Artificial discs hold promise for back pain.

Byline: Tim Christie The Register-Guard

Karen McKim was in her mid-30s when a back injury from her days on the rowing team at the University of Oregon came back to haunt her.

A disc in her low back steadily deteriorated over the next decade until the pain became so unbearable that even walking was a struggle.

"I was in constant pain every day," said McKim, now a 45-year-old legal secretary in Eugene. "It was an effort to get through each day mentally."

She resisted the most common treatment for chronic low back pain - spinal fusion surgery - because she feared it would keep her from being active. Then last year, her neurologist told her to see Eugene spine surgeon Scott Kitchel, who was testing an artificial lumbar disc as part of a clinical trial.

In May 2003, Kitchel operated on McKim, removing her worn-out disc and replacing it with one made of titanium and polyethylene, a high-density plastic. Within a week, she was walking 1 1/2 miles as part of her recuperation. Before long, McKim was back playing tennis, biking, swimming and hiking.

Today, she said, she has an occasional twinge of pain, but otherwise feels great. "I am totally amazed with that surgery," she said. "It's given me my life back."

Artificial discs such as the one in McKim's back hold the promise of dramatic change in the way doctors treat the legions of people suffering from chronic low back pain.

Discs are fibrous, rubbery little cushions that act like shock absorbers between each of the 33 vertebra in the spine. They wear out, either from injury or the wear-and-tear that comes with aging, leading to pinched nerves, numbness in the arms and chronic pain.

The low back, or lumbar, consists of the last five vertebra and is particularly vulnerable to injury when twisting and bending because it acts as a hinge between the upper and lower halves of the body.

Spinal fusion surgery - when doctors remove the damaged disc and tie the two adjacent vertebra together with a piece of bone - is the most common treatment when more conservative approaches such as exercise, stretching and physical therapy fail.

About 250,000 people each year get spinal fusion surgery. While the operation addresses pain caused by a ruptured disc about 75 percent of the time, patients sacrifice flexibility. The removal of a single disc also puts extra stress on the adjacent discs. Think of how a car would drive if a shock absorber broke and instead of replacing it, the axle was welded to the frame.

"With fusion, you take away motion," Kitchel said. "This technology restores motion."

Discs used in Europe for years

Four manufacturers have artificial discs undergoing clinical trials, and federal regulators are expected to approve the first model, called the Charite, later this year.

The Charite is made by DePuy Spine Inc., a Johnson & Johnson subsidiary based in Massachusetts. It's been available in Europe since 1987 and implanted in an estimated 7,000 people.

A U.S. Food and Drug Administration advisory panel recommended approval of the Charite in June. But the expert panel asked that its manufacturer provide more information on the implant's safety in coming years.

For the past two years, Kitchel has been an investigator in a clinical trial for a competing artificial disc called the ProDisc, manufactured by Spine Solutions, part of a Swiss company called Synthes. Kitchel said the company asked him to be an investigator because of his participation in past clinical trials and his research and academic work. Kitchel holds an academic appointment at Oregon Health & Science University in Portland.

More than 5,000 patients in Europe have gotten the ProDisc since 1999, and the U.S. clinical trial began in 2001. Kitchel said he expects the ProDisc to be on the market within a year.

Kitchel, the lone Northwest surgeon in this trial, has implanted about 50 ProDiscs. He offers the disc as an option to patients with chronic back pain, meaning they've been hurting for at least six months. Patients who have had the disc implanted had an average duration of symptoms of 1.8 years, he said.

"Certainly I'm very encouraged by the results," he said.

Back pain widespread problem

Low back pain is a huge problem in the United States, afflicting eight in 10 adults at some point in their lives. It's the second-leading cause of lost work time and the second most common medical complaint - both after the common cold.

Experts estimate treatment of degenerated discs costs $60 billion a year in direct medical treatment, a sum that doesn't include lost wages and the cost of decreased productivity.

Kitchel likened the advent of the artificial disc to another dramatic change in orthopedic surgery.

Until the 1970s, doctors treating worn-out hips and knees would fuse the joints, addressing the pain but robbing their patients of mobility. Now, surgeons routinely implant artificial hips and knees.

