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4. Pediatrics MCQs

Practice Set 121 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 2401

Topic: 4. Pediatrics
A 14-year-old boy sustains a twisting injury to his ankle. Radiographs reveal a Salter-Harris III fracture of the anterolateral distal tibia. The avulsed bony fragment is attached to which of the following structures?
. Anterior inferior tibiofibular ligament
. Posterior inferior tibiofibular ligament
. Anterior talofibular ligament
. Calcaneofibular ligament
. Deltoid ligament

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament

Explanation

This describes a juvenile Tillaux fracture, which occurs due to avulsion of the anterior inferior tibiofibular ligament (AITFL). The anterolateral physis is the last to close, making it susceptible to this specific Salter-Harris III injury.

Question 2402

Topic: 4. Pediatrics
A 14-year-old boy sustains an ankle injury during a soccer match. Radiographs demonstrate a Salter-Harris III fracture of the anterolateral aspect of the distal tibia epiphysis. Which of the following ligaments exerts the primary deforming force in this injury?
. Anterior talofibular ligament
. Calcaneofibular ligament
. Anterior inferior tibiofibular ligament
. Posterior inferior tibiofibular ligament
. Deltoid ligament

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament

Explanation

The AITFL attaches to the anterolateral distal tibia (Chaput tubercle) and causes a Salter-Harris III avulsion fracture in adolescents when the foot is externally rotated. This is known as a Tillaux fracture.

Question 2403

Topic: 4. Pediatrics

A 13-year-old male baseball pitcher presents with 3 months of lateral shoulder pain during the acceleration phase of throwing. Radiographs demonstrate widening and irregularity of the proximal humeral physis. What is the primary pathophysiology of this condition?

. Avascular necrosis of the humeral head
. Traction apophysitis of the greater tuberosity
. Salter-Harris type I stress fracture of the proximal humerus
. Partial tear of the articular-sided rotator cuff
. Superior labrum anterior to posterior (SLAP) tear

Correct Answer & Explanation

. Salter-Harris type I stress fracture of the proximal humerus

Explanation

This presentation describes 'Little Leaguer's shoulder,' which is characterized radiographically by a widened proximal humeral physis. Pathophysiologically, it represents a Salter-Harris type I stress fracture caused by repetitive torsional loads during the throwing motion.

Question 2404

Topic: 4. Pediatrics

A 14-year-old elite baseball pitcher presents with right shoulder pain that occurs exclusively during the late cocking phase of throwing. Radiographs demonstrate widening of the proximal humeral physis. What is the most appropriate initial management?

. Corticosteroid injection into the subacromial space
. Absolute rest from throwing for 3 months followed by physical therapy
. Arthroscopic SLAP repair
. Physical therapy with immediate continuation of throwing program
. Open physeal bar resection

Correct Answer & Explanation

. Absolute rest from throwing for 3 months followed by physical therapy

Explanation

'Little League Shoulder' is a stress fracture of the proximal humeral physis caused by repetitive rotational torque. The cornerstone of treatment is absolute rest from throwing for typically 3 months to allow physeal healing.

Question 2405

Topic: 4. Pediatrics

In the development of a long bone, which zone of the physis is characterized by a high concentration of type X collagen and is the weakest area, most susceptible to slipped capital femoral epiphysis (SCFE)?

. Reserve zone
. Proliferative zone
. Zone of hypertrophy
. Zone of provisional calcification
. Primary spongiosa

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

The zone of hypertrophy is the weakest part of the growth plate and is typically the site of physeal fractures and SCFE. It is uniquely characterized by the expression of type X collagen.

Question 2406

Topic: 4. Pediatrics

A child presents with rhizomelic shortening of the limbs, frontal bossing, and midface hypoplasia. The genetic mutation responsible for this condition primarily affects which of the following processes?

. Osteoclast differentiation and ruffled border formation
. Type I collagen triple helix formation
. Chondrocyte proliferation in the proliferative zone of the physis
. Mineralization of osteoid in the metaphysis
. Cleavage of the procollagen molecule

Correct Answer & Explanation

. Chondrocyte proliferation in the proliferative zone of the physis

Explanation

Achondroplasia is caused by a gain-of-function mutation in the FGFR3 gene. This over-activates FGFR3, inhibiting chondrocyte proliferation and hypertrophy in the proliferative zone of the physis and disrupting endochondral ossification.

