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.
HOW SPINAL FUSION WORKS
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.
A spine fusion surgery involves using bone graft to cause two vertebral bodies to grow together into one long bone. Bone graft can be taken from the patient’s hip (autograft bone) during the spine fusion surgery, harvested from cadaver bone (allograft bone), or manufactured (synthetic bone graft substitute).
In addition to choices about which/how many levels to fuse and which bone graft to choose, there are many types of spinal fusion, including fusions with surgical approaches from the front (anterior), the back (posterior), both front and back, and/or from the side.
TYPES OF SPINAL FUSION
There are several types of spinal fusion surgery options. The most commonly employed surgical techniques include:
- Posterolateral gutter fusion – the procedure is done through the back
- Posterior lumbar interbody fusion (PLIF) – the procedure is done from the back and includes removing the disc between two vertebrae and inserting bone into the space created between the two vertebral bodies
- Anterior lumbar interbody fusion (ALIF) – the procedure is done from the front and includes removing the disc between two vertebrae and inserting bone into the space created between the two vertebral bodies
- Anterior/posterior spinal fusion – the procedure is done from the front and the back
- Transforaminal lumbar interbody fusion (TLIF) – Similar to the PLIF, this procedure is also done from the back of the spine
- Extreme Lateral Interbody Fusion (XLIF) – an interbody fusion in which the approach is from the side
It is important to note that with any type of spine fusion, there is a risk of clinical failure (meaning that the patient’s pain does not go away) despite achieving a successful fusion.
MULTILEVEL SPINAL FUSION
In the vast majority of cases, a lumbar spinal fusion surgery is most effective for those conditions involving only one vertebral segment. Most patients will not notice any limitation in motion after a one-level spine fusion.
When necessary, fusing two levels of the spine may be a reasonable option for treatment of pain. However, spinal fusion of more than 2 levels is unlikely to provide pain relief because it removes too much of the normal motion in the lower back and places too much stress across the remaining joints.
Fusing 3 or more levels of the spine is usually reserved for cases of scoliosis and lumbar deformity.