Interactive Transcript
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Hello and welcome to Noon Conferences
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hosted by MRI Online.
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In response to the changes happening around the
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world right now in the shutting down of in-person
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events, we have decided to provide free daily
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noon conferences to all radiologists worldwide.
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Today, we're joined by Dr. Stephen J. Pomeranz.
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He is the founder of MRI Online.
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He's authored numerous medical textbooks in MRI,
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including the MRI Total Body Atlas.
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He is an avid conference lecturer.
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Chairs fellowship training programs in a more and advanced imaging
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and he is also the CEO
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and medical director of ProScan Imaging.
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Reminder, there will be time
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at the end of this lecture for a Q&A session.
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Please use the Q&A feature to ask all of your
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questions, and we'll get to as many as we can before
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our time is up. That being said,
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thanks so much for joining us today.
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Dr. Pomeranz, I will let you take it from here.
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Today, we're going to be talking about menisci.
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And my motto is, "Think it. Learn it. Apply it."
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And that's what we're going to do.
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Ashley has given you my faculty disclosures.
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I have nothing else to disclose.
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And we're going to get right to it.
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One of your primary jobs as a radiologist and as a
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musculoskeletal radiologist is to save the whales and
1:11
save the menisci. You need them.
1:13
In years past,
1:14
we indiscriminately resected small tears and
1:17
we're no longer going to go down that lane.
1:21
Let's talk about meniscus physiology and anatomy.
1:24
There is physiologic signal in a meniscus due to
1:27
diffusion from the joint towards the periphery that
1:31
does not communicate or approach the upper
1:33
lower or inner articular surface.
1:35
This is a given.
1:37
A tear is when one of the above is violated.
1:41
In other words, you have a signal that approaches one of these
1:43
surfaces and/or the meniscal shape is altered.
1:48
Here's a side or lateral view of the meniscus.
1:51
Gross specimen and reticulin staining
1:54
showing meniscal vascularity.
1:56
Here's the meniscus as a triangle.
1:58
The outer third of the meniscus,
2:00
particularly in young pediatric individuals,
2:03
is pretty well vascularized, and so tears in this region,
2:07
which are most commonly vertical,
2:09
will heal on their own in the majority of cases.
2:13
The meniscus has some very complex attachments.
2:16
The medial meniscus is less mobile than the lateral
2:19
meniscus. And it's firmly fixed to the joint capsule.
2:23
So, it is more prone to certain types of injuries.
2:26
There is a femoral meniscal attachment that is contiguous.
2:30
Comes in contact with and blends
2:31
with the deep portion of the medial collateral ligament,
2:35
known as the meniscofemoral ligament or MFL.
2:39
A lot on this covers a larger portion of the articular cartilage
2:42
compared with the medial meniscus.
2:44
About 80% vs. 60%,
2:47
although in discoid lateral meniscus, it's 100%.
2:51
The lateral meniscus is more mobile,
2:53
thus its lower propensity to be injured.
2:57
Lateral meniscal fibers do not directly attach
2:59
to the lateral collateral ligament as their
3:01
medial counterparts do attach to the MCL.
3:06
There's some variability in the meniscofemoral ligaments.
3:09
And most common and notable
3:11
is the anterior meniscofemoral ligament of humphrey.
3:15
Then there is the posterior meniscofemoral ligament
3:18
of Wrisberg, either or both of these come off the
3:22
posterior aspect of the lateral meniscus.
3:24
There is a transverse anterior
3:26
intermeniscal ligament of Winslow.
3:29
And there are various names and some
3:31
unnamed oblique intermeniscal ligaments
3:34
like the ligament of Barkow.
3:37
This diagram,
3:37
taken from the work of Stoller,
3:39
drawn by Salvador Beltran.
3:41
A beautiful diagram demonstrates some of these attachments,
3:46
including the anterior intermeniscal ligament
3:49
of Winslow, going from anterior horn to anterior horn.
3:53
And you can tell which side is which because the
3:56
lateral meniscus is more C-shaped,
3:57
the medial meniscus is more banana-shaped.
4:01
Here's the PCL, a posterior cruciate ligament.
4:03
In front, we have the meniscofemoral ligament
4:06
of Humphrey that we alluded to earlier.