Question 2407

Topic: 4. Pediatrics

A patient with multiple fragility fractures, blue sclerae, and hearing loss is diagnosed with Osteogenesis Imperfecta. The underlying defect typically involves a substitution of which amino acid in the collagen triple helix?

. Proline
. Hydroxyproline
. Glycine
. Lysine
. Hydroxylysine

Correct Answer & Explanation

. Glycine

Explanation

Osteogenesis imperfecta is most commonly caused by mutations in the COL1A1 or COL1A2 genes. These mutations typically result in the substitution of glycine, the smallest amino acid essential for the tight packing of the collagen triple helix.

Question 2408

Topic: Pediatric Hip

A 6-year-old boy is diagnosed with Legg-Calve-Perthes disease. In evaluating the pathogenesis of avascular necrosis in this age group, which of the following arteries provides the predominant blood supply to the capital femoral epiphysis?

. Artery of the ligamentum teres
. Lateral epiphyseal branches of the medial femoral circumflex artery
. Inferior metaphyseal arteries
. Anterior ascending branches of the lateral femoral circumflex artery
. Internal pudendal artery

Correct Answer & Explanation

. Lateral epiphyseal branches of the medial femoral circumflex artery

Explanation

In children over the age of 3-4 years and persisting into adulthood, the predominant blood supply to the femoral head is provided by the lateral epiphyseal branches of the medial femoral circumflex artery (MFCA).

Question 2409

Topic: Pediatric Upper Extremity & Spine

A 10-year-old boy sustains a supracondylar humerus fracture. After reduction, he is unable to flex the interphalangeal joint of his thumb and the distal interphalangeal joint of his index finger. If this specific nerve injury persists, which of the following muscles will also demonstrate denervation on electromyography?

. Flexor carpi radialis
. Pronator teres
. Pronator quadratus
. Flexor digitorum superficialis
. Abductor pollicis brevis

Correct Answer & Explanation

. Pronator quadratus

Explanation

The patient has an anterior interosseous nerve (AIN) palsy, a branch of the median nerve. The AIN innervates the flexor pollicis longus, the flexor digitorum profundus to the index and long fingers, and the pronator quadratus.

Question 2410

Topic: 4. Pediatrics

A 10-year-old female with wide-open physes sustains a complete midsubstance ACL tear. When planning an all-epiphyseal ACL reconstruction, which anatomical structure is at greatest risk of iatrogenic injury during femoral tunnel drilling?

. Peroneal nerve
. Distal femoral physis
. Medial collateral ligament
. Popliteal artery
. Anterior horn of the lateral meniscus

Correct Answer & Explanation

. Distal femoral physis

Explanation

In an all-epiphyseal ACL reconstruction for skeletally immature patients, the femoral tunnel must be drilled entirely distal to the distal femoral physis. Errant drilling can cause physeal arrest and subsequent severe angular or leg-length deformities.

Question 2411

Topic: 4. Pediatrics

A 12-year-old boy is tackled from the lateral side of his knee during a football game. He presents with medial knee pain and significant valgus laxity at 30 degrees of flexion. Radiographs appear normal. What is the most critical next step in the diagnostic workup to rule out a severe pathology that mimics a medial collateral ligament (MCL) tear?

. Diagnostic knee arthroscopy
. Stress radiographs or MRI to evaluate for a distal femoral physeal fracture
. Aspiration of the knee joint to check for hemarthrosis
. Measurement of the Ankle-Brachial Index (ABI)
. Immediate application of a hinged knee brace and weight-bearing as tolerated

Correct Answer & Explanation

. Stress radiographs or MRI to evaluate for a distal femoral physeal fracture

Explanation

In skeletally immature patients, the collateral ligaments are often stronger than the open physes. Apparent severe valgus laxity may actually represent a Salter-Harris fracture of the distal femur, which must be ruled out with stress views or MRI before treating as a simple MCL sprain.

Question 2412

Topic: 4. Pediatrics

A 12-year-old male with open physes sustains an ACL tear. Which surgical technique minimizes the risk of significant growth arrest?

