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4. Pediatrics MCQs

Practice Set 137 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 2721

Topic: Pediatric Hip

A 12-year-old boy is scheduled for in situ pinning of a left-sided slipped capital femoral epiphysis. Prophylactic pinning of the asymptomatic right hip is most strongly recommended if the patient also has:

. Obesity
. Renal osteodystrophy
. A family history of SCFE
. A slip angle greater than 50 degrees on the left
. Open triradiate cartilage

Correct Answer & Explanation

. Obesity

Explanation

Prophylactic contralateral pinning is highly recommended in patients with endocrine or metabolic disorders, such as renal osteodystrophy or hypothyroidism, due to a very high risk of bilateral involvement.

Question 2722

Topic: Pediatric Hip

When performing a closed reduction and spica casting for a 9-month-old with developmental dysplasia of the hip, a percutaneous adductor tenotomy is often performed. The primary purpose of this tenotomy is to:

. Prevent posterior subluxation
. Increase the safe zone of Ramsey
. Decrease the risk of femoral nerve palsy
. Prevent superior migration of the femoral head
. Improve acetabular remodeling

Correct Answer & Explanation

. Prevent posterior subluxation

Explanation

The adductor tenotomy relieves medial tension, allowing for adequate abduction without excessive pressure on the femoral head. This widens the "safe zone" of Ramsey and minimizes the risk of avascular necrosis.

Question 2723

Topic: Pediatric Hip

A 3-month-old girl with DDH is treated with a Pavlik harness. During a follow-up visit, she is noted to have decreased active knee extension on the affected side. What is the most appropriate next step in management?

. Continue the harness as prescribed
. Loosen the anterior straps
. Loosen the posterior straps
. Discontinue the harness entirely
. Change to a rigid hip abduction orthosis

Correct Answer & Explanation

. Continue the harness as prescribed

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness caused by excessive hip flexion. Loosening the anterior straps reduces hyperflexion and typically allows for full recovery of the nerve.

Question 2724

Topic: Pediatric Hip

A 13-year-old obese boy presents to the emergency department with acute left groin pain and an inability to bear weight after a minor fall. Radiographs show a slipped capital femoral epiphysis. According to Loder's classification, what is the primary significance of his inability to bear weight?

. Increased risk of chondrolysis
. Increased risk of avascular necrosis (AVN)
. Indication for prophylactic pinning of the contralateral hip
. Need for an open reduction and internal fixation
. Increased likelihood of underlying endocrine abnormality

Correct Answer & Explanation

. Increased risk of chondrolysis

Explanation

Loder classified SCFE into stable (able to bear weight) and unstable (unable to bear weight). Unstable SCFE is associated with a significantly higher risk of avascular necrosis (up to 47%) compared to stable SCFE.

Question 2725

Topic: 4. Pediatrics

A 4-week-old female infant undergoes a screening hip ultrasound for a breech presentation. The alpha angle is measured at 65 degrees and the beta angle at 45 degrees. Which of the following is the most appropriate management?

. Application of a Pavlik harness
. Application of a rigid abduction orthosis
. Closed reduction and spica casting
. Reassurance and routine follow-up
. MRI of the hips

Correct Answer & Explanation

. Application of a Pavlik harness

Explanation

An alpha angle greater than 60 degrees and a beta angle less than 55 degrees represent a Graf type I (normal) hip. No treatment is required, and the parents can be reassured.

Question 2726

Topic: Pediatric Hip

Prophylactic pinning of the contralateral, asymptomatic hip in a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE) is most strongly indicated in which of the following scenarios?

. 13-year-old boy with a BMI of 35
. 11-year-old girl with primary hyperparathyroidism
. 14-year-old boy with a traumatic unstable SCFE
. 12-year-old boy with a family history of SCFE
. 10-year-old girl with a stable, mild SCFE

Correct Answer & Explanation

. 13-year-old boy with a BMI of 35

Explanation

Patients with underlying endocrine disorders (e.g., hyperparathyroidism, hypothyroidism, renal osteodystrophy) have a very high rate of developing bilateral SCFE. Prophylactic pinning of the contralateral hip is strongly recommended in these patients.

