1. University Department of Orthopaedic and Trauma Surgery, Dundee Royal Infirmary, Barrack Road, Dundee DD1 9ND, UK.
2. Department of Orthopaedics, Helsingborg Hospital, S-251 87 Helsingborg, Sweden.
3. Department of Orthopaedics, Ystad Hospital, S-271 36 Ystad, Sweden.