Authors: Everhart JS, Calhoun JH.
Ohio State University, Columbus, OH
Title: Preoperative Anemia of Chronic Disease is a Strong Independent Risk Factor for Surgical Site Infection after Total Joint Arthroplasty
Background: Anemia of chronic disease is a non-specific, non-inflammatory response to many systemic illnesses. Patients with uncontrolled or poorly controlled chronic diseases will often present with anemia that resolves with improved medical management. Though several recent reports have focused on post-operative transfusions as a risk factor for surgical site infection (SSI) after total joint arthroplasty (TJA), we hypothesize that preoperative anemia itself is an independent predictor of SSI after TJA.
Hypothesis/Purpose: Is anemia of chronic disease an independent preoperative risk factor for SSI after TJA?
Methods: Demographic data and preoperative medical diagnoses were obtained for a large single-institution cohort of patients who underwent TJA from 01/2000-10/2011 (n=9214 patients; 3298 primary hip, 876 revision hip, 3253 primary knee, 490 revision knee, 685 primary upper extremity, 104 revision upper extremity, 508 other). Anemia of chronic disease and presence of other comorbid conditions were confirmed by ICD-9 based diagnosis > 30 days prior to surgery. Surgical site infection within 1 year was confirmed by readmission with an infection-associated ICD-9 diagnosis code in combination with elevated inflammatory markers or positive intraoperative cultures. Logistic regression modeling was used to determine the independent association between preoperative anemia and SSI; our findings were validated on a random 20% of the sample held out of the original model.
Results: Preoperative anemia of chronic disease was strongly associated with SSI risk (OR 3.23 CI 2.70, 3.87, Wald test p<0.001) after adjusting for renal function, primary vs. revision status, site of surgery, indication for surgery (primary osteoarthritis, fracture, oncologic surgery, etc.), age, BMI, history of staphylococcus colonization or infection, and chronic comorbid conditions. Our findings were successfully validated on an independent sample (validation OR 3.27 CI 2.31, 4.63; Wald test p<0.001).
Discussion: Preoperative anemia of chronic disease is a strong risk factor for SSI after TJA, regardless of the planned procedure, indication, or combination of medical comorbidities present. Presence of this condition may be indicative of compromised host immunity due to a poorly controlled systemic illness.
Conclusion: Preoperative anemia of chronic disease is a strong independent risk factor for SSI after TJA.