From the Guidelines

Aspirin can be used for Deep Vein Thrombosis (DVT) prophylaxis, but it is not a recommended alternative to anticoagulation.

Aspirin is less effective at preventing recurrent VTE than anticoagulants, with 53 fewer events per 1,000 cases (from 84 fewer to 13 fewer) compared to no aspirin 1
The use of aspirin for DVT prophylaxis should be considered in patients who are stopping anticoagulant therapy and do not have a contraindication to aspirin, with a weak recommendation and low-certainty evidence 1
The benefits of aspirin in preventing recurrent VTE must be balanced against its risk of bleeding and inconvenience, with 3 more events per 1,000 cases (from 6 fewer to 28 more) of major bleeding 1

Aspirin is not a reasonable alternative to anticoagulant therapy in patients who want extended therapy, due to its lower efficacy in preventing recurrent VTE 1
The decision to use aspirin for DVT prophylaxis should be individualized, taking into account the patient's risk of recurrent VTE, bleeding risk, and personal preferences 1

From the FDA Drug Label

The FDA drug label for aspirin (acetylsalicylic acid) does not directly support its use for Deep Vein Thrombosis (DVT) prophylaxis.
The label mentions that aspirin contains an NSAID, which may cause severe stomach bleeding and has an anticoagulant effect, but it does not provide information on its use for DVT prophylaxis.
The label does provide warnings and precautions for the use of aspirin, including stomach bleeding warning and allergy alert, but it does not address the specific question of DVT prophylaxis.
Therefore, based on the available information, aspirin should not be used for DVT prophylaxis without further guidance from a healthcare professional 2.

Aspirin has been studied as a potential prophylactic agent for deep vein thrombosis (DVT) in various patient populations, including those undergoing major orthopedic surgery or trauma patients 3, 4, 5, 6, 7.
The evidence suggests that aspirin may be effective in preventing DVT, although its efficacy may vary depending on the patient population, dosage, and comparison to other anticoagulants 3, 5, 7.
A study published in 2016 found that preinjury aspirin use was associated with a significant protective effect against DVT in trauma patients, with an odds ratio of 0.17 (95% confidence interval, 0.04-0.68; p = 0.012) 3.
Another study published in 2009 found that aspirin was efficacious in preventing VTE compared to placebo or no treatment, but appeared to be less efficacious than low molecular weight heparins in small trials 4.
A 1986 study found that aspirin was effective in preventing DVT in patients undergoing total hip replacement, with a significant reduction in phlebographic DVT compared to the control group 5.
A 2023 meta-analysis found that aspirin was less effective than oral anticoagulants in thromboprophylaxis after major orthopedic surgery, but had a lower risk of bleeding events 6.
A 2022 randomized controlled trial found that aspirin and rivaroxaban had comparable efficacy in preventing VTE after total knee arthroplasty, without increasing the incidence of wound complications and bleeding 7.

Aspirin has been compared to other anticoagulants, including low molecular weight heparins, rivaroxaban, and warfarin, in various studies 4, 6, 7.
The evidence suggests that aspirin may be less efficacious than some of these anticoagulants, but may have a lower risk of bleeding events 6.
The choice of anticoagulant for DVT prophylaxis may depend on various factors, including patient risk factors, surgical procedure, and individual patient characteristics.

The optimal dosage and administration of aspirin for DVT prophylaxis are not well established, and may vary depending on the patient population and comparison to other anticoagulants 3, 5, 7.
Studies have used various dosages of aspirin, ranging from 250 mg/day to 300 mg/day, and have administered it orally or as part of a combination regimen with other anticoagulants 3, 5, 7.