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4. Pediatrics MCQs

Practice Set 196 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 3901

Topic: 4. Pediatrics

A 5-year-old child presents with a history of recurrent long bone fractures after minimal trauma, blue sclerae, and dentinogenesis imperfecta. What is the underlying biochemical defect in this disorder?

. Defect in Type II collagen
. Defect in Type I collagen
. Defect in Type IX collagen
. Defect in Type X collagen
. Defect in Type IV collagen

Correct Answer & Explanation

. Defect in Type I collagen

Explanation

Osteogenesis imperfecta is caused by a quantitative or qualitative defect in Type I collagen, which is the primary collagen type in bone, sclera, and dentin. It typically results from mutations in the COL1A1 or COL1A2 genes.

Question 3902

Topic: Pediatric Hip

A 45-year-old female with Crowe IV developmental dysplasia of the hip (DDH) is undergoing a total hip arthroplasty. The surgeon plans to place the acetabular component at the true anatomic hip center and perform a subtrochanteric shortening osteotomy. Which of the following is the primary rationale for performing the shortening osteotomy in this specific scenario?

. To prevent superior gluteal nerve palsy
. To prevent sciatic nerve palsy
. To increase the offset of the femoral component
. To allow for the use of a larger acetabular component
. To correct excessive femoral retroversion

Correct Answer & Explanation

. To prevent sciatic nerve palsy

Explanation

Correct Answer: To prevent sciatic nerve palsyCrowe IV DDH is characterized by a high hip dislocation with greater than 100% subluxation. The native acetabulum is hypoplastic, and a false acetabulum forms superiorly. When performing a THA in these patients, placing the cup in the true anatomic hip center provides the best biomechanical advantage and longevity. However, bringing the femur down to the true hip center requires significant lengthening of the limb. Lengthening the limb by more than 4 cm poses a high risk of stretch-induced sciatic nerve palsy. To safely place the cup at the true center without overstretching the sciatic nerve, a subtrochanteric shortening osteotomy of the femur is routinely performed.

Question 3903

Topic: Pediatric Hip

A 40-year-old female with severe unilateral developmental dysplasia of the hip (Crowe type IV) undergoes a complex THA requiring significant leg lengthening. Postoperatively, she is unable to actively dorsiflex her foot or extend her great toe, and has numbness over the dorsum of her foot. What is the most common intraoperative mechanism for this specific neurologic complication?

. Direct laceration of the tibial nerve
. Retractor compression of the femoral nerve
. Excessive limb lengthening causing stretch injury to the peroneal division of the sciatic nerve
. Thermal injury from bone cement escaping anteriorly
. Ligation of the internal iliac artery causing ischemic neuropathy

Correct Answer & Explanation

. Excessive limb lengthening causing stretch injury to the peroneal division of the sciatic nerve

Explanation

The peroneal division of the sciatic nerve is particularly vulnerable to stretch injury during THA, especially in cases requiring limb lengthening >4 cm (such as Crowe IV DDH). It is tethered at the fibular head, making it mechanically more susceptible to tension than the tibial division.

Question 3904

Topic: Pediatric Hip
In a patient with Crowe Type III developmental dysplasia of the hip undergoing THA, the surgeon opts to place the acetabular component in the native true acetabulum rather than a high hip center. Which of the following surgical maneuvers is most commonly required to successfully reduce the hip and protect the neurovascular structures?
. Ischial osteotomy
. Subtrochanteric shortening osteotomy
. Hamstring release
. Anterior capsulorrhaphy
. Distal femoral lengthening osteotomy

Correct Answer & Explanation

. Subtrochanteric shortening osteotomy

Explanation

Placing the cup in the true, anatomic acetabulum in severe DDH requires bringing the femur down significantly. A subtrochanteric shortening osteotomy is typically required to allow joint reduction without placing excessive, dangerous tension on the sciatic nerve.

Question 3905

Topic: Pediatric Hip

A 40-year-old female with Crowe IV developmental dysplasia of the hip is undergoing a total hip arthroplasty. The surgeon plans to place the acetabular component at the level of the true anatomic acetabulum. What additional procedural step is most likely required to safely accomplish this reduction?

. Greater trochanteric advancement
. Proximal femoral replacement
. Subtrochanteric shortening osteotomy
. Hamstring tendon lengthening
. Proximal femoral valgus osteotomy

Correct Answer & Explanation

. Subtrochanteric shortening osteotomy

Explanation

In Crowe IV DDH, the femur is highly migrated. Placing the cup in the true, anatomic acetabulum requires significant distal translation of the femur to achieve reduction. A subtrochanteric shortening osteotomy is typically necessary to allow reduction and prevent devastating traction injury to the sciatic nerve.

