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).