Table 1 Inclusion and exclusion criteria

Inclusion criteria

• Male and female patients age 18–75 years

• Chronic low back pain unresponsive to at least six months of conservative care

• MRI and standing x-ray evidence of Pfirrmann Grade III or greater disc

• Degeneration and/or degenerative or isthmic spondylolisthesis of Grade I or II

• Signed informed consent

Exclusion criteria

• Osteoporosis

• Patients with prior failed fusion at the same level

• Degenerative scoliosis

• Degenerative spondylolisthesis greater than Grade II

• Pregnancy

• Psychiatric or mental disease

• Alcoholism (drinking more than 5 units per day)

• Active infection or prior infection at the surgical site

• Active cancer

• Insufficient language skills to complete questionnaires

• Participation in another study

• More than two symptomatic levels that need fusion

• Planned (e)migration abroad in the year after inclusion