Well, thank you very much, John. Thank you all for coming. And I don't have much about the batter's shoulder, I've got some about the thrower's shoulder, so we'll talk a little bit about this. You want me to originally talk a little bit about the scapula, we'll do that, but we're really going to cover the pathomechanics of the problem. So, we can use this term disabled throwing shoulder. It was a term that Steve Burkhart and Craig Morgan and I first came up with back in 2003, and we've really honed our knowledge since that time, and the latest distillation of that is in this past week's issue of arthroscopy, the third update. But we want to talk about the pathomechanics and also about the pathoanatomy. They're two separate things, and you have to understand both if you're trying to deal with this disabled throwing shoulder. And I will make the case that pathoanatomy is more posterior labral injury rather than the superior labral injury. There's a lot of good data to suggest that. So, this is rather complicated here, but I want to show that internal impingement is the pathomechanics that drives the largest majority of the problems in the throwing shoulder when they come to see you in the office. And it's rather complicated. It's scapular protraction and posterior humeral head translation. They come together, unfortunately, right there. So, you see you've got the components of scapular protraction, which include the anterior tilt, internal rotation, decreased upward rotation. So, the scapula is coming forward and around, and the glenoid is coming forward and around, and the humeral head is going back. And there's a lot of reasons for the humeral head going back. Biceps tightness, decreased external rotation, increased internal rotation tightness. There's a lot of things. And then you've got the kinetic chain. So, if you know this slide, you've got this shoulder taken care of, okay? But basically, this is what's going on. And all these factors come together right at the posterior labrum. Not the superior labrum, and not the anterior labrum. So, let's look at the kinetic chain just a second. It's a mechanism for force generation. You have to have your core stability, your base. You transfer linear to angular momentum. There's an optimum stride length. And you'd be amazed that if you don't get the right stride length, then the rest of the chain does not work. And this optimal stride length, about 75 to 85 percent of your height. And it really has a lot to do with how efficiently you transfer the force, generate the forces, transfer the forces to the hand. There's a stride leg to plant leg energy transfer. It's a platform for your optimum kinematics of the rest of the kinetic chain. It's interesting that the stride leg, the back leg, you get hip and knee extension, and it acts as a catapult. You actually catapult up and over. It's what you drive leg with. You know, that's what you do. And your linear momentum allows the center of mass to move toward home plate. That's how you get your momentum. Bad things happen. Fatigue, you get decreased muscle activations, ground reaction force. You get decreased stride length. You get that, then you uncouple the lower body from the upper body. So, that instead of having the normal sequencing and rotations, then it's a shortened time. To be honest with you, your arm doesn't cock as far back. You're still in protractions. You're trying to go backwards right there. So, there's a lot of things happening in lower extremity that has a huge effect on how the arm moves and how the rest of the mechanics work. And you can look at this. You can look at them. Everybody has a video. You can watch. You can measure their stride length, for example. You can see. Decreased stride length gives decreased scapular shoulder external rotation into cocking. Decreased plant leg breaking force so that you cannot break well here so that you tend to lean over. You're opening up and you have an increased distraction force on the posterior shoulder in deceleration. Now, the shoulder is a force regulator. Efficient transfer from the lower extremity to the upper extremity to the ball. The joint is a funnel for the forces. It requires effective co-contraction not only of the rotator cuff but also of the force couples around the scapula. Only 18 percent of the deceleration force is taken by the rotator cuff, 40 percent by the scapula, 40 percent by the kinetic chain, by the core. So, if you don't have efficient co-contractions there, then you are increasing the distraction forces at the shoulder. This is some data from a motion capture system that we're working on now that shows the coupled motions. These are the three motions of the scapula, anterior posterior tilt, internal rotation, upward rotation. You find that the sequence is that internal rotation, maximum external rotation of the scapula precedes maximum posterior tilt and ball and upward rotation occurs right at or just after ball release. So, there's a sequence. If you don't get the scapula back, then you're never going to be jumbling things up. So, what affects internal impingement around the scapula? We know that decreased upward rotation increases the area of impingement. This internal impingement increased internal rotation. So, see you're talking about this protraction and lack of upward rotation increases the area and pressure of this internal impingement on the posterior cuff. This is a modeling here that shows that if you look at that right there, you find that the five degrees of anterior tilt in addition to internal rotation increases the forces at the rotator cuff and labrum by about five-fold. So, it's a huge loss if you don't get your scapula into the