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4. Pediatrics MCQs

Practice Set 116 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 2301

Topic: Pediatric Hip

Prophylactic pinning of the contralateral hip is most strongly indicated and routinely recommended for which of the following patients presenting with a unilateral Slipped Capital Femoral Epiphysis (SCFE)?

. An 11-year-old girl with an idiopathic SCFE and closed triradiate cartilages
. A 12-year-old boy with a BMI in the 85th percentile
. A 10-year-old boy with renal osteodystrophy
. A 14-year-old boy with normal endocrine function
. A 15-year-old girl with an acute-on-chronic SCFE

Correct Answer & Explanation

. A 10-year-old boy with renal osteodystrophy

Explanation

Prophylactic pinning of the contralateral hip is indicated in patients at high risk for a sequential slip. Endocrine or metabolic disorders (such as renal osteodystrophy, hypothyroidism, or panhypopituitarism) carry a very high risk of bilateral involvement. Open triradiate cartilage (indicating young age) is another relative indication.

Question 2302

Topic: Pediatric Lower Extremity

According to the Ponseti method for the conservative treatment of congenital talipes equinovarus (clubfoot), what is the correct sequence of deformity correction during serial casting?

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

Correct Answer & Explanation

. Cavus, Varus, Adductus, Equinus

Explanation

The Ponseti method sequentially corrects the components of the clubfoot deformity in the specific order represented by the acronym CAVE: Cavus (corrected by elevating the first ray to supinate the forefoot), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy for full correction).

Question 2303

Topic: Pediatric Hip

A 12-year-old boy is diagnosed with a severe left slipped capital femoral epiphysis (SCFE) and undergoes in-situ pinning. Which of the following factors is the strongest absolute indication for performing a prophylactic pinning of the contralateral asymptomatic hip?

. Endocrine disorder (e.g., hypothyroidism)
. Male gender
. Modified Oxford Bone Age score of 18
. Body Mass Index in the 85th percentile
. Presentation with acute-on-chronic symptoms

Correct Answer & Explanation

. Endocrine disorder (e.g., hypothyroidism)

Explanation

Patients with an underlying endocrinopathy (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy) have an extremely high risk of bilateral SCFE (up to 100% in some series) and often present at an atypical age. Prophylactic pinning of the contralateral hip is strongly indicated in these patients. A low Modified Oxford Bone Age score (<16) also predicts higher risk, while a score of 18 implies skeletal maturity with minimal risk.

Question 2304

Topic: Pediatric Lower Extremity

A 2-year-old child presents with bilateral genu varum. Radiographs show medial beaking of the proximal tibial metaphysis. Which of the following radiographic measurements is the most reliable predictor that the deformity will progress (infantile Blount's disease) rather than resolve (physiologic bowing)?

. Tibiofemoral angle > 15 degrees
. Metaphyseal-diaphyseal angle (Drennan angle) > 16 degrees
. Epiphyseal-diaphyseal angle > 10 degrees
. Mechanical axis zone 3 or greater
. Posterior slope of the proximal tibia > 10 degrees

Correct Answer & Explanation

. Metaphyseal-diaphyseal angle (Drennan angle) > 16 degrees

Explanation

The metaphyseal-diaphyseal angle (Drennan angle) is critical in distinguishing physiologic bowing from infantile Blount's disease. An angle > 16 degrees has a high predictive value (up to 95%) that the varus deformity will progress (Blount's disease), warranting intervention such as bracing. Angles < 10 degrees typically indicate physiologic bowing, which resolves spontaneously.

Question 2305

Topic: Pediatric Upper Extremity & Spine
An infant is born with a unilateral radial clubhand (radial longitudinal deficiency). The consulting geneticist suspects a systemic syndrome. Physical examination reveals an absent thumb on the affected side. Which of the following syndromes is strictly characterized by the presence of a thumb despite radial deficiency, making it clinically distinguishable from the others?
. Holt-Oram syndrome
. Fanconi anemia
. VACTERL association
. Thrombocytopenia-absent radius (TAR) syndrome
. Roberts syndrome

Correct Answer & Explanation

. Thrombocytopenia-absent radius (TAR) syndrome

Explanation

Thrombocytopenia-absent radius (TAR) syndrome is unique among the conditions associated with radial longitudinal deficiency because the thumb is classically present, whereas in Holt-Oram syndrome, Fanconi anemia, and VACTERL association, the thumb is typically hypoplastic or absent.

