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4. Pediatrics MCQs

Practice Set 323 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 6441

Topic: 4. Pediatrics

A 13-year-old obese male presents with a 3-week history of left groin and knee pain. On examination, his left hip obligatorily externally rotates during passive flexion. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE). He undergoes in situ pinning with a single cannulated screw. What is the primary biological and biomechanical goal of this specific intervention?

. To anatomically reduce the epiphysis to prevent femoroacetabular impingement
. To prevent further slippage and promote premature physeal closure
. To decompress the joint space and prevent avascular necrosis
. To restore the normal neck-shaft angle
. To stimulate remodeling of the anterior femoral metaphysis

Correct Answer & Explanation

. To prevent further slippage and promote premature physeal closure

Explanation

Correct Answer: To prevent further slippage and promote premature physeal closureThe standard of care for a stable Slipped Capital Femoral Epiphysis (SCFE) is in situ pinning. The primary goal is to stabilize the physis to prevent further displacement (slippage) of the epiphysis and to promote early closure (epiphysiodesis) of the proximal femoral physis. Attempting anatomical reduction in a stable SCFE significantly increases the risk of avascular necrosis (AVN) and is generally contraindicated.

Question 6442

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy sustains a widely displaced extension-type supracondylar humerus fracture after falling from the monkey bars. Which of the following physical examination findings is most indicative of the most commonly associated nerve injury in this specific fracture pattern?

. Inability to extend the metacarpophalangeal joints
. Loss of sensation over the dorsal first web space
. Inability to flex the distal interphalangeal joint of the index finger
. Weakness in finger abduction and adduction
. Loss of sensation over the volar aspect of the small finger

Correct Answer & Explanation

. Inability to flex the distal interphalangeal joint of the index finger

Explanation

Correct Answer: Inability to flex the distal interphalangeal joint of the index fingerThe median nerve, specifically its anterior interosseous nerve (AIN) branch, is the most commonly injured nerve in extension-type supracondylar humerus fractures. The AIN is a pure motor nerve that innervates the flexor pollicis longus (FPL), the pronator quadratus, and the flexor digitorum profundus (FDP) to the index and middle fingers. Injury results in the inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger (loss of the 'A-OK' sign).

Question 6443

Topic: 4. Pediatrics

A 6-year-old boy is brought to the clinic by his parents due to a persistent, painless limp that has worsened over the past two months. He has no history of fever or recent illness. Radiographs of the pelvis reveal sclerosis and fragmentation of the proximal femoral epiphysis. What is the underlying pathophysiology of this patient's condition?

. Bacterial seeding of the joint space
. Idiopathic avascular necrosis of the femoral head
. Post-viral inflammatory effusion
. Physeal failure due to excessive shear stress
. Congenital shallow acetabulum

Correct Answer & Explanation

. Idiopathic avascular necrosis of the femoral head

Explanation

Correct Answer: Idiopathic avascular necrosis of the femoral headThe clinical vignette describes Legg-Calve-Perthes (LCP) disease, which typically presents in children aged 4-8 years as a painless limp. The underlying pathophysiology is idiopathic avascular necrosis (osteonecrosis) of the proximal femoral epiphysis. Radiographic stages progress from initial sclerosis to fragmentation, reossification, and eventually remodeling.

Question 6444

Topic: 4. Pediatrics

A 13-year-old obese male presents with a 3-week history of right groin pain and a limp. On examination, he has an obligate external rotation of the right hip during passive flexion. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE). He undergoes in situ pinning with a single cannulated screw. Which of the following is the most critical technical objective during this procedure to minimize the risk of chondrolysis and avascular necrosis?

. Achieving anatomical reduction of the epiphysis prior to pinning
. Placing the screw in the anterior-superior quadrant of the femoral head
. Ensuring the screw threads cross the physis and engage the center of the epiphysis without joint penetration
. Performing a prophylactic capsulotomy to decompress the joint
. Using a minimum of three screws to provide rotational stability

Correct Answer & Explanation

. Ensuring the screw threads cross the physis and engage the center of the epiphysis without joint penetration

Explanation

Correct Answer: CFor a stable SCFE, the gold standard treatment is in situ pinning with a single cannulated screw. The goal is to stabilize the physis and prevent further slippage. The screw should be placed in the center-center position of the epiphysis. Penetration of the joint space by the hardware is a major risk factor for chondrolysis, while aggressive attempts at anatomical reduction (especially in stable slips) significantly increase the risk of avascular necrosis (AVN).

