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4. Pediatrics MCQs

Practice Set 105 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 2081

Topic: Pediatric Hip

A 6-month-old infant is diagnosed with a delayed presentation of developmental dysplasia of the hip (DDH). Ultrasound confirms a completely dislocated but reducible hip. What is the most appropriate initial management step?

. Application of a Pavlik harness
. Closed reduction and spica cast application under general anesthesia
. Open reduction via an anterior approach
. Bilateral femoral derotation osteotomies
. Observation until 1 year of age

Correct Answer & Explanation

. Closed reduction and spica cast application under general anesthesia

Explanation

For a reducible DDH at 6 months of age, closed reduction under general anesthesia (often with an arthrogram) followed by spica casting is the standard of care. A Pavlik harness is generally ineffective and poorly tolerated after 6 months of age.

Question 2082

Topic: Pediatric Hip
Which of the following is the strongest indication for prophylactic pinning of the asymptomatic contralateral hip in a patient presenting with unilateral Slipped Capital Femoral Epiphysis (SCFE)?
. Male gender
. Age greater than 14 years at presentation
. Underlying hypothyroidism
. Body Mass Index (BMI) greater than the 95th percentile
. Grade III severe slip on the symptomatic side

Correct Answer & Explanation

. Underlying hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in SCFE is generally indicated in patients with underlying endocrinopathies (such as hypothyroidism, renal osteodystrophy, or growth hormone deficiency) or those undergoing radiation therapy, because their risk of developing bilateral SCFE approaches 50-100%. While obesity is a risk factor for SCFE, it alone is not an absolute indication for prophylactic pinning. Younger age (e.g., less than 10 years) or an open triradiate cartilage are also considered relative indications for prophylaxis due to the longer remaining growth and time at risk.

Question 2083

Topic: Pediatric Hip

According to the Herring Lateral Pillar Classification for Legg-Calve-Perthes disease, which of the following radiographic findings defines a Lateral Pillar Group C classification?

. No loss of height in the lateral pillar
. Less than 50% maintenance of lateral pillar height
. Greater than 50% maintenance of lateral pillar height but some lucency
. Less than 50% of the original lateral pillar height remains (greater than 50% collapse)
. Complete fragmentation of the medial pillar only

Correct Answer & Explanation

. Less than 50% of the original lateral pillar height remains (greater than 50% collapse)

Explanation

The Herring Lateral Pillar classification assesses the height of the lateral pillar of the femoral head on an AP pelvis radiograph during the fragmentation stage of Perthes disease. Group A: No loss of height. Group B: Greater than 50% of lateral pillar height is maintained. Group C: Less than 50% of lateral pillar height is maintained (i.e., greater than 50% collapse). The B/C border group maintains exactly 50% height or has a narrow, depressed lateral pillar. Group C has the poorest prognosis.

Question 2084

Topic: Pediatric Hip

A 4-month-old infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). At the follow-up appointment, the parents report that the baby has stopped actively extending the knee on the treated side. Physical exam confirms absent active knee extension and a diminished patellar reflex. What was the most likely error in the application of the harness?

. Excessive hip flexion
. Excessive hip abduction
. Inadequate hip flexion
. Excessive hip extension
. Inadequate hip abduction

Correct Answer & Explanation

. Excessive hip flexion

Explanation

The infant has developed a femoral nerve palsy, a known complication of Pavlik harness treatment. This is typically caused by hyperflexion of the hips, which compresses the femoral nerve against the inguinal ligament or pubis. The treatment is to temporarily remove the harness or adjust the anterior straps to reduce flexion. Excessive abduction is associated with a different, severe complication: avascular necrosis (AVN) of the femoral head.

Question 2085

Topic: 4. Pediatrics
A 13-year-old girl sustains an ankle injury while playing soccer. Radiographs reveal a Salter-Harris III fracture of the anterolateral distal tibia. Which of the following best describes the pathoanatomy and mechanism of this specific injury?
. Plantar flexion injury causing avulsion via the anterior talofibular ligament
. External rotation injury causing avulsion via the anterior inferior tibiofibular ligament
. Supination-inversion injury causing avulsion via the calcaneofibular ligament
. Axial loading causing impaction of the lateral tibial plafond
. Pronation-abduction injury causing a compression fracture of the lateral physis

Correct Answer & Explanation

. External rotation injury causing avulsion via the anterior inferior tibiofibular ligament

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibia. It occurs in adolescents (usually 12-14 years old) because the distal tibial physis closes from central to anteromedial to posteromedial, and finally the anterolateral portion closes last. An external rotation force causes the anterior inferior tibiofibular ligament (AITFL) to avulse this unfused anterolateral fragment.

