0:00

Okay.

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Let's talk a little bit about the rotator cuff.

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And as you know, this is our

0:09

deep foray into the jungle of the shoulder.

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It's like shark week.

0:13

It's shoulder week.

0:16

We've got the humeral head and neck,

0:18

and then we've got, pretend we're anterior,

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we've got the supraspinatus muscle,

0:26

and then that transitions into the myotendinous

0:29

junction, which is of variable thickness.

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And a variable length.

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And that junction can be divided up into a thicker area

0:40

where the tendon fibrils actually have a greater diameter.

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And that's known as the, the cable portion of the cuff.

0:48

And then we have kind of the arc shape.

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And I really should make it, really should make it thinner.

0:54

Because they are thinner.

0:55

You have the arc shaped crescent portion of the cuff.

1:00

And then we finally tamp down the

1:02

cuff as the footprint, or footplate.

1:07

That's the attachment portion that goes on the

1:10

marginal edge of the humerus, greater tuberosity.

1:13

So we've got muscle, myotendinous junction, cable

1:18

portion, crescent portion of the myotendinous

1:21

junction, footprint, but still tendon.

1:25

So there's a pretty long, uh, tendinous area.

1:29

And some individuals like to describe injuries to the

1:33

cuff as being that which has occurred either in the

1:37

cable or in the crescent or as a tear that is crescent

1:42

dominant configuration or cable dominant configuration.

1:46

And that's going to be a story for a

1:48

little bit later because that's a little

1:49

more advanced and a little more complex.

1:52

But when somebody has a real long cable,

1:56

Thicker portion of the myotendinous unit.

1:58

They're gonna tear and retract a little bit differently

2:01

than if they have a longer crescent portion of the cuff.

2:07

Then there are other descriptors that involve

2:11

the medial lateral orientation of the cuff.

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And a lot of these basic tenets for the

2:16

supraspinatus will apply for the infraspinatus.

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And the teres, although the teres almost never tears.

2:24

And it'll apply for the subscapularis,

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although the shape of the subscapularis belies

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a slightly different set of descriptors.

2:34

So, we'll get in, we'll get into

2:35

the subscapularis on its own.

2:37

Let's pretend we're talking supra

2:40

and infra together right now.

2:44

So then we're going to look at in the coronal plane,

2:46

whether we have a footprint tear, a crescent tear, a

2:49

cable tear, or we may even ignore these if we can't

2:53

distinguish them, and just say the tear is medial to

2:55

the footplate or footprint, or it's at the myotendinous

3:00

junction, which would be here, or it's in the muscle, or

3:03

there could be even a cyst that's located in the muscle

3:06

called the sentinel cyst from a very small tear, which

3:09

will be a story we'll also tell a little bit later.

3:13

We'll then look at where the cuff has retracted to.

3:17

If it ruptures and breaks into two parts,

3:20

then we may describe this medial lateral

3:24

rupture as having a retraction dimension of X.

3:28

Or we might say that the retraction

3:32

lies just underneath the AC joint.

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As long as we communicate, that's fine.

3:39

Is it preferable to say it lies under the AC joint with

3:42

a retraction dimension of four and a half centimeters?

3:45

Yeah, it is.

3:45

That's simple, direct, better communication.

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But one or the other will usually suffice if

3:52

you haven't had your second cup of coffee yet.

3:57

Another way to describe, and an important

3:59

way to describe, uh, cuff injuries is by

4:03

their location relative to the humerus.

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Now we've already said that, uh, This portion of

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the cuff that sits right on top of the humerus and

4:14

attaches to it is called the footplate or footprint.

4:17

If we look from the top down, you will see that

4:21

the supraspinatus comes over from medial to

4:24

lateral and goes on the humeral head and curves.41 00:02:13,825 --> 00:02:16,084 And a lot of these basic tenets for the

2:16

supraspinatus will apply for the infraspinatus.

2:20

And the teres, although the teres almost never tears.

2:24

And it'll apply for the subscapularis,

2:27

although the shape of the subscapularis belies

2:31

a slightly different set of descriptors.

2:34

So, we'll get in, we'll get into

2:35

the subscapularis on its own.

2:37

Let's pretend we're talking supra

2:40

and infra together right now.

2:44

So then we're going to look at in the coronal plane,

2:46

whether we have a footprint tear, a crescent tear, a

2:49

cable tear, or we may even ignore these if we can't

2:53

distinguish them, and just say the tear is medial to

2:55

the footplate or footprint, or it's at the myotendinous

3:00

junction, which would be here, or it's in the muscle, or

3:03

there could be even a cyst that's located in the muscle

3:06

called the sentinel cyst from a very small tear, which

3:09

will be a story we'll also tell a little bit later.

3:13

We'll then look at where the cuff has retracted to.

3:17

If it ruptures and breaks into two parts,

3:20

then we may describe this medial lateral

3:24

rupture as having a retraction dimension of X.

