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4. Pediatrics MCQs

Practice Set 106 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 2101

Topic: Pediatric Hip

In a patient presenting with a unilateral Slipped Capital Femoral Epiphysis (SCFE), which of the following risk factors is the strongest clinical indication for performing a prophylactic in situ pinning of the asymptomatic contralateral hip?

. Patient age greater than 14 years
. Male gender
. Presence of an underlying endocrinopathy (e.g., hypothyroidism)
. Obesity (BMI > 95th percentile)
. Severe slip angle (> 50 degrees) on the affected side

Correct Answer & Explanation

. Presence of an underlying endocrinopathy (e.g., hypothyroidism)

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is widely recommended and strongly indicated in patients with underlying endocrine disorders (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy), as their risk of developing a contralateral slip can exceed 50-100%.

Question 2102

Topic: Pediatric Lower Extremity

When treating an infant with idiopathic clubfoot (talipes equinovarus) utilizing the Ponseti method of serial casting, the components of the deformity must be addressed in a specific order to prevent midfoot breach and achieve optimal correction. What is the correct sequence of deformity correction?

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

Correct Answer & Explanation

. Cavus, Varus, Adduction, Equinus

Explanation

The Ponseti method dictates a strict sequence of correction summarized by the mnemonic CAVE: Cavus (corrected first by elevating the first ray), Adduction (abducting the forefoot with counter-pressure on the head of the talus), Varus (which corrects automatically as the midfoot is abducted), and finally Equinus (corrected last, often requiring a percutaneous Achilles tenotomy).

Question 2103

Topic: Pediatric Hip

A 12-year-old boy is diagnosed with a stable left Slipped Capital Femoral Epiphysis (SCFE). Which of the following patient characteristics is an absolute indication for prophylactic in-situ pinning of the contralateral asymptomatic right hip?

. Male gender
. Severe obesity (BMI > 95th percentile)
. Presence of an underlying endocrine disorder
. Bone age greater than 14 years
. Positive family history of SCFE

Correct Answer & Explanation

. Presence of an underlying endocrine disorder

Explanation

While there is debate regarding routine prophylactic pinning in idiopathic SCFE, the presence of an underlying endocrine disorder (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) or prior radiation therapy is an absolute indication for prophylactic pinning of the contralateral hip due to a remarkably high rate (up to 50-100%) of bilateral involvement.

Question 2104

Topic: Pediatric Hip

A 3-year-old girl is diagnosed with a neglected left Developmental Dysplasia of the Hip (DDH). Radiographs confirm a completely dislocated, high-riding femoral head with a false acetabulum. What is the most appropriate surgical management?

. Closed reduction and spica casting
. Open reduction and spica casting alone
. Open reduction with a femoral shortening osteotomy and pelvic osteotomy
. Pavlik harness application
. Hip arthrodesis

Correct Answer & Explanation

. Open reduction with a femoral shortening osteotomy and pelvic osteotomy

Explanation

In older children (typically > 2-3 years) with neglected, high-riding DDH, open reduction alone carries an unacceptably high rate of avascular necrosis (AVN) due to severe soft tissue tension. A femoral shortening osteotomy is required to reduce the tension on the hip joint, and a concomitant pelvic osteotomy (e.g., Salter or Pemberton) is almost always necessary to correct the underlying severe acetabular dysplasia.

Question 2105

Topic: Pediatric Hip

A 12-year-old obese male is diagnosed with a unilateral left Slipped Capital Femoral Epiphysis (SCFE). Which of the following is the strongest indication for prophylactic pinning of the asymptomatic right hip?

. Male gender
. Age over 14 years
. Body mass index > 35
. Underlying endocrine disorder
. Family history of SCFE

Correct Answer & Explanation

. Underlying endocrine disorder

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial for idiopathic cases but is strongly indicated in patients with underlying endocrine disorders (e.g., hypothyroidism, panhypopituitarism, renal osteodystrophy) or prior radiation therapy, as they have a near 100% risk of bilateral involvement.

Question 2106

Topic: Pediatric Lower Extremity

During the Ponseti method for correcting idiopathic clubfoot (talipes equinovarus), the manipulation sequence dictates a highly specific order of correction. Which of the following components of the deformity is corrected FIRST?

