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Today, we're honored to welcome Dr. Jon Jacobson
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for a lecture on ultrasound of
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the rotator cuff with MRI correlation.
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Dr. Jacobson is a professor of Radiology
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and Section Chief of Muscular Skeletal Imaging
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in the Department of Radiology
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at the University Of Cincinnati.
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His academic achievements include over
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250 peer-reviewed publications
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and many invited national
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and international lectures or workshops.
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At the end of the lecture,
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join Dr. Jacobson in a Q and A session
1:09
where he will address any questions you may
1:11
have on today's topic.
1:12
Please use the Q and A feature to submit your
1:15
question at any time during the lecture.
1:16
With that being said,
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we are ready to begin today's lecture.
1:19
Dr. Jacobson, please take it from here.
1:22
Perfect.
1:23
Okay, let's get going here.
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So, my name is Jon Jacobson.
1:26
I'll be talking about ultrasound of the
1:27
rotator cuff with MRI correlation.
1:31
A few disclosures I'd like to make.
1:33
First of all,
1:34
I want to mention that I put the syllabus of this
1:37
lecture on my website. There's the address.
1:41
I put other educational material related to
1:44
MS ultrasound on there as well,
1:46
but disclosures include consultant
1:48
for Bioclinica, Book Royalties and Elsevier.
1:50
Advisory Board: Phillips,
1:52
Medical Board: POCUSPRO.
1:54
I also have to disclose that
1:56
I no longer eat Skittles.
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So, let's start out with a few general comments
2:01
about the rotator cuff.
2:03
Of course,
2:03
the rotator cuff consists of four different structures.
2:07
At the top, the supraspinatus.
2:08
In the front, the subscapularis;
2:11
posteriorly, the infraspinatus and teres minor.
2:13
Note: the biceps long head tendon coursing superiorly.
2:17
Also want to point out what's colored in light blue.
2:19
And that is the subacromial subdeltoid bursa.
2:21
As the name implies,
2:23
it not only is located under the acromion,
2:25
but wherever you see the deltoid,
2:27
which is removed on this image,
2:29
you'll have that bursa.
2:30
So, it covers many parts of the rotator cuff.
2:36
So, a few basics about ultrasound of
2:39
the musculoskeletal system.
2:40
Tendons are hyperechoic and fibrillar,
2:43
as indicated with the letter T,
2:45
showing the supraspinatus tendon.
2:48
Muscle is relatively hypoechoic,
2:51
although you can see the linear characteristic
2:53
fiber adipose layer is within the muscle tissue.
2:56
Note the echogenic contours of the bone.
2:59
Now, this is a very important point.
3:01
The bone landmarks are essential when performing
3:04
musculoskeletal ultrasound.
3:05
Really, for three reasons.
3:07
One reason is
3:10
that's how you get your orientation.
3:11
You can appreciate the humeral head and
3:14
the shelf of the greater tuberosity,
3:15
simulating what you see on an MRI.
3:18
The second is,
3:19
once you identify the specific bone contours
3:22
that are the footprints of the tendons,
3:24
then you know which tendon you're looking at.
3:26
And the third point, as we age,
3:28
the tendons tend to wear out, or with attrition,
3:31
they occur at those footprints.
3:33
So this is where the money is going to be most
3:35
of the time when looking for pathology.
3:37
So, bone landmarks are really critical.
3:40
Now, there's an artifact that we have to talk about
3:43
when performing musculoskeletal ultrasound,
3:44
and it's called Anisotropy.
3:46
So, what is this?
3:48
Well, this occurs when a structure,
3:51
which is normally hyperechoic,
3:53
is artifactually hypoechoic,
3:54
which can stimulate pathology.
3:57
So, what does this mean and how does it occur?
4:01
Well, if we look here at the segment of tendon,
4:03
these fibers are perpendicular
4:05
to the sound beam.
4:07
So when the sound beam is propagated through
4:09
the soft tissues, it hits these interfaces,
4:12
reflects back up to the transducer,
4:14
and the image is made. Now, the problem is,
4:17
when these interfaces become
4:19
more and more oblique,
4:21
the sound beam propagates through
4:22
the soft tissues.
4:23
But instead of reflecting
4:25
back to the transducer,
4:26
it reflects away from the transducer.
4:28
And the more this is obliqued,
4:31
the more this goes away from the transducer,
4:34
and the tendon will appear more and more hypoechoic.
4:37
Now, it's not just tendons.
4:39
As you know,
4:40
when you guide a needle using ultrasound,
4:42
when the needle becomes oblique and when it
4:44
eventually is 45 degrees to the sound beam,
4:47
it becomes almost invisible.
4:49
So this is anisotropy of any linear structure.
4:53
It only takes about five degrees,
4:55
essentially three to five degrees of angulation
4:57
to make this come and go. So what happens is,
5:00
while we're scanning,
5:00
we're continually moving the transducer.
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When we see a hypoechic area,
5:05
we rock the transducer, hit it at 90 degrees,
5:08
and if it fills in, it's an artifact.
5:11
Okay, the supraspinatus. Let's focus on that.
5:14
Of course,
5:14
the most important tendon of the rotator cuff,
5:17
most commonly torn.
5:19
Here is the long axis view,
5:21
and here is the short axis view.
5:23
Again, hyperechoic and fibrillar.
5:26
Note the convex superior outer surface. Very important.
5:30
And on the short axis, a very uniform thickness.
5:34
When we're over the humeral head,
5:36
here is the hypoechoic hyaline cartilage.
5:38
So this uniform rind of tissue
5:41
is important to see,
5:42
just like we see on an MRI in a
5:44
sagittal oblique image over the humeral head.
5:47
So, to me, this is analogous to a tire on a wheel rim.
5:51
Now, incidentally,
5:51
this is from the Uniroyal tire plant outside of Detroit.
