Osteonecrosis of the humeral head: relationship of disease stage, extent, and cause to natural history.

One hundred fifty-one patients with 200 shoulders affected with osteonecrosis of the humeral head were evaluated for associated factors, the need for prosthetic replacement surgery, the state of the unoperated shoulder, and the existence of prognostic factors. Associated factors included corticosteroid use in 112 shoulders, trauma in 37, Gaucher's disease in 3, sickle cell disease in 3, and radiation necrosis in 1. No cause was evident in 44 shoulders. Ninety-seven shoulders had replacement surgery. The need for replacement surgery was found to be related to extent and stage of humeral head involvement and to diagnosis. Shoulders with a traumatic cause of osteonecrosis required surgery more often (cumulative rate of 77.8% by 3 years). Advancing stage of disease was also related to the need for surgery. By 3 years the cumulative replacement rate was performed in 42% for shoulders with stage 2 disease, 29% with stage 3 disease, 55% with stage 4 disease, and 79% with stage 5 disease. In a similar manner, surgical frequency increased with increasing extent of humeral head involvement. In 60 shoulders not surgically treated that were monitored an average of 8.6 years (range 3.4 to 14.5 years), there was none to occasional moderate pain in 46 and moderate to severe pain in 14. The mean American Shoulder and Elbow Surgeons score was 64.8.