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4. Pediatrics MCQs

Practice Set 35 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 681

Topic: Pediatric Hip

A 6-week-old female infant is diagnosed with developmental dysplasia of the hip (DDH). Ultrasound confirms a dislocated right hip that is reducible. She is prescribed a Pavlik harness. Which of the following nerve palsies is most commonly associated with excessive hip flexion in this device?

. Obturator nerve
. Sciatic nerve
. Femoral nerve
. Superior gluteal nerve
. Lateral femoral cutaneous nerve

Correct Answer & Explanation

. Femoral nerve

Explanation

Femoral nerve palsy is the most common nerve injury associated with the Pavlik harness and occurs when the hips are maintained in hyperflexion. This manifests as an inability to actively extend the knee, requiring harness adjustment.

Question 682

Topic: Pediatric Hip

A 13-year-old obese male presents with a 3-week history of vague right knee pain and a limp. Physical examination reveals an antalgic gait and obligatory external rotation of the right hip during passive flexion. Which of the following is the most appropriate initial diagnostic imaging?

. Anteroposterior (AP) radiograph of the right knee
. MRI of the right hip
. Anteroposterior (AP) and frog-leg lateral radiographs of the pelvis
. Ultrasound of the right hip
. CT scan of the pelvis with 3D reconstruction

Correct Answer & Explanation

. Anteroposterior (AP) and frog-leg lateral radiographs of the pelvis

Explanation

The clinical presentation is highly suspicious for Slipped Capital Femoral Epiphysis (SCFE), which often presents with referred knee pain. AP and frog-leg lateral radiographs of the pelvis are the gold standard for initial diagnosis, allowing comparison of both hips.

Question 683

Topic: Pediatric Hip

A 4-month-old female infant is found to have asymmetric thigh skin folds and limited hip abduction on the left side. An ultrasound confirms a dislocated left hip with an alpha angle of 40 degrees. What is the standard first-line management?

. Reassurance and follow-up in 3 months
. Closed reduction and spica casting
. Application of a Pavlik harness
. Open reduction and Dega osteotomy
. Varus derotational osteotomy of the proximal femur

Correct Answer & Explanation

. Application of a Pavlik harness

Explanation

For Developmental Dysplasia of the Hip (DDH) in an infant under 6 months of age, the Pavlik harness is the primary standard of care. It maintains the hip in flexion and abduction to allow for natural remodeling of the acetabulum.

Question 684

Topic: 4. Pediatrics

When treating congenital talipes equinovarus (clubfoot) using the Ponseti method of serial casting, the deformities are corrected in a specific sequential order. Which component of the deformity is the last to be corrected, often requiring a percutaneous tenotomy?

. Cavus
. Adductus
. Varus
. Equinus
. Internal tibial torsion

Correct Answer & Explanation

. Equinus

Explanation

In the Ponseti method, the mnemonic CAVE dictates the order of correction: Cavus, Adductus, Varus, and finally Equinus. The equinus contracture frequently requires a percutaneous Achilles tenotomy for definitive correction.

Question 685

Topic: Pediatric Upper Extremity & Spine
A 5-year-old boy presents with a completely displaced posteromedial Gartland type III supracondylar humerus fracture. Which of the following neurologic structures is most at risk with this specific displacement pattern?
. Median nerve
. Anterior interosseous nerve
. Ulnar nerve
. Radial nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Radial nerve

Explanation

In a posteromedially displaced supracondylar fracture, the proximal fragment is displaced anterolaterally, putting the radial nerve at greatest risk. Posterolateral displacement places the median nerve and anterior interosseous nerve at highest risk.

Question 686

Topic: Pediatric Hip

In a 12-year-old boy presenting with a unilateral slipped capital femoral epiphysis (SCFE), which of the following is considered an absolute indication for prophylactic pinning of the contralateral hip?

. Age over 14
. Male sex
. Underlying endocrine disorder
. Modified Southwick angle less than 30 degrees
. Obesity greater than 99th percentile

Correct Answer & Explanation

. Underlying endocrine disorder

Explanation

Endocrine disorders, such as hypothyroidism or renal osteodystrophy, are strong indications for prophylactic pinning of the contralateral asymptomatic hip due to a very high risk of bilateral SCFE involvement.

Question 687

Topic: Pediatric Hip

A 4-month-old girl with developmental dysplasia of the hip (DDH) has been treated in a Pavlik harness for 3 weeks. Examination reveals an inability to actively extend her knee on the affected side. What is the most likely cause of this complication?

. Femoral nerve palsy due to excessive hip flexion
. Sciatic nerve palsy due to excessive hip abduction
. Obturator nerve palsy due to excessive internal rotation
. Transient synovitis
. Avascular necrosis of the femoral head

Correct Answer & Explanation

. Femoral nerve palsy due to excessive hip flexion

Explanation

Femoral nerve palsy is a recognized complication of the Pavlik harness if the hip is positioned in excessive hyperflexion. The harness must be adjusted or removed to resolve the compression and allow nerve recovery.

