Increased blood viscosity in patients with Legg-Perthes disease: a preliminary report.

Based on studies by others, it appears that Legg-Perthes disease is an avascular necrosis of the femoral head due to occlusion of the blood supply. In an effort to delineate the pathogenesis of the disorder, we determined blood viscosity and percent platelet aggregation in 22 patients with Legg-Perthes disease and 21 control patients. Statistically significant higher blood viscosities were found in our patients with Legg-Perthes when compared with normals. No difference was found in the platelet aggregation studies. In accordance with Poiseuille's law, we propose that increased blood viscosity in patients with the affliction could lead to a diminution in blood flow to the capital femoral epiphysis, ultimately resulting in osteonecrosis and symptomatic manifestations of the disease.