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4. Pediatrics MCQs

Practice Set 88 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 1741

Topic: Pediatric Upper Extremity & Spine

A 14-year-old female with Adolescent Idiopathic Scoliosis (AIS) has a main thoracic curve of 55 degrees, a proximal thoracic curve of 30 degrees that bends out to 15 degrees, and a thoracolumbar curve of 40 degrees that bends out to 20 degrees. The apical lumbar vertebra is bisected by the center sacral vertical line (CSVL). The T5-T12 sagittal kyphosis is 25 degrees. What is her Lenke classification?

. Lenke 1AN
. Lenke 1BN
. Lenke 2BN
. Lenke 3BN
. Lenke 1CN

Correct Answer & Explanation

. Lenke 1BN

Explanation

The main thoracic curve is the major curve, and both minor curves bend out to < 25 degrees, making it a Type 1 (Main Thoracic). The CSVL bisecting the apical lumbar vertebra makes it a lumbar modifier B. Normal sagittal kyphosis (10 to 40 degrees) gives a sagittal modifier N, resulting in 1BN.

Question 1742

Topic: Pediatric Upper Extremity & Spine

In the evaluation of Adolescent Idiopathic Scoliosis (AIS), dynamic side-bending radiographs are routinely obtained. According to the Lenke classification, a curve is defined as 'structural' if it has a residual Cobb angle of at least what magnitude on maximal side-bending?

. 10 degrees
. 15 degrees
. 20 degrees
. 25 degrees
. 30 degrees

Correct Answer & Explanation

. 25 degrees

Explanation

The Lenke classification of AIS dictates that a minor curve is considered structurally significant if it does not bend out to less than 25 degrees (i.e., residual Cobb angle is >/= 25 degrees) on dynamic side-bending radiographs or has a kyphosis >/= +20 degrees.

Question 1743

Topic: 4. Pediatrics
A 14-year-old boy presents with ankle pain after an external rotation injury. Radiographs show a Salter-Harris III fracture of the anterolateral aspect of the distal tibia. Which of the following best explains the specific location of this fracture?
. The anterolateral physis is the first to close
. The anterolateral physis is the last to close
. Avulsion by the posterior inferior tibiofibular ligament
. Weakness of the deltoid ligament
. High-energy axial loading

Correct Answer & Explanation

. The anterolateral physis is the last to close

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibia. It occurs in adolescents because the distal tibial physis closes in a specific pattern: central, then medial, and finally lateral. Because the anterolateral physis is the last to close, it remains vulnerable to avulsion by the anterior inferior tibiofibular ligament (AITFL) during an external rotation injury.

Question 1744

Topic: 4. Pediatrics
A 13-year-old female presents with ankle pain after an external rotation injury. Radiographs reveal a Salter-Harris type III fracture of the anterolateral aspect of the distal tibial epiphysis. This fracture pattern (Tillaux fracture) is primarily due to an avulsion force from which of the following ligaments?
. Posterior inferior tibiofibular ligament (PITFL)
. Anterior inferior tibiofibular ligament (AITFL)
. Anterior talofibular ligament (ATFL)
. Calcaneofibular ligament (CFL)
. Deltoid ligament

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament (AITFL)

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibia epiphysis. It occurs in adolescents due to the asymmetric closure of the distal tibial physis (central first, then medial, with lateral being the last to close). External rotation causes the anterior inferior tibiofibular ligament (AITFL) to avulse the anterolateral epiphyseal fragment.

Question 1745

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 tibia. Which of the following best describes the anatomical basis and mechanism of this specific fracture pattern?
. Plantarflexion and inversion injury causing avulsion via the anterior talofibular ligament (ATFL)
. External rotation injury causing avulsion via the anterior inferior tibiofibular ligament (AITFL) due to late closure of the anterolateral physis
. Axial loading causing impaction of the talus into the central physis
. Eversion injury causing avulsion via the deltoid ligament
. Internal rotation injury causing avulsion via the posterior inferior tibiofibular ligament (PITFL)

Correct Answer & Explanation

. External rotation injury causing avulsion via the anterior inferior tibiofibular ligament (AITFL) due to late closure of the anterolateral physis

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibia. It occurs in adolescents due to the asymmetric closure of the distal tibial physis (closes central to medial to lateral). 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 1746

