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4. Pediatrics MCQs

Practice Set 36 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 701

Topic: 4. Pediatrics

Homeobox genes are best characterized by which of the following descriptions:

. Homeobox genes regulate fracture healing.
. Homeobox genes are involved in immune system regulation.
. Homeobox genes are a series of genes that regulate limb genesis.
. Homeobox genes regulate spinal development.
. Homeobox genes regulate vascular invasion of the physis.

Correct Answer & Explanation

. Homeobox genes are a series of genes that regulate limb genesis.

Explanation

Homeobox genes code for transcription factors involved in regulation of limb genesis in the embryonic period. Homeobox genes have a highly conserved 60-nucleotide sequence.

Question 702

Topic: 4. Pediatrics

Which of the following regions of the physis has the highest degree of proteoglycan aggregation in the matrix:

. Reserve zone
. Proliferative zone
. Hypertrophic zone
. Zone of degeneration
. Metaphysis

Correct Answer & Explanation

. Reserve zone

Explanation

The proteoglycan aggregation is greatest in the reserve zone and in the epiphysis. Proteoglycan concentration progressively decreases in the direction of the metaphysis. This phenomenon also enables calcification to occur.

Question 703

Topic: Pediatric Hip

Which of the following categories of slipped capital femoral epiphysis (SC FE) is associated with the highest rate of bilaterality:

. Idiopathic SC FE
. Renal failure
. Radiation therapy
. Hypothyroidism
. Growth hormone deficiency

Correct Answer & Explanation

. Renal failure

Explanation

Renal failure is associated with the highest risk (90%) of bilaterality. By contrast, idiopathic SC FE has a 20% risk of bilaterality initially and a further 10% to 20% risk until maturity.

Question 704

Topic: 4. Pediatrics

The dose of acetaminophen for a child should be no more than:

. 1.5 mg/kg
. 5 mg/kg
. 10-15 mg/kg
. 20-30 mg/kg
. 50 mg/kg

Correct Answer & Explanation

. 10-15 mg/kg

Explanation

The dose of acetaminophen should be 10-15 mg/kg. The maximum daily dose should be no more than 75 mg/kg. Larger doses of acetaminophen pose a risk of hepatotoxicity over a long period of time.

Question 705

Topic: 4. Pediatrics

Opioids must be used with caution in infants younger than 3 months of age because of which of the following properties:

. Increased clearance
. Increased protein binding
. Increased hepatic activity
. Decreased clearance and protein binding
. Decreased body surface area to mass

Correct Answer & Explanation

. Decreased clearance and protein binding

Explanation

Opioids must be used with caution in infants younger than 3 months of age because of decreased clearance and decreased protein binding. This results in greater bioavailability.

Question 706

Topic: Pediatric Hip

Which of the following factors should prompt a workup for an underlying disorder in a patient with slipped capital femoral epiphysis:

. A bilateral slip
. Weight over the 50th percentile for age
. Weight under the 50th percentile for age
. A positive family history
. A slip of grade II or higher

Correct Answer & Explanation

. Weight under the 50th percentile for age

Explanation

A positive age-weight test is defined as a patient who is under the 50th percentile of weight for age or older than 16 years of age at presentation with slipped capital femoral epiphysis. These patients should have a workup for underlying renal or endocrine disease. A positive family history is found in 5% to 10% of patients with slipped capital femoral epiphysis.

Question 707

Topic: Pediatric Hip
Which of the following categories of slipped capital femoral epiphysis (SCFE) is associated with the highest risk of a grade III slip?
. Renal failure
. Idiopathic SCFE
. Radiation therapy
. Hypothyroidism
. Growth hormone deficiency

Correct Answer & Explanation

. Renal failure

Explanation

A grade III slip refers to more than 50% displacement of the epiphysis. Renal failure is associated with the highest risk (43%) of progressing to a grade III slip. Fortunately, these slips are usually stable.

Question 708

Topic: Pediatric Upper Extremity & Spine

The timing of maximal progression of idiopathic scoliosis is most closely correlated with:

. C hronological age
. Skeletal age
. Peak height velocity
. Risser sign
. Tanner stage

Correct Answer & Explanation

. Peak height velocity

Explanation

The cause of scoliosis or its progression is still not known. However, the timing of the progression is most closely correlated with the peak velocity of growth. The other factors are more weakly correlated: a chronological or skeletal age of 10 to 12 years, Risser sign of 0, or Tanner sign of 0 to 1.

