Concerns After Fusion or Nonfusion in the Cervical SpineStep-by-step, orthopedic surgeons are finding better ways to treat neck and arm pain from degenerative disc disease of the neck. Severe neck pain and other symptoms down the arm (e.g., pain, numbness, tingling) are the usual reasons patients consider surgery for this problem.
Over the years, advances and improvements have been made in the surgical approach for this condition known as cervical spondylosis. Nearly 60 years ago, in the 1950s, the first anterior cervical diskectomy and fusion (ACDF) was done. This has now become the standard of care for symptomatic cervical spondylosis.
The surgeon removes the diseased or damaged disc and any bone spurs that might be causing problems. This part of the procedure is called decompression. Then the spine is surgically stabilized. This is the fusion part of the surgery. A metal plate is attached to the front (anterior) side of the spine. Bone graft material is used to help speed up the stabilization process.
More recently, ACDF has been replaced with a different surgical approach. The development of a total disc replacement (TDR) has been introduced. Efforts to compare results of treatment between ACDF and TDR are underway. The main effect that concerns surgeons is adjacent segment disease (ASD).
Adjacent segment disease refers to breakdown of the vertebrae next to the fusion or disc replacement implant. At first it was expected that the increased stress and strain from a fusion (no movement at the fused level) would result in adjacent segment disease but not after a total disc replacement (TDR) where movement is preserved.
But so far, no difference has been observed between these two procedures in terms of adjacent segment disease and the need for a second (revision) surgery. Of course, total disc replacements (TDRs) are new enough that results are limited. The number of patients in reported studies is small and long-term outcomes aren't available yet.
There is much to evaluate when comparing the results of these two procedures. Studies are needed to measure intradiscal pressure, strain distribution across the adjacent discs, and shear forces on the connecting vertebrae. Neck motion is another way to compare outcomes between ACDF and TDR. Changes in motion occur at the fused levels but overall neck motion improves for both ACDF and TDR just from taking away the pain.
In summary, available evidence suggests that cervical disc replacement is biomechanically superior to spinal fusion. In theory, total disc replacement (TDR) should decrease stress and strain on the neighboring spinal segments. But this may not be the reality based on studies done so far. In time with continued long-term follow-up, the results of fusion (ACDF) versus nonfusion (total disc replacement) surgery will be fully known.
The hope is that the number of patients who experience adjacent segment disease will decline in both groups as surgical techniques continue to improve and advance. Changes in design of disc implants will also help eliminate problems and provide better outcomes.
Samuel K. Cho, MD, and K. Daniel Riew, MD. Adjacent Segment Disease Following Cervical Spine Surgery. In Journal of the American Academy of Orthopaedic Surgeons. January 2013. Vol. 21. No. 1. Pp. 3-11.
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