. Equinus
. Hindfoot varus
. Forefoot adduction
. Midfoot cavus
. Tibial internal torsion

Correct Answer & Explanation

. Midfoot cavus

Explanation

The Ponseti method corrects clubfoot deformities in the mnemonic sequence 'CAVE': Cavus, Adduction, Varus, Equinus. The very first step is to elevate the first ray to supinate the forefoot, thereby correcting the midfoot Cavus. Next, forefoot adduction and hindfoot varus are corrected simultaneously by abducting the foot around the head of the talus.

Question 2107

Topic: Pediatric Lower Extremity

During the initial phase of the Ponseti method for correcting idiopathic clubfoot in an infant, the cavus deformity must be addressed first. Which specific anatomical structure serves as the fulcrum for the thumb of the physician while supinating the forefoot to correct the cavus?

. The calcaneocuboid joint
. The lateral malleolus
. The head of the talus
. The navicular tuberosity
. The sustentaculum tali

Correct Answer & Explanation

. The head of the talus

Explanation

In the Ponseti technique, the first step is to correct the cavus by supinating the forefoot and elevating the first ray. To achieve this, the physician's thumb must be placed on the lateral aspect of the head of the talus to act as a fulcrum while the forefoot is abducted. Placing pressure on the calcaneocuboid joint (a common mistake) prevents the calcaneus from abducting and leads to a rocker-bottom deformity.

Question 2108

Topic: 4. Pediatrics

A 13-year-old obese male presents with a 3-week history of left knee and thigh pain. He is able to bear weight but walks with an externally rotated gait. Radiographs reveal widening of the left proximal femoral physis, and a line drawn along the superior neck of the femur (Klein's line) fails to intersect the epiphysis. Which of the following is the standard of care for this condition?

. Closed reduction with internal rotation, followed by a hip spica cast
. In situ percutaneous pinning with a single cannulated screw
. Open reduction and internal fixation through an anterior approach
. Subtrochanteric derotation osteotomy
. Prophylactic pinning of the contralateral hip only

Correct Answer & Explanation

. In situ percutaneous pinning with a single cannulated screw

Explanation

The patient has a stable Slipped Capital Femoral Epiphysis (SCFE) (he can bear weight). Klein's line missing the epiphysis is the classic radiographic sign. The gold standard treatment for stable SCFE is in situ percutaneous pinning with a single central cannulated screw to prevent further slip and promote physeal closure. Closed reduction is contraindicated due to the high risk of osteonecrosis.

Question 2109

Topic: Pediatric Hip
In the Herring Lateral Pillar Classification of Legg-Calvรฉ-Perthes disease, a Group B hip is defined by what percentage of lateral pillar height maintenance on an AP radiograph during the fragmentation stage?
. > 100%
. > 50% but < 100%
. < 50%
. > 25% but < 50%
. > 75%

Correct Answer & Explanation

. < 50%

Explanation

The Herring Lateral Pillar classification divides Perthes disease into three main groups based on the height of the lateral pillar of the capital femoral epiphysis. Group A has no involvement (100% height maintained). Group B has > 50% of the lateral pillar height maintained. Group C has < 50% height maintained.

Question 2110

Topic: Pediatric Hip

What is the most significant risk factor for the development of avascular necrosis (AVN) of the femoral head following a slipped capital femoral epiphysis (SCFE)?

. Obesity
. Male sex
. Endocrine disorders
. Instability of the slip (inability to bear weight)
. Bilateral involvement

Correct Answer & Explanation

. Instability of the slip (inability to bear weight)

Explanation

The Loder classification divides SCFE into stable (able to bear weight with or without crutches) and unstable (unable to bear weight). Unstable SCFE has a significantly higher rate of avascular necrosis (AVN), ranging from 20% to 50%, compared to stable SCFE which has an AVN rate of nearly 0%.

Question 2111

Topic: Pediatric Hip

A 4-month-old infant is placed in a Pavlik harness for the treatment of developmental dysplasia of the hip (DDH). Which of the following positions or strap adjustments places the infant at the highest risk for developing avascular necrosis (AVN) of the femoral head?

. Excessive hip flexion by over-tightening the anterior straps
. Excessive hip abduction by over-tightening the posterior straps
. Excessive hip adduction by loosening the posterior straps
. Excessive hip extension by loosening the anterior straps
. Excessive knee flexion by over-tightening the foot stirrups

Correct Answer & Explanation

. Excessive hip abduction by over-tightening the posterior straps

Explanation

Excessive abduction in a Pavlik harness places the hip at high risk for avascular necrosis (AVN) due to occlusion of the retinacular vessels against the acetabular rim. Excessive hip flexion places the infant at risk for femoral nerve palsy.

