How Artificial Disc Replacement retains the natural motion of discs in the back and reduce the risk of future disc herniations

The artificial disc concept is intended to be an alternative for spinal fusion surgery. Each year in the U.S., more than 200,000 spinal fusion surgeries are performed to relieve excruciating pain caused by damaged discs in the low back and neck areas.

Unlike knee and hip replacement patients who are typically in their 50s or 60s, many patients can benefit from artificial disc technology at a much younger age — in their 20s or 30s. Therefore, the implantation of an artificial disc in younger patients can raise a surgeon’s concern about the potential life span of the artificial disc in the spine and the need for revision surgery to replace a worn-out artificial disc, which can be complex.

Traditionally, the common treatment for repairing herniated discs in the neck was an Anterior Cervical Discectomy and Fusion (ACDF) procedure. In a fusion surgery, the disc is removed and either a bone spacer or a plastic implant is be placed in the disc space to restore disc height and remove pressure on the pinched nerves or spinal cord. A metal plate and screws are then placed on the front of the neck to hold the implant in place. The result of this procedure will be a segment that no longer moves, or is “fused”.

In the low back, because of the number of vertebrae, this loss of movement is less of a problem as the remaining vertebrae can provide enough rotational movement.

Over the past decade, several artificial discs for the neck have emerged and have worked well for single level disc herniations in the neck. However, none of these previous artificial discs addressed the patient who might have disc degeneration at two levels. Those patients were not addressed by the other implants.

The advantage of artificial disc replacement over fusion is that the neck is that it maintains normal motion and reduces the stress placed on the other discs in the neck. The goal with motion preservation is to retain the normal rotation of the neck and lessen the need for any future surgery at other levels in the neck.

A key research study presented at the North American Spine Society several years ago revolutionized surgery for a herniated disc in the neck. The research study found that the artificial disc reduced the risk of “adjacent segment disease”, or the herniation of other discs above and below where two vertebrae were fused in the traditional ACDF surgery. The study showed that when traditional fusion was used, it locked two vertebrae together, which put more strain on the other discs above and below the fusion site, often causing other discs to herniate.

As a result over the following years, the most advanced spine centers of excellence in the United States began emphasizing artificial disc replacement as the best option for treating herniated discs in the neck.

In conclusion, if your spine surgeon is not discussing artificial disc replacement as an option for ACDF surgery in your neck, you should get a second opinion for neck surgery from a regional spine center of excellence.

Colorado Spine Partners is the only spine center in the State of Colorado to be featured at SpineCenterNetwork.com, a national listing of spine centers that meet credentialing criteria, and CentersforArtificialDisc.com which features fellowship-trained spine surgeons who are proficient in artificial disc replacement.

Benefits of using an artificial disc vs. fusion

Some of the main benefits of the artificial disc parallel that of knee replacement and hip replacement. This can include the following benefits:

• An artificial disc in the neck or back, in principle, is designed to retain motion in that particular segment of the spine.
• It prevents degeneration of disc levels above and below the affected disc
• There is no bone graft required
• There can be a quicker recovery and return to work or activity
• It can be a less invasive and less painful surgery than a fusion
• There can be less blood loss during surgery

Selection of artificial discs for the neck

There are about a dozen artificial discs that have been approved by the FDA for use in the United States. The Mobi-C disc was the first artificial disc to be approved by the FDA for use at TWO levels in the neck. This was an important advance because those patients with degenerative disc disease can often have herniated discs at multiple levels in the neck. By being able to address two levels, the surgeon is able to preserve the natural motion of the neck at both levels.

Dr. Chris Johnson at Colorado Spine Partners is trained in the use of several FDA-approved artificial disc implants. He currently favors the use of the Simplify artificial disc, the Prodisc-C and Prodisc Vivo. Selection of the disc is based on what disc would be best for a specific patient, as a petite woman would need a different size disc than a large male patient.

Lumbar vs. cervical artificial discs

Because of the weight of the body and the rotational stress that the trunk places on discs in the low back (lumbar) area, more stress is placed on artificial discs in the lumbar area than in the neck (cervical) area, which only supports the weight of the head.

A second issue relates to the ease of the artificial disc surgery and any necessary revision surgery to replace a worn out artificial disc. Because the surgeon must access the front of the spine to replace a herniated disc with an artificial disc implant, an incision is made in the abdomen for lumbar discs and in the front of the neck for cervical discs. Generally speaking, it is easier and safer to access the herniated disc in the neck than it is to access a herniated disc in the low back by maneuvering around internal organs in the stomach area.

The second issue related to artificial disc replacement in the low back is that revision surgery to replace a worn out artificial disc is more complex in the low back than in the neck. Unlike knee and hip replacement patients who are typically in their 50s or 60s, many patients can benefit from artificial disc technology at a much younger age — in their 20s or 30s. Consequently, the implantation of an artificial disc in younger patients can raise a surgeon’s concern about the potential life span of the artificial disc in the spine and the need for revision surgery to replace a worn-out artificial disc, which can be complex.