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4. Pediatrics MCQs

Practice Set 108 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 2141

Topic: 4. Pediatrics

An 8-week-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). The mother notes that the child has stopped kicking the leg on the affected side. On examination, the quadriceps are weak and the patellar reflex is diminished. This complication is most likely due to:

. Excessive hip abduction in the harness
. Excessive hip flexion in the harness
. Insufficient hip flexion in the harness
. Excessive knee flexion in the harness
. Avascular necrosis of the femoral head

Correct Answer & Explanation

. Excessive hip flexion in the harness

Explanation

Femoral nerve palsy in a Pavlik harness is typically caused by excessive hip flexion, which stretches or compresses the femoral nerve. The management involves adjusting the harness to decrease the amount of flexion or giving the infant a temporary break from the harness until neurologic function returns. Excessive abduction is associated with avascular necrosis (AVN) of the femoral head.

Question 2142

Topic: Pediatric Hip

According to the Loder classification, an unstable Slipped Capital Femoral Epiphysis (SCFE) is defined by which of the following clinical criteria, and what is the primary risk associated with it?

. Displacement greater than 50%; high risk of chondrolysis
. Inability to ambulate even with crutches; high risk of avascular necrosis
. Duration of symptoms less than 3 weeks; high risk of contralateral slip
. Presence of an effusion on ultrasound; high risk of septic arthritis
. Slip angle greater than 60 degrees; high risk of osteoarthritis

Correct Answer & Explanation

. Inability to ambulate even with crutches; high risk of avascular necrosis

Explanation

The Loder classification divides SCFE into stable and unstable categories based strictly on the clinical ability of the patient to bear weight (with or without crutches). An unstable SCFE means the patient cannot bear weight. This is highly clinically relevant because unstable SCFEs carry a substantially higher risk of developing avascular necrosis (AVN) of the femoral head (often approaching 50%).

Question 2143

Topic: Pediatric Hip

During the surgical treatment of a severe, unstable slipped capital femoral epiphysis (SCFE) using in situ pinning, the surgeon performs an anterior capsulotomy of the hip. What is the primary biomechanical or physiologic benefit of this adjunctive procedure?

. Reduces the risk of postoperative chondrolysis
. Reduces intracapsular pressure and the risk of avascular necrosis (AVN)
. Improves direct visualization to achieve anatomical reduction
. Facilitates the placement of a completely intra-epiphyseal screw
. Prevents the future development of cam-type femoroacetabular impingement

Correct Answer & Explanation

. Reduces intracapsular pressure and the risk of avascular necrosis (AVN)

Explanation

In an unstable SCFE, there is often an intracapsular hematoma that raises the pressure within the joint space. This increased pressure can compromise the tenuous retinacular vessels supplying the femoral epiphysis, increasing the risk of avascular necrosis (AVN). An anterior capsulotomy decompresses the hematoma, lowering intracapsular pressure and mitigating the risk of AVN.

Question 2144

Topic: 4. Pediatrics

A 4-month-old infant is being treated for developmental dysplasia of the hip (DDH) using a Pavlik harness. During a routine follow-up, the parents report the infant is not moving the affected leg as much. Physical examination reveals decreased active extension of the knee on the treated side, while hip movements and ankle movements appear normal. What is the most likely cause of this complication?

. Excessive hip abduction in the harness
. Excessive hip flexion in the harness
. Avascular necrosis of the femoral head
. Transient synovitis of the hip
. Inadequate hip flexion in the harness

Correct Answer & Explanation

. Excessive hip flexion in the harness

Explanation

Decreased active knee extension in a child wearing a Pavlik harness is highly indicative of a femoral nerve palsy. This iatrogenic complication is caused by excessive flexion of the hip in the harness, which stretches or compresses the femoral nerve against the inguinal ligament. The correct management is to temporarily loosen or remove the anterior (flexion) straps until nerve function recovers. Excessive abduction, conversely, increases the risk of avascular necrosis (AVN).

Question 2145

Topic: Pediatric Hip

A 6-week-old female is treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the 2-week follow-up, the mother notes the child is not kicking the left leg. Examination reveals absent active knee extension on the left. The hips are positioned in 120 degrees of flexion. What is the most likely cause of this finding?

