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4. Pediatrics MCQs

Practice Set 95 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 1881

Topic: Pediatric Hip

A 10-year-old boy presents with a unilateral stable Slipped Capital Femoral Epiphysis (SCFE). In addition to treating the affected hip, the surgeon considers prophylactic in situ pinning of the contralateral hip. Which of the following conditions is the strongest indication for prophylactic fixation?

. Male sex
. Age greater than 14 years
. Hypothyroidism
. Body Mass Index (BMI) in the 85th percentile
. Presentation with a stable SCFE slip angle of 20 degrees

Correct Answer & Explanation

. Hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in SCFE is highly recommended in patients with endocrine disorders (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) due to the significantly higher risk of bilateral involvement. Other indications for prophylactic pinning include young age (< 10 years for boys) and unreliability for follow-up.

Question 1882

Topic: 4. Pediatrics

The Ponseti method is the gold standard for the non-operative correction of congenital idiopathic clubfoot (talipes equinovarus). According to the principles of this method, in what order should the components of the deformity be corrected?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method sequentially corrects the deformities using the mnemonic CAVE: Cavus (corrected by elevating the first ray to supinate the forefoot and align it with the hindfoot), Adductus, Varus, and finally Equinus. Equinus is corrected last, often requiring a percutaneous Achilles tenotomy once the other deformities have been fully corrected.

Question 1883

Topic: Pediatric Hip
A 12-year-old male with a BMI > 95th percentile presents with hip pain and is diagnosed with a Slipped Capital Femoral Epiphysis (SCFE). Which of the following is the strongest indication for prophylactic in situ pinning of the asymptomatic contralateral hip?
. Age greater than 14 years at presentation
. Presence of a moderate slip angle (30-50 degrees) on the affected side
. Underlying endocrinopathy, such as hypothyroidism
. Male sex and African American descent
. History of prior hip trauma

Correct Answer & Explanation

. Underlying endocrinopathy, such as hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is strongly indicated in patients with underlying endocrinopathies (e.g., hypothyroidism, growth hormone deficiency) or renal osteodystrophy. These conditions dramatically increase the risk of bilateral involvement. Other indications include inability to follow up, radiation therapy, and open triradiate cartilage (though age and triradiate status are debated, endocrinopathy is universally agreed upon).

Question 1884

Topic: Pediatric Upper Extremity & Spine

A 12-year-old premenarchal female is evaluated for Adolescent Idiopathic Scoliosis (AIS). She has a right thoracic curve. Her Risser stage is 0. Based on SRS (Scoliosis Research Society) guidelines, which of the following is the primary indication for initiating full-time bracing treatment?

. Curve magnitude of 15 to 20 degrees with documented progression of 5 degrees
. Any curve greater than 45 degrees regardless of progression
. Curve magnitude of 20 to 25 degrees at initial presentation
. Curve magnitude of 25 to 45 degrees with documented progression, or initial curve 30 to 39 degrees
. Curve magnitude of 10 degrees combined with a positive family history

Correct Answer & Explanation

. Curve magnitude of 25 to 45 degrees with documented progression, or initial curve 30 to 39 degrees

Explanation

The SRS guidelines for bracing in AIS include patients who are skeletally immature (Risser 0-2, premenarchal) with a curve of 25 to 29 degrees that has documented progression of 5 degrees or more, or an initial presentation with a curve between 30 and 39 degrees. Curves > 45-50 degrees are generally indications for surgery, while curves < 25 degrees without documented progression are observed.

Question 1885

Topic: 4. Pediatrics

A 13-year-old overweight male presents with an acute exacerbation of chronic right groin and knee pain. He walks with an externally rotated gait. Radiographs confirm a severe Slipped Capital Femoral Epiphysis (SCFE).

Pathophysiologically, the slippage in SCFE occurs primarily through which specific histological zone of the proximal femoral physis?

