Selection Bias, Orthopaedic Style: Knowing What We Don't Know About Aspirin

Risk-Stratified Venous Thromboembolism Chemoprophylaxis After Total Joint Arthroplasty: Evaluation of an Institutional Approach

Background/Objectives: The optimal venous thromboembolism (VTE) chemoprophylaxis approach after hip or knee total joint arthroplasty (TJA) remains controversial. This study aimed to characterize antithrombotic-related complications associated with various chemoprophylaxis regimens after TJA and to assess our current institutional risk-stratified prescribing tool. Methods: This retrospective case-control study and regression analysis included elective unilateral TJA patients at a single institution between 1 July 2015 and 31 December 2021. The primary outcome was a composite of antithrombotic-related complications within 30 days of surgery, including thrombotic and hemorrhagic/wound-related adverse events. The duration of anticoagulant chemoprophylaxis prescribed prior to aspirin monotherapy (0-28 days) was compared between patients who did vs. did not experience a complication, with stratification by institutionally defined VTE risk categories (Routine, Moderate, or High Risk). The complication rate was then assessed as a function of anticoagulant duration within each risk subgroup. Results: The study included 5420 patients, with 279 (5.2%) experiencing ≥1 complication. Routine VTE risk patients experienced few complications, with no significant difference between aspirin monotherapy and various initial anticoagulant durations (p = 0.6118). Moderate and High VTE Risk patients saw significantly lower complication rates with initial anticoagulant prophylaxis of increasing durations (p = 0.0090 and p = 0.0050), with a significant overall effect of VTE Risk strata observed (p = 0.0006). Conclusions: When both bleeding and thrombotic events are considered, anticoagulant-to-aspirin regimens were associated with lower complication rates than aspirin monotherapy in higher risk patients, while routine patients saw no significant benefit over aspirin. Our risk-stratified prescribing approach should be prospectively evaluated.

Comparison of efficacy and safety between aspirin and oral anticoagulants for venous thromboembolism prophylaxis after major orthopaedic surgery: a meta-analysis of randomized clinical trials

Background: venous thromboembolism (VTE) is one of the most common complications after major orthopaedic surgery. Recent studies have suggested that aspirin may also be effective in preventing VTE, but it is still controversial whether it can be routinely used. Objectives: To compare the efficacy and safety of aspirin against oral anticoagulants in the prevention of VTE following total hip arthroplasty (THA), total knee arthroplasty (TKA) or hip fracture surgery (HFS). Methods: Relevant publications have been obtained using electronic search databases such as PubMed, Embase, Web of Science, Cochrane Library, and Clinical Trials. gov. from inception to 20 July 2023. Only RCTs evaluating the efficacy and safety of aspirin compared with oral anticoagulants undergoing major orthopaedic surgery were included in the meta-analysis. The primary outcome reported was any VTE event (including deep vein thrombosis (DVT) and pulmonary embolism (PE)). Secondary outcomes included mortality, major bleeding (including gastrointestinal bleed, cerebrovascular hemorrhage, or any bleeding requiring a return to the theater), minor bleeding (ecchymosis, epistaxis, hematuria), and wound complications. The risk of bias for all included studies was assessed according to the Cochrane Collaboration's tool. Results: After screening 974 studies, 12 randomized clinical trials (RCTs) were included, involving 5,088 participants, including 2,540 participants in aspirin, 2,205 participants in rivaroxaban, and 323 participants in warfarin. Aspirin was found to be less effective than oral anticoagulants in thromboprophylaxis after major orthopedic surgery (RR = 1.206, 95% CI 1.053-1.383). After subgroup analysis according to the type of oral anticoagulant, the results showed that aspirin was similar to rivaroxaban and inferior to warfarin. Considering that the studies in the warfarin group were all conducted before 2000, our results need to be further confirmed. In addition, the aspirin group had a higher risk of VTE than the control group in other subgroups, including a follow-up time of ≤3 months, type of procedure as TKA, high-dose aspirin (≥650 mg qd), and no combined use of mechanical prophylaxis. In terms of safety events, aspirin did not show significant differences in major bleeding (RR = 0.952, 95% CI 0.499-1.815), all-cause mortality (RR = 1.208, 95% CI 0.459-3.177), and wound-related events (RR = 0.618, 95% CI 0.333-1.145) compared with oral anticoagulants, and aspirin was associated with a reduction in the risk of minor bleeding (RR = 0.685, 95% CI 0.552-0.850) events and total bleeding (RR = 0.726, 95% CI 0.590-0.892). Conclusion: Aspirin reduces bleeding risk after major orthopedic surgery compared with oral anticoagulants, but may sacrifice VTE prevention to some extent. Updated evidence is needed to analyze the thromboprophylaxis effects of aspirin in patients undergoing major orthopedic surgery. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=463481, identifier CRD42023463481.

