1. Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK
2. Oxford Trauma and Emergency Care, Kadoorie Research Centre, Nuffield Department of Orthopaedic, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
3. Centre for Statistics in Medicine, Oxford Clinical Trials Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
4. Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK
5. University Hospital Coventry and Warwickshire NHS Trust, Coventry, UK
6. Faculty of Health and Life Sciences, University of Exeter, Exeter, UK