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Home > Specialties > Hip > Causes of Avascular Necrosis

Why Does Avascular Necrosis Happen?

No one really understands the cause of AVN, but it appears to be related to a disruption of the blood flow to the femoral head. Four basic mechanisms are implicated: mechanical disruption (e.g., broken hip), external pressure on or damage to a vessel wall (e.g., vasculitis, radiation therapy), arterial thrombosis or embolism (e.g., sickle cell diseases, prednisone, alcohol), and venous or blood outflow occlusion (e.g., infection). Although the relationship between the inciting event and the onset of osteonecrosis is clear in some cases, such as vascular disruption from a femoral neck fracture or arterial thrombosis from sickled blood cells, the inciting event in most cases is poorly understood. There is an increased incidence of osteonecrosis seen in people who chronically use corticosteroids, as well as people who consume more than 3 glasses of wine or 5 beers per week.