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4. Pediatrics MCQs

Practice Set 230 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 4581

Topic: Pediatric Hip

A 55-year-old male is scheduled for a total hip arthroplasty. He has a history of severe developmental dysplasia of the hip (Crowe Type IV). You plan a subtrochanteric shortening osteotomy. Which of the following is the most critical advantage of this technique compared to a greater trochanteric slide osteotomy?

. Preserves the abductor mechanism insertion
. Avoids the need for custom femoral components
. Allows correction of excessive femoral anteversion
. Prevents sciatic nerve palsy by shortening the femur
. Eliminates the risk of nonunion

Correct Answer & Explanation

. Preserves the abductor mechanism insertion

Explanation

In Crowe IV DDH, bringing the femoral head distally into the true acetabulum stretches the sciatic nerve. A subtrochanteric shortening osteotomy critically reduces this tension, significantly lowering the risk of sciatic nerve palsy.

Question 4582

Topic: Pediatric Hip

An infant is being treated for Developmental Dysplasia of the Hip (DDH) using a Pavlik harness. During a follow-up visit, the infant is noted to have decreased active knee extension on the treated side. This complication is most commonly associated with which of the following positioning errors?

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

Correct Answer & Explanation

. Excessive flexion of the hips

Explanation

In a Pavlik harness, excessive flexion of the hips (>120 degrees) can compress the femoral nerve against the inguinal ligament, leading to a transient femoral nerve palsy (manifesting as decreased active quadriceps extension). Conversely, excessive hyperabduction is associated with avascular necrosis (AVN) of the femoral head.

Question 4583

Topic: Pediatric Hip

A 9-year-old boy presents with an insidious onset of a limp, thigh pain, and obligatory external rotation of the hip with flexion. He is noted to be significantly shorter than his peers, plotting below the 5th percentile for height. Radiographs confirm a bilateral Slipped Capital Femoral Epiphysis (SCFE). Given his age and presentation, which of the following underlying systemic conditions must be highly suspected?

. Hypothyroidism
. Hyperthyroidism
. Hyperparathyroidism
. Addison's disease
. Type 1 Diabetes mellitus

Correct Answer & Explanation

. Hypothyroidism

Explanation

SCFE typically occurs during the adolescent growth spurt (males 12-16 years, females 10-14 years). When it presents in a patient outside this typical age range (e.g., <10 years), with bilateral involvement, or in a patient with short stature, an underlying endocrine abnormality should be strongly suspected, with hypothyroidism being the most common association.

Question 4584

Topic: Pediatric Hip

Slipped capital femoral epiphysis (SCFE) typically occurs in overweight adolescents undergoing a rapid growth spurt. Which of the following patient profiles should prompt an immediate and thorough laboratory workup for an underlying endocrine or renal abnormality?

. A 13-year-old male with a BMI in the 95th percentile
. A 12-year-old female presenting with acute-on-chronic bilateral knee pain
. A 9-year-old male with a BMI in the 30th percentile
. A 14-year-old male with a history of a prior contralateral SCFE
. A 15-year-old African American male with left hip pain

Correct Answer & Explanation

. A 13-year-old male with a BMI in the 95th percentile

Explanation

Atypical SCFE presentations that warrant an endocrine workup (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency) include age of onset less than 10 years or greater than 16 years, and weight less than the 50th percentile.

Question 4585

Topic: 4. Pediatrics
Osteogenesis imperfecta (OI) is a genetic disorder of Type I collagen biosynthesis. According to the Sillence classification, which type of OI is characterized as the perinatal lethal form, often presenting with multiple intrauterine fractures and an under-mineralized calvarium?
. Type I
. Type II
. Type III
. Type IV
. Type V

Correct Answer & Explanation

. Type II

Explanation

Sillence Type II Osteogenesis Imperfecta is the most severe and is typically lethal in the perinatal period due to severe pulmonary hypoplasia and massive skeletal fragility. Type I is the mildest form.

Question 4586

Topic: Pediatric Lower Extremity

According to the Ponseti method for treating idiopathic clubfoot, which deformity must be addressed first during the serial casting phase?

. Equinus
. Varus
. Adductus
. Cavus
. Internal tibial torsion

Correct Answer & Explanation

. Equinus

Explanation

The components of clubfoot are corrected in the specific order of CAVE: Cavus, Adductus, Varus, then Equinus. The cavus is corrected first by supinating the forefoot to align it with the hindfoot.

Question 4587

Topic: Pediatric Hip

A 12-year-old obese male presents with a left Slipped Capital Femoral Epiphysis (SCFE). Which of the following factors is considered the strongest indication for prophylactic in situ pinning of the asymptomatic contralateral hip?

. Male gender
. Age greater than 14 years
. Concurrent underlying endocrine disorder
. Body mass index > 95th percentile
. Family history of SCFE

Correct Answer & Explanation

. Male gender

Explanation

Patients with an underlying endocrine disorder (e.g., hypothyroidism, growth hormone deficiency, renal osteodystrophy) have a significantly higher risk of bilateral SCFE. Prophylactic pinning of the contralateral side is strongly recommended in these individuals.

