Spinal fusion is a procedure that eliminates motion between vertebrae. It also prevents the stretching of nerves and surrounding ligaments and muscles. It is an option when motion is the source of pain, such as movement that occurs in a part of the spine that is arthritic. The theory is if the painful vertebrae do not move, they should not hurt.
Fusion will take away some spinal flexibility, but most spinal fusions involve only small segments of the spine and do not limit motion very much.
A spinal fusion surgery is designed to stop the motion at a painful vertebral segment, which in turn should decrease pain generated from the joint.
There are many approaches to lumbar spinal fusion surgery, and all involve the following process:
• Adding bone graft to a segment of the spine
• Set up a biological response that causes the bone graft to grow between the two vertebral elements to create a bone fusion
• The boney fusion – which results in one fixed bone replacing a mobile joint – stops the motion at that joint segment. For patients with the following conditions, if abnormal and excessive motion at a vertebral segment results in severe pain and inability to function, a lumbar fusion may be considered:
• Lumbar Degenerative Disc Disease
• Lumbar Spondylolisthesis (isthmic, degenerative, or postlaminectomy spondylolisthesis)
Other conditions that may be treated by a spinal fusion surgery include a weak or unstable spine (caused by infections or tumors), fractures, scoliosis, or deformity.
At each level in the spine, there is a disc space in the front and paired facet joints in the back. Working together, these structures define a motion segment and permit multiple degrees of motion.
Two vertebral segments need to be fused together to stop the motion at one segment, so that an L4-L5 (lumbar segment 4 and lumbar segment 5) spinal fusion is actually a one-level spinal fusion. An L4-L5, L5-S1 fusion is a 2-level fusion.