Statistical analysis
Statistical analysis was conducted using SPSS (IBM, Amonk, New York, USA) and Stata Software (Statacorp, LLC, TX, USA; version 15). Categorical variables were expressed as absolute number and percentages. Normal distribution of continuous variables was assessed with the Shapiro-Wilk test. Continuous variables normally distributed were reported as mean ± standard deviation (SD). Continuous variables not normally distributed were reported as median and interquartile range [IQR]. Poisson regression model was used to assess differences between groups in terms of number of complications (a negative binomial regression model was not employed due to no overdispersion). Univariate and multivariate logistic analysis was performed to identify predictors of a negative/non-regular postoperative course.