Background and purpose – During recent years, spine surgery techniques have advanced, the population has become older, and multiple high-quality randomized controlled trials that support surgical treatment for degenerative spinal stenosis and spondylolisthesis have been published. We assess the incidence and trends in spine fusion and decompression surgery in Finland between 1997 and 2018. Patients and methods – We used nationwide data from the Finnish nationwide National Hospital Discharge Register. The study population covered all patients aged 20 years or over in Finland (5.5 million inhabitants) during a 22-year period from 1997 through 2018. All patients who underwent spinal decompression were included. Patients with both decompression and fusion codes were analyzed as fusions. Results – 76,673 lumbar spine decompressions and fusions were performed during the study period. The incidence of lumbar spine decompressions increased from 33 (95% CI 23-45) per 100,000 person-years in 1997 to 77 (CI 61-95) per 100,000 person-years in 2018. The incidence of lumbar spine fusions increased from 9 (CI 5-17) per 100,000 person-years in 1997 to 30 (CI 21-43) per 100,000 person-years in 2018. The increase in incidence of lumbar spinal fusions was highest among women aged over 75 years, with a 4-fold increase. Interpretation – The incidence of lumbar spine fusions and decompressions increased between 1997 and 2018 in Finland. These findings may be the result of the emergence of advanced surgical techniques but may also be the result of an aging population and increased evidence supporting the surgical treatment of various spinal pathologies.