Artificial Lumbar or Cervical Disc

The spine is a column composed of bones, discs and ligaments. The bones (or vertebrae) provide support and structure of the spine. The discs in between the vertebrae act like shock absorbers. The discs also contribute to the flexibility and mobility of the spinal column. Spinal discs are made up of two parts:

• The inner portion of the disc is a jelly-like material and is called the nucleus pulposus.
• The outer part, the anulus fibrosus, is stronger and more fibrous. The anulus fibrosus surrounds and supports the inner jelly material. The anulus is rich in nerve fibers, especially the back portion, and may play a role in the production of discogenic back pain.

Disc material is mainly composed of water and proteins. Aging gradually reduces the water content. This can cause the disc to flatten out and even develop tears or cracks throughout the anulus fibrosus. These discs are often referred to as “degenerative” discs and may or may not cause pain.

In the case of a degenerative disc, the inner jelly material (the nucleus pulposus) can bulge out and press up against the anulus fibrosus. This can stimulate the pain receptors and cause pain. Cracks or tears that develop within the anulus fibrosus can also become a source of pain. The inner nucleus can also come out through the cracks in the anulus and compress nerves or spinal cord, a condition that may cause weakness, pain, pins and needles or numbness, and may require surgery.

Disc Replacement

A new technique involves removing the disc and replacing it with an artificial disc. This approach has two primary benefits:

• Motion is maintained and the patient will not feel a restriction in the range of motion.
• Theoretically, adjacent segment disease will not occur.

Consequently, patients undergoing placement of an artificial lumbar disc may need fewer surgeries in the future.

Indications

Not all patients with back pain are candidates for artificial lumbar disc prosthesis. The ideal patient has the following requirements:

• Back pain thought to be coming from the discs

• No previous surgeries other than a lumbar microdiscectomy

• Not be markedly overweight

• Relatively few if any abdominal operations

• Little in the way of leg symptoms

Part of the diagnostic work to determine the advisability of disc replacement includes plain x-rays, MRI scanning, facet blocks and a lumbar discogram.

Artificial discs are new and still somewhat experimental.  There is a chance that they will not be helpful and they may be worse than conventional disc replacement techniques using bone.  The conventional bone technique works up to ninety-five percent of the time in well selected patients.  It is simple and involves no complex mechanical devices.  The total disc is made of high tech plastic and metal alloy.  It may wear out, has a higher risk of infection, and may require periodic replacement.  Talk to your surgeon about this and whether conventional surgery might be safer for you.

The new disc replacement is not indicated for more than one level, for fractures, for instability, for spondylolysis or for younger patients who are likely to wear it out in their lifetime.

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