How do corticosteroids cause Osteonecrosis?
GCs cause ON by both direct and indirect effects on cells. Direct effects include increased apoptosis of osteoblasts, osteocytes, and endothelial cells. Indirect effects include increased hypercoagulability, decreased angiogenesis, and modulated local vasoactive amine production, which can contribute to the ischemia. Finally, increased intraosseous pressure because of adipogenesis and fat hypertrophy in the bone marrow can decrease blood flow to the area. However, because not all patients who receive steroids get ON, genetic factors are thought to play a role. Genetic differences in the affinity of GCs to bind to their receptors as well as the speed of metabolism of GCs to their inactive forms at the local tissue level may account for why less than half of GC-treated patients get ON.