posteriorly tilted position. This is a motion capture. You can see in a patient with internal impingement, the right is the injured side. You see at 90 degrees of abduction up there toward the right hand of all those people. See how it goes into anterior tilt and goes into internal rotation up here at 90 degrees. So, this is the mechanics that's going on in patients who have these internal impingement problems. We've been looking at, we know about internal rotation and that's bad. Turns out external rotation is also bad, but you've got to make sure that you measure it the right way so that the decreased external rotation in cocking creates compensations. If you can't get back here, the only way you're going to get back here is do one of these, which puts internal, once again, there's your horizontal adduction, there's your internal impingement, or you throw from here, which means you cannot develop the right velocity. So, if you can't get external rotation, well, turns out you don't throw the ball this way, throw the ball this way. So, you need to know what the pronated forearm, why is that important? Because that tightens your biceps. And we did a study which showed that if you measured in the power position with pronation, we did the studies in sports health now, we looked at high school, college as well, professional athletes, that 80% of the players have a difference between the measurement of external rotation this way and a measurement this way, 10 degrees less with a pronated position, which means that if you can't get back here, once again, you got to do something to compensate for. So, you need to measure external rotation in the correct way. So, what you do is you measure the classical stabilized scapulae internal rotation, external rotation in neutral, but then you pronate the forearm and measure in pronation. The other thing we look at is, is the slap the pathoanatomy? So, we did this study here just recently where we looked at everybody we operated on arthroscopically for a labral injury, and we and we categorized their location, isolated anterior, isolated superior, posterior, and then combined throughout those areas. And we looked at all and we looked at all their videos and everything. So, this is the incidence of the location. You see the superior, the slap, the 11 o'clock to one o'clock, 7%. The posteriors, isolated posteriors, not involving superior at all, 26%. And then the superior posteriors or the slap eights, 22%. Some type of superior involvement, only less than half of all the labral injuries. Some type of posterior involvement, 86%. That's all of us, anterior posteriors, posterior superiors, isolated posteriors, the three, the 270s around. So, the point is that there's a whole lot of, if you're only looking for superior labral injuries, you're missing a whole bunch of things. Now, you say, well, that's a one-off, Kibler. You don't know what you're talking about. Well, it turns out that Javier Duralde was doing the exact same experiment or study exact same time. We didn't know about them. They didn't know about us. Theirs is published. We published both these within a month of each other in the last, in March of this year. They came up with the exact same numbers. So, this is probably the way to look at this, that indeed, a symptomatic thrower with a labral injury is not a superior labral injury as by itself. It's something, but it's in addition to. And so, you need to look at these other places very, very carefully. So, our current concept now is there's probably two types of clinically significant labral injuries. The first is this slap eight or this superior and posterior that has a superior component around the bicep, but it extends inferiorly all the way around to the seven o'clock and maybe down into the IGHL. This is probably a, it's called a weed pulling that Dr. Andrews talks about, but it goes all the way around the corner and it's sometimes, you can see it's an in-substance injury as well as a detachment away from the bone. But then there's a whole other group that are strictly due to the isolated posterior. They don't have anything to do with the slap. These are all translation injuries. These are all this impingement because of the protracted scapula. And you see that they're just beaten up. And you see, this is a thrower. This is not a football player. And you see, it's not only, it's an in-substance injury. You can see how this has been sheared. It's interesting that the middle part of these fibers are linear, almost like hoop stresses around the meniscus. And when they get injured, then you lose that concavity compression. You use that bumper. You lose that edge stability that is necessary to keep the glenohumeral joint in a dynamic stability position. So, clinical implications. You've got to look at the kinetic chain. Seriously, you've got to look at things that are important. Strength, balance, stride length, look at the scapular position and motion. Hopefully, we've understood a little bit about that a little bit more. Look at your glenohumeral rotation because it plays a huge role in the position and kinematics of the glenohumeral joint in this dynamic thing. And then, if you do end up with surgery, then please look at the entire labrum. The number of cases of failed slaps that missed the posterior component. I've got 47, a case of 47 of failed slaps, and 31 of them were missed posterior labral injuries. They just missed them. They're there. And they were missed. Continue to have symptoms. Continue to have posterior symptoms. So, just look for all that as well. Thank you very much.

disabled throwing shoulder

scapular protraction

biceps tightness

kinetic chain

labral injuries