1. Division of Surgery and Interventional Science; John Scales Centre for Biomedical Engineering; Institute of Orthopaedics and Musculoskeletal Science; University College London; The Royal National Orthopaedic Hospital; Brockley Hill Stanmore Middlesex HA7 4LP UK
2. Department of Research and Development, Wollaton Medical Consultancy Ltd.; Nottingham NG8 2RN UK