Question 3906

Topic: Pediatric Hip

A newborn with Down syndrome undergoes a pelvic radiograph for hip screening. Which of the following classic radiographic findings is typically seen in the pelvis of infants with Trisomy 21?

. Increased acetabular index and steep acetabular roofs
. Decreased iliac index with flattened acetabular roofs and flared iliac wings
. Protrusio acetabuli with medial joint space narrowing
. Coxa vara with a fragmented proximal femoral epiphysis
. A shallow acetabulum with a sharply angled sourcil

Correct Answer & Explanation

. Decreased iliac index with flattened acetabular roofs and flared iliac wings

Explanation

The classic pelvic radiographic appearance in Down syndrome includes flared iliac wings and flattened acetabular roofs, resulting in a decreased iliac index. This contrasts with developmental dysplasia of the hip (DDH), which shows an increased acetabular index.

Question 3907

Topic: Pediatric Upper Extremity & Spine

According to the Lenke Classification system for Adolescent Idiopathic Scoliosis, what defines a structural proximal thoracic (PT) curve?

. Cobb angle > 10 degrees on side-bending radiographs
. Cobb angle > 25 degrees on side-bending radiographs or T2-T5 kyphosis > 20 degrees
. Cobb angle > 40 degrees on standing AP radiographs
. Apical vertebral translation > 2 cm
. Nash-Moe rotation of Grade 2 or higher

Correct Answer & Explanation

. Cobb angle > 25 degrees on side-bending radiographs or T2-T5 kyphosis > 20 degrees

Explanation

In the Lenke classification, a minor curve is considered structural if it does not correct to less than 25 degrees on side-bending radiographs, or if there is a regional kyphosis of at least 20 degrees.

Question 3908

Topic: 4. Pediatrics

A 14-year-old male with severe spastic cerebral palsy (GMFCS Level V) is undergoing posterior spinal fusion for a 75-degree neuromuscular scoliosis. He has a pelvic obliquity of 25 degrees. What is the primary functional indication for extending the fusion to the pelvis in this patient?

. To improve independent ambulation
. To prevent superior mesenteric artery syndrome
. To restore stable sitting balance and prevent pressure ulcers
. To improve pulmonary vital capacity
. To prevent hip subluxation

Correct Answer & Explanation

. To restore stable sitting balance and prevent pressure ulcers

Explanation

In non-ambulatory patients with severe neuromuscular scoliosis and significant pelvic obliquity, extending the fusion to the pelvis (e.g., via iliac screws or Galveston technique) is critical to restoring a level pelvis, ensuring stable sitting balance, and preventing ischial pressure ulcers.

Question 3909

Topic: Pediatric Hip

A 10-year-old male with Down syndrome presents with a 3-week history of a limp and poorly localized knee pain. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Compared to an idiopathic SCFE in a neurotypical child, this patient is at an increased risk for which of the following?

. Chondrolysis requiring joint arthrodesis
. Femoral nerve palsy
. Development of a subtrochanteric fracture
. Bilateral involvement
. Malignant transformation

Correct Answer & Explanation

. Bilateral involvement

Explanation

Patients with Down syndrome have a higher incidence of SCFE and a significantly higher rate of bilateral involvement compared to the idiopathic population. They often present younger and require careful evaluation of the contralateral hip.

Question 3910

Topic: Pediatric Upper Extremity & Spine

A 12-year-old female presents with a 32-degree right thoracic curve. She has not reached menarche. Radiographs demonstrate open triradiate cartilages and a Risser stage of 0. What is the most appropriate management?

. Observation with radiographs every 6 months
. Posterior spinal fusion
. Thoracolumbosacral orthosis (TLSO) bracing
. Vertebral body tethering
. Physical therapy focusing on core strengthening

Correct Answer & Explanation

. Thoracolumbosacral orthosis (TLSO) bracing

Explanation

TLSO bracing is indicated for patients with Adolescent Idiopathic Scoliosis (AIS) who have a curve between 25 and 45 degrees and significant remaining growth (Risser 0-2, premenarchal, open triradiate cartilages).

Question 3911

Topic: Pediatric Upper Extremity & Spine

In a patient with Adolescent Idiopathic Scoliosis, which of the following clinical milestones corresponds with the period of greatest risk for rapid curve progression?

