Reverse Fragility Index Comparing Rates of Rerupture After Open Achilles Tendon Repair Versus Early Functional Rehabilitation A Systematic Review of Randomized Controlled Trials

Background: Despite similar published rates of rerupture among patients treated with early functional rehabilitation and open repair for acute Achilles tendon rupture, uncertainty still exists regarding the optimal treatment modality. The reverse fragility index (RFI) is a statistical tool that provides an objective measure of the study's neutrality by determining the number of events that need to change for a nonsignificant result to be significant. Purpose: The purpose was to utilize the RFI to appraise the strength of neutrality of randomized controlled trials (RCTs) comparing the rerupture rates of acute Achilles tendon ruptures treated with open repair versus early functional rehabilitation. Study Design: Systematic review; Level of evidence, 1. Methods: A systematic review was performed including all RCTs comparing the rerupture rates after operative repair and early functional rehabilitation for acute Achilles tendon ruptures. Studies were included that explicitly used early functional rehabilitation, defined as weightbearing and exercise-based interventions initiated within 2 weeks, as compared with open repair and reported a nonsignificant difference in rerupture rates. The RFI, with rerupture as the primary outcome, was calculated for each study (significance threshold, P < .05). The RFI quantifies a study's strength of neutrality and is defined as the minimum number of event reversals necessary to change a nonsignificant result to statistically significant. Results: Nine RCTs were included, with 713 patients and 46 reruptures. The median (interquartile range) rerupture rate was 7.69% (6.38%-9.64%) overall, 4.00% (2.33%-7.14%) in the operative group, and 10.00% (5.26%-12.20%) in the nonoperative group. The median RFI was 3, indicating that an outcome reversal of 3 patients was necessary to change the results from nonsignificant to statistically significant. The median number of patients lost to follow-up was 6 (3-7). Of 9 studies, 7 (77.8%) had a loss to follow-up greater than or equal to its RFI. Conclusion: The statistical nonsignificance of studies reporting equivalent rerupture rates in the management of acute Achilles tendon ruptures with open repair versus nonoperative management with early functional rehabilitation can be reversed by changing the outcome status of only a few patients.