5:57
If you travel west from the Detroit metropolitan airport,
6:00
I'm from Detroit,
6:00
you'll see this next to the freeway.
6:02
Now, these fences are put up,
6:04
these are like 20-foot fences because people
6:06
tried to roll this down the freeway.
6:08
Trust me, it won't work.
6:11
Incidentally, this was initially made for the 1965
6:14
World's Fair in New York City,
6:16
where initially it was a Ferris wheel.
6:18
But let's get back to what's important here.
6:21
Ultrasound.
6:22
Okay, so technical considerations.
6:25
12 to 15 MHz or twelve to 18 MHz
6:28
is the sweet spot for most rotator cuff evaluations.
6:31
Anything over ten will do.
6:33
Anything over 20 sometimes is just
6:35
not enough depth penetration.
6:36
Of those two views of the supraspinatus,
6:39
the long axis view is most important.
6:41
I start with that view.
6:43
There's less pitfalls,
6:44
you recognize the anatomy better,
6:46
and you can diagnose with 90% accuracy with that
6:49
long axis view alone. Although, of course,
6:52
one view is not enough.
6:54
Also, in addition to the bone contours as an important
6:57
landmark, which I mentioned earlier,
6:59
the biceps tendon intra-articular and the rotator interval.
7:02
Another very important landmark.
7:05
More on that in just a moment.
7:07
So, let's continue by talking about the normal
7:09
anatomy and the scanning technique.
7:11
So, here is the long axis view of the supraspinatus.
7:15
When I turn 90 degrees over the humeral head,
7:18
that's when I see the characteristic
7:20
curve of the humeral head,
7:22
the hypoechoic hyaline cartilage,
7:24
and the uniform thickness of the tendon.
7:27
Now, as I move the transducer more distally,
7:30
leaving the articular surface and now venturing
7:33
into the greater tuberosity and its facets,
7:37
we now lose the rounded appearance
7:39
with the hyaline cartilage,
7:40
and it's replaced with this angulated appearance,
7:43
like a shallow roof of a house.
7:46
This will separate the superior
7:48
and middle facets.
7:49
Note that the tendon now is becoming thinner as
7:52
it is attaching to the greater tuberosity.
7:55
Now, recognizing these facets is
7:58
really quite important,
8:00
because when you're looking at a tendon
8:01
in the short axis, you have to decide,
8:03
let's say when there's a tear.
8:05
Is it supraspinatus?
8:06
Is it infraspinatus?
8:07
Is it both?
8:08
How do we make this distinction?
8:10
Well, I rely on the bone landmarks
8:12
for this distinction.
8:14
Looking at the illustration on the left,
8:16
here is the roof of the house that we see,
8:19
the superior and middle facets with this apex.
8:21
Now, the size of the superior facet is somewhat
8:24
variable, but this is what I'm looking for,
8:27
because I know that the supraspinatus
8:29
attaches to the superior facet,
8:30
and some of the fibers
8:32
flop over and attach at the middle facet
8:35
and the infraspinatus overlaps.
8:37
Now, I do recognize that the five layers of the
8:39
rotator cuff, there's variability,
8:41
and fibers do sometimes move
8:44
into different directions,
8:46
but the majority of the tendon will have
8:48
disappearance at imaging as they attach
8:51
to their facets at their footprints.
8:53
Here is the biceps tendon,
8:55
an important landmark to let me know that
8:57
I'm looking at the most superior aspect
8:59
of the supraspinatus.
9:01
Now, here is a video clip showing,
9:05
starting at the humeral head,
9:06
the short-axis view of the supraspinatus.
9:09
Incidentally, the thickened hypoechoic subacromial
9:12
subdeltoid bursa is here.
9:14
The bursal walls are bright.
9:16
This is an abnormally thickened bursa.
9:18
But back to the supraspinatus.
9:19
We have a uniform rind. And as we move distally,
9:23
look what happens as we get to the apex.
9:25
Right there.
9:26
And I'll slow this down and stop right there.
9:29
At that point, we've left the articular surface.
9:32
And now we have the supraspinatus doing this,
9:35
the infraspinatus doing this.
9:38
So, identifying the bone contours
9:40
helps with our orientation.
9:42
And I apply this to MRI as well,
9:43
although the resolution is higher here
9:45
with ultrasound.
9:48
So, differentiating supraspinatus and
9:51
infraspinatus in its short axis,
9:53
I just talked about using the bone landmarks.
9:56
I can do the same thing in long axis.
9:59
And let me explain.
10:01
Well, first of all,
10:02
note the angle between the superior facet and
10:05
the humeral head is more well-defined
10:08
than the angle between the middle facet
10:10
and the humeral head. This is considerably flat.
10:13
So just by scanning a long axis,
10:15
I can tell by these bone contours if I'm
10:18
at the superior facet or the middle facet.
10:21
When I'm over the superior facet,
10:24
we know that this is a long-axis view,
10:26
the supraspinatus.
10:28
As I get to the middle facet more posteriorly,
10:30
I now know, based on the anatomy,
10:33
that the infraspinatus is going to overlap the supraspinatus.
10:38
Taken from the literature,
10:39
if you look at this image,
10:41
images on the bottom left,
10:42
you could see the supraspinatus here.
10:45
And then here's the infraspinatus
10:47
obliquely coming over the top.
10:50
Now, also look with ultrasound what
10:52
we note in this overlap area.
10:55
This is the infraspinatus,
10:57
this flattened tendon,
10:59
but this serrated appearance or
11:02
these linear hypoechoic areas,
11:04
this is the characteristic appearance
11:06
of the infraspinatus.
11:07
Here's the supraspinatus here going underneath.
11:11
So, we're able to identify the infraspinatus and
11:15
supraspinatus based on the bone contours
11:17
and the intrinsic appearance of the infraspinatus.
11:22
Now when I look at the infraspinatus in this view,
11:25
to me, it's analogous to a deflated football.
