Treatment Options

Motion Technology / Dynamic Stabilization / Disk Replacement

Spinal Motion

Your spine is made up of 24 vertebrae and the connection between each forms a joint, or "motion segment", with the vertebra above and the vertebra below. These individual motion segments do not provide the same range of motion as elbows and knees, but they work together to allow for forward and backward bending, side-to-side bending and rotation.

Movement at a single motion segment is limited to only a few degrees (focal motion), but since motion segments are stacked on top of each other, considerable movement is possible (global motion). And, certain parts of the spine allow for more movement than others. For instance, you may have noticed that the bones in your neck provide more motion than those in your lower back.

It is important to understand that for most patients considering spinal fusion, their worries that they will lose the ability to bend are unfounded. Why? Because the majority of fusions only involve one or two levels of the spine, so most patients continue to move and bend, as they wish with little or no change in their global motion.

Although spinal fusion continues to be the gold standard for treating degenerative spinal conditions, there are some new spinal technologies being investigated in laboratories and clinical trials.

Artificial Disk Replacement

Most surgeons consider the potential ideal candidate for artificial disc replacement to be single-level degenerative disc disease. Patients with conditions such as stenosis, spondylolisthesis, scoliosis, spinal instability or osteoporosis are not considered candidates.

Artificial disc replacement is designed to restore the normal disc height (the same purpose a cage serves in spinal fusion) by replacing the damaged intervertebral disc with a mobile implant. There are several types of artificial discs being studied including those fabricated from combinations of metal, polyethylene, polyurethane, and other biomaterials. In the lumbar spine the goal of these devices is to replace a relatively small amount of normal motion occurring at these joints.

An artificial disc is implanted through an anterior surgical approach. In the case of a lumbar artificial disc, should the disc wear out, break, dislocate, or come loose, a revision surgery can be life threatening, so it is important to understand the potential complications.

Nucleus Replacement

A disc nucleus replacement device is designed to replace only the inner portion of the disc (the nucleus). There are many implant designs and materials being studied including metal, ceramic, hydrogel, elastic coils and various injectable materials.

In theory, a nucleus replacement could be easier to revise in the event that further surgery becomes necessary. And, the procedure has the potential to be a less invasive than artificial disc replacement. The safety and effectiveness of disc nucleus replacement technologies is currently being investigated by the Food and Drug Administration (FDA), but these devices are not approved for use in the United States.

Extra-discal Devices

Unlike nucleus replacement and total disc replacement, extra-discal devices (such as flexible rods or spinous process spacers) preserve the intervertebral disc and vertebral structure. With this type of treatment, a device is attached to the back of the spine to help stabilize the motion segment while leaving the intervertebral discs intact.

Some extra-discal devices can be implanted through a minimally invasive, posterior surgical approach. The safety and effectiveness of these devices is currently being investigated by the FDA.

What Are Doctors Saying?

So are these technologies going to be highly successful? The jury is still out, and only time will tell.

At a recent meeting of the American Orthopaedic Association, surgeons were asked what treatment they would prefer for themselves if they had unrelenting low back pain from a single degenerative disc.

Of the 133 surgeons surveyed(1), only 7 percent stated that they would choose disc replacement. So what would the surgeon's choose? About 47 percent said they would choose spinal fusion and close to 47 percent would choose chronic pain management.

Why wouldn't these surgeons elect to have disc replacement? Well, 59 percent felt unsure about the long-term durability of the implants, 30 percent expressed concern that discs will be over-used, and 9 percent worried about the surgical complications.

New doesn't always mean better. It is important to remember that there are many types of spinal products and surgical techniques, but they aren't equally effective for everyone. Factors, such as your individual symptoms and diagnosis, play a significant role in which product is best for you.

As you read this please keep in mind that all treatment and outcome results are specific to the individual patient. Results may vary. Complications, such as infection, blood loss, bowel or bladder problems, are some of the potential adverse risks of spinal surgery. Please consult your physician for a complete list of indications, warnings, precautions, adverse events, clinical results, and other important medical information.

1 Boden SD, Balderston RA, Heller JG, Edward N. Hanley, Jr., and Zigler JE. An AOA Critical Issue, Disc Replacements: This Time Will We Really Cure Low-Back and Neck Pain? Journal of Bone and Joint Surgery 2004; 86: 411-422.

It is important that you discuss the potential risks, complications, and benefits of the spinal surgery with your doctor prior to receiving treatment, and that you rely on your physician's judgment. Only your doctor can determine whether you are a suitable candidate for this treatment.
The LT CAGE® and METRx™ Systems incorporate technology developed by Gary K. Michelson, M.D.

Published: October 27, 2004 Updated: January 05, 2006

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