. Peak height velocity
. Onset of menarche
. Closure of the triradiate cartilage
. Appearance of the iliac apophysis (Risser 1)
. Fusion of the iliac apophysis to the ilium (Risser 5)

Correct Answer & Explanation

. Peak height velocity

Explanation

The highest risk of curve progression in AIS occurs during the adolescent growth spurt, specifically at the time of peak height velocity. This typically occurs just prior to menarche and Risser 1, while triradiate cartilages are still open.

Question 3912

Topic: Pediatric Hip
A 10-year-old boy with Down syndrome presents with a 2-month history of a limp and poorly localized thigh pain. Exam reveals obligate external rotation of the hip during passive flexion. Which of the following is the most likely diagnosis?
. Legg-Calvé-Perthes disease
. Transient synovitis
. Slipped capital femoral epiphysis (SCFE)
. Developmental dysplasia of the hip (DDH)
. Septic arthritis

Correct Answer & Explanation

. Slipped capital femoral epiphysis (SCFE)

Explanation

Children with Down syndrome are at increased risk for SCFE, frequently due to underlying endocrine issues (e.g., hypothyroidism). Obligate external rotation with hip flexion is the classic physical exam finding for SCFE.

Question 3913

Topic: Pediatric Lower Extremity

Which of the following lower extremity orthopedic conditions is most prevalent in the Down syndrome population due to underlying collagen defects and generalized ligamentous laxity?

. Blount's disease
. Patellofemoral instability
. Tarsal coalition
. Congenital vertical talus
. Clubfoot (talipes equinovarus)

Correct Answer & Explanation

. Patellofemoral instability

Explanation

Generalized ligamentous laxity and hypotonia in Down syndrome frequently lead to patellofemoral instability. Recurrent subluxation or dislocation often requires surgical soft tissue realignment if symptomatic.

Question 3914

Topic: Pediatric Upper Extremity & Spine

A 12-year-old girl with Down syndrome presents with a 45-degree thoracic scoliotic curve.

Compared to adolescent idiopathic scoliosis (AIS), how does the management and prognosis of scoliosis in patients with Down syndrome typically differ?

. They have a lower rate of curve progression
. Bracing is highly effective and usually curative
. Curves are exclusively left-sided
. There is a higher rate of progression and bracing is often poorly tolerated
. Surgical fusion requires anterior-only approaches

Correct Answer & Explanation

. There is a higher rate of progression and bracing is often poorly tolerated

Explanation

Scoliosis in Down syndrome has a higher incidence and progression rate than standard AIS. Furthermore, orthotic bracing is often poorly tolerated and less effective due to the patient's underlying hypotonia and body habitus.

Question 3915

Topic: Pediatric Upper Extremity & Spine

In a 13-year-old female with adolescent idiopathic scoliosis, which of the following combinations of factors represents the highest risk for curve progression?

. Risser stage 0, open triradiate cartilage, and a 30-degree curve
. Risser stage 4, closed triradiate cartilage, and a 20-degree curve
. Risser stage 5, post-menarchal status, and a 40-degree curve
. Risser stage 2, 2 years post-menarche, and a 15-degree curve
. Risser stage 3, closed triradiate cartilage, and a 25-degree curve

Correct Answer & Explanation

. Risser stage 0, open triradiate cartilage, and a 30-degree curve

Explanation

The risk of curve progression in AIS is highest in patients with significant skeletal immaturity (Risser 0, open triradiate cartilage, pre-menarchal) combined with a larger initial curve magnitude (>25 degrees).

Question 3916

Topic: Pediatric Upper Extremity & Spine
In the Lenke classification system for adolescent idiopathic scoliosis, a proximal thoracic curve is considered "structural" and must be included in the fusion construct if the curve bends out to what minimum Cobb angle on side-bending radiographs?
. Greater than 10 degrees
. Greater than or equal to 25 degrees
. Greater than 35 degrees
. Greater than 40 degrees
. Greater than 50 degrees

Correct Answer & Explanation

. Greater than or equal to 25 degrees

Explanation

According to the Lenke classification, minor curves are considered structural if they do not bend out to less than 25 degrees (i.e., remain ≥25 degrees) on side-bending radiographs, or if there is kyphosis ≥ +20 degrees.

Question 3917

Topic: Pediatric Upper Extremity & Spine

A 12-year-old female with Adolescent Idiopathic Scoliosis (AIS) presents with a right thoracic curve. Which of the following combinations of factors indicates the highest risk for curve progression?

