Idiopathic osteonecrosis of the humeral head.

According to the frequency of occurrence, osteonecrosis of the humeral head ranks immediately after osteonecrosis of the femoral head. Experimental and clinical studies have indicated one or more mechanisms acting alone or in combination and causing necrosis of the bone. Rare cases in which the cause of osteonecrosis remains unknown, are referred to as the idiopathic form of humeral head osteonecrosis. The authors discuss the most recent advances in the etiopathogenesis of osteonecrosis, classification of humeral head osteonecrosis, and the methods of treatment. Three patients are described: two suffering from the idiopathic form and one with osteonecrosis of the humeral head related to an unidentified process affecting the condyles of the knee and both calcanei, and characterized by condensation of the bone.