Introduction: Deep infection is a devastating complication following hip arthroplasty. In the early 1970’s Staphylococcus Aureus (SA) was believed to be the causative organism in most cases and Coagulase Negative Staphylococccus (CNS) was widely regarded as a contaminant. It subsequently became recognised that the majority of infections are caused by CNS rather than SA, probably due to the use of peri-operative antimicrobial agents and laminar air flow in theatre.

Aims: The aim of this study was to look at the causative organisms in patients with an infected total hip replacement to see if the pattern of infection has changed with time.

Methods: Between February 1999 and November 2004, 95 patients underwent 1^st stage revision surgery at the Northern General Hospital for definite infection following total hip replacement. At least 5 tissue samples were taken at the time of surgery prior to antibiotic administration. Infection was confirmed when at least 3 of the samples were positive on microbiological culture. We retrospectively reviewed the records of these patients and identified the causative organisms.

Results: The 95 patients were infected with 130 different organisms. Of these 32% were SA including MRSA (7.2%), 27% CNS, 13.6% Enterococcus, 4.8% pseudomonas and 3.2% Streptococcci. 29% of patients had polymicrobial infection.

Discussion: Data published in the literature as well as historical data from our unit suggest that CNS is by far the most common organism causing prosthetic hip joint infection. Our results however, show a recent decrease in the proportion of CNS and an increase in SA and polymicrobial infection.