Coagulopathies and osteonecrosis.

Intravascular coagulation of the intraosseous microcirculation (capillaries and venous sinusoids) progressing to generalized venous thrombosis, and less commonly retrograde arterial occlusion, now appears to be the cause of nontraumatic osteonecrosis. However, this coagulopathy is only an intermediary event, which is always activated by some underlying etiologic risk factor(s). Conditions capable of triggering intravascular coagulation include familial thrombophilia (resistance to activated protein C, decreased protein C, protein S, or antithrombin III), hyperlipemia and embolic lipid (alcoholism and hypercortisonism), hypersensitivity reactions (allograft organ rejection, immune complexes, and antiphospholipid antibodies), bacterial endotoxic (Shwartzman) reactions and various viral infections, proteolytic enzymes (pancreatitis), tissue factor release (inflammatory bowel disease, malignancies, neurotrauma, and pregnancy), and other prothrombotic and hypofibrinolytic conditions.