1. Division of Surgery & Interventional Science, University College London, Royal Free Campus, London NW3 2QG, UK
2. Centre for Rheumatology & Connective Tissue Disease, University College London, Royal Free Campus, London NW3 2QG, UK
3. Department Of Surgery, Lister Hospital, Coreys Mill Lane, Stevenage, Hertfordshire SG1 4AB, UK