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

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

Slipped Capital Femoral Epiphysis (SCFE) typically occurs due to mechanical shear forces across a weakened physis during the adolescent growth spurt. Histologically and biomechanically, the weakest layer of the growth plate is the zone of hypertrophy. The slippage classically occurs through this layer because the chondrocytes are enlarged, and the extracellular matrix is sparse compared to the reserve or proliferative zones, making it highly susceptible to shear stress.

Question 1886

Topic: Pediatric Hip

A 12-year-old obese male presents with left knee pain and a limp. Physical examination demonstrates obligate external rotation of the left hip during passive flexion. He is diagnosed with a stable Slipped Capital Femoral Epiphysis (SCFE) and undergoes in situ pinning with a single cannulated screw. What is the most common long-term complication of this treated condition?

. Avascular necrosis (AVN)
. Chondrolysis
. Femoral-acetabular impingement (FAI)
. Slipped contralateral epiphysis
. Subtrochanteric fracture

Correct Answer & Explanation

. Femoral-acetabular impingement (FAI)

Explanation

Femoral-acetabular impingement (FAI), specifically cam-type impingement, is the most common complication after in situ pinning of a SCFE. The prominent anterior metaphysis created by the posterior slip abuts the acetabular rim during flexion and internal rotation. AVN is a dreaded complication but is much more common in unstable SCFE. Chondrolysis is associated with unrecognized joint penetration by the hardware.

Question 1887

Topic: Pediatric Hip

A 12-year-old obese male presents with left thigh pain and a limp. The provided radiograph is shown.

He is diagnosed with a Slipped Capital Femoral Epiphysis (SCFE). What is the most widely accepted indication for prophylactic pinning of the contralateral hip?

. Initial presentation with a severe slip angle > 50 degrees
. Age < 10 for girls or < 12 for boys, or underlying endocrinopathy
. Open triradiate cartilage at the time of presentation
. Positive family history of SCFE in a first-degree relative
. Body Mass Index (BMI) > 99th percentile for age

Correct Answer & Explanation

. Age < 10 for girls or < 12 for boys, or underlying endocrinopathy

Explanation

Prophylactic pinning of the contralateral hip is generally indicated in patients with metabolic or endocrine disorders (e.g., hypothyroidism, renal osteodystrophy) and in patients presenting at a very young age (girls <10, boys <12) due to a substantially increased risk of a contralateral slip. Recent literature also strongly weights the modified Oxford bone age score.

Question 1888

Topic: 4. Pediatrics
A 9-year-old boy sustains a distal femur fracture. Radiographs demonstrate a fracture line propagating along the physis and exiting through the metaphysis, producing a small metaphyseal bone fragment (Thurston-Holland fragment). Based on the Salter-Harris classification, what type of fracture is this, and what is the typical expectation regarding growth arrest?
. Type I; Excellent prognosis, rarely affects growth
. Type II; Most common type, usually does not affect growth, though distal femur location carries a uniquely higher risk
. Type III; Intra-articular fracture with high risk of growth arrest
. Type IV; Crosses the physis, requires anatomic reduction to prevent bar formation
. Type V; Crush injury, universally poor prognosis

Correct Answer & Explanation

. Type II; Most common type, usually does not affect growth, though distal femur location carries a uniquely higher risk

Explanation

A fracture that propagates through the physis and exits through the metaphysis (creating a Thurston-Holland fragment) is a Salter-Harris Type II fracture. It is the most common physeal fracture pattern. Because the germinal layers of the physis remain attached to the epiphysis, the general prognosis for growth is good. However, one must recognize that Type II fractures of the distal femur inherently carry a high risk of growth arrest (up to 40-50%) compared to other locations.