Question 4588

Topic: 4. Pediatrics
A 4-year-old child presents with multiple recurrent fractures, blue sclerae, and early hearing loss. This condition is most commonly caused by a genetic mutation directly affecting the synthesis of which of the following structural components?
. Type I collagen
. Type II collagen
. Type III collagen
. Fibrillin-1
. Fibroblast growth factor receptor 3 (FGFR3)

Correct Answer & Explanation

. Type I collagen

Explanation

Osteogenesis imperfecta is most commonly an autosomal dominant disorder caused by mutations in the COL1A1 or COL1A2 genes. These mutations result in quantitative or qualitative defects in Type I collagen, the major structural protein of bone.

Question 4589

Topic: Pediatric Hip

In a 12-year-old male presenting with a unilateral slipped capital femoral epiphysis (SCFE), which of the following factors is the strongest indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

. Male sex
. BMI greater than 35
. Presentation with isolated knee pain instead of hip pain
. Presence of an endocrine disorder such as hypothyroidism
. Symptomatic slip angle greater than 50 degrees

Correct Answer & Explanation

. Male sex

Explanation

Endocrine disorders (e.g., hypothyroidism, renal osteodystrophy) significantly increase the risk of bilateral SCFE. Prophylactic pinning of the contralateral hip is highly recommended in these patients to prevent a secondary slip.

Question 4590

Topic: Pediatric Hip

In a 7-year-old boy diagnosed with Legg-Calve-Perthes disease, which of the following radiographic findings is considered a head-at-risk sign indicating a poorer prognosis and potential need for surgical containment?

. Medial subluxation of the femoral head
. Gage sign (a V-shaped radiolucency in the lateral epiphysis)
. Ossification of the femoral head occurring before age 8
. Narrowing of the teardrop distance
. Presence of a concurrent slipped capital femoral epiphysis

Correct Answer & Explanation

. Medial subluxation of the femoral head

Explanation

Catterall's head-at-risk signs include the Gage sign, lateral calcification, lateral subluxation of the femoral head, and a horizontal physis. These signs indicate a loss of containment and a higher risk for permanent femoral head deformation.

Question 4591

Topic: 4. Pediatrics



In the developing child prior to physeal closure, the primary blood supply to the capital femoral epiphysis is derived from the lateral epiphyseal artery. This vessel is a terminal branch of which artery?

. Inferior gluteal artery
. Obturator artery
. Medial femoral circumflex artery
. Lateral femoral circumflex artery
. First perforating artery

Correct Answer & Explanation

. Inferior gluteal artery

Explanation

The medial femoral circumflex artery (MFCA) gives rise to the lateral epiphyseal vessels. These vessels provide the predominant blood supply to the capital femoral epiphysis in children, as the physis blocks the metaphyseal vessels.

Question 4592

Topic: 4. Pediatrics
Osteogenesis imperfecta (OI) type I is the most common form of the disease. It is primarily characterized by which of the following genetic defects?
. A quantitative defect resulting in decreased production of normal Type I collagen
. A qualitative defect resulting in the production of structurally abnormal Type I collagen
. A mutation in the FGFR3 gene
. A deficiency in lysyl hydroxylase
. A mutation in the RUNX2 gene

Correct Answer & Explanation

. A quantitative defect resulting in decreased production of normal Type I collagen

Explanation

OI Type I is generally caused by null mutations in one of the COL1A1 alleles, resulting in a quantitative defect where only about half the normal amount of Type I collagen is produced, but the collagen that is produced is structurally normal. Types II, III, and IV OI typically involve missense mutations (often glycine substitutions) resulting in a qualitative defect (structurally abnormal collagen).

Question 4593

Topic: 4. Pediatrics

In pediatric orthopedics, guided growth procedures for angular deformities exploit a fundamental physiological principle regarding the physis. The principle that increasing mechanical compression across a growth plate slows longitudinal growth, whereas increasing tension accelerates it, is known as:

. Wolff's law
. Heuter-Volkmann law
. Hilton's law
. Perren's strain theory
. Galileo's principle

Correct Answer & Explanation

. Wolff's law

Explanation

The Heuter-Volkmann law describes the effect of mechanical forces on physeal growth: compression inhibits growth, and tension stimulates it. This principle forms the basis for interventions like tension-band plating (hemiepiphysiodesis).

Question 4594

Topic: 4. Pediatrics

A 4-year-old child presents with frequent extremity fractures from minimal trauma, clinically visible blue sclerae, and dentinogenesis imperfecta. Radiographs reveal generalized osteopenia and multiple healed long bone fractures. This condition is most commonly caused by a genetic mutation affecting the synthesis of which structural protein?

. Type I collagen
. Type II collagen
. Fibrillin-1
. Fibroblast growth factor receptor 3 (FGFR3)
. Cartilage Oligomeric Matrix Protein (COMP)

Correct Answer & Explanation

. Type I collagen

Explanation

The patient's clinical presentation is classic for Osteogenesis Imperfecta (OI). The majority of OI cases are caused by autosomal dominant mutations in the COL1A1 or COL1A2 genes, which lead to defective qualitative or quantitative production of Type I collagen.

