Sample size calculations
According to the data obtained from the pre-test, we assumed that the average postoperative analgesia time in the FICB group was 400 min and 360 min in the control group, with a standard deviation of 60. Based on the abovementioned hypothesis, to achieve 90% statistical power (β = 0.1) with a two-sided confidence interval of 95% (α = 0.05), we used PASS11 to calculate that with a total sample size of 80 patients, each group should contain 40 patients. Considering the likelihood of screening failures and dropouts, we requested permission from the Institutional Review Board to enroll up to 25% more patients.