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4. Pediatrics MCQs

Practice Set 141 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 2801

Topic: 4. Pediatrics

Salter-Harris fractures typically occur through the weakest portion of the pediatric physis. Which zone of the physis is most frequently implicated as the site of failure?

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

Correct Answer & Explanation

. Reserve zone

Explanation

Fractures through the growth plate typically propagate through the zone of hypertrophy. This zone lacks substantial collagen and has a high ratio of chondrocyte volume to matrix, making it the weakest layer biomechanically.

Question 2802

Topic: 4. Pediatrics

Salter-Harris fractures typically propagate through the physis, affecting bone growth depending on the severity of the injury. Through which histologic zone of the physis do these fractures classically propagate?

. Zone of resting cartilage
. Zone of proliferation
. Zone of hypertrophy
. Zone of provisional calcification
. Primary spongiosa

Correct Answer & Explanation

. Zone of resting cartilage

Explanation

Fractures through the growth plate (physis) classically propagate through the zone of hypertrophy. This zone is mechanically the weakest due to the lack of collagen and large volume of intracellular fluid within the hypertrophic chondrocytes.

Question 2803

Topic: 4. Pediatrics

A 10-year-old child presents with a painful clunking lateral knee. MRI demonstrates a Wrisberg variant of a discoid lateral meniscus. This specific variant is characterized by which of the following anatomical features?

. Absence of the anterior horn meniscotibial ligament
. Absence of the posterior meniscofemoral ligament
. Absence of the posterior coronary ligaments
. A thick central zone with normal peripheral capsular attachments
. Medial meniscus involvement in 50% of cases

Correct Answer & Explanation

. Absence of the anterior horn meniscotibial ligament

Explanation

The Wrisberg variant of a discoid lateral meniscus lacks the normal posterior capsular attachments (coronary ligaments). Its only posterior attachment is the meniscofemoral ligament of Wrisberg, leading to extreme hypermobility and the classic snapping knee syndrome.

Question 2804

Topic: 4. Pediatrics

A 12-year-old Tanner stage 1 male sustains a mid-substance ACL tear. Due to his open physes, a physeal-sparing reconstruction is planned using the iliotibial band (MacIntosh or Micheli procedure). This technique primarily addresses which plane of instability?

. Anterior translation only
. Posterior translation only
. Varus instability
. Anterolateral rotatory instability
. Valgus instability

Correct Answer & Explanation

. Anterior translation only

Explanation

Physeal-sparing extra-articular reconstructions using the IT band primarily control anterolateral rotatory instability. They do not fully restore central pivot biomechanics but prevent pivot-shift events until skeletal maturity.

Question 2805

Topic: Pediatric Hip

A 6-week-old female infant is currently 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 kicking her right leg. Examination reveals decreased active extension of the right knee, while ankle movements and toe flexion are intact. Which nerve is most likely affected?

. Sciatic nerve
. Femoral nerve
. Obturator nerve
. Peroneal nerve
. Tibial nerve

Correct Answer & Explanation

. Sciatic nerve

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment, typically resulting from hyperflexion of the hips. It presents with decreased active knee extension and usually resolves completely when the harness is removed or adjusted.

Question 2806

Topic: Pediatric Upper Extremity & Spine

A 5-year-old boy sustains a Gartland type III extension-type supracondylar humerus fracture. On initial presentation, his hand is pink but pulseless. Following a satisfactory closed reduction and percutaneous pinning, the hand remains pink with brisk capillary refill, but the radial pulse remains unpalpable. What is the most appropriate next step in management?

. Immediate anterior vascular exploration
. Observation and hospital admission for 24 to 48 hours
. Emergent formal arteriography
. Removal of the pins and application of a long-arm cast
. Prophylactic fasciotomy of the forearm

Correct Answer & Explanation

. Immediate anterior vascular exploration

Explanation

A "pink, pulseless" hand following adequate reduction and pinning of a supracondylar fracture generally has adequate collateral circulation and can be safely observed. The pulse typically returns within a few days, avoiding the need for immediate vascular exploration.

Question 2807

Topic: Pediatric Hip

According to the Loder classification, which of the following defines an unstable slipped capital femoral epiphysis (SCFE)?

. A physeal slip angle greater than 50 degrees
. The inability of the patient to ambulate, with or without crutches
. The presence of a hip joint effusion on ultrasound
. Symptom duration of less than 3 weeks
. Slip displacement greater than 50% of the femoral neck width

Correct Answer & Explanation

. A physeal slip angle greater than 50 degrees

Explanation

The Loder classification defines an unstable SCFE as the inability to ambulate, even with the use of crutches. Unstable slips are associated with a significantly higher rate of avascular necrosis compared to stable slips.