. Curve of 15 degrees, Risser 4, post-menarchal
. Curve of 25 degrees, Risser 0, pre-menarchal
. Curve of 20 degrees, Risser 2, post-menarchal
. Curve of 35 degrees, Risser 4, post-menarchal
. Curve of 10 degrees, Risser 1, pre-menarchal

Correct Answer & Explanation

. Curve of 25 degrees, Risser 0, pre-menarchal

Explanation

The risk of progression in AIS is highest during peak growth velocity. A curve of 25 degrees in a pre-menarchal patient with a Risser 0 score carries an approximately 68-100% risk of progression, according to Lonstein and Carlson criteria.

Question 3918

Topic: 4. Pediatrics

A 9-year-old boy presents with a painful, swollen right forearm 3 weeks after a minor fall. Radiographs show a massive, mineralized mass surrounding a healing radial shaft fracture, initially raising suspicion for osteosarcoma. A biopsy confirms hyperplastic callus. On physical examination, he also has severely limited forearm pronation and supination, but his sclerae are white. Which of the following genetic mutations is most likely responsible for this patient's underlying condition?

. COL1A1
. COL1A2
. IFITM5
. SMN1
. FGFR3

Correct Answer & Explanation

. IFITM5

Explanation

Correct Answer: C (IFITM5)This patient's presentation is classic for Osteogenesis Imperfecta (OI) Type V. OI Type V is a distinct, moderate-to-severe form of the disease characterized by the triad of hyperplastic callus formation (which can be massive and mimic osteosarcoma), calcification of the interosseous membrane of the forearm (leading to restricted rotation and radial head dislocation), and an absence of blue sclerae. Unlike the vast majority of OI types (I-IV) which are caused by defects in type I collagen genes (COL1A1andCOL1A2), OI Type V is caused by a specific heterozygous mutation in theIFITM5gene.SMN1mutations cause Spinal Muscular Atrophy, andFGFR3mutations are associated with achondroplasia.

Question 3919

Topic: 4. Pediatrics

A 5-year-old boy with Osteogenesis Imperfecta Type IV undergoes bilateral femoral rodding with Fassier-Duval telescoping intramedullary nails to correct severe anterolateral bowing. Two years postoperatively, radiographs reveal that the right femur has resumed an anterolateral bow, and the male and female components of the rod have not distracted. What is the most likely cause of this specific complication?

. Osteomyelitis of the femoral diaphysis.
. Failure of the rod components to telescope, leading to bone growth around the implant.
. Distal migration of the female component through the knee joint.
. Aseptic loosening of the epiphyseal threads.
. Hyperplastic callus formation blocking the medullary canal.

Correct Answer & Explanation

. Failure of the rod components to telescope, leading to bone growth around the implant.

Explanation

Correct Answer: B (Failure of the rod components to telescope, leading to bone growth around the implant.)Fassier-Duval (FD) rods are telescoping intramedullary devices designed to elongate as the child grows, providing continuous internal splinting for fragile OI bones. The female component is anchored in the proximal epiphysis, and the male component is anchored in the distal epiphysis. A common complication is "jamming" or failure of the rod to telescope. When this occurs, the bone continues to grow longitudinally. Because the rod cannot lengthen, the growing bone is forced to bow around the fixed-length rod (sometimes called the "trombone effect" failure), leading to recurrent deformity and potentially rod migration or cutout.

Question 3920

Topic: 4. Pediatrics

A 7-year-old girl with a history of multiple low-energy fractures is noted by her dentist to have opalescent, amber-colored teeth that exhibit significant enamel attrition and dentin exposure. This dental manifestation is a direct result of a qualitative defect in a protein that is also the primary structural component of which of the following tissues?

. Hyaline cartilage of the articular surface.
. The nucleus pulposus of the intervertebral disc.
. The basal lamina of the epidermis.
. The sclera of the eye and tendons.
. The elastic fibers of the ligamentum flavum.

Correct Answer & Explanation

. The sclera of the eye and tendons.

Explanation

Correct Answer: D (The sclera of the eye and tendons.)The patient has dentinogenesis imperfecta, a common manifestation of Osteogenesis Imperfecta (OI). Dentinogenesis imperfecta is caused by defective dentin formation. Dentin, like bone, is primarily composed of Type I collagen. Therefore, the underlying defect in OI (mutations inCOL1A1orCOL1A2) affects tissues rich in Type I collagen. Type I collagen is the most abundant collagen in the human body and is the primary structural protein in bone, dentin, sclera, tendons, ligaments, and skin. Hyaline cartilage and the nucleus pulposus are primarily composed of Type II collagen. The basal lamina is composed of Type IV collagen.

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