By Neal Patel, Knee1 Staff
“Our goal is to recreate the structures of the knee that protect it from impact and provide stability.” With the aid of new technology and advances in medical science, Dr. Richard Steadman is well on his way to achieving this lofty goal. Dr. Steadman has already devised an effective technique, known as microfracture, that stimulates regeneration of articular cartilage. In addition, he is also in the midst of perfecting another product, known as the Collagen Meniscus Implant, which allows for meniscal cartilage regeneration. However, Dr. Steadman is quick to note that the surface has just been scratched in regeneration technology, as the potential for improvement in treatment through the use of growth factors and stem cells is immense and seemingly limitless.
Dr. Steadman received his medical degree from the University of Texas, Southwestern Medical School in Dallas and trained in orthopedics at the Charity Hospital in New Orleans. In 1988, Dr. Steadman founded the Steadman Hawkins Sports Medicine Foundation, a non-profit institution whose overall goal is to “[keep] people active through research and education. Presently, Dr. Steadman is Chairman of the Medical Group at the Foundation and a member of the Sports Medicine Committee for the U.S. Alpine Ski Team.
Knee1: You developed the technique known as microfracture, could you describe it?
Dr. Steadman: Microfracture is a technique that involves making multiple fractures in the joint surface to stimulate regeneration of articular cartilage in a defective area. The procedure is used if we identify a full thickness cartilage defect on the knee joint surface. One of the major requirements for the procedure is that the patients have good joint alignment. If a patient has bowleg, knock-knee or a similar condition that puts excessive pressure on the side of the knee where we are trying to regenerate the cartilage, then it may be necessary to do an osteotomy to change the angle of the bone. However, most athletes do not have that problem, as osteotomies are more popular in patients over forty-five years old.
The current procedure involves creating a bed from which the cartilage can grow. Preparation of the bed involves removal of the deepest layer of cartilage, which consists of the calcified cartilage layer. Research in horses has shown that preparing the bed in this manner enhances cartilage regeneration. In addition to preparing the bed, it is also extremely important that a stable edge is created around the defective area. Flaps of cartilage over the defect tend to discourage new cartilage from forming.
After creating the stable edge, we make multiple fractures in the bone using a curved awl. The awl allows us to break the subchondral bone but leaves the subchondral plate in tact. Most people involved in cartilage research feel that the subchondral plate is an important part of the functioning of articular cartilage and so it is better to leave the plate in place. By using an awl with different curves, we can come in with a 90-degree angle; an orientation that gives us our best chance for regeneration. By making these tiny fractures, we allow stem cells (undifferentiated cells that can form any tissue) and growth factors from the bone marrow to be released and coat the bone surface. These stem cells then regenerate the defective area of cartilage.
In the past, we used to drill these holes rather than using an awl. Drilling was ineffective for several reasons. First, it didn’t allow us to fracture the bone at the correct angle; the curve on the awls corrected this angle problem. Second, the drilling left a smooth, polished surface that didn’t promote sufficient adherence of the new cartilage to the bone. Using the awls, we get a rough surface to which the cartilage more effectively adheres.
Knee1: How did you develop this procedure?
Dr. Steadman: Microfracture is actually a combination of other procedures that have been done in the past, and I identified some mechanical aspects that we could do that I thought would enhance procedures that already used bone marrow to form new cartilage. At first, it was just a technique to make little fractures in the joint surface to make the joint think that it had been recently injured. As we progressed with our research, we felt that we had to improve on the need for a long rehabilitation time. Research in horses showed that this tissue takes at least eight weeks to become firm tissue that can stand up to stress. Over the 16 or 17 years that I have been doing the procedure, we have enhanced the technique through what we have learned through research. Today, we have a procedure that is about 85 percent successful in returning patients to their normal or near normal level of functioning.
Knee1: What type of rehabilitation is involved with the microfracture technique?
Dr. Steadman: For a long time we have known that cartilage needs time to mature before it is ready for heavy, impact activity. As a result, patients are on crutches for eight weeks after the procedure. However, we also believe that the new cartilage benefits from smooth motion. It is our feeling that the mechanical stimulation that we get through smooth motion gives the stem cells a message that aids in the overall signal causing the stem cells to form cartilage. Therefore, we try to create situations where we have very little impact on the new-forming cartilage, but a lot of smooth motion. This includes stationary bicycle and deep-water exercise.
Knee1: You have taken cartilage regeneration to the next level with your new Collagen Meniscal Implant (CMI). Could you describe that project?
Dr. Steadman: The Collagen Meniscal Implant is another important project that we have done. I helped found and am partial owner of the company, Regen Biologics, Inc., that is developing the CMI. When we started the project, I was the sole source of funding; however, it soon became clear that I couldn’t possibly provide all the necessary funding, so we formed the company.
This technique involves a collagen replacement for the meniscus cartilage that is sewn into the place of the defective meniscus similar to meniscus transplantation. However, in this case, the implant serves as a template for regeneration and the body grows cartilage directly into the implant. Over time, the implant is absorbed and the patient is left with a newly regenerated piece of meniscus.
One major advantage that we feel the implant has over a transplant is that the tissue that re-grows is softer. A lot of times with the meniscus transplant, the transplant contracts and becomes very stiff. Unlike the transplant, the regenerated cartilage remains soft in the joint. Another advantage over meniscus transplantation is that the implant can be used for a defect that is relatively small in size. With the transplant, you have to remove most of the meniscus rim to reattach the transplant meniscus. However, with the implant, you can take a small defect, as small as three to four millimeters, and simply fill the defect with the implant. A final advantage over the transplant is that with the implant, you don’t have to worry about issues of tissue rejection.
We have been doing this procedure for about seven years now. It was released for general use in Europe in February, 2000 and it is currently under an FDA protocol in the United States. The initial results in Europe have been very promising. The implant stimulates significant cartilage regeneration in most cases and it appears that the new tissue is soft enough to show clinical improvements in patients. In analyzing results, we have two different groups. In patients with fresh injuries, you don’t see much difference in results between patients that had menisectomies and patients that had the implant because the negative results of menisectomy don’t show up for a long time. However, if you look at patients who have the implant done after not experiencing improvements from a menisectomy, a dramatic increase in clinical improvement is seen.
Knee1: What do you see in the future for cartilage regeneration?
Dr. Steadman: There are several areas for advancement in cartilage regeneration. One area involves growth factors. There are a lot of growth factors in the body and we believe that in cartilage regeneration, a cascade of growth factors is involved. Rather than simply one growth factor being in control, different growth factors are needed at different times during the process of regeneration. There is definitely a real potential for elucidating this cascade. Another area involves provision of stem cells or cartilage cells that can become the new cartilage. Currently, in the microfracture technique and other similar procedures, we must rely on bone marrow as the source of cells. If we can create a situation where more cells are available, particularly the stem cells that can become anything, then we probably can enhance the cartilage regeneration. It’s not that the marrow using techniques are ineffective. We are definitely getting good results from these procedures; however, our goal is to get perfect results.