1. Oxford Clinical Trials Research Unit, Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
2. Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK
3. Health Economics Research Centre, Nuffield Department of Population Health, University of Oxford, Oxford, UK
4. Oxford Trauma, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK