[Epidemiological study on ossification of the posterior longitudinal ligament (OPLL) in the cervical spine--comparison of the prevalence between Japanese and Taiwanese].

The etiology of OPLL still remains obscure. The purpose of this study is to clarify whether OPLL in the cervical spine occurs more often in the Japanese than in the Chinese and the Takasago tribe (native tribe) in Taiwan. Lateral X-ray films of the cervical spine in these inhabitants over the age of 30 years were studied. Results were as follows. The prevalent rate of OPLL in the cervical spine was significantly lower in the Chinese (p less than 0.01) and in the Takasago tribe (p less than 0.05) as compared to the Japanese in Kagoshima. OPLL was found in 2 out of 1,004 Chinese (0.2%), in 2 out of 529 Takasago tribe (0.4%), and in 9 out of 514 Japanese in Kagoshima (1.8%). The incidence of ossification of the anterior longitudinal ligament, Barsony's disease and posterior osteophyte was significantly higher in the Chinese, while there was no significant difference of their incidence between the Takasago tribe and the Japanese in Kagoshima. This study suggests that the difference in the prevalence of cervical OPLL exists between Japanese and Taiwanese. However, further epidemiological survey is needed to ascertain this point.