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Title: Aspirin Safe for Emboli Prevention After Knee Replacement in Selected Patients: AAOS

"Aspirin Safe for Emboli Prevention After Knee Replacement in Selected Patients: AAOS"

By Roberta Friedman, PhD SAN FRANCISCO -- March 7, 2008 -- Aspirin can work well as part of a comprehensive strategy to avoid venous clots after total knee replacement, according to a study presented here at the American Academy of Orthopaedic Surgeons (AAOS) 75th Annual Meeting. Kevin Bozic, MD, Associate Professor in Residence, Department of Orthopaedic Surgery, and Philip R. Lee Institute for Health Policy Studies, University of California, San Francisco, San Francisco, California, presented the findings on March 5. Dr. Bozic called aspirin use a part of a "multimodal care package that lowers risk of venous thromboembolism following total knee arthroplasty." He cited data collected on more than 93,840 patients who had knee replacement surgeries at 307 hospitals between October 2003 and September 2005. In the study, Dr. Bozic and colleagues evaluated 4,719 patients treated with aspirin; 51,923 patients treated with adjusted-dose warfarin; and 37,198 patients treated with low-molecular-weight heparin or fondaparinux. As the data set was so large, small differences that may not have been clinically significant achieved statistical significance, the investigators noted. For instance, aspirin users were younger by 9 years ([P < .001) and had a lower risk score for venous thromboembolism. They were also less likely to have used a sequential compression device.

After statistical correction for patient comorbidities and for characteristics of the hospitals and physicians, the comparison showed that patients using aspirin had less risk for bleeding at the surgical site (odds ratio [OR] = 0.61; 95% confidence interval [CI] = 0.42, 0.89) and a lower rate of deep vein clots or pulmonary emboli (OR = 0.65; 95% CI = 0.53, 0.80) compared with patients who received warfarin or low-molecular-weight heparin or fondaparinux.

Rates of re-operation for surgical-site bleeding did not differ, nor did mortality rate, among the treatment groups.

"We show what happens in real practice when you don't get the doses exactly as prescribed," Dr. Bozic said. "There is a group of patients for which aspirin use is appropriate."

He added that he takes issue with guidelines of the American College of Chest Physicians that do not recommend aspirin in patients receiving total knee replacements. The guidelines are based on retrospective studies, he added, as is his report, and what is clearly required is an appropriate prospective trial of the treatments.

[Presentation title: Is There a Role For Aspirin in Venous Thromboembolism Prophylaxis Following Total Knee Replacement? Abstract 073]

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