. Transphyseal bone-patellar tendon-bone reconstruction
. Iliotibial band over-the-top physeal-sparing reconstruction
. Standard adult transphyseal hamstring reconstruction
. Wait until skeletal maturity while allowing unrestricted activity
. Primary repair with synthetic ligament augmentation

Correct Answer & Explanation

. Iliotibial band over-the-top physeal-sparing reconstruction

Explanation

In skeletally immature patients with significant remaining growth, physeal-sparing techniques such as an IT band over-the-top extra-articular and intra-articular reconstruction minimize the risk of premature physeal closure.

Question 2413

Topic: 4. Pediatrics

A 7-year-old boy with spastic diplegia is a limited community ambulator. He has a moderately severe crouched gait. The parents request a treatment that will result in a permanent decrease in lower extremity muscle tone. This is best accomplished with

. tone-reduction ankle-foot orthoses (AFOs).
. intramuscular injections of botulinum-A toxin.
. an intrathecal baclofen injection.
. selective posterior rhizotomy.
. fractional tendon lengthening of bilateral hamstring and gastrocnemius muscles.

Correct Answer & Explanation

. selective posterior rhizotomy.

Explanation

Posterior rhizotomy provides a permanent reduction in tone of spastic muscles. Potential drawbacks of the procedure include excessive muscle weakness, hip dislocation, and spinal deformity. Intramuscular botulinum-A toxin results in permanent blockade of presynaptic release of acetylcholine across the neuromuscular junction. The clinical effect usually resolves after 3 to 6 months due to neural regeneration. Tone-reduction AFOs have not been shown to reduce tone. A baclofen pump could offer prolonged reduction in tone, but not a single intrathecal injection. Arens LJ, Peacock WJ, Peter J: Selective posterior rhizotomy: A long-term follow-up study. Childs Nerv Syst 1989;5:148-152. Koman LA, Paterson Smith B, Balkrishnan R: Spasticity associated with cerebral palsy in children: Guidelines for the use of botulinum-A toxin. Paediatr Drugs 2003;5:11-23.

Question 2414

Topic: 4. Pediatrics

A 3-year-old boy had been treated with serial casting for a right congenital idiopathic clubfoot deformity. The parents are concerned because the child now walks on the lateral border of the right foot. Examination shows that the foot passively achieves a plantigrade position with neutral heel valgus and ankle dorsiflexion to 15 degrees. The forefoot inverts during active ankle dorsiflexion. Mild residual metatarsus adductus is present. Management should now consist of

. additional serial casting.
. a floor-reaction ankle-foot orthosis.
. closing wedge cuboid osteotomy.
. lateral transfer of the anterior tibialis tendon.
. posterior tibial tendon transfer through the interosseous membrane to the third metatarsal.

Correct Answer & Explanation

. lateral transfer of the anterior tibialis tendon.

Explanation

Dynamic midfoot supination that is the result of peroneal weakness is a common residual problem after cast correction or surgical reconstruction of a congenital idiopathic clubfoot. Dynamic supination is unlikely to resolve spontaneously. Most parents do not want to use brace support forever. Transfer of the posterior tibialis to the dorsum of the foot has shown poor results in clubfeet. Preferred treatments include: 1) transfer of the entire anterior tibialis tendon to the lateral cuneiform, or 2) split transfer of the anterior tibialis tendon to the cuboid or to the peroneus brevis tendon. Kuo KN, Hennigan SP, Hastings ME: Anterior tibial tendon transfer in residual dynamic clubfoot deformity. J Pediatr Orthop 2001;21:35-41. Garceau GJ: Anterior tibial tendon transfer for recurrent clubfoot. Clin Orthop 1972;84:61-65.

Question 2415

Topic: Pediatric Hip

A 3-month-old girl is being treated for developmental dysplasia of the hip (DDH) with a Pavlik harness. During a follow-up visit, the parents report that the child has stopped actively extending her knee on the treated side. On examination, the patellar reflex is diminished. What is the most appropriate next step in management?

. Continue the harness and add physical therapy
. Adjust the anterior strap to increase hip flexion
. Remove the harness and observe for spontaneous recovery
. Transition immediately to a rigid hip spica cast
. Perform an urgent ultrasound to rule out deep vein thrombosis

Correct Answer & Explanation

. Remove the harness and observe for spontaneous recovery

Explanation

The clinical presentation is consistent with a femoral nerve palsy, a known complication of excessive hip flexion in a Pavlik harness. Management requires immediate removal of the harness to allow for spontaneous neurological recovery.

