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4. Pediatrics MCQs

Practice Set 319 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 6361

Topic: 4. Pediatrics

A 4-year-old child with Neurofibromatosis Type 1 presents with anterolateral bowing of the tibia and an established pseudarthrosis. Previous cast immobilizations have failed. What surgical approach utilizes deformity correction principles with the highest rate of achieving union and preventing refracture in this condition?

. In situ bone grafting with a non-vascularized fibular strut.
. Resection of the pseudarthrosis, intramedullary rodding, and Ilizarov external fixation with bone grafting.
. Amputation at the level of the pseudarthrosis.
. Vascularized free fibula transfer alone without resection of the hamartomatous tissue.
. Medial opening wedge osteotomy proximal to the pseudarthrosis.

Correct Answer & Explanation

. Resection of the pseudarthrosis, intramedullary rodding, and Ilizarov external fixation with bone grafting.

Explanation

Congenital pseudarthrosis of the tibia (CPT) requires aggressive resection of the hamartomatous periosteum/bone. The gold standard involves intramedullary fixation (e.g., Fassier-Duval rod) combined with compression via an Ilizarov external fixator or robust bone grafting (often with BMP).

Question 6362

Topic: 4. Pediatrics

A newborn is evaluated for a congenitally short lower extremity. Radiographs reveal absence of the fibula, anteromedial bowing of the tibia, a severe equinovalgus foot, and the absence of the lateral 3 rays of the foot (Fibular Hemimelia, Paley Type 4). The projected leg length discrepancy at skeletal maturity is 22 cm. What is the most widely recommended functional management strategy for this specific clinical picture?

. Immediate application of an Ilizarov frame for tibial lengthening.
. Early Syme amputation and prosthetic fitting.
. Contralateral distal femoral and proximal tibial epiphysiodesis at age 5.
. Talectomy and tibiocalcaneal arthrodesis.
. Guided growth of the distal tibia using a medial tension-band plate.

Correct Answer & Explanation

. Early Syme amputation and prosthetic fitting.

Explanation

In severe fibular hemimelia with a non-functional foot (missing rays, severe rigid equinovalgus) and a massive predicted limb length discrepancy (>20 cm), multiple lengthening procedures carry high complication rates and poor foot function. Early Syme amputation provides an excellent end-bearing stump for highly functional prosthetic wear.

Question 6363

Topic: 4. Pediatrics

The Hueter-Volkmann principle is the biomechanical foundation for using a tension-band plate (eight-plate) for guided growth in pediatric angular deformities. Which of the following statements best describes this law?

. Bone remodels in response to the mechanical stresses placed upon it.
. Increased compression across a physis accelerates longitudinal growth.
. Increased compression across a physis retards longitudinal growth, while tension accelerates it.
. Physeal distraction leads to premature closure of the growth plate.
. Tension on the periosteum stimulates intramembranous ossification.

Correct Answer & Explanation

. Increased compression across a physis retards longitudinal growth, while tension accelerates it.

Explanation

The Hueter-Volkmann law dictates that increased mechanical compression across an active growth plate inhibits growth, whereas distraction or decreased compression stimulates it. A tension-band plate placed on the convex side of a deformity tethers that side (compression), allowing the concave side to continue growing and correct the angle.

Question 6364

Topic: 4. Pediatrics

An 8-year-old boy presents with severe, symptomatic idiopathic genu valgum. His bone age is equivalent to his chronological age. Which of the following is the most appropriate, minimally invasive surgical intervention to gradually correct this deformity?

. Distal femoral medial closing-wedge osteotomy
. Proximal tibial lateral opening-wedge osteotomy
. Medial distal femoral hemiepiphysiodesis using a tension-band plate
. Lateral distal femoral hemiepiphysiodesis using a tension-band plate
. Complete distal femoral epiphysiodesis

Correct Answer & Explanation

. Medial distal femoral hemiepiphysiodesis using a tension-band plate

Explanation

For a growing child with symptomatic genu valgum, guided growth via medial distal femoral hemiepiphysiodesis tethers the medial physis while allowing lateral growth. This gradually corrects the valgus alignment over time.

