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4. Pediatrics MCQs

Practice Set 34 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 661

Topic: 4. Pediatrics

A newborn is noted to have rhizomelic shortening of the limbs, frontal bossing, and midface hypoplasia. The condition is linked to a gain-of-function mutation in the FGFR3 gene. What is the effect of this mutation on the physis?

. Increased apoptosis in the hypertrophic zone
. Inhibition of chondrocyte proliferation in the proliferative zone
. Failure of mineralization in the zone of provisional calcification
. Premature closure of the reserve zone
. Increased osteoblast activity in the metaphysis

Correct Answer & Explanation

. Inhibition of chondrocyte proliferation in the proliferative zone

Explanation

Achondroplasia is caused by a constitutively active FGFR3 mutation. FGFR3 normally acts as a negative regulator of bone growth; its overactivity profoundly inhibits chondrocyte proliferation in the proliferative zone.

Question 662

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy falls from monkey bars and sustains a Gartland type III supracondylar humerus fracture. Examination reveals weakness in flexing the interphalangeal joint of the thumb. Which nerve is most likely injured?
. Ulnar nerve
. Anterior interosseous nerve
. Posterior interosseous nerve
. Superficial radial 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 pediatric supracondylar humerus fractures. AIN injury results in the inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger (OK sign).

Question 663

Topic: Pediatric Hip

A 13-year-old obese male complains of a 3-week history of dull, aching groin and knee pain. On examination, as the affected hip is flexed, it obligately rotates externally. Radiographs show a slip of the proximal femoral epiphysis. What is the most appropriate initial management?

. Closed reduction and spica casting
. In situ percutaneous screw fixation
. Open reduction and internal fixation
. Physical therapy and weight loss
. Proximal femoral osteotomy

Correct Answer & Explanation

. In situ percutaneous screw fixation

Explanation

Slipped capital femoral epiphysis (SCFE) is treated primarily with in situ percutaneous screw fixation to prevent further slippage. Closed reduction is contraindicated as it significantly increases the risk of avascular necrosis.

Question 664

Topic: Pediatric Hip

A 13-year-old obese boy presents with knee pain and a limp. On physical examination, as the affected hip is flexed, it obligatorily externally rotates. Radiographs show a widening of the proximal femoral physis with a "slip" of the epiphysis. What is the most severe common complication if this condition is treated with forceful closed reduction?

. Chondrolysis
. Avascular necrosis of the femoral head
. Rapid onset osteoarthritis
. Slipped capital femoral epiphysis of the contralateral hip
. Femoral neck nonunion

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Forceful closed reduction of a Slipped Capital Femoral Epiphysis (SCFE) significantly increases the risk of stretching or tearing the retinacular vessels, leading to iatrogenic avascular necrosis of the femoral head.

Question 665

Topic: Pediatric Hip

A 9-year-old girl with a BMI in the 95th percentile presents with right knee pain and an antalgic gait. Radiographs reveal a severe but stable slipped capital femoral epiphysis (SCFE). Given her atypical age for this condition, she is evaluated for an underlying metabolic condition associated with bilateral involvement. Which endocrine disorder is most strongly associated with her presentation?

. Hyperthyroidism
. Hypothyroidism
. Hyperparathyroidism
. Addison disease
. Cushing syndrome

Correct Answer & Explanation

. Hypothyroidism

Explanation

While typical SCFE occurs in overweight adolescents due to mechanical forces, bilateral presentations in atypical age groups (under 10 or over 16 years) strongly suggest an underlying endocrine disorder. Hypothyroidism is the most common endocrinopathy associated with SCFE in this demographic.

Question 666

Topic: 4. Pediatrics

A 13-year-old obese boy presents with a 3-week history of right groin pain and a limp. On examination, he has obligatory external rotation of the right hip with passive flexion. AP and frog-leg lateral radiographs show a widened right proximal femoral physis, and a line drawn along the superior neck does not intersect the epiphysis. What is the standard of care for this condition?

. Spica cast immobilization
. In situ fixation with a single cannulated screw
. Open reduction and internal fixation with multiple pins
. Core decompression of the femoral head
. Prophylactic fixation of the contralateral hip only

Correct Answer & Explanation

. In situ fixation with a single cannulated screw

Explanation

This patient has a slipped capital femoral epiphysis (SCFE). The standard treatment for a stable SCFE is in situ fixation using a single, centrally placed cannulated screw to prevent further slippage and promote early physeal closure.

Question 667

Topic: Pediatric Hip

A 12-year-old overweight boy presents with a 4-week history of left knee pain and a limp. Examination reveals obligate external rotation of the left hip during passive flexion. Radiographs confirm a Slipped Capital Femoral Epiphysis (SCFE). Which of the following accurately describes the true displacement of the epiphysis relative to the femoral neck?

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

Correct Answer & Explanation

. Posterior and inferior

Explanation

In SCFE, the femoral neck typically displaces anteriorly and superiorly relative to the epiphysis. Consequently, the epiphysis itself remains in the acetabulum and relatively displaces posteriorly and inferiorly.

