Legg-Calvé-Perthes disease and passive smoking.

We carried out a case-control study with 90 patients with Legg-Calvé-Perthes disease (LCPD) and 183 normal children, as controls, selected at random to determine whether the condition of passive smoking is related to the disease. Seventy-one of 90 of the LCPD group (78.9%) were passive smokers. Only 79 of 183 (43.2%) in the control group were passive smokers (p = 0.00000). We did not find any statistical relationship between passive smoking and evolution of the condition (p = 0.42883), Catterall extension (p = 0.60544), final Stulberg result (p = 0.53201), or presence of sequelae (p = 0.53256). We also could not find any statistical difference between ages (p = 0.18). The odds ratio was 5.3203 (95% confidence interval 2.92-9.69). The association between LCPD and passive smoking, after controlling for age and gender, became significant (p = 0.0000). Thus the risk of LCPD in passive smoking children is more than five times higher than in children who are not exposed to smoke. It seems that passive smoking is a factor directly or indirectly associated with LCPD.