Question 1889

Topic: Pediatric Upper Extremity & Spine
A 6-year-old girl falls on an outstretched hand and sustains a completely displaced, extension-type supracondylar humerus fracture (Gartland Type III). On physical examination, she cannot actively flex the interphalangeal joint of her thumb or the distal interphalangeal joint of her index finger. Which specific nerve structure is most likely injured?
. Ulnar nerve
. Radial nerve
. Anterior interosseous nerve (AIN)
. Posterior interosseous nerve (PIN)
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior interosseous nerve (AIN)

Explanation

The anterior interosseous nerve (AIN), a motor branch of the median nerve, is the most commonly injured nerve in extension-type pediatric supracondylar humerus fractures (particularly with posterolateral displacement). It innervates the flexor pollicis longus (FPL), the radial half of the flexor digitorum profundus (FDP), and the pronator quadratus. Deficits manifest clinically as the inability to form an 'OK' sign.

Question 1890

Topic: Pediatric Hip

A 12-year-old boy presents with left knee pain and an antalgic gait. Examination reveals obligate external rotation of the left hip during passive flexion.

Radiographs confirm a Slipped Capital Femoral Epiphysis (SCFE). Which of the following factors is considered an absolute indication for prophylactic in situ pinning of the contralateral, asymptomatic hip?

. Patient age greater than 14 years
. Male sex
. Underlying endocrine disorder (e.g., hypothyroidism)
. High body mass index (BMI > 95th percentile)
. Southwick angle greater than 50 degrees on the affected side

Correct Answer & Explanation

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

Explanation

The risk of developing a contralateral slip in a patient with an initial unilateral SCFE ranges from 20-40% overall, but approaches 100% in patients with an underlying endocrinopathy (such as hypothyroidism, growth hormone deficiency, or panhypopituitarism) or a history of radiation therapy to the pelvis. In these specific populations, prophylactic pinning of the contralateral hip is absolutely indicated.

Question 1891

Topic: Pediatric Upper Extremity & Spine
According to the Lenke classification system for Adolescent Idiopathic Scoliosis (AIS), curve flexibility is a key determinant in selecting fusion levels. A scoliotic curve is defined as 'structural' if it meets which of the following radiographic criteria on coronal side-bending films?
. Cobb angle corrects to less than 25 degrees
. Cobb angle fails to correct to less than 25 degrees
. Apical vertebral translation is greater than 2 cm
. Thoracic kyphosis (T2-T12) measures greater than +40 degrees
. Apical vertebral rotation is Nash-Moe Grade III or higher

Correct Answer & Explanation

. Cobb angle fails to correct to less than 25 degrees

Explanation

In the Lenke classification of AIS, the distinction between a major/structural curve and a minor/non-structural curve dictates the levels to be fused. A curve is considered 'structural' if the Cobb angle remains at 25 degrees or greater on a maximum voluntary supine side-bending radiograph. Additionally, regional sagittal kyphosis of >= +20 degrees also defines a proximal thoracic or main thoracic curve as structural.

Question 1892

Topic: Pediatric Hip

A 12-year-old obese boy presents with vague left thigh and knee pain. He is diagnosed with a Slipped Capital Femoral Epiphysis (SCFE) as seen in similar clinical scenarios.

During percutaneous in-situ fixation, unrecognized penetration of the guide wire into the hip joint occurs. What is the most likely specific complication resulting from this technical error?

. Chondrolysis
. Avascular necrosis
. Osteomyelitis
. Slipped progression
. Heterotopic ossification

Correct Answer & Explanation

. Chondrolysis

Explanation

Chondrolysis is a severe complication of SCFE characterized by rapid destruction of the articular cartilage. While it can occur idiopathically, its most established iatrogenic cause is unrecognized intra-articular hardware penetration. The 'approach-withdraw' fluoroscopic technique is required during pinning to assure pins are entirely intraosseous. Avascular necrosis (AVN) is usually due to damage to the epiphyseal blood supply (retinacular vessels) secondary to the initial displacement, forceful closed reduction, or posterosuperior pin placement.

Question 1893

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, it is noted that the anterior straps are overly tightened, causing hyperflexion of the hips. Which of the following nerve palsies is most commonly associated with this specific positioning error?

