Risk factors for osteonecrosis of the femoral head in patients with sickle cell disease.

The mechanisms involved in the pathogenesis of osteonecrosis of the femoral head in sickle cell disease are not fully known. The aim of this study was to identify risk factors for osteonecrosis of the femoral head among sickle cell disease patients. Clinical (frequency of painful crises and hospitalisation) and laboratory parameters (euglobulin clot lysis time, haematocrit, platelet count, and leucocyte count) of 25 consecutive patients with avascular necrosis of the femoral head from sickle cell disease were compared with those of 26 age- and sex-matched sickle cell disease patients without avascular necrosis. The group with avascular necrosis of the femoral head (mean age 23.7+/-4.9 years) had a significantly higher rate of painful crises (p = 0.03) and hospitalisations per year (p = 0.002) than the group without avascular necrosis (mean age 21.6+/-5.2 years). The group with avascular necrosis also had a significantly higher euglobulin clot lysis time than the group without avascular necrosis (p = 0.001). In conclusion, it appears that not all patients with sickle cell disease have impaired fibrinolytic activity. The aetiology of avascular necrosis in sickle cell disease is multifactorial.