0:00

Now let's turn our attention now to some chondral

0:04

and osteochondral lesions that may occur.

0:09

The first of these is what has been designated

0:13

osteo gans.

0:15

That's a confusing term.

0:17

We see that particular term applied to the Taylor dome,

0:21

to the femoral condyles, to the patella, to the Capella,

0:25

which I'll talk about tomorrow in the elbow

0:28

and to the glenoid.

0:29

The glenoid is not the most common site.

0:32

The sites above are more common regions to see OCD.

0:37

Now, the pathogenesis

0:39

of OCD probably varies among these sites.

0:42

When you think of involvement, for example,

0:45

of the inner aspect

0:46

of the medial femoral condyle in the knee,

0:49

it probably relates to repetitive stress

0:52

because that's not a common site

0:54

of a single osteochondral injury that could lead later on

0:59

to osteochondritis disc advance.

1:01

Others believe it's not related to stress

1:04

or to trauma at all.

1:05

It's a vascular lesion.

1:07

We see it in the baseball pitcher,

1:09

and I think it relates to repetitive stress

1:12

and it produces an abnormality of cartilage

1:14

or cartilage in bone.

1:16

And it can vary in location,

1:18

but typically is not seen exactly at that bare spot.

1:23

Now remember, the bare spot does produce a normal area

1:26

of cartilage thinning,

1:28

but if you see something that is not centered in the circle

1:32

that occupies the lower two thirds of the glenoid, it's

1:36

probably not a physiologic finding.

1:39

It is pathologic as shown in this condition with depression

1:43

and fragmentation of the subc chondral bone plate and bone.

1:48

Here's another example, again, not sitting

1:51

where we typically see the bare spot.

1:53

So this would be osteochondritis dis.

1:57

The second bony lesion is a little bit different.

2:00

There are very few descriptions of it.

2:03

It's actually Snyder who described it initially.

2:06

It goes by the name of Glo glenoid, articular rim divot

2:10

or the guard lesion.

2:13

Now to understand it, you have to go back to the embryology

2:17

of the glenoid cavity,

2:19

and typically there's a single superior ossification center

2:23

and several inferior ossification centers

2:26

that eventually fuse.

2:28

And their point of fusion is somewhere around 10 o'clock

2:32

posteriorly and maybe around three

2:35

or four o'clock anteriorly.

2:37

And these represent sites I think of weakness.

2:41

The typical guard lesion

2:44

occurs involving the posterior glenoid rim

2:47

and nearby fossa at

2:49

around the 10 o'clock position or so.

2:53

But let me show you what it looks like.

2:55

Here is one example in a professional baseball

2:58

Pitcher.

2:59

You can see that some features look like osteo gans,

3:04

but it's the involvement of the glenoid rim

3:07

here at about maybe nine

3:09

or 10 o'clock that makes this a guard lesion.

3:13

These tend to be, uh, painful.

3:16

Another finding that will occur

3:20

in this same sort of region relates

3:23

to a change in the morphology of the glenoid rim.

3:28

You get erosion and rounding off

3:30

of the posterior glenoid over time in the baseball pitcher.

3:34

Now, some people will indicate that

3:36

because of this one gets retroversion

3:40

of the glenoid articular surface.

3:42

So I wanted to say a couple words about retroversion.

3:46

The typical way that we measure retroversion

3:49

of the glenoid articular surface on ct

3:52

or Mr requires that we have the tip

3:55

of the scapula in the image.

3:58

And what you'll do somewhere

3:59

around the mid glenoid level is draw a line along the

4:03

articular surface and another line to the tip

4:07

of the scapula.

4:08

You'll connect them. And here you can see there

4:11

is retroversion.

4:13

Now there are a few problems with establishing the version

4:16

of the glenoid articular surface.

4:18

Number one, it varies as you look at different levels.

4:22

So it's not always neutral version.

4:25

It may be normally some retroversion.

4:28

And the second problem is using the scapular tip

4:32

as a reference point is ridiculous.

4:34

That's not even part of the glen humeral joint.

4:37

That's the scapular thoracic joint.

4:40

So a lot of people more recently suggest

4:42

that you use this triangular region just deep

4:46

to the subc chondral bone plate.

4:48

This is the glenoid vault.

4:51

And if you go into the literature, you'll see a number

4:53

of articles that have talked about this

4:55

particular structure.

4:57

And the way to determine version

4:59

of the glenoid articular surface would reference

5:03

to this structure, not the tip of the scapula.

5:06

And I believe that is a more

5:08

valuable way in determining glenoid version.

5:12

And you don't require wide images.

5:14

The glenoid vault is always right there.