An epidemiological study of the effect of fluorides in drinking water on the frequency of slipped capital femoral epiphysis.

Slipped epiphysis of the head of the femur is one of the common orthopedic disorders of adolescents, yet little is known of its etiology. Various factors have been suggested as the cause of slipped epiphysis, including abnormalities of the bone or cartilage in the head of the femur-'l such as those brought about by endocrine irregularities,8'7'9-'6ls9128l'9 ""-"1 trauma,5,t-* mechanical factors"12,"' and heredity.' However, in view of the many anatomic and phy3iological changes which take place in an adolescent, it would seem likely that a variety of factors, rather than any single etiologic agent, are actually involved in its causation. One factor not mentioned in the literature is fluoride in drinking water, which could explain in part the low frequency of slipped epiphysis reported by orthopedists in the Southwestern region of the United States,' where many communities have natural fluorides in their water supply. There is some evidence that fluorides in drinking water protect against such bone diseases of adults as osteoporosis, collapsed vertebrae, and fractures,`" although results from two studies"' have suggested that fluoride levels of higher than the 1 part per million (ppm) recommended for protection of teeth may be necessary before a reduction in incidence of bone diseases occurs. Animal experimentation indicates that there may be some basis for considering the possibility that fluorides protect against slipped epiphysis. It has been found that fluoride is deposited more rapidly in the bones of young growing rats than in mature rats,` that fluoride tends to go to the regions of greater bone growth and better blood supply,`74 that more fluoride is deposited in the epiphysis than in the diaphysis of long bones,4'49' and that the area of greatest concentration of fluorides, at least immediately following administration, is in the region of the epiphyseal cartilage, probably in the most recently calcified bone just below the epiphyseal plate.'