Fragility Index as a Measure of Randomized Clinical Trial Quality in Adult Reconstruction: A Systematic Review

Abstract

Background: The Fragility Index (FI) and Reverse Fragility Index are powerful tools to supplement the P value in evaluation of randomized clinical trial (RCT) outcomes. These metrics are defined as the number of patients needed to change the significance level of an outcome. The purpose of this study was to calculate these metrics for published RCTs in total joint arthroplasty (TJA). Methods: We performed a systematic review of RCTs in TJA over the last decade. For each study, we calculated the FI (for statistically significant outcomes) or Reverse Fragility Index (for nonstatistically significant outcomes) for all dichotomous, categorical outcomes. We also used the Pearson correlation coefficient to evaluate publication-level variables. Results: We included 104 studies with 473 outcomes; 92 were significant, and 381 were nonstatistically significant. The median FI was 6 overall and 4 and 7 for significant and nonsignificant outcomes, respectively. There was a positive correlation between FI and sample size (R ¼ 0.14, P ¼ .002) and between FI and P values (R ¼ 0.197, P ¼ .000012). Conclusions: This study is the largest evaluation of FI in orthopedics literature to date. We found a median FI that was comparable to or higher than FIs calculated in other orthopedic subspecialties. Although the mean and median FIs were greater than the 2 recommended by the American Academy of Orthopaedic Surgeons Clinical Practice Guidelines to demonstrate strong evidence, a large percentage of studies have an FI < 2. This suggests that the TJA literature is on par or slightly better than other subspecialties, but improvements must be made. Level of Evidence: Level I; Systematic Review.

The Statistical Fragility of Operative vs Nonoperative Management for Achilles Tendon Rupture: A Systematic Review of Comparative Studies

“…For the outcomes included in this analysis, the median FI was 2.5 (IQR 2-4), the mean FI was 2.9 (±1.58), the median FQ was 0.032 (IQR 0.012-0.069), and the mean FQ was 0.049 (±0.062). These values are consistent with the current orthopaedic literature reporting an average median FI of 3.81 10 – 14 , 17 , 18 , 21 , 23 , 29 – 31 , 36 , 38 , 42 , 47 – 53 , 55 …”

“…These values are consistent with the current orthopaedic literature reporting an average median FI of 3.81 10–14,17,18,21,23,29 –31,36,38,42,47 –53,55 –57 and FQ of 0.048. 10–12,18,21,…”

“…For the outcomes included in this analysis, the median FI was 2.5 (IQR 2-4), the mean FI was 2.9 (±1.58), the median FQ was 0.032 (IQR 0.012-0.069), and the mean FQ was 0.049 (±0.062). These values are consistent with the current orthopaedic literature reporting an average median FI of 3.81 [10][11][12][13][14]17,18,21,23,[29][30][31]36,38,42,[47][48][49][50][51][52][53][55][56][57] and FQ of 0.048. [10][11][12]18,21,23,31,[47][48][49][50][51]53 The hypothesis of this study was confirmed, with more than half (78%) of outcomes analyzed having a loss to follow-up greater than the fragility index for that outcome.…”

“…These values are consistent with the current orthopaedic literature reporting an average median FI of 3.81 [10][11][12][13][14]17,18,21,23,[29][30][31]36,38,42,[47][48][49][50][51][52][53][55][56][57] and FQ of 0.048. [10][11][12]18,21,23,31,[47][48][49][50][51]53 The hypothesis of this study was confirmed, with more than half (78%) of outcomes analyzed having a loss to follow-up greater than the fragility index for that outcome. Furthermore, outcomes from studies with a greater risk of bias and rerupture as an individual outcome were more fragile than the other outcomes observed in this analysis.…”

Statistics in Brief: The Fragility Index

“…Myth 1: There Is a Consensus on What FI Value Is Considered "Fragile" There are no clear thresholds for interpreting the FI and what would be considered "fragile." Although two orthopaedic studies mentioned an FI of 2 as a benchmark for adequate stability [13,18], this benchmark is based on an apparent misinterpretation of previous research that did not intend to provide a cutoff [7]. Some describe a finding as fragile if the FI is equal to or less than the number of patients lost to follow-up.…”