Question 6365

Topic: 4. Pediatrics

In distraction osteogenesis using the Ilizarov method, what is the generally accepted optimal rate and rhythm of distraction for a standard diaphyseal corticotomy?

. 1.0 mm once daily
. 0.5 mm twice daily
. 0.25 mm four times daily
. 1.5 mm divided into six increments
. 0.25 mm twice daily

Correct Answer & Explanation

. 0.25 mm four times daily

Explanation

Ilizarov's fundamental research demonstrated that continuous or high-frequency distraction optimizes bone regenerate quality. The standard clinical protocol is 1 mm per day divided into four 0.25 mm increments.

Question 6366

Topic: 4. Pediatrics
A 3-year-old boy is diagnosed with Langenskiold stage III infantile Blount's disease. Non-operative management with knee-ankle-foot orthoses (KAFOs) has failed. What is the most appropriate definitive management?
. Medial proximal tibial hemiepiphysiodesis
. Lateral proximal tibial hemiepiphysiodesis
. Observation until age 8, followed by guided growth
. Proximal tibial and fibular valgus-producing osteotomy
. Physeal bar excision with fat interposition

Correct Answer & Explanation

. Proximal tibial and fibular valgus-producing osteotomy

Explanation

For advanced infantile Blount's disease (Langenskiold stage III or higher) that has failed bracing, surgical realignment via a proximal tibial and fibular osteotomy is indicated to restore normal mechanical alignment and unload the medial physis.

Question 6367

Topic: 4. Pediatrics

The use of an eight-Plate (tension-band plate) for hemiepiphysiodesis corrects angular limb deformities by tethering one side of the physis. Which physiological principle provides the theoretical foundation for this technique?

. Wolff's Law
. Heuter-Volkmann principle
. Starling's principle
. Delpech's principle
. Hilton's Law

Correct Answer & Explanation

. Heuter-Volkmann principle

Explanation

The Hueter-Volkmann principle states that increased mechanical compression across a physis slows its growth, while reduced compression accelerates it. Tension-band plating relies on this principle to selectively slow growth on the tethered side.

Question 6368

Topic: 4. Pediatrics

A 10-year-old boy presents with severe bilateral genu valgum. You perform guided growth using tension band plates. Which of the following is an expected radiographic finding indicating the hardware is actively altering growth?

. The screws become perfectly parallel over time.
. The screws diverge significantly from each other over time.
. The screws converge toward each other over time.
. The plate bows away from the metaphyseal bone.
. The metaphyseal screw migrates across the physis.

Correct Answer & Explanation

. The screws diverge significantly from each other over time.

Explanation

As the physis grows on the side opposite the tension band plate, the tethered side acts as a hinge. This causes the screws, which are initially parallel, to diverge as angular correction is achieved.

Question 6369

Topic: 4. Pediatrics

A 7-year-old child with spastic diplegic cerebral palsy presents with a crouch gait. Kinematic analysis reveals increased knee flexion during stance. What is the most common iatrogenic cause of this gait pattern in this patient population?

. Over-lengthening of the medial hamstrings
. Under-lengthening of the psoas tendon
. Over-lengthening of the Achilles tendon
. Rectus femoris transfer
. Botulinum toxin injection into the gastrocnemius

Correct Answer & Explanation

. Over-lengthening of the Achilles tendon

Explanation

Crouch gait in cerebral palsy is heavily dependent on an incompetent plantarflexor-knee extension couple. Over-lengthening the Achilles tendon causes calcaneal stance and exacerbates crouch by removing the plantarflexor restraint on anterior tibial advancement.

Question 6370

Topic: 4. Pediatrics

A surgeon is using the multiplier method (Paley) to predict leg length discrepancy at maturity for a congenital femoral deficiency. The multiplier for the child's specific age is 1.5, and the current discrepancy is 3 cm. Assuming constant inhibition, what is the predicted discrepancy at skeletal maturity?

. 2.0 cm
. 3.0 cm
. 4.5 cm
. 6.0 cm
. 7.5 cm

Correct Answer & Explanation

. 4.5 cm

Explanation

Using the Paley multiplier method for congenital deformities, the predicted discrepancy at maturity is calculated by multiplying the current discrepancy by the age-and-sex-specific multiplier. Thus, 3 cm x 1.5 = 4.5 cm.

