A systematic review of conflicting meta-analyses in orthopaedic surgery

Meta-analyses are important evaluations in orthopaedic surgery, not only to create clinical guidelines, but also because their findings are included in public health and health policy decision making. However, with increasing numbers of meta-analyses, discordant and frankly conflicting conclusions have been reported. We searched for conflicting meta-analyses, ie, those arriving at different conclusions despite following the same research question, identified potential reasons for these differences, and assessed the statistical significance and clinical importance of differences. We identified conflicting meta-analyses on graft choice in ACL reconstruction and the use of hyaluronic acid. We found significant differences in individual results only for meta-analyses on hyaluronic acid, but the 95% confidence intervals of the magnitude of differences included values as much as 40% for ACL meta-analyses. However, our findings suggest most conflicts derive from differences in the interpretation of pooled results rather than in the actual results. Thus conclusions and interpretations from meta-analyses should be scrutinized as critically as those from any other type of study and subjected to reassessment if deemed necessary.