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4. Pediatrics MCQs

Practice Set 333 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 6641

Topic: 4. Pediatrics
A 2-year-old child presents with bilateral genu varum. Radiographs reveal a metaphyseal-diaphyseal angle of 18 degrees on the right and 10 degrees on the left. What is the most appropriate management for the right leg?
. Observation alone
. Guided growth via tension-band plating
. Knee-ankle-foot orthosis (KAFO)
. Proximal tibial closing wedge osteotomy
. Epiphysiodesis

Correct Answer & Explanation

. Knee-ankle-foot orthosis (KAFO)

Explanation

A metaphyseal-diaphyseal angle greater than 16 degrees strongly suggests infantile Blount's disease. For children under 3 years of age (Langenskiöld stage I or II), bracing with a KAFO is the standard initial treatment.

Question 6642

Topic: 4. Pediatrics

A 10-year-old child with spastic diplegic cerebral palsy undergoes an isolated percutaneous Achilles tendon lengthening. Postoperatively, the patient rapidly develops a progressive crouch gait. What biomechanical consequence explains this outcome?

. Loss of the plantarflexion-knee extension couple
. Overactivity of the rectus femoris
. Iatrogenic hamstring contracture
. Weakness of the hip flexors
. Excessive anterior pelvic tilt

Correct Answer & Explanation

. Loss of the plantarflexion-knee extension couple

Explanation

The gastrocnemius-soleus complex normally stabilizes the tibia during stance, promoting knee extension (the plantarflexion-knee extension couple). Over-lengthening the Achilles tendon removes this stabilizing force, leading to tibial advancement, knee flexion, and crouch gait.

Question 6643

Topic: 4. Pediatrics

An 11-year-old boy presents with progressive genu valgum and a lateral mechanical axis deviation. He has open physes with approximately 3 years of growth remaining. If guided growth is chosen, where should a tension-band plate be positioned?

. Medial distal femoral physis
. Lateral distal femoral physis
. Medial proximal tibial physis
. Anterior distal femoral physis
. Posterior proximal tibial physis

Correct Answer & Explanation

. Medial distal femoral physis

Explanation

To correct a valgus deformity, growth must be slowed on the medial side while allowing the lateral side to continue growing. Placing a tension-band plate across the medial distal femoral (or proximal tibial) physis achieves this via the Hueter-Volkmann principle.

Question 6644

Topic: Pediatric Lower Extremity

A 7-year-old girl presents with frequent tripping and an intoeing gait. Examination shows hip internal rotation of 85 degrees and external rotation of 10 degrees bilaterally. What is the most likely diagnosis and its natural history?

. Increased femoral anteversion; typically resolves spontaneously by age 10
. Decreased femoral anteversion; typically progresses requiring surgery
. Increased tibial torsion; requires a derotational osteotomy
. Metatarsus adductus; typically resolves with casting
. Femoral retroversion; typically resolves spontaneously by age 10

Correct Answer & Explanation

. Increased femoral anteversion; typically resolves spontaneously by age 10

Explanation

This presentation (excessive internal rotation, 'W-sitting') is classic for increased femoral anteversion. In the vast majority of cases, it resolves spontaneously by ages 8 to 10 without surgical intervention.

Question 6645

Topic: 4. Pediatrics



A 15-year-old requires correction of a multiplanar post-traumatic tibial deformity using a hexapod circular fixator. The mathematical model governing this device's simultaneous correction of all planes is based on which of the following kinematic principles?

. Ilizarov rule of thirds
. Euler buckling theorem
. Stewart platform mechanics
. Hooke's Law of elasticity
. Pascal's principle

Correct Answer & Explanation

. Stewart platform mechanics

Explanation

Hexapod circular fixators, like the Taylor Spatial Frame, utilize Stewart platform mechanics. This allows for 6 degrees of freedom, enabling simultaneous correction of length, angulation, translation, and rotation via computer software.

Question 6646

Topic: 4. Pediatrics

In the pathogenesis of infantile Blount disease, a vicious cycle occurs where varus bowing increases compressive forces across the medial proximal tibial physis, which in turn further suppresses medial growth. Which biomechanical principle best describes this phenomenon?

. Wolff's law
. Heuter-Volkmann principle
. Pauwels' principle
. Pascal's law
. Tension-stress effect

Correct Answer & Explanation

. Heuter-Volkmann principle

Explanation

The Hueter-Volkmann principle states that increased compressive forces across a physis inhibit its growth, while decreased forces or tension stimulate growth. This explains the progressive medial physeal failure in Blount disease.

Question 6647

Topic: Pediatric Lower Extremity

A 5-year-old girl is evaluated for an in-toeing gait. Examination reveals internal hip rotation of 85 degrees, external hip rotation of 10 degrees, and a thigh-foot angle of +10 degrees. What is the primary anatomical cause of her rotational profile?