Question 6371

Topic: 4. Pediatrics

Distraction osteogenesis is planned for a 15-year-old with a 5 cm post-traumatic tibial shortening. According to Ilizarov principles, what is the optimal rate and rhythm of distraction?

. 0.25 mm once per day
. 0.25 mm four times per day
. 1.0 mm once per day
. 1.5 mm twice per day
. 2.0 mm once per day

Correct Answer & Explanation

. 0.25 mm four times per day

Explanation

The optimal rate of distraction for bone regenerate is approximately 1.0 mm per day. Dividing this into frequent, small increments (e.g., 0.25 mm four times a day) provides the optimal rhythm to encourage ossification while minimizing soft tissue complications.

Question 6372

Topic: 4. Pediatrics

A 5-year-old with achondroplasia is being evaluated for bilateral genu varum. Guided growth with tension band plates is considered. What unique anatomical consideration in achondroplasia affects the success of this procedure?

. The physeal growth potential is inherently limited, making guided growth slower and less predictable.
. The proximal tibial physis is typically fused by age 5 in these patients.
. Tension band plates are absolutely contraindicated due to a high risk of catastrophic implant failure.
. They have rapid rebound overgrowth, requiring implant removal within 3 months.
. The fibula is usually shorter than the tibia, protecting the lateral aspect from tension.

Correct Answer & Explanation

. The physeal growth potential is inherently limited, making guided growth slower and less predictable.

Explanation

Patients with skeletal dysplasias like achondroplasia have intrinsically abnormal and slower physeal growth. While guided growth can still be utilized, it takes significantly longer to achieve correction compared to idiopathic deformities.

Question 6373

Topic: Pediatric Hip

A 13-year-old obese male presents with a 3-week history of left groin pain and a limp. On examination, as the left hip is passively flexed, it obligatorily externally rotates. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Relative to the capital femoral epiphysis, in which direction is the femoral neck (metaphysis) typically displaced in this condition?

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

Correct Answer & Explanation

. Anterior and superior

Explanation

Correct Answer: Anterior and superiorIn a Slipped Capital Femoral Epiphysis (SCFE), the capital femoral epiphysis remains anatomically seated within the acetabulum while the femoral neck (metaphysis) displaces. Because the epiphysis effectively 'slips' posterior and inferior relative to the neck, the biomechanical reality is that the femoral neck displaces anterior and superior relative to the epiphysis. This creates the classic external rotation deformity seen clinically.

Question 6374

Topic: Pediatric Upper Extremity & Spine

A 6-year-old boy sustains an extension-type supracondylar humerus fracture with posterolateral displacement of the distal fragment. Based on the typical displacement pattern, which of the following physical exam findings is most likely to be present if the most commonly associated nerve injury occurred?

. Inability to flex the distal interphalangeal joint of the index finger
. Inability to extend the metacarpophalangeal joints
. Numbness over the dorsal web space of the hand
. Inability to cross the index and middle fingers
. Weakness in wrist extension with radial deviation

Correct Answer & Explanation

. Inability to flex the distal interphalangeal joint of the index finger

Explanation

Correct Answer: Inability to flex the distal interphalangeal joint of the index fingerIn extension-type supracondylar humerus fractures, the direction of distal fragment displacement dictates the nerve most at risk. Posterolateral displacement of the distal fragment causes the proximal fragment to displace anteromedially, putting the median nerve (specifically the anterior interosseous nerve, AIN) at greatest risk. The AIN innervates the flexor pollicis longus (FPL) and the flexor digitorum profundus (FDP) to the index and middle fingers. An AIN palsy presents as an inability to flex the IP joint of the thumb and the DIP joint of the index finger (making an 'A-OK' sign is impossible). Posteromedial displacement puts the radial nerve at risk.

Question 6375

Topic: 4. Pediatrics

A 10-year-old sustains a Salter-Harris Type II fracture of the distal radius. Through which specific histologic zone of the physis does the fracture line primarily propagate before exiting through the metaphysis?

