Is aspirin (acetylsalicylic acid) monotherapy recommended for Deep Vein Thrombosis (DVT) prophylaxis post hip replacement?

Aspirin Monotherapy for DVT Prophylaxis Post Hip Replacement

Aspirin monotherapy is an acceptable and effective option for DVT prophylaxis after hip replacement in standard-risk patients, though it remains controversial with divergent guideline recommendations.

Guideline Landscape: A Critical Divide

The evidence reveals a fundamental disagreement among major guideline bodies:

Guidelines Supporting Aspirin Use

• The American Academy of Orthopaedic Surgeons (AAOS) recommends aspirin as an acceptable sole prophylactic agent (Grade B recommendation), arguing that the direct link between asymptomatic DVT and clinically significant PE has not been proven, and therefore studies using venography endpoints are not clinically relevant 1
• The Scottish Intercollegiate Guidelines Network (SIGN) and Brazilian guidelines also endorse aspirin monotherapy (Grade A recommendations) 1
• These guidelines prioritize symptomatic outcomes (PE, mortality) over asymptomatic DVT rates detected by imaging 1

Guidelines Against Aspirin as Sole Agent

• The American College of Chest Physicians (ACCP) explicitly advises against aspirin as the sole method of thromboprophylaxis (Grade A recommendation), stating it is significantly less effective than other anticoagulant regimens 1, 2
• The French guidelines similarly recommend against aspirin monotherapy (Grade B) 1
• The ACCP position is that aspirin has never been evaluated in RCTs for preventing asymptomatic DVT detected by venography 1

High-Quality Research Evidence

The most recent and highest quality evidence supports aspirin's clinical effectiveness:

• A 2020 systematic review and meta-analysis in JAMA Internal Medicine (13 RCTs, 6,060 participants) found no statistically significant difference in VTE risk between aspirin and other anticoagulants after hip and knee replacement (RR 1.12,95% CI 0.78-1.62), with comparable rates of DVT, PE, major bleeding, and wound complications 3
• This meta-analysis showed aspirin was not inferior to LMWH (RR 0.76,95% CI 0.37-1.56) or rivaroxaban (RR 1.52,95% CI 0.56-4.12) 3
• A 2022 multicenter study in JBJS involving 1,141 hip fracture patients found aspirin was noninferior to more potent anticoagulation, with an overall VTE rate of 1.98% for aspirin versus 6.7% for other anticoagulants (p < 0.001) 4

Practical Clinical Algorithm

Patient Selection for Aspirin Monotherapy

Use aspirin (81-325 mg) for standard-risk patients defined as:

• No history of prior VTE 5
• No recent orthopedic surgery 5
• No known hypercoagulable state 5
• No cardiac arrhythmia requiring anticoagulation 5
• Not receiving anticoagulation for other medical conditions 5
• No contraindications (peptic ulcer disease, aspirin intolerance) 5

Avoid Aspirin Monotherapy in High-Risk Patients:

• Active cancer 6
• Prior VTE history 6
• Hypercoagulable states 6
• Prolonged immobility 6
• Specifically elevated PE risk 1, 6

Dosing Recommendations

Low-dose aspirin (81 mg twice daily) is preferred over standard-dose (325 mg):

• A 2023 study found 81 mg BID had significantly lower bleeding rates (2.5%) compared to 325 mg once daily (7.6%, p = 0.0029), with no difference in VTE rates (1.5% vs 2.7%, p = 0.41) 7
• A 2019 study of 3,936 patients found no difference in symptomatic VTE between 81 mg BID (0.6%) and 325 mg BID (1.0%, p = 0.35), with similar bleeding and mortality rates 5
• Duration: 4-6 weeks postoperatively 7, 5

Critical Caveats

The fundamental controversy centers on outcome prioritization:

• AAOS-aligned guidelines prioritize symptomatic outcomes (PE, death) and argue that asymptomatic DVT detected by venography lacks clinical relevance 1
• ACCP-aligned guidelines prioritize all VTE prevention (including asymptomatic DVT) and demonstrate aspirin's inferiority for this endpoint 1, 2

When anticoagulation is contraindicated or unavailable:

• Aspirin may be considered as a secondary option in non-orthopedic surgery 6
• Mechanical prophylaxis (intermittent pneumatic compression) should be added when bleeding risk is high 6

Extended prophylaxis context:

• One study found aspirin was noninferior to LMWH for extended VTE prophylaxis after initial 10 days of LMWH following total hip arthroplasty 1
• However, for secondary prevention after stopping anticoagulation, reduced-dose DOACs prevent 46 more VTE events per 1,000 cases compared to aspirin 2

Historical data from 1986 showed aspirin (250 mg/day) reduced phlebographic DVT from 30% to 3.3% (p < 0.01) compared to controls 8, though modern anticoagulants were not available for comparison at that time.