. Obturator nerve palsy due to excessive abduction
. Femoral nerve palsy due to hyperflexion
. Sciatic nerve palsy due to excessive adduction
. Septic arthritis of the hip
. Transient synovitis from harness adjustments

Correct Answer & Explanation

. Femoral nerve palsy due to hyperflexion

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by hyperflexion of the hips (usually >100-110 degrees), which compresses the femoral nerve against the inguinal ligament. The treatment is temporary harness removal or adjustment to reduce flexion, with recovery usually occurring within a few days to weeks.

Question 2146

Topic: Pediatric Hip

In a patient diagnosed with a unilateral slipped capital femoral epiphysis (SCFE), which of the following represents the strongest indication for prophylactic in situ pinning of the contralateral, currently asymptomatic hip?

. Patient age of 14 years at initial presentation
. Male gender
. Presentation with an acute (rather than chronic) slip
. Underlying endocrine disorder (e.g., hypothyroidism or panhypopituitarism)
. Grade I slip severity on the primarily affected side

Correct Answer & Explanation

. Underlying endocrine disorder (e.g., hypothyroidism or panhypopituitarism)

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is strongly indicated in patients with underlying endocrine disorders (hypothyroidism, growth hormone deficiency, renal osteodystrophy) or previous radiation therapy, as these patients have a much higher risk of bilateral disease (up to 100% in some endocrine subgroups) compared to idiopathic cases.

Question 2147

Topic: 4. Pediatrics

When treating an infant with an idiopathic congenital clubfoot (talipes equinovarus) utilizing the Ponseti method of serial casting, what is the correct sequence of deformity correction?

. Equinus, Varus, Adduction, Cavus
. Cavus, Adduction, Varus, Equinus
. Varus, Cavus, Equinus, Adduction
. Adduction, Equinus, Cavus, Varus
. Cavus, Equinus, Adduction, Varus

Correct Answer & Explanation

. Cavus, Adduction, Varus, Equinus

Explanation

The Ponseti method follows the CAVE sequence: Cavus is corrected first (by elevating the first ray to align the forefoot with the hindfoot), followed by Adduction, then Varus (which corrects simultaneously with adduction as the foot is abducted around the talar head). Equinus is corrected last, often requiring a percutaneous Achilles tenotomy (TAL).

Question 2148

Topic: Pediatric Hip

A 12-year-old boy presents with a unilateral slipped capital femoral epiphysis (SCFE). Prophylactic pinning of the contralateral asymptomatic hip is most strongly indicated if the patient has a history of which of the following concomitant conditions?

. Hypothyroidism
. Hyperthyroidism
. Type 1 Diabetes mellitus
. Primary hyperparathyroidism
. Addison's disease

Correct Answer & Explanation

. Hypothyroidism

Explanation

Patients with endocrine disorders, particularly hypothyroidism, panhypopituitarism, and renal osteodystrophy, have a significantly higher risk of developing bilateral SCFE. In these patients, prophylactic pinning of the contralateral hip is strongly recommended.

Question 2149

Topic: Pediatric Lower Extremity

A 2-week-old infant is undergoing serial casting for a severe idiopathic clubfoot using the Ponseti method. According to the principles of this technique, which component of the deformity is corrected last and typically requires a percutaneous tenotomy?

. Cavus
. Adductus
. Varus
. Equinus
. Supination

Correct Answer & Explanation

. Equinus

Explanation

The Ponseti method addresses clubfoot deformities in the order of the CAVE acronym: Cavus, Adductus, Varus, and finally Equinus. The cavus is corrected first by elevating the first ray (supinating the forefoot). Equinus is corrected last, and an Achilles tenotomy is required in approximately 80-90% of cases to achieve adequate dorsiflexion.

Question 2150

Topic: Pediatric Hip
A 6-year-old boy is diagnosed with Legg-Calvรฉ-Perthes disease. The presence of certain radiographic signs, termed 'head-at-risk' signs by Catterall, suggests a higher likelihood of poor outcomes and extrusion of the femoral head. Which of the following is one of these classic Catterall 'head-at-risk' signs?
. Gage's sign
. Medial subluxation of the femoral head
. Vertical orientation of the physis
. Decreased teardrop distance
. Varus deformity of the femoral neck

Correct Answer & Explanation

. Medial subluxation of the femoral head

Explanation

Catterall described five 'head-at-risk' clinical and radiographic signs in Perthes disease that predict extrusion and a poor outcome. These include: Gage's sign (a V-shaped radiolucency in the lateral portion of the epiphysis and metaphysis), calcification lateral to the epiphysis, lateral subluxation of the femoral head, a horizontal growth plate, and metaphyseal cysts.