Question 709

Topic: Pediatric Upper Extremity & Spine

Which of the following events typically occurs first in adolescent girls:

. Risser sign turning to 1
. Peak height velocity
. Menarche
. Skeletal maturity
. Tanner sign of 3

Correct Answer & Explanation

. Peak height velocity

Explanation

Typically, the peak height velocity is the first of these events to occur in adolescent girls. Skeletal maturity is the last event to occur.

Question 710

Topic: 4. Pediatrics

In evaluating infants for Blount disease, which diagnostic parameter allows correct classification of the greatest number of children:

. Langenskjold rating
. Tibiofemoral angle
. Tibial metaphyseal-diaphyseal (M-D) angle
. Femoral M-D angle divided by tibial M-D angle
. Femoral intercondylar distance divided by height

Correct Answer & Explanation

. Femoral M-D angle divided by tibial M-D angle

Explanation

The tibial metaphyseal-diaphyseal (M-D) angle, no matter what threshold is set, has a significant number of false-positives or false-negatives. Using the ratio of femoral to tibial M-D angle improves diagnostic accuracy significantly. The Langenskjold rating, tibiofemoral angle, and intercondylar distances, although conceptually important, have low diagnostic accuracy for an individual patient.

Question 711

Topic: 4. Pediatrics

According to the Ponseti method for the treatment of congenital idiopathic clubfoot, which of the following deformities must be corrected first?

. Equinus
. Hindfoot varus
. Forefoot adduction
. Midfoot cavus
. Tibial internal torsion

Correct Answer & Explanation

. Midfoot cavus

Explanation

The first step in the Ponseti technique is correcting the midfoot cavus, which is achieved by elevating the first ray to align the forefoot with the hindfoot. This provides a solid foundation for the subsequent correction of adduction, varus, and finally equinus (the CAVE sequence).

Question 712

Topic: Pediatric Hip

An 8-year-old female presents with bilateral slipped capital femoral epiphysis (SCFE). Given her age and presentation, which of the following laboratory investigations is most appropriate?

. Hemoglobin A1c
. Thyroid-stimulating hormone (TSH)
. Serum parathyroid hormone (PTH)
. 25-hydroxyvitamin D
. Fasting blood glucose

Correct Answer & Explanation

. Thyroid-stimulating hormone (TSH)

Explanation

Patients presenting with SCFE outside the typical age range (under 10 or over 16) or with bilateral involvement should be screened for underlying endocrine disorders. Hypothyroidism is the most common associated endocrinopathy, making TSH the best initial screening test.

Question 713

Topic: Pediatric Upper Extremity & Spine
According to the modified Gartland classification for pediatric supracondylar humerus fractures, which of the following best describes a Type III injury?
. Completely displaced fracture with no cortical contact
. Undisplaced fracture with a positive posterior fat pad sign
. Displaced fracture with an intact posterior cortical hinge
. Fracture with metaphyseal comminution but intact medial hinge
. Flexion-type injury with an intact anterior hinge

Correct Answer & Explanation

. Completely displaced fracture with no cortical contact

Explanation

In the Gartland classification, a Type I fracture is nondisplaced, and a Type II fracture is displaced but has an intact posterior hinge. A Type III fracture is completely displaced with no cortical contact, presenting a higher risk for neurovascular compromise.

Question 714

Topic: Pediatric Hip

Which of the following is an absolute indication for prophylactic in situ pinning of the contralateral asymptomatic hip in a patient with a unilateral slipped capital femoral epiphysis (SCFE)?

. Age greater than 14 years in males
. Presence of an endocrine disorder such as hypothyroidism
. Triradiate cartilage closure
. Male gender
. African American descent

Correct Answer & Explanation

. Presence of an endocrine disorder such as hypothyroidism

Explanation

Prophylactic contralateral pinning is highly recommended in patients with endocrine or metabolic disorders, as they have a significantly higher rate of bilateral involvement. Other relative indications include previous radiation therapy and young age (<10 years).

