0:00

Now let me briefly talk about micro instability.

0:04

I'll talk a bit more about it in the second lecture today.

0:07

But this is typically seen between the hours of 12

0:12

and three on the glenoid face

0:14

because in that area you have a coracoid process

0:17

that is preventing macro instability.

0:20

It may occur with an acute injury,

0:22

but in my experience it's often associated

0:25

with chronic stress seen in athletes.

0:29

If those athletes typically complain of pain,

0:32

maybe a little bit of what they consider slipping

0:34

of the joint, and there are a number of abnormalities

0:38

that can be associated with it.

0:40

We've already talked about slap lesions, superior labral,

0:44

anterior capsular lesions may also be associated

0:47

with this designated slack lesions.

0:50

And there are abnormalities that I've listed here

0:52

to a variety of, uh, structures.

0:57

I'm gonna show you one, I'll talk more about it to, uh,

1:01

later today and show you I think two other examples.

1:05

But this looks like something we're gonna describe later,

1:08

the ALPS lesion, but it occurs higher up.

1:12

This is occurring at two or three o'clock.

1:15

You can see the labral detachment here,

1:18

the nearby middle glen mal ligament, okay,

1:20

which was bifid in this case.

1:22

And you can see stripping

1:24

of the anterior scapular periosteum.

1:27

It looks like a sub labral foramen,

1:29

but it is isolated to the two

1:31

or three o'clock position, unlike the foramen

1:34

that we described yesterday.

1:37

Now let's talk about macro instability.

1:40

And to do that of course we have to introduce Mr as

1:44

Blundell Banhart.

1:46

He was an interesting orthopedic surgeon, somewhat critical

1:49

of other orthopedic surgeons.

1:51

He believed the essential anatomic defect was detachment

1:55

of the anterior labrum

1:57

and the only appropriate surgery is to reattach the labrum.

2:01

And this was one of the quotes

2:02

with only one rational operation for this condition.

2:06

It is almost foolproof.

2:08

And when properly done, the patient is cured

2:10

and then he adds, as he often did,

2:12

when I say the operation is foolproof, I do not mean

2:16

that fools should practice surgery.

2:19

So this was the essential lesion to him.

2:23

I would suggest now that if we're trying

2:25

to describe essential anatomic lesions associated

2:29

with anterior macro instability, these are the ones

2:33

that we've all heard about.

2:34

Detachment of the anterior labrum

2:38

or compression of the anterior labrum and anterior caps.

2:42

A soft tissue bankart lesion, which we'll talk about

2:46

DA defect in the postal lateral portion of the humeral head.

2:50

Of course, that's our old friend, the hill sax lesion,

2:55

an erosion or fracture of the anterior glenoid rim. And

2:58

I'm gonna show you what the bone bank heart lesion can

3:01

look like because indeed there's some variability

3:05

in its appearance.

3:07

So let's start with a hills sax lesion.

3:10

Now I've listed some of the facts related

3:12

to it in the box on your left said to occur in 45

3:16

to 90% of initial dislocations,

3:20

the frequency increases in cases of recurrent dislocation

3:25

and may after several dislocations reach the nineties

3:28

or even 95%.

3:31

One of the important aspects with rare exceptions,

3:34

that occurs at the very top of the humeral head

3:37

and certainly, excuse me,

3:40

certainly within two centimeters

3:43

of the top of the humeral head.

3:45

And that has some importance

3:46

as I'll mention in a minute or so.

3:49

Once you have it, particularly if it is large,

3:53

and particularly if it's oriented in a certain fashion,

3:58

it may predispose to recurrent dislocations.

4:02

Increase size of the hills sax lesion, a certain pattern

4:05

of orientation.

4:07

Those are factors that will lead to a propensity

4:10

to dislocate.

4:11

Again, I show you a classic example here

4:15

with standard Mr.

4:17

And Mr. Arthrography, just to give you an idea

4:20

of what it looks like.

4:22

Now, I used to think this was an easy diagnosis

4:25

with conventional radiography.

4:27

I had no trouble. I typically would look in

4:30

internal rotation and look

4:32

for a contour abnormality in the poster

4:35

superior aspect of the humeral head.