4:08
Behind the PCL is the meniscofemoral ligament of Wrisberg,
4:11
and they are inversely proportional to one another
4:14
in terms of size.
4:16
But they both come off in the same general vicinity
4:19
in the posterolateral meniscus horn near the root.
4:24
There are root ligament attachments to the tibia
4:27
and tibial spines, both laterally and medially,
4:30
in the back and in the front.
4:32
And though not drawn,
4:34
there are intermeniscal ligaments
4:36
that may go from the posterior horn of one
4:38
to the anterior horn of the other
4:40
and these can be problematic.
4:41
The inner tip of the meniscus is not anchored.
4:45
It's freely floating like the wings
4:47
of a stingray or manta ray.
4:49
Whereas, the posterior periphery of the meniscus
4:52
is attached to the capsule more tight on the medial
4:56
side than on the lateral side.
5:00
Tearing of the meniscus roots have often been overlooked.
5:03
Only in the last decade have they been
5:05
recognized as an important cause of other pathology.
5:09
Tears of these roots result in untethering of the
5:13
meniscus and some loss of function and
5:15
alter biomechanics and kinematics.
5:18
The posteromedial meniscus root is the one that is most
5:21
associated with injury, and isolated injury at that,
5:26
and with that, the meniscus becomes untethered, begins
5:29
to extrude medially, and the patient ends up
5:31
with advanced osteoarthritis in later age.
5:36
We said that the meniscus is attached peripherally,
5:39
and here is an upper fascicle and a lower fascicle
5:42
of the lateral meniscus posterolateral corner,
5:46
and these are normal. We'll see later on that these can rapture.
5:49
But the inner portion of the meniscus is floppy,
5:52
it's not attached.
5:54
So, it can bend or be moved around
5:56
by synovial tissue and fluid.
5:59
This is known as meniscal flounce
6:01
as it was described by Zarins.
6:03
Some have proposed that people with hypermobile
6:05
meniscus tips are more prone to meniscal tears,
6:10
although that is the subject of debate.
6:12
Here's a patient that has sustained the valgus injury.
6:14
The amseal is torn, there's an impaction
6:16
injury on the lateral side.
6:17
But I'm showing it for the flounce.
6:20
There is some fluid and synovial thickening
6:23
that is bending and moving the meniscus around.
6:26
Bending it like Beckham.
6:27
Here's the sagittal projection again,
6:29
showing this phenomenon of hypermobility of the free
6:32
edge of the meniscus, known as Flounce,
6:35
not to be confused with a blunt-ended tip tear of
6:39
the meniscus, which is a look-alike.
6:41
There are three critical meniscal functions
6:44
and they are critical.
6:46
No more resecting these small, tiny little tears.
6:49
The menisci serves as stabilizers.
6:52
People that lose their menisci say that
6:54
"My knee feels like it's going to give away."
6:56
It reduces axial load hoop stress.
7:00
And it also improves the overall glide
7:03
and flexibility of the knee,
7:05
so that you have a bigger range of motion
7:07
when your meniscus is preserved.
7:11
Three critical rules.
7:14
No knee meniscus is uniformly black. None.
7:18
They all have water in them.
7:19
Most meniscal tears are not symptomatic
7:22
and are non-surgical.
7:24
The younger the individual,
7:26
the more relevant to clinical
7:27
management is the tear.
7:30
Incidental Meniscal Cleavage Tears
7:32
in the body of adults is extremely
7:35
common over age 60.
7:37
More than 50% of individuals will have them,
7:40
and they will be asymptomatic.
7:43
The meniscus is made up of extracellular matrix,
7:46
70% of which is water.
7:48
So you're going to see water in the meniscus.
7:51
They won't be bright like water,
7:53
it will be diffused water, as we'll see in a moment.
7:56
20% will be collagen.
7:59
And then, the remainder outside the extracellular
8:01
matrix are glycoproteins, proteoglycans,
8:04
and non-collagenous proteins.
8:06
So, what are the causes of meniscal signal?
8:09
Well, the most common cause is physiologic,
8:12
micro diffusion and fluid in the meniscus,
8:15
seen here in green.
8:17
Tears, of course.