Question 2086

Topic: Pediatric Hip

A 6-week-old female is diagnosed with Developmental Dysplasia of the Hip (DDH) and placed in a Pavlik harness. During a follow-up visit, the orthopaedic surgeon notes decreased spontaneous movement of the patient's knee and an absent patellar reflex on the affected side. This complication is most likely due to which of the following mechanical positioning errors in the harness?

. Excessive abduction of the hips
. Inadequate abduction of the hips
. Excessive flexion of the hips
. Inadequate flexion of the hips
. Excessive internal rotation of the hips

Correct Answer & Explanation

. Excessive flexion of the hips

Explanation

The complication described is a femoral nerve palsy, which manifests as decreased active knee extension and an absent patellar reflex. In a Pavlik harness, this is classically caused by hyperflexion of the hips (typically > 120 degrees), which compresses the femoral nerve against the inguinal ligament. Excessive abduction is associated with avascular necrosis (AVN) of the femoral head.

Question 2087

Topic: 4. Pediatrics
A 13-year-old boy sustains an ankle injury while playing soccer. Radiographs reveal a Salter-Harris III fracture of the anterolateral aspect of the distal tibial epiphysis. Which of the following describes the most likely deforming force and the ligamentous structure attached to this avulsed fragment?
. Inversion, calcaneofibular ligament
. External rotation, anterior inferior tibiofibular ligament
. Plantar flexion, anterior talofibular ligament
. Internal rotation, posterior inferior tibiofibular ligament
. Eversion, deltoid ligament

Correct Answer & Explanation

. External rotation, anterior inferior tibiofibular ligament

Explanation

This is a classic juvenile Tillaux fracture, which is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. It occurs due to an external rotation force. The anterior inferior tibiofibular ligament (AITFL) is intact and avulses the anterolateral epiphysis because, in this age group, the physis closes from central to anteromedial to posteromedial, leaving the anterolateral portion open and vulnerable last.

Question 2088

Topic: Pediatric Hip

A 12-year-old boy presents with an acute-on-chronic slipped capital femoral epiphysis (SCFE) of the left hip. Prophylactic pinning of the contralateral right hip is discussed with the family. Which of the following patient factors is considered the strongest absolute indication for prophylactic fixation of the asymptomatic contralateral hip?

. Patient age over 14 years
. Male sex
. Anteroposterior alpha angle > 55 degrees
. Presence of an underlying endocrine disorder
. Body Mass Index (BMI) greater than the 95th percentile

Correct Answer & Explanation

. Presence of an underlying endocrine disorder

Explanation

Patients with underlying endocrine disorders (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) have an exceptionally high rate (up to 100% in some series) of developing bilateral SCFE. Prophylactic pinning of the contralateral hip is strongly indicated in these cases. The other options are relative considerations but not as definitive as a diagnosed endocrinopathy.

Question 2089

Topic: Pediatric Lower Extremity

In the Ponseti method for the conservative treatment of idiopathic clubfoot, sequential correction of the specific deformity components is essential to avoid creating a rocker-bottom foot. Which of the following represents the correct order of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method dictates a specific sequence of correction remembered by the acronym CAVE: Cavus (corrected by elevating the first ray), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy). Correcting equinus before the midfoot is corrected can result in a rocker-bottom deformity.

Question 2090

Topic: Pediatric Hip

A 10-year-old boy with a BMI in the 99th percentile and height in the 3rd percentile presents with bilateral knee pain and a waddling gait. Radiographs confirm bilateral Slipped Capital Femoral Epiphysis (SCFE). Given his age and height percentile, an endocrine workup is initiated. Which of the following is the most commonly associated endocrinopathy in this clinical scenario?

. Hyperthyroidism
. Hypothyroidism
. Hyperparathyroidism
. Growth hormone excess
. Congenital adrenal hyperplasia

Correct Answer & Explanation

. Hypothyroidism

Explanation

Hypothyroidism is the most common endocrine disorder associated with Slipped Capital Femoral Epiphysis (SCFE). Patients with endocrine-related SCFE typically present at an atypical age (either younger than 10 or older than 16), often with short stature, and frequently have bilateral involvement. The combination of obesity and decreased height velocity strongly suggests hypothyroidism, distinguishing it from typical idiopathic SCFE where patients may be obese but are usually of normal or increased height.