Question 688

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy presents with a completely displaced extension-type supracondylar humerus fracture. On arrival, his hand is pink, but the radial pulse is absent. After a satisfactory closed reduction and percutaneous pinning, the hand remains pink and warm with a capillary refill of less than 2 seconds, but the pulse remains absent on Doppler ultrasound. What is the most appropriate next step in management?

. Perform immediate brachial artery exploration
. Remove the pins and attempt an open reduction
. Admit for close clinical observation and serial neurovascular checks
. Perform an immediate CT angiogram of the upper extremity
. Administer intravenous heparin and consult vascular surgery

Correct Answer & Explanation

. Admit for close clinical observation and serial neurovascular checks

Explanation

A pink, pulseless hand after adequate reduction and stabilization of a supracondylar humerus fracture is generally managed with close clinical observation. Emergent exploration is indicated only if the hand is poorly perfused (white and pulseless) after reduction.

Question 689

Topic: 4. Pediatrics

A 6-year-old boy falls from monkey bars and sustains a heavily displaced extension-type supracondylar humerus fracture. On examination, he is unable to flex the interphalangeal joint of his thumb and the distal interphalangeal joint of his index finger. Which nerve is most likely injured?

. Radial nerve
. Ulnar nerve
. Anterior interosseous nerve
. Posterior interosseous nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior interosseous nerve

Explanation

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type pediatric supracondylar humerus fractures. It innervates the flexor pollicis longus and the flexor digitorum profundus to the index and middle fingers.

Question 690

Topic: Pediatric Hip

A 13-year-old obese male presents with right groin pain and a limp. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE). During in situ pinning with a single cannulated screw, which complication is most likely if the screw is placed in the anterosuperior quadrant of the femoral head?

. Chondrolysis
. Avascular necrosis (AVN)
. Femoral neck fracture
. Implant failure
. Labral tear

Correct Answer & Explanation

. Avascular necrosis (AVN)

Explanation

Placement of the screw in the anterosuperior quadrant of the femoral head risks penetration of the joint space and injury to the lateral epiphyseal vessels, leading to avascular necrosis. Screws should ideally be placed in the center-center position.

Question 691

Topic: Pediatric Hip

An infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). At the two-week follow-up, the mother notes the child is no longer actively extending the knee on the treated side. What is the most appropriate next step in management?

. Continue the harness as this is a normal finding
. Increase the flexion straps to 120 degrees
. Discontinue the harness temporarily and observe
. Switch to rigid spica casting
. Obtain an immediate MRI of the lumbar spine

Correct Answer & Explanation

. Discontinue the harness temporarily and observe

Explanation

Loss of active knee extension indicates a femoral nerve palsy, the most common nerve injury associated with Pavlik harness use due to hyperflexion. The harness must be temporarily discontinued to allow the nerve to recover.

Question 692

Topic: Pediatric Hip

A 13-year-old obese male presents with a 4-week history of left knee pain and an antalgic gait. Examination reveals obligatory external rotation of the left hip upon flexion. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE). What is the primary reason to perform single-screw in situ fixation over multiple-screw fixation?

. Decreased risk of chondrolysis
. Decreased risk of avascular necrosis
. Decreased risk of joint penetration
. Increased biomechanical stability
. Prevention of contralateral slip

Correct Answer & Explanation

. Decreased risk of joint penetration

Explanation

Single-screw fixation is the standard of care for a stable SCFE. Compared to multiple screws, a single screw provides adequate stability while significantly decreasing the risk of inadvertent joint penetration and subsequent chondrolysis.

Question 693

Topic: Pediatric Upper Extremity & Spine

A 13-year-old girl with adolescent idiopathic scoliosis (AIS) has a right thoracic curve of 35 degrees. She is Risser stage 1 and premenarchal. What is the most appropriate management?

. Observation with repeat radiographs in 6 months
. Physical therapy for core strengthening
. Full-time bracing (TLSO)
. Posterior spinal fusion
. Anterior spinal tethering

Correct Answer & Explanation

. Full-time bracing (TLSO)

Explanation

In a skeletally immature patient (Risser 0-2, premenarchal) with an AIS curve between 25 and 40 degrees, full-time bracing (e.g., Thoracolumbosacral orthosis) is the gold standard to prevent curve progression to surgical magnitude.

Question 694

Topic: 4. Pediatrics

When treating congenital talipes equinovarus (clubfoot) using the Ponseti method, what is the correct order of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adduction, Varus, Equinus

Explanation

The mnemonic CAVE dictates the sequence of correction in the Ponseti method: Cavus (first ray elevated), Adductus (forefoot adduction), Varus (hindfoot varus), and finally Equinus (hindfoot equinus, often requiring a percutaneous Achilles tenotomy).