8:19
Contusions in children and the outer third vascularity.
8:23
So common.
8:24
A tragic mistake is to intervene on a child for this.
8:29
Cyst.
8:30
Intrameniscal Tears.
8:31
Degeneration.
8:34
CPPD and even Gout,
8:35
and Meniscal Ossicles
8:38
So some of you are wondering how you distinguish some
8:40
of these things, and we're going to spend
8:41
some time talking about that.
8:44
But one of the hallmarks of a tear
8:47
is focality and inflammation.
8:50
Let's take a look at some normal meniscal signal.
8:53
If you squint and look very carefully and stare at this
8:56
T1 spin-echo image,
8:58
you can see
9:00
some gray signal intensity in this meniscus,
9:03
corresponding to the diagram,
9:05
showing this yellowish color in the meniscus,
9:08
which fades as you move into the inner third.
9:11
This is normal
9:13
fluid that lives in the meniscus that travels along
9:16
the radial fibers that are found inside the meniscus.
9:20
These are fibrocartilaginous structures that are
9:23
made mostly of collagen, that consist of a superficial thin
9:26
mesh-like layer, a deeper radial layer,
9:29
and a circumferential layer as well.
9:32
And the radial and circumferential layers,
9:34
the diffusion of fluid produces this,
9:36
and I'm going to show you
9:38
an even clearer example of it in a minute.
9:41
So, what to find is this normal meniscal signal,
9:44
which can be somewhat bright
9:46
on heavily water-weighted sequences.
9:49
It's in the outer third.
9:50
It fades as you go to the middle third,
9:53
it may communicate with the capsule,
9:55
but it never goes up and down.
9:56
It never goes to the superior surface.
9:58
It never goes to the inferior surface,
10:01
it is centric.
10:03
It is not as bright as hyaline cartilage.
10:05
It is not bright on the T2-weighted image,
10:08
and again, it doesn't surface
10:10
superiorly or inferiorly, or in the tip.
10:13
It doesn't go in the inner third and come out the tip.
10:16
This outer third area is vascularized
10:19
and is the zone of respect
10:21
where tears have a high likelihood to heal.
10:25
Here's a coronal projection showing you an ill-defined
10:29
area of increased signal intensity.
10:31
It's as if you are in Alice in Wonderland,
10:34
looking through the glass.
10:36
You can see little structures inside.
10:38
These are collagenous bands that are water-laden.
10:40
Here's some more water around them.
10:42
This is all normal.
10:44
It's fuzzy, it's ill-defined, and that surrounding
10:48
tissues are close to a normal.
10:50
The bone's normal. The cartilage is normal.
10:52
The shape of the meniscus is normal.
10:55
All features that help you decide you're
10:57
looking at normal.
10:58
Normal.
10:59
Normal.
11:00
Sagittal water-weighted image,
11:01
the signal slopes gently down.
11:03
It fades in the middle and inner third.
11:05
By the inner third, it's gone.
11:07
It's fuzzy.
11:08
It's not as bright as as hyaline cartilage.
11:10
It is window-framed all the way around the surrounding
11:14
tissues are coal stone normal.
11:16
This is normal
11:18
meniscal signal.
11:21
Contrast that with this.
11:23
Let's go back for a minute.
11:24
Fuzzy
11:25
sharp edge.
11:27
This is somebody who fell in a creek bank.
11:31
It's a tear.
11:32
Why is it a tear?
11:34
What makes it different than the last example?
11:36
First, the patient has pain right there,
11:39
a posteromedial pain.
11:41
Second, you see they had a bone injury.
11:44
So that helps you.
11:46
Third, it's a little bit swollen.
11:49
Fourth, it doesn't fade.
11:51
It's very focal and then comes to a sudden stop
11:54
instead of fading into the middle third.
11:57
It has a little bit of weird complexity to it.
11:59
The capsule is swollen.
12:01
So, this going to be a hidden tear.
12:03
But it is a tear,
12:04
by a virtue of all those features,
12:07
but especially the focality.
12:11
Now, not everything that produces intrameniscal
12:13
signals are tear, you already know that.
12:15
You know meniscal vascularity can do it.
