Spinal Fusion and Adjacent Segment Degeneration
Adjacent segment degeneration (ASD) is a condition that often occurs after a spinal fusion surgery. Adjacent segment degeneration affects the intervertebral joint(s) above and below the area of the spinal fusion surgery. Adjacent segment degeneration can occur anywhere along the spine.
Here is the clinical definition of Adjacent segment degeneration: A complication of spine surgery that can be seen on an x-ray, CT scan or MRI as changes in the motion segments above or below the surgery site.
No one knows for sure if spinal fusion surgery actually causes the adjacent segment degeneration. Of course there are many other factors at work in the development and progression of adjacent segment degeneration. For example, a 1999 study by Etebar published in the Journal of Neurosurgery looked at 125 fusion patients in which rigid hardware was implanted to correct degenerative instability. The study found that post-menopausal women had an especially high risk for Adjacent segment degeneration!
What makes the Joints Degenerate when you have post Fusion Surgery Adjacent Segment Degeneration?
After a fusion surgery you will lose the ability to move your spine at the place where the spinal fusion procedure was done. This means you will no longer be able to bend forward, arch back, twist or tilt your spine at the specific level or levels fused by the surgery.
But that motion has to go somewhere in order to accommodate the things you do hundreds of times during a day, things like sitting, standing, walking, reaching, lifting and more.
Usually the motion goes to the joints next to or adjacent to the fusion surgery site.
You might say that adjacent segment degeneration is the result of extra wear and tear on the intervertebral joints above and below your surgery site. These joints now have to do double duty in order to make up for the immovable segments of your spine. Now they are subject to extra stress, and this will likely lead to degenerative changes.
Does Post Spinal fusion Adjacent Segment Degeneration Cause Pain?
While degenerative spinal changes associated with adjacent segment degeneration does show up on x-rays, they do not necessarily cause pain or other symptoms. Should symptoms emerge, however, your doctor may diagnose you with adjacent segment degeneration.
When Does Post Spinal fusion Adjacent Segment Degeneration Start?
Post Spinal fusion Adjacent Segment Degeneration takes time to develop. Studies evaluating the incidence of Post Spinal fusion Adjacent Segment Degeneration show that it may follow spinal surgery patients for up to 20 years. For example, studies show that people who have spinal fusion surgery when they are young most likely will develop Post Spinal fusion Adjacent Segment Degeneration as they age.
Will Post Spinal fusion Adjacent Segment Degeneration Add to My Medical Problems?
So what will your exact diagnosis be if changes are seen on your films after a spinal fusion? Unfortunately, there is not much research on this topic. A small study done in 1988 by Lee, published in Spine and involving 18 patients found that the most common type of degeneration in cases of Post Spinal fusion Adjacent Segment Degeneration was related to facet joint arthritis. Another study by Schlegel done in 1996, also published in Spine and involving 58 patients found incidences of spinal stenosis, disc herniation and spinal instability after spinal fusion surgery.
The good news is the presence of the degenerative changes in your spinal joints after a spinal fusion surgery does not necessarily mean you are not a candidate for Disc Replacement Surgery.
While some people do need a second surgery often Disc Replacement surgery can be done which will relieve the symptoms of Post Spinal fusion Adjacent Segment Degeneration and prevent further damage.
Cammisa, F., M.D., F.A.C.S. Chief, Spinal Surgical Service at Hospital for Special Surgery. Email Interview. Jan 2012.
Etebar S, Cahill DW. Risk Factors for adjacent-segment failure following lumbar fixation with rigid instrumentation for degenerative instability.J Neurosurg. 1999;90(2 Suppl):163-9.
Kyoung-Suok Cho, M.D., et. al. Rik Factors and Surgical Treatment for Symptomatic Adjacent Segment Degeneration after Lumbar Spine Fusion. J Korean Neurosurg Soc. 2009 November; 46(5): 425–430.
Hilibrand, A., MD.Et. al. Radiculopathy and Myelopathy at Segments Adjacent to the Site of a Previous Anterior Cervical Arthrodesis.Journal of Bone and Joint Surgery. 1999.
Lee, C.K. Accelerated degeneration of the segment adjacent to a lumbar fusion.Spine (Phila Pa 1976). 1988 Mar;13(3):375-7.
Levin, et. al. Adjacent Segment Degeneration Following Spinal Fusion for Degenerative Disc Disease. Bulletin of the NYU Hospital for Joint Diseases 2007;65(1):29-36
Schlegel JD, et. al. Lumbar motion segment pathology adjacent to thoracolumbar, lumbar, and lumbosacral fusions. Spine (Phila Pa 1976). 1996 Apr 15;21(8):970-81.
Siewe, J., et. al Comparison of standard fusion with a "topping off" system in lumbar spine surgery: a protocol for a randomized controlled trial. BMC Musculoskeletal Disord. 2011. Oct 18. http://www.ncbi.nlm.nih.gov/pubmed?term=22008088%5Buid%5D
Toerge, J. DO, Medical Director Musculoskeletal Institute National Rehabilitation Hospital, Washington, DC. Email Interview. Jan 2012.