Question 668

Topic: Pediatric Hip

A 6-week-old female infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). During follow-up, the parents report the infant has stopped kicking her legs, and the examiner notes absent active knee extension on the treated side. Which of the following is the most likely cause?

. Avascular necrosis of the femoral head
. Excessive abduction causing obturator nerve palsy
. Hyperflexion causing femoral nerve palsy
. Excessive extension causing sciatic nerve stretch
. Direct pressure from the anterior strap on the peroneal nerve

Correct Answer & Explanation

. Hyperflexion causing femoral nerve palsy

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by excessive flexion of the hip. Treatment involves loosening the anterior straps or temporarily discontinuing the harness until function returns.

Question 669

Topic: Pediatric Hip
A 6-year-old boy is diagnosed with Legg-Calvรฉ-Perthes disease. The treating surgeon uses the Herring lateral pillar classification to determine prognosis. Which radiographic feature defines a Herring Group C classification?
. No involvement of the lateral pillar
. Greater than 50% maintenance of lateral pillar height
. Less than 50% maintenance of lateral pillar height
. Complete extrusion of the femoral head
. Presence of a subchondral crescent sign

Correct Answer & Explanation

. Less than 50% maintenance of lateral pillar height

Explanation

The Herring classification evaluates the height of the lateral pillar of the femoral head during the fragmentation phase. Group C is defined by less than 50% maintenance of the lateral pillar height and carries the worst prognosis.

Question 670

Topic: Pediatric Upper Extremity & Spine

A 5-year-old girl sustains a widely displaced extension-type supracondylar humerus fracture. On presentation, her hand is pink, but the radial pulse is absent. After closed reduction and percutaneous pinning, her hand remains pink and well-perfused, but the radial pulse remains unpalpable. What is the most appropriate next step?

. Immediate open exploration of the brachial artery
. Angiography of the upper extremity
. Observation and admission for neurovascular monitoring
. Application of a warm compress and immediate discharge
. Removal of pins and transition to a cast

Correct Answer & Explanation

. Observation and admission for neurovascular monitoring

Explanation

The 'pink, pulseless hand' following reduction and pinning of a supracondylar humerus fracture indicates adequate collateral circulation. Current guidelines recommend close observation and monitoring rather than immediate vascular exploration.

Question 671

Topic: Pediatric Hip

A 13-year-old obese boy presents with a 3-week history of right thigh and knee pain. Physical examination reveals an obligatory external rotation of the right hip when it is passively flexed. Radiographs confirm a slipped capital femoral epiphysis (SCFE). What is the most appropriate definitive management?

. Closed reduction and spica casting
. In situ single cannulated screw fixation
. Immediate subtrochanteric osteotomy
. Open reduction and internal fixation with multiple pins
. Prolonged bed rest and skeletal traction

Correct Answer & Explanation

. In situ single cannulated screw fixation

Explanation

In situ fixation with a single, centrally placed, partially threaded cannulated screw is the gold standard definitive treatment for a stable slipped capital femoral epiphysis.

Question 672

Topic: 4. Pediatrics

You review a 35-year-old woman with progressively increased shortness of breath and lethargy after the birth of her first child. You send her for some pulmonary function tests, including measurement of gas transfer. Which of the following gases is usually used for measurement of gas transfer?

. Carbon dioxide
. Carbon monoxide
. Methane
. Nitrous oxide
. Oxygen

Correct Answer & Explanation

. Carbon monoxide

Explanation

Correct Answer: A- Carbon monoxide Explanation Carbon monoxide The Dlco (or diffusing capacity for carbon monoxide) is the standard method for measuring gas transfer from alveoli to red blood cells. Dlco is measured by looking at end-expiratory levels of carbon monoxide after inspiring a small amount and breath-holding. It is adjusted for haematocrit and alveolar volume. Conditions that affect the pulmonary vasculature and factors that lead to pulmonary fibrosis affect the Dlco. Carbon dioxide Carbon dioxide is incorrect. Dlco is measured by looking at end-expiratory levels of carbon monoxide after inspiring a small amount and breath-holding. Methane Methane is incorrect. Dlco is measured by looking at end-expiratory levels of carbon monoxide after inspiring a small amount and breath-holding. Nitrous oxide Nitrous oxide is incorrect. Dlco is measured by looking at end-expiratory levels of carbon monoxide after inspiring a small amount and breath-holding. Oxygen Oxygen is incorrect. Dlco is measured by looking at end- expiratory levels of carbon monoxide after inspiring a small amount and breath-holding.

Question 673

Topic: Pediatric Hip

A 13-year-old obese male presents with a painful limp and obligatory external rotation of the hip during flexion. He is diagnosed with a slipped capital femoral epiphysis (SCFE). Which blood supply to the femoral head is most at risk in this condition?

. Artery of the ligamentum teres
. Inferior gluteal artery
. Medial femoral circumflex artery
. Lateral femoral circumflex artery
. Obturator artery

Correct Answer & Explanation

. Medial femoral circumflex artery

Explanation

The lateral epiphyseal vessels, which are terminal branches of the medial femoral circumflex artery (MFCA), supply the majority of the femoral head. These vessels are highly vulnerable to stretching or kinking in SCFE, risking avascular necrosis.