Question 2306

Topic: Pediatric Hip

Which of the following factors is the most significant clinical predictor for the development of avascular necrosis (AVN) following a slipped capital femoral epiphysis (SCFE)?

. Body mass index (BMI) over the 95th percentile
. Severe slip angle (> 50 degrees)
. Instability of the slip (inability to bear weight)
. Age of the patient at the time of onset
. Underlying endocrine dysfunction

Correct Answer & Explanation

. Instability of the slip (inability to bear weight)

Explanation

The stability of the SCFE, defined by Loder as the ability or inability to bear weight (even with crutches), is the most important prognostic factor for AVN. Unstable SCFE has an AVN rate approaching 20-50%, whereas stable SCFE has an AVN rate of nearly 0%.

Question 2307

Topic: Pediatric Hip

A 4-month-old female infant is undergoing treatment with a Pavlik harness for developmental dysplasia of the hip (DDH). After 3-4 weeks of verified, continuous proper harness wear, ultrasound confirms the hip remains completely dislocated. What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 4 weeks
. Switch to an Ilfeld splint for rigid abduction
. Abandon the harness and proceed to closed reduction and spica casting
. Perform an immediate open reduction and pelvic osteotomy
. Discontinue the harness and wait until walking age to re-evaluate

Correct Answer & Explanation

. Abandon the harness and proceed to closed reduction and spica casting

Explanation

If a hip remains dislocated after 3 to 4 weeks of proper Pavlik harness treatment, the harness must be abandoned. Continuing it increases the risk of 'Pavlik harness disease' (posterior acetabular damage) and AVN. The next standard step is closed reduction and spica casting, possibly preceded by rigid orthosis trial or traction, but closed reduction is the definitive next step.

Question 2308

Topic: Pediatric Lower Extremity

According to the Ponseti method for the conservative management of idiopathic clubfoot, what is the correct sequence of deformity correction during serial casting?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method corrects the components of clubfoot in a specific sequence, remembered by the mnemonic CAVE: Cavus (corrected first by supinating the forefoot to align with the hindfoot), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy).

Question 2309

Topic: Pediatric Hip
A 4-week-old infant is referred for management of Developmental Dysplasia of the Hip (DDH). Which of the following conditions represents an absolute contraindication for the use of a Pavlik harness?
. Bilateral hip dislocation
. Age less than 6 weeks
. Teratologic hip dislocation (e.g., Arthrogryposis multiplex congenita)
. An alpha angle of 45 degrees on ultrasound
. A Barlow-positive, Ortolani-negative hip

Correct Answer & Explanation

. Teratologic hip dislocation (e.g., Arthrogryposis multiplex congenita)

Explanation

The use of a Pavlik harness relies on normal muscle function and active motion to achieve and maintain hip reduction. Teratologic hip dislocations (associated with syndromes such as arthrogryposis or spina bifida) exhibit severe muscle imbalance or contractures. In these cases, a Pavlik harness is absolutely contraindicated due to a high failure rate and an increased risk of complications. Other absolute contraindications include failure to achieve reduction after 3-4 weeks of use, or significant patient/family non-compliance.

Question 2310

Topic: Pediatric Hip

Prophylactic in situ pinning of the contralateral hip in patients presenting with a unilateral Slipped Capital Femoral Epiphysis (SCFE) is a debated topic. However, it is most strongly and universally indicated in which of the following clinical scenarios?

. A 14-year-old male with an idiopathic acute SCFE
. A 10-year-old male with a chronic SCFE and a BMI in the 85th percentile
. A 12-year-old female with SCFE and renal osteodystrophy
. A 13-year-old male with SCFE and a normal endocrine laboratory profile
. A 15-year-old female with an acute-on-chronic SCFE

Correct Answer & Explanation

. A 12-year-old female with SCFE and renal osteodystrophy

Explanation

Patients with underlying endocrine or metabolic disorders (such as renal osteodystrophy, hypothyroidism, or panhypopituitarism) are at a markedly elevated risk for developing bilateral SCFE (approaching 100% in some cohorts). Therefore, prophylactic fixation of the contralateral hip is universally recommended for these patients. Idiopathic cases have a lower bilateral rate (typically 20-40%), making prophylaxis a topic of shared decision-making rather than an absolute indication.

