Methods

Data were collected prospectively between October 1998 and February 2002 by a dedicated audit nurse. Pre-operative demographic and medical details were recorded. Operative and post-operative complications were noted. The definitions of surgical-site infection were based on a modification of those published by the Centre for Disease Control (CDC) in 1992. A superficial wound infection had a purulent discharge or positive culture of organisms from aseptically-aspirated fluid, tissue, or from a swab. Deep infection was counted as an infection that required a secondary procedure. Patients were seen at 6, 18 and 36 months post-operatively in a dedicated knee audit clinic and infection details recorded. The association between infection and other factors was tested by chi-squared or Mann-Whitney tests for categorised or quantitative factors respectively.