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Purpose. To quantify the risk of clinically overt venous thromboembolism (VTE) and major bleeding (MB) during the first year following surgery for lumbar spinal stenosis (LSS) relative to a matched population cohort.

Methods: This nationwide, retrospective cohort study utilized data from the Swedish National Spine Register (Swespine), including 77,145 patients who underwent surgical treatment for LSS between 2003 and 2023. These patients were matched 1:5 to 385,388 referents from the general population. Outcomes (VTE and MB) were identified through cross-linkage with the National Patient Register (NPR) and the Swedish Stroke Register (Riksstroke). Adjusted Cox piecewise regression models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for VTE and MB across prespecified postoperative intervals.

Results: Within the first 30 days after inclusion, patients exhibited substantially higher incidence rates of venous thromboembolism (VTE) and major bleeding (MB) compared with referents. The incidence rate of VTE was 30.39 per 1,000 person-years among patients versus 8.14 among referents, while the corresponding rates for MB were 88.78 and 31.87 per 1,000 person-years, respectively. Compared with referents, patients had a HR of 3.68 (95% CI, 3.05-4.44) for VTE and a HR of 2.52 (95% CI 2.27-2.80) for MB within the first 30 days after inclusion. The risk for VTE remained elevated through the 31–60-day interval (HR 2.09; 95% CI, 1.63-2.69), whereas the risk for MB declined sharply after the first month (HR 1.02; 95% CI 0.87-1.21).

Conclusion: Patients undergoing surgery for LSS face a significantly higher risk for VTE and MB compared to a matched population. This hazard was most acute during the first 30 postoperative days. While these risks decline sharply thereafter, the risk of VTE remains significantly elevated during the first 2 months following LSS surgery.