Lumbar Spinal Fusion
One of the main goals of any surgical procedure on the skeletal system is to stop the pain caused by joints that have worn out over time-degenerative joints. One of the most reliable ways to reduce pain from degeneration is to fuse the joint together. A fusion is an operation where two bones, usually separated by a joint, are allowed to grow together into one bone. The medical term for this type of fusion procedure is arthrodesis.
Spinal fusion has been used for many years to treat painful conditions in the lumbar spine. Over the past decade, there have been dramatic improvements in the way that spinal fusion operations are performed. One major improvement has been the development of fixation devices.
Only when all other conservative treatments have failed will your doctor suggest fusion surgery. Several back conditions may require a spinal fusion, including:
Degenerative Disc Disease – Degeneration of the discs between one or more vertebrae may require a spinal fusion of the vertebrae on both sides of the degenerative disc. The intervertebral discs are flat, round “cushions” that act as shock absorbers between each vertebra in the spine. The disc allows motion to occur between each vertebra. Removing a degenerated disc and allowing the two vertebrae to fuse together can reduce pain.
Spinal Instability – Each spinal segment is like a well-tuned part of a machine. All of the parts should work together to allow weight bearing, movement, and support. When one segment deteriorates to the point of instability, it can lead to localized pain and difficulties.
Segmental instability occurs when there is too much movement between two vertebrae. The excess movement of the vertebrae can cause pinching or irritation of nerve roots. It can also cause too much pressure on the facet joints, leading to inflammation. It can cause muscle spasms as the paraspinal muscles try to stop the spinal segment from moving too much. The instability eventually results in faster degeneration in this area of the spine.
Spine Curvature – Lumbar fusion may be needed for conditions such as scoliosis and kyphosis, where the spine has an abnormal curve. These spine deformities may result from congenital or degenerative spine conditions. A lumbar fusion may be suggested to stabilize the spine and correct the problem.
Spondylolysis and Spondylolisthesis – Spondylolisthesis is the term used to describe when one vertebra slips forward on the one below it. This usually occurs because there is a spondylolysis (defect) in the vertebra on top. There are two main parts of the spine that keep each vertebra aligned-the disc and the facet joints. When a spondylolisthesis occurs, the facet joint can no longer hold the vertebra back. The intervertebral disc may slowly stretch under the increased stress and allow the upper vertebra to slide forward. A fusion may be used for both conditions to stop motion in the problem vertebrae, where there is a spondylolysis.
Spinal Fusion Surgery
During a spinal fusion, a bone graft is used to join two or more vertebrae. The vertebrae grow together during the healing process, creating a solid piece of bone. The bone graft helps the vertebrae heal together, or fuse. The bone graft is usually taken from the pelvis at the time of surgery. However, some surgeons prefer to use bone graft from a bone bank (called allograft).
Your spine surgeon can use an anterior (from the front) approach, a posterior (from the back) approach, or a combined approach to lumbar fusion surgery.