DVT Prophylaxis in Non-Operatively Managed Lower Extremity Fractures
Pharmacological DVT prophylaxis with LMWH should be used in patients with non-operatively managed lower extremity fractures who have additional risk factors (age >60, previous VTE, active malignancy, immobility >3 days, or critical illness), while isolated fractures in low-risk patients may be managed with mechanical prophylaxis or early mobilization alone. 1, 2
Risk Stratification Framework
The decision to initiate prophylaxis hinges on identifying high-risk features rather than treating all lower extremity fractures uniformly:
High-Risk Patients Requiring Pharmacological Prophylaxis:
- History of previous VTE (OR 6.08 for recurrent VTE) 1
- Active malignancy (OR 2.65 for VTE) 1
- Age >60-65 years (OR 1.34 for VTE) 1
- Immobility or non-weight bearing status expected >3 days 1
- Known thrombophilia (OR 5.88 for VTE) 1
- Critical illness or ICU-level care (OR 1.65 for VTE) 1
- Multiple trauma or polytrauma 3, 4
Lower-Risk Patients (Mechanical Prophylaxis May Suffice):
- Isolated lower extremity fracture without additional risk factors 1
- Young patients (<60 years) with no VTE history 1, 2
- Expected early mobilization within 48-72 hours 2, 5
Evidence Supporting Prophylaxis in Lower Extremity Fractures
Meta-analysis data demonstrate that LMWH reduces VTE rates from 17.1% to 9.6% in patients with lower extremity immobilization, without significantly increasing bleeding risk 1. A Cochrane review found VTE incidence ranging from 4.3% to 40% in patients with leg injuries immobilized for ≥1 week who received no prophylaxis, compared to 0-37% with LMWH (odds ratio 0.49) 1.
The incidence of DVT after isolated lower extremity fractures ranges from 5% to 86% depending on fracture location, with femur fractures carrying the highest risk and more distal fractures showing progressively lower rates 4. Importantly, DVT can occur in both the injured and uninjured leg 4.
Recommended Prophylaxis Regimens
Pharmacological Options (Preferred for High-Risk Patients):
- Enoxaparin 40 mg subcutaneously once daily 2, 5
- Dalteparin 5000 IU subcutaneously once daily 5
- Fondaparinux 2.5 mg subcutaneously once daily 5
- Unfractionated heparin 5000 units subcutaneously twice or three times daily 5
LMWH is preferred over unfractionated heparin due to higher effectiveness in preventing DVT (RR 0.68) 2, 5, 6.
Mechanical Prophylaxis (For Bleeding Risk or Low-Risk Patients):
- Graduated compression stockings (30-40 mm Hg knee-high) 2, 5
- Intermittent pneumatic compression devices 2, 5, 7
- Foot pumps (particularly useful when lower extremity injury precludes sequential compression devices) 7
Combined Approach: The combination of mechanical and pharmacological prophylaxis is superior to either modality alone (RR 0.34 for DVT) and should be used in very high-risk patients 2, 5.
Duration of Prophylaxis
Continue prophylaxis throughout the period of immobilization or non-weight bearing status 1, 5. For patients with plaster cast immobilization, prophylaxis should continue for the entire duration of casting if additional risk factors are present 1. Standard duration is typically 7-10 days, but may extend up to 4 weeks for patients with persistent immobility or multiple risk factors 5.
Special Populations and Dose Adjustments
Renal Impairment:
- CrCl 30-50 mL/min: Reduce fondaparinux to 1.5 mg once daily 5
- CrCl <30 mL/min: Reduce enoxaparin to 30 mg once daily or use unfractionated heparin 5000 U every 8 hours 2, 5
Obesity:
- Patients >150 kg: Consider increasing enoxaparin to 40 mg subcutaneously every 12 hours 5
Elderly Patients (>65 years):
- Initial enoxaparin dose should be 30 mg every 12 hours 2
Critical Pitfalls to Avoid
Do not assume all lower extremity fractures require the same prophylaxis intensity. The American Society of Hematology guidelines specifically recommend against routine prophylaxis in medical outpatients with minor provoking factors (including minor injury) unless additional high-risk features are present 1. This conditional recommendation reflects that undesirable consequences may outweigh benefits in truly low-risk patients.
Do not overlook DVT risk in patients with "minor" fractures who have additional risk factors. Even ankle or foot fractures warrant prophylaxis if the patient has previous VTE history, active cancer, or prolonged immobility 1, 2.
Do not use aspirin as sole prophylaxis. Aspirin is not recommended as the sole method of thromboprophylaxis for lower extremity fractures, despite causing less bleeding 2. Antiplatelet drugs are ineffective for VTE prophylaxis because venous thrombosis is driven by stasis and hypercoagulability rather than platelet activation 8.
Do not delay initiation of prophylaxis. Pharmacological prophylaxis should begin immediately upon recognition of risk factors if no contraindications exist 5. Delay from injury to treatment initiation is itself a surgeon-modifiable risk factor for DVT 4.
Do not forget mechanical prophylaxis when pharmacological agents are contraindicated. For patients with active bleeding, severe thrombocytopenia, or recent neurosurgery, immediately apply mechanical prophylaxis rather than withholding all prophylaxis 5.
Contraindications to Pharmacological Prophylaxis
Absolute contraindications include:
- Active coagulopathy with INR >1.5 or platelet count <50 × 10⁹/L 5
- Active bleeding or recent major bleeding within 3 months 1, 5
- Active gastroduodenal ulceration 1
In these situations, use mechanical prophylaxis until bleeding risk decreases 2, 5.
Implementation Gap
Despite high-quality evidence, only 58.5% of at-risk surgical patients and 39.5% of at-risk medical patients receive appropriate VTE prophylaxis 5. This represents a significant quality gap that must be addressed through systematic risk assessment and protocol-driven prophylaxis initiation.