. Sciatic nerve
. Femoral nerve
. Obturator nerve
. Superior gluteal nerve
. Lateral femoral cutaneous nerve

Correct Answer & Explanation

. Femoral nerve

Explanation

In a Pavlik harness, excessive flexion (over-tightening of the anterior straps) can compress the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy (manifesting as decreased quadriceps function). Conversely, excessive abduction (over-tightening of the posterior straps) places the hip at significant risk for avascular necrosis (AVN) of the femoral head.

Question 1894

Topic: 4. Pediatrics
A 3-year-old girl is evaluated for severe, progressive bilateral genu varum. Radiographs demonstrate medial metaphyseal beaking, fragmentation, and depression of the proximal medial tibial physis. According to the Langenskiรถld classification of infantile Blount's disease, at which stage does an overt physeal bony bar (epiphyseal-metaphyseal bridge) definitively form across the medial physis, conferring a high risk of recurrence without bar excision?
. Stage II
. Stage III
. Stage IV
. Stage V
. Stage VI

Correct Answer & Explanation

. Stage V

Explanation

The Langenskiรถld classification describes progressive radiographic changes in infantile Blount disease. Stage I-IV show worsening metaphyseal beaking and stepping. Stage V shows a deep cleft separating the medial epiphysis into two portions. Stage VI is definitively characterized by the formation of a solid medial physeal bridge (bony bar) between the epiphysis and metaphysis, halting medial growth completely and often requiring bar resection along with osteotomy.

Question 1895

Topic: Pediatric Hip

A 13-year-old obese male presents with left hip pain and an obligatory external rotation of the left hip when it is passively flexed. Radiographs confirm a severe left slipped capital femoral epiphysis (SCFE).

Which of the following patient characteristics is an absolute indication for prophylactic pinning of the contralateral asymptomatic right hip?

. Patient age greater than 14 years at presentation
. Presence of a diagnosed endocrine disorder
. Severe slip angle (>50 degrees) on the symptomatic side
. Male gender with a BMI > 95th percentile
. Inability to ambulate on the affected limb

Correct Answer & Explanation

. Presence of a diagnosed endocrine disorder

Explanation

Prophylactic pinning of the contralateral asymptomatic hip in a patient with a unilateral SCFE is controversial for standard cases, but it is unequivocally recommended for patients with underlying endocrine disorders (such as hypothyroidism, panhypopituitarism, and renal osteodystrophy). These patients have an exceptionally high incidence of bilateral involvement. Other factors like young age (<10 years) or open triradiate cartilage may also sway a surgeon toward prophylactic pinning.

Question 1896

Topic: 4. Pediatrics

A 4-month-old infant is being treated with a Pavlik harness for a completely dislocated left hip (Developmental Dysplasia of the Hip). After 3 weeks of strict harness wear, a dynamic ultrasound demonstrates that the left hip remains persistently dislocated. What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 3 to 4 weeks
. Adjust the anterior straps to increase hip flexion past 120 degrees
. Transition to a rigid abduction orthosis or perform a closed reduction and spica casting
. Perform an immediate open reduction and Dega pelvic osteotomy
. Discontinue the harness and delay further intervention until the child is walking

Correct Answer & Explanation

. Transition to a rigid abduction orthosis or perform a closed reduction and spica casting

Explanation

If a hip remains dislocated after 3 to 4 weeks of compliant Pavlik harness use, it is considered a failure, and the harness must be abandoned to prevent 'Pavlik harness disease' (posterior acetabular wear and worsening of the dysplasia). Increasing flexion past 110-120 degrees places the child at high risk for femoral nerve palsy. The next appropriate step is either transitioning to a rigid abduction orthosis (like an Ilfeld splint) or performing a closed reduction under anesthesia followed by spica casting.

Question 1897

Topic: 4. Pediatrics

A 13-year-old elite baseball pitcher presents with vague, insidious onset shoulder pain that is worst during the deceleration phase of throwing. He denies any acute pop or trauma. Radiographs reveal widening and lateral fragmentation of the proximal humeral physis compared to the contralateral shoulder. What is the most appropriate initial management?

