What is the best approach for preventing pulmonary embolism in an older adult with a recent hip fracture or severe osteoarthritis undergoing partial hip arthroplasty, potentially with comorbidities such as dementia and impaired renal function?

VTE Prophylaxis for Hip Fracture/Arthroplasty in Older Adults

All older adults undergoing hip fracture surgery or hip arthroplasty should receive pharmacological VTE prophylaxis, with LMWH (enoxaparin 30 mg subcutaneously every 12 hours) as the preferred agent, combined with mechanical prophylaxis, and continued for up to 35 days total duration. 1, 2

Strength of Recommendation

The 2022 AAOS guidelines provide a strong recommendation for VTE prophylaxis in hip fracture patients, upgraded from moderate in 2014 based on consensus expert opinion despite moderate-quality evidence. 1 This reflects the clinical reality that VTE rates in hip fracture patients reach 12-37% without extended prophylaxis, making prevention essential despite the bleeding risks. 2

Pharmacological Agent Selection

First-Line: Low Molecular Weight Heparin (LMWH)

• LMWH is superior to unfractionated heparin in elderly trauma patients, demonstrating lower incidence of DVT and PE, fewer bleeding complications and transfusions, and reduced mortality. 2
• Enoxaparin 30 mg subcutaneously every 12 hours is the preferred dosing regimen for elderly patients. 2
• Dose adjustment according to anti-Xa levels and weight is warranted in this population. 2

Alternative: Fondaparinux

• Fondaparinux is FDA-approved for DVT prophylaxis following hip fracture, hip replacement, and knee replacement surgery. 3
• This agent may be particularly useful in patients with heparin-induced thrombocytopenia history. 3

Renal Impairment Considerations

Critical caveat: In patients with renal failure (like the case example with creatinine 1.42 mg/dL), switch from LMWH to unfractionated heparin 5000 units every 8 hours to avoid drug accumulation. 2 This is essential as LMWH is renally cleared and accumulation increases bleeding risk substantially.

Aspirin as Alternative

• Recent evidence suggests aspirin may be effective in standard-risk ambulatory patients with femoral neck fracture undergoing arthroplasty, with VTE rates of 1.98% versus 6.7% with other anticoagulants. 4
• However, given the strong guideline recommendations for more potent prophylaxis and the high-risk nature of this population (age >75, hip fracture, surgery, immobility), aspirin should be reserved for patients with contraindications to anticoagulation. 1, 2

Mechanical Prophylaxis: Essential Adjunct

Combined mechanical and pharmacological prophylaxis reduces DVT risk by 66% (RR 0.34), compared to 45% reduction with mechanical alone (RR 0.55). 2

• Options include intermittent pneumatic compression devices, graduated compression stockings, and early mobilization. 2
• Mechanical prophylaxis should be initiated immediately and continued throughout hospitalization. 5
• Common pitfall: Compliance with mechanical devices remains problematic due to skin abrasion and patient discomfort, requiring vigilant nursing oversight. 5

Duration of Prophylaxis

Standard Hip Fracture Surgery

• 5-9 days peri-operative period for most fracture surgeries. 2

Extended Prophylaxis for Hip Fracture

• Up to 24 additional days beyond the peri-operative period (total 32-35 days) is recommended for hip fracture patients. 2
• The case examples in the 2022 AAOS guidelines specifically mention "VTE prophylaxis for 1 month was provided." 1

This extended duration is critical as the thrombotic risk persists well beyond hospital discharge given continued immobility and the hypercoagulable state following major orthopedic surgery. 1

Special Population Considerations

Patients with Dementia

• The interdisciplinary care approach is strongly recommended for all hip fracture patients, with particularly strong evidence for those with mild-to-moderate dementia. 1
• VTE prophylaxis protocols remain unchanged regardless of cognitive status. 6

Patients on Anticoagulation for Other Indications

• In the case example of a patient on apixaban for atrial fibrillation, apixaban was restarted on postoperative day 2 for dual indication (VTE prophylaxis and atrial fibrillation). 1
• This approach avoids polypharmacy while addressing both thrombotic risks. 1

Body Weight <50 kg

• Increased bleeding risk requires careful monitoring, though prophylaxis should not be withheld. 3

Monitoring and Safety

• Thrombocytopenia monitoring is essential, particularly with heparin products. 3
• Pharmacological prophylaxis reduces DVT risk by 52% overall (RR 0.48), with LMWH providing an additional 32% reduction over UFH (RR 0.68). 2
• Important limitation: Neither mechanical nor pharmacological prophylaxis has been shown to significantly reduce PE rates in meta-analyses, though they reduce DVT which is the precursor. 2

Risk Stratification Context

This population carries multiple cumulative risk factors: 1, 2

• Age >75 years (independent risk factor)
• Lower extremity fracture (2-point risk score)
• Major orthopedic surgery
• Prolonged immobility
• Potential comorbidities (dementia, renal impairment, osteoarthritis)

The cumulative nature of these risks mandates aggressive prophylaxis despite bleeding concerns. 1