Levels of evidence in research published in the Journal of Bone and Joint Surgery (American volume) over the last thirty years

Background: The recent emphasis on evidence-based medicine has led to increasing levels of evidence being published in surgical journals. The purpose of the present study was to review the levels of evidence in reports published in The Journal of Bone and Joint Surgery (American Volume) over the last thirty years. Methods: We reviewed all of the articles published in The Journal in the years 1975, 1985, 1995, and 2005. Cadaver studies, animal studies, basic-science studies, review articles, Instructional Course Lectures, and correspondence were excluded. Articles were scored according to The Journal's levels of evidence for a primary research question. Results: A total of 1058 articles were reviewed. Of these, 134, 123, 120, and 174 articles met the inclusion criteria for the years 1975, 1985, 1995, and 2005, respectively, and were ranked according to level of evidence. The number of articles for each level of evidence rating was then expressed as a percentage of the total number of articles meeting the inclusion criteria for that year. There was a significant trend toward higher levels of evidence, with the combined percentage of Level-I, II, and III studies increasing from 17% to 52% (p < 0.01). The percentage of Level-I studies increased from 4% in 1975 to 21% in 2005. The average level of evidence rating improved from 3.72 to 2.90 during the study period. Conclusions: The level of evidence in The Journal has improved significantly over the last thirty years.