Question 4595

Topic: 4. Pediatrics
Osteogenesis imperfecta (OI) type I is the most common and mildest form of the disease. It is primarily characterized by a genetic defect resulting in which of the following structural abnormalities?
. Abnormal fibroblast growth factor receptor 3 (FGFR3)
. Defective mineralization of the osteoid matrix
. Decreased quantitative production of normal type I collagen
. Production of structurally abnormal (mutated) type II collagen
. Defective cartilage template formation during endochondral ossification

Correct Answer & Explanation

. Decreased quantitative production of normal type I collagen

Explanation

Type I osteogenesis imperfecta is typically a quantitative defect caused by a null allele, leading to a decreased amount of structurally normal type I collagen. Types II, III, and IV involve qualitative defects where abnormal collagen is produced.

Question 4596

Topic: 4. Pediatrics

Achondroplasia is the most common form of short-limbed dwarfism. The underlying genetic mutation involves a gain-of-function in the fibroblast growth factor receptor 3 (FGFR3). Which specific zone of the physis is primarily inhibited by this mutation?

. Resting zone
. Proliferative zone
. Hypertrophic zone
. Zone of provisional calcification
. Primary spongiosa

Correct Answer & Explanation

. Resting zone

Explanation

Achondroplasia results from an activating mutation in FGFR3, which abnormally inhibits chondrocyte proliferation. This primarily affects the proliferative zone of the physis, leading to diminished longitudinal bone growth.

Question 4597

Topic: 4. Pediatrics

Osteogenesis imperfecta is a genetic disorder of connective tissue characterized by bone fragility and recurrent fractures. The majority of cases involve a mutation in the COL1A1 or COL1A2 genes. This mutation most commonly results in the substitution of which critical amino acid in the collagen triple helix?

. Proline
. Lysine
. Hydroxyproline
. Glycine
. Glutamine

Correct Answer & Explanation

. Proline

Explanation

Collagen's triple helix structure requires the repeating sequence Gly-X-Y, where glycine must occupy every third position due to its small size. In Osteogenesis Imperfecta, a bulky amino acid frequently substitutes for glycine, disrupting the triple helix.

Question 4598

Topic: 4. Pediatrics
A 78-year-old woman who lives in a nursing home sustains an injury to her left forearm. Radiograph is shown in Figure A. It is determined that the injury occurred as the result of elder abuse. All of the following are considered risk factors for elder abuse EXCEPT?
. Dementia
. Disruptive behavior by the victim
. Gender
. Poverty
. Poor physical health of the victim

Correct Answer & Explanation

. Gender

Explanation

Physicians have an ethical and legal duty to protect patients from suspected abuse, and most states mandate reporting by health-care personnel so it is imperative physicians know the statutes in their state. Gender has not been identified as an independent risk factor. Risk factors include substance abuse or mental illness on the part of the abuser, dependence of the abuser on the victim, shared living arrangements, external factors causing stress, social isolation, a history of violence, increased age of victim, race, poverty, functional disability and cognitive impairment. A strong association between reported child abuse and reported elder abuse within a regional population has been reported. The review by Chen et al states the prevalence of elder abuse is 32 cases per 1,000 persons and is increasing with the growing elderly population. The review by Lachs states that risk factors for abuse include dementia, poor physical and emotional health, disruptive or aggressive behavior, social dysfunction and prior violence or abusive acts by the victim toward the abuser.

Question 4599

Topic: 4. Pediatrics

A 32-year-old female presents with multiple asymmetrical, expanding cartilaginous tumors in the phalanges of her hands, accompanied by soft tissue hemangiomas exhibiting phleboliths on radiographs. Which gene mutation is most likely responsible for her underlying syndrome?

. EXT1
. GNAS
. IDH1
. PTH1R
. FGFR3

Correct Answer & Explanation

. EXT1

Explanation

The patient has Maffucci syndrome, characterized by multiple enchondromatosis and soft tissue hemangiomas. Both Ollier disease and Maffucci syndrome are heavily associated with somatic mosaic mutations in the IDH1 or IDH2 genes.

Question 4600

Topic: Pediatric Hip

A 4-week-old female is placed in a Pavlik harness for developmental dysplasia of the hip. At her one-week follow-up, she is noted to have absent active knee extension on the affected side. Which of the following is the most appropriate next step in management?

. Adjust the harness to increase abduction
. Discontinue the harness temporarily or significantly decrease anterior strap tension
. Proceed to closed reduction and spica casting
. Increase anterior strap tension to secure reduction
. Transition immediately to a rigid hip abduction orthosis

Correct Answer & Explanation

. Adjust the harness to increase abduction

Explanation

Absent active knee extension indicates a femoral nerve palsy, a known complication of the Pavlik harness occurring in about 2% of cases. It is caused by excessive hyperflexion, which compresses the femoral nerve against the inguinal ligament. The most appropriate immediate management is to discontinue the harness temporarily or decrease the tension on the anterior flexion straps to allow the nerve to recover. Recovery typically occurs within a few days to a week.

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