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4. Pediatrics MCQs

Practice Set 180 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 3581

Topic: Pediatric Hip

When evaluating a patient with Legg-Calve-Perthes disease, which of the following radiographic or clinical findings is considered the most reliable predictor of a poor long-term outcome regarding hip joint congruency?

. Age of onset at 5 years
. Loss of hip internal rotation on examination
. A subchondral fracture line (Crescent sign) involving 30% of the head
. Lateral pillar involvement greater than 50% height collapse
. Male gender

Correct Answer & Explanation

. Lateral pillar involvement greater than 50% height collapse

Explanation

The Herring lateral pillar classification is highly prognostic in Legg-Calve-Perthes disease. Collapse of the lateral pillar greater than 50% (Group C) predicts severe deformity and a poor long-term outcome.

Question 3582

Topic: 4. Pediatrics

A 2-year-old child presents with a history of recurrent fractures after minimal trauma, blue sclerae, and dentinogenesis imperfecta. Genetic testing is ordered to confirm the suspected diagnosis. A defect in the gene coding for which of the following is most likely to be found?

. Type I collagen
. Type II collagen
. Type IV collagen
. Fibroblast growth factor receptor 3 (FGFR3)
. Cartilage oligomeric matrix protein (COMP)

Correct Answer & Explanation

. Type I collagen

Explanation

The clinical presentation is classic for Osteogenesis Imperfecta (OI), which is primarily caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes. These genes are responsible for the synthesis of Type I collagen.

Question 3583

Topic: 4. Pediatrics

A 9-month-old infant, who does not yet walk, is brought to the emergency department for crying when his diaper is changed. Radiographs reveal a spiral fracture of the left femoral diaphysis. The parents state the child caught his leg in the crib slats. What is the most critical initial step in management?

. Immediate application of a one-and-a-half hip spica cast
. Admission, skeletal survey, and consultation with child protective services
. Surgical fixation with flexible intramedullary nails
. Application of a Pavlik harness to stabilize the femur
. Referral for urgent genetic testing for metabolic bone disease

Correct Answer & Explanation

. Admission, skeletal survey, and consultation with child protective services

Explanation

A diaphyseal femur fracture in a non-ambulatory infant is highly suspicious for non-accidental trauma (child abuse). The immediate priority, alongside pain control, is securing the child's safety, consulting child protective services, and obtaining a skeletal survey.

Question 3584

Topic: 4. Pediatrics

A 4-year-old girl with spastic quadriplegic cerebral palsy (GMFCS Level V) is evaluated in a routine hip surveillance clinic. Anteroposterior pelvis radiographs reveal a Reimers migration percentage of 45% bilaterally. What is the most appropriate surgical intervention to prevent painful hip dislocation?

. Continued radiographic observation every 6 months
. Bilateral varus derotational osteotomies (VDRO) with pelvic osteotomies
. Isolated bilateral adductor and iliopsoas tenotomies
. Botulinum toxin A injections to the hip adductors
. Proximal femoral resection (Castle procedure)

Correct Answer & Explanation

. Bilateral varus derotational osteotomies (VDRO) with pelvic osteotomies

Explanation

In children with cerebral palsy, a hip migration percentage greater than 40% usually indicates established dysplasia that will not respond to soft tissue releases alone. Bony reconstruction with VDRO and often a concurrent pelvic osteotomy is required.

Question 3585

Topic: Pediatric Hip

A 4-week-old girl is being treated for developmental dysplasia of the hip with a Pavlik harness. During a follow-up visit, the mother notes that the child is no longer kicking her right leg as much. Examination reveals an inability to actively extend the right knee, though sensation appears intact. What is the most appropriate next step in management?

. Adjust the anterior straps to increase hip flexion
. Adjust the posterior straps to increase hip abduction
. Remove the Pavlik harness and observe for recovery
. Transition immediately to a rigid hip abduction orthosis
. Perform an emergent ultrasound to rule out a deep vein thrombosis

Correct Answer & Explanation

. Remove the Pavlik harness and observe for recovery

Explanation

The patient has developed a femoral nerve palsy, a known complication of excessive hip flexion in a Pavlik harness. The most appropriate management is to temporarily remove the harness to allow the nerve to recover before resuming treatment.