Question 2151

Topic: Pediatric Hip

A 9-year-old boy presents with right knee pain and a limp. Examination reveals obligate external rotation with hip flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Considering his age, which of the following laboratory tests is most critical?

. Complete blood count and ESR
. HLA-B27
. Thyroid stimulating hormone (TSH) and Free T4
. Serum calcium, phosphate, and alkaline phosphatase
. Antinuclear antibodies (ANA)

Correct Answer & Explanation

. Thyroid stimulating hormone (TSH) and Free T4

Explanation

Atypical SCFE occurs in patients <10 years or >16 years old, or those with bilateral involvement, low weight, or short stature. Hypothyroidism is the most common endocrine disorder associated with atypical SCFE. Evaluation with TSH and Free T4 is mandatory.

Question 2152

Topic: Pediatric Hip

A 3-year-old girl is newly diagnosed with unilateral developmental dysplasia of the hip (DDH). The hip is dislocated and reducible. What is the most appropriate primary treatment?

. Pavlik harness
. Closed reduction and spica casting
. Open reduction with concomitant pelvic and/or femoral osteotomy
. Observation until age 5 followed by salvage osteotomy
. Injections of botulinum toxin and bracing

Correct Answer & Explanation

. Open reduction with concomitant pelvic and/or femoral osteotomy

Explanation

In a child older than 18-24 months of age, closed reduction is usually unsuccessful due to soft tissue contractures and adaptive bony changes. The standard of care for a 3-year-old with DDH is open reduction, often combined with a pelvic osteotomy and/or a femoral shortening osteotomy to relieve tension and provide stability.

Question 2153

Topic: Pediatric Hip

Which of the following clinical scenarios is the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip in a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE)?

. A 14-year-old male with a BMI in the 95th percentile
. A 10-year-old female with primary hypothyroidism
. A 12-year-old male with a positive family history of SCFE
. A 15-year-old male with a slip angle of 60 degrees
. A 13-year-old female with an acute-on-chronic slip

Correct Answer & Explanation

. A 10-year-old female with primary hypothyroidism

Explanation

Endocrine disorders (such as hypothyroidism, panhypopituitarism, and renal osteodystrophy) carry an exceptionally high risk of bilateral SCFE, sometimes approaching 100%. Prophylactic pinning of the contralateral hip is strongly indicated in patients with underlying endocrinopathies, history of pelvic radiation therapy, or those presenting at an unusually young age (<10 years).

Question 2154

Topic: Pediatric Hip

A 4-month-old infant with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. The parents adjusted the harness themselves, placing the hips in extreme hyperflexion. Which of the following complications is the infant at the highest risk of developing?

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

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Improper use of the Pavlik harness can lead to significant complications. Extreme hyperflexion of the hips can compress the femoral nerve against the inguinal ligament, leading to a femoral nerve palsy, which manifests clinically as an absence of active knee extension. Avascular necrosis is typically associated with excessive forced abduction.

Question 2155

Topic: 4. Pediatrics

A 2-year-old child presents with a painless lump over the right clavicle present since birth. Radiographs show a distinct gap in the middle third of the right clavicle with smooth, rounded bone ends. There is no history of trauma. Which of the following is true regarding this condition?

. It most commonly occurs on the left side.
. It has a strong association with neurofibromatosis type 1.
. It is caused by failure of coalescence of the medial and lateral primary ossification centers.
. Nonoperative management is indicated only if symptomatic.
. It typically presents with a prominent bone spike piercing the skin.

Correct Answer & Explanation

. It is caused by failure of coalescence of the medial and lateral primary ossification centers.

Explanation

Congenital pseudarthrosis of the clavicle (CPC) is a rare condition occurring almost exclusively on the right side. It occurs due to the failure of coalescence of the medial and lateral primary ossification centers of the clavicle. Unlike congenital pseudarthrosis of the tibia, it is not associated with Neurofibromatosis type 1 (NF-1). Surgery is generally considered for cosmetic prominence, pain, or functional limitation, usually around ages 3-5.

Question 2156

Topic: Pediatric Hip

In a patient presenting with a unilateral Slipped Capital Femoral Epiphysis (SCFE), which of the following is the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Age older than 14 years at initial presentation
. Male sex
. An underlying endocrine disorder (e.g., hypothyroidism)
. Grade I (mild) slip on the affected side
. Presence of a metaphyseal blanch sign of Steel

Correct Answer & Explanation

. An underlying endocrine disorder (e.g., hypothyroidism)

Explanation

Prophylactic pinning of the contralateral hip in unilateral SCFE is highly recommended in patients with an underlying endocrine disorder (e.g., hypothyroidism, renal osteodystrophy) or a history of radiation therapy. These patients have a significantly elevated risk (>50%) of developing a bilateral slip. Younger age (<10 years) is also an indication.