Question 2808

Topic: 4. Pediatrics

A 4-week-old female infant undergoes a screening ultrasound of the hips due to a breech presentation. The coronal view reveals an alpha angle of 52 degrees and a beta angle of 65 degrees. According to the Graf classification, what does this alpha angle indicate?

. A normal, mature hip (Type I)
. A physiologically immature or mildly dysplastic hip (Type II)
. A subluxated hip (Type III)
. A completely dislocated hip (Type IV)
. A septic hip joint

Correct Answer & Explanation

. A normal, mature hip (Type I)

Explanation

An alpha angle between 50 and 59 degrees corresponds to a Graf Type II hip, which indicates physiologic immaturity or mild dysplasia. An alpha angle greater than 60 degrees is considered normal (Type I).

Question 2809

Topic: Pediatric Hip

Which of the following patient profiles represents the strongest absolute indication for prophylactic in situ pinning of the contralateral hip in a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE)?

. A 12-year-old boy with a stable SCFE
. An 11-year-old girl with primary hypothyroidism
. A 14-year-old boy with an unstable SCFE
. A 13-year-old boy with a body mass index > 95th percentile
. A 15-year-old girl with an acute-on-chronic SCFE

Correct Answer & Explanation

. A 12-year-old boy with a stable SCFE

Explanation

Endocrinopathies, such as hypothyroidism or renal osteodystrophy, are strong indications for prophylactic contralateral pinning in SCFE. These patients have a significantly elevated risk of developing bilateral disease.

Question 2810

Topic: 4. Pediatrics

In the operative management of pediatric supracondylar humerus fractures, biomechanical studies have shown that which of the following pin configurations provides the greatest torsional stability?

. Two divergent lateral pins
. Two parallel lateral pins
. Three parallel lateral pins
. Crossed medial and lateral pins
. A single intramedullary Kirschner wire

Correct Answer & Explanation

. Two divergent lateral pins

Explanation

Crossed medial and lateral pins provide the greatest torsional stability for supracondylar humerus fractures. However, lateral-only pin constructs are often preferred clinically to eliminate the risk of iatrogenic ulnar nerve injury.

Question 2811

Topic: Pediatric Hip

In the closed or open reduction of late-presenting developmental dysplasia of the hip (DDH), which of the following factors is most strongly associated with an increased risk of developing avascular necrosis (AVN) of the femoral head?

. Release of the transverse acetabular ligament
. Concomitant psoas tenotomy
. Post-reduction immobilization in excessive hip abduction
. Capsulorrhaphy during open reduction
. Excision of the ligamentum teres

Correct Answer & Explanation

. Release of the transverse acetabular ligament

Explanation

Immobilization of the hip in excessive abduction (the "frog-leg" position) causes mechanical compression of the retinacular vessels against the acetabular rim. This is the primary iatrogenic risk factor for AVN in the treatment of DDH.

Question 2812

Topic: Pediatric Hip

A 13-year-old boy undergoes single-screw in situ pinning for a stable slipped capital femoral epiphysis (SCFE). Seven months postoperatively, he complains of worsening hip stiffness and global pain. Radiographs reveal symmetric hip joint space narrowing to less than 2 mm with no signs of hardware failure. What is the most likely diagnosis?

. Avascular necrosis
. Deep surgical site infection
. Implant failure with joint penetration
. Chondrolysis
. Femoral neck stress fracture

Correct Answer & Explanation

. Avascular necrosis

Explanation

Chondrolysis is a devastating complication of SCFE characterized by acute cartilage necrosis, presenting with marked stiffness, pain, and symmetric joint space narrowing on radiographs. It is strongly associated with unrecognized joint penetration by the hardware.

Question 2813

Topic: 4. Pediatrics

A newborn presents with bilateral, rigid, and irreducible hip dislocations. Physical examination also reveals bilateral clubfeet and fixed knee extension contractures. The infant otherwise has normal spinal anatomy on ultrasound. What is the most likely diagnosis?

. Typical developmental dysplasia of the hip
. Arthrogryposis multiplex congenita
. Developmental coxa vara
. Slipped capital femoral epiphysis
. Legg-Calve-Perthes disease

Correct Answer & Explanation

. Typical developmental dysplasia of the hip

Explanation

Teratologic hip dislocations are present at birth, typically rigid and irreducible, and associated with underlying neuromuscular or syndromic conditions such as arthrogryposis multiplex congenita or myelomeningocele.

Question 2814

Topic: Pediatric Hip

A 14-year-old boy with a severe, chronic slipped capital femoral epiphysis presents with severe impingement. The surgeon plans a corrective osteotomy at the apex of the deformity to restore anatomy. Which of the following procedures is an intracapsular osteotomy of the femoral neck that provides excellent correction but historically carries the highest risk of avascular necrosis?

