0:00

So next case that we had a 30 year old male complaining of hip pain since

0:05

falling down a slope, while carrying a refrigerator,

0:08

at which time he heard a pop. So the uh,

0:11

main findings in this case was, uh, subc, chondral, uh,

0:15

signal abnormality in the intra superior femoral head.

0:17

We can see there is like this scent and then there's flattening of the

0:22

articular surface. This is AGRE image.

0:27

I'm waiting for the, the T two fat set images to come.

0:29

The coronal T two fat set images.

0:32

We can go back to this axial proton density.

0:37

And what we can see there is a lot of reactive marrow edema,

0:40

reactive joint effusion.

0:41

And the main abnormality seems to be this subc chondral

0:46

geographic area. We have this ous, uh, linear, uh,

0:51

high point and signal and with, um,

0:54

a bright signal in the subc chondral region. So this will be your, uh,

0:58

subc chondral fracture. And this, uh, ous line suggests avascular necrosis.

1:02

There is because of, uh, like a prominent, uh,

1:06

subc chondral fracture, there is articular surface his collapse.

1:10

So these are changes of avascular necrosis.

1:12

The changes are acute and that's why we have reactive mar edema and then a

1:17

reactive joint effusion. So, uh,

1:20

until the images are loading completely. Let's, um,

1:24

review some points about avascular necrosis.

1:27

So early detection of avascular necrosis is important.

1:30

All treatments are geared towards preservation of the femoral head.

1:34

And this is more successful when we do this early in the course of the disease

1:39

and of all imaging tests,

1:40

MR is the most sensitive means to diagnose av and because, uh,

1:44

it picks up the earliest mar edema, like it,

1:46

it takes time for it to show up on CT x-ray, and mr,

1:50

and probably bone scan 'cause the two things.

1:53

But bone scan will have a lower resolution.

1:55

These are the two imaging modalities, but Mr would be the most sensitive of all.

2:00

So what are your classic imaging features? That on T one weighted images,

2:03

we see a crescentic, uh,

2:04

band of low signal intensity in the superior portion of the femoral head

2:09

bone marrow.

2:11

And this band is thought to represent the reactive interface between the

2:15

necrotic bone and the reparative, uh,

2:17

zones that typically extend to the subc chondral plate.

2:20

And on T two weighted images,

2:22

you get this classic double line sign where you have this high signal,

2:26

um, uh,

2:28

linear high signal along the inner side and a low signal on the outer side.

2:33

So that's your double line sign.

2:34

So the high signal is from granulation tissue and the low signal is from the

2:38

necrotic bone. So, uh,

2:42

currently the value of MR is more for, uh,

2:45

diagnosis and also the helps and prognosis by giving the size and location of

2:49

the lesions. So like small size, uh,

2:52

lesions that are more in the medial superior portion, they, uh,

2:57

tend not to collapse.

2:59

So they can be amenable to conservative treatment and avian that does not extend

3:03

to the subc chondral margin also has good prognosis regardless of the size of

3:07

the lesion.

3:08

But if you have bigger lesion that ex with articular of his involvement,

3:12

like that extent all the way to the subc chondral bone, um,

3:15

they are more likely to collapse.

3:17

And we need to do core decompression at an earlier stage for these patients. So,

3:22

and then there was, um,

3:23

one study that showed that 74% of femoral hit collapse was seen in

3:28

the region of avian and MR involved poor than two thirds of the weight bearing.

3:32

So if more the weight bearing surface areas involved higher chances of

3:36

femoral head collapse,

3:38

there's also a classification on MR that's based on the signal intensity of this

3:43

dead ma like the, the, the infarcted bone,

3:47

how it looks on T one and T two weight images. It can have fat,

3:50

it can have blood, it can have fluid, or it can have fibrosis.

3:54

It actually shows the evolution of changes in avascular necrosis and just

3:59

suggests the timeline of, or tells you about the acuity of the, the problem.

4:04

And there is this more detailed classification and we know that, look, you know,

4:08

we do this classification too where like, uh, stage zero is, uh,

4:13

everything is normal. Stage one is when your MR is showing mar edema.

4:18

Stage two is you have changes of AV N but there is no crescent sign.

4:22

Stage three is when you have a crescent sign.

4:24

Late three is when you have collapse, and four is when you have osteoarthritis.

4:28

So that's the basic grading. So when you have an MR of avascular necrosis,

4:32

let's see if all our images are here. Not yet. So when you have an mr, uh,

4:37

first of all,

4:37

we need to make the diagnosis and that's pretty easy when you have this

4:40

geographic area of, uh, yeah,

4:44

I was saying when you have the subc chondral geographic area of altered mirow

4:47

signal intensity, you know, it's avascular necrosis. So once we have that,

4:51

the other things that we need to do on MR imaging to give the approximate, um,

4:56

area of how much of the femoral head articular surface it's involving, it, it's,

5:00

it's, uh, nothing objective. It's more subjective where you tell, okay,

5:04

I think it's, it's 30 to 40% of the femoral head that's involved.

5:08

And then you'll do the same thing on coronal images. Then, uh, we tell,

5:12

uh, if there is a subc chondral fracture,

5:15

like it's there in this case we see this nice fluid signal in the subc chondral,

5:20

uh, right underneath the articular cortex.

5:23

And then there is associated articular surface collapse.

5:25

So these are your pertinent positive findings that we need to mention with this

5:29

case. And if there is, uh, any secondary osteoarthritis in the joint or not.

5:34

So here the articular cartilage looks pretty decent, so, uh,

5:38

it's probably your stage three. Yeah. So, uh,

5:43

first to make a diagnosis of avascular necrosis when we have these, um,

5:47

geographic area of subc chondral marrow signal abnormality,

5:50

and the other things that we need to tell how much area of the articular surface

5:54

of the femoral head is involved,

5:56

if there is any articular surface collapse and if there are secondary

5:59

osteoarthritic changes.

6:01

So that completes the report on cases of avascular necrosis. Okay.

6:05

Any questions on this one?

6:07

Um, you said just a subjective assessment of the percentage of the mm-Hmm.

6:11

White brain surface involved. So are you,

6:13

are you just looking at the sort of upper half of the

6:19

sphere of the federal head? No, no. You're looking at that.

6:22

What whatcha you looking at?

6:23

No, you're looking at the entire article surface, like starting from here.

6:27

I'll just trace it all the way till here. So from here to here,

6:30

if you think it's a hundred percent how much of this area is in what?

6:33

So I would say it's, it's predominant pro, probably around 40%.

6:37

But you do that assessment,

6:38

like when you're scrolling that entire stack from anterior to posterior,

6:42

and then you'll also do it on sagittal.

6:44

We cannot like ignore the sagittal because in fact maybe,

6:46

maybe smaller on coronal, but it is more wider on the sagittal images.

6:49

So that increases the area. And then, then the main thing is, again,

6:53

don't have to be very accurate.

6:54

All they wanna know is if it's less than 50% or more than 50%.