Topic: 4. Pediatrics
A 14-year-old boy presents with an ankle injury after falling off his skateboard. Radiographs demonstrate a Salter-Harris III fracture of the anterolateral distal tibia. What is the primary deforming force and the associated ligament responsible for avulsing this fragment?
. Internal rotation; Anterior inferior tibiofibular ligament
. External rotation; Anterior inferior tibiofibular ligament
. Inversion; Calcaneofibular ligament
. Plantarflexion; Anterior talofibular ligament
. External rotation; Posterior inferior tibiofibular ligament

Correct Answer & Explanation

. External rotation; Anterior inferior tibiofibular ligament

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. It is caused by an external rotation force applied to the foot. The anterior inferior tibiofibular ligament (AITFL) is tensioned and avulses the anterolateral fragment, as this is the final portion of the distal tibial physis to close.

Question 1747

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents with a Gartland Type III supracondylar humerus fracture. On examination, the hand is pink and well-perfused, but the radial pulse is absent. Following closed reduction and percutaneous pinning, the hand remains pink, but the pulse is still absent. What is the next best step in management?
. Immediate vascular surgery consult for open arterial exploration
. Observation and admission for close clinical monitoring
. Removal of all pins and open reduction via an anterior approach
. Performance of an upper extremity angiogram
. Application of a long arm cast in 120 degrees of flexion

Correct Answer & Explanation

. Observation and admission for close clinical monitoring

Explanation

In the setting of a pink, pulseless hand following successful reduction and pinning of a pediatric supracondylar fracture, the standard of care is close clinical observation. Open exploration is only indicated if the hand becomes pale and poorly perfused (ischemic).

Question 1748

Topic: Pediatric Upper Extremity & Spine
A 5-year-old boy sustains a Gartland type III supracondylar humerus fracture. On initial presentation, the radial pulse is absent, but the hand is pink and warm. Following closed reduction and percutaneous pinning, the hand remains pink and well-perfused, but the pulse is still absent on Doppler. What is the most appropriate next step?
. Immediate open vascular exploration and repair
. CT angiography of the upper extremity
. Remove percutaneous pins and perform open reduction
. Observation and admission for close neurovascular monitoring
. Emergent volar and dorsal fasciotomies of the forearm

Correct Answer & Explanation

. Observation and admission for close neurovascular monitoring

Explanation

A 'pulseless, pink' hand after anatomic reduction of a pediatric supracondylar humerus fracture indicates adequate collateral circulation. Current guidelines recommend close inpatient observation rather than immediate vascular exploration, as the pulse typically returns over hours to days.

Question 1749

Topic: Pediatric Upper Extremity & Spine

In the Lenke classification for adolescent idiopathic scoliosis (AIS), a structural proximal thoracic (PT) curve is defined by either a regional kyphosis (T2-T5) of at least +20 degrees, OR a side-bending Cobb angle of at least what magnitude?

. 10 degrees
. 15 degrees
. 20 degrees
. 25 degrees
. 30 degrees

Correct Answer & Explanation

. 20 degrees

Explanation

According to the Lenke classification system for AIS, a curve is considered structural if the Cobb angle fails to correct to less than 25 degrees on side-bending radiographs, OR if there is a regional kyphosis of at least +20 degrees.

Question 1750

Topic: Pediatric Upper Extremity & Spine
In the Lenke classification system for adolescent idiopathic scoliosis (AIS), a minor curve is considered 'structural' and generally must be included in the fusion construct if it meets which of the following radiographic criteria?
. Cobb angle > 10 degrees on a standing coronal radiograph
. Cobb angle > 15 degrees on a dynamic push-prone radiograph
. Cobb angle ≥ 25 degrees on a coronal side-bending radiograph
. Apical vertebral translation > 2 cm
. Apical vertebral rotation Grade III or greater

Correct Answer & Explanation

. Cobb angle ≥ 25 degrees on a coronal side-bending radiograph

Explanation

According to the Lenke classification for AIS, a minor curve is considered structural if it fails to correct to less than 25 degrees on a coronal side-bending radiograph (i.e., Cobb angle remains ≥ 25 degrees). A regional sagittal kyphosis of ≥ +20 degrees also defines a minor curve as structural.

Question 1751

Topic: Pediatric Upper Extremity & Spine

A 14-year-old female presents with adolescent idiopathic scoliosis. Radiographs demonstrate a main thoracic curve of 55 degrees, a proximal thoracic curve of 20 degrees that bends out to 15 degrees, and a thoracolumbar/lumbar curve of 35 degrees that bends out to 15 degrees. The T5-T12 kyphosis is +25 degrees. According to the Lenke classification system, what is her curve type?

