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4. Pediatrics MCQs

Practice Set 98 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 1941

Topic: Pediatric Lower Extremity

An infant with severe idiopathic clubfoot (talipes equinovarus) is managed with serial casting according to the Ponseti method.

According to this treatment protocol, which component of the deformity is corrected last?

. Cavus
. Adductus
. Varus
. Equinus
. Supination

Correct Answer & Explanation

. Equinus

Explanation

The Ponseti method follows a strict sequence of deformity correction summarized by the acronym CAVE: Cavus (elevating the first ray to match the forefoot supination), Adductus, Varus, and finally Equinus. The equinus contracture is addressed last, and in about 80% of cases, correction requires a percutaneous Achilles tenotomy prior to the final cast application.

Question 1942

Topic: Pediatric Hip

A 13-year-old obese boy undergoes in situ pinning for a stable slipped capital femoral epiphysis (SCFE). During the procedure, the screw is inadvertently placed in the anterosuperior quadrant of the femoral head. What is the most likely complication associated with this specific pin position?

. Chondrolysis
. Osteonecrosis
. Slip progression
. Femoral neck fracture
. Labral tear

Correct Answer & Explanation

. Osteonecrosis

Explanation

The blood supply to the femoral head relies heavily on the lateral epiphyseal branches of the medial femoral circumflex artery, which enter the femoral head posterosuperiorly. Pin placement in the anterosuperior quadrant of the femoral head directly endangers this blood supply, significantly increasing the risk of iatrogenic osteonecrosis (avascular necrosis). The ideal screw position is in the center of the epiphysis.

Question 1943

Topic: Pediatric Hip

A 6-month-old female is diagnosed with Developmental Dysplasia of the Hip (DDH). An anterior-posterior radiograph of the pelvis is evaluated. Which of the following radiographic parameters specifically indicates superior (proximal) displacement of the femoral head?

. A broken Shenton's line
. The femoral head ossific nucleus lies medial to Perkin's line
. The femoral head ossific nucleus lies inferior to Hilgenreiner's line
. An acetabular index of 20 degrees
. A center-edge angle of Wiberg of 35 degrees

Correct Answer & Explanation

. A broken Shenton's line

Explanation

Shenton's line is a continuous curve formed by the medial border of the femoral neck and the superior border of the obturator foramen. A break in this line indicates proximal (superior) displacement of the femur relative to the pelvis. Normal position requires the ossific nucleus to be medial to Perkin's line (evaluates lateral displacement) and inferior to Hilgenreiner's line.

Question 1944

Topic: Pediatric Lower Extremity

In the Ponseti method for the treatment of idiopathic clubfoot, which of the following represents the correct sequence of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The correct sequence of correction in the Ponseti method follows the acronym CAVE: Cavus (corrected by elevating the first ray), Adductus, Varus, and finally Equinus (which often requires a percutaneous tendoachilles lengthening).

Question 1945

Topic: 4. Pediatrics

A 4-week-old infant with developmental dysplasia of the hip is treated with a Pavlik harness. During a follow-up visit, the parents report the infant is not kicking the treated leg. Examination shows decreased active knee extension but normal passive motion and hip flexion. What is the most likely cause of this clinical presentation?

. Avascular necrosis of the femoral head
. Femoral nerve palsy
. Obturator nerve palsy
. Sciatic nerve palsy
. Tibial nerve palsy

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment due to excessive hyperflexion of the hip, leading to nerve compression. It presents as decreased active knee extension (quadriceps weakness). Management requires temporary discontinuation or adjustment of the harness.

Question 1946

Topic: 4. Pediatrics

A 3-year-old female presents with progressive genu varum. Radiographs reveal beaking and fragmentation of the medial proximal tibial metaphysis consistent with infantile Blount's disease. Pathoanatomically, this disease is primarily caused by disordered endochondral ossification of which specific portion of the proximal tibial physis?

. Posteromedial aspect
. Anteromedial aspect
. Posterolateral aspect
. Anterolateral aspect
. Central physeal aspect

Correct Answer & Explanation

. Posteromedial aspect

Explanation

Blount's disease (tibia vara) is characterized by disordered endochondral ossification and growth suppression primarily at the posteromedial aspect of the proximal tibial physis. This asymmetric growth restriction leads to the classic clinical deformity of multiplanar varus, internal tibial torsion, and procurvatum.

Question 1947

Topic: Pediatric Hip

A 12-year-old boy presents with left thigh pain and an antalgic gait. Radiographs confirm a mild left slipped capital femoral epiphysis (SCFE). He is subsequently evaluated for potential contralateral disease. Which of the following is considered the strongest absolute indication for prophylactic in-situ pinning of the contralateral right hip?

