Sample size
pain
COMPLICATIONS
Since there was no comparative study on the pain intensity after the injection of BTX-A at the time of designing this research, no effect size was available from the literature. Therefore, the authors assumed a conservative effect size (0.25) as well as a high power (90%), resulting in a sample size of 676 participants. The sample size was augmented to 730 patients to offset additional variables besides pain (i.e. 2-week complications). Since there was no limit on the time frame of the study and also since there was a large number of individuals agreeing to participate, we did not anticipate any particular issues in curating the needed data.