. Lenke 1
. Lenke 2
. Lenke 3
. Lenke 4
. Lenke 6

Correct Answer & Explanation

. Lenke 1

Explanation

Lenke 1 is a Main Thoracic curve. The minor curves (proximal thoracic and thoracolumbar/lumbar) bend out to < 25 degrees, meaning they are non-structural. The sagittal modifier is Normal (N) because T5-T12 kyphosis is between +10 and +40 degrees. Therefore, she is a Lenke 1.

Question 1752

Topic: 4. Pediatrics

An 8-year-old girl was treated for a Salter-Harris type I fracture of the right distal femur 2 years ago. She has symmetric knee flexion, extension, and frontal alignment to her contralateral knee. She has a 1-cm limb-length discrepancy of the femur. She has always been in the 50th percentile for height and her skeletal age matches her chronologic age. She has a complete physeal closure of the right distal femur. What is the expected limb-length discrepancy at maturity? Review Topic

. 3 cm
. 6 cm
. 10 cm
. 14 cm
. 18 cm

Correct Answer & Explanation

. 10 cm

Explanation

The child has a near complete central physeal arrest of the distal femur. She will develop worsening limb-length discrepancy. She is growing at the average rate for the population. The distal femoral physis grows roughly at a rate of 9 mm/year. Girls finish their growth roughly at 14 years. Thus, at maturity, the uninjured side will be

Question 1753

Topic: Pediatric Hip

In a 12-year-old male presenting with a unilateral slipped capital femoral epiphysis (SCFE), which of the following factors is the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Male sex
. African American race
. Obesity (BMI > 95th percentile)
. Underlying endocrine disorder
. Age over 14 years

Correct Answer & Explanation

. Underlying endocrine disorder

Explanation

While unilateral SCFE can progress to bilateral disease in about 20-40% of cases, patients with underlying endocrine disorders (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency) have an exceptionally high risk of bilateral involvement (up to 100% in some series). Therefore, an underlying endocrinopathy is a strong and widely accepted absolute indication for prophylactic pinning of the contralateral hip.

Question 1754

Topic: Pediatric Hip

When performing a total hip arthroplasty on a patient with Crowe Type IV developmental dysplasia of the hip (DDH), the true native acetabulum is characteristically deficient in which of the following regions?

. Anterior and superior
. Anterior and inferior
. Posterior and superior
. Posterior and inferior
. Medial and inferior

Correct Answer & Explanation

. Anterior and superior

Explanation

In developmental dysplasia of the hip (DDH), the true acetabulum is classically shallow, with the greatest bony deficiency located in the anterior and superior walls. This morphological abnormality necessitates careful preoperative planning for acetabular cup placement and often requires the use of structural bone grafts or specialized augments to achieve adequate superior-anterior coverage.

Question 1755

Topic: Pediatric Upper Extremity & Spine

A 13-year-old premenarchal female (Risser stage 0) is diagnosed with adolescent idiopathic scoliosis (AIS). Her primary right thoracic curve measures 32 degrees on standing PA radiographs. According to the guidelines of the Scoliosis Research Society (SRS), what is the most appropriate next step in management?

. Observation with repeat standing radiographs in 6 months
. Prescription of a rigid thoracolumbosacral orthosis (TLSO) for 16-23 hours daily
. Prescription of a nighttime-only bending brace
. Posterior spinal fusion with segmental instrumentation
. Anterior vertebral body tethering

Correct Answer & Explanation

. Prescription of a rigid thoracolumbosacral orthosis (TLSO) for 16-23 hours daily

Explanation

According to the SRS criteria, bracing is indicated for actively growing patients (girls who are premenarchal or <1 year postmenarchal, Risser 0-2) with a primary curve measuring between 25 and 40 degrees. The standard of care, supported by the BrAIST trial, is a rigid TLSO worn for 16-23 hours a day, which significantly decreases the risk of curve progression to the surgical threshold.

Question 1756

Topic: Pediatric Hip

A 13-year-old obese male presents to the emergency department with acute-on-chronic left knee pain and an absolute inability to bear weight on the left lower extremity. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Which of the following factors is the most significant predictor for the development of avascular necrosis (AVN) in this patient?