11:28
Apologies to the Patriots fans,
11:30
but to me it looks like a squished football,
11:33
this being the laces of the football.
11:38
Okay, rotator cuff tears.
11:39
How well does ultrasound perform?
11:42
Well, all the papers show that ultrasound and MRI
11:46
are equal in accuracy.
11:49
Of course, like everything,
11:50
you have to be trained and have experience.
11:52
There is a variability in MRI interpretation,
11:55
just like this variability
11:57
in obtaining images with ultrasound.
12:00
So, there's variability with both.
12:02
You can see with full-thickness tears,
12:04
MR Arthrography, MRI, and ultrasound, over 90%.
12:06
That's what we want.
12:07
MR Arthrography, more specific.
12:11
Now, partial tears, the numbers are lower
12:14
because the tears are smaller,
12:15
where MRI and ultrasound are,
12:19
again, fairly equal but lower.
12:21
But because many of these partial tears
12:22
are articular-sided that will fill with contrast,
12:27
MR Arthrography is more specific
12:29
and is also more sensitive.
12:34
Okay, so what do rotator cuff tears
12:35
look like on ultrasound?
12:38
Well, the normal tendon is hyperechoic.
12:40
Therefore, a defect will be hypoechoic or anechoic,
12:44
meaning the defect will fill with fluid,
12:47
with hemorrhage, with granulation tissue,
12:49
with synovium.
12:50
Now, I'm going to be talking about four indirect
12:53
signs of rotator cuff tears.
12:55
I want to mention two upfront because
12:57
they're very important,
12:58
and I'm going to emphasize them
12:59
throughout this talk.
13:01
The first, cortical irregularity,
13:03
specifically at the supraspinatus footprint.
13:05
In fact, if you see this on a radiograph,
13:09
three out of four patients will have a tear.
13:11
Actually, in my experience,
13:13
it's probably closer to 85% and 90%
13:15
will have a tear,
13:16
and you do not see that cortical irregularity with tendinosis.
13:20
Now, the other indirect sign is volume
13:22
loss or thinning of the tendon,
13:24
where the superior convexity is flattened.
13:27
More on that in just a moment.
13:28
And at the end of the spectrum,
13:30
when the tendon is torn and retracted under
13:32
the acromion, there's nonvisualization.
13:36
Okay, so if we look at rotator cuff tears,
13:39
the supraspinatus is, of course, the most common.
13:42
With larger tears,
13:43
they can extend anteriorly
13:45
into the subscapularis.
13:46
They can extend inferiorly to the infraspinatus,
13:49
uncommonly isolated tears of
13:51
those other two tendons.
13:53
When patients are under the age of 35 or 40,
13:56
rotator cuff tears are not very common.
13:58
Now, the problem is they tend to be smaller,
14:01
partial, articular, and anterior.
14:03
As you know, our numbers go down in accuracy.
14:07
What's important,
14:08
papers have shown up to 30% to 40% of patients,
14:12
if they're under the age of 40
14:14
and have a rotator cuff tear,
14:17
will also have labral pathology.
14:18
As you know, ultrasound is not very good
14:21
at looking at the labrum.
14:22
So, one algorithm would be based
14:24
on the patient's age.
14:25
The younger the patient,
14:27
meaning under 40 or 35,
14:28
perhaps an MRI would be
14:30
the best imaging test to go first.
14:33
And maybe an MR Arthrogram,
14:34
if you have a high suspicion of a labral tear.
14:37
On the contrary, as you age over 40 and 50,
14:41
that's when we see degenerative tears.
14:44
The information about the labrum
14:45
may be less important.
14:47
They tend to occur at the posterior
14:48
aspect of the supraspinatus.
14:50
And again, when large,
14:52
can extend anterior or posterior.
14:54
All right. So when I look at the rotator cuff
14:58
by MRI and ultrasound,
15:00
I try to put the abnormality into one of these
15:04
categories: partial tear, full-thickness tear,
15:07
and tendinosis.
15:08
So, let's talk about that in more detail.
15:12
First, another few points about anatomy.
15:14
The anatomy is so key.
15:16
So there are actually three surfaces
15:18
to the rotator cuff tendons.
15:20
You have the bursal surface and the articular
15:23
surface, and the greater tuberosity surface.
15:25
It's a shelf of bone,
15:27
a broad shelf that actually represents another surface.
15:31
Similar to what we see on the MRI.
15:35
Now, when people talk about the supraspinatus on
15:38
ultrasound, and even to less extent,
15:40
on MRI, the analogy is it looks like a bird's beak.
15:44
And I really don't like that analogy because all the
15:47
birds I've seen, their beaks come to a point,
15:50
except maybe a toucan.
15:52
But I won't get into that.
15:53
The point is,
15:54
it doesn't really come to a point.
15:56
If you can see here by these images,
15:58
the bursal fibers attach out here,
16:00
the articular fibers here,
16:02
and the fibers in between.
16:04
In between.In between.
16:04
So, it's actually a broad attachment.
16:06
They call that the footprint.
16:08
Any ligament or tendon attachment to bone,
16:11
that surface area is called the footprint.
16:14
So rather than a bird's beak,
16:16
I think this is more analogous to a rainbow.
16:20
So that's just one way to think about it.
16:24
Okay.
16:24
So, when you see a defect of a
16:27
tendon by ultrasound or MRI,
16:28
here's an example where it's touching
16:31
the articular surface,
16:33
not going to the bursal surface, therefore,
16:36
a partial-thickness articular-sided tear.
16:38
Note the cortical irregularity that occurs
16:41
with these attrition tears as we age,
16:43
where the fibers are tearing off the bone,
16:46
creating the bone irregularity.
16:47
The Sharpey's fibers.
16:48
Now, there are other terms for this,
16:50
which makes it somewhat confusing.
16:52
A Rim-rent tear is an older term, a PASTA lesion.