Kitchel said spinal fusion surgery will always be appropriate for certain back injuries, but he expects artificial disc surgery to replace 30 percent to 50 percent of fusions in coming years.

The hospitalization and recovery times are shorter with disc replacement: Fusion patients usually spend three nights in the hospital vs. one night for disc patients. Fusion patients with physically demanding jobs don't return to work for six months; a disc patient with a similar job can be back at work in six weeks.

Disc replacement surgery will cost $30,000 to $40,000, when the shorter hospitalization time is accounted for, compared with $40,000 to $50,000 for spinal fusion, he said.

But not all experts view artificial discs as the next big thing in back care.

Dr. Rick Deyo, an adult medicine physician at the University of Washington Medical School in Seattle and a leading evidence-based researcher of low back pain treatments, counts himself as a skeptic.

"I'm skeptical only because we've had a century of breakthroughs in treating low back pain, but we still have plenty of low back pain," he said. "I'm not sure all of our advances have made much of a dent."

It's not clear how the discs will work over the long term.

The early generation of artificial hips and knees, he said, "were disasters."

"It took years until they developed models that were safe and effective," he said. "My worry is we could experience the same thing here."

Dr. Dilip Sengupta, an orthopedic spine surgeon at Dartmouth-Hitchcock Medical Center in Lebanon, N.H., said artificial disc surgery also poses significant short-term risks in those few cases when something goes wrong.

"It's extremely dangerous to retrieve the disc," he said. That's because disc replacement surgery is done through the abdomen and involves moving the two biggest vessels in the body, the aorta and the vena cava, away from the spine. It's not that difficult when the disc is inserted, but the soft tissue in the abdomen gets scarred after the first surgery and becomes difficult to move.

"The risk is absolutely unacceptable," he said.

Doing spinal fusion to fix the problem is difficult as well because the artificial disc gets in the way and keeps the vertebra from fusing together, he said.

Surgeons go in through the front

Last week, Kitchel did three artificial disc surgeries in one morning at Sacred Heart Medical Center in Eugene. Patient No. 2 was Jeff Roth, a 38-year-old Eugene police detective with a herniated disc.

General surgeons help on these surgeries because doctors get to the spine through the abdomen, not the back. So general surgeon Charlie Stanton began the procedure by making an incision below the bellybutton and carefully moving blood vessels and internal organs away to give Kitchel access to the spine.

Once the vertebra and disc were exposed, Kitchel went to work. He made frequent use of a fluoroscope, a high-tech X-ray machine that produces pictures instantly on a monitor in the operating room, to check his bearings and make sure he was placing the disc in the right spot.

He first performed a discectomy, using big pliers, a chisel-like tool and a knife to scrape, gouge and pluck out the degenerated disc to make room for the artificial disc.

The artificial disc is like a sandwich, with two titanium plates surrounding the polyethylene disc in the middle.

He placed a tool to hold open a space between the two vertebra, then wedged two titanium plates with teeth-like fins into the vertebra. He then placed the high-tech plastic disc between the plates and took another picture to check the fit.

Kitchel removed his tools and turned the operation back over to Stanton. The whole surgery took about an hour.

Roth said he hopes the artificial disc gives him the same kind of relief it gave McKim. He said he's had back problems for about 10 years.

"It affected just about every aspect of my life," he said. "It's just constant pain you walk around with. I've used a lot of sick time because I couldn't get through the day."

Like McKim, Roth didn't want spinal fusion because it would limit his mobility. He did some research on the Internet and learned about artificial discs.

"It just seemed like a great idea," he said. He decided the potential for long-term pain relief was worth the risk of having a device still under investigation.

Roth was back home two days after the surgery and still hurting. But he was walking around and looking forward to the day when the new disc will allow him to resume doing the simple activities he enjoys, like playing with his kids and working in the yard.

"Hopefully, I just don't have any more pain," he said, "and I can get some enjoyment out of life again."

CAPTION(S):

Orthopedic surgeon Scott Kitchel holds a new artificial disc for the lower back. He's been installing these devices as part of a clinical trial for about two years.