Question 2727

Topic: Pediatric Hip

An 18-month-old girl presents with a painless limp. Examination reveals a positive Galeazzi sign and limited abduction of the right hip. Radiographs confirm a dislocated right hip. Which of the following is the most appropriate definitive treatment?

. Pavlik harness
. Closed reduction and spica casting
. Open reduction and spica casting
. Open reduction and pelvic osteotomy
. Total hip arthroplasty

Correct Answer & Explanation

. Pavlik harness

Explanation

In a child older than 18 months with untreated DDH, closed methods generally fail. Open reduction is required, often combined with a pelvic osteotomy (e.g., Salter) to address the secondary acetabular dysplasia.

Question 2728

Topic: Pediatric Hip

A 12-year-old boy presents with an unstable slipped capital femoral epiphysis (SCFE). The surgeon plans to perform a capsulotomy and percutaneous in situ pinning. What is the primary rationale for performing an anterior capsulotomy in this setting?

. To improve the radiographic visualization of the epiphysis
. To reduce intracapsular pressure and potentially decrease the risk of AVN
. To facilitate an anatomic open reduction of the slip
. To prevent post-operative chondrolysis
. To allow for easier placement of a second screw

Correct Answer & Explanation

. To improve the radiographic visualization of the epiphysis

Explanation

Unstable SCFE is associated with a hemarthrosis that increases intracapsular pressure, potentially compromising epiphyseal blood flow. An anterior capsulotomy decompresses the joint and is thought to reduce the high risk of AVN.

Question 2729

Topic: 4. Pediatrics

A 6-week-old female infant is being treated with a Pavlik harness for a dislocated left hip. During a follow-up visit, the parents report that the child has stopped actively extending her left knee. On examination, there is decreased active knee extension and a diminished patellar reflex on the left. What is the most likely cause of this finding, and what is the appropriate management?

. Sciatic nerve palsy; order an urgent MRI
. Femoral nerve palsy; loosen the anterior straps of the harness
. Obturator nerve palsy; switch to a rigid abduction orthosis
. Avascular necrosis of the femoral head; immediate closed reduction
. Normal variant; continue current harness settings

Correct Answer & Explanation

. Sciatic nerve palsy; order an urgent MRI

Explanation

Hyperflexion in a Pavlik harness can compress the femoral nerve against the rim of the pelvis, leading to transient femoral nerve palsy. The appropriate management is to loosen the anterior straps to decrease hip flexion, which typically results in spontaneous resolution.

Question 2730

Topic: Pediatric Hip
A 4-week-old female infant born in the breech presentation undergoes ultrasound screening for developmental dysplasia of the hip (DDH). The coronal image reveals an alpha angle of 40 degrees and a beta angle of 80 degrees. According to the Graf classification, what is the best initial management for this patient?
. Reassurance and clinical follow-up in 4 weeks
. Repeat ultrasound at 3 months of age
. Application of a Pavlik harness
. Immediate closed reduction and spica casting
. Open reduction with an adductor tenotomy

Correct Answer & Explanation

. Application of a Pavlik harness

Explanation

An alpha angle of less than 60 degrees indicates dysplasia, and an angle of 40 degrees falls into Graf Type III (dislocated but reducible). The standard of care for a newborn to 6-month-old with a dysplastic or dislocated hip is the application of a Pavlik harness.