Question 2311

Topic: Pediatric Hip
In the evaluation of a child with Legg-Calvรฉ-Perthes disease, Catterall described specific 'head at risk' clinical and radiographic signs that portend a poor prognosis and higher risk of femoral head deformation. Which of the following is considered a 'head at risk' radiographic sign?
. Metaphyseal cysts
. Medial subluxation of the femoral head
. Ossification of the lateral pillar
. Decreased teardrop distance
. Sclerosis of the acetabulum

Correct Answer & Explanation

. Medial subluxation of the femoral head

Explanation

Catterall's 'head at risk' signs indicate a high likelihood of a poor clinical outcome. The five classic signs are: 1. Gage's sign (a V-shaped radiolucency in the lateral portion of the epiphysis and adjacent metaphysis), 2. Calcification lateral to the epiphysis, 3. Lateral (not medial) subluxation of the femoral head, 4. A horizontal orientation of the growth plate, and 5. Metaphyseal cysts. These signs typically mandate more aggressive treatment.

Question 2312

Topic: Pediatric Hip

A 12-year-old boy with a BMI in the 98th percentile undergoes in situ percutaneous pinning for a stable slipped capital femoral epiphysis (SCFE). During advancement of the single cannulated screw, the surgeon observes an 'approach-withdraw' phenomenon on the lateral fluoroscopic view. What severe complication is most strongly associated with failure to recognize and correct this intraoperative finding?

. Avascular necrosis of the femoral head
. Chondrolysis of the hip joint
. Iatrogenic femoral neck fracture
. Premature physeal closure with severe leg length discrepancy
. Subtrochanteric fracture

Correct Answer & Explanation

. Chondrolysis of the hip joint

Explanation

The 'approach-withdraw' phenomenon occurs when a screw penetrates the articular surface of the femoral head. As the screw is advanced and the hip is rotated, the screw tip appears to approach and then withdraw from the subchondral bone on fluoroscopy due to the spherical shape of the head. Unrecognized joint penetration is a primary cause of chondrolysis following SCFE fixation.

Question 2313

Topic: 4. Pediatrics

A 2-week-old infant is brought to the pediatric orthopedic clinic for treatment of bilateral idiopathic clubfeet using the Ponseti method. What is the correct, stepwise sequence of deformity correction during serial casting?

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

Correct Answer & Explanation

. Cavus, Adduction, Varus, Equinus

Explanation

The Ponseti method dictates a specific sequence of correction summarized by the acronym CAVE: Cavus (corrected by supinating the forefoot to align with the hindfoot), Adduction (corrected by abducting the foot around the fixed talar head), Varus (corrects passively with abduction as the calcaneus everts), and finally Equinus (corrected last, usually requiring a percutaneous Achilles tenotomy).

Question 2314

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy presents to the emergency department with a completely displaced, extension-type supracondylar humerus fracture (Gartland Type III). On physical examination, he is unable to flex the interphalangeal (IP) joint of his thumb and the distal interphalangeal (DIP) joint of his index finger. Which of the following neurological structures is most likely injured?
. Ulnar nerve
. Radial nerve
. Posterior interosseous nerve
. Anterior interosseous nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior interosseous nerve

Explanation

The anterior interosseous nerve (AIN), a branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. Injury manifests as an inability to flex the IP joint of the thumb (FPL) and the DIP joint of the index finger (FDP), preventing the patient from making an 'A-OK' sign.

Question 2315

Topic: 4. Pediatrics
A 3-year-old boy with multiple cafรฉ-au-lait spots presents with anterolateral bowing of the tibia. Radiographs demonstrate focal sclerosis and narrowing of the medullary canal of the tibia. What is the underlying pathophysiology of the localized tibial lesion in this condition?
. Genetic defect in type I collagen synthesis
. Osteoclast overactivity leading to rapid bone turnover
. Gain-of-function mutation in the FGFR3 gene
. Thickened periosteum containing hamartomatous fibrous tissue
. Severe vitamin D deficiency causing osteoid mineralization failure

Correct Answer & Explanation

. Thickened periosteum containing hamartomatous fibrous tissue

Explanation

The clinical picture describes Congenital Pseudoarthrosis of the Tibia (CPT), which is highly associated with Neurofibromatosis Type 1 (NF1). The underlying pathophysiology of the nonunion and bowing is a highly thickened, tight periosteum containing hamartomatous fibrous tissue that chokes the periosteal blood supply, leading to localized ischemia, sclerosis, and subsequent spontaneous fracture/pseudoarthrosis.

Question 2316

Topic: Pediatric Hip

An 8-month-old female presents with a persistently dislocated left hip after an unsuccessful 6-week trial of a Pavlik harness initiated at age 5 months. Ultrasound confirms continued posteroclavicular dislocation. What is the most appropriate next step in management?

