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Important Way to Compare Results Between Disc Replacement and Fusion

Posted on: 05/29/2013
There are many ways to evaluate the results of treatment for severe neck pain and instability following cervical fusion or disc replacement. Change in symptoms (numbness, pain, loss of motion, loss of function) is a common source of information about what works well and what doesn't.

In this study, the authors chose rate of reoperation after five years as the main means of evaluating and comparing results between disc replacement and neck fusion. The type of disc replacement system they used was the ProDisc-C. The type of fusion procedure was the anterior cervical discectomy and fusion (ACDF). ACDF involves removal of the diseased disc with a bone-packed spacer (bone graft) placed in the space left by the missing disc. The use of hardware (plate and screws) along the front of the spine provided support and stability until healing took place.

Just over 200 patients with single-level disc disease between C3 and C7 were randomly divided into two separate treatment groups. Half (103 patients) received the disc replacement. The other half (106 patients) had the fusion procedure. The main difference between these two treatment types is the effect on neck motion. Fusion prevents movement at the level that was grafted together. Disc replacement allows for motion (though not usually full, anatomic motion).

Besides the five-year reoperation rate, they also took a look at the effect of the two procedures on the next vertebra. The incidence of adjacent segment disease (ASD) has been known to be increased after fusion compared with disc replacement. ASD refers to increased pressure in the disc spaces next to the fusion site. There can also be increased motion at those levels observed with ASD.

The concern is that fusion (or perhaps disc replacement) will increase the speed at which the next disc/vertebra starts to degenerate and break down. By comparing the five-year results in two groups of matched patients, it is possible to compare the durability of the disc replacement and the rate of adjacent segment disease with both procedures.

Although disc replacements help maintain spinal motion, they are devices that can break, shift, or sink down. Any of these problems can result in return of painful neck and/or arm symptoms and the need for a second surgery (referred to as a reoperation). Other studies have shown that the fusion procedure does have a much higher (two to six times higher) rate of reoperation compared with disc replacement.

Let's look at what happened with these 200+ patients. Data was collected at six weeks after the surgery and again after six and 12 months. The last collection point was after five years, although the authors intend to recheck everyone seven years after the primary (first) surgery.

A dozen patients in the fusion group had at least one additional surgery (three of those 12 had more than one reoperation). There were problems with pseudoarthrosis (movement at the fusion site creating a "false joint") and movement of the hardware (plate) lifting off the spine. This "lift-off" of the plate then caused pressure on the esophagus resulting in difficulty swallowing.

Only three of the ProDisc-C had revision surgeries. Two of those three had the disc replacement removed and the neck fused after all. None of the implanted discs broke or failed. Overall, fusion procedures had a much higher reoperation rate (five times more reoperations). The two main reasons for reoperations in either group were persistent pain and significant adjacent-segment disease (ASD).

The authors concluded that the advantages of disc replacement continue to exceed those of the fusion procedure, which has always been the "gold standard" for treatment of degenerative disc disease. In time, if motion is spared with the disc replacement, there is less adjacent segment disease, and lower reoperation rates, disc replacement may replace fusion as the "gold standard" treatment.

These results support similar findings in other studies comparing these two treatment approaches for degenerative disc disease in the cervical spine (neck). Watch here for continued (seven-year) results of this study in two more years.

Rick B. Delamarter, MD, and Jack Zigler, MD. Five-Year Reoperation Rates, Cervical Total Disc Replacementi Versus Fusion, Results of a Prospective Randomized Clinical Trial. In Spine. April 20, 2013. Vol. 38. No. 9. Pp. 711-717.

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