Statistical analysis
SPSS 22.0 software (SPSS Inc., Chicago, IL, USA) was used for all statistical analyses. Data are presented as the means ± SD or percentages as appropriate. A paired t -test was used to analyze preoperative and postoperative data. Continuous data are presented as medians and ranges, and categorical data are presented as frequencies and percentages. The hospitalization length and hospitalization cost were analyzed using the Mann­-Whitney U test. Categorical variables were analyzed using the chi-squared test or Fisher’s exact test when the number of variables was less than five. P -values <0.05 were considered to be statistically significant.