1. Edinburgh Orthopaedic Trauma Unit, Royal Infirmary of Edinburgh, 51 Little France Crescent, Edinburgh EH16 4SU, UK.
2. Gloucestershire Royal Hospital, 23 Cotham Road, Bristol BS6 6DJ, UK.
3. Department of Orthopaedics and Trauma, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK.