Baltimore, MD—Thromboprophylaxis with aspirin was noninferior to LMWH in preventing death in patients with extremity fractures that had been treated operatively or with any pelvic or acetabular fracture, according to a new study.

The use of aspirin also was associated with low incidences of deep-vein thrombosis and pulmonary embolism and low 90-day mortality, according to the Patient-Centered Outcomes Research Institute’s PREVENT CLOT trial authors. The results, which could be practice-changing, were published in The New England Journal of Medicine.

The researchers added that while clinical guidelines recommend LMWH for thromboprophylaxis in patients with fractures, few trials of its effectiveness compared with aspirin have been conducted.

We expect our findings from this large-scale trial to have an important impact on clinical practice, and potentially even change the standard of care,” the study’s principal investigator Robert V. O’Toole, MD, said in a University of Maryland press release. “Orthopaedic trauma patients are commonly prescribed the blood thinner low-molecular-weight heparin to prevent blood clots for weeks following surgery. Not only does the medication need to be injected, it can also be quite expensive compared to aspirin.”

The pragmatic, multicenter, randomized, noninferiority trial, enrolled 12,211 adult patients who had a fracture of an extremity (anywhere from hip, to midfoot or shoulder, to wrist) that had been treated operatively or who had any pelvic or acetabular fracture.

The participants were randomly assigned to receive LMWH (enoxaparin) at a dose of 30 mg twice daily or aspirin at a dose of 81 mg twice daily while hospitalized. After hospital discharge, the patients continued to receive thromboprophylaxis according to the clinical protocols of each hospital.

The primary outcome was defined as death from any cause at 90 days. Secondary outcomes included nonfatal pulmonary embolism, deep-vein thrombosis, and bleeding complications.

With 6,101 of the patients randomly assigned to receive aspirin, 6,110 were given LMWH. Patients had a mean age of 44.6 years, 0.7% had a history of venous thromboembolism, and 2.5% had a history of cancer. A mean of 8.8±10.6 in-hospital thromboprophylaxis doses was prescribed, with a median 21-day supply of thromboprophylaxis at discharge.

“Death occurred in 47 patients (0.78%) in the aspirin group and in 45 patients (0.73%) in the low-molecular-weight–heparin group (difference, 0.05 percentage points; 96.2% confidence interval, –0.27 to 0.38; P <.001 for a noninferiority margin of 0.75 percentage points),” the study reports. “Deep-vein thrombosis occurred in 2.51% of patients in the aspirin group and 1.71% in the low-molecular-weight–heparin group (difference, 0.80 percentage points; 95% CI, 0.28 to 1.31). The incidence of pulmonary embolism (1.49% in each group), bleeding complications, and other serious adverse events were similar in the two groups.”

Background information in the article pointed out that venous thromboembolism is a well-recognized, potentially fatal complication after orthopedic trauma. The authors recounted how findings from recent trials and meta-analyses raise the possibility that aspirin could be an effective thromboprophylaxis alternative to LMWH in patients who have undergone total joint arthroplasty and offer a more favorable safety profile. “However, evidence from head-to-head comparisons among patients with fractures that have been treated operatively is limited,” they added. “Patients with fractures have shown a strong preference for aspirin if clinical outcomes are similar among thromboprophylaxis options, given the lower cost of aspirin and its oral administration (as compared with subcutaneous injection of low-molecular-weight heparin).”

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