Thromboembolism prophylaxis failure rates after hip and knee arthroplasty

Background: Aspirin has not traditionally been recommended as monotherapy for venous thromboembolism (VTE) prophylaxis after hip or knee arthroplasty. Recently, the 2012 American College of Chest Physicians (ACCP) guidelines recommended aspirin as monotherapy for VTE prophylaxis. The objective of this study was to retrospectively compare the rate of treatment failure in aspirin treated patients and patients who received anticoagulants. Methods: Patients who underwent hip or knee arthroplasty between May 1, 2011 and July 31, 2013 were identified using the International Classificaton for Diseases (ICD)-9 codes. Patients who developed documented postoperative VTE were identified by quality management chart review or by screening all identified patients who were readmitted within 35 days, or both. Patients were excluded if they were on known anticoagulation or if a prophylaxis regimen could not be determined. Results: In the specified time period, 1486 hip and knee arthroplasty procedures were performed (785 knee arthroplasties and 701 hip arthroplasties) 85 patients were excluded. Documented VTE occurred in 21 patients (1.41%); nine out of 552 aspirin therapies failed (1.63%), and 11 out of 827 anticoagulant therapies failed (1.33%) (P=0.65). One failure occurred in a patient receiving aspirin and dalteparin after arthroplasty and thus is not included in either aspirin or anticoagulant failure groups but is included in the overall failure rate total. Demographic data were similar between groups. There was no difference in ordered nonpharmacologic prophylaxis between groups, and there were no fatal outcomes. Conclusions: This retrospective study suggests that there is no difference between the efficacy of aspirin and anticoagulants for VTE prophylaxis after total hip or total knee arthroplasty.