. Metatarsus adductus
. Internal tibial torsion
. Increased femoral anteversion
. Femoral retroversion
. External tibial torsion

Correct Answer & Explanation

. Increased femoral anteversion

Explanation

The patient exhibits classically increased femoral anteversion, characterized by excessive internal hip rotation (>70 degrees) and restricted external rotation. The positive thigh-foot angle indicates normal to slightly external tibial torsion, ruling out internal tibial torsion.

Question 6648

Topic: 4. Pediatrics

A 14-year-old girl presents with severe bilateral leg pain, weakness, and a waddling gait. Radiographs display profound cortical thickening of the bilateral femoral and tibial diaphyses, sparing the epiphyses.

What is the underlying genetic mutation associated with this condition?

. COMP
. FGFR3
. TGFB1
. COL1A1
. RUNX2

Correct Answer & Explanation

. TGFB1

Explanation

The clinical and radiographic presentation is classic for Progressive Diaphyseal Dysplasia (Camurati-Engelmann disease). This condition is inherited in an autosomal dominant pattern due to mutations in the TGFB1 gene.

Question 6649

Topic: 4. Pediatrics

A 10-year-old with Morquio syndrome requires surgical intervention for lower extremity deformity.

What is the most common lower extremity angular deformity seen in these patients?

. Genu varum
. Genu valgum
. Tibial bowing (anterolateral)
. Coxa vara
. Equinovarus

Correct Answer & Explanation

. Genu valgum

Explanation

Severe genu valgum (knock-knees) is the most common lower extremity deformity in Morquio syndrome (MPS IV), often resulting from ligamentous laxity and metaphyseal dysplasia, frequently requiring surgical correction via guided growth or osteotomy.

Question 6650

Topic: 4. Pediatrics

A 10-year-old girl presents with a waddling gait, severe leg pain, and proximal muscle weakness. Radiographs demonstrate bilateral, symmetrical cortical thickening of the femoral and tibial diaphyses, sparing the epiphyses.

Which genetic mutation is associated with this condition?

. COL1A1
. FGFR3
. COMP
. TGFB1
. GNAS

Correct Answer & Explanation

. TGFB1

Explanation

The presentation is classic for Progressive Diaphyseal Dysplasia (Camurati-Engelmann disease), characterized by symmetrical diaphyseal sclerosis and muscle weakness. It is an autosomal dominant condition caused by mutations in the TGFB1 gene.

Question 6651

Topic: 4. Pediatrics

A 10-year-old child presents with a waddling gait, severe leg muscle weakness, and chronic deep thigh pain. Radiographs demonstrate bilateral symmetrical cortical thickening of the diaphyseal regions of the femur and tibia, sparing the epiphyses. What is the most likely diagnosis?

. Osteopetrosis
. Progressive diaphyseal dysplasia (Camurati-Engelmann disease)
. Melorheostosis
. Infantile cortical hyperostosis (Caffey disease)
. Osteopoikilosis

Correct Answer & Explanation

. Progressive diaphyseal dysplasia (Camurati-Engelmann disease)

Explanation

Progressive diaphyseal dysplasia (Camurati-Engelmann disease) presents with bilateral, symmetrical diaphyseal cortical thickening, leg pain, and proximal muscle weakness resulting in a waddling gait.

Question 6652

Topic: 4. Pediatrics

Which genetic mutation is responsible for Progressive diaphyseal dysplasia (Camurati-Engelmann disease)?

. COL1A1
. FGFR3
. TGFB1
. COMP
. SOX9

Correct Answer & Explanation

. TGFB1

Explanation

Camurati-Engelmann disease is an autosomal dominant condition caused by mutations in the TGFB1 (Transforming Growth Factor Beta 1) gene, which leads to increased bone formation.

Question 6653

Topic: 4. Pediatrics

A 4-year-old boy presents with severe thoracolumbar kyphosis, coarse facial features, and corneal clouding. Radiographs of the spine demonstrate anterior inferior vertebral beaking. Which of the following metabolic defects is the underlying cause of this patient's condition?

. Deficiency of iduronate-2-sulfatase
. Deficiency of alpha-L-iduronidase
. Deficiency of N-acetylgalactosamine-6-sulfatase
. Deficiency of beta-glucuronidase
. Mutation in the FGFR3 gene

Correct Answer & Explanation

. Deficiency of alpha-L-iduronidase

Explanation

Anterior inferior vertebral beaking, coarse facial features, and corneal clouding are classic for Hurler syndrome (MPS I), an autosomal recessive disorder caused by a deficiency of alpha-L-iduronidase. Hunter syndrome (MPS II) presents similarly but is X-linked and lacks corneal clouding, while Morquio syndrome (MPS IV) features anterior central (middle) vertebral beaking.

Question 6654

Topic: 4. Pediatrics

Which of the following joint abnormalities is a classic orthopedic manifestation in patients with Morquio syndrome (MPS IV) as a result of primary epiphyseal dysplasia and ligamentous laxity?

