Table 1.

Inclusion and exclusion criteria

Inclusion criteria	Exclusion criteria
Low back pain (LBP) with or without leg pain for more than 1 year. If leg pain occurred, then LBP was dominant	Spinal stenosis requiring decompression
Conservative treatment for >3 months had failed	Moderate or worse facet joint arthritis
Confirmation of disc degeneration by MRI	Three or more painful levels at clinical examination
Age 20–55 years	No obvious painful level or levels upon evaluation by diagnostic injection (if performed)
Oswestry Disability Index >30 or back pain (VAS) >50/100 the week before inclusion	Isthmic spondylolysis/spondylolisthesis
Signed informed consent	Degenerative spondylolisthesis ≥3 mm
Patient open to considering the two treatment options	Major deformity
	Manifest osteoporosis. If osteoporosis was suspected due to gender and age (females >50), illness, or medication, osteoporosis was evaluated and excluded before inclusion
	Previous lumbar fusion or decompression with postoperative instability (e.g., facet joint damage or wide laminectomy)
	Compromised vertebral body
	Previous spinal infection or tumour
	Inability to understand information due to abuse, psychological, or medical reasons
	Language difficulties with inability to understand follow-up instruments
	Pregnancy or other medical conditions that would be a contraindication to surgery