Abstract P201: Impact of Special Populations on Thromboprophylaxis and Clinical Outcomes of Patients Undergoing Knee Replacement Surgery in the US

Abstract

Background: New anticoagulants are evaluated in clinical trials which often initially focus on prevention of venous thromboembolism (VTE) after major orthopedic surgery. Unlike clinical trials, real-world surgical patients include special populations of patients with comorbidities or concomitant drug use. Objective and purpose: To evaluate the proportion of special patient groups in a real-world population undergoing knee arthroplasty, and to assess their thromboprophylaxis status and clinical outcomes. Methods: Data were extracted from the IMS' PharMetrics® Patient-Centric database for patients aged ≥ 18 years and undergoing knee arthroplasty during 2007. The primary efficacy end point was the overall rate of hospital acquired VTE as one of the secondary hospital discharge reasons. The overall rate of adverse bleeding events was one of the secondary hospital discharge reasons as the primary safety end point. Results: Of the 19,390 knee arthroplasty patients included in the analysis, 3,279 (17%) were aged ≥ 75 years, 4,368 (23%) used a CYP3A4 inhibitor, and 1,882 (10%) used warfarin chronically. Smaller proportions had atrial fibrillation (AF; 1,334; 7%), renal insufficiency (766; 4%), used antiplatelet drugs (621; 3%), had hepatic impairment (320; 2%), or had a history of acute coronary syndromes (ACS; 288; 2%). Pharmacologic thromboprophylaxis was prescribed to 47% (9,063 of 19,390) of patients. In a logistic regression model, the likelihood of VTE events was increased significantly (all P < 0.05) with AF (odds ratio [OR] 1.41; 95% confidence interval [CI] 1.06-1.88), chronic warfarin use (OR 1.33; 95% CI 1.03-1.72), and each increasing year of age (OR 1.01; 95% CI 1.00-1.02). ACS increased the odds of bleeding events (OR 1.50; 95% CI 1.14-1.97; P < 0.05). The likelihood of rehospitalization for ACS was increased in patients with a history of ACS (OR 5.47; 95% CI 1.93-15.54). Conclusion: Special populations are prevalent in everyday knee surgery patients and certain comorbidities or drug use can be associated with increased odds of VTE events or bleeding. Additional studies on the effects of different patient characteristics on clinical outcomes are warranted, particularly for new anticoagulants where little real-world data exist.