Infections in Total Hip and Total Knee Arthroplasty: Development of a Score To Assess Endogenous Risk of Surgical Site Infections

Background: Surgical site infections (SSI) are a dreaded complication of total hip (THA) and knee arthroplasties (TKA), and are a major public health concern. Risk factors are well known, but no endogenous risk assessment score exists. The objective of this study to develop a score to assess endogenous risk of infection after THA or TKA. Methods: All infections after TKA and THA implanted in the department of orthopedic surgery of a teaching hospital between January 2007 and December 2012 were included. Two control groups were matched to cases on the type of prosthesis (hip or knee; first-line or revision). Results: Twenty-four SSIs after THA and 21 after TKA were registered (respective incidence during the study period: 1.56 and 1.91%). Relevant endogenous risk factors found were: Smoking (adjusted odds ratio=3.9), a BMI greater than 35 kg/mC (1.8), inflammatory rheumatism (7.3), and the number of operations (prosthetic or not) on the involved joint (2.9 per additional surgery). The average score of endogenous infection risk on all analyzed subjects was 3.373.33 (median=3, range=0-17). Mean scores were substantially different among cases and control groups: Respectively 5.84 +/- 4.04 vs 2.13 +/- 2.01 (p<0.0001). With a five-point threshold, the sensitivity and specificity of the score are respectively 62 and 91%. ASA score greater than or equal to three was not found to be substantial risk factor in this study (p=0.15). Conclusions: Endogenous infection risk score studied here was found to be relevant in discriminating cases from control groups, but requires validation in a larger cohort.