Reverse Continuous Fragility Index Misleads in Biceps Tenotomy Versus Tenodesis Trials: The Case for a Continuous Fragility Score and Quotient

Abstract

Shoulder surgeons regularly choose between biceps tenotomy and tenodesis during rotator cuff repair, and that choice is guided by evidence synthesis built on fragility analysis of the underlying randomized controlled trials. A recent analysis of seven such trials reports a mean reverse continuous fragility index (rCFI) of 17.7 and concludes that the noninferiority findings are moderately stable — a conclusion that flows directly into how surgeons counsel patients and how guidelines grade recommendations. The rCFI calculation simulates a reconstructed patient-level data set from published summary statistics and returns an iteration count that varies with the random seed; its normalization, labeled the "reverse fragility quotient," divides simulated transfers by the number of real patients. A measurement that shifts with investigator choices and mixes simulated with real quantities cannot serve as a foundation for clinical decisions. The continuous fragility quotient (CFQ) is a structurally different construction: it computes a deterministic value on the interval from zero to one directly from the Welch t-statistic using the same published inputs, with no simulation involved. Replacing rCFI with CFQ gives surgeons, patients, and guideline committees a reproducible measurement they can rely on — a foundational requirement for honest evidence synthesis and sound clinical recommendations.