Question 715

Topic: Pediatric Hip
In the lateral pillar classification of Legg-Calvรฉ-Perthes disease described by Herring, which portion of the femoral head is evaluated on the anteroposterior radiograph to determine the prognosis?
. The central third of the epiphysis
. The medial third of the epiphysis
. The lateral third of the epiphysis
. The anterior third of the epiphysis
. The posterior third of the epiphysis

Correct Answer & Explanation

. The lateral third of the epiphysis

Explanation

The Herring lateral pillar classification evaluates the height of the lateral third of the capital femoral epiphysis on an AP radiograph during the fragmentation stage. Maintenance of lateral pillar height is the most significant prognostic indicator for long-term hip congruency.

Question 716

Topic: Pediatric Hip

A 12-year-old obese male presents with acute-on-chronic left hip pain and an inability to bear weight. Radiographs confirm an unstable slipped capital femoral epiphysis (SCFE). Which of the following represents the most significant risk associated with urgent, aggressive closed reduction of this injury prior to pinning?

. Chondrolysis
. Avascular necrosis (AVN) of the femoral head
. Femoroacetabular impingement
. Leg length discrepancy
. Premature physeal closure

Correct Answer & Explanation

. Avascular necrosis (AVN) of the femoral head

Explanation

Forceful or aggressive closed reduction of an unstable SCFE significantly increases the risk of avascular necrosis (AVN) of the femoral head. Gentle, incidental reduction during patient positioning is acceptable, but intentional forceful manipulation is contraindicated.

Question 717

Topic: 4. Pediatrics

A 12-year-old boy comes to your office 2 weeks after a distal radius physeal fracture, which has been splinted in the emergency department. The epiphysis is displaced dorsally by 50%, and the articular surface has a dorsal tilt of 17ยฐ. You recommend:

. C losed manipulation with sedation
. C losed manipulation under anesthesia with relaxation
. Open reduction, internal fixation
. C ast application and observation
. Percutaneous pin fixation in current position

Correct Answer & Explanation

. C ast application and observation

Explanation

Distal radial physeal fractures are common injuries. Reduction should be done gently and not repeated multiple times. Fractures presenting late like this one are difficult to manipulate atraumatically, but have good remodeling potential. Therefore, a cast should be applied to limit any further displacement, but no manipulation or operation is recommended.

Question 718

Topic: 4. Pediatrics

Which of the following lowers the chance of a good result from stretching of muscular torticollis in infants:

. Palpable mass in the sternocleidomastoid muscle
. Age at presentation less than 1 month
. Rotation to neutral
. Absence of plagiocephaly
. High birth weight

Correct Answer & Explanation

. Palpable mass in the sternocleidomastoid muscle

Explanation

Stretching produces good results in more than 90% of infants. Presence of a palpable mass in the sternomastoid predicts a lower success rate than absence of such a mass. The other factors are either positive or neutral.

Question 719

Topic: Pediatric Upper Extremity & Spine

Which of the following statements is true of the King classification of idiopathic scoliosis:

. It takes into account sagittal alignment of curves.
. It defines structural and nonstructural curves.
. It classifies all possible curve patterns.
. It has a lower interobserver reliability than the Lenke system.
. It has more curve types than the Lenke system.

Correct Answer & Explanation

. It takes into account sagittal alignment of curves.

Explanation

The Lenke system is more comprehensive than the King system, for the latter considers the entire range or thoracolumbar and lumbar curve possibilities, as well as the sagittal plane. The Lenke system also appears to have a higher interobserver reliability.

Question 720

Topic: Pediatric Upper Extremity & Spine

A 9-year-old boy injures his elbow in a fall from a 12-foot height. Radiographs reveal a posterior dislocation of the elbow with a fracture of the medial epicondyle which is displaced. The ossification center is 5 mm in diameter. You recommend:

. Open reduction internal fixation with a smooth pin
. Open reduction internal fixation with a small screw
. Open reduction and fixation with a suture
. Open reduction with excision of the fragment and suture of the medial collateral ligament
. C losed reduction of the dislocation and application of a splint

Correct Answer & Explanation

. C losed reduction of the dislocation and application of a splint

Explanation

A recent long-term study has shown that open reduction of displaced medial epicondyle fractures does not yield superior results to closed treatment. This applies even when the elbow is initially dislocated. Excision of the epicondyle with suture of the ligament yields the highest incidence of late problems, such as flexion contractures and degenerative changes.

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