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4. Pediatrics MCQs

Practice Set 326 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 6501

Topic: Pediatric Lower Extremity

A 12-year-old male soccer player complains of anterior knee pain that worsens with running and jumping. On examination, there is localized tenderness and swelling directly over the tibial tubercle. Radiographs show fragmentation of the tibial tubercle apophysis. What is the most likely diagnosis?

. Sinding-Larsen-Johansson syndrome
. Patellar tendinopathy
. Osgood-Schlatter disease
. Osteochondritis dissecans of the knee
. Patellofemoral pain syndrome

Correct Answer & Explanation

. Osgood-Schlatter disease

Explanation

Correct Answer: CPathophysiology:Osgood-Schlatter disease is a traction apophysitis of the tibial tubercle. It occurs in active adolescents (typically boys aged 12-15 and girls aged 10-13) during periods of rapid growth. Repetitive microtrauma from the pull of the patellar tendon on the unossified tibial tubercle leads to inflammation and microavulsions.Clinical Presentation:Patients present with anterior knee pain exacerbated by running, jumping, or kneeling. Examination reveals a prominent, tender tibial tubercle.Differential Diagnosis:Sinding-Larsen-Johansson syndrome is a similar traction apophysitis but occurs at the inferior pole of the patella. Patellofemoral pain syndrome presents with diffuse anterior knee pain without localized tubercle tenderness.

Question 6502

Topic: 4. Pediatrics

A 13-year-old obese male presents with a 3-week history of left groin pain and a limp. Physical examination reveals obligatory external rotation of the left hip during passive flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Through which histologic zone of the physis does the slippage primarily occur in this condition?

. Reserve zone
. Proliferative zone
. Zone of maturation
. Zone of hypertrophy
. Zone of provisional calcification

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

Correct Answer: D (Zone of hypertrophy)Slipped capital femoral epiphysis (SCFE) typically occurs through the zone of hypertrophy of the physis. This zone is mechanically the weakest due to the lack of collagen and the large size of the chondrocytes. The condition is most commonly seen in obese adolescents undergoing rapid growth spurts, where mechanical shear forces across the proximal femoral physis exceed the structural integrity of the hypertrophic zone.

Question 6503

Topic: 4. Pediatrics

A 2-week-old infant is brought to the clinic for management of congenital idiopathic clubfoot. The treating orthopedic surgeon plans to utilize the Ponseti method of serial casting. What is the correct sequence of deformity correction in this technique?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

Correct Answer: A (Cavus, Adductus, Varus, Equinus)The Ponseti method corrects the deformities of clubfoot in a specific, sequential order, remembered by the acronym CAVE: Cavus, Adductus, Varus, and Equinus. The cavus is corrected first by elevating the first ray to align the forefoot with the hindfoot. Subsequent casts correct the adductus and varus by abducting the foot around the head of the talus. Finally, the equinus is corrected, which often requires a percutaneous Achilles tenotomy.

Question 6504

Topic: 4. Pediatrics

A 13-year-old obese male presents with a 3-week history of left thigh and knee pain. On examination, he walks with an antalgic gait and his left hip obligatorily externally rotates when flexed. Radiographs confirm a slipped capital femoral epiphysis (SCFE). He undergoes in situ pinning with a single cannulated screw. Which of the following is the most devastating potential complication associated with this condition and its treatment, particularly if an unstable slip is aggressively reduced?

. Chondrolysis
. Avascular necrosis of the femoral head
. Femoroacetabular impingement
. Premature physeal closure
. Slipped capital femoral epiphysis of the contralateral hip

Correct Answer & Explanation

. Avascular necrosis of the femoral head

Explanation

Correct Answer: BAvascular necrosis (AVN) is the most devastating complication of Slipped Capital Femoral Epiphysis (SCFE). The risk is significantly higher in unstable slips (where the patient is unable to bear weight) and if forceful closed reduction is attempted prior to pinning. The standard of care isin situpinning to prevent further slippage without attempting to anatomically reduce the physis, thereby protecting the tenuous blood supply. Chondrolysis is another severe complication but is less common today with the avoidance of joint penetration by hardware. Contralateral slip occurs in up to 20-40% of patients but is not as acutely devastating as AVN.

