Statistical analysis
Data were gathered, tabulated, and statistically analyzed with SPSS version 19 (Statistical Package for Social Studies) developed by IBM, Illinois, Chicago, USA. The range, mean, and standard deviations of numerical variables were computed. The differences between the observations of bone density between groups were tested using a one-way analysis of variance. Meanwhile, the differences of bone density within each group were tested using repeated measurement analysis of variance. For other variables, which were not normally distributed, the differences of observations between groups were tested by Kruskal–Wallis test, and differences within groups at different follow-up periods were assessed by Friedman test. The significance level was set at 