From the Guidelines

Aspirin can be used for Deep Vein Thrombosis (DVT) prophylaxis, but it is not the preferred choice.

Aspirin is less effective than anticoagulants in preventing recurrent VTE, with a reduction of about one-third compared to more than 80% with extended anticoagulant therapy 1.
The use of aspirin for DVT prophylaxis is generally recommended only for patients who are stopping anticoagulant therapy and do not have a contraindication to aspirin, as the benefits of aspirin must be balanced against its risk of bleeding and inconvenience 1.
A study comparing aspirin with placebo for the prevention of recurrent VTE in patients with a first unprovoked proximal DVT or PE found that aspirin reduced the risk of recurrent VTE by 53 fewer events per 1,000 cases, but increased the risk of major bleeding by 3 more events per 1,000 cases 1.
The Pulmonary Embolism Prevention (PEP) trial demonstrated that aspirin is effective in preventing VTE after major orthopedic surgery, with a 36% reduction in symptomatic DVT or pulmonary embolism 1.

The decision to use aspirin for DVT prophylaxis should be made on a case-by-case basis, taking into account the individual patient's risk factors and medical history.
Aspirin should not be considered a replacement for anticoagulant therapy in patients who are at high risk of recurrent VTE.
The dose and duration of aspirin therapy for DVT prophylaxis are not well established, but doses ranging from 50-150 mg/d have been used in clinical trials 1.

From the Research

Aspirin has been studied as a potential prophylaxis for venous thromboembolism (VTE), which includes DVT and pulmonary embolism (PE) 2, 3, 4, 5, 6.
The efficacy of aspirin in preventing VTE after total knee arthroplasty (TKA) and total hip arthroplasty (THA) has been compared to other anticoagulants, such as rivaroxaban and warfarin 3, 4, 5.
Studies have shown that aspirin is associated with a reduced risk of VTE compared to placebo 4, and is as effective as rivaroxaban for primary thromboprophylaxis post-THA and TKA 5.
The optimal dose of aspirin for VTE prophylaxis is still unclear, with some studies suggesting that low-dose aspirin (81 mg twice daily) is as effective as regular-dose aspirin (325 mg twice daily) 2, 6.
Aspirin has been found to have a similar safety profile to other anticoagulants, with no significant differences in major bleeding, mortality, or wound-related events 3, 4, 5, 6.

Aspirin has been compared to direct oral anticoagulants (DOACs) such as rivaroxaban, and has been found to be as effective in preventing VTE after TKA and THA 5.
A meta-analysis of randomized controlled trials found that aspirin was less effective than oral anticoagulants in thromboprophylaxis after major orthopedic surgery, but had a lower risk of bleeding 3.
Another study found that aspirin was associated with a non-significantly reduced risk of VTE compared to other thromboprophylactic methods, but had a similar safety profile 4.

Aspirin has been found to be safe and effective for VTE prophylaxis after TKA and THA, with a low risk of major bleeding and mortality 2, 4, 5, 6.
The risk of bleeding with aspirin is similar to that of other anticoagulants, and is lower than that of warfarin 3, 4.
Aspirin has been found to be effective in preventing symptomatic DVT and PE after TKA and THA, with a similar efficacy to other anticoagulants 4, 5.