Table 1 Inclusion and exclusion criteria

Age between 18 and 80 years, clinical symptoms of LSS, not responding to at least 3 months of non-surgical treatment, radiological findings (foraminal, central canal or lateral recess stenosis) corresponding to the clinical symptoms such as back pain, leg pain or neurologic claudication, and understanding the Norwegian language (spoken and written).

Previous surgery at the level of stenosis, previous fracture or fusion of the thoraco-lumbar spine, cauda equina syndrome (bowel or bladder dysfunction) or fixed complete motor deficit, ASA (American Society of Anesthesiologists) grade 4 or 5, more than 20° lumbosacral scoliosis, distinct symptoms in lower limbs due to other diseases, stenosis in more than three lumbar levels, being unable to comply fully with the protocol, isthmic defect in pars interarticularis at the level of stenosis, participation in another clinical study that could interfere with the present trial, alcohol or substance abuse and ≥ 3 mm spondylolisthesis verified on upright lateral view X-ray.