Question 2731

Topic: Pediatric Hip

A 13-year-old obese boy presents to the emergency department with acute severe right hip pain after a minor fall. He is completely unable to bear weight on the right leg, even with the use of crutches. Radiographs confirm a severe slipped capital femoral epiphysis (SCFE). Based on the Loder classification, this specific clinical presentation carries the highest risk for which of the following complications?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Premature physeal closure
. Contralateral SCFE within 6 months
. Cam-type femoroacetabular impingement

Correct Answer & Explanation

. Chondrolysis

Explanation

The Loder classification defines an unstable SCFE by the patient's inability to ambulate, with or without crutches. Unstable SCFE is associated with a markedly high rate of avascular necrosis (up to 50%), whereas stable SCFE rarely results in AVN.

Question 2732

Topic: Pediatric Hip

A 12-year-old girl is diagnosed with a unilateral stable slipped capital femoral epiphysis (SCFE). She has a known medical history of panhypopituitarism and renal osteodystrophy. When counseling the parents about surgical management, what is the primary indication for recommending prophylactic in situ pinning of the contralateral hip?

. Her age at presentation
. Her female gender
. Her underlying endocrine and metabolic disorder
. The stable classification of her current slip
. Her body mass index (BMI) over the 95th percentile

Correct Answer & Explanation

. Her age at presentation

Explanation

Patients with underlying endocrine disorders (e.g., hypothyroidism, renal osteodystrophy, panhypopituitarism) have an exceedingly high risk (up to 100%) of developing bilateral SCFE. Prophylactic pinning of the contralateral asymptomatic hip is strongly recommended in this population.

Question 2733

Topic: Pediatric Hip

During a closed reduction for developmental dysplasia of the hip (DDH) under general anesthesia in a 9-month-old, the hip reduces at 100 degrees of flexion and 60 degrees of abduction. However, it redislocates when abduction is reduced to 40 degrees. The safe zone of Ramsey is determined to be narrow. Which of the following is the best next step to safely enlarge this zone?

. Perform a percutaneous Achilles tendon lengthening
. Perform a percutaneous adductor longus tenotomy
. Proceed immediately to a femoral shortening osteotomy
. Cast the child in 80 degrees of abduction
. Perform an iliopsoas tenotomy

Correct Answer & Explanation

. Perform a percutaneous Achilles tendon lengthening

Explanation

A narrow safe zone of Ramsey (< 20 degrees between reduction and redislocation) increases the risk of avascular necrosis if the hip is forced into hyperabduction. A percutaneous adductor longus tenotomy safely increases the maximal abduction, widening the safe zone for a safer spica cast position.

Question 2734

Topic: 4. Pediatrics

A 14-year-old boy is undergoing in situ single-screw fixation for a stable slipped capital femoral epiphysis (SCFE). To provide optimal stability and minimize the risk of unrecognized joint penetration, where should the screw threads be ideally positioned within the epiphysis?

. In the anterior-superior quadrant
. In the posterior-inferior quadrant
. In the center of the epiphysis on both AP and lateral views
. In the anterior-inferior quadrant
. Parallel to the physis without crossing it

Correct Answer & Explanation

. In the anterior-superior quadrant

Explanation

The ideal screw placement for a SCFE is the center-center position (center of the epiphysis on both the AP and lateral radiographs). This trajectory is perpendicular to the physis, provides maximal mechanical stability, and significantly reduces the risk of inadvertent joint penetration.

Question 2735

Topic: Pediatric Hip

A 13-year-old girl was treated 8 months ago with a single cannulated screw for a SCFE. She now presents with progressive hip stiffness, worsening pain, and a significant loss of hip range of motion. Radiographs demonstrate diffuse joint space narrowing of the affected hip without focal collapse. What is the most likely etiology of this late complication?

. Avascular necrosis
. Unrecognized intra-articular screw penetration leading to chondrolysis
. Septic arthritis
. Hardware failure resulting in loss of fixation
. Secondary osteoarthritis due to femoroacetabular impingement

Correct Answer & Explanation

. Avascular necrosis

Explanation

Chondrolysis is characterized by acute loss of articular cartilage and joint space narrowing, presenting with severe stiffness. In the setting of SCFE treatment, it is most strongly associated with unrecognized intra-articular hardware penetration.

