1. Department of Trauma and Orthopaedics, Glasgow Royal Infirmary, Gatehouse Building, 84 Castle Street, Glasgow, G4 0SF, UK.
2. Public Health Sciences Section, Division of Community Health Sciences, The University of Edinburgh Medical School, Teviot Place, Edinburgh EH8 9AG, UK.
3. Department of Orthopaedics Queen Margaret Hospital, Whitefield Road, Dunfermline KY12 0SU, UK.