Does low-dose aspirin use influence rates of pseudoarthrosis after posterior and transforaminal lumbar interbody fusion? A propensity-matched study

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAID) are common medications often avoided by spine surgeons for their perceived negative effects on arthrodesis. Aspirin is a unique NSAID with distinct pharmacological properties compared to other NSAIDs. At lower doses, aspirin induces more potent inhibition of COX-1 versus COX-2, decreasing osteoclastic activity and upregulating osteogenic pathways in animal models. Aspirin's role in spinal fusion outcomes is unclear. This study aimed to evaluate the relationship between aspirin 81 mg daily use and pseudoarthrosis after single-level PLIF or TLIF surgery. METHODS: This is a retrospective cohort study utilizing TriNetX, a large research platform including 71 participating healthcare organizations, to identify patient cohorts who underwent single-level PLIF or TLIF surgery. Patients were stratified by no aspirin and aspirin 81 mg daily use, defined by documented medication use within 3 months prior to and following surgery. The primary outcome was diagnosis of pseudoarthrosis. Propensity score matching (1:1 ratio) was performed for relevant demographic and clinical variables including those utilized in frailty indices, followed by risk analyses to determine odds of outcome at 6-months, 1-year, 2-years, 3-years, and 5-years. Additionally, odds of reoperation within 5 years and 30-day complication and hospital utilization rates were assessed. RESULTS: For patients who underwent single-level PLIF or TLIF, there were significantly lower rates of reported pseudoarthrosis in the aspirin 81 mg (n = 2,936) group at all timepoints, but there were no differences in reoperation rates at any timepoint. There were no significant differences in 30-day wound healing complications, surgical site infections, post-operative hematoma, transfusions, ED visits, and readmissions. CONCLUSIONS: Patients taking daily 81 mg aspirin who underwent single-level PLIF or TLIF did not demonstrate higher rates of pseudoarthrosis. There were no differences in reoperation and 30-day complications and hospital utilization. Changes to clinical practice are not recommended until prospective studies are completed.