Expanding Understanding of the Labrum and Chondrolabral Junction

In this video, Scott D. Martin, MD, director of the Joint Preservation Service within the Department of Orthopaedics Sports Medicine Center at Massachusetts General Hospital, discusses his research into the labrum and the chondrolabral junction of the shoulder. Dr. Martin discusses how preclinical models are shedding new light on joint cartilage production and function, and details a novel approach to labrum repair and reconstruction.

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Transcript

Our other research is using animal models. We're mainly using a caprine model, which is goat, and what we wanted to look at was, not only the labrum, where there's been histology studies on the labrum, but also on the chondrolabral junction, and that's where the labrum joint, the articular cartilage where there's usually a seamless transition from the articular cartilage to what we thought was just fibrocartilage of the labrum. When we're doing our surgery, for patients who have over coverage of their cup, they might have a cup that tips down a little bit, we try to trim back that cup, so it doesn't pinch as they flex their hip up and tear their labrum. And when I was doing that surgery, I noted that there was a lot of elasticity at that chondrolabral junction, where the labrum comes over the edge of the cup like a fish mouth, joins the inside of the coating of the cup, the articular cartilage, and, much to my surprise, there wasn't any elastin there at all.

In the caprine study that we did, we did over 12 goats. After necropsy, on the histopathology, we found a very unique type 1 loose crimped collagen that has never been described in joints before, and it makes perfect sense once we discovered it, that you would need a type of collagen that holds up well under the rigors of just daily living. If you just pivot your body to turn on a light, you're putting a huge amount of sheer force right through that area and so once you see it and understand that there has to be something more than elastin, which probably, like a rubber band, will wear out over time, the type 1 loose crimped collagen was that perfect solution where you think in your head, "I wish I thought of that."

I think that that this gives us promising hope to continue the research that we're doing in the future, again, translational—from doing it in the lab in animal studies and then taking it to the clinical studies. We are also working with Jenna Galloway of the Centuries Research Group and using zebrafish, which Jenna will take bone marrow aspirate that we send to her, that includes mesenchymal stromal cells, and she will do aliquots of that with testing, using different assays with different chemicals. Now we're trying to test with organic materials, such as proteins and enzymes, to stimulate the zebrafish to form cartilage. They glow a certain color once they're forming cartilage, and that will be the next step in the future, to hopefully not only healing and preserving damaged cartilage that's there, but absolutely regenerating new cartilage.

You can use a remote graft, such as from your iliotibial band, or you can use semitendinosus or gracilis tendons to make a new labrum. We found problems with that. Number one, it's from a remote site, so when you try to put that into the hip and make it congruent where it has to be within 1 mm or less with no gaps, otherwise, it's equal to having a labrectomy, where you've taken out your labrum. We find that very challenging. One is that you get most likely an out-around repair, where you have a, instead of it being perfectly round, it's a little bit cupped and then gaps underneath the labrum.

The second problem is, to put that in, I have to take the rest of the patient's labrum out, which can damage that chondrolabral junction, because after labrum comes that unique histology that we talked about, that type 1 loose crimped collagen and that's the junction that we don't want to lose, and the reason why as stated, we don't know how to heal that area. So, it's like throwing the baby out with the bathwater, if I got to take more labrum out and sacrifice that chondrolabral junction, I'm afraid I'm not doing what I need to do to repair that area.

So what I've been doing now for about the last nine years is doing a capsular autograft reconstruction of the labrum, where, if a patient has a deficient labrum, we try at all costs to maintain what they have as far as residual tissue, and then I will go up above the labrum and harvest about 7 mm to 10 mm of their own capsule and bring it down and augment their deficient labrum, effectively making them a new labrum.

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