Venous thromboembolism in orthopedic surgery: Global guidelines

Venous thromboembolism (VTE) is a severe complication that can occur after major orthopedic procedures. As VTE-related morbidity and mortality are a significant concern for both medical professionals and patients, and preventative measures are typically employed. Multiple organizations, including the American College of Chest Physicians (ACCP) and the American Academy of Orthopedic Surgeons (AAOS), have developed guidelines for VTE prophylaxis specifically in patients undergoing joint replacement procedures. However, recently, the International Consensus Meeting (ICM) was convened, which brought together over 600 experts from 68 countries and 135 international societies. These experts, spanning a range of medical disciplines including orthopedic surgery, anesthesia, cardiology, hematology, vascular, and internal medicine, conducted a comprehensive review of the literature using a strict Delphi process to generate practical recommendations for VTE prophylaxis across all types of orthopedic procedures. This review article summarizes some of the recommendations of the ICM.

Aspirin for Venous Thromboembolic Prophylaxis Following Total Hip and Total Knee Arthroplasty: An Analysis of Safety and Efficacy Accounting for Surgeon Selection Bias

BACKGROUND

Aspirin may be effective at preventing venous thromboembolism following total knee arthroplasty (TKA) or total hip arthroplasty (THA). Current evidence is limited by bias as many surgeons who use aspirin prescribe for high-risk patients alternative chemoprophylactic agents. Therefore, this study aimed to evaluate the risk of pulmonary embolism (PE) and deep vein thrombosis (DVT) in patients who received aspirin and warfarin while accounting for surgeon selection bias.

METHODS

A national database was queried for patients undergoing primary elective TKA or THA from 2015 to 2020. Patients whose surgeon used aspirin in >90% of their patients were compared to patients whose surgeon used warfarin in >90% of cases. Instrumental variable analyses were performed to assess for PE, DVT, and transfusion while accounting for selection bias. Among TKA patients, 26,657 (18.8%) were in the warfarin cohort and 115,005 (81.2%) were in the aspirin cohort. Among THA patients, 13,035 (17.7%) were in the warfarin cohort and 60,726 (82.3%) were in the aspirin cohort.

RESULTS

Analyses were unable to identify a difference in the risk of PE (TKA: adjusted odds ratio [aOR]: 0.98, P = .659; THA: aOR = 0.93, P = .310) and DVT (TKA: aOR = 1.05, P = .188; THA: aOR = 0.96, P = .493) between the aspirin and warfarin cohorts. However, the aspirin cohort was associated with a lower risk of transfusion (TKA: aOR = 0.58, P < .001, THA: 0.84, P < .001).

DISCUSSION

After accounting for surgeon selection bias, aspirin was as effective as warfarin at preventing PE and DVT following TKA and THA. Furthermore, aspirin was associated with a lower risk of transfusion compared to warfarin.

Aspirin Thromboprophylaxis Is Associated With Less Major Bleeding Events Following Total Joint Arthroplasty

BACKGROUND

There is ongoing debate on what is optimal prophylactic agent to reduce venous thromboembolism (VTE) following total joint arthroplasty (TJA). Although many studies assess the efficacy of these agents in VTE prevention, no attention is given to their adverse effect on major bleeding events (MBEs). This study compared the incidence of MBE in patients receiving aspirin as VTE prophylaxis vs other chemoprophylaxis.

METHODS

A single-institution, retrospective study of 35,860 patients undergoing TJA between 2009 and 2020 was conducted. Demographic variables, co-morbidities, type of chemoprophylaxis, and intraoperative factors were collected. MBE was defined using the 2010 criteria for major bleeding in surgical patients presented by the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis. To enhance capture rate, comprehensive queries utilizing MBE keywords were conducted in clinical notes, physician dictations, and phone call logs. Univariate followed by multivariate regression was performed as well as propensity score matched analysis.

RESULTS

Overall, 270 patients (0.75%) in this cohort developed MBE. The MBE rate was 0.5% in the aspirin group and 1.2% in the non-aspirin group. After adjusting for confounders, multiple logistic regression and propensity score matched analysis revealed almost 2 times lower odds of MBE in patients who received aspirin. Variables independently associated with increased MBE risk included increasing age, body mass index, American Society of Anesthesiologists score, revision surgery, peptic ulcer disease, coagulopathy, intraoperative blood transfusion, and active smoking.