Question 2157

Topic: 4. Pediatrics

A 6-year-old child sustains a completely displaced supracondylar humerus fracture and an ipsilateral displaced distal radius fracture ('floating elbow'). The hand is pink, but the radial pulse is absent before reduction. What is the most appropriate management sequence?

. Closed reduction and casting of both fractures in the emergency department
. Closed reduction and percutaneous pinning (CRPP) of the distal radius first, then the supracondylar fracture
. CRPP of the supracondylar humerus fracture first, then management of the distal radius fracture
. Immediate open arterial exploration, followed by fracture fixation
. Application of an external fixator spanning the elbow and wrist

Correct Answer & Explanation

. CRPP of the supracondylar humerus fracture first, then management of the distal radius fracture

Explanation

In a pediatric 'floating elbow' with a pink but pulseless hand, the priority is reduction and stabilization of the supracondylar humerus fracture. The brachial artery is frequently kinked, compressed, or entrapped at the supracondylar fracture site. Closed reduction and percutaneous pinning (CRPP) of the humerus often restores the pulse. The distal radius fracture is managed subsequently.

Question 2158

Topic: Pediatric Hip

A 5-year-old girl with an untreated late developmental dysplasia of the hip (DDH) undergoes an open reduction. During the procedure, the surgeon performs a femoral shortening osteotomy. What is the primary biomechanical and clinical rationale for incorporating this femoral shortening?

. Correct excessive femoral anteversion
. Reduce soft tissue tension to prevent avascular necrosis (AVN)
. Correct an associated coxa vara deformity
. Eliminate the need for a concomitant pelvic osteotomy
. Facilitate closure of the redundant joint capsule

Correct Answer & Explanation

. Reduce soft tissue tension to prevent avascular necrosis (AVN)

Explanation

In older children (typically >3 years) with high DDH dislocations, closed or isolated open reduction forces the femoral head into the true acetabulum under high tension due to contracted soft tissues. This dramatically elevates joint contact pressures, severely increasing the risk of avascular necrosis (AVN) of the femoral head. A femoral shortening osteotomy safely decompresses the joint, facilitates reduction without tension, and preserves the blood supply.

Question 2159

Topic: 4. Pediatrics

Prophylactic in situ pinning of the contralateral, asymptomatic hip in Slipped Capital Femoral Epiphysis (SCFE) is a topic of debate. However, it is almost universally recommended by pediatric orthopedic surgeons in which of the following patient populations?

. Boys older than 15 years
. All female patients regardless of age
. Patients with an underlying endocrine disorder or renal osteodystrophy
. Obese patients with a BMI > 95th percentile
. Patients presenting with isolated bilateral knee pain

Correct Answer & Explanation

. Patients with an underlying endocrine disorder or renal osteodystrophy

Explanation

While the decision for prophylactic pinning is complex and considers factors like age (e.g., girls < 10, boys < 12) and follow-up reliability, the presence of an underlying endocrine disorder (e.g., hypothyroidism, growth hormone deficiency) or renal osteodystrophy is an absolute indication due to the extremely high risk (up to 100%) of bilateral, consecutive slipping.

Question 2160

Topic: 4. Pediatrics

A 2-year-old child is evaluated for multiple fractures with minimal trauma, blue sclerae, and early-onset hearing loss. A diagnosis of Osteogenesis Imperfecta (OI) is suspected. The vast majority of classical OI cases are caused by autosomal dominant mutations affecting type I collagen synthesis. Which genes are most commonly mutated in this condition?

. FGFR3
. COL2A1
. COL1A1 and COL1A2
. COMP
. RUNX2

Correct Answer & Explanation

. COL1A1 and COL1A2

Explanation

Osteogenesis Imperfecta is primarily a defect in Type I collagen, the major protein in bone. 90% of cases are caused by mutations in the COL1A1 or COL1A2 genes. FGFR3 mutations cause achondroplasia; COL2A1 mutations cause type II collagenopathies (e.g., SED, achondrogenesis); COMP mutations cause pseudoachondroplasia; and RUNX2 mutations cause cleidocranial dysplasia.

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