Question 6445

Topic: 4. Pediatrics

An infant is born with idiopathic congenital talipes equinovarus (clubfoot). The pediatric orthopedic surgeon initiates treatment using the Ponseti method of serial casting. According to the Ponseti principles, what is the correct sequence of deformity correction?

. Equinus, Varus, Adductus, Cavus
. Cavus, Adductus, Varus, Equinus
. Adductus, Cavus, Equinus, Varus
. Varus, Cavus, Adductus, Equinus
. Equinus, Cavus, Varus, Adductus

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

Correct Answer: BThe Ponseti method is the gold standard for treating clubfoot. The deformities must be corrected in a specific sequence, remembered by the acronym CAVE: Cavus (elevating the first ray), Adductus (abducting the forefoot), Varus (correcting hindfoot varus, which corrects simultaneously with adductus), and finally Equinus (dorsiflexing the ankle). The equinus is often the last deformity to be corrected and frequently requires a percutaneous Achilles tenotomy.

Question 6446

Topic: 4. Pediatrics

A 13-year-old obese male presents with a painful limp and obligate external rotation of the hip during passive flexion. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE). The surgeon recommends in situ pinning rather than an anatomical closed reduction. What is the primary rationale for avoiding forceful closed reduction in this patient?

. High risk of rapidly progressive chondrolysis
. High risk of iatrogenic avascular necrosis of the femoral head
. Increased risk of inducing a contralateral slip
. Inability to achieve adequate hardware purchase in the epiphysis
. Risk of premature physeal closure leading to severe leg length discrepancy

Correct Answer & Explanation

. High risk of iatrogenic avascular necrosis of the femoral head

Explanation

Correct Answer: High risk of iatrogenic avascular necrosis of the femoral headThe standard of care for a stable Slipped Capital Femoral Epiphysis (SCFE) is in situ pinning. Forceful closed reduction of the displaced epiphysis places the tenuous retinacular blood supply (specifically the medial femoral circumflex artery branches) at extreme risk, significantly increasing the incidence of iatrogenic avascular necrosis (AVN). While premature physeal closure is an expected outcome of pinning, AVN is a devastating complication that must be avoided.

Question 6447

Topic: Pediatric Hip

A 12-year-old obese boy presents with a 3-week history of left knee pain and a painful limp. On physical examination, his left hip obligatorily externally rotates when passively flexed. Radiographs confirm a stable Slipped Capital Femoral Epiphysis (SCFE). What is the most appropriate immediate management for this patient?

. Closed reduction and spica casting
. Open reduction and internal fixation
. In situ percutaneous pinning
. Non-weight bearing and physical therapy
. Proximal femoral osteotomy

Correct Answer & Explanation

. In situ percutaneous pinning

Explanation

Correct Answer: In situ percutaneous pinningThe standard of care for a stable Slipped Capital Femoral Epiphysis (SCFE) is in situ percutaneous pinning with a single cannulated screw. This prevents further slippage of the epiphysis and promotes premature closure of the physis. Closed reduction is contraindicated as it significantly increases the risk of avascular necrosis of the femoral head.

Question 6448

Topic: 4. Pediatrics
A 9-year-old girl sustains a distal radius fracture. Radiographs demonstrate a fracture line that passes transversely through the physis and exits obliquely through the dorsal metaphysis, leaving the epiphysis intact. According to the Salter-Harris classification, what type of fracture is this?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

A Salter-Harris Type II fracture involves a fracture line that extends through the physis and exits through the metaphysis, creating a metaphyseal fragment (Thurston-Holland fragment). It is the most common type of physeal fracture. Type I involves only the physis; Type III involves the physis and epiphysis; Type IV involves the metaphysis, physis, and epiphysis; and Type V is a crush injury to the physis.

Question 6449

Topic: Pediatric Lower Extremity

A newborn male is diagnosed with idiopathic talipes equinovarus (clubfoot). The parents are counseled on the standard of care for initial management. Which of the following best describes the primary treatment modality?

. Immediate posteromedial release surgery
. Use of a Denis Browne splint
. Serial manipulation and casting using the Ponseti method
. Observation and stretching exercises by the parents
. Application of a Pavlik harness

Correct Answer & Explanation

. Serial manipulation and casting using the Ponseti method

Explanation

Correct Answer: Serial manipulation and casting using the Ponseti methodThe Ponseti method is the gold standard for the initial treatment of idiopathic clubfoot. It involves a specific sequence of serial manipulations and long-leg cast applications to gradually correct the cavus, adductus, varus, and equinus deformities (CAVE). A percutaneous Achilles tenotomy is often required as the final step to correct the equinus contracture.