. Corticosteroid injection into the subacromial space
. Immediate surgical epiphyseodesis to prevent slippage
. Complete cessation of throwing for 3 months followed by a structured return-to-throw program
. Continuation of throwing with a strict pitch count limit
. Arthroscopic labral repair and capsular plication

Correct Answer & Explanation

. Complete cessation of throwing for 3 months followed by a structured return-to-throw program

Explanation

The patient is presenting with 'Little League Shoulder,' which is proximal humeral epiphysiolysis. It is an overuse injury caused by repetitive rotational stress on the open physis during the throwing motion. The mainstay of treatment is absolute rest from throwing, typically for 3 months, or until the patient is completely pain-free and radiographs show healing of the physis. Once healed, a gradual return-to-throw program focusing on pitching mechanics is initiated.

Question 1898

Topic: 4. Pediatrics

A neonate is diagnosed with achondroplasia, the most common form of short-limb dwarfism. This condition is primarily characterized by a defect in the proliferation and hypertrophy of chondrocytes in the physis. Which specific genetic mutation and inheritance pattern is most commonly responsible for this disorder?

. COL1A1 gene mutation, Autosomal Dominant
. COMP gene mutation, Autosomal Dominant
. FGFR3 gene mutation, Autosomal Dominant
. FGFR3 gene mutation, Autosomal Recessive
. SOX9 gene mutation, X-linked Dominant

Correct Answer & Explanation

. FGFR3 gene mutation, Autosomal Dominant

Explanation

Achondroplasia is caused by an activating point mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene. The inheritance pattern is Autosomal Dominant, although approximately 80% of cases occur as sporadic de novo mutations, which are strongly associated with advanced paternal age. The mutant FGFR3 is constitutively active and functions as an abnormal inhibitor of chondrocyte proliferation in the proliferative zone of the physis, leading to diminished endochondral ossification.

Question 1899

Topic: Pediatric Hip



A 13-year-old obese male presents with acute-on-chronic hip and knee pain and an inability to bear weight on the affected limb. Radiographs confirm an unstable slipped capital femoral epiphysis (SCFE). He is taken to the operating room for urgent in-situ pinning. What is the most significant complication associated with attempting a forceful, intentional closed reduction of this deformity prior to hardware placement?

. Chondrolysis of the hip joint
. Femoral head osteonecrosis (avascular necrosis)
. Premature closure of the greater trochanteric apophysis
. Progression of the slip post-operatively
. Anterior labral tear

Correct Answer & Explanation

. Femoral head osteonecrosis (avascular necrosis)

Explanation

An unstable SCFE (defined as the inability to bear weight even with crutches) already carries a high risk of osteonecrosis. Attempting a forceful closed reduction further disrupts the fragile retinacular vascular supply to the femoral epiphysis, significantly increasing the risk of iatrogenic avascular necrosis. Gentle reduction by positioning may occur naturally, but intentional forceful reduction is contraindicated.

Question 1900

Topic: Pediatric Hip

A 4-month-old infant with developmental dysplasia of the hip (DDH) has been treated with a Pavlik harness for exactly 4 weeks. Serial ultrasounds show the left hip remains persistently dislocated and irreducible in the harness. What is the most appropriate next step in the management of this patient?

. Continue the Pavlik harness for an additional 4 weeks to allow further remodeling
. Transition immediately to a rigid hip abduction orthosis (e.g., Ilfeld splint)
. Discontinue the harness and proceed with closed reduction and spica casting under general anesthesia
. Open reduction via an anterior approach with a Salter pelvic osteotomy
. Varus derotational osteotomy of the proximal femur

Correct Answer & Explanation

. Discontinue the harness and proceed with closed reduction and spica casting under general anesthesia

Explanation

If a hip remains dislocated after 3 to 4 weeks of strict Pavlik harness use, it is deemed a failure of the harness. The harness must be discontinued immediately to prevent 'Pavlik harness disease' (erosion of the posterior acetabular wall and increased risk of avascular necrosis). The standard next step is an exam under anesthesia, arthrogram, and closed reduction with spica casting.

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