There are a number of factors that are important in considering cervical disc replacement vs. a traditional decompression and fusion surgery. Perhaps the most important consideration is that longer term studies and follow-up will be needed to fully understand the potential risks and benefits of cervical disc replacement. At present, most of the information on the discs remains theoretical.
Indications for an Artificial Cervical Disc
The indications for a cervical disc replacement are generally the same as for a cervical discectomy and fusion. A person must have a symptomatic cervical disc, which may be causing arm pain, arm weakness or numbness with some degree of neck pain. These symptoms may due to a herniated disc and/or osteophytes compressing adjacent nerves or the spinal cord. This condition typically occurs at cervical spine levels C4-5, C5-6, or C6-7.
Prior to being admitted into a clinical trial, the candidate must usually meet strict defined entrance criteria, which at least include:
- Undergo a trial of non-operative treatment for at least 4 to 6 weeks, usually consisting of anti-inflammatory medication and physical therapies
- Have had no prior neck surgery
- Must be deemed a good surgical candidate
At this time in US clinical trials, only single-level cervical disease is being treated. In Europe multilevel disease is being addressed. Multilevel disease will hopefully be cleared for clinical trials in the United States in the near future.
For a listing of cervical artificial discs in development or clinical testing (as of 2/5/07), please see Cervical Artificial Disc Replacement Technologies.
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Surgical Procedure for Cervical Disc Replacement
The standard surgical procedure for a disc replacement is an anterior (from the front) approach to the cervical spine. This surgical approach is the same as that presently used for a discectomy and fusion operation. The affected disc is completely removed including any impinging disc fragments or osteophytes (bone spurs). The disc space is distracted (jacked up) to its prior normal disc height to help decompress (relieve pressure) on the nerves. This is important because when a disc becomes worn out, it will typically shrink in its height, which can also contribute to the pinching on the nerves in the neck. See figure 7.
At this point, using x-rays or fluoroscopy, the artificial disc device is implanted into the prepared disc space. Postoperatively, the patient typically can go home within 24 to 48 hours with minimal activity limitations.
Potential Risks and Complications
The potential complications with an artificial device are at least similar to an anterior cervical discectomy and fusion and may include:
- Blood loss
- Nerve injury or paralysis
- Need for further surgery
Although these complications can be severe, they are very rare occurrences.
In addition, the artificial disc does theoretically have some of the same potential complications associated with total hip and knee arthroplasty. An arthroplasty is a mechanical device and by the laws of physics will wear out over long periods of time. That time period remains to be defined for total disc replacement. In addition, small particle debris may react with the body. Laboratory and animal studies for some of the devices have shown that after simulating ten years of wear, only minimal disc wear occurs and the materials appear to be well tolerated over time.
Potential Benefits of a Cervical Artificial Disc vs. a Fusion
Unlike a fusion procedure, the artificial disc surgery does not have the potential complications associated with taking a bone graft from the hip nor the theoretical risk of infection transmission from using a cadaveric bone graft. Clearly the issue of bone graft healing is eliminated. The disc replacement also should reduce the chances for adjacent segment disease (versus a fusion), since the artificial disc should allow for more normal neck motion and absorb some of the daily stresses of the neck. The length and type of activity restrictions following surgery are also much less with disc replacement.