Aspirin for Thromboprophylaxis after Fracture
- Aspirin for thromboprophylaxis to prevent venous thromboembolism after hip- or knee-replacement surgery has been included in clinical guidelines. Although the use of aspirin thromboprophylaxis for venous thromboembolism in hip and knee replacements is still in debate, data on its use in patients with extremity fracture (in the hip to midfoot or shoulder to wrist) are limited.
Interpret with Caution
The PREVENT CLOT trial aimed to test the noninferiority of aspirin compared to low-molecular-weight heparin for thromboprophylaxis in patients after an extremity fracture. The use of aspirin for thromboprophylaxis in patients with extremity fracture is limited, and the trial included patients with different levels of risk of venous thromboembolism and upper extremity fracture. The trial population was young, with a mean age of 22.7±11.6 years, and at low risk for venous thromboembolism. However, the authors’ conclusion that aspirin was noninferior to low-molecular-weight heparin should be interpreted with caution due to concerns regarding selection bias. The trial involved hospitalized patients, for some of whom mechanical prophylaxis is not feasible. The incidence of bleeding events was high with either thromboprophylaxis strategy, with events occurring at a median of 7 days. Deep-vein thrombosis is a costly and disabling condition that can lead to post-thrombotic syndrome and reduced quality of life. Short-term use of low-molecular-weight heparin is recommended for hospitalized patients with major fracture, despite the additional costs and patient discomfort.
Risk of DVT Understated
Aspirin was found to be noninferior to low-molecular-weight heparin in preventing all-cause mortality in patients with major traumatic fracture. However, the risk of deep-vein thrombosis was understated, with a higher incidence in the aspirin group compared to the low-molecular-weight heparin group. Clots below the knee are less clinically important than proximal deep-vein thrombosis, which had a between-group difference of 0.9 percentage points. Clinicians and patients can use the data for shared decision making, weighing the lower cost of aspirin over low-molecular-weight heparin against a small increased risk of deep-vein thrombosis below the knee.
Population Heterogeneity
The trial had no upper age limit, and at least one quarter of the participants were 60 years of age or older. There was no significant heterogeneity in treatment effect according to patient age or baseline risk of venous thromboembolism. Allowing older patients with a hip fracture to bear weight at discharge does not decrease the generalizability of the findings. Bleeding events were defined differently in previous studies, which may explain the contrast in incidence of bleeding events in the trial.
Future Studies
Future studies may be necessary to evaluate not only the preferred thromboprophylaxis strategy but also a safe time frame for the initiation of pharmacologic thromboprophylaxis in patients with trauma. A cost-utility analysis may provide useful data on the effect of these interventions on population-level costs and benefits.