0:01

Let's take an overview of the three

0:02

projections we're going to use for shoulder MRI.

0:05

And we're gonna, we're going to take a general overview, not

0:09

just instability, but with a focus on instability.

0:13

Now remember your coronal projection, your coronal

0:16

projection should parallel the scapular spine.

0:18

So it's not going to be a straight coronal, it's going to

0:20

be an angled coronal along the long axis of the scapula.

0:24

Another little, uh, pearl that I, that I

0:27

didn't discuss is, you know, if the humerus

0:30

is angled like this in the coronal projection.

0:32

Then I want your sagittal projection

0:34

to be along the long axis of the shaft.

0:37

I don't want it to be straight up and down, because

0:39

that's going to help you with rotator cuff tears.

0:42

And the axial projection, I don't mind if they're completely

0:45

orthogonal, whether it's a macro or micro instability case.

0:50

So let's talk coronal for a minute.

0:53

Coronal projection, you're going to look at the AC

0:55

joint, you're going to look at the rotator cuff.

0:56

Remember people that dislocate with Hill-Sachs lesions,

1:00

they get cuff contusions, they get cuff bleeds.

1:03

Elderly patients have a much higher

1:05

incidence of rotator cuff tears.

1:07

The more fatty infiltration they have of their muscles,

1:10

the more likely they are to tear with a dislocation.

1:14

Biceps labral anchors typically are well-seen

1:17

coronally, but they don't tear unless you

1:19

have a downward inferior violent dislocation.

1:23

The coronal projection is, is your most favored

1:27

nation view for the three bands of the inferior

1:30

glenohumeral ligament, anterior axillary and posterior.

1:33

Probably not so much for the middle glenohumeral ligament.

1:36

And it is a great view to look at the subacromial

1:39

arch in space in impingement syndrome, and to look

1:42

underneath the AC joint to see what's happening there.

1:45

It's not as good a view to see the subcoracoid arch.

1:49

For micro-instability, the coronal view

1:51

will help you segregate out the different

1:53

types of SLAP lesions, 1 through 12.

1:57

The AP rule.

1:59

The AP rule says as you go from front to back, any

2:04

fissures that you have in the superior labrum, let's

2:06

draw a labrum, let's pretend we have a fissure right

2:09

here, let's make our fissure a different color, any

2:12

fissure you have right here will diminish in conspicuity,

2:17

it'll go away as you go posterior, so the attachments

2:21

in the back on the superior labrum are going to be

2:24

tight, and then we've already discussed in another

2:27

vignette, when you're down low, you're Alright.

2:30

Your axillary labrum should point about 60 degrees

2:35

to the axis of the shoulder, but your inferior

2:38

glenohumeral ligament tends to come off a little

2:40

more medial relative to the inferior labrum and it

2:44

usually comes off right at the junction between the

2:47

bony glenoid, pretend this is the glenoid right here,

2:50

between the bony glenoid and the inferior labrum.

2:55

Also use the coronal projection to see if the humeral

2:57

head is floating up, it's decentered superiorly.

3:02

Usually a sign of failure of the

3:05

depressor mechanism of the shoulder.

3:07

Frequently these patients have atrophy of the

3:09

trapezius, supraspinatus, and sometimes they

3:12

even have some lateral deltoid atrophy too.

3:16

This is also a great projection to look at the

3:18

brachial plexus and the quadrilateral space.

3:21

The sagittal projection.

3:23

As it relates to instability, Uh, this is

3:27

where you want to look for glenoid bone loss.

3:29

And we're going to show you later on in a separate vignette

3:32

how to make on-track and off-track measurements to look at

3:35

the presence of engagement or, or lack thereof in patients

3:40

that have repetitive instability or macro-instability.

3:45

This is an excellent projection to look at the

3:47

biceps takeoff and biceps pulley mechanism.

3:49

It is my favorite projection to look at the character of

3:52

the glenoid fossa along with the axial to look at its depth.

3:56

To look at its shape, its roundness, etc.

3:59

Um, I'll also look at the acromion and the rotator

4:01

cuff in this projection, from front to back.

4:07

looking at the Hill-Sachs best in the coronal.

4:09

And especially measuring its percent

4:11

of involvement in the axial projection.

4:14

Remember, 40 percent or greater for a Hill-Sachs, danger.

4:17

Remember, if you lose 25 percent or more

4:22

of the anterior radius of your glenoid,

4:25

which was measured in a prior vignette.

4:27

That is early danger, if you lose 50-60 percent of that

4:32

anterior radius, that is, that is significant danger.

4:35

So go back to that vignette and look at it again.

4:38

The sagittal projection, great way to look

4:40

for scapular, body, and spine fractures.

4:43

And it's also an excellent way to look for the Bennett

4:47

lesion in patients with repetitive instability.

4:49

What's the Bennett lesion?

4:50

A periosteal bleed along the posterior rim of the

4:54

glenoid cup, so here's our pear-shaped glenoid cup.

4:57

It's usually posteroinferiorly,

4:59

so it's going to be back in here.

5:01

I've drawn it in green.

5:02

And it usually calcifies or ossifies.

5:05

A sign of either macro instability or, more commonly,

5:09

repeated micro instability with periosteal hemorrhage.

5:12

The axial projection.

5:14

What's the top-down rule?

5:15

The top-down rule says that And I'll

5:18

say it again, and again, and again.

5:21

When you go from the top down, the labrum should get

5:24

bigger and blacker than it is up high, and it should

5:29

get bigger and blacker than the posterior labrum.

5:32

Any fissures, or sulcuses, or sulci, in the

5:36

upper portion of the shoulder should go away

5:39

by the time you hit the equator of the humerus.

5:42

And then as you continue on down, there should

5:44

be none other than normal hyaline interposition

5:48

between the fibrocartilage and the glenoid.

5:52

This is also a good projection to look at the

5:55

anterosuperior rotator interval, which contains

5:59

the superior glenohumeral ligament and the

6:02

coracohumeral ligament and some fibroelastic tissue.

6:05

You can look at all the components of

6:07

the rotator cuff in the axial projection.

6:09

I suggest you do so.

6:11

The axial projection is the projection

6:14

for determining the nature of chronic peelback

6:17

lesions that we see so commonly in athletic

6:20

men and women who like to lift weights.

6:23

You'll see Perthes lesions, or reverse Perthes

6:25

lesions, also known as Kim's lesions, Pulp's lesions,

6:29

Capsular detachments, reverse dislocations, and so on.

6:32

And we're gonna get into all of

6:34

these and how we characterize them.

6:36

The axial projection shows you

6:38

all the glenohumeral ligaments.

6:39

It shows you the biceps labral anchor.

6:41

It shows you the coracoid arch.

6:43

And importantly, in instability, it shows you whether

6:46

the humeral head is anterior or posteriorly de-centered.

6:52

In green, I'm going to draw you a labrum.

6:55

And if the front of the glenoid is protruding out

6:58

a little bit, it may force the humeral head back.

7:02

So the humeral head may de-center posteriorly.

7:04

That is posterior de-centering from what

7:07

we call retroversion of the glenoid cup.

7:10

That'll be a special story.

7:12

Or you could have the opposite.

7:14

You could have glenoid cup and

7:16

push the humeral head forward.

7:18

Now you have anterior de-centering of the

7:20

humeral head with antiversion of the glenoid cup.

7:24

So that concludes a very quick, concise, intense

7:28

review of the three projections of the shoulder.

7:31

And it's time to move on to some pathology if

7:34

you've looked at all the technique vignettes.