Rupert Berkeley1, Daniel Lindsay2, Rob Pollock3, Asif Saifuddin4. 1. Department of Radiology, Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex, HA7 4LP, UK. rupert.berkeley@nhs.net. 2. Department of Pathology, Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex, HA7 4LP, UK. 3. Department of Surgery, Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex, HA7 4LP, UK. 4. Department of Radiology, Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex, HA7 4LP, UK.