By Tom Keppeler, Knee1 Staff
Two knee-related questions spark a hot debate in the orthopedic community. First, both surgeons and researchers have noticed that women injure their anterior cruciate ligament far more than their male counterparts, but as of yet have no definite explanation. Secondly, while many doctors contend that some tears in the meniscus, the shock-absorbing cartilage pad in the knee, that extend in to the central portion cannot be repaired, others claim that they can with high rates of success.
Dr. Frank Noyes believes he may have the answer to both questions. The first question led Noyes and his staff at Cincinnati Sportsmedicine and Orthopaedic Center to investigate why women were at such a high risk for ACL injury. To combat this risk, Noyes and his associate designed an intensive strength-training program known as Cincinnati Sportsmetrics to better balance the muscle strength of women's legs and, therefore, reduce the risk of ACL injury. Noyes has also pursued a novel approach for the second problem—by using a different suture technique, he says, a doctor can repair a meniscus with a tear extending into the avascular zone, not just remove it.
Dr. Noyes is president of Cincinnati Sportsmedicine and Orthopaedic Center and the Cincinnati Sportsmedicine Research and Education Foundation. He has served as team physician for the University of Cincinnati athletic teams and consults for a number of college, professional, and Olympic programs. He serves as a professor in the Department of Orthopedic Surgery and the Department of Aerospace and Mechanical Engineering at the university. Dr. Noyes graduated from the University of Michigan Medical School in Ann Arbor and is licensed in Ohio, Michigan, and Kentucky. Dr. Noyes is also team physician for the National Football League's Cincinnati Bengals.
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Knee1: What makes women so susceptible to ACL injury?
Dr. Noyes: There are several theories out there. We have focused on two in particular because we can do something about them. The first theory is lack of sufficient muscle strength in the hamstring and calf muscles. That has now been shown in a number of studies, and we have seen a lot of women come in with a quadriceps-to-hamstring ratio of 40 percent, whereas the number should be more like 60 to 70 percent, as it is in males. There are many different suggestions as to why the female hamstring strength is weak. Doctors have wondered whether female athletes are doing different conditioning exercises for years and years than their male counterparts. The positive side is that we can alter that through the Sportsmetrics program. It takes a good six to eight weeks to do this. Many women go through the program twice, and end up with beautiful control.
The second theory on women's injury is a coordination issue. There is no question that there are differences in how the muscles are coordinated in the lower extremity. We just presented a paper that shows that when women jump, they not only put their Anterior Cruciate Ligament at risk, they also come down into a knock-knee position. Again, Sportsmetrics addresses that issue by teaching better coordination. Part of the program is a 30-minute risk analysis that an athlete goes through. The important part is performing what we call the "sports-injury test." Besides jumping balance and the knock-knee position, we look for ankle problems, coordination problems, and, very importantly, any prior injuries the athlete may have endured. The other theories, which deal with jumping posture, jumping technique, the width of the pelvis, anatomical differences, estrogen differences—many variables that may play a role. For right now, we are concentrating our efforts on the ones mentioned earlier. The top two that everyone agrees on are muscular strength and coordination.
Knee1: How did you develop the Sportsmetrics program?
Dr. Noyes: We have a lot of good female athletic teams in this area. The program came out of an observation we made 10 to 12 years ago that, when women jump, they tend to jump with what we call the wiggle-wobble position. We have always had an equal male team to female team ratio. We also noticed when we did strength tests on these athletes that many of them had abnormal results. That led to our first test, which we won an award for six or seven years ago, where we took a group of female athletes into the laboratory and analyzed their gait. We showed for the first time the abnormalities that are present in females when they jump, and secondly, that a conditioning program would work.
We did a study with high school athletes in which we had a group that went through the Sportsmetrics program and a group that did not—a total of 1,263 male and female athletes who we tracked throughout the course of a year. The study showed a higher incidence of injuries in the female athletes who were not trained. Although we tracked a large number, we really need to have thousands and thousands of participants. We consider that a pilot study. Part of what we are doing right now is hooking up different research sites across the country and tracking the athletes to increase the size of the database. We now have a dedicated group of six individuals from trainers to a Ph.D. that represents the largest sports-injury preventative program for female injuries in the country. It is difficult stuff, but, fortunately, we have had a lot of feedback from schools that have had adopted the program; some have had it for two or three years and are continuing to show very low injury rates.
Knee1: Let's talk about the meniscus. Could you explain to our readers what its role is in the knee?
