The Reverse Fragility Index: RCTs Reporting Non-Significant Differences in Failure Rates Between Hamstring and Bone–patellar Tendon–bone Autografts Have Fragile Results

The reverse fragility index (RFI) is a novel metric to appraise the results of studies reporting statistically non-significant results. The purpose of this study was to determine the statistical robustness of randomized controlled trials (RCTs) reporting non-significant differences in anterior cruciate ligament reconstruction (ACLR) graft failure rates, defined as re-rupture/revision ACLR rate, between hamstring tendon (HT) and bone–patellar tendon–bone (BTB) autografts by calculating RFIs. A systematic review was performed to identify RCTs that compared HT to BTB grafts for ACLR through January 2022. Studies reporting non-significant differences in graft re-rupture and revision ACLR rate (n.s.) were included. The RFI, defined as the fewest number of event reversals needed to change the non-significant graft re-rupture/revision outcome to statistically significant (P < 0.05), was recorded for each study. In addition, the number of studies in which the loss to follow-up exceeded the RFI was recorded. Among the 16 included RCTs, the median (interquartile range [IQR]) sample size was 71 (64–114), and the median (IQR) total number of graft re-rupture/revision ACLR events was 4 (4–6). The median (IQR) graft re-rupture/revision ACLR rate was 4.3