. The magnitude of the slip angle
. The patient's body mass index (BMI)
. The clinical instability of the slip (inability to bear weight)
. Delay in surgical fixation beyond 24 hours
. The presence of an underlying endocrine disorder

Correct Answer & Explanation

. The clinical instability of the slip (inability to bear weight)

Explanation

According to the Loder classification, SCFE is divided into stable (able to bear weight) and unstable (unable to bear weight, even with crutches). Unstable slips carry a significantly higher risk of avascular necrosis (AVN), reported to be up to 47%, whereas stable slips have an AVN rate approaching zero. This clinical feature is the most important prognostic factor for AVN.

Question 1757

Topic: Pediatric Hip

A 4-month-old infant is undergoing treatment with a Pavlik harness for developmental dysplasia of the hip (DDH). At the two-week follow-up, the mother reports that the infant has stopped kicking the leg on the affected side. Examination reveals an absent patellar reflex and profound quadriceps weakness. What is the most likely cause of this finding, and what is the next best step in management?

. Sciatic nerve palsy from excessive hip flexion; loosen the anterior straps.
. Femoral nerve palsy from excessive hip flexion; temporarily loosen the anterior straps or discontinue the harness.
. Obturator nerve palsy from excessive hip abduction; loosen the posterior straps.
. Femoral nerve palsy from excessive hip abduction; abandon the harness and proceed to closed reduction.
. Avascular necrosis of the femoral head; obtain an urgent MRI.

Correct Answer & Explanation

. Femoral nerve palsy from excessive hip flexion; temporarily loosen the anterior straps or discontinue the harness.

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment, caused by hyperflexion of the hip which compresses the nerve against the pelvis. It presents with decreased active knee extension and an absent patellar reflex. The appropriate management is to loosen the anterior flexion straps or temporarily discontinue the harness to allow the nerve to recover, which it typically does within days to weeks.

Question 1758

Topic: Pediatric Hip

A 12-year-old obese boy presents with a left-sided stable slipped capital femoral epiphysis (SCFE). Which of the following is the strongest indication for prophylactic in situ pinning of the asymptomatic right hip?

. Patient age over 14 years
. Female gender
. Presence of an endocrine disorder such as hypothyroidism
. Body mass index > 95th percentile
. Severe slip angle (> 50 degrees) on the affected side

Correct Answer & Explanation

. Presence of an endocrine disorder such as hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is strongly recommended in patients with endocrine disorders (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) due to the exceedingly high risk of bilateral involvement. Age less than 10, open triradiate cartilage, and prior radiation therapy are also considered indications for prophylactic fixation.

Question 1759

Topic: Pediatric Hip

A 22-year-old female is evaluated for symptomatic developmental dysplasia of the hip (DDH). Preoperative planning for a Bernese periacetabular osteotomy (PAO) is underway. Which of the following is a strict prerequisite for a successful PAO in this patient?

. A completely closed triradiate cartilage
. Tonnis grade 3 osteoarthritis
. Lack of congruency on abduction-internal rotation views
. Age over 30 years
. An alpha angle greater than 60 degrees

Correct Answer & Explanation

. A completely closed triradiate cartilage

Explanation

The Bernese periacetabular osteotomy (PAO) is indicated for symptomatic DDH in adolescents and young adults. A strict prerequisite is a closed triradiate cartilage to prevent growth arrest, as the osteotomy cuts through the ilium, ischium, and pubis around the acetabulum. Advanced osteoarthritis (Tonnis grade 2 or 3) is a relative contraindication, and the joint must demonstrate congruency on functional (abduction/internal rotation) views to ensure the redirected acetabulum will articulate properly.

Question 1760

Topic: Pediatric Upper Extremity & Spine

In the Lenke classification for adolescent idiopathic scoliosis (AIS), which of the following criteria determines whether a secondary (minor) curve is considered 'structural' and therefore necessitates inclusion in the fusion construct?

. Cobb angle > 15 degrees on standing PA radiograph
. Cobb angle > 25 degrees on side-bending radiographs
. Apical vertebral translation > 2 cm
. Nash-Moe rotation of grade II or higher
. Presence of a concomitant kyphosis > 10 degrees

Correct Answer & Explanation

. Cobb angle > 25 degrees on side-bending radiographs

Explanation

According to the Lenke classification of AIS, a minor curve is considered structural if it fails to correct to < 25 degrees on supine side-bending radiographs, or if there is regional kyphosis > 20 degrees. Structural minor curves must generally be included in the surgical fusion construct to achieve optimal coronal and sagittal balance.

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