Question 2091

Topic: Pediatric Hip

A 3-month-old female infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). During her 2-week follow-up, the mother reports that the infant is not kicking her left leg as much as the right. On examination, the infant exhibits absent active knee extension on the left side, although she withdraws to pain. Passive range of motion is full. Which of the following adjustments to the Pavlik harness is the most appropriate next step in management?

. Loosen the anterior flexion straps
. Tighten the anterior flexion straps
. Loosen the posterior abduction straps
. Tighten the posterior abduction straps
. Abandon the Pavlik harness and proceed to closed reduction and spica casting

Correct Answer & Explanation

. Loosen the anterior flexion straps

Explanation

The infant is presenting with a femoral nerve palsy, a known complication of the Pavlik harness. This occurs due to excessive hyperflexion of the hip, which compresses or stretches the femoral nerve against the inguinal ligament or pelvic brim. The clinical sign is a loss of active knee extension. The appropriate management is to temporarily loosen or release the anterior flexion straps to reduce the degree of hip flexion, allowing the nerve to recover. Abandoning the harness entirely is not immediately indicated unless the palsy fails to resolve.

Question 2092

Topic: 4. Pediatrics

A 6-year-old child presents with a completely displaced, extension-type supracondylar humerus fracture. Prior to intervention, the hand is pale and pulseless. The child is taken to the operating room, where an anatomic closed reduction is achieved and pinned with three divergent lateral Kirschner wires. Post-reduction, the radial pulse remains impalpable by Doppler, but the hand is now warm, pink, and has a capillary refill of less than 2 seconds. What is the most appropriate next step in management?

. Immediate open exploration of the brachial artery via an anterior approach
. Perform a CT angiogram of the upper extremity
. Remove the pins and attempt an open reduction to relieve vascular kinking
. Admit for continuous neurovascular monitoring and observation
. Perform a prophylactic forearm fasciotomy

Correct Answer & Explanation

. Admit for continuous neurovascular monitoring and observation

Explanation

The management of the 'pink, pulseless hand' following a successfully reduced and pinned supracondylar humerus fracture is observation. If the hand is well-perfused (warm, pink, brisk capillary refill < 2 seconds) despite the absence of a palpable pulse, it indicates adequate collateral circulation. Current pediatric orthopedic guidelines recommend admission and close monitoring. Surgical exploration of the brachial artery is indicated if the hand remains pale and poorly perfused (ischemic) after reduction.

Question 2093

Topic: Pediatric Hip

A 3-year-old girl is undergoing surgical treatment for developmental dysplasia of the hip (DDH). The surgeon performs a pelvic osteotomy that is described as an incomplete, pericapsular osteotomy that hinges on the triradiate cartilage, allowing the acetabular roof to be hinged downward to improve anterolateral coverage, thereby decreasing the volume of the acetabulum. Which osteotomy is being described?

. Salter osteotomy
. Pemberton osteotomy
. Dega osteotomy
. Chiari osteotomy
. Tonnis osteotomy

Correct Answer & Explanation

. Pemberton osteotomy

Explanation

The Pemberton osteotomy is an incomplete transiliac osteotomy that hinges at the triradiate cartilage, altering the shape and decreasing the volume of the acetabulum. The Salter osteotomy is a complete osteotomy that hinges at the pubic symphysis without changing the acetabular volume. The Dega osteotomy also hinges at the triradiate cartilage but leaves the inner table of the ilium intact.

Question 2094

Topic: Pediatric Hip

A 13-year-old boy presents with a limp and obligate external rotation of his left hip during passive flexion, indicative of a slipped capital femoral epiphysis (SCFE). Relative to the capital femoral epiphysis, in what direction does the femoral neck (metaphysis) displace in a typical SCFE?

. Anterior and superior
. Anterior and inferior
. Posterior and superior
. Posterior and inferior
. Medial and inferior

Correct Answer & Explanation

. Posterior and inferior

Explanation

In a SCFE, the capital femoral epiphysis remains secured within the acetabulum while the femoral metaphysis (neck) displaces anteriorly and superiorly. This gives the radiographic appearance that the epiphysis has slipped posteriorly and inferiorly.

Question 2095

Topic: 4. Pediatrics

An infant is being treated for congenital idiopathic clubfoot using the Ponseti casting technique. The sequence of correction of the individual deformities is critical to achieving a successful outcome. According to the Ponseti method, which specific component of the deformity must be corrected FIRST?

