Table 3.

Range of plausible effect sizes and (adjusted) standard deviations of the SRS

Mean group difference	Standard deviation
	0.5	0.6	0.7	0.8
0.5	23	32	43	55
0.6	16	23	30	39
0.7	12	17	23	29

Sample size per group by a range of mean group differences and standard deviations (SDs) on the surgical rating scale (SRS) at 90 % power. A sample size of 60 in total would provide a power of 90 % in case the effect size is slightly lower as observed in Martini et al. [2] of 0.6 points on the SRS and a somewhat increased SD of 0.7 points on the SRS. A drop-out of 10 % is expected and therefore we will include 66 patients