Sample Size Estimation The sample size was estimated with the help of PS software (power and sample size calculation software) 3.0.43 with a power of 80% and a significant level of 0.05. The estimation was based on Visual Analog Score (VAS) with assuming 50% of difference in mean postoperative pain score. The total estimated sample size is 22 patients in each arm for our study. However, with the inclusion of 20% drop out rate, the total number of patients needed for this study is 27 patients in each arm.