. Severe congenital talipes equinovarus
. Progressive coxa vara
. Severe genu valgum
. Slipped capital femoral epiphysis
. Bilateral radioulnar synostosis

Correct Answer & Explanation

. Severe genu valgum

Explanation

Morquio syndrome (MPS IV) is highly associated with ligamentous laxity and severe genu valgum (knock-knees), which often requires surgical correction (such as guided growth or osteotomies) to maintain ambulation.

Question 6655

Topic: 4. Pediatrics

A 10-year-old boy presents with severe bilateral leg pain, fatigability, and a waddling gait. Radiographs show symmetrical cortical thickening of the femoral and tibial diaphyses, sparing the epiphyses.

What is the underlying genetic mutation responsible for this progressive diaphyseal dysplasia (Camurati-Engelmann disease)?

. COL1A1
. FGFR3
. COMP
. TGFB1
. RUNX2

Correct Answer & Explanation

. TGFB1

Explanation

Camurati-Engelmann disease (Progressive Diaphyseal Dysplasia) is an autosomal dominant condition caused by mutations in the TGFB1 gene. This leads to increased transforming growth factor-beta 1 activity, stimulating excessive bone formation at the diaphyses.

Question 6656

Topic: 4. Pediatrics

An 8-year-old child presents with normal intelligence but severe skeletal dysplasia, macrocephaly, coarse facial features, and dense corneal clouding. Laboratory tests show elevated urinary dermatan sulfate only. A diagnosis of Maroteaux-Lamy syndrome (MPS VI) is made. Which enzyme is deficient in this condition?

. Arylsulfatase B
. Alpha-L-iduronidase
. Iduronate-2-sulfatase
. Galactose-6-sulfatase
. Beta-galactosidase

Correct Answer & Explanation

. Arylsulfatase B

Explanation

Maroteaux-Lamy syndrome (MPS VI) is caused by a deficiency in arylsulfatase B. It is characterized by severe skeletal manifestations (dysostosis multiplex) and corneal clouding, but notably preserves normal intellectual function.

Question 6657

Topic: 4. Pediatrics

A 12-year-old girl presents with deep leg pain, easy fatigability, and a waddling gait. Radiographs reveal bilateral, symmetric cortical thickening and sclerosis of the femoral and tibial diaphyses, sparing the epiphyses.

A mutation in which of the following genes is primarily responsible for this condition?

. COL1A1
. FGFR3
. TGFB1
. COMP
. SOX9

Correct Answer & Explanation

. TGFB1

Explanation

The clinical and radiographic presentation is diagnostic of progressive diaphyseal dysplasia (Camurati-Engelmann disease). This autosomal dominant condition is caused by a mutation in the TGFB1 gene, leading to increased bone formation.

Question 6658

Topic: 4. Pediatrics

A 4-year-old girl is evaluated for a congenital femoral deficiency. Her projected limb length discrepancy at maturity is calculated to be 6 cm using the Paley multiplier method. Which parameter forms the foundational constant in the multiplier method algorithm?

. The annual growth velocity of the physis
. The ratio of current bone length to mature bone length
. The skeletal age over chronological age
. The proportion of total height to lower limb length
. The rate of physeal closure

Correct Answer & Explanation

. The ratio of current bone length to mature bone length

Explanation

The multiplier method is based on the epidemiological observation that the ratio of a given bone's length at any specific chronological age to its final length at skeletal maturity is a constant. This allows for simple and accurate prediction of limb length discrepancy.

Question 6659

Topic: 4. Pediatrics

According to the classic Ilizarov principles of distraction osteogenesis for limb lengthening, which of the following represents the optimal daily rate and rhythm to promote robust regenerate formation while avoiding premature consolidation?

. 1.0 mm per day divided into 4 increments of 0.25 mm
. 0.5 mm per day divided into 2 increments of 0.25 mm
. 1.5 mm per day divided into 3 increments of 0.5 mm
. 2.0 mm per day divided into 4 increments of 0.5 mm
. 1.0 mm per day in a single 1.0 mm increment

Correct Answer & Explanation

. 1.0 mm per day divided into 4 increments of 0.25 mm

Explanation

The optimal rate of distraction is 1.0 mm per day, typically performed in four equal increments of 0.25 mm (rhythm). Slower rates risk premature consolidation, while faster rates or less frequent larger increments lead to poor regenerate formation and soft tissue complications.

Question 6660

Topic: 4. Pediatrics

When performing distraction osteogenesis using the Ilizarov method, what is the most widely accepted optimal rate and rhythm of distraction to promote high-quality regenerate bone while preventing premature consolidation?

. 0.5 mm per day, divided into 2 increments
. 1.0 mm per day, divided into 4 increments
. 1.5 mm per day, divided into 6 increments
. 2.0 mm per day, divided into 2 increments

Correct Answer & Explanation

. 1.0 mm per day, divided into 4 increments

Explanation

The classic Ilizarov principle recommends a distraction rate of 1.0 mm per day, optimally divided into four 0.25 mm increments. This rhythm maximizes osteogenesis and angiogenesis while minimizing soft tissue complications.

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