1. Department of Trauma and Orthopaedic Surgery, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
2. Barts Health NHS Trust, London, UK
3. Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
4. Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Centre for Statistics in Medicine, University of Oxford, Oxford