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4. Pediatrics MCQs

Practice Set 167 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 3321

Topic: Pediatric Hip
A 9-year-old boy is diagnosed with Legg-Calvé-Perthes disease (LCPD) of the right hip. Radiographs in the fragmentation stage demonstrate collapse of more than 50% of the lateral pillar of the femoral head (Herring Lateral Pillar Class C). Which of the following factors in this patient is most strongly associated with a poor radiographic and functional outcome at skeletal maturity?
. Chronological age > 8 years at the onset of symptoms
. Presence of an adduction contracture on physical examination
. Body Mass Index (BMI) in the 85th percentile
. Male gender
. Concomitant ipsilateral knee pain

Correct Answer & Explanation

. Chronological age > 8 years at the onset of symptoms

Explanation

In Legg-Calvé-Perthes disease, the two most important prognostic factors are the age of the patient at the onset of symptoms and the extent of epiphyseal involvement/collapse (specifically lateral pillar height). An age of onset older than 8 years is universally associated with a poorer prognosis because there is less remaining growth potential for the femoral head to remodel before skeletal maturity. Lateral pillar class B or C also indicates a poor prognosis, but among the choices provided, age > 8 years is the primary unmodifiable demographic risk factor dictating a poor outcome.

Question 3322

Topic: 4. Pediatrics

A 6-year-old boy is brought to the emergency department after falling from monkey bars. Radiographs demonstrate a completely displaced extension-type supracondylar humerus fracture. On examination, the child's hand is pink and warm, but the radial pulse is absent. He is taken to the operating room for closed reduction and percutaneous pinning. Following anatomic reduction and secure pinning, the hand remains pink, warm, and well-perfused with brisk capillary refill, but the radial pulse remains absent. What is the most appropriate next step in management?

. Immediate open vascular exploration and repair
. Observe with close clinical monitoring
. CT angiography of the upper extremity
. Remove the pins and intentionally malreduce the fracture
. Intravenous heparin infusion

Correct Answer & Explanation

. Observe with close clinical monitoring

Explanation

In extension-type supracondylar humerus fractures, a pink, pulseless hand following a satisfactory closed reduction and percutaneous pinning is typically managed with observation. The collateral circulation is sufficient to maintain viability of the limb, and the radial pulse usually returns within a few days to weeks. Vascular exploration is indicated if the hand becomes white, cold, and poorly perfused (white and pulseless) after reduction.

Question 3323

Topic: 4. Pediatrics

A 6-week-old infant with developmental dysplasia of the hip is being treated with a Pavlik harness. During a routine follow-up visit at 2 weeks post-application, the mother notes that the child is no longer actively kicking the affected leg. Examination reveals decreased active extension of the knee on the affected side, though sensory responses appear intact. Which of the following is the most appropriate next step in management?

. Increase hip flexion by tightening the anterior straps
. Decrease hip flexion by loosening the anterior straps or discontinuing the harness
. Increase hip abduction by tightening the posterior straps
. Decrease hip abduction by loosening the posterior straps
. Proceed immediately to closed reduction and spica casting

Correct Answer & Explanation

. Decrease hip flexion by loosening the anterior straps or discontinuing the harness

Explanation

The clinical scenario describes a femoral nerve palsy, a known complication of Pavlik harness treatment caused by excessive hip flexion. The femoral nerve becomes compressed against the rim of the pelvis or inguinal ligament. The most appropriate immediate management is to decrease the amount of hip flexion by adjusting (loosening) the anterior straps, or if the palsy is profound, temporarily discontinuing the harness until spontaneous nerve recovery occurs.

Question 3324

Topic: Pediatric Hip

A 13-year-old obese boy presents with severe right groin pain after a minor slip. He is unable to bear weight on the affected limb, even with the assistance of crutches. Radiographs demonstrate a right slipped capital femoral epiphysis (SCFE) with a 45-degree slip angle. According to the Loder classification, what specific clinical factor in this patient is associated with the highest risk of developing avascular necrosis (AVN) of the femoral head?

. The severity of the slip angle on the frog-leg lateral radiograph
. The patient's body mass index (BMI) > 95th percentile
. The inability to bear weight on the affected limb
. The duration of symptoms prior to the acute event
. The degree of retroversion of the femoral neck

Correct Answer & Explanation

. The inability to bear weight on the affected limb

Explanation

The Loder classification defines an unstable SCFE as one in which the patient cannot bear weight, even with crutches, regardless of the duration of symptoms. Unstable slips have a significantly higher rate of avascular necrosis (up to 47%), whereas stable slips have a very low rate of AVN (<10%). While slip angle determines severity, the functional instability (inability to bear weight) is the most critical prognostic risk factor for AVN.