Question 6450

Topic: Pediatric Hip

A 13-year-old obese male presents with a 3-week history of left knee pain and a noticeable limp. He denies any recent trauma. On physical examination, as the affected hip is passively flexed, the thigh obligatorily deviates into external rotation. Internal rotation of the hip is significantly limited. What is the most appropriate initial management for the suspected diagnosis?

. Closed reduction and spica casting
. Immediate open reduction and internal fixation
. In situ pinning of the proximal femoral epiphysis
. Non-weight bearing and observation
. Aspiration of the hip joint

Correct Answer & Explanation

. In situ pinning of the proximal femoral epiphysis

Explanation

Correct Answer: CThe patient's clinical presentation (obese adolescent, knee/thigh pain, limp, obligatory external rotation with hip flexion, and limited internal rotation) is classic for a Slipped Capital Femoral Epiphysis (SCFE). The standard of care for a stable SCFE is in situ pinning, typically with a single cannulated screw placed in the center of the epiphysis. This prevents further slippage and promotes premature closure of the physis. Closed reduction is contraindicated as it significantly increases the risk of avascular necrosis (AVN) of the femoral head.

Question 6451

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy sustains a widely displaced extension-type supracondylar humerus fracture after falling from monkey bars. Upon presentation, he has a pulseless, pink hand and is unable to make an 'OK' sign with his thumb and index finger. Which of the following neural structures is most likely injured?

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

Correct Answer & Explanation

. Anterior interosseous nerve

Explanation

Correct Answer: CThe anterior interosseous nerve (AIN), a motor branch of the median nerve, is the most frequently injured nerve in extension-type supracondylar humerus fractures. The AIN innervates the flexor pollicis longus (FPL), the flexor digitorum profundus (FDP) to the index and middle fingers, and the pronator quadratus. Injury to the AIN results in the inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger, leading to an inability to form the 'OK' sign. The ulnar nerve is more commonly injured in flexion-type supracondylar fractures or iatrogenically during medial pin placement.

Question 6452

Topic: Pediatric Hip

A 6-week-old female infant is currently being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up exam, the parents report the infant has stopped kicking her right leg. On exam, there is an absence of active knee extension on the right side. What is the most likely iatrogenic cause of this finding?

. Excessive abduction of the hip
. Hyperflexion of the hip
. Excessive adduction of the hip
. Over-tightening of the chest strap
. Prolonged positioning in extension

Correct Answer & Explanation

. Hyperflexion of the hip

Explanation

Femoral nerve palsy is the most common nerve injury associated with Pavlik harness use and typically presents with decreased active knee extension. It is usually caused by excessive hyperflexion of the hip and resolves once the anterior straps are loosened.

Question 6453

Topic: Pediatric Lower Extremity

A 2-week-old male is evaluated for rigid bilateral idiopathic clubfoot. According to the Ponseti method, what is the initial biomechanical step in the manipulative reduction before applying the first cast?

. Correcting the hindfoot varus
. Dorsiflexing the ankle to correct equinus
. Elevating the first ray to correct the cavus
. Pronating the entire forefoot
. Translating the calcaneus laterally

Correct Answer & Explanation

. Elevating the first ray to correct the cavus

Explanation

The Ponseti method follows a strict sequential correction of the CAVE deformity (Cavus, Adductus, Varus, Equinus). The first crucial step is correcting the cavus by elevating the first ray to align the forefoot with the hindfoot.

Question 6454

Topic: Pediatric Hip
In the management of a 7-year-old child with Legg-Calvรฉ-Perthes disease, which radiographic classification system, applied during the fragmentation phase, is recognized as the most reliable predictor of long-term hip prognosis?
. Catterall classification
. Salter-Thompson classification
. Herring Lateral Pillar classification
. Stulberg classification
. Waldenstrรถm stages

Correct Answer & Explanation

. Herring Lateral Pillar classification

Explanation

The Herring Lateral Pillar classification, which evaluates the height of the lateral third of the capital femoral epiphysis during the fragmentation phase, is the most accurate and widely used prognostic indicator for Legg-Calvรฉ-Perthes disease.

Question 6455

Topic: Pediatric Hip

A 6-week-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up ultrasound, the anterior strap is noted to be excessively tight, forcing the hip into hyperflexion. Which of the following complications is she at highest risk of developing due to this specific strap positioning?

