Biology, Genetics & Bone Healing MCQs

The compressive strength and stiffness of normal articular cartilage are primarily provided by the interaction between interstitial fluid and which of the following extracellular matrix components?

A 10-year-old boy sustains a transverse subtrochanteric fracture. Radiographs reveal generalized, symmetric increased bone density with an absent medullary canal (Erlenmeyer flask deformity). The underlying pathophysiology of this condition is a defect in which of the following?

Recombinant human bone morphogenetic protein-2 (rhBMP-2) enhances bone healing by inducing the differentiation of mesenchymal stem cells into osteoblasts. This osteoinductive effect is mediated by activating which of the following intracellular signaling pathways?

During the process of secondary fracture healing, the initial cartilaginous soft callus is gradually replaced by a hard woven bone callus. Which of the following cell types is primarily responsible for the production of the initial woven bone via endochondral ossification?

Intermittent, low-dose administration of parathyroid hormone (PTH) analogs, such as teriparatide, is utilized for severe osteoporosis. While continuous elevated PTH causes net bone resorption, intermittent administration primarily stimulates bone formation by directly activating receptors on which cell type?

During primary cortical bone healing via cutting cones, which of the following cell types is located at the very leading edge of the remodeling unit?

A 14-year-old patient presents with multiple fragility fractures, hepatosplenomegaly, and progressive cranial nerve palsies. Radiographs show diffusely dense, 'marble-like' bones with absent medullary canals. The primary cellular defect in this condition involves the impairment of which of the following?

A 65-year-old female with severe, T-score -3.5 osteoporosis is started on daily subcutaneous teriparatide therapy. This medication increases bone mineral density primarily through which of the following mechanisms?

Denosumab has emerged as an effective medical therapy for unresectable or recurrent giant cell tumor of bone (GCTB). What is the exact molecular mechanism of action of this drug in the treatment of GCTB?

Primary (direct) bone healing relies on Haversian remodeling across the fracture site without the formation of an intermediate cartilaginous or fibrous callus. Which of the following mechanical conditions is an absolute prerequisite for primary bone healing to occur?

A 5-year-old boy presents with progressive bowing of his legs, a waddling gait, and short stature. Laboratory evaluation reveals normal serum calcium, critically low serum phosphate, normal parathyroid hormone (PTH), and markedly elevated alkaline phosphatase. Genetic testing identifies a mutation in the PHEX gene. What is the primary pathophysiologic mechanism driving this patient's metabolic bone disease?

Which of the following molecules is secreted by osteoblasts to act as a decoy receptor, preventing RANKL from binding to its target and thereby decreasing osteoclastogenesis?

A 45-year-old woman with a history of Roux-en-Y gastric bypass 10 years ago presents with diffuse bone pain and bilateral groin aching. Radiographs reveal bilateral Looser zones in the femoral necks. Which of the following laboratory profiles is most consistent with her underlying metabolic bone disease?

According to Perren's strain theory of bone healing, what is the maximum tissue strain environment under which primary lamellar bone formation can occur across a fracture gap?

A 32-year-old female presents with an expansile, eccentric lytic lesion in the distal femur epimetaphysis. Biopsy confirms a giant cell tumor of bone. If medical therapy is initiated prior to surgery, the agent used most likely targets which of the following?

Bone morphogenetic proteins (BMPs) play a crucial role in bone healing and osteoinduction. Upon binding to their transmembrane serine/threonine kinase receptors, which intracellular signaling molecules are directly phosphorylated to translocate to the nucleus?

A patient with a history of recurrent fractures and severe anemia demonstrates diffusely dense bones on radiographs with an "Erlenmeyer flask" deformity of the distal femurs. A deficiency in which of the following enzymes is most commonly associated with the autosomal recessive form of this disease?

Romosozumab is a bone-building medication used for severe osteoporosis. It exerts its anabolic effect on bone primarily by inhibiting which of the following molecules in the Wnt signaling pathway?

A 2-year-old child presents with bowing of the lower extremities and widening of the wrists. Laboratory testing shows normal serum calcium, significantly decreased serum phosphate, normal parathyroid hormone, and normal 25-hydroxyvitamin D. Which of the following is the most likely diagnosis?

Secondary bone healing relies on endochondral ossification and callus formation, which is driven by interfragmentary motion. According to Perren's strain theory, what type of tissue forms when the interfragmentary strain is between 2% and 10%?