. Open triradiate cartilage
. Underlying endocrine disorder
. Body mass index > 95th percentile
. Initial slip angle > 50 degrees
. Male gender

Correct Answer & Explanation

. Underlying endocrine disorder

Explanation

Prophylactic pinning of the contralateral hip in patients with SCFE is highly recommended and considered essentially an absolute indication for patients with endocrine or metabolic disorders (e.g., hypothyroidism, renal osteodystrophy, panhypopituitarism) due to the exceedingly high risk of bilateral involvement, approaching 100% in these conditions. Young age (<10 years) and open triradiate cartilage are relative indications.

Question 1948

Topic: 4. Pediatrics
A 14-year-old boy presents with acute ankle pain after an external rotation injury while playing soccer. Radiographs reveal a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. What is the primary deforming force (ligamentous attachment) responsible for producing this specific fracture pattern?
. Anterior talofibular ligament (ATFL)
. Calcaneofibular ligament (CFL)
. Anterior inferior tibiofibular ligament (AITFL)
. Posterior inferior tibiofibular ligament (PITFL)
. Deltoid ligament

Correct Answer & Explanation

. Anterior inferior tibiofibular ligament (AITFL)

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibial epiphysis. It occurs due to avulsion by the strong anterior inferior tibiofibular ligament (AITFL) during an external rotation injury. This pattern occurs in adolescents because the distal tibial physis closes asynchronously: central, then medial, and finally anterolateral, leaving the anterolateral portion vulnerable to avulsion.

Question 1949

Topic: Pediatric Hip
A 6-year-old boy is diagnosed with Legg-Calvé-Perthes disease. The treating orthopedist relies on the Herring Lateral Pillar classification to determine the child's prognosis and guide treatment. Which of the following accurately describes a Herring Lateral Pillar Group B hip?
. No involvement of the lateral pillar, maintaining 100% height
. > 50% maintenance of normal lateral pillar height
. < 50% maintenance of normal lateral pillar height
. Complete 100% collapse of the lateral pillar
. Central pillar collapse with perfectly intact lateral and medial pillars

Correct Answer & Explanation

. < 50% maintenance of normal lateral pillar height

Explanation

The Herring Lateral Pillar Classification evaluates the height of the lateral aspect of the capital femoral epiphysis. Group A: No involvement of the lateral pillar. Group B: >50% of the lateral pillar height is maintained. Group C: <50% of the lateral pillar height is maintained. A Group B/C classification was later added for borderline cases where the pillar is approximately 50% of normal height or poorly ossified. Prognosis significantly worsens from A to C.

Question 1950

Topic: Pediatric Hip



A 12-year-old boy presents with left thigh pain and an antalgic gait for 4 weeks. Radiographs confirm a stable left slipped capital femoral epiphysis (SCFE). Prophylactic in situ pinning of the contralateral asymptomatic right hip is most strongly indicated if the patient has which of the following concomitant conditions?

. A chronologic age of 14 years at presentation
. A body mass index (BMI) tracking in the 50th percentile
. A diagnosis of hypothyroidism or panhypopituitarism
. A slip angle of 20 degrees on the symptomatic left side
. A modified Oxford bone age score of 22

Correct Answer & Explanation

. A diagnosis of hypothyroidism or panhypopituitarism

Explanation

Patients with endocrine disorders (such as hypothyroidism, growth hormone deficiency) or renal osteodystrophy are at a significantly elevated risk for bilateral slipped capital femoral epiphysis (SCFE). In these populations, prophylactic pinning of the contralateral hip is highly recommended, regardless of their chronological age.

Question 1951

Topic: Pediatric Lower Extremity

An 8-week-old infant with rigid, idiopathic clubfoot is undergoing serial casting using the Ponseti method. To achieve a plantigrade, functional foot, the deformity must be systematically corrected in a specific sequence. Which of the following accurately represents the correct sequence of correction?

. Equinus, varus, adductus, cavus
. Cavus, adductus, varus, equinus
. Adductus, varus, cavus, equinus
. Varus, cavus, adductus, equinus
. Cavus, varus, adductus, equinus

Correct Answer & Explanation

. Cavus, varus, adductus, equinus

Explanation

The Ponseti method dictates that clubfoot deformities should be corrected in the specific order summarized by the mnemonic CAVE: Cavus (corrected first by elevating the first ray to supinate the forefoot), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy as the final step).