12:17
Here is a scenario
12:18
where there is signal in the outer third.
12:21
Now, most tears that occur at the outer third are vertical.
12:24
This is horizontal signal.
12:26
And I don't mind if you have some signal
12:27
in the outer third.
12:28
But I do mind when the patient is very symptomatic
12:31
there, and they are.
12:32
I do mind when it's inordinately swollen.
12:35
Look at the superficial MCL bursa.
12:38
I do mind when there are erosions right
12:40
nearby in synovial hypertrophy.
12:43
This is a patient that has the MR manifestations,
12:46
horizontal signal that doesn't fade in the inner third,
12:49
comes to an abrupt hole,
12:51
with erosions,
12:52
with inflammation in the entity of CPPD.
12:55
Another cause of intrameniscal signal.
12:59
Here's a 16-year-old who had a football injury.
13:01
This is a meniscal ossicle or ossification
13:05
in the meniscus.
13:06
It was originally thought these are developmental,
13:08
but we now know that the majority of these occur as
13:12
a result of either a hematoma,
13:14
or sometimes a fragment of bone
13:16
may even get trapped in a torn meniscus
13:18
and the meniscus closes over on it.
13:20
So, the majority of these are acquired
13:23
as opposed to developmental in nature.
13:26
So now we come to a real tear.
13:29
Unlike the normal examples you saw,
13:32
this one is not window-framed.
13:34
There is no dark signal along the underbelly of it,
13:37
on the inferior tibial surface.
13:38
It's got these little fingerlets.
13:40
It's sitting on the surface of the tibia.
13:44
There's a little bit of swelling
13:45
in the posteromedial corner.
13:47
This is what we might refer to as an undersurface
13:50
scuff or rolled edge posteromedial meniscus body horn
13:54
junction or corner tear.
13:55
We'll ignore the intraosseous ganglion for now.
13:58
So now, what you can see,
14:00
we're working our way up the scale.
14:02
We've gone from some normal signals to some
14:05
inflammation, to some examples of intrameniscal tear.
14:11
And now, we have a clear-cut communicating tear
14:14
that's a lot bigger than our scuff
14:16
rolled edge undersurface tear.
14:17
That's a flap tear, it's obliquely oriented.
14:21
This one is not displaced in this position.
14:23
Here's a diagram of it.
14:26
This one involves the inner third, middle third,
14:28
and outer third.
14:29
It goes from the body to the posterior horn.
14:31
And in fact, went all the way to the root.
14:34
And it is key when you're looking at these tears to
14:36
evaluate them in thirds.
14:37
Inner third, middle third, outer third.
14:40
Here, the inner third is involved.
14:42
Here, the middle third is involved.
14:43
Here, the outer third is involved.
14:45
And this helps you decide whether a tear is
14:48
surgical or not.
14:49
A large non-displaced flap tear of
14:52
the medial meniscus.
14:52
Let's talk a little bit about technique.
14:55
What do we like?
14:57
On high field, I like proton density fat supression for detection,
15:00
along with the T1.
15:02
I always use a T1.
15:04
And some of the sequences you're familiar with
15:06
are PD FATSAT, PD SPIR, PD SPAIR, PD SPECIAL, and STIR.
15:12
On older high-field systems
15:13
and some low-field systems,
15:14
I like standard gradient echo and steady-state
15:17
free precession, including gradient recalled acquisition
15:20
in steady-state or GRASS,
15:21
true FISP, field echo, and on Hitachi scanners,
15:25
I love the SARGE,
15:27
which is a type of steady-state free precession.
15:30
For three-dimensional very high-resolution imaging
15:34
on newer high-field scanners, I like additive gradient
15:39
echo, which I can perform with one millimeter cuts
15:42
and reconstruct and look at the axial projection.
15:45
These go by the names of MERGE, MEDIC, M-FFE,
15:49
if you're Philips user, and ADAGE if you're a Hitachi user.
15:53
Here is an example of some of these sequences.
15:56
Here's a proton density fat-suppression,
15:59
heavily water-weighted image.
16:00
On an older system,
16:02
here is a gradient echo,
16:03
a GRASS sequence.
16:05
Pretty nice.
16:06
And it shows the meniscus tear
16:08
in a lovely way with a double meniscus sign anteriorly.
