NEW YORK (Reuters Health) - After hip and knee replacement surgery, the risk of infection in the new joint seems to be four times higher in patients with rheumatoid arthritis than in those with osteoarthritis, a study indicates.

Unlike the more common osteoarthritis that is often associated with aging, rheumatoid arthritis -- or RA -- arises when the immune system mistakenly attacks tissue in the joints, leading to inflammation, pain and progressive joint damage.

Dr. Tim Bongartz of the Mayo Clinic College of Medicine, Rochester, Minnesota, and colleagues examined data on 462 patients with RA who had hip or knee replacements at Mayo Clinic Rochester between 1996 and 2004.

Over an average follow-up of about 4 years, 23 of the joint replacement surgeries -- roughly 4 percent -- were complicated by infection of the new joint.

A total of 255 (39 percent) were revision surgeries, and revision procedures were a significant predictor of post-surgery infection in the prosthetic joint, raising the risk nearly threefold.

Having had a previous infection in the replaced joint was associated with a greater than fivefold increased risk of infection.

Comparing these RA patients with a matched group of patients with osteoarthritis showed that RA was also associated with a greater than fourfold increased risk of infection.

"The identification of patients with RA as being at significantly higher risk of prosthetic joint infections emphasizes the importance of utilizing all possible pre- and postoperative (preventive) measures in this high-risk group," the investigators conclude.

SOURCE: Arthritis and Rheumatism, December 15, 2008

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