. Re-application of the Pavlik harness for an additional 4 weeks
. Transition to a rigid hip abduction orthosis (e.g., Ilfeld splint)
. Closed reduction and spica casting under general anesthesia
. Open reduction with femoral shortening osteotomy
. Observation until skeletal maturity to perform a salvage osteotomy

Correct Answer & Explanation

. Closed reduction and spica casting under general anesthesia

Explanation

In children older than 6 months with Developmental Dysplasia of the Hip (DDH), or those who fail a Pavlik harness, closed reduction and spica casting under general anesthesia with an arthrogram is the next standard step. A rigid abduction brace is sometimes used for Pavlik failure in infants <6 months, but at 8 months, closed reduction is indicated. Open reduction is reserved for failure of closed reduction.

Question 2317

Topic: Pediatric Hip

A 12-year-old obese male presents to the emergency department unable to bear weight on his right leg for the past 24 hours after a minor fall. Radiographs confirm a severe, unstable slipped capital femoral epiphysis (SCFE). Which of the following complications is he at the highest risk for developing compared to a patient with a stable SCFE?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Femoroacetabular impingement (FAI)
. Slipped capital femoral epiphysis of the contralateral hip
. Premature physeal closure leading to leg length discrepancy

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

An unstable SCFE is defined by the inability of the patient to bear weight, even with crutches (Loder classification). Unstable SCFE has a notoriously high rate of avascular necrosis (AVN) of the femoral head, ranging from 20-50%, compared to stable SCFE, where AVN is extremely rare (<1%).

Question 2318

Topic: 4. Pediatrics

A 2-week-old infant is diagnosed with idiopathic congenital talipes equinovarus (clubfoot). The treating orthopedic surgeon initiates the Ponseti method of serial casting. In what sequential order are the components of the deformity corrected?

. Equinus, Varus, Adductus, Cavus
. Cavus, Adductus, Varus, Equinus
. Adductus, Cavus, Equinus, Varus
. Varus, Cavus, Adductus, Equinus
. All components are corrected simultaneously

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method systematically corrects the deformities of clubfoot in a specific sequence, remembered by the mnemonic CAVE: Cavus (corrected first by elevating the first ray to align the forefoot with the hindfoot), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy as the final step).

Question 2319

Topic: Pediatric Lower Extremity

A 2-week-old infant is brought to the clinic with an idiopathic clubfoot. The treating orthopedic surgeon plans to initiate the Ponseti method of serial casting. According to the principles of the Ponseti method, what is the first step in correcting the complex deformity of the foot?

. Abducting the forefoot to correct the adductus
. Pronating the forefoot to correct the varus
. Plantarflexing the first ray to correct the cavus
. Dorsiflexing the first ray to correct the cavus
. Dorsiflexing the ankle to correct the equinus

Correct Answer & Explanation

. Dorsiflexing the first ray to correct the cavus

Explanation

The Ponseti method addresses clubfoot deformities in a specific sequence summarized by the acronym CAVE: Cavus, Adductus, Varus, Equinus. The very first step is to correct the cavus deformity. This is achieved by supinating the forefoot and elevating (dorsiflexing) the first ray to align the forefoot with the hindfoot.

Question 2320

Topic: 4. Pediatrics

A 9-year-old boy (Tanner stage 1) sustains a midsubstance ACL tear while playing soccer. Non-operative management fails, and he experiences recurrent instability. Surgical intervention is planned. To minimize the risk of growth arrest and angular deformity, which of the following techniques is considered the most appropriate standard of care?

. Standard transphyseal reconstruction with interference screws
. Primary repair of the midsubstance tear using suture anchors
. Physeal-sparing all-epiphyseal reconstruction
. Bone-patellar tendon-bone (BTB) autograft reconstruction
. Wait until skeletal maturity while continuing conservative management

Correct Answer & Explanation

. Physeal-sparing all-epiphyseal reconstruction

Explanation

In a skeletally immature patient with wide-open physes (Tanner stage 1), drilling standard transphyseal tunnels risks significant growth arrest and angular deformity. The best accepted surgical technique to minimize physeal injury while restoring intra-articular stability is a physeal-sparing all-epiphyseal reconstruction (or an extra-articular Iliotibial band tenodesis such as the MacIntosh procedure, though all-epiphyseal is an intra-articular choice). BTB and standard transphyseal interference screws are contraindicated due to the high risk of physeal damage.

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