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Patients' cells used to regrow cartilage in damaged knees

Dr. James York, orthopedic surgeon at AAMG Orthopedic and Sports Medicine Center, a practice of Anne Arundel Medical Center.
Dr. James York, orthopedic surgeon at AAMG Orthopedic and Sports Medicine Center, a practice of Anne Arundel Medical Center. (Courtesy of Anne Arundel Medical Center, Baltimore Sun)

In place of traditional knee replacement, doctors at Anne Arundel Medical Center have been using patients' cells to help repair their damaged cartilage. The cartilage knee replacement, where cells are implanted and grow into the damaged space, is the longest-lasting fix for younger patients who don't have arthritis, said Dr. James York, an orthopedic surgeon at AAMG Orthopedic and Sports Medicine Center.

How does a cartilage knee replacement work?

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Autologous cartilage implantation (ACI) is a two-stage procedure. The first stage is a minor cartilage biopsy, where a small piece of the joint cartilage is harvested from a part of the knee that does not bear weight with arthroscopy. The small sample — about the size of two Tic-Tacs — is sent to a laboratory, where it is cultured and grown into about 16 million "baby" cartilage cells.

In the second stage, about two months following the first procedure, the surgeon does an open surgery to implant the new cells. First, the damaged cartilage is cleaned out. Then the new cells are put into place, secured with a special membrane sewn over the defective area. Within six hours, the new cells cling to the damaged area and begin to grow. The new cells continue to grow, eventually filling in the damaged area in about three months.

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Who are candidates for a transplant?

You're an ideal candidate for ACI if you have cartilage damage the size of a nickel or larger; are under 40; do not have arthritis; and have healthy surrounding cartilage.

How long has the method been used and how common is it?

ACI was U.S. Food and Drug Administration-approved and has been in use in the United States since about 1994. This procedure is not done as frequently as knee replacement, since it is for younger patients who have cartilage injuries or defects in knees that are otherwise normal. ACI is not effective for the treatment of arthritis.

What are the benefits and drawbacks compared to other repair methods?

ACI has been proved to be the longest-lasting repair of a cartilage defect with cartilage that is closest to your own native joint surface cartilage. It does require more care, "down time" and prolonged rehabilitation compared with other techniques. Patients are using crutches for four to eight weeks with minimal to gradually more weight-bearing over time. The knee needs to be protected from pounding and hard twisting motion for several months. Patients are doing physical therapy and progressive home exercises for five to nine months. Microfracture techniques require the least amount of rehabilitation but do require four to six weeks of use of crutches but are useful for relatively small defects and the benefits last about one to three years. There are many newer cartilage transplant techniques that are being used for small to medium-size defects that are very promising and may give more lasting results with less initial down time.

After the cartilage regrows, does the patient have any limitations?

Complete healing takes several months, but patients should return to near pre-injury status, allowing them to return to a normal lifestyle. Once a patient is about a year out from surgery, the cartilage repair has matured enough to permit full activities without restriction.

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