• Christine Baumgartner, Judith Maselli, Andrew D Auerbach, and Margaret C Fang.
• Division of Hospital Medicine, University of California, San Francisco, San Francisco, CA, USA. christine.baumgartner@insel.ch.
• J Gen Intern Med. 2019 Oct 1; 34 (10): 203820462038-2046.

BackgroundAlthough guidelines now allow the use of aspirin as an alternative to anticoagulants for venous thromboembolism prophylaxis after knee or hip arthroplasty, there is limited data on contemporary use and outcomes with aspirin.ObjectiveTo describe the use of pharmacologic thromboprophylaxis and to assess venous thromboembolic risk with aspirin compared with anticoagulation after knee or hip arthroplasty.DesignRetrospective cohort study using data from the US MedAssets database.PatientsAdults with a principal discharge diagnosis of knee or hip arthroplasty between January 1, 2013, and December 31, 2014.Main MeasuresWe identified charges for medications used for thromboprophylaxis within 7 days after the index surgery from billing records. The primary outcome was postoperative venous thromboembolism identified by International Classification of Diseases, 9th edition codes, from the index hospitalization, rehospitalization within 30 days, or during an outpatient visit within 90 days postoperatively. We compared postoperative thromboembolic risk in patients receiving aspirin-only and those receiving anticoagulants using propensity score-adjusted multivariable logistic regression models.Key ResultsWe identified 74,234 patients with knee arthroplasty and 36,192 with hip arthroplasty who received pharmacologic thromboprophylaxis. Aspirin-only was used in 27.9% of all patients, while 24.2% and 24.1% received warfarin or enoxaparin as prophylactic monotherapy, respectively. Postoperative venous thromboembolism occurred in 495 (0.67%) patients undergoing knee arthroplasty and 145 (0.40%) undergoing hip arthroplasty. Aspirin-only was not related to increased odds of postoperative venous thromboembolism compared with anticoagulants in multivariable adjusted analyses (odds ratio [OR] 0.70; 95% confidence interval [CI], 0.56-0.87, and OR 0.93; 95% CI, 0.62-1.38 for knee or hip arthroplasty, respectively).ConclusionsMore than a fourth of all patients received aspirin as the sole antithrombotic agent after knee or hip arthroplasty. Postoperative thromboprophylaxis with aspirin-only was not associated with a higher risk of postoperative venous thromboembolism compared with anticoagulants after hip or knee arthroplasty.

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