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Menisci, Dr. Stephen J. Pomeranz (11-20-20)

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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.

0:47

And my motto is, "Think it. Learn it. Apply it."

0:53

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.

1:00

And we're going to get right to it.

1:03

One of your primary jobs as a radiologist and as a

1:07

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,