A H R W Simpson1, H Frost2, J Norrie3. 1. Bone & Joint Research, London, UK; George Harrison Law Professor of Orthopaedic Surgery; Department of Orthopaedics, Royal Infirmary of Edinburgh, Edinburgh, UK. 2. School of Health and Social Care Edinburgh Napier University, Edinburgh, UK. 3. Director, Edinburgh Clinical Trials Unit, (ECTU) Co-Director, Centre for Population Health Sciences, Usher Institute, The University of Edinburgh, Edinburgh, UK.