Question 3325

Topic: Pediatric Hip
An 8-year-old boy presents with a painless limp of 3 months duration. Radiographs show sclerosis and fragmentation of the femoral head consistent with Legg-Calvé-Perthes disease. According to the Herring lateral pillar classification, which of the following radiographic findings determines the poorest prognosis for subsequent femoral head sphericity?
. Involvement of the medial pillar
. Presence of the Gage sign
. >50% loss of lateral pillar height
. Presence of a subchondral crescent sign
. Metaphyseal cysts

Correct Answer & Explanation

. >50% loss of lateral pillar height

Explanation

The Herring lateral pillar classification is highly prognostic in Legg-Calvé-Perthes disease, evaluated during the fragmentation stage. Group A has no lateral pillar involvement. Group B maintains >50% of the lateral pillar height. Group C has <50% of lateral pillar height maintained. Group C (>50% loss of height) has the poorest prognosis and highest likelihood of developing an aspherical incongruent joint. Age >8 years at onset is also a poor prognostic indicator.

Question 3326

Topic: Pediatric Lower Extremity
A 3.5-year-old boy who was successfully treated in infancy for bilateral idiopathic clubfoot using the Ponseti method presents with a recurrent deformity. On physical examination, he demonstrates dynamic supination of the foot during the swing phase of gait. Passive range of motion demonstrates that the foot is fully correctable without fixed equinus or cavus. What is the most appropriate next step in management?
. Repeat percutaneous Achilles tenotomy
. Tibialis anterior tendon transfer to the lateral cuneiform
. Split anterior tibial tendon transfer (SPLATT)
. Lateral column lengthening (calcaneal osteotomy)
. Triple arthrodesis

Correct Answer & Explanation

. Tibialis anterior tendon transfer to the lateral cuneiform

Explanation

Dynamic supination in a previously treated clubfoot that remains passively correctable is a common sign of relapse in toddlers. It is driven by the strong pull of the tibialis anterior muscle acting without adequate antagonism. The definitive treatment for this specific dynamic deformity in a child over 2.5 to 3 years old is a full tibialis anterior tendon transfer (TATT) to the lateral cuneiform. If residual rigid equinus or cavus were present, a brief period of serial casting would precede the transfer.

Question 3327

Topic: 4. Pediatrics

A 2-year-old girl is evaluated for multiple recurrent fractures after minimal trauma. On clinical examination, she has blue sclerae and evidence of dentinogenesis imperfecta. Genetic testing confirms a mutation in the COL1A1 gene. The pathophysiologic basis of her condition primarily involves a quantitative or qualitative defect in the synthesis of which of the following?

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

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta (OI) is primarily caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, which encode the alpha-1 and alpha-2 chains of type I collagen. Type I collagen is the major structural protein of bone, dentin, and sclerae, which explains the clinical triad of brittle bones, dentinogenesis imperfecta, and blue sclerae. FGFR3 is associated with achondroplasia, Type II collagen with spondyloepiphyseal dysplasia, and COMP with pseudoachondroplasia.

Question 3328

Topic: 4. Pediatrics
A 4-year-old boy with a BMI in the 99th percentile presents with progressively worsening severe bowing of his left leg. Radiographs demonstrate an abrupt angulation at the proximal medial tibial metaphysis with a metaphyseal-diaphyseal angle (Drennan angle) of 18 degrees. The radiographic appearance is consistent with a Langenskiöld stage III lesion. Observation over the last year has shown clear progression. What is the most appropriate surgical management?
. Observation until skeletal maturity
. Full-time use of a knee-ankle-foot orthosis (KAFO)
. Proximal tibial valgus osteotomy
. Hemiepiphysiodesis of the lateral proximal tibia
. Medial plateau elevation osteotomy alone

Correct Answer & Explanation

. Proximal tibial valgus osteotomy

Explanation

The patient has infantile Blount disease (tibia vara) that is progressive. A metaphyseal-diaphyseal angle >16 degrees is highly predictive of progression. Once a child is older than 3 to 4 years and presents with an advanced Langenskiöld stage (Stage III or higher), bracing is generally ineffective. The standard of care is a proximal tibial valgus-derotation osteotomy to realign the mechanical axis, unload the medial physis, and prevent permanent physeal bar formation.

