The Reverse Fragility Index: Interpreting the Evidence for Arthroscopic Rotator Cuff Repair Healing Associated With Early Versus Delayed Mobilization

Abstract

Background: The American Academy of Orthopaedic Surgeons (AAOS) clinical practice guidelines (CPGs) note “strong” evidence that early and delayed mobilization protocols after small to medium arthroscopic rotator cuff repairs achieve similar rotator cuff healing rates. Purpose: We utilized the reverse fragility index (RFI) to assess the fragility of randomized controlled trials (RCTs) reporting no statistically significant difference in tendon re-tear rates after rotator cuff repair in those undergoing early versus delayed rehabilitation. Methods: Randomized controlled trials used in the most recent AAOS CPGs on the timing of postoperative mobilization after arthroscopic rotator cuff repairs were analyzed. Only RCTs with a reported P value ≥ .05 were included. The RFI at a threshold of P < .05 was calculated for each study. The reverse fragility quotient (RFQ) was calculated by dividing the RFI by the study sample size. Results: In 6 clinical trials with a total of 542 patients, the number of tendon re-tear events was 48. The median RFI at the P < .05 threshold was 4 (range: 3.25–4.75), and the median RFQ was .05 (range: 0.03–0.08). The median loss to follow-up was 6 patients. Of the 6 studies investigated, 3 reported a loss to follow-up greater than their respective RFI. Conclusion: The equivalence in rotator cuff repair healing rates associated with early and delayed mobilization protocols rests on fragile studies, as their statistical non-significance can be reversed by changing the outcome status of only a handful of patients. Consideration should be given to the routine reporting of RFI in clinical practice guidelines including RCTs with statistically non-significant results.