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A Joint Exam

Part 2 - Stabilization Test

Lee Ann Brady, DMD
Dr. Brady discusses and demonstrates a stabilization test.

One of the next things that we talked about on the other video on joint diagnosis was something called the stabilization test. It's a really important way for patients who have discomfort on range of motion. So when we do a range of motion study, they tell us it's uncomfortable in one direction or more than one direction. It's going to be really important to see if I can differentiate between is that coming from muscle or is it coming from the joint space. So we do a stabilization test. How do we do that? I wanted to show you that in actual clinical practice. So what I'm going to do is I'm going ask Katie to bite her teeth together and clinch lightly. Now Katie I'm going to actually ask you to try and move your jaw to the right. I don't want to have you actually move. I'm going to actually hold your jaw with pretty firm pressure to give you something that's sort of work against. Ready. All right. So try to move right. And that's all there is to it. Now I can feel underneath my hands all of Katie's muscles firing. You could see visually her mandible didn't go anywhere. That's exactly what we want to accomplish in the stabilization test. So if we think about what's going on, if I actually ask Katie to move to the right, so can you move your lower jaw all the way to the right, okay, and then back. Okay. When she moves to the right actually two things are happening. Her muscles are firing in particular her lateral pterygoid muscles are having to fire to move her condyles. And so now let's think about what's happening there. If she's moving to the right so the right side is the working condyle, it's simply rotating. Her left condyle is translating. So that's how she's making a right movement. And she says I have pain when I do that. What I want to be able to isolate is that pain coming because as she's rotating or translating she's pinching retrodiscal tissue. She's got something going on in the joint space or is that pain coming from those lateral pterygoid muscles. When I do a stabilization test, when I asked her to move because she's trying to move against the resistance of my hands, she fires those muscles. Yet because she's not actually moving nothing is changing at the level of the condyle-disc assembly. Therefore during the stabilization test if she says, yup, the pain is still there. It feels just like when I actually moved. Where my head goes is that it has to be coming from muscle probably the lateral pterygoid cause her muscles are still working. If she says, nope, I didn't hurt at all when I tried to move but didn't during the stabilization test but I actually have her moved and she's like yup there's that pain when I actually move. Now I'm thinking something is happening in the condyle-disc assembly on whichever side she has the discomfort she's able to pinch those tissues that's where she has that discomfort. So the first piece would be that I would have to do a range of motion test. One of the things we do is we'll actually just use some kind of a device. This is actually a range of motion measurement device from Great Lakes that's disposable. So what I like about them is that you just literally throw them away when you're done with them. You don't have to sterilize them. And we're going to measure maximum opening. I said earlier that somewhere between 35mm-60mm. We're going to measure right and left protrusive. And if on those movements she had reported some discomfort, we then do that stabilization test. Now if she had absolutely no discomfort on a range of motion, she doesn't report any discomfort in eating or chewing or the normal functions of her daily life, I don't need to do that stabilization test. Another important part, as we go through our joint exam and the piece that will help me differentiate between joint issues and muscles issues, is what we called a load test. So doing a load test, there's a lot of different ways to doing a load test. And in the prior video I show doing a load test actually using bimanual guidance or bilateral manipulations so using my hands on the mandible to load the mandible. One of the things that I like to do and another way to do is to use a leaf gauge. And so, thank you Crystal, if you're not familiar with a leaf gauge a leaf gauge is literally just a whole sheet of 0.1mm pieces of plastic that have been held together by a pin and a leaf gauge is really design to help us seat the condyles in centric relation the most anterior medial superior position and get the muscles to release to see what that position is like. And so I'm going to actually use a leaf gauge and demonstrate doing a load test with a leaf gauge. So Katie I'm going to put some gloves on behind you. So the leaf gauge is, by the way while I'm putting my gloves on, are sterilizable. So you can get them and once you use them what you want to do with them is throw them in cold sterile. It's really important that they're completely dry before you use them or the leaves kind of stick together. So we actually dry them out before we bag and then sterilize them. So, now the trick as we get started with this leaf gauge for a load test is that I would Katie's posterior teeth to be apart. I want her only occluding on the anterior segment on where the leaf gauge is. But I don't want her back teeth to part by mile. I don't want to be able to drive a truck through her back teeth. I want her just far enough apart that I know I'm not going to get any posterior interference and we can make sure that we only have anterior tooth contact. So the first piece of this is just going to be the test how much do I need. People who have very deep bites typically are going to need fewer leaves probably to separate them as much as you want. So we're just going to play and see what we need. So what I'm doing is just randomly selecting a number of these leaves. We're going to ask Katie to open. I'm going to put it on her front teeth and I'm going to ask her to bite together and I'm going ask her to push her lower teeth forward and pull all the way back and now Katie are feeling anything touching the back. No. Okay. And I am going to look and make sure that I have clearance. Do you have a mirror, Crystal? And I've got probably about a millimeter of space between Katie's second molars. So now we're going to go ahead and do the leaf gauge. So Katie what we're going to do with is we're going to actually put this in. You're going to push your teeth forward, pull back and squeeze. And I want you to tell me if you feel anything up here in front of you ears. Okay. Bite together. Push your lower teeth forward. Pull back. Lightly squeeze. Do you feel anything in front of your ears? No. Okay. So that would be a negative load test. She said no I don't feel anything. When I hear that the first thing that I want to do is I want to now actually have her hold this in place about 30 seconds. Why? Because typically in just a second we may not have the time to get the response that there's actually something going on. So I'm going to actually have her hold this and see if she felt anything. So now bite together for me Katie and push forward and pull back. And I want you to hold that for me. And I want you to just let me know if you start to feel anything in front of your ears. And I'm just going to count to 30 seconds in my head. I'm actually not doing that right now cause I'm talking to you all. But I would typically would be counting off and waiting to see when my 30 seconds are up. And really part of that is if she's pinching retrodiscal tissues it can take a moment before she gets that response. If she has fatigue in the lateral pterygoid, it can also take them just a moment before they're going to actually respond to her. So Katie any change? Yes. So what were you feeling? A 1 or a 2 on my right side. Okay, so what it actually tenderness? Is that how you would describe it? Just slight. Okay. So you can see how we waited those few seconds and now Katie actually got some tenderness on this right hand side. So now in reality we have a positive load test. What does a positive load test tell us? Well it tells me either she has a lateral pterygoid on this right hand side that's contracted from holding her mandible forward into her intercuspal position and the leaf gauge is trying to seat her condyles into centric relation and that lateral pterygoid is saying I don't think so. I'm used to being in this particular position. If that's the case, what would I not do with this appointment? I wouldn't want to get bite records that I believe to be in centric relation to do diagnostic cause they wouldn't be accurate. I need to do something to get those muscles release prior to getting those records. What else could it be? It also could be that she's actually pinching retrodiscal tissue on this joint and by loading that joint because her back teeth are out of contact she's now getting a response from that tissue cause there's inflammation there. Now again I said it's about putting puzzle pieces together. In Katie's case her retrodiscal palpation was negative. She had inflammation in that joint I would expect that she would have a positive palpation even minor. She also had no palpable joint sounds. In order to pinch retrodiscal tissue I would be wondering if she was off the disc and so far there's no evidence that that's true. So at this point most likely for Katie it's a lateral pterygoid but I want to actually be able to prove that to myself.