Risk for Clinical Venous Thromboembolism and Major Bleeding after Surgery for Lumbar Spinal Stenosis: A Retrospective Matched Register-based Cohort Study with 462,533 Individuals

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 During the 1-year follow-up, VTE occurred in 0.9% (n = 700) of patients, compared with 0.6% (n = 2,277) of referents, while MB occurred in 3.7% (n = 2,870) of patients, compared with 2.2% (n = 8,648) of referents. During the first 30 days post-surgery, patients exhibited a significantly elevated hazard for both VTE (HR 3.68; 95% CI, 3.05–4.44) and MB (HR 4.01; 95% CI, 3.66–4.39). The risk for VTE remained significantly 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. Conclusion Patients undergoing LSS surgery face a fourfold relative increase in the risk of both VTE and MB during the first 30 postoperative days. While these risks dissipate over time, the elevated hazard for VTE persists for up to 60 days.