Wenbin Ding1, Hui Liu2, Zhaomin Zheng3. 1. Department of Orthopedics, Shenzhen Sixth People's Hospital, No. 89 Taoyuan Road, Shenzhen, 518052, China. 2. Department of Spine Surgery, The First Affiliated Hospital, Sun Yat-sen University, No. 58 Zhongshan Er Road, Guangzhou, 510080, China. 3. Department of Spine Surgery, The First Affiliated Hospital, Sun Yat-sen University, No. 58 Zhongshan Er Road, Guangzhou, 510080, China. zhengzml@163.com.