The Fragility Index of Total Hip Arthroplasty Randomized Control Trials: A Systematic Review
Authors: Go CC, Maldonado DR, Go BC, Annin S, Saks BR, Jimenez AE, Domb BG
Journal: Journal of the American Academy of Orthopaedic Surgeons, May 2022
Background
The fragility index (FI) is a metric that indicates how many patients would need to have different outcomes to change the significance of a randomized controlled trial (RCT). This study evaluates the statistical robustness of RCTs on total hip arthroplasty (THA).
Methods
- Systematic review of THA RCTs published from 2015–2020.
- Calculated the FI for each trial and assessed its relationship with sample size and study characteristics.
Key Findings
- Median FI was 2, indicating that the statistical significance of many studies hinged on the outcomes of just two or fewer patients.
- Six studies had an FI of 0, raising concerns about the reliability of their findings.
- Larger sample sizes correlated with higher fragility, suggesting that even well-powered studies may have statistically fragile conclusions.
Conclusions
The FI is a valuable complement to traditional measures like P values, providing insight into how robust—or vulnerable—study conclusions are to small changes in outcomes.
What Does This Mean for Providers?
When evaluating evidence from THA RCTs, providers should consider the fragility index alongside P values and effect sizes. A low FI may signal that results are statistically weak, even if they appear significant. This reinforces the importance of critical appraisal and cautious interpretation when applying trial data to clinical decision-making.