1. Department of Orthopedic Surgery, Surgery Building, The People's Liberation Army General Hospital, Beijing 100000, P.R. China
2. Department of Spine Surgery, Zhongshan Hospital Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian 361004, P.R. China
3. Department of Orthopedics, Spine Surgery, Changzheng Hospital, Second Military Medical University, Shanghai 200003, P.R. China