16:56
First of all, I don't like acronyms.
17:00
We forget what they stand for.
17:01
In fact, if you put pasta into PubMed,
17:05
there are now three different
17:06
definitions of PASTA.
17:09
Partial articular sided tendon bulge is one of
17:12
the three. So I just call it what it is.
17:14
It's a partial-thickness articular-sided tear.
17:17
Yeah, I don't like acronyms.
17:19
Maybe I should make an acronym for that, IDLA.
17:23
There you go.
17:24
Okay, how about a bursal-sided partial tear?
17:27
Well, there's the defect touching the bursal surface,
17:31
not touching the articular surface,
17:33
therefore not a full-thickness tear.
17:36
Now, note it is touching the bone.
17:38
So, it's incorrect to say that a bursal defect
17:41
touching bone is a full-thickness tear.
17:43
That's incorrect.
17:44
It has to touch the articular surface.
17:47
In fact, most bursal-sided tears do occur at their bony
17:51
attachment as we age.
17:52
That's where it happens.
17:54
And there's the cortical irregularity.
17:57
And because the tendon is really not a bird's beak,
18:00
but rather more like a rainbow.
18:02
You could have defects within
18:03
the tendon such as this,
18:05
where it wouldn't be seen at
18:07
arthroscopy or B, note, the cortical irregularity.
18:11
Know these illustrations,
18:12
I'm putting the biceps for orientation.
18:14
Very important.
18:15
Then finally, the full-thickness tear,
18:17
going from bursal to articular surface.
18:19
Note the significant remodeling and the greater
18:21
tuberosity that occurs with these larger,
18:25
more chronic tears.
18:28
So, also remember that the supraspinatus
18:31
is not a cable-like structure.
18:33
It's more like a flattened structure,
18:36
like a piece of lasagna or something like that.
18:38
So when you have a full-thickness tear,
18:41
which is defined as a defect going from
18:43
the articular to bursal surface,
18:45
it could be focal like this,
18:48
or it could be full-width.
18:50
So, you can either use those terms
18:52
or simply measure the width.
18:53
But just be aware that when you
18:55
have a full-thickness tear,
18:56
we have to consider the width
18:58
or the extent of that tear.
19:02
All right,
19:02
let's move on to supraspinatus pathology.
19:06
Those were a lot of general comments,
19:07
but the anatomy is really quite important.
19:10
So, let's get to it and show some examples.
19:14
Here we see, on your left,
19:15
a well-defined hypoechoic area
19:18
that persisted no matter how we move the transducer,
19:21
touching the articular surface,
19:23
the rounded surface of the bone,
19:25
there's the hypoechoic hyaline cartilage
19:27
not going to the bursal surface,
19:29
therefore a partial-thickness articular-sided tear.
19:32
I would have measured it as maybe 3 mm in length.
19:34
We would measure its width in the other plane.
19:37
I would say it's about 40% deep
19:40
or maybe up to 50% depth.
19:42
Now, we use the term long and short axis with
19:45
ultrasound because we're not looking at the body
19:48
from an external perspective
19:50
as coronal and sagittal.
19:51
As you can see here with the hand on the hip,
19:54
this transducer is pointing at the patient's ear.
19:56
We're not in a coronal or sagittal plane.
19:58
We're following the joint around.
20:00
So we're always talking about the axis relative
20:02
to the structure of interest.
20:04
Now, note here on the right,
20:05
a fluid-sensitive MR image.
20:08
It's essentially an inverted image from the ultrasound.
20:13
The tendon here normally is dark.
20:15
The tendon is normally bright on ultrasound.
20:17
The tear is bright. They usually are on MR.
20:21
And here it's dark. The bone cortex is dark.
20:23
Here the bone is bright.
20:25
So it's really the same thing.
20:27
So if you can make your ultrasound
20:29
look like an MR,
20:31
you're home free because it's the same anatomy,
20:34
it's the same pathology.
20:36
You just have to work on getting the bone
20:39
landmarks and seeing the tendon perfectly in
20:41
long axis or short axis without an artifact.
20:44
But that's what we do with MR anyways.
20:47
Now, there's one significant pitfall with these
20:49
partial articular-sided tears,
20:51
and it relates to focal anisotropy.
20:54
Let me explain what this is
20:56
and how we can avoid this.
20:57
So when we think about anisotropy, just like
21:00
magic angle phenomenon, and with MRI,
21:02
it tends to be all or nothing,
21:04
where an entire segment of tendon
21:06
will have the artifact.
21:08
But the problem here is you could have focal
21:11
anisotropy that looks exactly like a partial
21:13
articular-sided tear.
21:14
First of all, why do we have this appearance?
21:17
Well, this is explained by the anatomy.
21:20
Proximally, while the tendon fibers are more uniform,
21:22
look what happens at its footprint.
21:24
Most of the tendon is going straight,
21:27
but right here,
21:28
these articular side fibers are making
21:30
an abrupt turn.
21:31
Therefore, this area right here is prone to focal
21:35
anisotropy, while the outer part is still normal.
21:38
So how do we avoid this? Well, first of all,
21:41
when you look here and say, well, first,
21:43
I don't see tremendous bone irregularity,
21:45
which would make me think
21:46
maybe it's an artifact,
21:48
but maybe it is tendinosis and that's why we
21:50
don't have the bone irregularity.
21:52
Well, what we simply do is we recognize
21:54
that this is a pitfall location,
21:56
and then we heel toe and move the transducer.
21:59
Look what happens with this hypoechoic
22:01
area as they start the Sydney clip.
22:03
I'm barely moving the transducer and
22:06
it completely fills in.
22:07
Now, there's a little calcification here,
22:09
I'll give you that. But the, quote,
22:11
defect goes from now tear to normal.
22:14
So, just be aware.
22:16
I've seen this error being made with even some
22:19
of the most experienced sonographers and
22:22
radiologists because it's really tricky.
