Lumbar Disc Prosthesis Versus Multidisciplinary Rehabilitation; 8-year Follow-up

Inclusion Criteria: * aged 25-55 years * had low back pain as the main symptom for at least 1 year * structured physiotherapy or chiropractic treatment for at least 6 months without sufficient effect * Oswestry Disability Index (ODI) of at least 30 * degenerative intervertebral disc changes in L4/L5 and/or L5/S1.Degeneration had to be restricted to the two lower levels. The following degenerative changes were evaluated: at least 40% reduction of disc height, Modic changes type I and/or II, high-intensity zone in the disc, and morphological changes classified as changes in signal intensity in the disc of grade 3 or 4. The disc was classified as degenerative if the first criteria alone or at least two changes were found on magnetic resonance imaging. The discs were independently classified by two observers (orthopaedic surgeon /radiologist). When in disagreement, the images were classified by a third observer and the outcome decided by simple majority. Exclusion Criteria: * Generalized chronic pain syndrome (widespread myofascial pain) * Degeneration established in more than two levels. To be classified as a normal disc, the disc height must not be reduced more than 40% and all other criteria of degenerative disc disease aforementioned must be absent. The classification of a normal disc is performed by two independent observers. If disagreement, the pictures will be classified by a third observer and the outcome decided by simple majority. * Symptoms of spinal stenosis * Disc protrusion or recess stenosis with nerve root affection * Spondylolysis * Isthmic spondylolisthesis * Arthritis * Former fracture of L1 - S1 * Ongoing psychiatric or somatic disease that excludes either one or both treatment alternatives * Does not understand Norwegian language, spoken or in writing * Drug abuse * Osteoporosis * Congenital or acquired deformity Patients were examined by an orthopaedic surgeon and a specialist in physical medicine and rehabilitation together, which had to agree on inclusion.