Background and purpose: While the rates of lumbar spinal stenosis (LSS) surgery have increased continuously internationally, the role of fusion surgery in the treatment of LSS has been under debate. We aimed to assess the outcome of LSS surgery at 1 year postoperatively and to compare decompression surgery with or without fusion based on the Finnish national spine register FinSpine data.

Methods: FinSpine data of surgically treated LSS from 2015 to 2022 was included. The primary outcome was Oswestry Disability Index (ODI), and secondary ones were Visual Analogue Scale for leg and back pain. Predetermined minimal clinically important difference (MCID) for all outcome measures was used to assess the clinical significance of differences in outcomes. Propensity score matching was utilized to ensure that the treatment groups were comparable.

Results: There were 8,647 LSS patients in the data, of whom 6,751 (77%) were the subject of decompression surgery. Over 90% of patients without spondylolisthesis received decompression alone. At 1-year follow-up, ODI was on average 20.6 (95% confidence interval [CI] 19.3-21.9]) for the fusion group and 23.3 (CI 22.5-24.0) for the decompression group. Differences in ODI, VAS leg pain, or VAS back pain were below the MCID. The share of patients reaching ODI percentage change score ≥ 30% was 74% (CI 71-78) in the fusion group and 66% (CI 63-68) in the decompression group.

Conclusion: Most of the LSS patients experienced significant improvement after LSS surgery. We found no clinical differences between decompression surgery with and without fusion.