Question 2112

Topic: Pediatric Hip

A 12-year-old obese male undergoes in-situ single screw fixation for a stable slipped capital femoral epiphysis (SCFE). Which of the following technical errors or clinical factors is most strongly associated with the development of postoperative chondrolysis?

. Patient weight greater than the 95th percentile
. Unrecognized intra-articular penetration by the hardware
. Delay in surgical fixation of more than 24 hours
. Use of a fully threaded screw instead of a partially threaded screw
. Performing bilateral prophylactic pinning

Correct Answer & Explanation

. Unrecognized intra-articular penetration by the hardware

Explanation

Chondrolysis is a devastating complication of SCFE characterized by acute loss of articular cartilage space. The most strongly associated iatrogenic cause is unrecognized intra-articular hardware penetration during pinning. To prevent this, the 'approach-withdraw' technique under fluoroscopy must be used to ensure the screw tip is fully within the epiphysis.

Question 2113

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents with a completely displaced, extension-type supracondylar humerus fracture (Gartland Type III). On initial examination, the hand is pale, pulseless, and cool. After a gentle closed reduction and percutaneous pinning in the OR, the hand becomes pink, warm, and has a capillary refill of 1.5 seconds, but the radial pulse remains absent on Doppler. What is the most appropriate next step in management?
. Immediate open exploration of the brachial artery in the antecubital fossa
. Perform an intraoperative formal angiogram
. Observation and hospital admission for close serial neurovascular monitoring
. Remove the pins, slightly extend the elbow, and repin the fracture
. Perform a prophylactic volar forearm fasciotomy

Correct Answer & Explanation

. Observation and hospital admission for close serial neurovascular monitoring

Explanation

The management of a 'pink, pulseless' hand following the successful reduction and pinning of a pediatric supracondylar humerus fracture is observation. If the hand is well-perfused (warm, pink, brisk capillary refill < 2 seconds), the limb is viable. The absence of a palpable or Doppler pulse is typically due to localized vasospasm, which resolves over hours to days. Emergent vascular exploration is indicated if the hand remains 'pale and pulseless' (poorly perfused) after reduction.

Question 2114

Topic: Pediatric Upper Extremity & Spine
A 5-year-old child sustains a Gartland type III supracondylar humerus fracture. Post-injury examination reveals an isolated anterior interosseous nerve (AIN) palsy. What is the most characteristic clinical finding associated with this specific nerve injury?
. Inability to cross the fingers
. Weakness of thumb interphalangeal (IP) joint and index finger distal interphalangeal (DIP) joint flexion
. Inability to extend the wrist
. Numbness over the volar aspect of the index finger
. Weakness of the abductor pollicis brevis

Correct Answer & Explanation

. Weakness of thumb interphalangeal (IP) joint and index finger distal interphalangeal (DIP) joint flexion

Explanation

The anterior interosseous nerve (AIN) 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 radial half of the flexor digitorum profundus (FDP to the index and middle fingers), and the pronator quadratus. An AIN palsy presents with weakness in flexing the thumb IP joint and index finger DIP joint, clinically resulting in the inability to form an 'OK' sign. Because it is purely motor, there is no sensory deficit.

Question 2115

Topic: Pediatric Hip

A 4-month-old female infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During the follow-up visit, the parents report she has stopped kicking her right leg. Examination reveals decreased active extension of the right knee, but intact ankle and toe movements. What is the most likely cause?

. Femoral nerve palsy from excessive hip flexion
. Sciatic nerve palsy from excessive hip flexion
. Obturator nerve palsy from excessive hip abduction
. Transient synovitis of the hip
. Slipped capital femoral epiphysis

Correct Answer & Explanation

. Femoral nerve palsy from excessive hip flexion

Explanation

The most common nerve injury associated with the use of a Pavlik harness is femoral nerve palsy, typically caused by hyperflexion of the hips. This leads to an inability to actively extend the knee (quadriceps weakness). It usually resolves once the flexion is decreased or the harness is temporarily discontinued. Sciatic nerve palsy is exceedingly rare in this context.

Question 2116

Topic: Pediatric Hip

A 13-year-old obese boy presents with left knee pain and an antalgic gait. Examination shows obligate external rotation of the left hip during passive flexion. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE). What is the primary physiological reason to perform an in-situ pinning rather than attempting an aggressive closed reduction before pinning?

