Secondary osteonecrosis in osteoarthritis of the femoral head.

Secondary osteonecrosis was found by pathologic examination in nine (6 per cent) of 150 femoral heads removed surgically for osteoarthritis. The changes were morphologically distinct from the remodeling deformities that supervene late in steroid-induced or idiopathic osteonecrosis. They appeared as infarcts confined to previously eburnated tissue. There were no distinctive clinical or radiologic characteristics. The findings do not lend weight to the hypothesis that unrecognized osteonecrosis is a major etiologic factor in apparently primary osteoarthritis.