STATISTIC OBSERVATION OF DYSBARIC OSTEONECROSIS IN JAPAN

From 1979 to 1990, the authors examined 5,375 subjects from all over J apan, including 3,554 compressed-air (CA) workers and 1,821 divers. We have conducted long-bone roentgenographies for all suspected cases of Dysbaric Osteonecrosis (DON) (i.e., 4,205 [78.2%] cases) and detected 465 cases of the disease. According to Ohta-Matsunaga's criteria, the number of type A lesions was 8; Type B, 88; Type C, 361; and the asso ciation of Types B+C, 7. The incidence of DON among the X-rayed group was 11.1%. The sites of lesion were the upper femur (73.3%), lower fem ur (9.096), and humerus (17.7%). Since Japan is reported to have a hig h incidence of DON among divers, we have tried to find the possible re asons. We profiled the diving of shell-fishing Ariake divers, who are reported to have DON at a rate of 59.6%, and compared it to the profil e of Izu-Shititoh (Izu seven islands) divers, using the agarose-gel me thod described by Mano et al. As a result of this comparison, the Aria ke divers have been observed to have an atypical and prohibitive patte rn of diving (i.e., repetitive dives in too short intervals, long divi ng times, no decompression stops, and insufficient air deck recompress ion after surfacing). We have concluded that the incidence of DON amon g Japanese divers is not especially high compared to other countries a nd that the Ariake divers present a unique diving profile and an excep tionally high incidence of DON, which does not represent the overall p opulation of Japanese divers.