Question 2736

Topic: Pediatric Hip

A 2-year-old girl is brought to the clinic for a newly noticed painless limp. Radiographs demonstrate a completely dislocated right hip with a false acetabulum and a dysplastic true acetabulum. Based on her age and presentation, what is the most appropriate initial management?

. Pavlik harness application
. Closed reduction and spica casting
. Open reduction, pelvic osteotomy, and potential femoral shortening
. Wait until skeletal maturity for a total hip arthroplasty
. Observation as the false acetabulum will remodel

Correct Answer & Explanation

. Pavlik harness application

Explanation

Children presenting with DDH after 18-24 months of age typically have significant secondary adaptive changes (acetabular dysplasia and capsular constriction). Successful treatment usually requires an open reduction combined with a pelvic osteotomy and often a femoral shortening osteotomy.

Question 2737

Topic: Pediatric Hip

A 12-year-old, overweight boy complains of vague left knee pain for the past 3 months. His knee examination is completely unremarkable. When the examiner passively flexes his left hip to 90 degrees, the leg obligately deviates into external rotation. What is the most likely underlying diagnosis?

. Legg-Calve-Perthes disease
. Developmental dysplasia of the hip
. Osgood-Schlatter disease
. Slipped capital femoral epiphysis
. Transient synovitis

Correct Answer & Explanation

. Legg-Calve-Perthes disease

Explanation

Obligate external rotation of the hip during passive flexion is a pathognomonic physical exam finding for a slipped capital femoral epiphysis (SCFE). Furthermore, SCFE frequently presents as referred knee or thigh pain, leading to potential misdiagnosis if the hip is not examined.

Question 2738

Topic: Pediatric Hip

A 10-year-old boy is diagnosed with a unilateral stable slipped capital femoral epiphysis. Which of the following radiographic parameters is considered the most reliable predictor for the development of a subsequent contralateral slip?

. Initial slip angle > 50 degrees
. Southwick slip angle on the lateral radiograph
. Modified Oxford bone age score
. Klein's line intersection on the anteroposterior radiograph
. Femoral neck-shaft angle

Correct Answer & Explanation

. Initial slip angle > 50 degrees

Explanation

The Modified Oxford bone age score relies on pelvic radiographs to determine skeletal maturity and is the most reliable predictor of a contralateral slip. Patients with a lower score (greater skeletal immaturity) are at the highest risk for sequential SCFE.

Question 2739

Topic: Pediatric Hip

A 6-week-old female is undergoing treatment with a Pavlik harness for developmental dysplasia of the hip. At a follow-up visit, the parents report the infant is no longer kicking her right leg. Examination reveals an inability to actively extend the knee on the affected side. This complication is most directly caused by which of the following?

. Excessive flexion of the anterior straps
. Inadequate flexion of the anterior straps
. Excessive abduction of the posterior straps
. Inadequate abduction of the posterior straps
. Excessive internal rotation of the lower leg

Correct Answer & Explanation

. Excessive flexion of the anterior straps

Explanation

Femoral nerve palsy in a Pavlik harness is caused by hyperflexion of the hips, typically resulting from overly tight anterior straps. Management consists of loosening the straps to reduce flexion and monitoring for spontaneous recovery.

Question 2740

Topic: Pediatric Hip

According to the Loder classification, an unstable slipped capital femoral epiphysis (SCFE) is associated with a significantly higher rate of which of the following complications when compared to a stable SCFE?

. Chondrolysis
. Avascular necrosis of the femoral head
. Premature physeal closure
. Femoroacetabular impingement
. Development of a contralateral slip

Correct Answer & Explanation

. Chondrolysis

Explanation

The Loder classification defines an unstable SCFE by the patient's inability to ambulate even with crutches. Unstable slips carry a nearly 50% risk of avascular necrosis, whereas the rate in stable slips is close to zero.

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