0:01

We now move on and we'll discuss the tendon pattern,

0:06

the tendon patterns of impingement.

0:08

Now these are generally divided into two types, external,

0:13

something perhaps outside of the cuff itself

0:16

with two subtypes that are emphasized, subacromial

0:20

and subor, and then internal.

0:24

And there are several varieties now of internal.

0:27

The two that are most commonly described are posterosuperior

0:31

and anterosuperior.

0:34

I'm gonna discuss three of these four patterns

0:37

of impingement.

0:40

So let's talk about external impingement.

0:43

The general abnormality that is agreed upon

0:47

by most people about this pattern of impingement

0:51

is narrowing of the subacromial subcoracoid space.

0:55

But it is controversial as to what causes that narrow

1:01

with two theories.

1:03

One theory suggests that it's an intrinsic problem

1:06

of the tendons of the rotator cuff

1:09

that produce the initial abnormalities, degeneration,

1:13

and tearing of the tendons, weakening of those muscles

1:17

because of those tendons

1:19

and an elevation of the humeral head

1:22

with secondary narrowing of the subacromial

1:25

sub corticoid space.

1:27

The alternative theory says, no, no, wait a minute.

1:31

That's not what's going on.

1:32

The initial abnormalities are abnormalities

1:35

of the corco acromial arch

1:38

and those abnormalities lead to narrowing

1:42

of the subacromial subc corticoid space.

1:46

And because of that narrowing,

1:48

and I'll show you exactly why there are abnormalities

1:51

that develop within the subj tendons, perhaps beginning

1:56

as degeneration, but ending up as partial

1:59

or full thickness tearing of those tendons.

2:02

So that is an extrinsic cause, not an intrinsic cause.

2:09

I strongly believe that shoulder impingement is a clinical

2:15

diagnosis, not an imaging diagnosis.

2:18

And I would argue that there may be no foolproof signs.

2:23

One fairly reliable sign that the symptoms

2:27

of impingement are present.

2:29

Now the orthopedic surgeon is armed with a variety of tests

2:33

and they're good near test and the Hawkins test,

2:36

and there are others that are, are listed in the literature.

2:40

Okay? So there are a number of tests.

2:43

Generally they relate to painful elevation

2:46

of the arm in certain positions of that arm.

2:50

So that is the way the diagnosis is made.

2:53

So I really believe it is not our diagnosis to make

2:57

we provide evidence for that diagnosis.

3:02

Now, if you are a believer in the external theory of

3:08

impingement on the rotator cuff tendons,

3:10

this is the story that you would tell.

3:13

There are gonna be some abnormality in the

3:16

cortical acromial arch.

3:18

And that includes of course, the acromium, the clavicle,

3:22

the corco acromial ligament, and other nearby structures.

3:26

And that abnormality produces some sort of mass,

3:31

and that mass pushes down on the external

3:33

surface of the tendon.

3:36

Now the foursome showing

3:37

by the blue arrows here is compression.

3:41

Compression will injure tendons,

3:43

but it is tensile force that is most important

3:47

for tendon tearing.

3:49

So if you believe in this pattern, you're gonna have

3:52

to explain why within external force we get such failure

3:57

of the tears, uh, of the tendon.

4:00

Certainly we can get sal sided fraying

4:03

with this particular picture as I show it.

4:06

Well, the argument that the believers in this theory would

4:10

suggest, oh, wait a minute, as I push down on the top

4:13

of this tendon,

4:15

what will occur is a convexity involving

4:19

the inferior or articular surface of that tendon,

4:24

and through a process of tend

4:27

tensile undersurface fiber failure known as tough.

4:32

That is why articular cited tearing is the

4:36

initial abnormality.

4:38

And indeed what occurs can be full thickness tearing.

4:44

If you believe in this, then any process

4:47

that narrows the subacromial space could lead to

4:51

external subacromial impingement.

4:54

Now, the major finding we see statistically is usually

5:00

osteoarthrosis of the acromial vic of the joint,

5:03

particularly when there is capsular distension

5:06

and osteophytes that are contacting

5:09

or even depressing the myo tendonous junction

5:12

of the supraspinatus.

5:14

Uh, it certainly looks like there is impingement,

5:17

but I would counter, again, I don't think that is diagnostic

5:21

of the clinical features of the impingement syndrome,

5:25

but there are other causes certainly that could lead

5:27

to the structural findings that are required

5:31

for external subacromial infringement.

5:34

And that is why there's been a lot of interest in the shape

5:37

of the acromion, and particularly with the diagnosis

5:42

and identification of an outgrowth

5:45

that is called a subacromial and feso fight,

5:50

or simply a subacromial spur.

5:53

Here's a beautiful example of

5:54

what it looks like in a specimen. Here.

5:56

We can see it in images right here.

6:00

This represents ossification at the acromial attachment

6:04

of the cortical acromial ligament.

6:08

Alright? That's what it looks like.

6:10

That's what it is, and that's why it points

6:12

to the cricoid process

6:15

and of all of the imaging findings that we look for,

6:18

this is the most specific,

6:21

although it is not totally diagnostic,

6:23

it's the most specific.