Statistical analysis
Categorical data were presented as numbers and percentages. The Shapiro-Wilk test was used to determine whether the distributions of continuous variables were normal. Normally distributed continuous data were presented as mean and standard deviation, and non-normally distributed continuous data as median and interquartile range values. The groups of normally distributed data were compared with the independent t-test, and the Mann-Whitney U test was used to compare non-normally distributed data.
The frequencies of categorical variables were compared using the Pearson chi-Square, Yates’ chi-square or Fisher’s exact test where appropriate. Statistical significance was considered when the p value was <0.05. The Bonferroni correction was used in the pairwise comparison of more than two groups with statistically significant differences. The multivariate logistic regression analysis was performed to determine the predictors of complication. All statistical analyses was performed using the Statistical Package for the Social Sciences version 21 (IBM SPSS Statistics; IBM Corp., Armonk, NY).