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4. Pediatrics MCQs

Practice Set 97 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 1921

Topic: Pediatric Hip
A 12-year-old obese boy presents with a left-sided slipped capital femoral epiphysis (SCFE). Which of the following represents the strongest indication for prophylactic in situ pinning of the contralateral, asymptomatic hip?
. Age greater than 14 years
. Male gender
. Presence of an endocrine disorder
. Grade III slip on the symptomatic side
. Acute-on-chronic presentation

Correct Answer & Explanation

. Presence of an endocrine disorder

Explanation

The presence of an underlying endocrine disorder (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy) is a strong risk factor for bilateral SCFE, with some studies reporting nearly 100% eventual bilateral involvement. Prophylactic pinning of the contralateral hip is highly recommended in these patients. Other indications include prior radiation therapy and age younger than 10.

Question 1922

Topic: Pediatric Hip

A 6-week-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a routine follow-up, the parents report that the child has stopped actively kicking the affected leg. On physical examination, there is an absent patellar reflex and decreased active knee extension. The harness is found to be in excessive hyperflexion. Which of the following nerves is most likely compressed?

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

Correct Answer & Explanation

. Femoral nerve

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment, usually resulting from hyperflexion of the hip (anterior straps too tight). It manifests as decreased spontaneous movement of the leg, specifically decreased active knee extension (quadriceps weakness) and an absent patellar reflex. The treatment involves loosening the anterior straps or temporarily removing the harness.

Question 1923

Topic: 4. Pediatrics

A 2-week-old infant is being treated for idiopathic congenital talipes equinovarus using the Ponseti method of serial casting.

According to this method, the components of the deformity must be corrected sequentially. Which of the following represents the correct sequence of correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method addresses clubfoot deformities in the order summarized by the mnemonic CAVE: Cavus, Adductus, Varus, Equinus. The cavus is corrected first by supinating the forefoot to elevate the first ray. Next, the adductus and varus are simultaneously corrected by abducting the forefoot around the fulcrum of the talar head. Finally, the equinus is corrected, which frequently requires a percutaneous Achilles tenotomy.

Question 1924

Topic: 4. Pediatrics

A 13-year-old obese boy presents with right thigh pain and a noticeable limp.

Radiographs confirm a slipped capital femoral epiphysis (SCFE). Pathologically, the biomechanical failure and slippage in a SCFE occurs through which specific 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) represents a Salter-Harris Type I equivalent fracture. The mechanical failure occurs through the zone of hypertrophy of the physis. This zone is mechanically the weakest because the cells are large, lack structural integrity, and the extracellular matrix is diminished.

Question 1925

Topic: 4. Pediatrics

A 2-week-old infant presents to the clinic with idiopathic congenital talipes equinovarus (clubfoot).

The parents agree to proceed with the Ponseti method of serial casting. According to the foundational principles of the Ponseti technique, what is the correct sequence of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The Ponseti method strictly follows a specific order of deformity correction, easily remembered by the mnemonic CAVE: Cavus (corrected by elevating the first ray), Adductus, Varus, and finally Equinus. The equinus is corrected last, often requiring a percutaneous Achilles tenotomy.

Question 1926

Topic: Pediatric Hip

A 6-week-old female infant is evaluated for developmental dysplasia of the hip (DDH). Ultrasound is performed, and an alpha angle of 45 degrees is noted on the right hip. She is prescribed a Pavlik harness. Which of the following complications is most likely to occur if the harness is placed in excessive hip flexion (greater than 120 degrees)?

. Femoral nerve palsy
. Sciatic nerve palsy
. Avascular necrosis of the femoral head
. Obturator nerve palsy
. Inferior hip dislocation

Correct Answer & Explanation

. Femoral nerve palsy

Explanation

In the use of a Pavlik harness for DDH, excessive hip flexion (typically > 120 degrees) is known to cause femoral nerve palsy due to compression of the nerve against the inguinal ligament. Excessive abduction is associated with avascular necrosis of the femoral head.

Question 1927

Topic: Pediatric Hip

A 13-year-old overweight boy presents with a 3-week history of right groin and knee pain. He walks with a limp. On examination, when his right hip is flexed, it obligatorily externally rotates. Radiographs show a slip of the proximal femoral epiphysis. Which radiographic line is used to diagnose this condition?

