Risk factors for infection following total joint arthroplasty in rheumatoid arthritis.

Objectives: Determine risk factors for infection following hip or knee total joint arthroplasty in patients with rheumatoid arthritis.

Methods: All rheumatoid arthritis patients with a hip or knee arthroplasty between years 2000 and 2010 were identified from population-based administrative data from the Calgary Zone of Alberta Health Services. Clinical data from patient charts during the hospital admission and during a one year follow-up period were extracted to identify incident infections.

Results: We identified 381 eligible procedures performed in 259 patients (72.2% female, mean age 63.3 years, mean body mass index 27.6 kg/m2). Patient comorbidities were hypertension (43.2%), diabetes (10.4%), coronary artery disease (13.9%), smoking (10.8%) and obesity (32%). Few infectious complications occurred: surgical site infections occurred within the first year after 5 procedures (2 joint space infections, 3 deep incisional infections). Infections of non-surgical sites (urinary tract, skin or respiratory, n=4) complicated the hospital admission. The odds ratio for any post-arthroplasty infection was increased in patients using prednisone doses exceeding 15 mg/day (OR 21.0, 95%CI 3.5-127.2, p=<0.001), underweight patients (OR 6.0, 95%CI 1.2-30.9, p=0.033) and those with known coronary artery disease (OR 5.1, 95%CI 1.3-19.8, p=0.017). Types of disease-modifying therapy, age, sex, and other comorbidities were not associated with an increased risk for infection.

Conclusion: Steroid doses over 15 mg/day, being underweight and having coronary artery disease were associated with significant increases in the risk of post-arthroplasty infection in rheumatoid arthritis. Maximal tapering of prednisone and comorbidity risk reduction must be addressed in the peri-operative management strategy.