Degenerative spondylolisthesis and spinal stenosis
"In nonrandomized as-treated comparisons with careful control for potentially confounding baseline factors, patients with degenerative spondylolisthesis and spinal stenosis treated surgically showed substantially greater improvement in pain and function during a period of 2 years than patients treated nonsurgically" according to a randomized controlled trial. 
Chronic nonspecific lumbalgia
Several systematic reviews of spinal fusion for chronic nonspecific lumbalgia have been performed."Surgery for radiculopathy with herniated lumbar disc and symptomatic spinal stenosis is associated with short-term benefits compared to nonsurgical therapy, though benefits diminish with long-term follow-up in some trials" according to one systematic review. "Surgery may be more efficacious than unstructured nonsurgical care for chronic back pain but may not be more efficacious than structured cognitive-behavior therapy" according to one systematic review.
Several randomized controlled trials of spinal fusion for chronic nonspecific lumbalgia have been performed."Lumbar fusion in a well-informed and selected group of patients with severe CLBP can diminish pain and decrease disability more efficiently than commonly used nonsurgical treatment." according to a randomized controlled trial. " The success rate was 50% in the fusion group and 48% in the cognitive intervention/exercise group" according to a randomized controlled trial. "The main outcome measure showed equal improvement in patients with chronic low back pain and disc degeneration randomized to cognitive intervention and exercises, or lumbar fusion." according to a randomized controlled trial. "Both groups reported reductions in disability during two years of follow-up, possibly unrelated to the interventions" according to a randomized controlled trial. 
- Anonymous (2015), Spinal fusion (English). Medical Subject Headings. U.S. National Library of Medicine.
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- Brox JI, Reikerås O, Nygaard Ø, Sørensen R, Indahl A, Holm I et al. (2006). "Lumbar instrumented fusion compared with cognitive intervention and exercises in patients with chronic back pain after previous surgery for disc herniation: a prospective randomized controlled study.". Pain 122 (1-2): 145-55. DOI:10.1016/j.pain.2006.01.027. PMID 16545523. Research Blogging.
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