. Shenton's line
. Hilgenreiner's line
. Klein's line
. Perkin's line
. Ward's triangle

Correct Answer & Explanation

. Klein's line

Explanation

The clinical scenario describes Slipped Capital Femoral Epiphysis (SCFE). Klein's line is drawn along the superior edge of the femoral neck on an AP pelvic radiograph. In a normal hip, this line should intersect a portion of the lateral capital femoral epiphysis. In SCFE, the line passes superior to the epiphysis or intersects less of it compared to the contralateral normal side (Trethowan's sign).

Question 1928

Topic: Pediatric Hip
A 6-year-old boy presents with a painless limp of several months' duration. Examination reveals restricted hip abduction and internal rotation. Radiographs demonstrate sclerosis and flattening of the capital femoral epiphysis consistent with Legg-Calvé-Perthes disease. According to the Waldenström classification, what is the sequence of radiographic stages in this disease?
. Fragmentation, Initial, Reossification, Healed
. Initial, Fragmentation, Reossification, Healed
. Reossification, Initial, Fragmentation, Healed
. Initial, Reossification, Fragmentation, Healed
. Healed, Reossification, Fragmentation, Initial

Correct Answer & Explanation

. Initial, Fragmentation, Reossification, Healed

Explanation

The Waldenström classification of Legg-Calvé-Perthes disease outlines four stages: 1) Initial (infarction/necrosis) stage, characterized by sclerosis and cessation of growth; 2) Fragmentation stage, where the epiphysis appears fragmented as necrotic bone is resorbed; 3) Reossification stage, where new bone forms; and 4) Healed (residual) stage, where the bone is fully reossified, though often with a deformed head.

Question 1929

Topic: Pediatric Hip

A 13-year-old obese male underwent in situ single-screw pinning for a severe, unstable slipped capital femoral epiphysis (SCFE) 6 months ago. He now complains of progressive hip stiffness and pain. Radiographs demonstrate marked concentric joint space narrowing of the affected hip without evidence of avascular necrosis.

What is the most likely diagnosis?

. Deep joint space infection
. Heterotopic ossification
. Chondrolysis
. Screw penetration into the joint
. Cam-type femoroacetabular impingement

Correct Answer & Explanation

. Chondrolysis

Explanation

Chondrolysis is a known complication of SCFE, characterized by acute articular cartilage destruction, concentric joint space narrowing (typically <3 mm), stiffness, and pain. It is more common in severe slips, unstable slips, and historically with spica cast immobilization or unrecognized intra-articular hardware penetration, though it can occur idiopathically post-slip.

Question 1930

Topic: Pediatric Lower Extremity

When treating a rigid idiopathic clubfoot using the Ponseti method of serial casting, what is the correct sequence of deformity correction?

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

Correct Answer & Explanation

. Cavus, Equinus, Varus, Adductus

Explanation

The Ponseti method dictates a specific sequence of correction commonly remembered by the acronym CAVE. Cavus is corrected first by elevating the first ray (supinating the forefoot). Then the midfoot Adductus and hindfoot Varus are corrected simultaneously by gradually abducting the foot around the fixed talar head. Equinus is corrected last, often requiring a percutaneous Achilles tenotomy.

Question 1931

Topic: 4. Pediatrics
A 6-year-old child presents after a fall from monkey bars with a widely displaced extension-type Gartland III supracondylar humerus fracture. On initial examination, the hand is pink but the radial pulse is not palpable. After emergent closed reduction and percutaneous pinning in the operating room, the radial pulse remains absent, but the hand remains warm and pink with a capillary refill of less than 2 seconds. What is the most appropriate next step in management?
. Immediate exploration of the brachial artery
. CT angiography of the upper extremity
. Observation and hospital admission for serial neurovascular checks
. Administration of intra-arterial vasodilators
. Prophylactic volar forearm fasciotomy

Correct Answer & Explanation

. Observation and hospital admission for serial neurovascular checks

Explanation

The management of a 'pink, pulseless' hand following reduction and pinning of a pediatric supracondylar humerus fracture is observation. Collateral circulation in children is typically excellent and sufficient to maintain viability of the limb. Arterial exploration is indicated only if the hand is 'white and pulseless' (dysvascular) after a successful reduction.

