Statistical analysis
REGRESSION
Data were collected in spreadsheets (Excel, Microsoft Office, Redmond, US). Treatment site (test or control) was the primary predictor variable. Descriptive statistics recorded mean and standard deviation for continuous quantitative variables, absolute and relative frequencies for categorical data. Shapiro–Wilk test was used to evaluate the normal distribution of each variable. To compare the two study groups, the analysis of variance was performed using a two-tailed Student t-test for normal distributions. Alternatively, the non-parametric Wilcoxon test was performed. Linear regression analysis allowed to correlate the outcomes variable with the surgical time. The level of significance was set at a = 0.05. Statistical analysis was conducted using the software STATA (STATA 11, StataCorp, College Station, TX).