Question 3586

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy sustains a completely displaced extension-type supracondylar humerus fracture. On presentation, the hand is pink, warm, and has brisk capillary refill, but the radial pulse is absent on palpation and Doppler. What is the most appropriate next step in management?

. Immediate CT angiography of the upper extremity
. Open exploration of the brachial artery in the emergency department
. Urgent closed reduction and percutaneous pinning
. Emergent forearm fasciotomies
. Observation and repeat vascular examination in 24 hours

Correct Answer & Explanation

. Urgent closed reduction and percutaneous pinning

Explanation

A pulseless but well-perfused (pink) hand associated with a supracondylar humerus fracture should initially be managed with urgent closed reduction and percutaneous pinning. Vascular exploration is only indicated if the hand becomes poorly perfused (white/ischemic) after reduction.

Question 3587

Topic: Pediatric Lower Extremity

During the initial application of the Ponseti method for a rigid idiopathic clubfoot in a 2-week-old infant, which of the following maneuvers is the essential first step in correcting the deformity?

. Pronation of the forefoot to correct the cavus
. Elevation of the first ray to correct the cavus
. Abduction of the midfoot with counter-pressure on the calcaneus
. Immediate percutaneous Achilles tenotomy to correct equinus
. Forced dorsiflexion of the midfoot to stretch the plantar fascia

Correct Answer & Explanation

. Elevation of the first ray to correct the cavus

Explanation

The first step in the Ponseti method is correcting the cavus deformity by supinating the forefoot (elevating the first ray) in alignment with the hindfoot. Pronating the forefoot will worsen the cavus and block subsequent correction.

Question 3588

Topic: 4. Pediatrics

A 2-year-old boy presents with anterolateral bowing of the tibia. Radiographs demonstrate a diaphyseal narrowing with a sclerotic medullary canal. Which of the following conditions is most strongly associated with this clinical presentation?

. Osteogenesis imperfecta
. Achondroplasia
. Neurofibromatosis type 1
. Fibrous dysplasia
. Cleidocranial dysplasia

Correct Answer & Explanation

. Neurofibromatosis type 1

Explanation

Anterolateral bowing of the tibia with diaphyseal narrowing is characteristic of congenital pseudarthrosis of the tibia (CPT). CPT is highly associated with Neurofibromatosis type 1 (NF1), which is present in over 50% of these patients.

Question 3589

Topic: Pediatric Hip

A 13-year-old boy is diagnosed with a unilateral slipped capital femoral epiphysis (SCFE) and undergoes in-situ screw fixation. Prophylactic pinning of the asymptomatic contralateral hip is most strongly indicated if the patient has a history of which of the following?

. Type 1 diabetes mellitus
. Hypothyroidism
. Asthma treated with intermittent corticosteroids
. Attention-deficit/hyperactivity disorder
. Idiopathic short stature

Correct Answer & Explanation

. Hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in SCFE is indicated in patients with endocrine disorders, such as hypothyroidism or renal osteodystrophy. These conditions significantly increase the risk of developing a subsequent contralateral slip.

Question 3590

Topic: 4. Pediatrics

According to the Gross Motor Function Classification System (GMFCS), what is the recommended hip surveillance radiographic interval for a 6-year-old child with cerebral palsy classified as GMFCS level V?

. AP pelvis radiograph every 3 years
. AP pelvis radiograph every 2 years
. AP pelvis radiograph every 6 to 12 months
. Screening only if the patient becomes symptomatic
. Annual MRI of the hips

Correct Answer & Explanation

. AP pelvis radiograph every 6 to 12 months

Explanation

Children with GMFCS level IV and V cerebral palsy have the highest risk of progressive hip displacement. Standard hip surveillance protocols recommend an AP pelvis radiograph every 6 to 12 months for this high-risk group.

Question 3591

Topic: Pediatric Hip

A 12-year-old girl with a slipped capital femoral epiphysis undergoes in-situ pinning. Six months later, she presents with severe hip stiffness and a painful limp. Radiographs demonstrate significant concentric joint space narrowing without focal collapse of the femoral head. What is the most likely underlying cause of this complication?

