1. Department of Orthopeadics & Traumatology, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong
2. Department of Materials Science & Engineering, TongJi University, 1239 Siping Road, Shanghai, People's Republic of China
3. Department of Spine Surgery, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China
4. Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, People's Republic of China