Japan's share of articles in orthopedics.

We investigated Japan's contribution to research in orthopedics during the last decade. Articles published during 1991-2000 in highly reputed orthopedics journals were accessed through the MEDLINE database. Articles with an affiliation with a Japanese institution were recorded along with the publication year. The proportions of randomized controlled trials (RCTs), cohort studies, and case reports among the articles from Japan were also generated and compared with the overall number for all articles published in these journals. The shares of the top-ranking countries are presented along with the trend over time. Of the total articles (10 551), Japan's share for the selected journals in orthopedics was 8.3% (878 articles), ranking third in the world, after the United States (50.3%) and the United Kingdom (11.2%). The recent increase in the share was not statistically significant for Japan. Proportions of the level of evidence were lower for Japan-originated articles than for the total articles. Japan's contribution to orthopedics research is higher than that in other biomedical fields, but the number of high-quality clinical research studies conducted in Japan in this field was meager, similar to that in other fields.