Q: I've had a neck fusion at C56 and now the C45 level is starting to go.Is it possible to have a disc replacement at C45 with a fusion at C56? And can I have the fusion removed and put a disc in there?

A: These are very good questions! The use of total disc replacements versus fusion and the replacement of a fusion with disc replacement implants is one currently being studied. Likewise, the idea of a disc replacement for adjacent disc disease following a fusion is under investigation.

In fact, a recent study at the University of Washington Medical Center in Seattle explored some of these questions. The study was done with nine cadaver necks. Cadavers are human bodies preserved after death for use in studies like this.

The surgeon fused some necks and compared cervical spine (neck) movement with other necks that had a one-level fusion plus a one-level disc replacement. The fusion and disc replacement were at adjacent levels. The combination fusion-disc replacement is referred to as a hybrid. As part of the study, they did perform a fusion at one level and then reversed the procedure. This involved removing the fusion and replacing it with a disc replacement.

There were three significant findings from this study:

Neck motion is the same after a disc replacement when compared with a hybrid (disc replacement at one level with fusion at the next level)
There was no difference in neck motion regardless of the location of the fusion (above or below the disc replacement) in the hybrid procedure
Results after the hybrid procedure (again measured in terms of neck motion) were better than with a two-level fusion.
Using cadavers is helpful but still not the same as a live human. So the effects observed may not truly reflect what is happening inside the human body under the same conditions. And cadaver studies do not allow for observation of long-term effects.

Further study is needed to evaluate the value of disc replacement versus disc replacement combined with fusion versus fusion alone. Additionally, there is a need to look at the results of these comparisons at one-level versus two-level procedures.

At least for the moment, it looks like the hybrid approach may be a better choice than a two-level fusion. Reversal of vertebral fusion and replacement with a disc implant may be beneficial but will also require some additional study before becoming a routine procedure. It is certainly worth asking your surgeon about all options and possibilities open to you, including this one of a fusion reversal that you have asked about.

Reference: Michael J. Lee, MD, et al. Disc Replacement Adjacent to Cervical Fusion. In Spine. November 1, 2011. Vol. 36. No. 23. Pp. 1932-1939.