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Report on Disc Replacements for the Cervical Spine

It's been just slightly more than 10 years since the first cervical disc replacements were done on a group of patients in England. These first generation implants had design problems that have since been improved. In this article, surgeons from Washington University in Washington D.C. offer a review of the cervical disc arthroplasty (replacement) procedure.

In the beginning, cervical disc replacements were used when all else failed. Fusion had created more problems at the adjacent levels. The hope was to save the affected segment. But things have progressed far enough along that there is talk about expanding the use of cervical disc arthropathy (CDA).

Until now, degenerative disc disease has been treated first, nonoperatively. If and when conservative care failed to reduce pain, improve motion, and restore function, then a procedure called anterior discectomy and fusion (ACDF) was the gold standard of treatment.

In the ACDF procedure, the spine is entered from the front of the body (anterior). The diseased disc is removed (discectomy) and the segment is fused. The main advantage of spinal fusion is that it provides stability for the affected level. The main disadvantage is that motion is lost. Over the years, the ACDF (fusion) procedure has yielded better and better results. Studies report long-term results in the 90 per cent range for excellent outcomes.

So you can see that surgeons might be reluctant to use a disc replacement when the ACDF procedure has been so successful. But still, the ACDF does not preserve motion and that's an important loss to consider. And long-term studies have confirmed that with the fusion procedure, one-fourth of all patients end up having another surgery for adjacent disc disease.

With loss of mobility at one level (the fused level), biomechanics of the spine are altered. Load is transferred through the spine to the next (adjacent) level. The added wear and tear speeds up the degenerative disc disease process. If this complication could be avoided with cervical disc replacement, more surgeons would consider switching from fusion to disc replacement.

Early results from studies of cervical disc arthroplasty are limited in scope. Although the outcomes look good, the data only extends up to four years at the most. Any information about five or 10-year outcomes will be forthcoming but isn't available now. However, so far, the early (two to four year) success rates with cervical disc replacement are equal to the results for cervical fusion.

Rates of reoperation for adjacent disc disease are much lower for disc replacement (one per cent) compared with fusion (3.4 per cent). But again, these statistics are gathered within the first two years of the procedure. Long-term results just aren't here yet. Likewise, there isn't any long-term data available on durability and wear rates for cervical disc replacements.

What about the complication rate between these two procedures? How do these compare? We've mentioned the adjacent disc disease as one complication. Other possible complications include dysphagia (difficulty swallowing), infection, length of time in surgery (greater with disc replacement), and time to return-to-work (longer for fusion patients).

Dysphagia is more likely to occur with disc replacements but the actual rate of occurrence is unknown. Infection is always a concern with any surgery. Infection is potentially more likely with disc replacement because of the longer time needed to perform the procedure.

The authors conclude by saying that cervical disc replacement has a good early showing. More time and more studies are needed to know if it will eventually be able to replace fusion as the gold standard for cervical disc disease. With more and more surgeons using these implants, we should have an answer to the question in the next few years.

References: Rishi Bhatnagar, et al. Cervical Disc Arthropathy. In Current Orthopaedic Practice. May/June 2010. Vol. 21. No. 3. Pp. 306-309.

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