Decreased fibrinolytic potential in patients with idiopathic avascular necrosis and transient osteoporosis of the hip.

A thrombotic etiology has been suggested as the cause of idiopathic avascular necrosis of the hip, although the underlying pathophysiological mechanisms are unknown. Transient osteoporosis of the hip has also been suggested to represent bone marrow edema that may be related to ischemia. We evaluated four patients with idiopathic avascular necrosis and one patient with transient osteoporosis of the hip for thrombotic potential placing a special emphasis on the fibrinolytic system. All five patients had identifiable abnormalities of fibrinolysis. Four patients had elevated levels of plasminogen activator inhibitor (PAI-1) and one patient had an inadequate increase in tissue plasminogen activator (tPA) post venous occlusion. Serum triglycerides were increased in three of the patients. These findings suggest an association between decreased fibrinolytic potential and the subsequent development of avascular necrosis and transient osteoporosis of the hip. These patients should have an evaluation of the fibrinolytic system with tPA and PAI-1 levels as well as a lipid profile.