1. Department of Orthopaedics; Xijing Hospital; Fourth Military Medical University; 127 Changle Western Road Xi'an 710032 P.R. China
2. Department of Orthopaedics; Air Force General Hospital; 30 Fucheng Road Beijing 100142 P.R. China
3. Department of Pathology; PLA General Hospital; 28 Fuxing Road Haidian District Beijing 100853 P.R. China
4. Department of Orthopaedics and Traumatology; University of Hong Kong; Pokfulam Hong Kong SAR China