Question 2416

Topic: Pediatric Hip

A 6-week-old infant presents for a routine screening hip ultrasound due to a breech presentation. The ultrasound report indicates an alpha angle of 48 degrees and a beta angle of 75 degrees. Which of the following is the most appropriate interpretation and management?

. Normal hip; no further follow-up needed
. Physiologic immaturity; repeat ultrasound in 4 weeks
. Developmental dysplasia; initiate Pavlik harness treatment
. Severe dysplasia; schedule for closed reduction and spica casting
. Borderline dysplasia; recommend double-diapering

Correct Answer & Explanation

. Developmental dysplasia; initiate Pavlik harness treatment

Explanation

An alpha angle less than 60 degrees and a beta angle greater than 55 degrees on a coronal ultrasound indicate developmental dysplasia of the hip (Graf Type IIc or worse). Initiation of a Pavlik harness is the standard of care for an infant at this age with these parameters.

Question 2417

Topic: 4. Pediatrics

A 9-month-old child with DDH undergoes an attempted closed reduction in the operating room. An intraoperative arthrogram reveals an hourglass constriction that prevents the femoral head from seating fully into the true acetabulum. Which of the following structures is primarily responsible for this specific radiographic finding?

. Ligamentum teres
. Transverse acetabular ligament
. Iliopsoas tendon
. Pulvinar
. Inverted labrum (limbus)

Correct Answer & Explanation

. Iliopsoas tendon

Explanation

An hourglass constriction seen on an arthrogram during DDH reduction is classic for an obstructing iliopsoas tendon. While the pulvinar, ligamentum teres, and transverse acetabular ligament can block reduction, they typically cause a medial dye pool rather than an hourglass shape.

Question 2418

Topic: Pediatric Hip

A 13-year-old obese boy presents with 2 days of severe left hip pain and inability to bear weight after a minor fall. Radiographs confirm a severe slipped capital femoral epiphysis (SCFE). According to the Loder classification, what is the most significant prognostic factor associated with his presentation?

. A high risk of chondrolysis
. A 10% to 50% risk of avascular necrosis (AVN)
. A high likelihood of contralateral slip
. The need for prophylactic pinning of the right hip
. Guaranteed premature osteoarthritis

Correct Answer & Explanation

. A 10% to 50% risk of avascular necrosis (AVN)

Explanation

Under the Loder classification, a SCFE is unstable if the patient cannot bear weight, even with crutches. Unstable SCFE has a much higher rate of avascular necrosis (10% to 50%) compared to stable SCFE (less than 10%).

Question 2419

Topic: Pediatric Hip

An 8-year-old boy whose weight is in the 40th percentile presents with groin pain and an altered gait. Radiographs reveal a mild stable slipped capital femoral epiphysis (SCFE). Given the patient's age and body habitus, which of the following is the most appropriate next step in evaluation?

. Genetic testing for Down syndrome
. DEXA scan
. Endocrine laboratory workup (TSH, free T4, BUN, Cr)
. MRI of the lumbosacral spine
. Rheumatoid factor and ANA testing

Correct Answer & Explanation

. Endocrine laboratory workup (TSH, free T4, BUN, Cr)

Explanation

SCFE typically occurs in obese adolescents during the pubertal growth spurt. Presentation in patients younger than 10 years or those who are not overweight strongly warrants an endocrine workup to rule out hypothyroidism or renal osteodystrophy.

Question 2420

Topic: Pediatric Hip

Which of the following radiographic signs is most sensitive for detecting an early, subtle Slipped Capital Femoral Epiphysis (SCFE) on an anteroposterior (AP) pelvis radiograph?

. The femoral head is displaced medially to the ilioischial line
. Klein's line fails to intersect a portion of the lateral femoral epiphysis
. The epiphyseal-diaphyseal angle is greater than 50 degrees
. A "crescent sign" is visible in the subchondral bone
. The teardrop distance is widened by more than 2 mm

Correct Answer & Explanation

. Klein's line fails to intersect a portion of the lateral femoral epiphysis

Explanation

Klein's line is drawn along the superior edge of the femoral neck on an AP radiograph. In a normal hip, it should intersect the lateral portion of the femoral epiphysis; failure to do so (Trethowan's sign) indicates a SCFE.

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