The sample size was determined using methods appropriate for noninferiority trials, assuming 90% power and a significance level of 0.05. To find out whether the early weightbearing is not inferior to nonweightbearing after operation of an ankle fracture, 192 patients were required to have 90% power that the lower limit of an one-sided 95% confidence interval for the difference between two treatments will be above the noninferiority margin of -8, adding 20% of assumed drop-out.