Computational protocol: No difference in the functional improvements between unilateral and bilateral total knee replacements

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Protocol publication

[…] Prior to the study, we used G*Power to perform a t-test of the difference between two independent means to calculate the required sample size [], and effects were detected in a two-sided test with a power of (1 − β) = 80% at a significance level of 0.05. Other calculation settings were as follows: (1) the hypothetical proportion of patients selecting bilateral TKR was 40% based on clinical experience, (2) minimally clinically important differences (MCID) were at least 15 points for the WOMAC and 10 points for the SF-36 [], and (3) the standard deviations of functional changes were approximately 20, as shown in a previous study []. Based on these settings, the required sample size for calculation was at least 60 subjects for the WOMAC and 133 subjects for the SF-36. [...] All data were analyzed using the R statistical program (version 3.1.1) with the geepack package, and graphs were drawn using bear, ggplot2 and metafor packages. […]

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