SURGICAL SITE INFECTION FOLLOWING KNEE PROSTHESES IN ENGLAND

Abstract

Data collected on total knee replacements (TKR) from 77 hospitals in England were analysed to identify risk factors for surgical site infection (SSI).

Demographic, operative, and infection data were collected prospectively over a four-year period by the Nosocomial Infection National Surveillance Scheme.

There were 213 (1.8%) infections reported in 11552 primary TKR of which 82% were superficial, 10% deep incisional, and 8% joint/bone infections. The incidence of SSI in 687 revision of TKRs was 4.1% (71% superficial incisional, 18% deep incisional and 11% joint/bone). In the single variable analysis of primary TKRs, significant risk factors were male sex (p< 0.01), age (p< 0.001), ASA score (p< 0.001), wound class (p< 0.001) and NNIS risk index (p< 0.001). In revision of TKRs, only age (p< 0.01) and pre-operative hospital stay of more than one day (p< 0.02) were found to be significant. Significant risk factors with multi-variable logistic regression were type of procedure (TKR or revision TKR), hospital where the procedure was performed, male sex, and age. The mean length of stay in primary TKRs was 10 days (19 days with SSI) and 12 days in revision TKR (22 days with SSI). The median time to diagnosis for superficial SSI was 7 days for superficial SSIs, 9 days for deep incisional SSIs and 7.5 days for joint/bone infections. Staphylococcus aureus accounted for 35% of the infections and nearly one third of these were methicillin resistant (MRSA).

There is significant inter-hospital variation in the incidence of SSI following total knee replacement. Revision TKR procedures are associated with a significantly higher incidence of SSI than primary TKRs (p< 0.001). Male sex and age are also important risk factors. Patients with SSI had a length of post-operative stay approximately twice that of those without SSI.