1. Department of OrthopaedicsShanghai Jiao Tong University Affiliated Sixth People's HospitalShanghai Jiao Tong University Shanghai 200233 P. R. China
2. State Key Laboratory of High Performance Ceramics and Superfine MicrostructuresShanghai Institute of CeramicsChinese Academy of Sciences Shanghai 200050 P. R. China
3. Center of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China