1 Department of Trauma and Orthopaedics, St George's Hospital, St George's University Hospitals National Health Service Foundation Trust, London, United Kingdom.
2 St George's University London, St George's University Hospitals National Health Service Foundation Trust, London, United Kingdom.
3 Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom.