1. Glan Clwyd Hospital, Sarn Lane, Rhyl, Denbighshire LL18 5UJ, UK.
2. University Department of Orthopaedic Surgery, Glenfield General Hospital, Groby Road, Leicester LE3 9QP, UK.
3. Department of Orthopaedic and Trauma Surgery, Middlesborough General Hospital, Ayresome Green Lane, Middlesborough TS5 5AZ, UK.