Why does neck fusion have the potential for making things worse instead of better? Should I skip this treatment idea and just go for a disc replacement? I thought I understood everything my surgeon told me about these two choices -- right up until I got home and tried to explain it to my wife. Now I have more questions than answers.
When the spine is unstable from degenerative disc disease and conservative (nonoperative) care does not help reduce pain, improve function, and stabilize the spine, then surgery is sometimes the next step. Fusion is one option. Disc replacement is another. Each one of these choices has advantages and disadvantages to consider.
For example, when successful, fusion eliminates motion at the diseased level. That's the positive aspect of this procedure. But at the same time, when one segment doesn't move, the segment above and below the fused area takes on more stress and load. Over time the result can be a condition known as adjacent segmental disease or ASD.
With ASD, there is an increase in motion above and below the fused level. The center of rotation for those vertebra can be altered causing uneven wear on the spinal joints. Simply stated, fusion changes the normal, anatomic motion in the spine. That's good when trying to stabilize a sloppy joint that is unstable and potentially damaging. That may not be so helpful if the result is a faster degenerative process in the spine around the fusion.
Total disc replacement (TDR) helps preserve spinal motion and therefore the risk of developing adjacent segmental disease (ASD). But it's not entirely clear yet whether or not a disc replacement restores normal spinal motion. Are the joint (motion) exactly the same after disc replacement compared with normal motion? Or even compared with fusion?
Studies have already shown that compensatory motion occurs at adjacent spinal levels after spinal fusion. This increase in motion is accompanied by other effects such as increased pressure on the discs, a shift in the center of rotation, and increased vibrational stress on the spine.
As we mentioned, total disc replacement helps avoid these effects. But as a recent review of multiple studies showed, there is no major difference in kinematics at the adjacent levels after disc replacement compared with spinal fusion. The studies followed patients for up to two years after the surgery. Longer-term results might show a difference but this wasn't evident in the short-term.
We hope this bit of information helps you sort out what you heard and your current understanding of these two different procedures. Don't hesitate to ask your surgeon (or the physician's assistant if there is one) to answer any further questions you may have before having whatever procedure is your final choice. You want to be comfortable that you were fully informed when making this treatment decision.