1. State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Beijing 100084 P. R. China
2. Key Laboratory of Advanced Materials of Ministry of Education of China School of Materials Science and Engineering Tsinghua University Beijing 100084 P. R. China
3. Department of Orthopedics Shanghai Jiao Tong University Affiliated Sixth People's Hospital Shanghai 200233 P. R. China
4. Shanghai Engineering Research Center for Orthopaedic Material Innovation and Tissue Regeneration Shanghai 200233 P. R. China