The Continuous Fragility Index of Statistically Significant Findings in Studies Based on High Levels of Evidence Comparing Interventions for Femoroacetabular Impingement Syndrome.

Abstract

Critical analysis of studies with high level of evidence has relied on the significance set by the reported <i>P</i> values. However, this strategy steers readers toward categorical interpretation of the data; therefore, a more comprehensive approach of data analysis is warranted. The continuous fragility index (CFI) allows for frailty interpretation of any given study's continuous outcome results. To calculate the CFI of high-level quality studies reporting significant continuous outcomes on comparison of treatment modalities for management of femoroacetabular impingement syndrome. Meta-analysis; Level of evidence, 2. Three databases (PubMed, Embase, Cochrane) were queried from inception to February 2024 utilizing Boolean operators to combine variations of the following search terms: "femoroacetabular impingement, randomized controlled trials or prospective cohort." Studies were included if level of evidence 1 or 2, and a statistically significant outcome was reported for any continuous outcome. CFI calculation was performed for all significant outcomes to obtain a study-specific mean CFI and also for the primary outcome of each study. Mean CFI was also calculated for outcomes reported to be significant in >3 studies. Additionally, multivariable linear regression was utilized for assessment of variables associated with achievement of a higher CFI. Thirteen studies totaling 1316 patients were included for analysis: 11 level of evidence 1 and 2 level of evidence 2 studies. A total of 48 outcomes reaching significance were extracted, with 8 representing primary outcomes. Study-specific mean (SD) CFI was 8 (9.3), whereas primary outcome mean CFI was 12.5 (12). In 4 of the 13 studies, the number of hips lost to follow-up was greater than the study CFI. Outcome-specific mean CFI was obtained for 5 outcomes reported in >3 studies. Multivariable linear regression revealed that larger sample size and greater journal impact factor had a significant positive association with a higher overall CFI value (<i>P</i> < .05). The mean (SD) number of patient outcome events needed to reverse the significance of a continuous outcome (ie, CFI) was 8.0 (9.3). Nearly one-third of studies had a CFI less than the reported loss to follow-up, reflecting the need for better patient compliance to attain less fragile statistical results. Larger sample size and greater journal impact factor were both predictive of a higher CFI.