Question 1952

Topic: 4. Pediatrics

A 6-week-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip. At the 2-week follow-up, the mother notes the child is no longer actively extending the knee on the treated side. What is the most likely cause, and what is the appropriate management?

. Obturator nerve palsy; continue harness
. Femoral nerve palsy; temporarily discontinue the harness
. Sciatic nerve palsy; adjust the posterior strap
. Femoral nerve palsy; adjust the anterior strap to increase flexion
. Dislocated hip; proceed to closed reduction

Correct Answer & Explanation

. Femoral nerve palsy; temporarily discontinue the harness

Explanation

Hyperflexion in a Pavlik harness can lead to femoral nerve palsy, presenting as decreased active knee extension. The standard initial management for a clinically evident femoral nerve palsy in this setting is to temporarily remove the harness to allow for neurologic recovery, rather than continuing or tightening the straps.

Question 1953

Topic: 4. Pediatrics
In Legg-Calvé-Perthes disease, which of the following is considered a 'head-at-risk' radiographic sign of Catterall?
. Medial subluxation of the femoral head
. Vertical physis
. Gage's sign
. Acetabular dysplasia
. Premature closure of the triradiate cartilage

Correct Answer & Explanation

. Gage's sign

Explanation

Catterall's 'head-at-risk' signs include: Gage's sign (a V-shaped radiolucency in the lateral portion of the epiphysis/metaphysis), calcification lateral to the epiphysis, lateral subluxation of the femoral head, a horizontal physis, and metaphyseal cysts.

Question 1954

Topic: Pediatric Hip

A 12-year-old boy presents with left thigh pain, an antalgic gait, and an externally rotated left lower extremity. Radiographs demonstrate the pathology shown.

Which of the following is considered an absolute indication for prophylactic pinning of the asymptomatic, contralateral hip in a patient presenting with Slipped Capital Femoral Epiphysis (SCFE)?

. Obesity (BMI > 95th percentile)
. Male gender
. Underlying endocrine disorder (e.g., hypothyroidism)
. Age greater than 14 years at presentation
. Black race

Correct Answer & Explanation

. Underlying endocrine disorder (e.g., hypothyroidism)

Explanation

SCFE is characterized by a displacement of the proximal femoral epiphysis. Prophylactic pinning of the contralateral hip is somewhat controversial but generally recommended in patients with a high risk of subsequent contralateral slip. Absolute indications or highly strong recommendations for prophylactic contralateral pinning include an underlying endocrine disorder (such as hypothyroidism or growth hormone deficiency), renal osteodystrophy, previous radiation therapy, and presentation at a very young age (e.g., < 10 years). Endocrine disorders dramatically increase the risk of bilateral involvement, often occurring simultaneously or sequentially.

Question 1955

Topic: Pediatric Hip

A 6-week-old female infant is treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). At the second weekly follow-up, the parents report the infant is no longer moving her right lower extremity. Clinical examination reveals an absence of active knee extension on the right. What is the most likely iatrogenic cause of this finding?

. Avascular necrosis of the femoral head
. Femoral nerve palsy due to excessive hyperflexion
. Obturator nerve palsy due to excessive abduction
. Sciatic nerve palsy due to hyperflexion
. Common peroneal nerve palsy from the posterior foot strap

Correct Answer & Explanation

. Femoral nerve palsy due to excessive hyperflexion

Explanation

Femoral nerve palsy is the most common nerve palsy associated with Pavlik harness treatment and is typically caused by excessive flexion of the hips. Hyperflexion compresses the femoral nerve against the inguinal ligament, leading to decreased quadriceps function (loss of active knee extension). The treatment is to temporarily adjust or remove the harness; the palsy typically resolves spontaneously within days to weeks.

Question 1956

Topic: 4. Pediatrics

A 5-year-old boy falls from monkey bars and sustains a widely displaced supracondylar humerus fracture. Upon presentation to the emergency department, the hand is pink but the radial pulse is absent. He undergoes prompt closed reduction and percutaneous pinning. Post-operatively in the recovery room, the radial pulse remains absent, but the hand is warm with brisk capillary refill (less than 2 seconds) and normal oxygen saturation on the index finger. Which of the following is the most appropriate next step in management?

