1 Royal College of Surgeons (England) Surgical Interventional Trials Unit (SITU), Botnar Research Centre, Headington, Oxford, OX3 7LD, UK; Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, National Institute of Health Research (NIHR) Biomedical Research Centre, University of Oxford, Headington, Oxford, OX3 7LD, UK. Electronic address: david.beard@ndorms.ox.ac.uk.
2 Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, National Institute of Health Research (NIHR) Biomedical Research Centre, University of Oxford, Headington, Oxford, OX3 7LD, UK.
3 Royal College of Surgeons (England) Surgical Interventional Trials Unit (SITU), Botnar Research Centre, Headington, Oxford, OX3 7LD, UK; Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, National Institute of Health Research (NIHR) Biomedical Research Centre, University of Oxford, Headington, Oxford, OX3 7LD, UK.