The risk of venous thromboembolism with aspirin compared to anticoagulants after hip and knee arthroplasty

Abstract Background Recent guidelines include aspirin as an option to prevent venous thromboembolism (VTE) in selected patients undergoing hip or knee replacement surgery. However, the efficacy of aspirin after arthroplasty has not been well-defined, particularly in more contemporary patient populations. We compared rates of post-operative VTE between patients who received aspirin-only versus anticoagulants after hip or knee arthroplasty, using data from a large US-based administrative database. Materials and methods We conducted a retrospective cohort study of 231,780 adults who underwent total knee arthroplasty and 110,621 who underwent total hip arthroplasty in 2009–2012 and who received pharmacologic VTE prophylaxis (aspirin or anticoagulant) within the first 7 days after surgery. We compared the risk of post-operative VTE between patients receiving aspirin-only vs. anticoagulants, controlling for clinical and hospital characteristics using multivariable logistic regression with propensity score adjustment. Results Aspirin-only prophylaxis was administered to 7.5% of patients after knee arthroplasty and 8.0% after hip arthroplasty. Post-operative VTE was diagnosed in 2217 (0.96%) patients after knee arthroplasty and 454 (0.41%) after hip arthroplasty. Compared to anticoagulants, aspirin was not associated with a higher risk for post-operative VTE either after knee arthroplasty (adjusted odds ratio and 95% confidence interval [OR] 0.34 [0.24–0.48]) or hip arthroplasty (OR 0.82 [0.45–1.51]). Conclusions Aspirin was uncommonly administered as the sole prophylactic agent after hip or knee arthroplasty in this study. However, patients who received aspirin-only had similar rates of post-operative VTE compared to patients who received anticoagulants. Further research should focus on distinguishing which patients benefit more from anticoagulants versus aspirin after arthroplasty.