0:01

So let's talk about some of the basic concepts

0:03

and the controversies

0:05

or disagreements related to those concepts.

0:08

The first one relates to excessive external rotation

0:13

that occurs at the glenohumeral joint.

0:15

It is an extremely important factor

0:19

and it influences the velocity of the baseball pitcher.

0:23

So, as you know, nowadays, the professional baseball pitcher

0:27

commonly throws a, a greater than 90 miles an hour,

0:31

and some, in fact go over a hundred miles an hour.

0:34

So velocity is particularly important.

0:37

So it's the concept of ex,

0:40

this excessive external rotation.

0:43

And the controversy is what causes the ability

0:47

of the thrower to have this external rotation

0:50

of the shoulder far more than, for example, I

0:53

or you, uh, could, uh, uh, get to.

0:57

And there are two theories.

0:58

One is called the adaptive capsular Laxity theory,

1:02

which suggests that the primary abnormality relates

1:05

to injury to the anterior capsule, leading to laxity

1:10

that will lead to anterior instability,

1:12

but provide ex, uh, exaggerated external rotation.

1:17

And then the second theory,

1:18

and the one that I'm gonna emphasize in the next slides is

1:21

de designated the posterior capsular contracture theory.

1:26

And this suggests that there are a number of abnormalities

1:28

that occur involving the postal inferior,

1:32

and to a lesser extent, the postal superior region

1:36

of the capsule leading to its contraction.

1:39

Okay? And owing to that one will develop

1:44

excessive external rotation,

1:46

but the price that is paid is designated GERD

1:49

or glenohumeral internal rotation deficit.

1:53

Now, the GERD topic is the subject of many, many, uh,

1:58

articles in the literature.

2:00

I'm gonna simplify it

2:01

and not talk a great deal about it tonight,

2:04

but you should learn a little bit about gerd.

2:07

It's very, very important.

2:08

And to illustrate that, that I would mention

2:11

that the normal arc of motion in non throw throwers is about

2:17

180 degrees with equal movement in external

2:21

and internal rotation.

2:22

So in this particular diagram taken from the literature,

2:26

you can see in non throwers, they have equal amount

2:29

of internal and external rotation.

2:33

Now, for the throwers, it's different.

2:35

They have to, in order to be good, develop excessive

2:38

external rotation, and they do so.

2:41

And you can see that with the black curve,

2:43

this is their excessive external rotation,

2:46

but the price they pay is a limitation in internal rotation,

2:51

less internal rotation than you see in non throwers.

2:55

And that particular finding of GERD can be career ending.

3:00

So what I'm saying is that the pictures over time

3:04

develop this ability that they need

3:07

to externally rotate their emeral joint,

3:10

but eventually the GERD problem will maybe end their career.

3:15

And if you wanna see, for example, here are two pictures

3:18

of a a child, and then, uh, here is a young adult

3:22

and you can see the difference in external rotation

3:25

that the baseball pitcher gets over a period of time.

3:29

There's a higher risk of injuries to the shoulder with gerd,

3:32

and there may in fact be developed a humeral retroversion.

3:38

So let's look at what happens during the deceleration

3:42

and follow through phases.

3:44

What will occur, and I'll show you this in a few slides, is

3:48

that that capsule will in fact rotate in a postal

3:52

central to direction.

3:55

And this will be the area of the capsule

3:57

that will resist those spinal forces that occurred

4:01

during deceleration and follow through.

4:04

So over a period of time related to that,

4:07

the posterior capsule will thicken and contract.

4:11

I'm gonna show the diagram indicating that by this kind

4:14

of strange green lines that you see here,

4:18

but that's to indicate the contraction

4:21

and shortening of the capsule

4:23

and thickening of the capsule

4:25

that occurs over a period of time.

4:28

Now, you can see that when you look at these shoulders in

4:32

with MR imaging

4:33

and you don't need arthrography to see,

4:35

to see the abnormalities,

4:37

although we have it in this particular example,

4:40

you're gonna see a lot of fibrosis in

4:43

and around the posterior labrum,

4:45

often the postero inferior labrum,

4:47

but sometimes the posterior superior labrum.

4:50

And in this case, the yellow arrow is pointing to that.

4:53

Here's another one. Even more dramatic.

4:56

The image quality is not terrific,

4:58

but you can see here during the autogram, the, uh,

5:02

intra labral and per labral fibrosis that has occurred

5:06

because of the stress

5:08

that's placed on the postal inferior act aspect

5:12

of the joint capsule.

5:14

Now, there's a good thing for the thrower that that occurs

5:17

that because of that particular contracture,

5:21

the contact point between the humeral head

5:23

and the glenoid will move from this position

5:27

to a more postal superior position.

5:30

You kind of get that idea here in a sagittal Mr.

5:34

Orthographic image.

5:35

Here's the humeral head, here's the glenoid.

5:38

So the humeral head has shifted its point of contact

5:41

to this region, and it's this shift

5:44

that will allow the greater tuberosity

5:47

to clear the corco acromial arch.

5:50

Now I get this far and that's what I can't go any further.

5:54

But with this ability of shifting

5:56

The contact point to a more posterior superior location,

6:02

that baseball pitcher can further externally rotate.

6:06

And with that comes an ability

6:08

to throw the baseball, uh, faster.

6:12

Now, what will occur

6:14

because of, uh, that shift is a pseudo laxity

6:19

of the anterior capsule.

6:21

And that's why a lot of people think this is a

6:23

primary abnormality.

6:25

But what it relates to is the shift

6:27

of the contact point from a more central

6:30

and lower point up to this particular area.

6:34

In the normal situation, in abduction

6:37

and external rotation, the anterior capsule is very tight,

6:41

but when you shift the contact point, it will become lax.

6:46

Some people call this pseudo laxity.