Statistical analysis
COMPLICATIONS, REGRESSION
The SPSS version 23.0 statistical programme (SPSS Inc, Chicago, IL, USA) was used for the statistical analysis and the statistical significance was set to < 0.05. In order to identify the most important factors affecting the occurrence of post-operative complications Classification and Regression Trees (CART) were used [Among more than 20 Classification Trees, the most suitable was selected based on two criteria. First, the selected tree should have the lowest misclassification rate and highest kappa statistic which should exceed 0.4 [