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

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Excessive flexion in a Pavlik harness (caused by anterior straps being too tight) places the patient at risk for femoral nerve palsy by compressing the nerve against the inguinal ligament. In contrast, excessive abduction (posterior straps too tight) increases the risk of avascular necrosis of the femoral head.

Question 6456

Topic: Pediatric Hip

A 7-year-old boy is diagnosed with Legg-Calve-Perthes disease. When evaluating his pelvic radiographs, the treating orthopedic surgeon utilizes the Herring classification. Which specific anatomical feature is assessed in this classification system to determine the prognosis?

. Extent of subchondral fracture (crescent sign)
. Height of the lateral pillar of the capital femoral epiphysis
. Degree of metaphyseal cyst formation
. Percentage of femoral head coverage by the acetabulum
. Amount of medial joint space widening

Correct Answer & Explanation

. Height of the lateral pillar of the capital femoral epiphysis

Explanation

The Herring classification system for Legg-Calve-Perthes disease evaluates the height of the lateral pillar of the capital femoral epiphysis on an AP radiograph during the fragmentation stage. A preserved lateral pillar (>50% height) generally correlates with a better long-term outcome.

Question 6457

Topic: 4. Pediatrics

A 2-week-old infant is undergoing serial casting for congenital talipes equinovarus. The pediatric orthopedic surgeon aims to correct the cavus deformity as the first step of the Ponseti method. Which maneuver is required to achieve this specific initial correction?

. Supination of the forefoot and elevation of the first ray
. Pronation of the forefoot and depression of the first ray
. Dorsiflexion of the ankle with the knee in 90 degrees of flexion
. Abduction of the midfoot with firm counter-pressure on the calcaneus
. Plantarflexion of the first ray and eversion of the hindfoot

Correct Answer & Explanation

. Supination of the forefoot and elevation of the first ray

Explanation

The first step in the Ponseti method is correcting the cavus by elevating the first ray and supinating the forefoot to align it with the hindfoot. Pronation of the forefoot is a common error that actually worsens the cavus deformity.

Question 6458

Topic: Pediatric Hip

A 7-year-old boy presents with bilateral hip pain and a waddling gait. Radiographs reveal bilateral, symmetric fragmentation and flattening of the capital femoral epiphyses, along with irregularity of the acetabula. Radiographs of the spine are entirely normal. Which of the following is the most likely diagnosis?

. Legg-Calve-Perthes disease
. Multiple Epiphyseal Dysplasia
. Spondyloepiphyseal Dysplasia
. Meyer Dysplasia

Correct Answer & Explanation

. Multiple Epiphyseal Dysplasia

Explanation

Correct Answer: Multiple Epiphyseal DysplasiaMultiple Epiphyseal Dysplasia (MED) is characterized by delayed and irregular ossification of the epiphyses. It is distinguished from Legg-Calve-Perthes disease by its bilateral, symmetric nature and the presence of acetabular involvement (Perthes typically has a normal acetabulum initially and is often unilateral or asymmetric). The normal spine differentiates MED from Spondyloepiphyseal Dysplasia (SED), which features platyspondyly.

Question 6459

Topic: 4. Pediatrics

Which of the following genetic mutations is most commonly associated with the autosomal dominant form of Multiple Epiphyseal Dysplasia (MED)?

. COL2A1
. COMP
. FGFR3
. RUNX2

Correct Answer & Explanation

. COMP

Explanation

Correct Answer: COMPThe most common mutation in autosomal dominant Multiple Epiphyseal Dysplasia is in the COMP (Cartilage Oligomeric Matrix Protein) gene, located on chromosome 19. Mutations in COL2A1 are associated with Spondyloepiphyseal Dysplasia (SED). FGFR3 mutations cause Achondroplasia, and RUNX2 mutations cause Cleidocranial Dysplasia.

Question 6460

Topic: 4. Pediatrics

A 12-year-old patient with a known skeletal dysplasia presents with knee pain. A lateral radiograph of the knee reveals a 'double-layered' patella. This specific radiographic finding is considered pathognomonic for a mutation in which of the following genes?

. SLC26A2
. COMP
. COL2A1
. FGFR3

Correct Answer & Explanation

. SLC26A2

Explanation

Correct Answer: SLC26A2The 'double patella' sign (a double-layered appearance of the patella on a lateral radiograph) is highly characteristic of the autosomal recessive form of Multiple Epiphyseal Dysplasia (rMED), which is caused by mutations in the SLC26A2 gene (a diastrophic dysplasia sulfate transporter). While dominant forms (COMP) can occasionally show patellar abnormalities, the classic double patella is linked to SLC26A2.

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