1. Department of General Surgery, Xiangya Hospital, Central South University, Changsha 410008, P.R. China.
2. Department of Medical Record Information, Xiangya Hospital, Central South University, Changsha 410008, P.R. China.
3. Department of Neurological Surgery, Xiangya Hospital, Central South University, Changsha 410008, P.R. China.
4. Department of Geriatric Medicine, Xiangya Hospital, Central South University, Changsha 410008, P.R. China.