3:28

Or we might say that the retraction

3:32

lies just underneath the AC joint.

3:36

As long as we communicate, that's fine.

3:39

Is it preferable to say it lies under the AC joint with

3:42

a retraction dimension of four and a half centimeters?

3:45

Yeah, it is.

3:45

That's simple, direct, better communication.

3:49

But one or the other will usually suffice if

3:52

you haven't had your second cup of coffee yet.

3:57

Another way to describe, and an important

3:59

way to describe, uh, cuff injuries is by

4:03

their location relative to the humerus.

4:07

Now we've already said that, uh, This portion of

4:10

the cuff that sits right on top of the humerus and

4:14

attaches to it is called the footplate or footprint.

4:17

If we look from the top down, you will see that

4:21

the supraspinatus comes over from medial to

4:24

lateral and goes on the humeral head and curves.

4:28

And all the fibers will curve.

4:30

And if you internally rotate the

4:32

shoulder, they will curve even more.

4:34

And the more they curve, the harder they are to evaluate.

4:37

That's why we don't want to internally rotate the shoulder.

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And the more they curve, the more

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magic angle effect you're going to get.

4:45

Making diagnosis a little bit tougher.

4:47

So we like to have the hand either

4:48

neutral or slightly externally rotated.

4:52

The infraspinatus, which we're

4:55

going to attack in a few moments.

4:58

And we're going to change color

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for the infraspinatus for a moment.

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Hope we don't run out of colors.

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Will come right underneath the supraspinatus and they

5:06

interdigitate with each other So the infraspinatus is

5:09

creeping right underneath the supraspinatus It actually

5:12

goes pretty far forward, but in the sagittal you'll

5:15

see a space between the two right here And I'll draw

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the sagittal for you known as the posterior rotator

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interval Which means there's an anterior rotator interval

5:27

and there's also a far posterior rotator interval So

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some people refer to this as the central interval.

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But as you get further out, you're going to have

5:36

a very difficult time distinguishing the fibers

5:39

of the infra and supra because they interdigitate.

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Another interesting aspect of rotator cuff anatomy

5:47

is as the supraspinatus comes forward, it may

5:51

send some fibers over to the lesser tuberosity.

5:54

Let's pretend we have a humerus underneath there.

5:56

I'll make my humerus blue again just to be consistent.

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And there is my lesser tuberosity.

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And here are my lesser, here are my fibers going over.

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Just a few go over to the lesser

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tuberosity from the supraspinatus.

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And that's only in the last ten years been recognized.

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And only in the last ten or twenty years

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has the degree of interdigitation between

6:20

these two structures been recognized.

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frequently than the infraspinatus.

6:28

Often.

6:29

as a result of contact abnormalities when

6:32

the arm is over the head, especially when

6:35

it's in front of the mid-coronal plane.

6:38

So when it's in front of your mid-body,

6:41

or the mid-scapular line, that's where the

6:44

supraspinatus gets the most forces applied to it.

6:47

Whereas the infraspinatus has more forces

6:50

applied to it when you're in the cocking motion.

6:52

When the arm and elbow are behind that mid-coronal

6:56

line along the scapular line, or mid-scapular line.

7:01

So now let's go back to our discussion.

7:04

We got a little bit sidetracked regarding the humeral head.

7:06

We said the footplate or footprint

7:08

is a rather complex structure.

7:12

And when you have a tear, say, in this location, it is

7:15

not, let me repeat, it is not an articular sided tear.

7:21

It is an articular-sided tear.

7:23

Stop doing that.

7:25

There's no articular surface there.

7:27

There's no synovium there.

7:29

There's no cartilage there.

7:31

It's on the humeral head surface

7:33

of the footplate or footprint.

7:34

And it is concealed.

7:37

It's invisible.

7:39

They can't get in there from this direction and see it.

7:42

They can't get in there from

7:43

the deltoid approach and see it.

7:45

It's hidden inside these fibers

7:47

and is usually a nonsurgical tear.

7:50

If it gets inside the humeral head and pits the

7:54

humeral head, it's got a rim rent component.

7:58

These are often referred to as concealed

8:00

interstitial delamination tears of the foot

8:03

plate or footprint with rim rent penetration.

8:08

Then if we get a little further over,

8:12

we're in the region of the bare area.

8:17

you're always going to see a little signal there because

8:19

there's no cartilage. That's why it's called the bare

8:22

area and the cartilage starts right about here. Now we

8:28

have hyaline cartilage, so if you have a tear here,

8:30

you'd say it's a bare area tear. Right next to

8:33

the footplate or footprint, if you have a tear

8:35

underneath here, you would say that it's an

8:38

articular-sided tear, so let's stop right there.

8:45

Let's stop right there, and pause for a minute, and then

8:50

we're going to come back to this same diagram, and we're

8:52

going to drill into the next layer of intelligentsia.

8:57

Be back in a minute.