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This is a 42-year-old man with a

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rather violent posterior dislocation.

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It's no secret,

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the patient has innumerable areas of

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marrow edema, and in fact, 14 percent of all overt

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posterior dislocators will have some type of micro

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or macro trabecular fracture, with the humerus being

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number one, followed by, followed by the scapula.

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And this patient has a scapular

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fracture as well as a humeral fracture.

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The humeral fractures are mostly medullary.

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You can see them on the T1 weighted image.

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And the defect, anteriorly, is depressed.

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So this portion of it is a cortical

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depression, a rather violent and deep one.

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This part of it is intramedullary.

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So it's in the anteromedial aspect of the humerus.

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Where you would expect to see a

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reverse Hill-Sachs abnormality.

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Now, let's look at, I'm going to move the image

0:58

over and make it just a little bit smaller for you.

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So you can see that the glenoid is missing a piece.

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Let's follow our glenoid.

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It's very edematous because it's fractured.

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But that's a piece of a glenoid cortex.

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And let's go back, posteroinferiorly,

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and look at the amount of bone loss you have here.

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That's what's left of the glenoid cortex.

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We have mentioned in other vignettes that

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it's the posterocaudal aspect of the glenoid

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that is more prone to violent attachments

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and injuries than the mid to upper portion.

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And that's similar to the anterior aspect of the shoulder.

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Let's scroll the water-weighted image and I

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think you can appreciate the same findings.

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Focusing on the amount of bony loss in

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the posterior inferior glenoid, you can

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see the capsule has been pulled off it.

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There's a big cavernous area of separation.

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You could drive a truck through there.

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And there's also other pathologies, including

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a superior labral tear, which is chronic.

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Not unexpected in somebody who is athletic

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and very muscular, even though he's 42,

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he's middle-aged, but still quite muscular.

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Now let's focus on the axial projection for a moment.

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Rotator cuff tears occur in

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violent dislocations posteriorly.

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And those tears can result in detachment of

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the posterior capsule and the rotator cuff.

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In this case, the capsules come off

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right there, but the rotator cuff is on.

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But, in severe ones, the entire posterior rotator

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cuff mechanism, the infraspinatus and teres can come

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off, or just the infraspinatus, or just the teres.

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If the rotator cuff is affected anteriorly, namely

2:52

the subscapularis, it's usually an incredibly violent

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dislocation, and usually the humeral head stays out.

3:00

So when you see the patient, if the subscap is off, usually

3:03

the humeral head is not centered in the cup anymore.

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Just a word about centering, before we get

3:08

into some of the posterior labral findings.

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I've told you in other vignettes that I generally put a

3:13

little dot in the middle of my humerus, and I put a dot in

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the middle of my glenoid, and I like to see them congruent.

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But I'll allow up to about 5.

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8 centimeters, uh, sorry, 5.

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8 millimeters of displacement

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posteriorly, before I get too excited.

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In fact, the mean as reported by a,

3:33

uh, renowned author Tongue is 6 to 6.

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2 mm.

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So, you know, if you use a number of 6 mm,

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that's, that's absolutely, absolutely fine.

3:44

And then we talked about the concept

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of retroversion and antiversion.

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And the mean retroversion angle

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for most patients is about, uh, 4.

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5 degrees.

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So let me draw that angle for you one more time.

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So, we're going to take a line along the scapular spine.

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Take another one perpendicular to it.

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And then we're going to go cortex to cortex.

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Sometimes not easy to do.

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And then these two will meet up somewhere back here.

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And you'll have an angle.

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So that would be your retroversion angle.

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The mean retroversion angle is about 4

4:19

5 degrees.

4:20

I allow it up to 6 degrees.

4:23

When you see it around 10 degrees, those are individuals

4:26

that are prone to posterior instability syndrome.

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So those are some good numbers to have in your back pocket.

4:33

That being said, we have a catastrophic

4:35

major posterior dislocation.

4:38

We have lost a big chunk of the posterior glenoid.

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We've detached not only the bone,

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but also the labrum with it.

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We have injured and separated the capsule from the labrum.

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We have separated completely the

4:56

periosteum from the underlying bone.

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Here is more periosteum and capsules separated.

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So this is a very convoluted lesion.

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We've got a capsular tear over here, laterally.

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We've got a capsulolabral tear.

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We've got a labroglenoid separation.

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And we've got a periosteal separation.

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And you might refer to this as

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a quadruple lesion, if you will.

5:22

And on top of that, he's got a chronic slap lesion.

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And on top of that, he's got a complex,

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depressed, anteromedial, reverse, hill sax lesion.

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And I'll leave you with all the massive

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swelling and the intramedullary and chondral

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spongy bone edema, which we've discussed.

5:44

Dramatic posterior dislocation.

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Posterior complex injuries.