1. Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
2. Department of Trauma and Orthopaedic Surgery, Barts Health NHS Trust, London, UK
3. Oxford Trauma and Emergency Care, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, UK
4. Statistics and Epidemiology Unit, Warwick Medical School, University of Warwick, Coventry, UK