. Avascular necrosis of the femoral head
. Unrecognized intra-articular hardware penetration
. Natural progression of the slip
. Femoroacetabular impingement
. Post-infectious inflammatory arthritis

Correct Answer & Explanation

. Unrecognized intra-articular hardware penetration

Explanation

Concentric joint space narrowing following SCFE fixation is the hallmark of chondrolysis. The most common iatrogenic cause of chondrolysis is unrecognized penetration of the fixation screw into the hip joint space.

Question 3592

Topic: 4. Pediatrics

A 3-year-old boy presents with bilateral varus bowing of his legs. Radiographs reveal medial metaphyseal beaking at the proximal tibia. Which of the following radiographic measurements indicates the highest risk for progression of infantile Blount disease?

. Metaphyseal-diaphyseal angle greater than 16 degrees
. Tibiofemoral angle of 10 degrees varus
. Mechanical axis deviation of 1 cm medial to knee center
. Physeal-diaphyseal angle less than 10 degrees
. Anterior distal femoral angle of 80 degrees

Correct Answer & Explanation

. Metaphyseal-diaphyseal angle greater than 16 degrees

Explanation

The metaphyseal-diaphyseal angle (Drennan angle) is critical in evaluating infantile tibia vara. An angle greater than 16 degrees indicates a high likelihood of progression to true infantile Blount disease rather than physiologic bowing.

Question 3593

Topic: 4. Pediatrics
A 14-year-old girl sustains a juvenile Tillaux fracture of the ankle during a soccer match. What is the pathomechanics responsible for this specific fracture pattern?
. Avulsion of the anteromedial distal tibia by the deltoid ligament
. Avulsion of the anterolateral distal tibial epiphysis by the anterior inferior tibiofibular ligament
. Impaction of the talus into the tibial plafond during axial loading
. Shear force from the fibula causing a medial malleolus fracture
. Avulsion of the posterior malleolus by the posterior inferior tibiofibular ligament

Correct Answer & Explanation

. Avulsion of the anterolateral distal tibial epiphysis by the anterior inferior tibiofibular ligament

Explanation

A Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. It is caused by an external rotation force leading to an avulsion by the anterior inferior tibiofibular ligament (AITFL) as the medial physis has already closed.

Question 3594

Topic: 4. Pediatrics

A 6-year-old boy presents with a painless clicking and snapping in his lateral knee. MRI demonstrates a thickened lateral meniscus extending into the intercondylar notch with absent posterior meniscotibial attachments. What is the diagnosis?

. Complete discoid meniscus
. Incomplete discoid meniscus
. Wrisberg variant discoid meniscus
. Meniscal cyst
. Congenital popliteus tendon subluxation

Correct Answer & Explanation

. Wrisberg variant discoid meniscus

Explanation

The Wrisberg variant of a discoid meniscus is characterized by an abnormal or absent posterior meniscotibial attachment (coronary ligament), leaving only the ligament of Wrisberg. This hypermobility causes the classic 'snapping knee' syndrome.

Question 3595

Topic: Pediatric Hip
Figure 10 shows the AP pelvis radiograph of an 8-year-old boy with a persistent limp. He is diagnosed with Legg-Calvé-Perthes disease. Which of the following factors represents the most significant prognostic indicator for long-term hip outcome in this patient?
. Gender of the patient
. Age at the onset of disease
. Presence of a positive Trendelenburg sign
. Body mass index
. Duration of conservative treatment prior to diagnosis

Correct Answer & Explanation

. Age at the onset of disease

Explanation

Age at the onset of Legg-Calvé-Perthes disease is the most critical clinical prognostic factor. Patients who develop the disease after age 8 have a significantly worse prognosis due to having less remaining growth for femoral head remodeling.

Question 3596

Topic: 4. Pediatrics

A 15-year-old boy with achondroplasia presents with progressively worsening lower extremity radicular pain and weakness triggered by walking. What is the primary anatomical cause of his spinal symptoms?

