Lumbar fusion improves instability of the spine. As a disc degenerates and flattens, the vertebrae slip back and forth. This irritates the joints and creates or worsens stenosis (arthritis of the spine), irritating the nerves, causing back and leg pain.
Next, a bone graft is usually placed along the vertebrae and is then fused together with the vertebrae. In some cases, the fusion itself is unnecessary and the bone graft simply grows together with the vertebrae naturally.
Spinal fusions are generally recommended when a doctor can pinpoint the location of your pain, usually through an MRI, CT or x-ray. But ultimately, there can be a number of different medical conditions in which a lumbar spinal fusion may be recommended. Some of these conditions include degenerative disc disease (DDD), recurring disc herniation, lumbar spondylolisthesis, scoliosis, fracture, or a weak spine caused by infections or tumors.
Risks associated with undergoing a lumbar fusion procedure include pain, failure of the fusion, blood clots, nerve injury, graft rejection and infection. It should be noted that the risks of this surgical procedure depend greatly on your age, health, and the underlying reason that you are having the surgery.
Several FDA studies are comparing fusion to total disc replacement. While it is likely the FDA will approve some discs, the long-term results are years away.