Question 6505

Topic: Pediatric Lower Extremity

A newborn male is evaluated in the nursery and found to have a rigid, inward-turning left foot. The deformity consists of midfoot cavus, forefoot adductus, hindfoot varus, and hindfoot equinus. The Ponseti method of serial casting is initiated. What is the correct sequence of deformity correction in the Ponseti method?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

Correct Answer: BThe Ponseti method is the gold standard for treating idiopathic clubfoot (talipes equinovarus). It corrects the deformities in a very specific sequence, remembered by the acronym CAVE: Cavus, Adductus, Varus, and Equinus. The cavus is corrected first by elevating the first ray to align the forefoot with the hindfoot. Then, the adductus and varus are corrected simultaneously by abducting the foot around the head of the talus. Finally, the equinus is addressed; because it is often the most rigid component, it frequently requires a percutaneous Achilles tenotomy as the final step before the last cast is applied.

Question 6506

Topic: 4. Pediatrics

A 4-week-old female infant is brought to the clinic for a routine well-child check. She was born at 39 weeks gestation via breech presentation. Family history is notable for a sister who required a Pavlik harness as an infant. Physical examination reveals symmetric thigh folds and negative Ortolani and Barlow maneuvers. What is the most appropriate next step in management regarding her hip evaluation?

. Reassurance and routine follow-up at 2 months
. Immediate application of a Pavlik harness
. Anteroposterior pelvis radiograph today
. Ultrasound of the hips at 6 weeks of age
. MRI of the pelvis

Correct Answer & Explanation

. Ultrasound of the hips at 6 weeks of age

Explanation

Correct Answer: DThis infant has multiple significant risk factors for Developmental Dysplasia of the Hip (DDH), including female sex, breech presentation, and a positive family history. Even with a normal physical examination, infants with high-risk factors (specifically breech presentation or a positive family history) should undergo screening imaging. Ultrasound is the modality of choice for infants under 4-6 months of age because the femoral head is largely cartilaginous and not well visualized on plain radiographs. The ultrasound is typically performed around 6 weeks of age to avoid false positives from physiologic capsular laxity that is normally present at birth.

Question 6507

Topic: Pediatric Hip

A 13-year-old obese male presents with left knee pain and an obligatory external rotation of the hip during passive flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). During the pathomechanical process of this condition, what is the true displacement of the femoral head (epiphysis) relative to the femoral neck (metaphysis)?

. The epiphysis displaces anteriorly and superiorly.
. The epiphysis displaces anteriorly and inferiorly.
. The metaphysis displaces anteriorly and superiorly, while the epiphysis remains in the acetabulum.
. The metaphysis displaces posteriorly and inferiorly, while the epiphysis remains in the acetabulum.
. The epiphysis displaces laterally and superiorly.

Correct Answer & Explanation

. The metaphysis displaces anteriorly and superiorly, while the epiphysis remains in the acetabulum.

Explanation

Correct Answer: The metaphysis displaces anteriorly and superiorly, while the epiphysis remains in the acetabulum.Although the term "slipped capital femoral epiphysis" implies that the epiphysis is the structure that moves, the biomechanical reality is the opposite. The femoral epiphysis is held securely within the acetabulum by the ligamentum teres. The mechanical failure occurs through the hypertrophic zone of the physis, allowing the femoral neck (metaphysis) to displace anteriorly, superiorly, and externally rotate relative to the fixed epiphysis. This creates the classic radiographic appearance of a posterior and inferior "slip" of the epiphysis on the AP and lateral views.

Question 6508

Topic: 4. Pediatrics

A 2-week-old infant is brought to the clinic for management of idiopathic congenital talipes equinovarus. The treating orthopedic surgeon plans to utilize the Ponseti method of serial casting. According to this method, which of the following represents the correct sequence of deformity correction?

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

Correct Answer & Explanation

. Cavus, Adductus, Varus, Equinus

Explanation

Correct Answer: Cavus, Adductus, Varus, EquinusThe Ponseti method follows a strict sequence of correction summarized by the acronym CAVE: Cavus, Adductus, Varus, and Equinus. The first step is to correct the cavus deformity by supinating the forefoot and elevating the first ray to align it with the hindfoot. Once the cavus is corrected, the adductus and varus are corrected simultaneously by gradually abducting the foot around the lateral aspect of the talar head (which acts as a fulcrum). Finally, the equinus is corrected; this often requires a percutaneous Achilles tenotomy in the final stage of casting to achieve adequate dorsiflexion without causing a rocker-bottom deformity.

Question 6509

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy falls from monkey bars and sustains a widely displaced extension-type supracondylar humerus fracture. On physical examination, he is unable to flex the interphalangeal joint of his thumb and the distal interphalangeal joint of his index finger. Which of the following nerves is most likely injured?

