Artificial Ligaments Offer Hope for Injured Knees

Injuries involving tearing of knee ligaments are as common as treacherous ski slopes and concrete-hard football fields. Until recently, the rehabilitation process was as predictable.

Besides the pain, patients faced the prospect of five to seven days in a hospital and six to nine months of recovery, often emerging with limited flexibility in their knees.

But now the introduction of artificial ligaments--strands of synthetic fibers--have shortened the healing process. They have also offered hope to thousands who had unsuccessful operations through the traditional method of reattaching the torn ligaments by using tendons from other parts of the bodies.

“They can (now) go home the same day and are off crutches in a week,” Dr. Marc Friedman said. “Because this is not a living tissue, you don’t have to wait for it to attach to the bone and heal. These ligaments can be attached with screws.”

Friedman, of the Southern California Orthopedic Institute at Valley Presbyterian Hospital in Van Nuys, is one of the principal investigators in the development of artificial ligaments.

From 1983 to 1986, more than 1,000 artificial ligaments were implanted at eight research sites throughout the country. Since the procedure was approved by the Federal Drug Administration in 1986, Friedman said, at least that many more have been inserted.

It is not known how long artificial ligaments will last in a knee, which Friedman said normally flex 1 million to 4 million times a year. But he believes that they might remain functional for up to 80 million flexes, or anywhere from 20 to 80 years.

Orthopedists have been attempting since the 1950s to use artificial ligaments. The traditional method was failing because sutures used to bind ligaments with scar tissue were not strong enough.

The artificial ligaments initially used also failed the test of time. Friedman said ligaments placed in knees 10 years ago do not work, but those implanted within the last five years have a chance.

The big breakthrough, he said, was the use of materials such as carbon, Teflon, Dacron, freeze-dried tendons and Gore-Tex.

Gore-Tex, a trademark, is a thick braided strand of synthetic fiber called expanded polytetrafluoroethylene, a durable material used in sutures, ski parkas, running clothes and foul-weather gear.

“With the advances in arthroscopic surgery, we have been able to work out some of the kinks,” Friedman said.

Arthroscopic surgery is performed to diagnose the extent of damage to the ligament. A fiberoptic cord that is connected to a camera is surgically inserted into the knee, and the image, multiplied 50 times, is projected onto a screen.

For implantation as an artificial ligament, an eyelet at each end of a six- to eight-inch piece of braided Gore-Tex is attached to the femur, or thigh bone, and the tibia, the major bone in the lower leg.

The artificial ligament is eventually incorporated with the actual bone.

The traditional operation--autogenous repair in which tendons are used to tie the ligament--has a 75%-80% success rate.

Friedman said the success rates for artificial reconstruction with five years of clinical use are comparable to those of autogenous repairs.

Specific success rates are still under discussion among researchers, and Friedman admits that the procedure does have a downside.

In some cases, the artificial material increases the synovial, or lubricating, fluid in the knee, restricting movement and causing discomfort.

Although the Gore-Tex ligament is restricted for use in patients who have had a failed surgical reconstruction, in the future it may become more readily available to other patients.

Friedman said the artificial ligament is not recommended for the professional or high-level athlete since it is known to break under excessive stress. It does offer an alternative, however, for many patients who function in everyday sports activities.