Replacing the irreplaceable in the knee Health: Animal-collagen implants show promise on preventing bone-on-bone damage of meniscus tears.


SAN ANTONIO -- Millions of Americans have undergone surgery to remove a torn meniscus cartilage in the knee, one of the most common injuries in sports. The long-term result of such surgery is often painful, degenerative arthritis in the knee.

Now, clinical trials are beginning at a dozen sites across the country to study a new procedure designed to help the torn meniscus re-grow. The new method uses a crescent-shaped implant made of animal collagen, the connective tissue found in skin, cartilage and bone. The implant acts as a "scaffold" to support the growth of new tissue.

A meniscus tear "is a very common problem in the NBA," said Dr. David Schmidt, an orthopedic surgeon and team physician for the San Antonio Spurs basketball team. "If you lose your meniscus, 10 years down the line if you continue to play competitive athletics, you may have a badly arthritic knee."

Schmidt repaired Spurs' center David Robinson's torn meniscus 1993. Spurs forward Charles Smith and former Houston Oilers quarterback Cody Carlson are among the players who have had a meniscus removed.

The meniscus is fibrous cartilage that acts as a shock absorber, protecting the knee from normal wear and cushioning the space between the thigh bone and shin bone. It also stabilizes the knee.

There is a meniscus on each side -- a C-shaped medial meniscus on the inside of the knee, and a round lateral meniscus on the outside.

When the meniscus is torn, surgeons try to stitch it back together, but usually the tear is too severe and removal is necessary -- since the tear can get caught in the knee and prevent the leg from straightening.

When the meniscus is removed, however, the lack of protection between the bones of the knee often leads to osteoarthritis years later.

Surgeons have tried transplanting the meniscus from human cadavers, but long-term results have been unsatisfactory.

After several years of studies in animals, the collagen implants have been used on a handful of people over the past two years. Clinical trials required for Food and Drug Administration approval are expanding.

But even participating surgeons are cautious.

Jesse DeLee, who is heading the San Antonio arm of the study, said it was not yet known whether the new tissue growth would be of the same shape and quality as the old.

"The fibers may be arranged at a different angle, and that can profoundly affect the function of the meniscus," DeLee said.

"If this is successful, I think it offers a good option," Schmidt said. "The downside is, it takes 15 years to know. Whether it affects their long-term outcome, we won't know for years."

Patients who undergo the implant will be on crutches for several weeks, compared to an almost immediate return to function for those whose meniscus is removed. In addition, implant patients will require follow-up biopsies and surgery.

The other question is whether insurers will pay for the implants, ,, which will cost more than simply removing the meniscus -- particularly with the long-term outcome still in doubt.

Patients who enroll in the study are not guaranteed to get the implants. They will "draw from a hat" to see whether they receive the implants or conventional surgery, Schmidt said. Surgeons will compare the results of the two groups.

Pub Date: 9/16/97

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