The Fragility of Statistical Findings in Achilles Tendon Injury Research: A Systematic Review

Abstract

Introduction: Probability analysis with the reporting of P values is often used to determine the statistical significance of study findings in the Achilles literature. The purpose of this study was to determine the utility of applying a fragility analysis to comparative trials evaluating Achilles tendon injuries. Methods: We identified all dichotomous outcome data for comparative studies of Achilles tendon injuries published in 11 orthopaedic journals from 2000 to 2020. The fragility index (FI) was determined by the number of event reversals required to change a P value from less than 0.05 to greater than 0.05, or vice-versa. The associated fragility quotient was determined by dividing the FI by the sample size. Results: Of the 51,357 studies screened, 1,487 met the search criteria, with 51 comparative studies and 177 total outcome events included for analysis. The overall FI was only 4 with an associated fragility quotient of 0.048. One-half of the studies failed to report lost to follow-up data, with an additional 21.6% reporting loss to follow-up of greater than or equal to 4. Conclusion: Our fragility analysis suggests that Achilles tendon injury outcomes are not as statistically stable as previously thought and should be interpreted with caution.

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

“…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.…”

“…(70.5%). 48 The findings from this study add to the growing body of evidence supporting the inclusion of fragility indices and quotients in studies focused on Achilles tendon rupture management and the orthopaedic literature as a whole.…”

The Statistical Fragility of Platelet-Rich Plasma as Treatment for Chronic Noninsertional Achilles Tendinopathy: A Systematic Review and Meta-analysis

“…These values are on par with prior studies assessing statistical fragility in the orthopaedic literature. 11 , 13 , 14 , 23 , 24 , 29 , 31 , 32 , 34 Most pertinently, Parisien et al 31 evaluated the statistical fragility of unspecified comparative trials for Achilles tendon pathology, presenting an overall FI of 4 and associated FQ of 0.048 for 51 outcome events. Parisien et al 32 further studied the statistical fragility of PRP utilization in rotator cuff repair and found an overall FI of 4 and FQ of 0.092 for 177 outcome events.…”