Dr. Noyes: I think the readers of your site know how important the meniscus really is. It obviously is the important shock absorber of the knee, and it has been well-appreciated that if you lose the meniscus, you concentrate the force in the joint by three to four times. If you then add upon that athletic activities, you now have large forces across the knee. People realize now that, in terms of sports activities, an athlete can put anywhere from four to eight times his or her body weight on the knee joint without a healthy meniscus. What happens then, if you lose the meniscus, you are definitely at risk for arthritis and deterioration in that joint. The second very important part of that problem is that if you are bow-legged or knock-kneed, you tend to concentrate the pressure on one side of the joint or another, so now you have a second doubling that occurs. I am commonly asked by my patients if they lose their meniscus whether they will inevitably end up with arthritis. The answer is that at least 50 to 60 will percent have some symptoms of arthritis at the 10- to 20-year mark. Obviously, much of that has to do with the integrity of the articular cartilage (the cartilage that surrounds the joint). We all are born with a certain integrity, or strength, of articular cartilage. There is a genetic factor, there is an alignment factor, there is the type of athletics that we do, but the bottom line is that we want to preserve the meniscus.
Knee1: When did your facility start repairing, as opposed to removing, complex tears of the meniscus?
Dr. Noyes: We started repairing these complicated meniscus tears in the early 80s. Dr. Charles Henning should be credited with teaching many of us in the United States how to do these repairs using multiple sutures to put the meniscus back together. We have credited Dr. Henning, who has since passed away, as being one of the leaders, one of the pioneers, who taught many of the leading surgeons in the United States. Dr. Henning visited us in the early 80s. He was a friend of mine. We have had a large experience with meniscal repair, and we published our first paper in 1991. That paper showed two things: first, that you could repair a meniscus along with an ACL and use immediate motion. At the time, many surgeons were worried that they would have to restrict motion in the knee that they repaired the meniscus in.
We know now that, with an ACL repair, we have to move that knee immediately so that the patients do not get arthrofibrosis. In that initial study in 1991, about one-third of the patients had tears that extended into the "avascular zone." It is important for your readers that we define that. Most people divide the meniscus into thirds. Everyone is going to repair a meniscus in its outer third. It has a good blood supply, it is close to the periphery, it has a high rate of healing; our study showed that repairs to that area had a 98 percent success rate. That is not new. Many people have shown that. On the other hand, we all know that we would not repair a meniscus damaged in the inner third. It has a very poor blood supply, we would not subject our patient to the added time of recovering from that.
We are now left with, for example, a tear that starts in the outer third and becomes complex, meaning that it goes in more than one plane, and maybe extends into the avascular zone. It may not be a perfectly clean tear; it may have a little bit of a ragged edge. The important part of it is that, if you remove that tear, you have essentially done a meniscectomy, because you have left very small portions of the meniscus, maybe 2 to 3 millimeters. If that is the case, surgeons are very reluctant—even today—to repair that, because it takes added time, an added assistant, and a different technique than what is commonly used. You cannot use arrows or meniscus fixators. We liken the tear to a laceration of the skin, in which you have to use multiple sutures—what Henning used—that are called "vertical divergent sutures." Rather than being horizontal, they are in a vertical direction so that they can trap a good portion of the collagen, which is going in a loop configuration. These types of sutures give the repair great strength. We commonly will use six to eight sutures along the top, and then we will use inferior sutures that also close the gap. When the meniscus repair is done, we want it to look like a skin incision. We want it to be as good a repair as you can do, and we want both the superior and inferior tears closed. To do that takes one additional thing: you have to make a small incision into another part of the joint to tie the sutures across the meniscus bed. It is a very meticulous, careful suture technique.
Knee1: Why can't you use meniscus fixators?
Dr. Noyes: In this type of tear, you need the added fixation strength both superiorly and inferiorly to close that gap. Whereas most orthopedic surgeons may know that a fixation device can be used when the tear is close to the periphery, in this case, a surgeon must really "lace in" the sutures both superiorly and inferiorly. A paper we published in 1998 represents the largest series that has been reported. It went from 1982 to 1995 on 198 consecutive meniscus repairs. The important part of that study is really determining whether a patient will have symptoms after the operation. Orthopedic surgeons need to advise patients, particularly younger, athletic patients that if they are trying to preserve the meniscus that this is a viable option. As an example, we had 92 patients who had tears in the avascular zone that were 4 to 6 millimeters from the rim. Instead of excising the meniscus, we repaired it. In that group, we had a re-operation rate of 12 percent. That rate is pretty low. Alternatively, you could say that we had a success rate of 88 percent.
