Surgical methods offered to patients with chronic low back pain are controversial. In addition, new and expensive treatment methods like total disc replacemet (TDR) are a challenge for the health care services. At present, ongoing randomized studies in both Europe and USA are comparing TDR to fusion. However, to our knowledge, no randomized trials have compared TDR to non-surgical treatment. The aim of the present study is to evaluate the effect of a comprehensive and structured non-surgical treatment with TDR surgery in patients with chronic low back pain and localized degenerative disc changes.

Main hypothesis: There is no difference in treatment effect between surgery with lumbar total disc prosthesis and a multidisciplinary rehabilitation program measured by Oswestry Disability Index after 1 and 2 years.

Secondary hypothesis: There is no difference in cost - effectiveness between surgery with lumbar disc prosthesis and a multidisciplinary rehabilitation program after 1 and 2 years.

Description of interventions.

Surgical intervention: The surgical intervention consists of replacement of the degenerative intervertebral lumbar disc with a artificial lumbar disc device (ProDisc II, Spine Solutions Inc. , New York, NY). The ProDisc consists of three pieces, two metal endplates and a polyethylene core that is fixed to the inferior endplate when the device is implanted, and is implanted through a retroperitoneal (or transperitoneal) access. Depending on the surgeon, a Pfannenstiel incision or a para median incision is used. A fluoroscope is used to ensure that the prosthesis is placed in the midline and sufficiently towards the posterior edge of the corpus vertebrae. All hospitals participating in the study will use the same artificial lumbar disc device, and standard instruments from the manufacturer are used for inserting the disc. Postoperatively, orthoses will not be used, but patients are given restrictions on heavy lifting and excessive movements the first 6 weeks after surgery. Otherwise, no instructions will be given. Six weeks after surgery, patients will be referred to physiotherapy.

Non-surgical intervention: The intervention is based on a treatment model described by Brox et al (Spine 2003;28:1913-1921) and consists of a cognitive approach and supervised physical exercise. The treatment is interdisciplinary and is directed by a team of physiotherapists and specialists in physical medicine and rehabilitation. The intervention is organized as an outpatient treatment in groups of 6 - 8 patients during a period of 12 - 15 treatment days. In agreement with the patient, individual goals for the rehabilitation process are established.

Sub-studies:

Several sub - projects will be conducted at the different hospitals in the study, in example validation of discography, RSA to validate the migration and motion of the prosthesis, a biomechanical study using DCRA technique, validation of a classification system for physiotherapy and a responsiveness of questionnaires included in the study.

Inclusion Criteria:

• Low back pain as the main symptom for at least one year.
• Structured physiotherapy or chiropractic treatment for at least 6 months without (significant) effect.
• Oswestry Disability Index score of 30% points or more
• Degenerative changes in the intervertebral disc in one or both of the two lowest levels of the lumbar spine (L4/L5 and/or L5/S1). (Degenerative changes are classified based on MR findings according to the following criteria: At least 40% reduction of disc height, Modic changes type I and/or II, "High intensity zone" in the disc, Morphological changes classified as changes in signal intensity in the disc. To classify the disc as degenerative the first criteria alone or at least two of the other criteria must be present. The MR series are evaluated by two independent observers.)

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