Sample size
The mean 24-h cumulative morphine consumption in the pilot study, which included ten patients, was 6.08 ± 2.17mg in the anterior QLB group and 8.50 ± 2.55mg in the TFPB group. Therefore, with 95% confidence (1 − α), 95% test power (1 − β), and effect size d = 1.032, the sample size calculation determined that a minimum of 22 patients in each group should be included in the study. Given the risk of data loss, each group was designed with 25 patients, for a total of 50 patients.