Sample size and statistical analysis
LISB
This study was designed to compare the non-inferiority of the anesthesia success rate in MISB and LISB undergoing surgery at or below the elbow. Previous studies reported that the success rate of low interscalene brachial plexus block anesthesia for surgery at or near the elbow was approximately 95% when opiates and midazolam were used in advance, and a low dose of propofol was used for continuous sedation [The primary endpoint was assessed by the non-inferiority test for the difference between two proportions (the null hypothesis that the difference in the anesthesia success rate was greater than or equal to 15% vs. the alternative hypothesis that the difference was less than 15%). The 95% confidence interval for the difference in anesthesia success rate between MISB and LISB was calculated. If the lower 95% confidence limit was above –15%, the anesthesia effect of MISB was deemed to be non-inferior to LISB.For other outcomes, after confirming the normality of distribution using the Shapiro–Wilk test, continuous variables were compared using the t-test or Mann–Whitney test. As appropriate, continuous variables were presented as means ± SDs or median (interquartile range). Categorical variables were compared by the chi-square or Fisher exact test and presented as numbers and percentages. Data analysis was performed using SPSS software (Statistical Program for Social Sciences, SPSS Inc., Chicago, Illinois, USA). with a two-tailed 