4:38

And long came the cross-sectional techniques.

4:41

And I learned that it's not always that easy

4:44

to diagnose a hill sax lesion

4:46

because there are other things

4:48

that produce irregularity along the posterior superior

4:52

aspect of the humeral head.

4:54

We'll be talking about some cases of, uh,

4:57

internal impingement where you can see cystic changes there.

5:01

The general rule is as you look at the humeral head in a,

5:04

in the axial plane, the defect should be high up.

5:09

So it should appear in the first one, two,

5:13

and certainly third transverse image no matter

5:17

what your spacing is.

5:19

So here's an example of what it looks like in this case

5:22

as we go down with standard mr, it gets larger as we go down

5:26

and ideally it is angular like this.

5:30

All right? This would be a classic example

5:33

and this is what it looks like on the autogram.

5:36

And here's what it might look in the coronal plane.

5:40

Now I tell you all that, that you should see it high up

5:43

because there is a pseudo hill sax lesion.

5:47

As you get lower down, as you get lower down to your third,

5:51

fourth, or fifth transverse, you're gonna see a

5:57

involving this particular region of the humerus

6:00

between the arrows and the bottom two images.

6:04

Now you're too low here to call this a hills sax lesion.

6:07

The hills sax lesion should be higher up in the first two

6:11

or certainly the first three transverse sections.

6:17

Now you're gonna come across engaging versus non engaging

6:22

hills sax lesions.

6:23

So let me define that because it's a bit confusing.

6:27

A non engaging hills sax lesion is a lesion

6:32

that can reengage the anterior glenoid rim,

6:36

but only during a pathologic movement of the humeral head.

6:40

An injury that leads to a pathologic movement

6:44

can in fact lead to engagement.

6:47

An engaging hill sax lesion is a lesion that can reengage

6:51

the anterior glenoid rim during either physiologic

6:56

or pathologic movements.

6:58

So some persons can move their shoulder by themselves,

7:03

no injury and reengage that, uh,

7:07

hills sax lesion.

7:09

So that is the difference between the two terms.

7:11

And they are misleading terms

7:13

because whether we use non engaging

7:16

or engaging, both of those lesions can engage.

7:20

It's just that you require a pathologic process, okay?

7:25

If in fact you're dealing with a non engaging iax lesion.

7:30

Now the question arises how you measurement. Now I know Dr.

7:34

PEs, Dr. Pomerance is going

7:36

to be discussing in more detail these

7:39

particular measurements.

7:40

But let me give you a few ideas of

7:42

what has been written in the literature.

7:46

Some people prefer ct, particularly 3D CT.

7:50

Others prefer Mr or may only have mr.

7:54

So typically measurements are made in the coronal

7:58

and in the axial plane.

8:00

And in the coronal plane,

8:02

typically you use the axial image in which the hills sax

8:05

lesion is the largest.

8:07

And you can see that the width, particularly here,

8:10

a medial lateral width, which is a critical width,

8:14

you can see it there and the depth is, uh, is uh, measured.

8:19

Now if you go to the coronal image, you can see we use

8:22

that same sort of measurements, a depth and a width,

8:27

and they should be somewhat similar,

8:30

although the depth may vary.

8:32

Typically the width is about the same.

8:35

Now, you may express that in terms of a percentage compared

8:38

to the diameter of the best fit circle, it's up to you.

8:42

But also you could just describe in millimeters

8:46

the depth and width.

8:48

The other interesting thing

8:50

that has been suggested if you use 3D CT, is

8:55

To determine the angle between lines

8:58

drawn along the axis of the hills sax lesion

9:02

and that of the humeral shaft.

9:05

The risk of engagement of the hills sax lesion increases

9:10

with its size, with

9:12

and with a horizontal orientation

9:15

with the arm in neutral position.

9:18

And to prove that last point here is a hill sax lesion in

9:23

the neutral position on the left.

9:25

And you can appreciate here in abduction

9:27

and external rotation, it parallels the glenoid margin,

9:31

increasing the risk of re-engagement of

9:35

that I sax lesion.