CONCLUSION

Administration of aspirin for VTE prophylaxis, compared to other chemoprophylaxis agents may have an association with lower risk of major bleeding following TJA. Future randomized controlled trials should examine these findings.

Venous Thromboembolic Prophylaxis After Total Hip and Knee Arthroplasty

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The selection of an agent for prophylaxis against venous thromboembolism (VTE) is a balance between efficacy and safety. The goal is to prevent symptomatic VTE while limiting the risk of bleeding.

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The optimal agent for VTE prophylaxis has not been identified. The American College of Chest Physicians guidelines recommend that, after total hip or total knee arthroplasty, patients receive at least 10 to 14 days of 1 of the following prophylaxis agents: aspirin, adjusted-dose vitamin K antagonist, apixaban, dabigatran, fondaparinux, low-molecular-weight heparin, low-dose unfractionated heparin, rivaroxaban, or portable home mechanical compression.

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The use of aspirin for VTE prophylaxis has increased in popularity over the past decade because it is effective, and it is an oral agent that does not require monitoring. The true efficacy of aspirin needs to be determined in multicenter randomized clinical trials.

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Validated risk stratification protocols are essential to identify the safest and most effective regimen for VTE prophylaxis for individual patients. There is no consensus regarding the optimal method for risk stratification; the selection of a prophylaxis agent should be determined by shared decision-making with the patient to balance the risk of thrombosis versus bleeding.

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Patients with atrial fibrillation being treated with chronic warfarin therapy or direct oral anticoagulants should stop the agent 3 to 5 days prior to surgery. Patients do not typically require bridging therapy prior to surgery.

Non-Inferiority of Aspirin for Venous Thromboembolism Prophylaxis After Hip Arthroplasty in a Statewide Registry

BACKGROUND

Uncertainty remains surrounding the use of aspirin as a sole chemoprophylactic agent to reduce the risk of venous thromboembolism (deep vein thrombosis or pulmonary embolism) and bleeding after primary total hip arthroplasty.

METHODS

We performed a non-inferiority analysis of a retrospective cohort of patients undergoing total hip arthroplasty from April 1, 2013 to December 31, 2018. Cases were retrieved from the Michigan Arthroplasty Registry Collaborative Quality Initiative database and performed by 355 surgeons at 61 hospitals throughout Michigan. Surgical setting ranged from small community hospitals to large academic and non-academic centers. The primary outcomes were post-operative venous thromboembolism event or death and bleeding event.

RESULTS

Of the 59,747 patients included, 32,878 (55.03%) were female, and the mean age was 64.5. A total of 462 (0.77%) composite venous thromboembolism events occurred. There were 221 (0.71%) and 129 (0.80%) venous thromboembolism events in patients receiving aspirin only and anticoagulants only, respectively. Aspirin was non-inferior to anticoagulants for composite venous thromboembolism events (odds ratio 0.99, 95% confidence interval 0.79-1.26, P < .001). Bleeding events occurred in 767 (1.28%) patients, with 304 (0.97%) and 281 (1.74%) bleeding events in patients receiving aspirin only and anticoagulants only, respectively. Aspirin was non-inferior to anticoagulants for bleeding events (odds ratio 0.62, 95% confidence interval 0.52-0.74, P < .001).

CONCLUSION

Aspirin is not inferior to other anticoagulants as pharmacologic venous thromboembolism prophylaxis with regards to post-operative risk of venous thromboembolism or bleeding. Sole use of aspirin for venous thromboembolism prophylaxis after total hip arthroplasty should be considered in the appropriate patient.

Does aspirin prevent venous thromboembolism?

Venous thromboembolism (VTE; deep vein thrombosis and/or pulmonary embolism) is a well-established cause of morbidity and mortality in the medical and surgical patient populations. Clinical research in the prevention and treatment of VTE has been a dynamic field of study, with investigations into various treatment modalities ranging from mechanical prophylaxis to the direct oral anticoagulants. Aspirin has long been an inexpensive cornerstone of arterial vascular disease therapy, but its role in the primary or secondary prophylaxis of VTE has been debated. Risk-benefit tradeoffs between aspirin and anticoagulants have changed, in part due to advances in surgical technique and postoperative care, and in part due to the development of safe, easy-to-use oral anticoagulants. We review the proposed mechanisms in which aspirin may act on venous thrombosis, the evidence for aspirin use in the primary and secondary prophylaxis of VTE, and the risk of bleeding with aspirin as compared with anticoagulation.