. Hypertrophy of the ligamentum flavum
. Severe rotatory kyphoscoliosis
. Decreased interpedicular distance
. Spondylolisthesis of L5 on S1
. Atlantoaxial instability

Correct Answer & Explanation

. Decreased interpedicular distance

Explanation

Patients with achondroplasia have a mutation in the FGFR3 gene resulting in defective endochondral ossification. In the spine, this manifests as shortened pedicles and a narrowed interpedicular distance, leading to severe congenital spinal stenosis.

Question 3597

Topic: Pediatric Hip

An 18-month-old girl who recently started walking presents with a painless limp and a positive Galeazzi sign on the left. Radiographs confirm a completely dislocated left hip with a dysplastic acetabulum. What is the most appropriate management?

. Application of a Pavlik harness
. Closed reduction and spica casting
. Open reduction with possible pelvic and/or femoral osteotomy
. Observation and physical therapy
. Varus derotational osteotomy alone without opening the joint

Correct Answer & Explanation

. Open reduction with possible pelvic and/or femoral osteotomy

Explanation

In a child over 18 months of age with developmental dysplasia of the hip, conservative treatments and isolated closed reductions have high failure rates. Open reduction, often combined with a pelvic or femoral osteotomy to correct the dysplasia, is the standard of care.

Question 3598

Topic: Pediatric Hip

A 3-month-old girl with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During her first follow-up visit, the parents report that she has stopped kicking her left leg. On physical examination, the infant exhibits a lack of active knee extension on the left side, but withdrawal to pain is intact. What is the most appropriate next step in management?

. Adjust the anterior straps to increase hip flexion
. Remove the harness and admit for closed reduction and spica casting
. Decrease hip flexion by adjusting the anterior straps or temporarily discontinue the harness
. Switch to a rigid abduction orthosis (e.g., Ilfeld splint)
. Obtain an urgent ultrasound to evaluate for deep vein thrombosis

Correct Answer & Explanation

. Decrease hip flexion by adjusting the anterior straps or temporarily discontinue the harness

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment and is caused by hyperflexion of the hip. Management requires immediate reduction of hip flexion by adjusting the anterior straps or temporarily discontinuing the harness until active quadriceps function returns.

Question 3599

Topic: 4. Pediatrics
A 30-month-old boy is evaluated for worsening unilateral bowing of the left leg. Radiographs demonstrate a metaphyseal-diaphyseal angle (Drennan angle) of 18 degrees with focal medial metaphyseal beaking, consistent with infantile Blount disease (Langenskiöld stage II). What is the most appropriate initial management?
. Observation and reassurance
. Daytime or full-time use of a knee-ankle-foot orthosis (KAFO)
. Proximal tibial valgus-derotation osteotomy
. Medial hemiepiphysiodesis
. Guided growth using lateral tension band plates

Correct Answer & Explanation

. Daytime or full-time use of a knee-ankle-foot orthosis (KAFO)

Explanation

In a child younger than 3 years with infantile Blount disease (Langenskiöld stage I or II), initial treatment consists of using a knee-ankle-foot orthosis (KAFO) during weight-bearing activities. Surgical intervention is typically reserved for children older than 4 years, those who fail conservative management, or those presenting with advanced stages (III and above).

Question 3600

Topic: Pediatric Hip

A 13-year-old girl with a history of a slipped capital femoral epiphysis (SCFE) treated with in-situ pinning 6 months ago presents with worsening hip stiffness and pain. Physical examination reveals a significant global loss of hip motion. Radiographs are shown in Figure 10.

Assuming the radiograph demonstrates diffuse joint space narrowing without focal collapse of the femoral head, what is the most likely iatrogenic cause of this patient's current condition?

. Aggressive physical therapy initiated immediately postoperatively
. Unrecognized hardware penetration into the joint
. Failure to perform a capsulotomy during the index procedure
. Use of a fully threaded screw instead of a partially threaded screw
. Placement of the screw in the anterior half of the femoral head

Correct Answer & Explanation

. Unrecognized hardware penetration into the joint

Explanation

Global loss of motion and diffuse joint space narrowing after SCFE fixation is the hallmark of chondrolysis. The most common iatrogenic cause of chondrolysis in this setting is unrecognized pin or screw penetration into the hip joint, necessitating prompt hardware removal.

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