16:10
And here's another heavily water-weighted one,
16:13
the 3D 1 mm additive gradient echo or ADAGE
16:17
showing a large root-to-body meniscus tear.
16:20
These are the most favored nation status sequences
16:24
for meniscal detection, along with the T1.
16:27
Which ones do we no like?
16:29
We don't like the spoiled
16:31
gradient echo sequence that is made on
16:33
some of the older general electric scanners
16:36
because it makes the meniscus too grey
16:38
and too bright, and results in an overcall.
16:41
We don't like the T2 because it's under-sensitive.
16:44
It misses most tears that are scarred or have blood.
16:47
So if you rely on this, you will undercall.
16:50
And then, I don't personally like the proton density
16:53
non-fat suppression image because even though it shows
16:56
meniscal pathology well, it hides bone pathology.
17:00
Which I use frequently to decide on the relevance
17:04
and significance of my tears.
17:07
One special sequence that I rarely use is the radial,
17:11
where I am constantly rotating.
17:12
And perpendicular to the meniscus,
17:14
there is a tear right here.
17:16
But I'm showing it for the technique
17:17
rather than the tear itself.
17:20
This is a specialized view known as the radial series.
17:25
So, let's take a look at a tiny little tear.
17:27
Is that real? Is it flounce?
17:29
Is it volume averaging? Is it synovial tissue?
17:32
Oh, it's small.
17:33
Right at the tip of the posteromedial meniscus
17:36
in a 49-year-old man with pain,
17:38
swelling, and stiffness following an injury.
17:40
This is where the high-resolution images come into play.
17:43
In the axial projection, here is your medial meniscus
17:46
banana-shaped.
17:47
Lateral meniscus, C-shaped.
17:49
And right there,
17:50
right there,
17:52
there is your radial tear.
17:53
Let's see if my pen is working today.
17:55
It is. I'm going to draw right over it
17:57
so you can see it.
17:58
And now, I'm going to take it away.
18:00
Radial tears are a type of vertical tear that is
18:03
radially oriented to the arc of the meniscus.
18:05
There it is at low field. No less.
18:09
Let's take a look at the meniscus and
18:12
divide it up into thirds.
18:15
Well, first, when we look at the anterior horn,
18:17
body, and posterior horn, you could divide the meniscus
18:20
up that way into a third,
18:21
a third,
18:22
a third.
18:23
Same thing on the medial side as the lateral side.
18:25
But there's another way to divide it,
18:28
inner third, middle third, and outer third.
18:30
And I use them both.
18:31
And I use both as descriptors.
18:33
So whenever I have a tear,
18:35
I say whether it's in the anterior horn,
18:36
horn body junction, body posterior body horn junction,
18:40
or posterior horn.
18:41
And whether it is in the white-white zone, inner third,
18:44
red-white zone, middle third,
18:45
or red-red zone, outer third.
18:48
The outer third tears are usually vertical with pivot-shifts.
18:51
Living in the middle third, usually buckets.
18:55
Living in the inner third,
18:57
radials, flaps and parrot beaks live here.
19:01
There are three,
19:03
count of three basic tear shapes.
19:05
So don't get too discouraged,
19:07
vertical, horizontal, and complex.
19:09
Vertical, this includes the bucket.
19:13
Yup, that's a type of vertical tear.
19:15
The radial and the longitudinal vertical.
19:18
Horizontal tears.
19:19
These include traumatic and degenerative cleavage tears.
19:23
And then everything else, I lump into the complex.
19:26
Here's not all of them.
19:27
I'm not showing you a horizontal one.
19:29
But here's a few of them.
19:30
Here is the longitudinal vertical tear.
19:33
Parallel is the peripheral axis of the meniscus.
19:37
And here's another vertical tear.
19:39
This one comes from the inside out.
19:41
It's perpendicular to that one,
19:44
radial, vertical longitudinal.
19:47
Both vertical tears.
19:49
Now, if you take a vertical tear and you put it in the
19:52
middle of the meniscus, in the red-white zone, and then
19:56
it starts to widen, you get yourself a bucket-handle tear.
19:59
And here is an example of a flap tear.