22:24
So this is one thing I've learned over the years
22:27
about this focal anisotropy simulating
22:29
a partial articular tear.
22:32
Here are some other examples
22:33
with MR correlation.
22:35
Focal, hypoechoic, touching the hyaline cartilage,
22:38
not touching the bursa.
22:40
Here it is bright on T2 MR image.
22:43
Here's the width of it.
22:44
Note, this is called the cartilage interface sign.
22:47
We normally see a thin white
22:49
line over the cartilage,
22:50
but when fluid is laying on top of it,
22:53
such as filling in a tear,
22:56
that linear echo will become brighter.
23:01
Okay, let's move on to partial-thickness
23:03
bursal sided tears. Now, the pitfall with these,
23:06
because they're often related to impingement,
23:09
is that the bursa is going to be thickened and
23:12
the defect will then often be filled in with
23:15
synovium and other tissue, which can,
23:16
at first glance, simulate tendon.
23:18
If we look here on the MR first,
23:21
the outer border of the supraspinatus should
23:23
come over like this. But instead, it dives in.
23:26
We have this triangular defect filled with
23:29
debris from the bursa, and here it is as well.
23:33
So, it's important not to call this tendon.
23:35
It doesn't look like tendon.
23:36
The tendon is actually doing this.
23:38
And I would say this is about 75% uncovered,
23:42
75% depth with maybe about 4 mm in length.
23:46
But it's not touching the hyaline cartilage,
23:48
therefore not a full-thickness tear.
23:51
Here's a companion case.
23:53
There's the hypoechoic area.
23:55
Note the cortical irregularity,
23:57
one of the important indirect signs,
23:59
and there's the volume loss,
24:01
the other important indirect sign.
24:04
So I find that this volume loss,
24:06
or loss of normal superior convexity,
24:08
is often brought out best in its short-axis view,
24:12
as we can see here.
24:14
There's the cortical irregularity as well.
24:16
So this, to me,
24:17
is analogous to a flattened tire appearance.
24:20
Whereas I mentioned over the humeral head,
24:22
you should have a nice rounded appearance
24:25
of a tire on a wheel rim.
24:28
Another companion case with MR correlation.
24:30
Note the cortical irregularity.
24:32
There's the defect, there's the volume loss.
24:35
Here's the volume loss.
24:37
Now, I'm not pushing excessively to
24:39
make this volume loss occur.
24:41
It just happens with the normal transducer pressure.
24:44
Of course, cortical irregularity.
24:46
Very difficult to see on MR.
24:48
You do appreciate the thinning of the tendon
24:50
though, just like we see on the ultrasound.
24:54
Okay, here is a full-thickness tear.
24:56
It's going from the articular surface to
24:59
the bursal surface.
25:00
The first point,
25:01
it's filled with fluid. It's anechoic.
25:04
When you have fluid within a tear,
25:06
which occurs more commonly with an acute tear,
25:10
our accuracy goes really high.
25:12
This is 100% accuracy.
25:13
Well, 99.9%.
25:14
Nothing's 100%.
25:16
The point is, you can see the end
25:18
of the tendon very easily.
25:19
Here's that cartilage interface sign where the
25:21
normal bright line is brighter than normal
25:24
because fluid is laying on it.
25:26
So that's telling me,
25:27
indeed, it's touching the articular surface.
25:30
So we have this full-thickness tear and we have to decide,
25:33
is it focal or is it full-width?
25:36
Okay, I'm going to go to the short axis
25:38
to help with that.
25:39
Here is the cartilage interface sign,
25:41
humeral head. There's the width of the tear.
25:44
So, I'm going to do is I'll move the transducer
25:45
more distally and I'll look at this shape of the
25:49
roof of a house showing the superior and middle facets.
25:53
So now, if I look at this image,
25:56
if I were to color in the area where I think the
25:59
tear is on the illustration, it would be here.
26:02
It's the posterior part of the supraspinatus.
26:05
The anterior part is still there with tendinosis.
26:08
Here's the infraspinatus that's still intact.
26:11
And indeed,
26:12
the most common site of a degenerative
26:14
supraspinatus tear is posteriorly right over this apex.
26:20
Okay.
26:20
Here's another case, but this is a larger tear.
26:23
Look at the degree of retraction here.
26:27
There's hyaline cartilage interface,
26:28
there's corticoregularity,
26:30
and this is really thinned
26:31
because there's no tendon there.
26:33
It's just fluid.
26:34
In short axis,
26:36
we can appreciate the thickness of the
26:38
infraspinatus and rather than that coming all
26:40
the way around with a uniform thickness,
26:42
it just thins out to really the collapsed bursa and fluid.
26:46
Here's the biceps tendon.
26:47
Again, a very important landmark to note that we're
26:50
looking at the most anterior
26:52
aspect of the supraspinatus.
26:53
So how about if we were to determine,
26:56
is this full width?
26:57
Well, this one is.
26:59
I would say this whole area,
27:01
the superior facet has no tendon.
27:03
The middle facet here,
27:05
where we expect to see supraspinatus, is missing.
27:08
There's the biceps.
27:09
So this is a full-width, full-thickness tear.
27:12
Or you could measure because they're usually
27:14
about 2.2 to 2.3 or larger centimeters in width
27:18
when the entire supraspinatus is torn.
27:22
Here, just showing that case with MR correlation,
27:25
I think you can appreciate the retraction of the tendon.
27:29
You see the normal infraspinatus
27:31
and no tendon anteriorly.
27:35
And then this whole idea of looking at facets,
27:37
I use that when I interpret MR as well.
27:40
Here's the superior facet,
27:41
there's the middle facet.
27:42
We see no tendon here,
27:44
and where it should flop over, it's missing.
27:46
And here's the infraspinatus coming in
27:49
from the more posterior aspect.
