. Pediatrics

A 6-year-old boy with spastic quadriplegic cerebral palsy (GMFCS Level V) is undergoing routine orthopedic surveillance. According to established hip surveillance guidelines for children with cerebral palsy, which of the following radiographic measurements is the most critical parameter to track for evaluating the risk and progression of hip displacement?

. Acetabular angle (Sharp's angle)
. Center-edge angle of Wiberg
. Neck-shaft angle
. Reimer's migration percentage
. Tonnis angle

Correct Answer & Explanation

. Reimer's migration percentage

Explanation

Reimer's migration percentage is the universally accepted standard measurement for monitoring hip displacement in children with cerebral palsy. It measures the percentage of the ossified femoral head that is laterally uncovered by the ossified lateral margin of the acetabulum. A migration percentage of >30% represents subluxation and is generally considered an indication for closer surveillance or possible surgical intervention (e.g., adductor/psoas lengthening or varus derotational osteotomy), especially in non-ambulatory children (GMFCS levels IV and V) who are at the highest risk.

Question 3180

Topic: Pediatric Hip

A 12-year-old boy who is at the 99th percentile for BMI presents with right thigh pain and an antalgic gait. Radiographs confirm a mild right slipped capital femoral epiphysis (SCFE). Which of the following is the most reliable radiographic predictor that this patient will subsequently develop a contralateral SCFE?

. Initial slip angle greater than 30 degrees
. Presence of a closed triradiate cartilage
. Open triradiate cartilage (modified Oxford bone age score less than 16)
. High alpha angle on the asymptomatic side
. Klein's line intersecting less than 20% of the epiphysis on the right

Correct Answer & Explanation

. Open triradiate cartilage (modified Oxford bone age score less than 16)

Explanation

The most significant predictor of a future contralateral SCFE is skeletal immaturity at the time of the initial presentation. An open triradiate cartilage, which corresponds to a modified Oxford bone age score of less than 16, indicates substantial remaining growth and a high risk of developing a contralateral slip. Therefore, prophylactic in situ pinning of the contralateral hip is strongly considered in these patients. Slip severity and BMI are factors, but the status of the triradiate cartilage is the most specific predictor of a subsequent contralateral slip.

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