The statistical fragility of intramedullary reaming in tibial nail fixation: a systematic review

Purpose To report the statistical stability of prospective clinical trials evaluating the effect of intramedullary reaming on rates of non-union in tibial fractures through calculation of the fragility metrics for non-union rates and all other dichotomous outcomes. Methods Literature search was conducted for prospective clinical trials evaluating the effect of intramedullary reaming on non-union rates in tibial nailing. All dichotomous outcomes were extracted from the manuscripts. The fragility index (FI) and reverse fragility index (RFI) were calculated by determining the number of event reversals required for a statistically significant outcome to lose significance and vice-versa. The fragility quotient (FQ) and reverse fragility quotient (RFQ) were calculated by dividing the FI or RFI by the sample size, respectively. Outcomes were defined as “fragile” if the FI or RFI was found to be less than or equal to the number of patients lost to follow-up. Results Literature search identified 579 results which produced ten studies meeting the criteria for review. There were 111 outcomes identified for analysis, of which 89 (80%) exhibited statistical fragility. For reported outcomes across the studies the median and mean FI was 2, the median FQ was 0.019, the mean FQ was 0.030, the median RFI was 4, the mean RFI was 3.95, the median RFQ was 0.045, and the mean RFQ was 0.030. Four studies reported outcomes which were found to have an FI of 0. Conclusions The studies evaluating the effect of intramedullary reaming on tibial nail fixation demonstrate considerable fragility. On average, two event reversals for significant findings, and four event reversals for insignificant findings are sufficient to alter statistical significance. Level of evidence Level II, systematic review of Level I and Level II studies.