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

Correct Answer & Explanation

. Anterior interosseous nerve

Explanation

Correct Answer: Anterior interosseous nerveThe anterior interosseous nerve (AIN), a pure motor branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. The AIN innervates the flexor pollicis longus (FPL), the flexor digitorum profundus (FDP) to the index and middle fingers, and the pronator quadratus. Injury is clinically assessed by asking the patient to make an "OK" sign; an inability to flex the IP joint of the thumb and the DIP joint of the index finger results in a "pincer" grasp instead, indicating AIN palsy. Ulnar nerve injuries are more commonly associated with flexion-type supracondylar fractures or iatrogenic injury during medial pin placement.

Question 6510

Topic: Pediatric Hip

An infant with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a follow-up visit, the parents report the child is no longer kicking the affected leg. On examination, the knee lacks active extension. Which of the following positioning errors most likely caused this complication?

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

Correct Answer & Explanation

. Excessive hip flexion

Explanation

Femoral nerve palsy is a known complication of the Pavlik harness, typically caused by excessive hip flexion. It presents with absent active knee extension and usually resolves with temporary removal or adjustment of the harness.

Question 6511

Topic: Pediatric Hip

A 4-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. At her 2-week follow-up, her mother reports that the infant is no longer actively kicking her left leg. On examination, there is an absence of active knee extension on the left, but active ankle motion is intact. Which of the following is the most likely cause?

. Avascular necrosis of the femoral head
. Inferior dislocation of the hip
. Femoral nerve palsy due to excessive hip flexion
. Obturator nerve palsy due to excessive hip abduction
. Developmental coxa vara

Correct Answer & Explanation

. Femoral nerve palsy due to excessive hip flexion

Explanation

Hyperflexion of the hip in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to an iatrogenic femoral nerve palsy. The immediate treatment is to adjust the harness to decrease the degree of hip flexion.

Question 6512

Topic: Pediatric Lower Extremity

A 2-week-old male presents with idiopathic clubfoot (talipes equinovarus). The orthopedic surgeon plans to initiate treatment using the Ponseti method. Which of the following is the essential first step when applying the first series of casts?

. Supination of the forefoot to stretch the medial column
. Pronation of the forefoot and extreme plantar flexion
. Elevation of the first ray to correct the cavus deformity
. Abduction of the forefoot to correct the adduction deformity
. External rotation of the calcaneus to correct hindfoot varus

Correct Answer & Explanation

. Elevation of the first ray to correct the cavus deformity

Explanation

The Ponseti method addresses clubfoot deformities in the order of CAVE: Cavus, Adductus, Varus, and Equinus. The first critical maneuver is elevating the first ray to supinate the forefoot in alignment with the hindfoot, thereby correcting the cavus.

Question 6513

Topic: Pediatric Hip

A 4-month-old female is currently being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). At her 2-week follow-up, the parents note that she is no longer kicking her right leg. On physical examination, the right knee lacks active extension, but active ankle and toe movements are completely intact. What is the most likely etiology of this finding, and what is the most appropriate next step in management?

. Transient femoral nerve palsy from excessive hip flexion; adjust the harness to decrease flexion.
. Ischemic necrosis of the femoral head from hyperabduction; immediate surgical release.
. Sciatic nerve palsy from excessive hip extension; permanently discontinue the harness.
. Transient obturator nerve palsy from excessive abduction; adjust the anterior straps.
. Acute compartment syndrome of the thigh; emergent fasciotomy.

Correct Answer & Explanation

. Transient femoral nerve palsy from excessive hip flexion; adjust the harness to decrease flexion.

Explanation

Excessive hip flexion in a Pavlik harness can compress the femoral nerve, causing a transient femoral nerve palsy that presents as a loss of active knee extension. The appropriate management is to adjust the anterior straps to decrease the degree of hip flexion, which typically results in full neurologic recovery.

Question 6514

Topic: 4. Pediatrics

A 3-year-old child with Congenital Femoral Deficiency (CFD) has a stable hip and knee (Paley Type 1) and a predicted LLD at skeletal maturity of 12 cm. Which of the following is the most appropriate long-term reconstructive strategy for achieving limb equalization?

. A single-stage 12 cm femoral lengthening at age 8
. Immediate Syme amputation and prosthetic fitting
. Multiple staged lengthenings combined with contralateral epiphysiodesis
. Standard Van Nes rotationplasty

Correct Answer & Explanation

. Multiple staged lengthenings combined with contralateral epiphysiodesis

Explanation

For a large predicted LLD (> 8 cm) in a patient with stable joints (Type 1 CFD), limb reconstruction is feasible but cannot be safely done in one setting. It requires staged lengthening procedures (e.g., at ages 4, 8, and 14), often augmented by contralateral epiphysiodesis.