Question 3329

Topic: 4. Pediatrics

A 6-week-old female is currently being treated with a Pavlik harness for a dislocated left hip. During a follow-up visit after 2 weeks of treatment, the mother reports that the infant is not kicking her left leg as vigorously as the right. Physical examination reveals decreased active extension of the left knee, while ankle and toe movements remain symmetric and normal. What is the most likely cause of this physical finding?

. Ischemic necrosis of the femoral head
. Femoral nerve palsy from excessive hip flexion
. Obturator nerve palsy from excessive hip abduction
. Sciatic nerve palsy from excessive hip extension
. Inferior dislocation of the left hip joint

Correct Answer & Explanation

. Femoral nerve palsy from excessive hip flexion

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically resulting from hyperflexion of the hip. It presents as decreased active knee extension (quadriceps weakness). The appropriate management involves temporarily loosening the anterior straps to reduce hip flexion or discontinuing the harness until nerve function fully recovers, which is usually spontaneous.

Question 3330

Topic: Pediatric Hip

A 12-year-old obese boy presents to the emergency department with acute left hip pain and an inability to bear weight after a minor fall 2 days ago. Radiographs demonstrate a severe, displaced slipped capital femoral epiphysis (SCFE) on the left side. He is completely unable to bear weight even with crutches. According to the Loder classification, this specific presentation is associated with a significantly increased risk of which of the following complications?

. Chondrolysis
. Contralateral slipped capital femoral epiphysis
. Avascular necrosis (AVN) of the femoral head
. Early-onset femoroacetabular impingement (FAI)
. Proximal femoral growth arrest

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

The Loder classification categorizes SCFE into stable (patient can bear weight) and unstable (patient cannot bear weight, even with crutches). Unstable SCFE has a substantially higher risk of avascular necrosis (AVN), historically reported to be as high as 47%, compared to nearly 0% in stable SCFE.

Question 3331

Topic: 4. Pediatrics

A 6-year-old boy falls from the monkey bars and sustains a widely displaced, extension-type supracondylar humerus fracture. Upon initial presentation, his hand is pink and warm, with a capillary refill of less than 2 seconds, but the radial pulse is not palpable. He undergoes immediate closed reduction and percutaneous pinning. Post-operatively in the recovery room, his hand remains pink and warm, but the radial pulse is still absent. What is the most appropriate next step in management?

. Immediate vascular surgery consultation for brachial artery exploration
. Observation and admission for close compartment and neurovascular monitoring
. Emergent upper extremity arteriography
. Removal of the percutaneous pins and hyperflexion of the elbow
. Administration of intravenous heparin

Correct Answer & Explanation

. Observation and admission for close compartment and neurovascular monitoring

Explanation

The patient has a 'pink, pulseless' hand after reduction and pinning of a supracondylar fracture. The standard of care in this scenario is careful observation and monitoring. Collateral circulation in the pediatric elbow is generally sufficient to perfuse the hand even if the brachial artery is in spasm or injured. Vascular exploration is indicated if the hand becomes pale, cold, and poorly perfused (a 'white, pulseless' hand) after closed reduction.

Question 3332

Topic: Pediatric Lower Extremity
A 4-year-old boy treated with the Ponseti method for idiopathic right clubfoot presents with relapsed deformity. The parents report he has been compliant with the bracing protocol. Examination reveals dynamic supination of the foot during the swing phase of gait. Passive range of motion shows completely correctable hindfoot varus and forefoot adduction. Which of the following is the most appropriate surgical intervention?
. Posteromedial release
. Split anterior tibial tendon transfer (SPLATT)
. Full anterior tibial tendon transfer to the lateral cuneiform
. Calcaneal sliding osteotomy
. Talonavicular arthrodesis

Correct Answer & Explanation

. Full anterior tibial tendon transfer to the lateral cuneiform

Explanation

Dynamic supination during the swing phase in a relapsed clubfoot treated previously with Ponseti casting is typically caused by a strong anterior tibial muscle combined with weak everters. The standard of care for this specific dynamic relapse is a full transfer of the anterior tibial tendon (TATT) to the lateral cuneiform (or cuboid). This procedure successfully rebalances the foot to prevent recurrent supination.

