Fragility analysis reveals instability of outcomes in patellofemoral research
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A comprehensive fragility analysis showed instability of reported outcomes in the patellofemoral instability literature, with reversal of study significance found with alteration of only a few outcome events.
Michael Constant, BA, of the department of orthopedics at New York-Presbyterian Hospital, Columbia University Medical Center, and colleagues queried the PubMed database from Jan. 1, 2000, to Oct. 10, 2020, for comparative trials in 10 prominent orthopedic journals that reported dichotomous outcomes related to the management of patellofemoral instability. Researchers calculated fragility index and fragility quotient for each individual outcome event and determined the overall fragility index and fragility quotient for all included studies.
Among the 22 comparative studies in the analysis, including 11 randomized controlled trials and 11 nonrandomized trials, researchers performed a fragility analysis on 75 outcome events and found a median fragility index of 3 and a median fragility quotient of 0.043. Results showed a loss to follow-up greater than the overall fragility index in 27% of the studies included, suggesting the maintenance of the follow-up may have resulted in the reversal of significance.
“The result of the comprehensive fragility analysis demonstrated a lack of robustness in [patellofemoral instability] research with the alteration of only a few outcome events required to reverse statistical significance,” the authors wrote, further recommending supporting statistical integrity of future trials through triple reporting of the P value, fragility index and fragility quotient.
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Michael Constant, BA, and colleagues analyzed 22 comparative trials in the patellofemoral instability literature, reporting a median fragility index of 3 and fragility quotient of 0.043. These findings are consistent with several recent larger studies performed in broader orthopedic topics, such as trauma and sports medicine, in which the authors have reported the prevalence of statistically fragile results.
As this study focused on the robustness of reported outcomes, the topics of the trials that were included were not discussed; however, given the fewer number of trials in this area, as well as the multifactorial nature of patellar instability and heterogeneity in treatment options, it would be interesting to understand which studies were included this analysis. Overall, the authors highlight an important point regarding the need to recognize statistical instability in reported results. As patellofemoral research expands toward larger clinical trials with standardized reporting measures, reporting the fragility index and fragility quotient in addition to the P-value may be an important consideration for future studies.
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