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Let's talk a little bit about the glenoid cup.

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It is just simply too shallow for the size of this giant

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humeral head, and that's why the shoulder dislocates.

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It's also got some unique features.

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We're gonna look at its concavity and make sure it's

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not flat, and if it's flat, we're gonna comment on that.

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We're also gonna make sure it's not too deep, because

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if it's too deep, then that's gonna restrict motion.

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If it's too flat, then there's gonna be too much motion.

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So we don't want either of those, it's gotta be just right.

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It's also got some quirky variations,

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for instance, look at this right here.

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I'm gonna put my little pen marks on it, right there.

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What is that?

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An OCD?

0:41

No.

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This is the normal notch of Osaki that

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exists in the center of the glenoid cup.

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And frequently, if you scroll this area, the

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highland cartilage, which is this gray area

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right here, gets a little bit thinner, and

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this is known as the bare area of the glenoid.

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Now let's go over to the sagittal projection.

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And we see that the glenoid cup is a pair, right?

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Here's our pair.

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I'm going to trace it again.

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Yeah, it kind of looks like a pair

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if you've got some imagination.

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And if you lose the bottom of the pair, let's

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say you took off this piece right here, you

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might have what's called an inverted pair.

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You know, it's a little fatter at the top,

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and it's a little more narrow at the bottom.

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Or, you took a slice out of the pear.

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And that would be bad.

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How bad?

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Well, if you get substantially more than 50 percent of

1:36

this height involved in glenoid bone loss, very bad.

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And we're going to discuss that in detail.

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So the glenoid is concave.

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It's a, it's a, it's a compression and a depression.

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In other words, through a range of motion, the

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humerus is compressed against this concavity.

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It's particularly important.

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In the mid range of glenohumeral movement.

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Because in the mid range of glenohumeral

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movement, this tissue here is lax.

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So when you hear about somebody that lies in

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bed with his arm over the head, Not in extremes

2:11

of internal rotation or external rotation

2:13

and the shoulder just pops out, that's why.

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Because they're in the mid range

2:18

position where these structures are not.

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So that's just a brief discussion of the glenoid cup.

2:28

I didn't give you any measurements, but I want to leave

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you with one measurement that we're going to talk about in

2:33

greater detail when we get into actual cases of instability.

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This patient's normal.

2:38

And that is anteversion Now that sounds kind

2:42

of fancy, but don't get, don't get scared.

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So let's look at the scapula, and if we draw a line along

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the scapular spine, just kind of off the screen, but

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pretend that we see it, and then we take a line that's

2:57

drawn from one cortex to the other cortex, and we make this

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intersection right here, that should be within three to six

3:06

degrees of a line that's absolutely balls on perpendicular.

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So, actually, let me make my second line orange.

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So, I'm going to take it all off again.

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I'm going to redraw.

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I'll make my scapular line blue.

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Pretend we're going along the scapular spine.

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I'll make my perpendicular line, oh, let's pick orange.

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From cortex to, sorry, perpendicular

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to my blue line right there.

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Absolutely perpendicular.

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And I'll make my cortex to cortex line blue.

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Let's make that brown, so my cortex to cortex line, brown.

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And so I have this angle right here, and that

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angle should be about three to six degrees.

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So if the anterior bony architecture and labrum

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stick out all the way, then now a line from cortex

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to cortex is going to look something like this.

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And we're going to say that the shoulder is

4:15

retroverted, or the glenoid is retroverted.

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On the other hand, if the back of the labrum sticks out

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And let's start over again in our, with our drawing tool.

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If the back of the labrum sticks out, we'll make it yellow.

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Let's say it's stuck out all the

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way to here, along with bone.

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So let's say the bone is over here,

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and now our line is like this.

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Relative to our perpendicular line,

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which would be, say, like that.

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Then we would say that the

4:45

shoulder demonstrates antiversion.

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And I'm going to give you some detailed analyses

4:51

of antiversion and retroversion angle measurements.

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This is just a simple introduction

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when we show you examples of such.

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So that concludes our discussion of the glenoid.