Question 695

Topic: 4. Pediatrics

A 13-year-old obese boy presents with a 4-week history of left knee pain and an antalgic gait. Physical examination of the left hip reveals restricted internal rotation, and the hip obligatorily externally rotates during passive flexion. Radiographs demonstrate a widening and irregularity of the left proximal femoral physis. Following definitive surgical management, what is the most devastating common complication this patient faces?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Progressive leg length discrepancy
. Heterotopic ossification
. Ipsilateral femoral shaft fracture

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

Slipped capital femoral epiphysis (SCFE) is treated with in situ pinning. Avascular necrosis of the femoral head is the most devastating complication, often resulting from unstable slips or iatrogenic injury to the retinacular vessels during hardware placement.

Question 696

Topic: Pediatric Upper Extremity & Spine

A 6-year-old girl sustains a severely displaced, extension-type supracondylar fracture of the humerus. On examination, the hand is pink but the radial pulse is non-palpable. Capillary refill is less than 2 seconds. What is the most appropriate initial management?

. Immediate open anterior exploration of the brachial artery
. CT angiography of the upper extremity
. Closed reduction and percutaneous pinning
. Application of a long arm cast in 90 degrees of flexion
. Administration of a thrombolytic agent

Correct Answer & Explanation

. Closed reduction and percutaneous pinning

Explanation

In a "pink, pulseless" hand following a displaced supracondylar humerus fracture, the first step is urgent closed reduction and percutaneous pinning to restore alignment, which often relieves kinking of the brachial artery. Vascular exploration is generally reserved for hands that remain persistently ischemic (white) after fracture reduction.

Question 697

Topic: 4. Pediatrics

Fibrous dysplasia has been determined to be the result of a mutation in which gene:

. GNAS1
. FGFR3
. FBN1
. CFBA1
. COL1A1

Correct Answer & Explanation

. GNAS1

Explanation

Fibrous dysplasia has been determined to be the result of a postzygotic mutation in the GNAS1 (stimulatory G protein of adenylyl cyclase) gene. All of the cells that are descended from the cell with the mutation manifest features of the disease. FGFR3 (fibroblast growth factor receptor-3 protein) is abnormal in achondroplasia. FBN1 (fibrillin 1) is abnormal in Marfan syndrome. C FBA1 is abnormal in cleidocranial dysplasia. COL1A1 (collagen, type 1, alpha 1) is abnormal in osteogenesis imperfecta.

Question 698

Topic: 4. Pediatrics

Which of the following conditions is not associated with congenital contractures:

. Amyoplasia
. Diastrophic dysplasia
. Popliteal pterygium syndrome
. Larsen syndrome
. Down syndrome

Correct Answer & Explanation

. Down syndrome

Explanation

Down syndrome is the only condition listed that does not involve congenital contractures. Amyoplasia (or classic arthrogryposis) involves multiple contractures with normal intelligence and loss of flexion creases. Diastrophic dysplasia is a disorder of cartilage that includes contractures of many joints, as well as epiphyseal irregularity. Popliteal pterygium syndrome includes contractures with webbing across the flexor surfaces of the joints. Larsen syndrome involves multiple joint dislocations, as well as contractures.

Question 699

Topic: 4. Pediatrics

In which of the following clinical situations would it be most appropriate to recommend an anterior and posterior hemiepiphyseodesis of the convex side of a congenital scoliosis:

. A 12-year-old girl with a hemivertebra of L3.
. A 10-year-old boy with a hemivertebra of L3.
. A 5-year-old boy with a congenital bar of T3-4.
. A 5-year-old boy with a hemivertebra of T5.
. A 5-year-old boy with a hemivertebra of L5.

Correct Answer & Explanation

. A 5-year-old boy with a hemivertebra of T5.

Explanation

Hemiepiphyseodesis is most likely to produce progressive curve correction in patients under age 6. Hemiepiphyseodesis is not likely to result in improvement when there is no concave growth potential, as in the case of a congenital bar. In hemivertebra of the lumbosacral region, improvement is most likely when a hemivertebra resection is performed.

Question 700

Topic: 4. Pediatrics

Which of the following factors is associated with a decrease in the accuracy of measurement of congenital scoliosis:

. Increase in the size of the curve
. Decrease in the size of the curve
. Increased level of training in deformity surgery
. Film coned and centered on the deformity
. Use of the Ferguson technique instead of the C obb technique

Correct Answer & Explanation

. Increase in the size of the curve

Explanation

Measurement of congenital scoliosis has an intraobserver variation of 8°. Measurement accuracy decreases with decreased level of training, increased curve size, and decreased clarity of the endpoints. A coned and centered film would give better detail.

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