Question 3333

Topic: 4. Pediatrics
A 13-year-old boy presents with severe ankle pain after an external rotation injury while skateboarding. Radiographs reveal a Salter-Harris III intra-articular avulsion fracture of the anterolateral aspect of the distal tibial epiphysis (Tillaux fracture). The fracture pattern observed is directly related to the normal physiological pattern of physeal closure in the distal tibia. In what sequence does the distal tibial physis normally close?
. Central, medial, lateral
. Lateral, central, medial
. Medial, central, lateral
. Anterior, posterior, medial
. Posterior, central, anterior

Correct Answer & Explanation

. Medial, central, lateral

Explanation

The distal tibial physis typically closes over an 18-month period, beginning centrally, then proceeding medially, and finally closing laterally. Because the anterolateral physis is the last to close, it remains susceptible to avulsion forces from the anterior inferior tibiofibular ligament (AITFL) during an external rotation injury, leading to the classic Tillaux fracture in adolescents.

Question 3334

Topic: Pediatric Hip
An 8-year-old boy presents with a 4-month history of a painless limp. Examination shows restricted hip abduction and internal rotation. AP and frog-leg lateral pelvis radiographs show sclerosis, flattening, and fragmentation of the right femoral head. Which of the following clinical or radiographic factors indicates the worst prognosis for this patient?
. Age of onset at 5 years
. Involvement of less than 50% of the femoral head
. Maintenance of lateral pillar height >50%
. Loss of containment with lateral subluxation of the femoral head
. Decreased hip internal rotation of 10 degrees

Correct Answer & Explanation

. Loss of containment with lateral subluxation of the femoral head

Explanation

In Legg-Calvé-Perthes disease, a poor prognosis is associated with older age at onset (typically >8 years), extensive epiphyseal involvement, loss of lateral pillar height (Herring B/C or C), and signs of a 'head at risk'. Loss of containment with lateral subluxation (extrusion) is a severe 'head at risk' sign that subjects the softened femoral head to deforming mechanical forces against the lateral acetabular rim, leading to permanent aspherical deformity and early osteoarthritis.

Question 3335

Topic: Pediatric Hip

A 12-year-old obese boy presents with sudden inability to bear weight on the left leg after a minor fall. He had been experiencing vague left thigh pain for 3 weeks prior to the fall. On physical examination, the left hip is held in external rotation and he is entirely unable to ambulate even with crutches. Radiographs show a severe posterior and inferior displacement of the proximal femoral epiphysis. He undergoes urgent in-situ pinning with a single cannulated screw. Based on his presentation, which of the following complications is he at the highest risk for developing compared to a patient who is able to bear weight?

. Chondrolysis
. Avascular necrosis
. Contralateral slip
. Femoroacetabular impingement
. Screw cutout

Correct Answer & Explanation

. Avascular necrosis

Explanation

The patient has an unstable Slipped Capital Femoral Epiphysis (SCFE). The Loder classification dictates that an unstable SCFE is defined by the inability to bear weight, even with assistive devices. The distinction is critical because unstable SCFE has a significantly higher risk of avascular necrosis (AVN), reported to be between 10% and 47%, compared to nearly 0% in stable SCFE. Chondrolysis is typically associated with unrecognized pin penetration into the joint space. While femoroacetabular impingement is a known long-term sequela of SCFE deformity, AVN is the specific, devastating complication most closely linked to the unstable nature of the slip.

Question 3336

Topic: Pediatric Upper Extremity & Spine
A 5-year-old girl falls from monkey bars and sustains a Gartland type III supracondylar humerus fracture. On presentation to the emergency department, her hand is pink and well-perfused with a capillary refill of 2 seconds, but the radial pulse is not palpable. She undergoes emergent closed reduction and percutaneous pinning. In the recovery room, her hand remains pink and warm, but the radial pulse remains absent on palpation and Doppler ultrasound. What is the most appropriate next step in management?
. Immediate exploration of the brachial artery
. Computed tomography angiography of the upper extremity
. Observation with close clinical monitoring
. Immediate removal of pins and open reduction
. Forearm fasciotomy

Correct Answer & Explanation

. Observation with close clinical monitoring

Explanation

The management of the 'pulseless, pink hand' following a pediatric supracondylar humerus fracture is observation. If the hand remains well-perfused (pink, warm, capillary refill < 2 seconds) after closed reduction and pinning, the collateral circulation is sufficient, and arterial exploration or advanced imaging is not indicated. The brachial artery may be in spasm or have a small intimal tear that will often resolve or remodel without ischemic consequence. Arterial exploration is strictly indicated if the hand is 'white and pulseless' (ischemic) after reduction and pinning.