27:53
Now the pitfall with these full-width,
27:55
full-thickness retracted tears is when it's a chronic tear,
28:00
because a rule of thumb is
28:02
with ultrasound and MR, for that matter,
28:05
with more chronic pathology, tendon problems,
28:07
ligament problems, when the fluid goes away,
28:10
is resorbed, we just can't define things as well.
28:14
So unlike that acute foldicus tear where we saw
28:17
fluid outlining the end of the tendon, here,
28:20
the fluid has been resorbed and we just see this
28:23
gradual tapering of the tendon and
28:24
it's hard to see the end of it.
28:26
It's actually...
28:28
It's right here.
28:28
But you probably measure it from here because
28:30
you can't put a suture through that.
28:32
The other difficulty is,
28:33
with all the remodeling,
28:35
you have to really use your imagination to say
28:37
this is where the shelf of the tuberosity
28:39
should be at its footprint.
28:41
So, I'd measure it from here to there.
28:44
But that's the pitfall
28:45
with any chronic tendon problem by imaging,
28:48
is when the fluid is reabsorbed.
28:50
Here's an intrasubstance tear.
28:53
There's the defect.
28:55
There's the cortical irregularity,
28:57
not touching the hyaline cartilage, but close,
29:01
not touching the collapsed hypoechoic
29:04
subacromial subdeltoid bursa.
29:06
Note here the lack of the cartilage interface sign,
29:09
although it's pretty darn close,
29:11
but I would say it's not touching
29:14
the articular surface.
29:16
All right, let's move on from tendon tear to tendinosis.
29:20
First nomenclature.
29:21
We do not use the term tendonitis because the
29:26
inflammatory cells are gone by day five or
29:29
seven in any tendon in the body.
29:31
Now, I do recognize there is a background of inflammatory
29:34
mediators with every pathology in the body.
29:37
For example, if you look at,
29:40
let's say, thyroid cancer.
29:42
There are inflammatory mediators just because
29:44
they are present with thyroid cancer,
29:46
I'm not going to call it thyroiditis.
29:48
The point here is we're calling it tendinosis.
29:51
The other thing is that we know that putting
29:54
steroids into the tendon is bad.
29:56
Putting steroids over tendinosis will give you
29:59
short-term pain relief because it stabilizes
30:02
the nerve endings,
30:03
but has nothing to do with inflammation.
30:05
So we're trying to establish why
30:07
are we injecting steroids?
30:09
Where is it helping?
30:10
Calling the disease or the pathology what it is
30:13
is the first step.
30:14
Another side point,
30:16
the term tendinopathy.
30:17
That is an ambiguous term.
30:19
Many of the clinicians I talk to around the country,
30:21
when you say tendinopathy,
30:23
that means pathology of tendon,
30:25
including tendinosis, calcific tendonitis,
30:29
tendon tear, and even tenosynovitis,
30:32
and other tendons.
30:33
Where many radiologists, especially in Europe,
30:36
they use the term tendinopathy,
30:38
synonymous with tendinosis.
30:40
I'm not here to tell you what
30:41
word you should use,
30:42
but just realize there may be ambiguity
30:44
in some of the terminology.
30:46
This is why I'm sticking with the word tendinosis.
30:49
It consists of mucoid degeneration, primarily,
30:51
chondroid metaplasia.
30:53
Here are the obligatory histology slides
30:56
with arrows pointing at things.
30:59
So, tendinosis will appear hypoechoic.
31:02
How do we distinguish this from a tendon tear?
31:05
Well, the rule of thumb is the more anechoic,
31:08
well-defined, and homogeneous,
31:10
the more likely it's a tendon tear.
31:13
Where if it's more ill-defined and heterogeneous,
31:16
it is tendinosis.
31:18
By the way, heterogeneous is not a word
31:21
in the medical dictionaries used with pathology,
31:27
not to get on this topic.
31:28
Heterogeneous is a term that's used
31:31
in biology but not in the human body.
31:34
Just like homogeneous has to do with milk.
31:36
Homogeneous...
31:38
Whatever.
31:38
I'm going off on a tangent.
31:40
Let me get back to the two
31:42
most important indirect signs:
31:44
volume loss and bone irregularity.
31:47
This is how I make the distinction between
31:50
tendon tear and tendinosis.
31:52
Tendinosis,
31:52
the tendon will tend to be enlarged,
31:54
especially if it's moderate or severe,
31:56
but the bone is smooth at its footprint.
31:59
Where a tear,
32:00
we will look for these two important indirect signs
32:03
of cortical irregularity and thinning.
32:05
Here's a case of tendinosis.
32:08
The tendon is diffusely hypoechoic.
32:11
However, it's not a discrete abnormality.
32:14
The bone is completely smooth.
32:17
There's no loss of the normal convexity.
32:19
And as you know, with MRI,
32:21
gray signal equal the muscle
32:23
is characteristic for tendinosis.
32:26
All right,
32:27
as we leave rotator cuff pathology,
32:30
we need to always include information
32:32
about fatty infiltration.
32:33
And then when the muscle is small,
32:36
the muscle bulk is small. Fatty atrophy.
32:39
We know that there's one finding that predicts
32:43
if a repaired cuff tear will actually do well by MRI,
32:48
that would be the infraspinatus.
32:51
That this one paper said was the only variable
32:53
to predict cuff healing. So fortunately,
32:55
we can see that really easily with ultrasound.
32:58
I look at the supraspinatus too.
33:00
But the infraspinatus is the most important
33:02
structure to talk about fatty infiltration
33:05
and muscle atrophy.
33:06
We know that the larger and the more
33:09
chronic rotator cuff tears,
33:10
especially the ones that are more anterior involving
33:14
the rotator cable,
33:16
are more likely to retract
33:18
and create this problem.
33:21
Ultrasound is comparable to MRI is what it says.
33:24
To be honest, mild atrophy,
33:26
mild fat infiltration, MR will do better.
