Obesity, diabetes, and preoperative hyperglycemia as predictors of periprosthetic joint infection: a single-center analysis of 7181 primary hip and knee replacements for osteoarthritis.

BACKGROUND: Diabetes and obesity are common in patients undergoing joint replacement. Studies analyzing the effects of diabetes and obesity on the occurrence of periprosthetic joint infection have yielded contradictory results, and the combined effects of these conditions are not known.
METHODS: The one-year incidence of periprosthetic joint infections was analyzed in a single-center series of 7181 primary hip and knee replacements (unilateral and simultaneous bilateral) performed between 2002 and 2008 to treat osteoarthritis. The data regarding periprosthetic joint infection (defined according to Centers for Disease Control and Prevention criteria) were collected from the hospital infection register and were based on prospective, active surveillance. Patients diagnosed with diabetes were identified from the registers of the Social Insurance Institution of Finland. The odds ratios (ORs) for infection and the accompanying 95% confidence intervals (CIs) were calculated with use of binary logistic regression with adjustment for age, sex, American Society of Anesthesiologists risk score, arthroplasty site, body mass index, and diabetic status.
RESULTS: Fifty-two periprosthetic joint infections occurred during the first postoperative year (0.72%; 95% CI, 0.55% to 0.95%). The infection rate increased from 0.37% (95% CI, 0.15% to 0.96%) in patients with a normal body mass index to 4.66% (95% CI, 2.47% to 8.62%) in the morbidly obese group (adjusted OR, 6.4; 95% CI, 1.7 to 24.6). Diabetes more than doubled the periprosthetic joint infection risk independent of obesity (adjusted OR, 2.3; 95% CI, 1.1 to 4.7). The infection rate was highest in morbidly obese patients with diabetes; this group contained fifty-one patients and periprosthetic infection developed in five (9.8%; 95% CI, 4.26% to 20.98%). In patients without a diagnosis of diabetes at the time of the surgery, there was a trend toward a higher infection rate in association with a preoperative glucose level of ≥6.9 mmol/L (124 mg/dL) compared with <6.9 mmol/L. The infection rate was 1.15% (95% CI, 0.56% to 2.35%) in the former group compared with 0.28% (95% CI, 0.15% to 0.53%) in the latter, and the adjusted OR was 3.3 (95% CI, 0.96 to 11.0). The type of diabetes medication was not associated with the infection rate.
CONCLUSIONS: Diabetes and morbid obesity increased the risk of periprosthetic joint infection following primary hip and knee replacement. The benefits of joint replacement should be carefully weighed against the incidence of postoperative infection, especially in morbidly obese patients. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.