Is Aspirin the Best Way to Prevent Blood Clots After THA/TKA?

Marcia Frellick

March 29, 2022

CHICAGO ― Patients discharged to facilities rather than to home after total hip arthroplasty (THA) or total knee arthroplasty (TKA) may need more potent chemoprophylaxis than aspirin to prevent blood clots, new data suggest.

Dr Stefano Muscatelli

Researchers led by Stefano Muscatelli, MD, an orthopedist at Michigan Medicine in Ann Arbor, first aimed to determine whether there was an increase in risk of venous thromboembolism (VTE) in patients who were discharged to facilities such as a skilled nursing facility or inpatient rehabilitation facility, compared with those discharged to home after THA or TKA.

The second aim was to determine whether VTE risk differed between home- and non-home-discharge patients when stratified by the chemoprophylaxis prescribed to prevent VTE.

Findings were presented at the American Academy of Orthopaedic Surgeons (AAOS) 2022 Annual Meeting by co-author Michael McHugh, MD, also an orthopedist at Michigan Medicine in Ann Arbor.

The agents were categorized in three groups: aspirin only; more aggressive anticoagulants, including warfarin, factor Xa inhibitor, direct thrombin inhibitor, low-molecular-weight heparin, pentasaccharide, or antiplatelet agents, with or without concurrent aspirin; and other regimens.

The researchers found that rates of VTE were higher among patients discharged to facilities.

Of 6411 patients included in the study, the overall rate of VTE was 1.05%. Among home-discharge patients (n = 5445), rates of VTE were significantly lower than among patients discharged to facilities (n = 966) (0.83% vs 2.26%; P < .001).

However, the researchers found there was no difference in VTE rates between non-home and home discharge in patients who received more aggressive chemoprophylaxis.

Among discharged patients who received only aspirin, rates of VTE among those discharged to home were significantly lower compared to those discharged to facilities (0.76% vs. 3.83%; P < .001).

"Smoking, BMI [body mass index], procedure type, and preoperative anticoagulation were not associated with the outcome of VTE," McHugh said.

He concluded, "Although we found VTE to continue to be an uncommon complication, non-home discharge is independently associated with higher rates of VTE. Patients should be encouraged to discharge home, but those discharged to non-home facilities after total joint arthroplasty should be considered for more potent chemoprophylaxis than aspirin."

Dr Stuart Fischer

Stuart J. Fischer, MD, with Summit Orthopaedics and Sports Medicine in Summit, New Jersey, who was not part of the study, told Medscape Medical News he found the results inconclusive.

He said there is the potential for confounding because "the people who are sent to a facility after total hip or total knee are inherently less mobile and less able to take care of themselves, so they are at a higher risk for VTE. They are going to be more static."

Fischer noted that over the past few years, there has been a movement away from anticoagulation with more aggressive agents toward aspirin, for several reasons. Providers don't have to monitor aspirin use and can instruct patients to take it once or twice a day. Initial data seem to show that it protects well against VTE.

"The question is, in certain population of patients, is it enough? And that's where the data are unclear," Fischer said.

"It's certainly a useful study, and we need to find out which methods of anticoagulation are most effective in each setting," he said.

Limitations include that it was a retrospective review and that adverse events from more aggressive chemoprophylaxis agents were not assessed. Prophylactic regimens were chosen at the discretion of the treating surgeon.

The researchers excluded bilateral cases, conversion arthroplasty, hip hemiarthroplasty, unicompartmental knee arthroplasty, and deaths.

Muscatelli and McHugh report no relevnt financial relationships. A co-author reports being a paid consultant for DePuy and Zimmer. Fischer reported no relevant financial relationships.

American Academy of Orthopaedic Surgeons (AAOS) 2022 Annual Meeting: Abstract 275. Presented March 23, 2022.

Marcia Frellick is a freelance journalist based in Chicago. She has previously written for the Chicago Tribune, Science News, and, and was an editor at the Chicago Sun-Times, the Cincinnati Enquirer, and the St. Cloud (Minnesota) Times. Follow her on Twitter at @mfrellick.

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