Dong Wang1, Yunfeng Tang1, Guanglin Wang2. 1. Department of Orthopaedics, West China Hospital, West China School of Medicine, Sichuan University, No. 37, Wuhou Guoxue Road, 610041, Chengdu, Sichuan, People's Republic of China. 2. Department of Orthopaedics, West China Hospital, West China School of Medicine, Sichuan University, No. 37, Wuhou Guoxue Road, 610041, Chengdu, Sichuan, People's Republic of China. wangglfrank@hotmail.com.