0:00

This third vignette gets a little more

0:02

sophisticated and advanced as we show you

0:06

a non-arthrogram MRI and an arthrogram MRI

0:12

using a sequence that is oft not employed.

0:16

The simple proton density

0:19

long TR short TE sequence.

0:23

When might you employ this sequence?

0:26

Anytime you're interested in the status

0:29

of a fibrocartilaginous structure.

0:32

It's also a pretty good sequence to look at

0:35

hyaline cartilage even without fat suppression.

0:38

Neither one of these images is fat suppressed.

0:43

It has very robust signal to noise.

0:47

And for this reason and other contrast

0:49

properties, it brings forth the

0:52

signal in menisci and fibrocartilage

0:55

structures, and it also brings forth

0:58

signal around those structures as well.

1:01

Or immediately around them.

1:03

So it happens to be a little-used, but

1:06

excellent sequence for quote-unquote menisci.

1:11

Now in the sagittal projection, 20

1:14

percent of the time, this will be the only

1:18

sequence that you will see labral tears.

1:21

Now some of you non-believers out there, as

1:24

we scroll through this, the sagittal sequence

1:27

does an excellent job of showing you the

1:30

anterior iliofemoral ligament and the Y-shaped

1:33

ligament of Bigelow, which is discussed.

1:36

In the anatomic section of this series,

1:40

but that's not really why we're here.

1:42

We're usually here to find

1:44

labral pathology, aren't we?

1:46

And to see the status of hyaline cartilage.

1:49

Now don't confuse this normal defect,

1:51

this stellate crease, for a true

1:54

defect because it's well corticated.

1:57

It's not edematous.

1:58

It's smooth.

1:59

It's a normal variant.

2:00

But let's look at the labrum.

2:03

Now, some of you are looking at this and

2:04

saying, Well, I don't really see much.

2:06

But you know what?

2:07

There's very little room for

2:10

irregularity in the sagittal projection.

2:12

In other words, I give the sagittal

2:15

labral shape and signal no quarter.

2:19

In other words, I don't want to see any

2:21

communicating signal on the surface,

2:24

no matter how small, on the anterior

2:26

surface, or on the posterior surface.

2:28

And I do.

2:30

Right here.

2:32

Now you might say, I would never

2:33

read those little fissures and slits.

2:35

You know what, I wouldn't either.

2:39

But I already have another series that

2:41

shows the labral tear very concretely.

2:44

But here's a neat little pearl.

2:47

On a T1-weighted image, if there was a fluid

2:49

collection, it would have a very similar

2:52

signal to the muscle, and you wouldn't see it.

2:57

But if there was a little bit of blood,

2:59

or a little bit of proteinaceous fluid,

3:01

or a little paralabral cyst next to the

3:04

labrum, I think all of you would say,

3:06

there's a labral tear there, right?

3:08

And you know what?

3:09

There is.

3:11

Do you see it?

3:12

It's right there.

3:16

That is a tiny paralabral cyst coming

3:19

out of your ill-defined labral tear that

3:22

was better seen in other projections.

3:25

You might say, well, wow, would you feel

3:28

confident enough not to inject the joint

3:31

with that combination of pathologies?

3:34

Yeah, I would.

3:35

But I also had a coronal T1-weighted image

3:38

that showed the tear in its entirety.

3:42

But still, the presence of that paralabral

3:44

cyst with those signals, with a lot

3:46

of experience, that's a labral tear.

3:50

Now the sagittal projection, using PD

3:53

can be used for other purposes, but there

3:55

are other sequences that are better.

3:57

It is beautiful when it comes to anatomy.

3:59

Look at that transverse ligament

4:02

that has been likened to a St.

4:04

Andrew's cross.

4:05

It's beautiful.

4:06

Look at those hamstrings back there.

4:08

Well, we don't see them so well.

4:09

Let's go to the right.

4:10

You see the hamstrings really

4:12

beautifully on the right-hand side.

4:14

And now let's go to the arthrogram image.

4:16

Yes, in this specific case, the arthrogram

4:19

image shows the labral tear and the

4:22

sagittal projection more optimally.

4:24

There's no question about it.

4:26

And how often does that happen?

4:28

In our experience, and we've got a lot of

4:30

it, less than 10 to 20 percent of the time.

4:33

The non-contrast image in

4:35

expert hands shows it better.

4:37

It shows the indirect signs of tear.

4:39

Like this tiny little paralabral pseudocyst.

4:43

Swelling, inflammation, subtle erosions,

4:46

which can sometimes be hidden by the contrast.

4:50

This is another PD, long TR, short TE image.

4:55

Excellent contrast properties for the labra, for

4:59

the hyaline cartilage, and for the contrast,

5:01

it has been placed into the joint, showing you

5:04

more optimally that tear that you wondered might

5:08

be present, was able to intuit from the indirect

5:13

sign, but here you actually see the tear.

5:15

Let's blow it up a little bigger

5:17

to really drive home the point.

5:18

There's your tear, through and through.

5:23

So the sagittal projection, invaluable

5:26

in assessing labral pathology.

5:28

Somewhere between 1 out of 10 and 1 out of 5

5:32

labral tears only shows up in this projection.

5:34

We allow quite a bit of variability in the

5:38

signal intensity and the shape of coronal labrum

5:43

in the coronal projection, especially in adults.

5:47

But we have very little wiggle room and

5:50

allow very little variability in the

5:52

sagittal projection where we want the

5:54

labrum to be smooth, dark and triangular.

5:59

Let's move on, shall we?