20:02
Here is a baby flap tear with complex obliquity,
20:06
found in the anterolateral body horn junction,
20:08
called the parrot beak tear.
20:10
And here's a flap tear that has rotated posteriorly or
20:14
folded posteriorly,
20:15
the so-called folded displaced flap tear.
20:19
This is a very important thing to recognize
20:21
along with the bucket,
20:22
because these are surgical signs.
20:24
Here's a sagittal projection showing you
20:26
several folded flap tears.
20:28
Look at this one.
20:30
Folded backward, ripped off.
20:31
This one folded over on itself.
20:33
This one folded making a meniscal sandwich.
20:36
The folded flap tear,
20:38
usually going from anterior to posterior.
20:40
But it can fold in the opposite direction.
20:45
So, here's a vertical longitudinal tear.
20:46
You've already seen the vertical radial tear.
20:49
And in the vertical longitudinal tear,
20:50
it's usually in the outer third.
20:52
This one happens to be in the middle third.
20:53
It's got slight obliquity to it,
20:56
but you can see the analogy with the diagram
20:59
right here.
21:00
Most of these vertical longitudinal tears that occur
21:03
in the middle or outer third are left alone.
21:06
There's the radial tear.
21:08
Radial tear also vertical,
21:10
but this one going from the inside out.
21:12
We frequently pay attention to its gap,
21:14
how wide is it right there and we'll measure it.
21:16
How deep is it?
21:18
Not how deep is your love,
21:19
how deep is the tear?
21:21
It is said that tears over 8 mm in depth
21:23
should be operated on.
21:26
I am far more conservative than that,
21:28
even though I'm not making that decision.
21:30
Radial tears,
21:31
when they are near full depth,
21:33
usually have to be dealt with.
21:35
But not all the time,
21:36
the 8 mm rule is not hard and fast for depth.
21:39
But here we have the radial tear,
21:41
sagittal projection.
21:42
Normal meniscus.
21:44
Normal meniscus.
21:45
Defect.
21:46
Defect.
21:48
The rest of the meniscus.
21:50
The rest of the meniscus.
21:52
The radial tear seen as a defect
21:54
when you image it on en face.
21:56
If the tear was over here,
21:58
then you would see it in the coronal projection
22:00
as a defect.
22:02
A horizontal tear,
22:03
that one's easy,
22:04
self-explanatory.
22:06
Over 50% to 60% of all people over age 60 have this.
22:10
A horizontal cleavage tear of the
22:12
lateral meniscus body.
22:14
You don't operate on these.
22:16
They are so common.
22:17
They are frequently associated with osteoarthritis
22:20
and degenerative joint disease.
22:22
But sometimes, they can exist all by themselves
22:25
and still be asymptomatic.
22:28
Here's a radial tear.
22:29
But instead of being a small defect,
22:31
now you can analyze its shape.
22:33
It looks like a crab.
22:35
It's a complex radial tear.
22:37
So from walking on it,
22:39
it's getting mashed.
22:40
Here it is getting mashed.
22:42
So, complex radial would do very well on this one cut.
22:46
It's only in the inner third.
22:47
But on this next cut,
22:48
it's in the inner, middle, and outer third.
22:51
He's a 41-year-old man.
22:52
He's been symptomatic for some time with this tear.
22:55
And it's going to have to be, unfortunately, resected.
22:58
Which usually results in arthritis within six months,
23:01
but you have no choice.
23:03
Here's a complex tear.
23:06
Complex is easy.
23:07
It's anything that you can't simply
23:09
define as horizontal, vertical, or flap-like.
23:13
There, and even flap tears are considered complex.
23:16
But this one goes in many different directions.
23:18
It goes horizontal.
23:19
It goes vertical.
23:20
It goes up. It goes down.
23:22
And because of its size,
23:25
it has contributed to instability of the knee,
23:30
and eventually, that meniscus has pulled away
23:32
from its attachment posteromedially,
23:34
and we're starting to develop meniscal capsular detachment
23:37
from this complex tear.
23:40
Here's another type of complex tear.
23:42
This is a baby flap tear.
23:45
It's got a complex obliquity.
23:47
Let me see if I can draw it for you.
23:49
Here's a meniscus right here.