. Immediate return to the operating room for open exploration of the brachial artery
. Removal of the pins and placement of a hyperflexion cast
. Observation with close neurovascular monitoring
. CT angiography of the upper extremity
. Prophylactic forearm fasciotomies

Correct Answer & Explanation

. Observation with close neurovascular monitoring

Explanation

The patient has a 'pink, pulseless' hand following reduction and pinning of a supracondylar humerus fracture. Current pediatric orthopedic guidelines recommend observation for a well-perfused (pink, warm, brisk capillary refill) but pulseless hand post-reduction. The collateral circulation around the elbow is robust enough to maintain distal viability. Vascular exploration is indicated if the hand is white, cold, and poorly perfused (pulseless and ischemic) after a well-aligned reduction. Arteriography is generally not indicated and delays treatment if the limb is ischemic. Removing pins would destabilize the fracture and risk further neurovascular injury.

Question 1957

Topic: Pediatric Hip

A 13-year-old boy with a BMI in the 95th percentile presents with a 2-month history of vague left knee and thigh pain. On physical examination, he has an obligate external rotation of the left hip with passive hip flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Which of the following best describes the anatomic displacement of the femoral metaphysis relative to the epiphysis in this condition?

. Metaphysis displaces posterior and inferior
. Metaphysis displaces anterior and superior
. Metaphysis displaces posterior and superior
. Metaphysis displaces anterior and inferior
. Metaphysis displaces directly medial

Correct Answer & Explanation

. Metaphysis displaces anterior and superior

Explanation

In Slipped Capital Femoral Epiphysis (SCFE), the proximal femoral epiphysis remains relatively secure in the acetabulum while the femoral neck (metaphysis) displaces. Because the mechanical axis of weight-bearing forces acts anteriorly and superiorly on the proximal femur, the metaphysis translates anteriorly and superiorly. Clinically and radiographically, this makes the epiphysis appear to have slipped posteriorly and inferiorly relative to the neck. Therefore, the metaphysis moves anteriorly and superiorly.

Question 1958

Topic: Pediatric Upper Extremity & Spine

You are evaluating a 14-year-old female with Adolescent Idiopathic Scoliosis (AIS) to determine surgical fusion levels. According to the Lenke classification system, a proximal thoracic curve is defined as 'structural' (and thus typically requires inclusion in the fusion construct) if the Cobb angle on side-bending radiographs is at least:

. 10 degrees
. 15 degrees
. 20 degrees
. 25 degrees
. 30 degrees

Correct Answer & Explanation

. 25 degrees

Explanation

In the Lenke classification for adolescent idiopathic scoliosis, a minor curve is considered 'structural' if it does not bend out to less than 25 degrees on coronal side-bending radiographs, or if there is kyphosis of at least +20 degrees across the regional segments. Identifying structural minor curves is critical, as the general rule is to include all structural curves in the fusion construct.

Question 1959

Topic: Pediatric Hip

A 6-month-old female with Developmental Dysplasia of the Hip (DDH) fails initial Pavlik harness treatment. She undergoes closed reduction and application of a hip spica cast under general anesthesia. To minimize the risk of iatrogenic avascular necrosis (AVN) of the femoral head, the hip should be immobilized in the 'human position'. What specific joint angles correspond to this position?

. Greater than 110 degrees of flexion and maximal abduction
. 90 to 100 degrees of flexion and less than 60 degrees of abduction
. Neutral flexion/extension and 45 degrees of abduction
. 45 degrees of flexion and maximal external rotation
. 120 degrees of flexion and 90 degrees of abduction

Correct Answer & Explanation

. 90 to 100 degrees of flexion and less than 60 degrees of abduction

Explanation

The 'human position' for spica casting in DDH entails positioning the hip in approximately 90 to 100 degrees of flexion and moderate abduction (usually 45 to 60 degrees). Immobilizing the hip in extreme, forced abduction (the 'frog-leg' position, >60 degrees abduction) dramatically increases the risk of avascular necrosis (AVN) of the femoral head by compressing the extraosseous epiphyseal vessels against the acetabular margin.

Question 1960

Topic: Pediatric Hip

A 12-year-old obese male presents with left knee pain and an obligate external rotation of the left hip upon flexion. Radiographs confirm a severe, unstable left slipped capital femoral epiphysis (SCFE). Which of the following is an established indication for prophylactic in situ pinning of the contralateral, asymptomatic hip?

. Patient age > 14 years at presentation
. Presence of an endocrine disorder such as hypothyroidism
. Unstable SCFE on the ipsilateral side regardless of age
. Presentation with a slipped angle > 60 degrees
. Body Mass Index > 30

Correct Answer & Explanation

. Presence of an endocrine disorder such as hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is strongly indicated in certain high-risk populations. These include patients with underlying endocrinopathies (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy), metabolic disorders, or those who present at an atypically young age (females < 10 years, males < 12 years). Severe slips or unstable slips alone, or obesity, do not mandate prophylactic pinning without careful consideration of the risks.

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