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posted: 8/27/2012 6:00 AM

New device being tested to relieve spinal stenosis

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By Jack Kelly
Pittsburgh Post-Gazette

You're over 50, and when you walk more than a short distance, you get pain or cramping in your legs and lower back. The pain subsides when you sit down. But, you notice the distance you can walk before the pain recurs is getting shorter and when the pain recurs, it is more severe.

You may have spinal stenosis, a narrowing of the spinal column that puts pressure on the spinal cord or a narrowing of the openings where spinal nerves leave the spinal column.

"Stenosis" is derived from the Greek word for choking. If the pressure is on the lower part of the spine, the result is pain or numbness in the legs. If the pressure is on the upper part of the spine, the pain and numbness most likely will be in the neck and shoulders. People with more severe cases may have trouble with their balance and may have difficulty controlling their bladder and bowels.

Spinal stenosis is chiefly a degenerative disease that occurs with age. As we get older, the ligaments of the spine may thicken and calcify, and our bones and joints may enlarge. Stenosis can also be caused by a bulge of the intervertebral discs. There's not much you can do to keep from getting it.

The odds are you won't.

Spine surgeon Nicholas Shamie, a spokesman for the American Academy of Orthopaedic Surgeons, estimates that 1.2 million Americans have lumbar stenosis, the most common form. But there are 76 million Americans over 50, so if Shamie's figure is correct, only about 1.6 percent of seniors have this disease. Risk increases with age and is somewhat greater for women. Genetics plays a role. Some people are born with a more narrow spinal canal.

Risk is also greater for gymnasts, construction workers and others whose jobs or activities put stress on their spines. Although there isn't much you can do to keep from getting spinal stenosis, there's a lot you can do to ameliorate its effects.

Perhaps the most important is to lose those extra pounds.

"Being overweight doesn't help," said Jack Wilberger, chairman of neurosurgery at Allegheny General Hospital in Pittsburgh. "It certainly puts more strain on the spine and on the back. We are not currently aware of any other thing that would increase the risk of spinal stenosis."

Exercise can help keep the weight off and is a boon in itself. Exercise that strengthens supporting muscles, including those in the abdomen, can take some pressure off the spine.

Once stenosis has been diagnosed, "We treat conservatively with anti-inflammatory drugs and some physical therapy," Wilberger said. "That works for about 70 percent. When things get so bad people can't function in a reasonable manner, then surgery is an option."

He said that in general up to 80 percent who have surgery get good relief and another 10 percent get some relief.

But patients whose stenosis is more extensive, or who have other conditions, too, may require more complex surgery.

The number of complex spinal surgeries went up by 15 times between 2002 and 2007, according to a study published in the Journal of the American Medical Association in 2010. Some physicians -- including the lead author of the JAMA study -- think the risks of these surgeries outweigh the benefits.

Neurosurgeons at 30 hospitals nationwide are evaluating a device -- the ACADIA Facet Replacement System -- that could reduce those risks. Facet joints are small stabilizing joints located between and behind adjacent vertebrae in the spine. They provide about 20 percent of the twisting ability in the neck and the lower back. If they become inflamed, they can cause spinal stenosis.

Currently, if the facet joints are removed to relieve pressure on the spinal cord, vertebrae must be fused together to provide the stability the facet joints once provided. But spinal fusion permanently limits range of motion.

The ACADIA Facet Replacement System replaces degenerated facet joints with artificial ones, so spinal fusion isn't required for stability.

With this device, surgeons may be able to eliminate their patients' pain "while preserving their ability to bend and stretch," said Donald Whiting, vice chair of the department of neurosurgery at Allegheny General Hospital.

"As long as the disc in front is functional, you can retain your motion," he said. "This is very promising. I think it's pretty cool."

A clinical trial will be conducted over the next seven to 10 years.

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