Biology, Genetics & Bone Healing MCQs

Bone morphogenetic proteins (BMPs) play a critical role in fracture healing by promoting osteoinduction and driving mesenchymal stem cells toward an osteoblastic lineage. BMPs transmit their intracellular signals primarily by phosphorylating which of the following downstream mediators?

An 80-year-old man presents with increasing hat size, unilateral hearing loss, and bowing of his right tibia. Laboratory testing shows a significantly elevated serum alkaline phosphatase with normal calcium and phosphorus levels. The primary cellular defect initiating this disease process originates from an abnormality in which of the following?

According to Perren's strain theory, what is the maximum strain tolerated by lamellar bone formation during fracture healing?

Sclerostin is a key negative regulator of bone formation secreted by osteocytes. Which of the following intracellular signaling pathways does sclerostin directly inhibit?

A patient with chronic kidney disease presents with profound hypocalcemia and secondary hyperparathyroidism. The patient's bone disease is primarily exacerbated by a deficiency in which of the following enzymes?

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is utilized to enhance bone healing. BMP-2 initiates the osteoinductive cascade by binding to a cell surface receptor, which directly activates which of the following intracellular signaling molecules?

A massive segmental bone defect is reconstructed using a freshly harvested autogenous cancellous bone graft from the iliac crest. This graft provides which of the following biologic properties for bone regeneration?

Which of the following describes the primary mechanism by which intermittent, low-dose administration of parathyroid hormone (PTH) increases bone mass?

Romosozumab is a monoclonal antibody recently developed for the treatment of osteoporosis. It functions by inhibiting sclerostin. Sclerostin primarily exerts its effect on bone metabolism by inhibiting which of the following pathways?

Bone morphogenetic protein-2 (BMP-2) is utilized clinically to enhance spinal fusion. Upon binding to its cell surface receptor, BMP-2 initiates intracellular signaling primarily through which of the following protein families?

A 4-year-old boy presents with multiple fractures and is diagnosed with malignant infantile osteopetrosis. The defect involves a failure of osteoclasts to create an acidic environment in the resorption pit. A mutation in the gene encoding which of the following enzymes is most likely responsible?

A patient with severe scurvy is found to have significantly weakened bones and bleeding gums. The primary defect in collagen synthesis caused by vitamin C deficiency occurs during which step?

A diaphyseal radius fracture is rigidly fixated with a compression plate, achieving absolute stability and less than 2% interfragmentary strain. The fracture will heal primarily via which of the following mechanisms?

A patient with blue sclerae, hearing loss, and multiple childhood fractures is diagnosed with osteogenesis imperfecta. This condition is most commonly caused by a genetic mutation affecting which of the following?

The nutrient artery of a long bone provides the primary blood supply to the medullary cavity and the inner two-thirds of the diaphyseal cortex. In what direction does the blood flow through the cortical bone?

A 5-year-old child presents with bowing of the lower extremities and a waddling gait. Laboratory tests reveal low serum phosphate, normal serum calcium, and elevated alkaline phosphatase. Genetic testing shows a mutation in the PHEX gene. The overproduction of which factor is directly responsible for the renal phosphate wasting in this patient?

A 65-year-old woman with a history of fragility fractures is started on a nitrogen-containing bisphosphonate (alendronate). At the cellular level, what is the primary molecular target of this medication?

Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) is utilized during an anterior lumbar interbody fusion. BMPs exert their cellular osteoinductive effects primarily by activating which of the following intracellular signaling pathways?

During revision of a loose total hip arthroplasty, periprosthetic tissue is retrieved. Histological analysis reveals abundant macrophages with phagocytosed polyethylene particles. Which cytokine is primarily responsible for initiating the cascade that leads to osteoclast activation and aseptic loosening in this scenario?

A 12-year-old boy presents with multiple bony prominences near his knee and shoulder joints. Genetic testing confirms a mutation in the EXT1 gene. This gene is primarily responsible for the synthesis of which of the following?