Zhen Li1, Bin Li2, Zhaomin Zheng3, Liu Yang4, Zhuojing Luo4. 1. AO Research Institute Davos Davos Switzerland. 2. Orthopedic Institute, Medical College Soochow University Suzhou China. 3. Department of Spine Surgery The First Affiliated Hospital of Sun Yat-sen University Guangzhou China. 4. Xijing Hospital The Fourth Military Medical University Xian China.