Question 1932

Topic: Pediatric Hip

A 12-year-old obese male presents with a stable slipped capital femoral epiphysis (SCFE) of the left hip.

Which of the following factors is the strongest indication for prophylactic in situ pinning of the asymptomatic contralateral right hip?

. Body Mass Index greater than the 95th percentile
. Slip angle greater than 50 degrees on the affected side
. Age greater than 14 years at presentation
. Presence of an underlying endocrine disorder (e.g., hypothyroidism)
. Male gender

Correct Answer & Explanation

. Presence of an underlying endocrine disorder (e.g., hypothyroidism)

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial but is strongly indicated in patients with a high risk of bilateral involvement. Risk factors predicting contralateral slip include an underlying endocrine disorder (such as hypothyroidism, panhypopituitarism, or renal osteodystrophy), prior radiation therapy, or age of presentation less than 10 years (or low modified Oxford bone age score).

Question 1933

Topic: Pediatric Hip

A 4-month-old female with developmental dysplasia of the hip (DDH) has been treated with a Pavlik harness for 4 weeks.

Clinical and ultrasonographic evaluations confirm that the left hip remains persistently dislocated. What is the most appropriate next step in management?

. Continue Pavlik harness treatment for an additional 4 weeks
. Transition to a rigid abduction orthosis (e.g., Ilfeld or Rhino brace)
. Perform an immediate open reduction and spica casting
. Perform a proximal femoral varus derotational osteotomy
. Perform a pelvic (Salter) osteotomy

Correct Answer & Explanation

. Transition to a rigid abduction orthosis (e.g., Ilfeld or Rhino brace)

Explanation

If a Pavlik harness fails to achieve reduction within 3 to 4 weeks, its use should be discontinued to prevent complications such as 'Pavlik harness disease' (erosion of the posterior acetabular lip) and avascular necrosis. The AAOS guidelines recommend transitioning to a rigid or semi-rigid abduction orthosis as the next step before considering closed or open surgical reduction.

Question 1934

Topic: Pediatric Lower Extremity

The Ponseti method is the gold standard for the treatment of idiopathic clubfoot (talipes equinovarus). To avoid a 'rocker-bottom' deformity, in what precise order must the components of the clubfoot deformity be corrected?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

The components of clubfoot are corrected sequentially according to the mnemonic CAVE: Cavus (by elevating the first ray to supinate the forefoot), Adductus, Varus, and lastly Equinus. Attempting to correct equinus too early, before the calcaneus is fully abducted, leads to a midfoot breach and a rocker-bottom foot deformity. Equinus is often addressed at the end with an Achilles tenotomy.

Question 1935

Topic: Pediatric Hip

A 13-year-old obese boy presents with non-traumatic knee pain and is noted to have an obligate external rotation of his hip when it is passively flexed. Radiographs confirm the diagnosis.

He is unable to bear weight on the affected extremity. What is the primary complication associated with this presentation compared to a patient who is able to bear weight?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Femoroacetabular impingement (FAI)
. Slipped capital femoral epiphysis on the contralateral side
. Leg length discrepancy

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

The patient has an unstable slipped capital femoral epiphysis (SCFE), defined by Loder criteria as the inability to bear weight even with crutches. Unstable SCFE has a significantly higher rate of avascular necrosis (up to nearly 50% in some series) compared to stable SCFE (which has an AVN rate near 0%). Both stable and unstable SCFEs can lead to impingement or contralateral slips, but AVN is the critical distinguishing risk factor of an unstable slip.

Question 1936

Topic: Pediatric Hip

A 13-year-old obese male presents to the emergency department with severe left thigh pain and an inability to bear weight on the left leg for the past 2 weeks, even with crutches. Radiographs demonstrate a slipped capital femoral epiphysis.

Which of the following defines this as an 'unstable' SCFE, and what is the primary associated complication risk?

