Sample size calculation:~Calculation of sample size was done to detect a 15% difference in the VAS score between two groups detected that at least 27 patients were needed at an α error of 0.05 and 80 % power of the study. The number will be increased to 30 patients to avoid a 10% dropped out patients.~Statistical analysis Statistical analysis will be done by Statistical Package for the Social Sciences (SPSS) v25 (IBM Inc., Chicago, USA). Normality of data will be checked with Shapiro-Wilks test and histogram. Quantitative variables will be presented as mean and standard deviation (SD) and will be compared by unpaired student T test. Categorical variables will be presented as frequency and percentage (%) and will be analysed by the Chi-square test. P value < 0.05 will be considered statistically significant.
To improve the outcome after surgery, effective pain control is needed. The aim of the current study was to compare the efficacy of ultrasound guided erector spinae plane block versus the intra articular injection of local anesthetic for post-operative analgesia in patients undergoing shoulder arthroscopy.