23:50
Let's see if I can make it 3D.
23:53
Here we go.
23:54
And this tear looks like the snout of a bird.
23:57
It can go this way.
23:58
It can go this way.
24:00
Not only is it curved,
24:01
when you look at it from the top as you dive into
24:03
the meniscus, it also has a curvature, as well.
24:06
Now when you image it,
24:07
you're going to see it, with successive cuts,
24:10
you're gonna see it march towards the
24:13
inside of the meniscus.
24:15
The so-called meniscal marching sign.
24:17
So, let's take a look.
24:18
There is a meniscus.
24:19
It's marching inward,
24:21
it's marching inward,
24:23
it's gone.
24:25
So when you see that, you know that your
24:26
tear has an obliquity to it.
24:30
These are thin tears that,
24:31
like the anterolateral body horn junction,
24:34
they're curved in multiple projections.
24:36
They look like the snout of a bird.
24:38
It's the parrot beak tear.
24:39
Here's another one.
24:41
This one perhaps doesn't show the
24:42
curves as well as I would like,
24:43
but it is in the typical anterolateral body horn junction.
24:46
There it is right there.
24:47
It looks just like a radial tear.
24:49
The axial projection,
24:50
you can see how it tapers.
24:51
Just like the snout of a parrot.
24:53
There it is right there.
24:55
Ooh, that's pretty.
24:56
Maybe a little more curve would
24:57
be nice, but I think you get the picture.
25:00
Meniscal Chronicity.
25:03
Unfortunately, as we age,
25:06
we get a little dehydrated.
25:08
Why do you think the salesperson
25:09
shows you pediatric MRI
25:11
when they're trying to sell you a scanner?
25:12
Because kids have more water.
25:14
The pictures are prettier.
25:16
Because you're measuring the amount
25:18
of protons in the body
25:19
when you make an MRI image.
25:21
When you're older, you dry out, and when you dry out,
25:24
things start to crack.
25:26
This is bad news.
25:27
And as they start to crack, they cleave.
25:30
This is very common for menisci.
25:33
And over time, the meniscus may macerate.
25:35
So, you're not going to go in and resect this.
25:38
The patient needs a joint replacement.
25:41
So, doesn't so much matter what you say as long
25:44
as you understand what you're doing,
25:46
that you don't force an unnecessary procedure.
25:49
There's...
25:49
Oh, wait.
25:50
We will describe it as degenerative joint disease.
25:53
We will Kellgren Lawrence grade it.
25:56
You can google this and learn the Kellgren Lawrence
25:58
grading system, which I urge all you young
26:01
radiologists to do since it's an important plain film
26:04
grading system and I apply it to MRI.
26:07
I usually describe menisci like this
26:09
as medial compartment failure
26:11
when they have OA, penetrating erosions,
26:14
no cartilage replaced by synovium,
26:17
and a macerated meniscus that is extruded medially.
26:20
So, my conclusion will read medial compartment failure
26:24
with failed medial meniscus
26:25
and extensive diffused chondromalacia,
26:29
with grade 3-4 delamination.
26:31
Meniscal Cysts.
26:33
These are actually pretty common.
26:36
The ones on the lateral side are smaller,
26:40
they are more anterior,
26:41
and they're more often painful.
26:44
The ones on the medial side
26:46
are more often posterior.
26:48
They are more often giant,
26:49
and they're more often painless.
26:51
This one happens to be small.
26:54
It's a child with open growth plates.
26:57
This case illustrates what I have
26:58
referred to over the years
27:00
as the meniscal arrow sign.
27:02
Those of you that understand the sport of wrestling,
27:04
especially our friends from Russia and
27:07
Iran where wrestling is a huge sport,
27:09
there's a lot of flexion of the leg that takes place.
27:12
So, there's a lot of what I call compressive axial load tears.
27:15
The meniscus develops
27:17
what I call a traumatic split.
27:19
And with that split, the diffusion event that
27:22
normally takes place becomes accelerated.
27:25
And that diffused synovial fluid gets loculated as a
27:30
small, peripheral, parameniscal cyst that comes
27:33
right smack dab out of the center.
27:37
The so-called meniscal arrow sign.