Question 674

Topic: Pediatric Hip

In an 8-month-old female undergoing attempted closed reduction for developmental dysplasia of the hip (DDH), the surgeon encounters a block to concentric reduction. Which of the following is considered a primary intra-articular anatomic block to reduction in this condition?

. Inverted limbus (labrum)
. Contracted gluteus maximus
. Laxity of the round ligament
. Elongated transverse acetabular ligament
. Hypoplastic ligamentum teres

Correct Answer & Explanation

. Inverted limbus (labrum)

Explanation

Common intra-articular obstacles to closed reduction in DDH include an inverted limbus (labrum), hypertrophied pulvinar, a tight/constricted transverse acetabular ligament, and a hypertrophied ligamentum teres.

Question 675

Topic: Pediatric Upper Extremity & Spine
A 6-year-old falls from monkey bars and sustains a widely displaced Gartland Type III supracondylar humerus fracture. The hand is pink and warm, but the radial pulse is completely absent. What is the most appropriate next step in management?
. Immediate vascular surgery consult for arterial bypass
. Urgent closed reduction and percutaneous pinning
. Emergent upper extremity arteriogram
. Observation and elevation for 24 hours
. Open reduction with immediate brachial artery exploration

Correct Answer & Explanation

. Urgent closed reduction and percutaneous pinning

Explanation

A "pulseless but pink" hand after a displaced supracondylar fracture usually indicates arterial kinking or spasm rather than complete transection. Urgent closed reduction and percutaneous pinning typically restores the pulse.

Question 676

Topic: 4. Pediatrics

A 4-week-old female infant is found to have a positive Ortolani test during a routine pediatric examination. Ultrasound confirms developmental dysplasia of the hip (DDH). What is the preferred initial management?

. Observation with repeat ultrasound at 6 months
. Application of a Pavlik harness
. Closed reduction and spica casting
. Open reduction of the hip joint
. Bilateral triple pelvic osteotomies

Correct Answer & Explanation

. Application of a Pavlik harness

Explanation

The Pavlik harness is the gold standard initial treatment for reducible developmental dysplasia of the hip in infants under 6 months of age. It holds the hips in flexion and abduction, allowing for dynamic acetabular remodeling.

Question 677

Topic: 4. Pediatrics

A 13-year-old overweight boy complains of a vague right groin and knee pain for 3 weeks and walks with a limp. On examination, there is obligatory external rotation of the right hip as it is flexed. What is the most appropriate treatment?

. Physical therapy and protected weight-bearing
. In situ percutaneous screw fixation of the epiphysis
. Immediate total hip arthroplasty
. Bilateral hip spica casting
. Intra-articular corticosteroid injection

Correct Answer & Explanation

. In situ percutaneous screw fixation of the epiphysis

Explanation

The presentation is classic for Slipped Capital Femoral Epiphysis (SCFE). In situ fixation with a single percutaneous screw is the standard of care to stabilize the physis and prevent further slippage.

Question 678

Topic: 4. Pediatrics

A 6-year-old boy presents with an extension-type supracondylar humerus fracture. Examination reveals an inability to flex the interphalangeal joint of the thumb and the distal interphalangeal joint of the index finger. Which nerve is most likely injured?

. Radial nerve
. Ulnar nerve
. Anterior interosseous nerve
. Posterior interosseous nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior interosseous nerve

Explanation

The anterior interosseous nerve (AIN) is the most commonly injured nerve in extension-type pediatric supracondylar humerus fractures. It innervates the flexor pollicis longus and the flexor digitorum profundus to the index and middle fingers.

Question 679

Topic: Pediatric Hip

A 13-year-old obese boy undergoes in situ pinning for a stable, left-sided slipped capital femoral epiphysis (SCFE). Which of the following is the strongest indication for prophylactic pinning of the contralateral asymptomatic hip?

. Patient age over 15 years
. Male gender
. Presentation with thigh pain instead of knee pain
. Presence of an endocrine disorder such as hypothyroidism
. Slip angle greater than 50 degrees on the affected side

Correct Answer & Explanation

. Presence of an endocrine disorder such as hypothyroidism

Explanation

Prophylactic pinning of the contralateral hip in SCFE is highly recommended in patients with endocrine disorders (e.g., hypothyroidism, renal osteodystrophy) due to a significantly higher risk of bilateral involvement. Age less than 10 years at presentation is another strong indication.

Question 680

Topic: Pediatric Hip

An obese 13-year-old boy undergoes in-situ percutaneous pinning for a stable slipped capital femoral epiphysis (SCFE). Which of the following is the most common long-term complication associated with this condition?

. Avascular necrosis of the femoral head
. Chondrolysis
. Femoroacetabular impingement
. Nonunion
. Leg length discrepancy

Correct Answer & Explanation

. Femoroacetabular impingement

Explanation

The most common long-term complication after in-situ pinning of a SCFE is cam-type femoroacetabular impingement (FAI) due to the residual prominent anterior metaphysis. Avascular necrosis is more commonly seen in unstable SCFE.

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