The Lumbar Interbody Fusion vs. Multidisciplinary Rehabilitation (LIFEHAB) Trial

Inclusion Criteria: 1. Male and non-pregnant female patients between 20 and 65 years of age with persistent low back pain of at least one year's duration at inclusion 2. Received non-operative treatment in line with national \[50\] and international \[49\] guidelines, including at least self-management, exercise, and physical therapy, without satisfactory effect before study enrolment 3. Back-related disability: ODI 30 - 60 points at baseline 4. Back pain \> leg pain 5. One- or two-level disc degeneration between L2 and sacrum with any of the following: * High-intensity zone (HiZ) * Modic changes * Severe disc height reduction exceeding 50% of the cranial disc Exclusion Criteria: 1. Multilevel disc degeneration requiring intervention beyond two levels 2. Spondylolysis or lytic spondylolisthesis 3. History of previous spondylodiscitis 4. Previous lumbar fusion surgery 5. Scoliosis \>20 degrees 6. Signs of a vertebral fracture at the planned level of fusion or its adjacent levels 7. Active smokers 8. Unlikely to adhere to treatment or complete follow-up (e.g., ongoing serious psychiatric disease, drug abuse, plans to move outside the catchment areas of the trial centers) 9. Significant nerve root compression assessed by MRI and clinical examination 10. BMI \> 40 11. Not understanding the Norwegian language. 12. Generalized myalgia, including history or signs of fibromyalgia and myalgic encephalitis 13. Contraindications to MRI (e.g., cardiac pacemaker electrodes, metal implants in the eye or brain, claustrophobia). 14. Active cancer 15. Disabling chronic neurological disease (e.g., Parkinson's disease, ALS, MS) 16. Disabling osteoarthritis of the hip or knee (Kellgren \& Lawrence grade III or higher) 17. Daily use of morphine equivalents ≥ 60mg or regular use of morphine-containing pain patches 18. Decline specific treatment arm