Question 6515

Topic: Pediatric Hip

A 10-year-old boy is diagnosed with developmental coxa vara. Biomechanically, how does this deformity alter the forces acting on the proximal femur?

. It decreases the bending moment across the femoral neck and increases the abductor moment arm.
. It increases the bending moment across the femoral neck and decreases the abductor moment arm.
. It increases the bending moment across the femoral neck and increases the abductor moment arm.
. It decreases the bending moment across the femoral neck and decreases the abductor moment arm.
. It decreases both the joint reaction force and the bending moment across the femoral neck.

Correct Answer & Explanation

. It increases the bending moment across the femoral neck and increases the abductor moment arm.

Explanation

Coxa vara decreases the neck-shaft angle, which anatomically lengthens the abductor moment arm, improving abductor efficiency. However, it also creates a longer perpendicular distance from the load vector to the neck, increasing the bending moment and the risk of fracture.

Question 6516

Topic: 4. Pediatrics

A 10-year-old girl suffers a completely displaced Salter-Harris type IV fracture of the distal femur resulting in premature complete physeal closure. Assuming skeletal maturity is reached at age 14, what is the projected final leg length discrepancy?

. 1.5 cm
. 2.4 cm
. 3.6 cm
. 4.5 cm
. 6.0 cm

Correct Answer & Explanation

. 3.6 cm

Explanation

The distal femoral physis grows at approximately 9 mm per year. With 4 years of growth remaining (from age 10 to 14), the projected discrepancy is 4 years x 9 mm/year = 36 mm, or 3.6 cm.

Question 6517

Topic: 4. Pediatrics

A 4-year-old girl has a 2 cm congenital femoral deficiency. Using the Paley multiplier method, what is the expected limb length discrepancy at skeletal maturity? (Assume the multiplier for girls at age 4 is approximately 2.0)

. 2 cm
. 3 cm
. 4 cm
. 5 cm
. 6 cm

Correct Answer & Explanation

. 4 cm

Explanation

The Paley multiplier method predicts limb length discrepancy at maturity by multiplying the current discrepancy by an age- and gender-specific multiplier. For a 4-year-old girl, the multiplier is roughly 2.0, yielding a 4 cm predicted discrepancy.

Question 6518

Topic: Pediatric Lower Extremity

A 12-year-old boy undergoing tibial lengthening with a circular external fixator experiences premature consolidation of the bony regenerate. Which of the following factors most strongly predisposes to this specific complication?

. Latency period of 3 days.
. Distraction rate of 1.5 mm/day.
. Osteotomy using a high-speed burr.
. Fibular hemimelia diagnosis.
. Distraction rate of 0.25 mm/day.

Correct Answer & Explanation

. Distraction rate of 0.25 mm/day.

Explanation

Premature consolidation occurs when the bone heals before the target length is achieved, typically due to a distraction rate that is too slow (e.g., 0.25 mm/day). The standard target rate for distraction osteogenesis is roughly 1.0 mm/day.

Question 6519

Topic: Pediatric Hip

A patient develops coxa vara following a malunited intertrochanteric fracture. How does this structural deformity primarily alter hip biomechanics?

. Increases the abductor moment arm and increases shear stress across the femoral neck.
. Decreases the abductor moment arm and decreases shear stress.
. Decreases the abductor moment arm and increases shear stress.
. Increases the body weight moment arm and decreases shear stress.
. Decreases joint reaction force and decreases shear stress.

Correct Answer & Explanation

. Decreases the abductor moment arm and increases shear stress.

Explanation

Coxa vara decreases the neck-shaft angle, which lengthens the abductor moment arm (improving abductor mechanical advantage) but significantly increases shear forces across the femoral neck, risking nonunion or failure.

Question 6520

Topic: 4. Pediatrics

In a 3-year-old child presenting with asymmetric genu varum, which radiographic parameter is the most reliable predictor that the deformity is infantile Blount disease progressing to require surgical intervention, rather than resolving physiologic bowing?

. Metaphyseal-diaphyseal angle (MDA) > 11 degrees
. Metaphyseal-diaphyseal angle (MDA) > 16 degrees
. Tibiofemoral angle > 15 degrees
. Epiphyseal-metaphyseal angle > 20 degrees
. Mechanical axis deviation (MAD) > 5 mm

Correct Answer & Explanation

. Metaphyseal-diaphyseal angle (MDA) > 16 degrees

Explanation

The metaphyseal-diaphyseal angle (MDA) of Drennan is highly prognostic in early tibia vara. An MDA greater than 16 degrees strongly correlates with the progression of infantile Blount disease requiring surgery.

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