AJSM - 2026-05-14 - Journal Article
Low Fragility Index Undermines Confidence in ACL Graft Superiority: A Systematic Review and Fragility Index Analysis.
Mahatme RJ, Moore SA, Gangavaram A, Anderson W, Campa W, Grawe BM
Topics
Key Takeaway
Across 29 ACL reconstruction RCTs, the median fragility index was 2.0, meaning most statistically significant graft comparisons reverse with a change of just 2 events.
Summary Depth
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Summary
This systematic review applied fragility index (FI), reverse FI (rFI), fragility quotient (FQ), and reverse FQ (rFQ) analysis to 29 RCTs comparing HT, BPTB, QT, and allograft ACL grafts. Of 179 analyzable outcomes, only 21 (10.5%) reached statistical significance, and all graft comparisons yielded FI ≤2.5; in 89.7% of studies, loss to follow-up met or exceeded the FI or rFI. Revision ACL, secondary surgery, and medical complications were the most fragile outcomes (FI=1.0), while HT showed the highest FQ (0.034) among significant outcomes—attributable to study volume rather than demonstrated clinical superiority.
Key Limitation
The analysis is restricted to dichotomous outcomes, excluding the continuous functional and patient-reported outcome measures that most directly inform shared decision-making in graft selection.
Original Abstract
BACKGROUND
Graft selection is a key factor in anterior cruciate ligament reconstruction (ACLR), yet the statistical robustness of comparative outcomes remains unclear. Reliance on P values may overstate confidence in clinical differences.
PURPOSE
To assess the statistical fragility of dichotomous outcomes in randomized controlled trials (RCTs) comparing hamstring tendon (HT), bone-patellar tendon-bone (BPTB), quadriceps tendon (QT), and allograft ACL grafts.
STUDY DESIGN
Systematic review and fragility analysis; Level of evidence, 1.
METHODS
A systematic search of PubMed, Embase, and Medline (June 2025) identified RCTs comparing 2 ACL graft types with >1 dichotomous outcome. Outcomes were analyzed for fragility index (FI), reverse FI (rFI), fragility quotient (FQ), and reverse FQ (rFQ); those with zero events in both groups were excluded. Median FI and rFI values were compared across graft types and outcome categories, and significant outcomes were stratified by graft type.
RESULTS
A total of 29 RCTs (200 outcomes) were included; 179 outcomes (89.5%) were analyzed, and 21 (10.5%) showed significant results. Overall median FI and rFI were both 2.0 (interquartile range: FI 1.0-5.0, rFI 1.0-4.0). In 26 studies (89.7%), loss to follow-up exceeded or equaled the FI or rFI. HT versus BPTB was the most common graft pair comparison (72.1%). All graft comparisons had high fragility (FI ≤2.5). Radiographic complications and knee complications had relatively high FIs (6.5 and 4.5), whereas medical complications, revision ACL, and secondary surgery were most fragile (FI = 1.0). Among significant outcomes, HT had the highest FQ (0.034), followed by QT (0.026) and BPTB (0.016); none favored allografts.
CONCLUSION
Many ACLR RCT findings were fragile, with most significant results reversible by altering 2 events. Loss to follow-up often exceeded fragility thresholds, raising reliability concerns. Although HT had the greatest number of significant outcomes and highest FQ, this likely reflects study volume rather than clinical superiority. High-powered RCTs with standardized outcomes and fragility reporting are needed to clarify graft effectiveness.