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

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

Correct Answer: Zone of hypertrophyPhyseal fractures, including Salter-Harris types, typically propagate through the zone of hypertrophy. This zone is biomechanically the weakest area of the growth plate because the chondrocytes are enlarged (hypertrophic) and the extracellular matrix is relatively sparse. The fracture line usually spares the reserve and proliferative zones, which is why growth potential is often maintained in Type I and II fractures, provided the blood supply is intact.

Question 6376

Topic: Pediatric Hip

A 3-month-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up visit, the parents report that the infant has stopped kicking her leg on the treated side. On examination, there is an absence of active knee extension. This complication is most likely due to which of the following positioning errors?

. Excessive hip abduction
. Inadequate hip abduction
. Excessive hip flexion
. Inadequate hip flexion
. Excessive hip internal rotation

Correct Answer & Explanation

. Excessive hip flexion

Explanation

Correct Answer: Excessive hip flexionThe Pavlik harness is used to treat DDH by maintaining the hips in flexion and abduction. However, improper application can lead to severe complications. Excessive hip flexion (typically >120 degrees) can compress the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy, which presents as an inability to actively extend the knee. Conversely, excessive hip abduction places the medial circumflex femoral artery at risk, potentially causing avascular necrosis (AVN) of the femoral head.

Question 6377

Topic: 4. Pediatrics

Slipped Capital Femoral Epiphysis (SCFE) typically presents with posterior and inferior displacement of the epiphysis relative to the femoral neck. Through which specific histological zone of the physis does this failure primarily occur?

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

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

Correct Answer: CIn SCFE, the mechanical failure and subsequent slippage occur primarily through the zone of hypertrophy of the physis. This zone is structurally the weakest because it lacks the abundant collagen matrix found in the proliferative zone and has not yet been reinforced by the calcification seen in the zone of provisional calcification.

Question 6378

Topic: Pediatric Hip

A 3-month-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up visit, the physician notes that the infant is no longer actively extending her knee on the treated side. Which of the following positioning errors in the harness is the most likely cause of this complication?

. Excessive hip abduction
. Inadequate hip abduction
. Excessive hip flexion
. Inadequate hip flexion
. Excessive knee flexion

Correct Answer & Explanation

. Excessive hip flexion

Explanation

Correct Answer: CThe Pavlik harness maintains the hip in flexion and abduction. Excessive hip flexion (typically greater than 120 degrees) can cause compression of the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy. This presents clinically as an inability to actively extend the knee due to quadriceps weakness. Conversely, excessive abduction is associated with avascular necrosis (AVN) of the femoral head.

Question 6379

Topic: 4. Pediatrics

A 12-year-old obese male presents with a painful limp and an obligate external rotation of the hip during flexion. Radiographs confirm a slipped capital femoral epiphysis (SCFE). The mechanical failure of the physis in this condition predominantly occurs through which of the following histologic zones?

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

Correct Answer & Explanation

. Zone of hypertrophy

Explanation

Correct Answer: CSlipped capital femoral epiphysis (SCFE) involves the displacement of the proximal femoral epiphysis relative to the metaphysis. The biomechanical failure and slippage occur almost exclusively through the zone of hypertrophy of the physis. This zone is structurally the weakest because it lacks the abundant collagenous matrix found in the proliferative zone and the calcified matrix found in the zone of provisional calcification.

Question 6380

Topic: Pediatric Hip

A 3-month-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up visit, the parents report that the infant has stopped kicking her right leg. On examination, there is an absence of active knee extension on the right side. This complication is most likely due to which of the following improper harness adjustments?

. Excessive abduction of the hip
. Inadequate abduction of the hip
. Excessive flexion of the hip
. Inadequate flexion of the hip
. Excessive internal rotation of the hip

Correct Answer & Explanation

. Excessive flexion of the hip

Explanation

Correct Answer: CThe Pavlik harness is the standard initial treatment for DDH in infants under 6 months. Proper positioning is crucial. Excessive flexion of the hip (caused by anterior straps being too tight) can compress the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy. This manifests clinically as decreased kicking and absent active knee extension. Conversely, excessive abduction (posterior straps too tight) increases the risk of avascular necrosis of the femoral head.

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