1. Department of Orthopeadics, Xiangya Hospital Central South University, Changsha 410008, P. R. China
2. National Clinical Research Center for Geriatric Disorders (Xiangya Hospital), Changsha 410008, P. R. China
3. Centers for Disease Control and Prevention, Zhuzhou 412008, P. R. China
4. Department of Orthopeadics, The First Affiliated Hospital, Medical College of Zhejiang University, Hangzhou 311121, P. R. China