1. Department of Anaesthesia, Royal National Orthopaedic Hospital, Stanmore, UK
2. Department of Orthopaedics and Musculoskeletal Science, Division of Surgery and Interventional Science, University College London, London, United Kingdom
3. Centre for Rehabilitation Engineering and Assistive Technology (CREATe), Department of Orthopaedics and Musculoskeletal Science, Division of Surgery and Interventional Science, University College London, London, United Kingdom
4. Department of Orthopaedics and Musculoskeletal Science, Division of Surgery and Interventional Science University College London, London, United Kingdom