. Equinus
. Varus
. Adduction
. Cavus
. Internal tibial torsion

Correct Answer & Explanation

. Equinus

Explanation

In the Ponseti method, the mnemonic CAVE dictates the order of correction: Cavus, Adductus, Varus, Equinus. The cavus is corrected first by elevating (supinating) the first metatarsal to align the forefoot with the hindfoot. Only then is the foot abducted to correct the adductus and varus, followed finally by addressing the equinus (often requiring a percutaneous Achilles tenotomy).

Question 2096

Topic: 4. Pediatrics

A 12-year-old obese male presents with knee and thigh pain. Radiographs demonstrate a classic 'ice cream slipping off a cone' appearance of the proximal femur, diagnostic of Slipped Capital Femoral Epiphysis (SCFE). The pathophysiology of this condition involves a mechanical failure primarily through which histological zone of the physis?

. Reserve zone
. Proliferative zone
. Hypertrophic zone
. Zone of provisional calcification
. Primary spongiosa

Correct Answer & Explanation

. Hypertrophic zone

Explanation

Slipped Capital Femoral Epiphysis (SCFE) occurs due to mechanical shear forces across a susceptible physis. The slippage invariably occurs through the hypertrophic zone of the physis, which is structurally the weakest layer because it lacks collagen matrix and is composed of large, swollen chondrocytes.

Question 2097

Topic: Pediatric Hip
A 6-year-old boy is diagnosed with Legg-Calvé-Perthes disease. During the radiographic evaluation of the hip, the earliest sign of the fragmentation stage represents a subchondral fracture of the femoral head. What is the eponym or term for this specific radiographic finding?
. Crescent sign
. Trethowan's sign
. Loss of Klein's line intersection
. Sagging rope sign
. Waldenström's sign

Correct Answer & Explanation

. Crescent sign

Explanation

The 'crescent sign' in Legg-Calvé-Perthes disease (or avascular necrosis) represents a subchondral fracture and marks the beginning of the fragmentation stage. Waldenström's sign is an increase in the medial joint space seen very early. Trethowan's sign and Klein's line are associated with SCFE. The sagging rope sign is a late sign indicating a widened femoral neck and coxa magna.

Question 2098

Topic: 4. Pediatrics

An 11-year-old obese boy presents with right thigh pain and a limp for 3 weeks. Radiographs confirm a stable slipped capital femoral epiphysis (SCFE). During in situ single screw fixation, where should the screw be positioned within the epiphysis to minimize the risk of joint penetration and maximize stability?

. Anterior and superior
. Anterior and inferior
. Posterior and superior
. Central and perpendicular to the physis
. Perpendicular to the femoral neck axis

Correct Answer & Explanation

. Central and perpendicular to the physis

Explanation

The ideal screw placement for SCFE is in the center of the epiphysis and perpendicular to the physis. Because the epiphysis slips posteriorly and medially, the entry point on the anterior femoral neck needs to be adjusted to achieve this central and perpendicular trajectory.

Question 2099

Topic: Pediatric Lower Extremity

In the Ponseti method for correcting idiopathic clubfoot, what is the proper sequence of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method dictates sequential correction utilizing the acronym CAVE: Cavus (corrected first by supinating the forefoot), Adductus, Varus, and finally Equinus. Equinus is corrected last and often requires a percutaneous Achilles tenotomy.

Question 2100

Topic: Pediatric Hip

A 7-year-old girl with a history of neglected Developmental Dysplasia of the Hip (DDH) presents with a severely subluxated, incongruent hip joint. The acetabulum is extremely shallow and unable to adequately cover the femoral head using redirectional techniques. The surgeon decides to perform a salvage pelvic osteotomy that relies on the interposition of the joint capsule to provide coverage and medialize the hip center of rotation. Which of the following procedures is planned?

. Salter osteotomy
. Pemberton osteotomy
. Dega osteotomy
. Chiari osteotomy
. Ganz (Periacetabular) osteotomy

Correct Answer & Explanation

. Chiari osteotomy

Explanation

The Chiari osteotomy is a salvage procedure used for incongruent hips where the femoral head cannot be concentrically reduced. It involves an iliac osteotomy just above the acetabulum, with the distal fragment displaced medially. The interposed joint capsule undergoes metaplasia to form a fibrous weight-bearing surface (fibrocartilage). Salter, Pemberton, Dega, and Ganz are all reconstructive (redirectional or reshaping) osteotomies requiring a congruent hip joint.

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