1. State Key Laboratory for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an 710049, P. R. China
2. Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, LS2 9JT, UK
3. John Scales Centre for Biomedical Engineering, Royal National Orthopaedic Hospital, University College London, Stanmore, HA7 4LP, London, UK