. To prevent premature physeal closure
. To decrease the risk of avascular necrosis (AVN)
. To avoid limb length discrepancy
. To prevent contralateral SCFE
. To minimize the risk of chondrolysis

Correct Answer & Explanation

. To decrease the risk of avascular necrosis (AVN)

Explanation

The primary danger of forcefully reducing a slipped capital femoral epiphysis (SCFE) is the disruption of the fragile terminal branches of the medial femoral circumflex artery (retinacular vessels), which dramatically increases the risk of avascular necrosis (AVN) of the femoral head. Therefore, in-situ pinning without aggressive reduction is the standard of care for a stable SCFE.

Question 2117

Topic: Pediatric Hip

According to current guidelines, which of the following is considered the strongest indication for prophylactic in situ pinning of the asymptomatic contralateral hip in a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE)?

. Age greater than 14 years in males
. Presentation with a stable SCFE
. Concomitant diagnosis of renal osteodystrophy
. Modified Oxford Bone Age Score of 22
. Closed triradiate cartilage

Correct Answer & Explanation

. Concomitant diagnosis of renal osteodystrophy

Explanation

Prophylactic pinning of the contralateral hip in unilateral SCFE is strongly recommended in patients with endocrine or metabolic disorders (e.g., renal osteodystrophy, hypothyroidism, panhypopituitarism) due to the exceedingly high rate of bilateral involvement (up to 100% in some series). Other indications include young chronologic age or skeletal age (modified Oxford Bone Age score <16), and history of radiation therapy. A score of 22 and closed triradiate cartilage indicate a mature skeleton with low risk of subsequent SCFE.

Question 2118

Topic: Pediatric Hip

An infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At the 2-week follow-up, the parents report the infant is not kicking the left leg. On exam, there is an absent patellar reflex and profound weakness in knee extension on the left side. What specific positional error of the Pavlik harness is the most likely cause of this complication?

. Excessive abduction of the hip
. Inadequate flexion of the hip (less than 90 degrees)
. Excessive flexion of the hip (greater than 120 degrees)
. Excessive internal rotation of the hip
. Inadequate abduction of the hip

Correct Answer & Explanation

. Excessive flexion of the hip (greater than 120 degrees)

Explanation

The infant is presenting with an iatrogenic femoral nerve palsy, a known complication of Pavlik harness treatment. This is caused by excessive flexion of the hip (typically greater than 120 degrees), which causes the anterior strap to compress the femoral nerve against the pelvic brim. Treatment involves loosening the anterior straps to reduce flexion. Conversely, excessive abduction is associated with avascular necrosis of the femoral head.

Question 2119

Topic: 4. Pediatrics

A 4-year-old child presents with disproportionate short stature, a waddling gait, and normal facial features and intelligence. Radiographs demonstrate delayed epiphyseal ossification and platyspondyly with anterior tongue-like projections. What is the primary genetic mutation responsible for this condition?

. FGFR3
. COL1A1
. COMP
. RUNX2
. SOX9

Correct Answer & Explanation

. COMP

Explanation

The clinical scenario describes Pseudoachondroplasia. Unlike achondroplasia (which is caused by an FGFR3 mutation and presents with distinctive craniofacial features), pseudoachondroplasia patients have normal intelligence and normal faces. It is caused by a mutation in the Cartilage Oligomeric Matrix Protein (COMP) gene.

Question 2120

Topic: Pediatric Hip

In the management of a patient with a unilateral Slipped Capital Femoral Epiphysis (SCFE), prophylactic in situ pinning of the contralateral asymptomatic hip is most strongly indicated in which of the following scenarios?

. A 13-year-old obese male with idiopathic SCFE
. A 10-year-old female with idiopathic SCFE
. A 12-year-old male with SCFE secondary to primary hypothyroidism
. A 14-year-old male with a positive family history of SCFE
. A 15-year-old female with an acute-on-chronic SCFE

Correct Answer & Explanation

. A 12-year-old male with SCFE secondary to primary hypothyroidism

Explanation

Prophylactic contralateral pinning is highly recommended for patients with endocrine or metabolic disorders (e.g., hypothyroidism, renal osteodystrophy) due to the extremely high risk of bilateral involvement. Other relative indications include open triradiate cartilage or age <10 years.

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