Incidence of nontraumatic osteonecrosis of the femoral head in the Japanese population

Abstract

Objective: To estimate the incidence rate of nontraumatic osteonecrosis of the femoral head (ONFH) in the Japanese population.

Methods: A survey was conducted to ascertain newly identified patients with nontraumatic ONFH in the Specified Disease Treatment Research Program of Fukuoka Prefecture (population 5 million) between 1999 and 2008. Distributions of age and sex in this population were investigated. Crude incidence rates of nontraumatic ONFH were calculated, and age-adjusted incidence rates were estimated by adjusting the crude values against those for the Japanese standard population in each year.

Results: In Fukuoka Prefecture, 1,244 newly identified patients with nontraumatic ONFH were recruited into the Japanese subsidy program over the span of 10 years. The ratio of men to women was 1.6, comprising 758 men (61%; mean age 48 years) and 486 women (39%; mean age 56 years). The crude incidence rate of nontraumatic ONFH in the 10-year period was 2.58 cases per 100,000 person-years (range 1.54-3.66). The mean age-adjusted incidence rate was 2.51 cases per 100,000 person-years.

Conclusion: This study showed that the incidence rate of nontraumatic ONFH was 2.51 cases per 100,000 person-years in the Japanese population.