Question 3337

Topic: Pediatric Hip

A 4-week-old female infant is being treated with a Pavlik harness for developmental dysplasia of the left hip (DDH). At her 1-week follow-up visit, the mother reports that the infant is no longer kicking her left leg. On examination, the hip remains successfully reduced, but there is absent active extension of the left knee. Sensation to a light pinprick on the anterior thigh appears diminished compared to the contralateral side. What is the most appropriate management of this complication?

. Adjust the anterior strap to increase hip flexion by 10 degrees
. Adjust the posterior strap to increase hip abduction
. Discontinue the harness completely
. Switch to a rigid hip spica cast immediately
. Reassure the mother and observe without modifying the harness

Correct Answer & Explanation

. Discontinue the harness completely

Explanation

The infant has developed a femoral nerve palsy, a known complication of Pavlik harness treatment. It is primarily caused by excessive hyperflexion of the hip, which compresses the femoral nerve against the inguinal ligament. The standard of care when a femoral nerve palsy is identified is to discontinue the Pavlik harness immediately to prevent permanent nerve damage. Once the harness is removed, motor function typically recovers over days to a few weeks. After full recovery of quadriceps function, an alternative treatment method, such as a rigid abduction orthosis or careful reinstitution of the harness with less flexion, can be considered.

Question 3338

Topic: 4. Pediatrics

A 7-year-old boy with spastic quadriplegic cerebral palsy (GMFCS Level IV) is evaluated for bilateral hip pain that interferes with seating and perineal hygiene. An anteroposterior pelvic radiograph demonstrates a right hip Reimers migration percentage of 55%, a broken Shenton's line, and an acetabular index of 35 degrees. The left hip shows a migration percentage of 20% with normal acetabular parameters. What is the most appropriate surgical management for the right hip?

. Adductor and iliopsoas tenotomies alone
. Varus derotational osteotomy (VDRO) of the proximal femur alone
. VDRO of the proximal femur combined with a pelvic osteotomy
. Proximal femoral resection arthroplasty (Castle procedure)
. Open reduction and spica casting

Correct Answer & Explanation

. VDRO of the proximal femur combined with a pelvic osteotomy

Explanation

In children with cerebral palsy, the management of hip displacement depends on the Reimers migration percentage (MP) and the presence of acetabular dysplasia. An MP > 50% combined with a high acetabular index (> 25-30 degrees) indicates significant subluxation and bony dysplasia. Soft tissue releases alone are indicated for early displacement (MP < 30%) in younger children. A VDRO alone is appropriate for moderate displacement (MP 30-40%) without severe acetabular dysplasia. For an MP of 55% with an acetabular index of 35 degrees, a combined procedure (proximal femoral VDRO and a volume-reducing pelvic osteotomy, such as a Dega or San Diego osteotomy) is required to stabilize the hip and correct the dysplasia. A salvage procedure (Castle) is reserved for severe, painful, un-reconstructable dislocated hips in older, non-ambulatory patients.

Question 3339

Topic: Pediatric Hip

A 12-year-old boy with chronic kidney disease presents with a stable slipped capital femoral epiphysis (SCFE) on the left. Which of the following is the strongest indication for prophylactic pinning of the contralateral right hip?

. Age younger than 10 years
. Presence of renal osteodystrophy
. Severe obesity with BMI > 95th percentile
. Male gender
. Open triradiate cartilage

Correct Answer & Explanation

. Presence of renal osteodystrophy

Explanation

Patients with endocrine disorders or renal osteodystrophy are at a highly elevated risk of bilateral SCFE. Prophylactic pinning of the contralateral hip is strongly recommended in these patients due to the high incidence of subsequent slip.

Question 3340

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 but the radial pulse is absent on Doppler. What is the most appropriate next step in management?

. Immediate vascular exploration
. Observation with ward monitoring
. Removal of pins and hyperflexion of the elbow
. Prophylactic forearm fasciotomy
. CT angiography

Correct Answer & Explanation

. Observation with ward monitoring

Explanation

A "pink, pulseless" hand after reduction of a supracondylar humerus fracture indicates adequate collateral perfusion. The standard of care is close observation and admission, as the pulse often returns within 24 to 48 hours without surgical exploration.

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