. Symptom duration less than 3 weeks; high risk of chondrolysis
. Inability to bear weight; high risk of avascular necrosis (AVN)
. Slip angle greater than 50 degrees; high risk of AVN
. Open triradiate cartilage; high risk of nonunion
. Presence of an effusion on ultrasound; high risk of septic arthritis

Correct Answer & Explanation

. Inability to bear weight; high risk of avascular necrosis (AVN)

Explanation

The Loder classification defines an unstable SCFE by the patient's inability to bear weight, even with assistive devices. This distinction is critical because unstable SCFEs carry a much higher risk of avascular necrosis (AVN) of the femoral head (approaching 47%) compared to stable SCFEs (<10%). Symptom duration previously defined acute vs. chronic but doesn't dictate stability.

Question 1937

Topic: Pediatric Hip

A 4-month-old infant is being treated with a Pavlik harness for Developmental Dysplasia of the Hip (DDH). At the two-week follow-up, the mother notes that the baby is not kicking or extending the knee on the treated side, though ankle and toe movements are intact. Which of the following is the most likely cause of this finding?

. Avascular necrosis of the femoral head due to excessive abduction
. Femoral nerve palsy due to hyperflexion of the hip
. Obturator nerve palsy due to excessive abduction
. Sciatic nerve compression from the posterior harness straps
. Slipped capital femoral epiphysis caused by the harness

Correct Answer & Explanation

. Femoral nerve palsy due to hyperflexion of the hip

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment. It is typically caused by excessive hyperflexion of the hip in the anterior straps. It presents clinically as an inability to extend the knee (quadriceps weakness) or a lack of kicking on the affected side. The treatment is to temporarily loosen the anterior straps or remove the harness until nerve function returns.

Question 1938

Topic: Pediatric Upper Extremity & Spine
A 6-year-old boy falls from the monkey bars and sustains a completely displaced, extension-type supracondylar humerus fracture (Gartland Type III). During your neurologic examination in the emergency department, you ask the child to make an 'OK' sign with his hand, but he is unable to flex the interphalangeal joint of his thumb and the distal interphalangeal joint of his index finger. Which nerve is most likely injured?
. Radial nerve
. Ulnar 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 supracondylar humerus fractures (particularly those that displace posterolaterally). It innervates the flexor pollicis longus (FPL), the radial half of the flexor digitorum profundus (FDP to index and middle fingers), and the pronator quadratus. An AIN palsy clinically presents as the inability to form an 'OK' sign (pincer grasp) due to weakness of the FPL and FDP.

Question 1939

Topic: Pediatric Hip

A 6-week-old female is diagnosed with a completely dislocated left hip (Graf IV) and treated with a Pavlik harness. After 4 weeks of compliant wear, dynamic ultrasound shows the hip remains persistently dislocated.

What is the most appropriate next step in management?

. Continue the Pavlik harness for an additional 4 weeks
. Transition to a rigid abduction orthosis (e.g., Ilfeld) or proceed to closed reduction and spica casting
. Perform an open reduction via a medial approach
. Perform a proximal femoral varus derotational osteotomy
. Observe and reassess at 6 months of age

Correct Answer & Explanation

. Transition to a rigid abduction orthosis (e.g., Ilfeld) or proceed to closed reduction and spica casting

Explanation

According to established AAOS guidelines for Developmental Dysplasia of the Hip (DDH), failure of a Pavlik harness to reduce a dislocated hip after 3-4 weeks is an indication to discontinue the harness to prevent 'Pavlik harness disease' (acetabular damage/erosion). The appropriate next step is transitioning to a rigid abduction orthosis or proceeding directly to a closed reduction and spica casting in the operating room.

Question 1940

Topic: Pediatric Hip

A 12-year-old obese male presents with a mild, stable right slipped capital femoral epiphysis (SCFE).

Which of the following conditions is an absolute indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Age greater than 14 years at presentation
. Obesity (BMI > 95th percentile)
. Presence of an underlying endocrine disorder
. African American race
. Male sex

Correct Answer & Explanation

. Presence of an underlying endocrine disorder

Explanation

The risk of developing a contralateral SCFE is approximately 20-40% overall. However, prophylactic pinning of the contralateral asymptomatic hip is strongly indicated in patients with underlying endocrinopathies (e.g., hypothyroidism, growth hormone deficiency), renal osteodystrophy, prior pelvic radiation therapy, or an unusually young age at presentation (<10 years), as their risk of bilateral involvement approaches 100%.

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