. Southwick osteotomy
. Imhauser osteotomy
. Kramer osteotomy
. Dunn procedure
. Salter osteotomy

Correct Answer & Explanation

. Southwick osteotomy

Explanation

The Dunn procedure is an intracapsular, cuneiform osteotomy performed directly at the femoral neck to reduce a severe SCFE. Because it is intracapsular, it disrupts the retinacular blood supply and historically has a high risk of avascular necrosis.

Question 2815

Topic: 4. Pediatrics

A 4-week-old female infant is being treated with a Pavlik harness for a dislocated left hip. At the 2-week follow-up, the mother notes the child is not moving her left leg. On exam, the infant lacks active knee extension but has normal ankle movement. What is the most likely cause?

. Femoral nerve palsy
. Sciatic nerve palsy
. Obturator nerve palsy
. Avascular necrosis of the femoral head
. Hip joint infection

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment, typically due to hyperflexion of the hip. Treatment involves adjusting the harness to reduce flexion, which usually leads to spontaneous recovery.

Question 2816

Topic: Pediatric Hip

A 12-year-old obese boy presents to the emergency department unable to bear weight on his right leg after a minor fall. Radiographs reveal a severe, posterior slip of the right capital femoral epiphysis. What is the recommended definitive management?

. Closed reduction and spica casting
. Gentle closed reduction and in-situ pinning with a single screw
. Open reduction and internal fixation through a surgical dislocation approach
. In-situ pinning with a single screw without reduction
. Subtrochanteric osteotomy

Correct Answer & Explanation

. Closed reduction and spica casting

Explanation

Unstable SCFE has a high risk of AVN. Recent literature supports open reduction and internal fixation utilizing a surgical hip dislocation approach (modified Dunn procedure) to decompress the intracapsular hematoma and restore anatomy.

Question 2817

Topic: Pediatric Hip

A 13-year-old boy undergoes in-situ pinning for a left-sided SCFE. Which of the following is the strongest indication for prophylactic pinning of the contralateral asymptomatic hip?

. Obesity (BMI > 95th percentile)
. Age greater than 14 years
. Male sex
. Endocrine disorder (e.g., hypothyroidism)
. Slips greater than 50 degrees

Correct Answer & Explanation

. Obesity (BMI > 95th percentile)

Explanation

Endocrine disorders, such as hypothyroidism or renal osteodystrophy, strongly predispose patients to bilateral SCFE. Prophylactic pinning of the contralateral hip is highly recommended in this population.

Question 2818

Topic: Pediatric Upper Extremity & Spine

A 5-year-old boy sustains a completely displaced, extension-type supracondylar humerus fracture. On presentation, the hand is pink and warm, but the radial pulse is absent. After urgent closed reduction and percutaneous pinning, the hand remains pink and warm, and the pulse remains absent. What is the most appropriate next step in management?

. Urgent exploration of the brachial artery
. Observation and admission for close neurovascular monitoring
. Immediate arterial bypass grafting
. Angiography of the upper extremity
. Removal of pins and open reduction

Correct Answer & Explanation

. Urgent exploration of the brachial artery

Explanation

A 'pulseless pink hand' after reduction of a supracondylar fracture indicates adequate collateral perfusion. Observation and close monitoring are appropriate, as the pulse often returns within a few days to weeks.

Question 2819

Topic: 4. Pediatrics

According to the American Academy of Pediatrics (AAP) and AAOS, which of the following infants should routinely undergo a screening ultrasound for DDH at 6 weeks of age, regardless of clinical exam findings?

. A full-term male infant born via vaginal delivery to a mother with a history of DDH
. A preterm female infant born at 32 weeks gestation
. A full-term female infant born in the breech presentation
. A full-term male infant born with clubfoot
. A full-term female infant born via vertex delivery with no family history

Correct Answer & Explanation

. A full-term male infant born via vaginal delivery to a mother with a history of DDH

Explanation

Routine ultrasound screening at 6 weeks is recommended for infants with strong risk factors for DDH, specifically female sex with breech presentation, or a positive family history regardless of sex.

Question 2820

Topic: 4. Pediatrics

When evaluating a pelvic radiograph of a 12-month-old child for developmental dysplasia of the hip, an abnormal acetabular index would typically be greater than:

. 15 degrees
. 20 degrees
. 25 degrees
. 30 degrees
. 45 degrees

Correct Answer & Explanation

. 15 degrees

Explanation

In a normal infant around 1 year of age, the acetabular index should be less than 25 degrees. Values greater than 30 degrees are considered dysplastic and warrant intervention or close monitoring.

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