Jian Tong1,2, Qingquan Kong3. 1. Department of Orthopedics, Orthopedic Research Institute West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, People's Republic of China. 2. Department of Spinal Surgery, No.1 Orthopedics Hospital of Chengdu, Chengdu, 610000, China. 3. Department of Orthopedics, Orthopedic Research Institute West China Hospital, Sichuan University, Chengdu, Sichuan, 610041, People's Republic of China. kqqspine@126.com.