OBESITY AND SURGICAL SITE INFECTION IN PRIMARY TOTAL KNEE ARTHROPLASTY

Abstract

The aim of this study was to evaluate the rate of surgical site infection (SSI) in all patients undergoing a primary total knee arthroplasty (TKA) and to audit the outcomes for those who were obese.

We retrospectively reviewed data for 839 primary TKAs done at a National Arthroplasty Centre over one year (April 2007 – March 2008). Body mass index (BMI) data was available for 824 (98%) of the patients. Surgical site infection (SSI) data had been collected prospectively by the Infection Control team for up to 30 days post-operatively and was available for all patients.

There were 23 patients with SSIs, 22 having superficial SSI and only one patient with a deep SSI. The overall superficial SSI rate was 2.7%. For the BMI< 25 group (9.6% of patients) SSI rate was 1.3%. For BMI 25–30 (31.6% of patients) SSI rate was 2.3%. For BMI 30–35 (31.2% of patients) SSI rate was 1.6%. For BMI 35–40 (19.0% of patients) SSI rate was 3.2%. For BMI > (8.6% of patients) SSI rate was 8.5%. Fisher’s Exact Test between all obese patients (BMI< 30) and those with BMI< 30 showed no significant difference in superficial SSI rates (p = 0.39) but did show a significant difference between superficial SSI rates in the obese class III patients (BMI> 40) and the rest of the cohort (p = 0.008).

Obese class III (BMI > 40) patients are at an increase risk of superficial SSI as compared to other patients undergoing primary TKA. However, obese class I and II patients (BMI 30–40) do not appear to have an increased likelihood of superficial SSI as compared to patients who have BMI< 30.