Practice Set 6 of 212
This practice set contains high-yield board review questions covering key concepts in Biology, Genetics & Bone Healing. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.
A 5-year-old boy presents with multiple fractures, blue sclerae, and hearing loss. A defect in which of the following is the primary cause of his condition?
. Type I collagen
When evaluating a child for suspected non-accidental trauma, which of the following laboratory profiles best differentiates severe nutritional rickets from osteogenesis imperfecta (OI)?
. Abnormal type I collagen synthesis
A 14-month-old child presents with severe bowing of the legs. Radiographs show widened physes and "cupping and fraying" of the metaphyses. Laboratory evaluation reveals hypophosphatemia, normal serum calcium, and normal parathyroid hormone levels. What is the most likely diagnosis?
. X-linked hypophosphatemic rickets
Following severe elbow trauma or an open surgical contracture release, what is the most effective and widely accepted prophylactic regimen to prevent heterotopic ossification (HO)?
. Indomethacin and/or low-dose single-fraction radiation
Which of the following conditions is inherited in an X-linked dominant fashion:
. Familial hypophosphatemic rickets
What is the primary mechanism of action of intravenous bisphosphonates (e.g., pamidronate) used in treating children with osteogenesis imperfecta?
. Inhibiting osteoclast-mediated bone resorption
A patient with delayed closure of the fontanelles, multiple supernumerary teeth, and the ability to appose their shoulders anteriorly in the midline most likely has a mutation affecting which gene?
. CBFA1 (RUNX2)
. Type II collagen
A patient with Cleidocranial Dysplasia is undergoing an orthopedic evaluation. Which of the following is the underlying genetic and pathophysiologic mechanism for this condition?
. Mutation in the RUNX2 (CBFA1) gene affecting membranous bone formation
Which of the following skeletal dysplasias is inherited in an X-linked dominant fashion and presents with lower extremity bowing, widened physes, and hypophosphatemia that does not respond to standard doses of Vitamin D?
. Familial hypophosphatemic rickets
A 3-year-old with frequent fractures, blue sclerae, and dentinogenesis imperfecta is started on intravenous pamidronate. What is the primary mechanism of action of this medication in treating her condition?
. Inhibits osteoclast-mediated bone resorption
A patient with Spondyloepiphyseal Dysplasia congenita (SEDc) is likely to have a defect involving which of the following molecules?
. Type II collagen
A 4-year-old child presents with severe varus bowing of the lower extremities, short stature, and a waddling gait. Laboratory studies reveal normal serum calcium, markedly low serum phosphate, and elevated alkaline phosphatase. Which of the following is the hallmark molecular pathogenesis?
. Excessive FGF23 production
A 9-year-old girl is noted to have excessive mobility of her shoulders, allowing them to touch in the midline. Pelvic radiographs would most likely reveal which of the following abnormalities?
. Wide pubic symphysis
. Inhibition of farnesyl pyrophosphate synthase in osteoclasts
Which of the following combined clinical features is pathognomonic for Cleidocranial Dysplasia?
. Delayed closure of cranial sutures and absent clavicles
A 20-month-old toddler is brought in because of bowed legs. You note moderate-to-severe genu varum and thigh-foot angles of 35° inward. The child is otherwise healthy, and height and weight are near the 50th percentiles. Radiographs demonstrate tibial metaphyseal-diaphyseal angles of 8° on the right and 9° on the left. Femoral metaphyseal-diaphyseal angles are the same. You recommend:
. Observation, with return only if not improving
A 3-year-old girl presents with progressive bilateral bowlegs. Radiographs reveal varus deformity localized to the proximal tibia with a metaphyseal-diaphyseal angle (Drennan's angle) of 18 degrees. What does this finding indicate?
. High likelihood of progression to infantile Blount disease
During anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone autograft, incorporation of the bony ends into the tunnels occurs primarily via which of the following processes?
. Creeping substitution
Which of the following molecules binds directly to RANK on the surface of osteoclast precursors to stimulate their differentiation into mature osteoclasts?
. RANKL