S11.3 RISK OF REVISION FOR INFECTION AFTER PRIMARY TOTAL KNEE REPLACEMENT IN PATIENTS WITH RHEUMATOID ARTHRITIS. A COMPARISON OF PATIENTS WITH RHEUMATOID ARTHRITIS AND PRIMARY OSTEOARTHRITIS FROM THE NORWEGIAN ARTHROPLASTY REGISTER

Abstract

Objectives: The major objective of the present study was to investigate the risk of revision of infection after primary total knee replacements (TKR) in patients with rheumatoid arthritis (RA) during a 13-year period. We wished to compare RA patients with OA patients in order to detect differences in the risk of revision for infection, and to compare changes in the risk for the two patient groups over time. Furthermore we studied the time from primary implantation to revision for infection in the two groups.

Patients and Methods: From January 1994 to June 2008, 2482 primary TKRs in patients with RA and 25189 in OA patients were identified in the Norwegian Arthroplasty Register. Kaplan-Meier survival curves, with revision for infection as the endpoint, were constructed. Cox regression analyses were performed to calculate relative risk (RR) of revision for infection according to diagnosis, age, gender, year of surgery (from 1994 through 2000 and from 2001 to June 2008) and time of revision related to the time of primary TKR. All relative risks were adjusted for the other variables.

Results: The 5-year revision rate for infection of TKR was 1.1% in RA patients and 0.5% in OA patients. Rheumatoid arthritis patients had a 1.7 (95%CI 1.2–2.6) times higher risk of revision for infection compared to the control group (OA patients). The patients who had TKR surgery in the later period had a decreased risk of revision for infection (RR 0.72, 95%CI 0.53–0.98) compared to the time period 1994–2000. Furthermore, the risk of revision for late infection in RA patients, increased compared to OA from 4 years after the index operation.

Conclusion: Patients with RA undergoing total knee replacement surgery were at a higher risk of revision for prosthetic joint infection and had a higher risk of late infections leading to revision, than patients with OA. These findings emphasizes the importance of preoperative management and optimizing preventive strategies, especially in this patient group.