How statistically fragile are randomized controlled trials comparing quadriceps tendon autografts with hamstring or bone-patellar tendon-bone autografts in anterior cruciate ligament reconstruction?

Purpose: To determine the statistical fragility of randomized controlled trials (RCTs) which compare the use of quadriceps tendon (QT) autografts to either hamstring tendon (HT) or bone-patellar tendon-bone (BPTB) autografts in anterior cruciate ligament reconstruction (ACLR).

Methods: A search was conducted across PubMed, MEDLINE and EMBASE databases for RCTs comparing QT autografts to HT or BPTB autografts in ACLR from inception to 21 April 2024. Studies that reported ≥1 statistically significant continuous outcome, statistically significant dichotomous outcome and/or nonsignificant dichotomous outcome were included for analysis. The fragility index (FI), continuous fragility index (CFI) and reverse fragility index (RFI) were calculated for significant dichotomous outcomes, significant continuous outcomes and nonsignificant dichotomous outcomes, respectively.

Results: A total of 11 RCTs comprising 716 patients were included. The mean sample size was 65.8 patients. The median FI among nine outcomes from four studies was 1.0 (interquartile range [IQR], 0.5; 95% confidence interval [CI], 0.6-1.4; range 0.5-1.5). The number of patients lost to follow-up at the final follow-up period was more than the study-specific FI in three (75%) studies. The median CFI among 30 outcomes from six studies was 4.9 (IQR, 10.1, 95% CI, 3.9-8.2; range 0-18.2). The number of patients lost to follow-up at the final follow-up period was more than the study-specific CFI in four (66.7%) studies. The median RFI among 10 outcomes from five studies was 5.0 (IQR, 3.5; 95% CI, 3.4-6.6; range 1.0-9.0). The number of patients lost to follow-up at the final follow-up period was more than the study-specific RFI in four (80%) studies.

Conclusion: This systematic review revealed that regardless of the metric used, RCTs comparing QT autografts to HT or BPTB autograft options in ACLR are statistically fragile. While the indices of statistical fragility evaluated in this study are important metrics of robustness to consider, their application in research and clinical practice needs to be further elucidated.

Level of evidence: Level I.