33:29
But when you get to grade 3 or 4 goutallier on MR or CT,
33:33
ultrasound will be fine.
33:35
You can see it.
33:38
So what I do is I look, in short axis, of the infraspinatus
33:43
compared to the teres minor.
33:44
The key bone landmark is this ridge of bone in
33:47
the scapula to identify the muscle-tendon
33:50
junctions of these two,
33:51
where the infraspinatus is normally
33:53
twice as large as the teres minor.
33:55
Here you can see it's almost the same size,
33:58
telling me there's atrophy.
33:59
Also note that the muscle, rather than hypoechoic
34:03
is echogenic and the tendon-muscle
34:05
differentiation is gone.
34:06
Now, as an aside,
34:08
I never compare to the deltoid,
34:10
I never compare to the trapezius.
34:12
In patients with a large BMI,
34:14
especially those who are diabetic,
34:16
we often see fatty infiltration.
34:18
But the teres minor is normal in 97% of rotator cuffs.
34:23
So, that is my intrinsic standard.
34:25
In the long axis,
34:26
you'll see that all these interfaces will
34:29
attenuate the sound beam, making it difficult.
34:32
Now, let me just make a side point about the physics
34:35
of what's going on here, because I think
34:36
this is important to understand.
34:38
So, what does pure fat look like on ultrasound?
34:41
Well, it's nearly anechoic.
34:43
This is fat here with these fibrous layers in between.
34:47
Muscle is hypoechoic.
34:49
So you might ask why,
34:50
when you mix hypoechoic fat in hypoechoic
34:53
muscle, why does it become echogenic?
34:56
Well, it has to do with the physics of how
34:58
an ultrasound image is formed.
35:00
Remember an ultrasound image,
35:02
we're essentially looking at interfaces or reflections.
35:06
What produces the brightness of the reflection
35:08
is the impedance difference
35:10
across that interface.
35:12
So even though muscle alone is hypoechoic
35:15
and fat alone is hypoechoic,
35:17
when you mix them together like this,
35:20
their impedance differences create reflections
35:22
at every single interface.
35:24
This is why it's brighter.
35:26
It's the same reason why edema or inflammation
35:29
of a muscle becomes echogenic as well.
35:32
So back to fatty infiltration.
35:34
There you go. That's the physics part.
35:37
Extended field of view can help.
35:39
Here we can see the normal teres minor.
35:41
Here we can see the infraspinatus and supraspinatus,
35:45
echogenic, loss of tendon, muscle differentiation.
35:47
Look at the trapezius and deltoid.
35:50
That's why don't compare to those.
35:52
Look at the teres minor.
35:55
Here's the contralateral side.
35:57
Note that this is about twice as large of the teres minor,
36:00
meaning the infraspinatus.
36:02
The tendon-muscle differentiation,
36:04
we can appreciate both the supraspinatus
36:06
and infraspinatus.
36:08
Okay, secondary signs of rotator cuff tears.
36:10
I've already talked about them.
36:12
I'm going to briefly mention them as we continue forward
36:16
on this journey through the rotator cuff.
36:19
So these are the four.
36:21
The first two, cortical irregularity, volume loss.
36:23
The most important.
36:25
I'll mention these other two, as well.
36:28
So we know how important this finding is.
36:31
In fact, when I'm looking at a radiograph
36:33
with an external rotation view,
36:36
if you see cortical irregularity,
36:38
three out of four dentists,
36:39
I mean three out of four patients are going to
36:42
have a rotator cuff tear.
36:42
In my experience, it's closer to 90%.
36:46
So this is a very important finding to say,
36:49
maybe you need an ultrasound or an
36:51
MRI of the cuff. If it is smooth,
36:53
you do not have a cuff tear most of the time.
36:57
96% of the time, there's no cuff tear.
37:00
Remember, tendinosis does not produce
37:02
cortical irregularity.
37:04
So you shouldn't say this is correlating with
37:06
rotator cuff pathology.
37:07
That's incorrect.
37:08
It's specific to a cuff tear.
37:11
Now, again, I'm talking about the supraspinatus
37:13
attachment on the greater tuberosity.
37:18
Now incidentally,
37:18
when we look at the subscapularis,
37:21
I see cortical irregularity,
37:23
probably about 50% of the time it's routinely seen.
37:27
Some of these are vascular channels.
37:30
The point is, when I see it,
37:32
I'm going to slow down and look for a tear.
37:34
But nearly every time, there's no tear.
37:37
So just recognize that I'm specifically talking
37:40
about the supraspinatus footprint.
37:42
Similarly, if you look under the infraspinatus,
37:44
as you know, the bare area,
37:46
will commonly be irregular,
37:48
as a normal variant from vascular channels,
37:52
although we know it can be excessive
37:53
with internal impingement.
37:55
The point is,
37:56
the specificity of the cortical irregularity
38:00
causing related to a cuff tear,
38:02
it's more specific for the supraspinatus.
38:06
So that's number one,
38:07
cortical irregularity, supraspinatus attachment.
38:10
When you're scanning,
38:11
if you see cortical irregularity at that supraspinatus footprint,
38:14
slow down because if there's a tear,
38:16
it's going to be there.
38:18
The second one, volume loss.
38:20
We've talked about this.
38:21
Well, I've talked about it, you've heard about it.
38:23
Here is a full-thickness tear where the loss
38:26
of the superior convexity is now concave.
38:29
Here's a bursal-sided tear.
38:31
Again, concavity.
38:32
This is a thickened bursa over the top,
38:34
filling the gap,
38:36
going beyond the greater tuberosity.
38:38
So we don't see this with tendinosis.
38:41
And you uncommonly see with articular side tears
38:43
because they're just too deep.
38:45
Very important indirect sign.
38:46
Those are the two that are most important.
38:48
Here is a companion case,
38:49
a short-axis view showing the biceps and
38:52
the supraspinatus in short axis.
