1. Imperial College London; Department of Surgery and Cancer, Faculty of Medicine; Charing Cross Hospital London UK W6 8RF
2. Medical Research Council Clinical Trials Unit; 222 Euston Road London UK NW1 2DA
3. University of Huddersfield; Ergonomics and Clinical Biomechanics, Spine Research Unit; 30 Queen Street Huddersfield UK HD1 2SP
4. Cantonal Hospital of Fribourg; Fribourg Switzerland 1708
5. Royal Holloway University of London; Department of Psychology; Egham Surrey UK TW20 0EX
6. Nuffield Orthopaedic Centre; Department of Orthopaedic Surgery; Windmill Road Headington Oxford Oxfordshire UK OX3 7LD