Slipped capital femoral epiphysis. A study of 68 cases in the eastern half area of Japan.

Slipped capital femoral epiphysis is an uncommon disease among children in Japan. Eighty-one hips in 68 patients collected in the eastern half area of Japan were examined and studies in reference to the incidence, clinical characteristics, and results of treatment. The estimated yearly incidence rate in boys was 0.3 to 0.5 per 100,000 in the population between 10 and 14 years old. The higher incidence of boys (a 5.8 to 1 predilection for males) was characteristic. The disease was extremely rare in girls. Although Japanese children are generally neither as tall nor as heavy as Americans or Europeans, these patients were relatively taller and also much heavier than average. One of the reasons why children of Japan are not susceptible to slipped epiphysis may be explained by the Japanese physique. Satisfactory results were found in less than half the cases. Poor results were mainly caused by complications such as avascular necrosis and acute cartilage necrosis. The incidence of the latter complication was 20.7 per cent in 58 hips followed longer than a year and a half. The method of treatment seems not necessarily related to the development of chondrolysis. This complication is caused by an unknown genetic factor.