38:54
And when I start the cine clip,
38:57
what you'll see here is
39:00
the supraspinatus should be located here,
39:02
but rather, it ends there.
39:04
So the first point here is seeing the biceps
39:07
tendon tells me there indeed is an anterior tear.
39:11
If I were just back here,
39:12
I would have missed it.
39:14
So, I want to make sure I'm looking anterior now.
39:16
Note the volume loss and the fluid,
39:18
there's the cartilage interface.
39:19
So we got all the findings of a cuff tear.
39:22
Incidentally, the fluid is tracking over the biceps.
39:27
So, the rotator interval pulley system is torn.
39:33
And this is coursing over the top.
39:35
This person will be prone, say,
39:36
to having biceps tendon,
39:39
subluxation and dynamic imaging,
39:41
and prone to having a subscapularis tear.
39:44
So the coracohumeral ligament is torn.
39:47
This is probably part of the superior
39:49
glenohumeral ligament, which is there.
39:50
But the point is,
39:51
the biceps pulley is involved with this anterior cuff tear.
39:56
Okay. The third or fourth indirect signs,
39:58
the least specific.
39:59
If you have fluid in the joint,
40:02
usually seen first around the biceps tendon
40:04
long head, as you know,
40:05
that connects to the glenohumeral joint in everyone.
40:08
And in the bursa,
40:09
there's a 95% positive predictive value.
40:12
Now, I think that number is actually
40:13
quite a little high,
40:14
and probably someone needs to redo this research
40:17
because a small amount of fluid
40:19
in both is really nonspecific.
40:21
But what I found was when you have significant
40:23
fluid in both, you should think about it.
40:25
But to be honest,
40:26
it's the other indirect signs and the primary
40:28
sign of a cuff tear that we rely on.
40:31
But I'm just including this for completeness' sake.
40:34
And then finally,
40:34
the cartilage interface sign.
40:37
Here, we can see this bright interface,
40:39
brighter than normal,
40:40
because fluid is laying on top of it.
40:42
Now, I want to point out this is an uncommon
40:44
appearance of a rotator cuff tear.
40:46
Most cuff tears occur at the footprints after
40:49
the age of 40.
40:50
If you're younger,
40:51
you have acute injury,
40:52
you could have a more proximal tear like this.
40:55
Of course,
40:56
if you have the less common proximal tear,
40:58
you won't have the cortical irregularity that
41:00
you'd see with an older attrition tear.
41:02
So this would explain why we don't see the
41:04
cortical irregularity.
41:07
And it's limited because it can be subjective.
41:09
But nonetheless,
41:09
I think it's the third most important,
41:12
but not the top two, for sure, indirect signs.
41:16
Okay, infraspinatus and subscapularis.
41:19
It's really the same primary features that we've
41:22
talked about with the supraspinatus,
41:24
hypoechoic and thickened tendinosis,
41:27
often combined with supraspinatus.
41:30
Hypoechoic to a more well-defined
41:32
defect with cortical irregularity.
41:34
Here's the tear of the infraspinatus,
41:37
usually not isolated,
41:38
usually an extension posteriorly of
41:41
a supraspinatus massive tear.
41:44
Subscapularis,
41:45
partial-thickness articular-sided tear.
41:48
Here we can see it involving the articular surface,
41:51
but not going to the bursal surface.
41:53
There is a bursal surface here,
41:55
as I showed in that second image.
41:57
That subacromial deltoid bursa covers
42:00
a fair amount of the subscapularis.
42:03
Wherever you see deltoid,
42:05
the bursa will be present.
42:09
Probably the most common full-thickness tear
42:11
I see in the subscapularis is a focal tear.
42:14
So what do I mean by that?
42:15
First of all, here is the contralateral side.
42:19
We see the multiple tendon bundles of the subscapularis.
42:23
Cephalad is here, inferior there.
42:25
In this case,
42:26
all these tendon bundles are missing
42:28
except for this one.
42:29
This is a full-thickness tear because it goes
42:32
from the articular to bursal surface.
42:33
But is a focal tear,
42:35
meaning it's not the entire width of the tendon.
42:38
So, I've seen some people call this a partial tear.
42:40
I kind of get that.
42:42
But if you're using the criteria
42:43
for the supraspinatus,
42:44
we should be consistent with the remaining
42:47
rotator cuff tears,
42:48
because there is a bursal surface,
42:50
there is an articular surface.
42:52
Therefore this is a full-thickness tear,
42:55
although more focal.
42:58
Here is a full-width full-thickness tear
43:01
with complete retraction.
43:02
Here's the tendon that's pulled off.
43:04
Here's contralateral side.
43:06
If we look in the short axis,
43:08
compared to the contralateral side,
43:10
it's completely missing.
43:12
Here's the subacromial subdeltoid
43:13
bursa coming over the top.
43:15
Again, it covers much of that tendon.
43:19
Okay, finally,
43:20
we're going to wrap up this talk using the topic
43:24
of calcific tendonitis.
43:27
So first of all,
43:28
when I see calcification in a tendon,
43:30
and I'll focus on the rotator cuff,
43:33
I try to put it into two categories:
43:34
a degenerative linear calcification,
43:37
usually in a background of tendinosis,
43:39
or a more globular collection,
43:42
which is when I use the term calcific tendinosis
43:45
or tendonitis.
43:47
Remember that in the early phases,
43:49
it's not inflamed,
43:50
in the resorptive phase, it is.
43:52
If you want to split hairs,
43:53
you could use either term
43:55
depending on the phase,
43:56
or I think most people just use
43:58
them as synonymous terms.
44:00
But these are...
44:01
it's a globular collection.
44:03
And what is interesting is
44:04
the theory of why this occurs.
44:06
It's tendon metaplasia.
44:07
It's not even degenerative.
44:09
It's interesting.
44:10
It's more common in women over the age of 40,
44:13
and people with calcific tendinosis,