Preoperative Anticoagulation for Hip Fracture Patients
For elderly patients with hip fracture and no existing indication for anticoagulation, you should initiate pharmacologic VTE prophylaxis with low-molecular-weight heparin (LMWH) as soon as possible after admission, ideally before surgery if hemostasis is adequate, or immediately postoperatively if bleeding risk is concerning.
Recommended Anticoagulant Choice
LMWH is the preferred agent for VTE prophylaxis in hip fracture patients 1. The evidence strongly supports LMWH over unfractionated heparin (UFH) based on superior efficacy and safety:
- Lower rates of DVT and PE (P = 0.007 and P < 0.001 respectively)
- Fewer bleeding complications and transfusions (P < 0.001)
- Reduced mortality (P < 0.001) 1
Specific Dosing for Elderly Patients
For patients older than 65 years, start with enoxaparin 30 mg subcutaneously every 12 hours 1. If renal failure is present (CrCl < 30 mL/min), switch to UFH 5000 units every 8 hours 1.
Timing: Preoperative vs Postoperative Initiation
The evidence on preoperative versus postoperative initiation is nuanced:
- A large Norwegian study of 45,000 elderly hip fracture patients found that preoperative prophylaxis did not influence mortality or reoperation rates 1
- However, postoperative prophylaxis decreased intraoperative bleeding complications for operations with hip compression screws (but not for intramedullary nails) 1
Practical approach: Start LMWH preoperatively if the patient is hemodynamically stable without active bleeding or coagulopathy. If there are concerns about bleeding risk, solid organ injury, or traumatic brain injury, delay pharmacologic prophylaxis until after surgery and use mechanical prophylaxis (intermittent pneumatic compression) in the interim 1.
Alternative Agents
Fondaparinux
Fondaparinux is FDA-approved specifically for hip fracture surgery and showed significant VTE reduction in trials 2, 3. However, it has a longer half-life (approximately 17 hours) which complicates perioperative management 4.
Factor Xa Inhibitors (DOACs)
While increasingly used in real-world practice, factor Xa inhibitors showed higher PE rates compared to LMWH (AR 2 vs -3.5) in elderly hip fracture patients 1. Recent 2025-2026 data suggests comparable safety but this remains less established than LMWH 5, 6.
Unfractionated Heparin
UFH is acceptable but less effective than LMWH (RR 0.68 for DVT prevention) and more difficult to manage 7, 1.
Mechanical Prophylaxis
Combine pharmacologic prophylaxis with intermittent pneumatic compression (IPC) for optimal VTE prevention 7, 8. The combination reduces DVT risk more effectively than either alone (RR 0.34) 1.
Use mechanical prophylaxis alone only when pharmacologic agents are contraindicated due to:
- Active bleeding
- Coagulopathy
- Hemodynamic instability
- Severe traumatic brain injury
- Spinal trauma requiring stabilization 1
Duration of Prophylaxis
Minimum 10-14 days of thromboprophylaxis is mandatory 7, 8, 9. For high-risk patients (age > 75, prior VTE, prolonged immobility), extend prophylaxis to 4-5 weeks 7, 8, 10, 9, 2.
Critical Pitfalls to Avoid
Do NOT use aspirin alone as VTE prophylaxis—it is ineffective (Grade 1A recommendation) 7, 8, 2
Do NOT delay surgery waiting for "prophylactic" anticoagulation to start—surgery within 24-48 hours reduces mortality and morbidity more than any prophylaxis regimen 1, 11, 12, 13
Do NOT withhold LMWH solely due to planned neuraxial anesthesia—if timing conflicts exist, use general anesthesia with peripheral nerve blocks rather than delaying surgery 11, 12, 13
Do NOT forget to restart prophylaxis postoperatively—failure to resume anticoagulation exposes patients to high VTE risk during the critical postoperative period 7, 8
Risk Stratification Context
Hip fracture patients are automatically high-risk for VTE (5 points on Caprini score) 8. Age ≥65 adds 2 additional points on the TESS score, and lower extremity fracture adds 2 more points 1. These patients require prophylaxis unless specific contraindications exist.