4. Pediatrics MCQs

A surgeon plans to correct a severe articular ankle valgus deformity using a focal dome osteotomy of the distal tibia rather than an opening or closing wedge osteotomy. What is the primary mechanical advantage of the dome osteotomy in this scenario?

During the second stage of an Ilizarov hip reconstruction for a chronically dislocated hip, a distal femoral osteotomy is performed in addition to the proximal pelvic support osteotomy. What is the precise mechanical purpose of this distal osteotomy?

A 12-year-old with developmental coxa vara has a neck-shaft angle of 90 degrees and significant relative trochanteric overgrowth resulting in a Trendelenburg gait. A valgus-producing intertrochanteric osteotomy is planned. According to Paley's principles, where should the osteotomy hinge be positioned to optimally correct the varus, relatively distalize the greater trochanter, and maximize neck length?

A 14-year-old patient with severe coxa vara is undergoing a proximal femoral osteotomy. Radiographic analysis reveals the Center of Rotation of Angulation (CORA) is located in the center of the femoral head. If the osteotomy is performed at the intertrochanteric level and the hinge is placed precisely at the CORA, what is the anticipated geometric outcome according to Paley's principles?

A 12-year-old boy presents with multiple painless bony bumps around his knees and ankles. Radiographs show multiple osteochondromas pointing away from the joint. Genetic testing reveals a mutation in the EXT1 gene. What is the primary molecular consequence of this mutation?

Recent molecular studies have identified specific somatic mosaic mutations as the primary driver in the pathogenesis of both Ollier disease and Maffucci syndrome. These mutations most commonly occur in which of the following genes?

A 35-year-old male presents with chronic, aching pain and progressive stiffness in his right lower extremity. Radiographs reveal dense, irregular, eccentric hyperostosis along the cortex of the femur and tibia, resembling 'dripping candle wax'. Which of the following genes is most commonly mutated in this condition?

A 2-year-old child with a known FGFR3 mutation presents with newly developed sleep apnea, generalized hyperreflexia, and clonus. Based on the most likely diagnosis, what is the most appropriate initial diagnostic step?

A 4-year-old child presents with a waddling gait and short-limb dwarfism. The child had a normal length at birth and normal facial features. Radiographs reveal small, irregular epiphyses and widened, irregular metaphyses. A mutation in which gene is most likely responsible?

A 3-year-old with recurrent minor trauma fractures and distinct blue sclerae is diagnosed with Osteogenesis Imperfecta Type I. Analysis shows a quantitative decrease in structurally normal type I collagen. What is the most common underlying genetic mechanism for this specific subtype?

A 5-year-old child presents with bowlegs, short stature, and a waddling gait. Radiographs show flaring and irregularity of the metaphyses at the knees and hips, but the epiphyses are entirely normal. Genetic testing reveals a mutation strictly affecting the hypertrophic zone of the physis. Which gene is mutated?

A 4-year-old child presents with short-trunk dwarfism, a barrel chest, and a waddling gait. Ophthalmic examination reveals severe myopia and retinal detachment. Pelvic radiographs show delayed ossification of the femoral heads and severe coxa vara. This phenotype is most strongly associated with a mutation in which of the following genes?

A 10-year-old boy presents with bilateral knee and hip pain after exercise. His height is at the 15th percentile. Radiographs demonstrate small, irregular epiphyses in the hips and knees, and a lateral radiograph of the knee reveals a characteristic 'double-layered' patella. What is the most likely mutated gene responsible for this condition?

A 7-year-old boy with a known RUNX2 gene mutation presents for orthopedic evaluation. He has hypermobile shoulders that can be brought together in the midline, delayed closure of cranial sutures, and normal stature. Which of the following lower extremity anomalies is most characteristic of this syndrome and may require surgical intervention?

A 3-year-old child presents with bowed legs and a waddling gait. Radiographs show widened growth plates, flaring of the metaphyses, and coxa vara, mimicking rickets. However, serum calcium, phosphorus, and alkaline phosphatase are entirely normal. The spine is uninvolved. A mutation in which gene is the most likely cause?

An 8-year-old child with severe short-trunk disproportionate dwarfism is evaluated. Radiographs exhibit 'dumbbell-shaped' femora with broad metaphyses, flattened epiphyses, and marked platyspondyly with anterior wedging. Additionally, the patient has a cleft palate and profound hearing loss. What is the underlying genetic defect?

A 14-year-old boy with a history of recurrent fractures since childhood sustains a minor forearm fracture. Four weeks later, radiographs demonstrate massive, hyperplastic callus formation at the fracture site and extensive calcification of the interosseous membrane. Which gene mutation is responsible for this distinct phenotypic variant of osteogenesis imperfecta (Type V)?

A 5-year-old girl is evaluated for a waddling gait and disproportionate short stature with shortening primarily of the limbs. Radiographs show delayed, fragmented epiphyseal ossification. Unlike a patient with classic achondroplasia, which of the following physical examination findings is expected in this patient?