The more interesting group is the patients with two tears, a double-longtitudinal tear. Now, you might expect the success rate to go down, and, in fact, it does, but, importantly, it only goes down to a 22 percent re-operation rate. That means that a 15- or 20-year-old athlete who has this double-longtitudinal tear with otherwise good tissue could expect a 78 percent success rate.
The second benefit of the study is that in many of the patients who needed a second operation, about 50 percent sustained a second knee injury. They were asymptomatic for three or four years until they had another twisting knee injury. Does that mean that the meniscus may, in fact, not gain its full strength? Yes, I think it may. But, on the other hand, perhaps the re-injury was also a significant factor. We would like to think that we are preventing meniscectomies in a large group of patients. I think our data would show that. What we cannot say scientifically is how much function a damaged meniscus may provide, because it has to undergo some degeneration once it's injured. We suspect it will provide some function and we expect that function to be much better than with a total removal. But we need to be able to measure it, and, unfortunately, we do not have any criteria now to measure it. We have obtained M.R.I.s and they show that the meniscus has attained a satisfactory position inside the knee joint, but we cannot measure the shock-absorption effect after the meniscus repair. No one has that ability yet.
Knee1: Is it not recommended, then, that athletes return to the same level of activity after the repair?
Dr. Noyes: We have been allowing them to. If we get a good repair, we obviously caution them, but we have not restricted them. The alternative is this: if you have a complex meniscus tear that you excise, then, very definitely you must advise them that the joint may be at added risk.
Knee1: What do you expect we will learn about the meniscus in the next few years?
Dr. Noyes: We have many fellows that come from different programs throughout the United States. We always ask them whether people are repairing these complex tears that extend into the avascular zone in their community. In 90 percent or more, the answer is no. Why not? I guess it is still relatively new concept that the surgeon can get a pretty good repair. We actually state that the meniscus repair is just as important, if not more so, than the ACL. You must double the length of your procedure and make a second incision. You must also have another person come in who has got to catch the sutures. Everything is going to be delayed because of meniscus repair. We think that there will be a learning curve in the orthopedic community to have the available resources to do that. We feel now that the scientific data is there to show that the doctor should perform the repair in the athletically-inclined individual. We are not going to get into the argument of whether we should do it in a 40-year-old or 45-year-old. Right now, we do it in everyone. If we have a suitable meniscus of good tissue, where we can perform a stable repair in 30 to 40 minutes with a more than 80 percent success rate. We are pushing the envelope, but right now, a reasonable word would be to say it is just being explored in the orthopedic community.
Knee1: Where do you expect research on the meniscus to go in the next five years?
Dr. Noyes: Our direction of research right now is in meniscus transplantation. We have performed more than 160 meniscus transplants from cadavers. The meniscus transplant offers a suitable alternative for patients in their 20s and 30s who have lost the meniscus. The problem is that we do not know how long a meniscus transplant will function. Because it is somewhat unpredictable, it has made us push the curve more toward repairing the meniscus, and try to avoid the meniscus-transplant business. When we now look at the arthroscopic pictures of a number of younger individuals in whom we did transplants that we would have performed a repair of the area with what we know today. Also, a majority of insurance companies do not cover meniscus transplantations, because they incorrectly believe it is experimental. It is not experimental, it does have a track record, even though the studies have been short-term. We are spending a great deal of time with bioengineering to find a suitable collagen construct for meniscus transplantation, and we are also involved in the cellular regeneration area. In the future, we believe that we will have a implant a collagen meniscus with a patient's cells on it into a patient's knee and have the patient re-grow their own meniscus. I think that may be as far as 10 years away, however.
Knee1: Does this work involve stem cells?
Dr. Noyes: Our approach right now is to use stem cells. We have been involved in stem-cell research for the past five years. We have done work with stem cells for tendon and ligament healing. The question that we are addressing right now is whether it will be a stem cell for a fibrochondrocyte or whether we should make it a chondrocyte. We do not have the answer to that question yet.
Knee1: Have you paired up with any big research facilities to perform this research?
Dr. Noyes: The two groups that are doing this are Cincinnati Sportsmedicine and Orthopaedic Center and the College of Engineering at the University of Cincinnati.
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