27:39
Right out of the tip of the arrow comes the tear,
27:42
and right at the tip is your small ball-like meniscal cyst.
27:48
Contrast that with this patient,
27:50
an adult, growth plates closed.
27:52
Now fifty years of age.
27:54
I call this the under-over sign.
27:57
Our tear comes right out of the center of the meniscus,
27:59
but not this lesion.
28:00
It comes from underneath the meniscus.
28:03
It's got pressure.
28:05
It's moving structures out of the way.
28:08
There's not a lot of joint fluid,
28:09
which makes a capsular synovial cyst unlikely.
28:12
There's no synovium.
28:14
It's loculated.
28:15
It's a ganglion pseudocyst.
28:19
Let's talk about meniscal instability.
28:25
Here are some signs that, taken together,
28:28
support the diagnosis of meniscal instability.
28:32
Each one by itself not necessarily, although
28:35
some are more important than others.
28:38
But here are the things I look at
28:39
to decide how aggressive
28:41
I'm going to be in my dictation:
28:43
length greater than 45 cm,
28:45
complex shape,
28:47
diminished volume or height,
28:50
displacement, extrusion, fragmentation,
28:54
folding like you saw earlier.
28:56
Inflammation,
28:58
swelling of the capsule,
28:59
swelling of the tear,
29:02
associated ligamentous laxity
29:04
makes smaller tears more relevant.
29:07
Is it trizonal?
29:08
Outer third, middle third, inner third.
29:11
Radial depth, as we said earlier.
29:12
Greater than 8 mm.
29:14
Is it gapped or widened?
29:17
Here's an example of an unstable tear
29:20
that has to be dealt with surgically.
29:23
The sign known as the comma sign.
29:25
The meniscus is extruding out and down.
29:28
There's your comma right,
29:29
there with a large complex flap tear
29:32
that is traveling with the meniscus as it should,
29:35
and associated inflammation.
29:38
So if you have a comma sign,
29:40
then you also have an apostrophe sign.
29:43
We look at this coronal water-weighted image
29:45
and we say, "Well, where's the meniscus?"
29:47
It's too small.
29:48
The most common cause of a small meniscus
29:50
is meniscectomy, but they've had no surgery.
29:54
Another common cause is inflammatory
29:57
autodigestion, as in, RRA.
29:59
Neither one exists here.
30:01
The meniscus has gone fishing out into the
30:04
parafemoral gutter as the meniscal apostrophe sign.
30:08
Another example of an unstable meniscus tear.
30:13
So, all of those features can be used to help you
30:17
make intelligent, cogent, thoughtful decisions about
30:22
how to word and discuss the case with your clinician.
30:25
Your job is to make the clinician look good.
30:28
What are the factors that determine
30:29
surgery besides those?
30:31
Patient Age.
30:32
Much more likely to operate on somebody 25 than 65.
30:36
Patient activity level.
30:38
Kind of sport are they doing.
30:40
Other symptoms on the same side as the tear.
30:44
It won't operate on a medial tear
30:45
when the symptoms are lateral.
30:47
They have locking.
30:48
Are there cysts?
30:50
Are there signs of instability
30:52
like we described in the prior slide?
30:55
One of the most important that you just simply
30:58
cannot miss, is a bucket handle tear in a youth,
31:03
and associated ligamentous pathology
31:06
Here's an example of a tear
31:07
in a young person that we would operate on.
31:09
Goes all the way from the root into the horn body junction.
31:14
It's thick.
31:15
There is extensive inflammation.
31:18
And on the sagittal T1,
31:20
it is complex and it is the locus
31:23
where the patient's symptoms are.
31:24
So cleaning this up
31:26
with a trimming and a sowing of the middle and outer third
31:29
is totally appropriate.
31:31
And you've already seen an example of a meniscus cyst
31:34
previously, so we're not going to talk about that again.
31:37
But here is an example of a patient with a small tear.
31:42
The posteromedial corner, right there, is swollen.
31:45
There's some horizontal signal in the meniscus
31:47
that's not that impressive.
31:49
As you go to the coronal adage,
31:51
which is a 3D 1.2 mm slice thickness,
31:55
and you see the signal,
31:57
and you say,