A simple tool to guide choice of antithrombotic therapy following total joint arthroplasty led to a reduction in pulmonary embolism (PE) after being introduced systemwide, according to a prospectively tracked evaluation of a large patient cohort. The results of the study were reported in an abstract scheduled for release at the annual meeting of the American Academy of Orthopaedic Surgeons. The meeting was canceled because of COVID-19.
“We developed a simplified scoring system for evaluating risk of thromboembolism and guiding prophylaxis that led to a significant reduction in events across a large integrated health care system,” reportedassociate medical director for hip and knee preservation and orthopedic research at Intermountain Healthcare, Salt Lake City, Utah.
The goal of the methodology was to create a uniform and evidence-based approach to risk assessment in order to guide selection of appropriate venous thromboembolism (VTE) prophylaxis. The tool takes into account the need to individualize antithrombotic drugs for risk of both VTE and for bleeding.
“VTE is a major threat following total joint replacement, but not all patients require anticoagulants. Recent evidence supports a shift to aspirin for low-risk patients,” explained Dr. Wylie in an interview.
The risk tool assigns points for such factors as history of VTE, older age, history of coronary artery disease, history of cancer, and increased body mass index. There are two possible ratings to guide strategies. Those with standard risk are candidates for 81 mg of aspirin twice daily. Those with high risk are candidates for 2.5 mg of apixaban, also administered twice daily. Custom dosing of warfarin is an alternative for the latter group. Regardless of strategy, prophylaxis is administered for 30 days following arthroplasty
“The risk score is calculated automatically, because you have to click a box in the electronic medical record for all of those factors as part of admission orders,” Dr. Wylie said.
The protocol was introduced in July 2017 and adoption was tracked prospectively over 18 months. In an evaluable cohort of 20,284 patients, PE rates in the 71% of patients adherent to the protocol were compared with the 29% who were not.
Over the observation period, the rates of PE were 0.34% and 0.62% (P = .004) for those adherent and nonadherent, respectively. The rate of unplanned readmissions and death, which were secondary outcomes, were both numerically lower in the group treated by adherent surgeons, but the differences did not reach statistical significance.
Adoption of the protocol by surgeons did increase over the course of the observation period, and this correlated with a decrease in unplanned readmissions. Bleeding-related readmission was a rare event in this analysis and did not significantly increase over time, according to Dr. Wylie.
The risk assessment tool, developed by a multispecialty team at Intermountain Healthcare, was based on a review of hundreds of published papers and guidelines, according to, who is the associate medical director of total joint replacement at Intermountain and was a coauthor on this study. A member of the team that developed the risk assessment tool, Dr. Momberger noted that new risk score was developed at a time when clinicians have been moving quickly away from warfarin to direct oral anticoagulants.
“None of our surgeons were using the same VTE prophylaxis when we started this project,” Dr. Momberger said. This was a motivation for developing a systemwide approach. In the 22 participating hospitals, there were 50 surgeons performing total knee arthroplasty and 40 surgeons were performing total hip surgery at the time the new protocol was introduced.
Further analyses will provide a more detailed analysis of the effect of the protocol on other thrombotic events, including deep vein thrombosis, and on cost. Since these data were analyzed, protocol adoption has increased and now exceeds 80%, according to Dr. Wylie.
Although a standardized approach to VTE prophylaxis following total joint arthroplasty is attractive, the ideal strategy remains controversial, according to Sunny Parikh, MD, an orthopedic surgeon affiliated with Colchester (England) General Hospital.
As a coauthor of a recent study that quantified symptomatic VTE rates at his and a neighboring hospital over a 3-year period (), Dr. Parikh reported that VTE rates did not reach zero even with a prolonged course of the low-molecular-weight heparin enoxaparin.
At 90 days, the symptomatic VTE rate was only 0.3% for total knee arthroplasty but reached 1.2% for total hip arthroplasty.
“At the time of this study we were using enoxaparin for 28 days following total hip replacements and for 14 days following total knee replacements,” Dr. Parikh reported. Since this study, his institution has switched to a regimen recommended by the U.K.’s National Institute for Health and Clinical Excellence (NICE).
Under the NICE guidelines, VTE prophylaxis for total hip arthroplasty is 40 mg enoxaparin once daily for 14 days followed by 75 mg aspirin for another 14 days, according to Dr. Parikh. For total knee arthroplasty, the standard regimen is 75 mg aspirin for 14 days.
For those who might not be best managed with the standard approach, “there is no clear guideline.” Rather, in patients with renal or liver impairment, “we discuss the case with the hematology team to adjust the doses,” Dr. Parikh reported.
The advantage of a standardized approach applied to all or most patients is that is eliminates disparities, but Dr. Parikh agreed that risk-adjusted prophylaxis might be warranted for optimal outcomes.
Dr. Wylie reported a financial relationship with Arthrex.