*2.5. Statistical Analysis*

Data collection and statistical analysis were investigated with the free online software EasyMedStat (www.easymedstat.com; Neuilly-Sur-Seine; France). Continuous data were expressed as mean (standard deviation, minimum–maximum) and categorical data were given as absolute and relative frequencies (%). To compare differences between preoperative and last FU data, the Student t-test for paired data or the Wilcoxon signed-rank test were used accordingly. Survival rate without a revision surgery and its 5% pointwise confidence intervals were estimated with the method of Kaplan Meier. The significance level was set at *p* < 0.05.
