0:00

Okay, now we're going to talk about

0:02

acetabular or impingement or CAM type

0:06

impingement, and labral injuries.

0:08

For that, I think it's very instructive

0:10

to take a look at the hemipelvis

0:13

and the associated femoral head.

0:15

Here's the femoral head

0:17

going into the acetabulum.

0:20

So if I'm going to, I'm going

0:21

to turn it just a little bit.

0:22

So where does impingement occur?

0:24

It occurs anteriorly on the neck and occurs

0:30

superiorly on the neck, and anywhere between

0:33

here and here is where impingement happens.

0:38

So I'm going to take the pelvis away

0:41

and show you just the femoral head.

0:44

So anything from the superior border

0:46

to the anterior border, so superior

0:49

we're going to call 12 o'clock,

0:51

anterior we're going to call 3 o'clock.

0:53

So in the 12 o'clock to the 3 o'clock position,

0:56

if there's any bump, any deformity

0:59

here, that's what's going to cause

1:01

our impingement, as the femur goes

1:04

this way, and the femur goes this way.

1:07

Okay?

1:08

I think with that little preamble, we can

1:10

start looking at images, and it'll make

1:13

sense why we get the images that we do.

1:16

Okay, here now we're back at the

1:17

computer, where I'm showing you a

1:19

cartoon diagram of that hemipelvis.

1:22

Let's just orient you a little bit over here.

1:24

We have anterior on this side,

1:29

posterior on this side, right?

1:31

This is superior.

1:33

This is inferior.

1:35

The black hole here is the obturator ring.

1:39

And this stuff you're seeing over here, of

1:41

course, is your acetabulum, your bony acetabulum.

1:46

Up here at the 12 o'clock position is

1:48

where we showed you to be the superior

1:50

location of the femoral neck where it would

1:52

impinge if there was anything abnormal.

1:54

And 3 o'clock is at the anterior position

1:58

of the femoral neck if anything were

2:00

to be abnormal and impinged.

2:02

So we're concentrating

2:03

basically on this quadrant.

2:07

That's why we say when we look for

2:09

impingement, we're looking at the 12

2:11

o'clock to the 3 o'clock positions.

2:14

That's the only parts that really matter to us.

2:17

So with that, let me show

2:18

you another PowerPoint slide.

2:21

We are now showing you a slightly

2:23

oblique view of the pelvis.

2:25

Again, I'm going to try to draw

2:28

for you what I'm talking about.

2:31

Here is the acetabulum.

2:34

This is anterior and this is posterior, which

2:40

means that around here is our 3 o'clock position

2:46

and around here is our 12 o'clock position.

2:51

What we're going to do in MRI is we're

2:54

going to pretend that we can slice

2:57

this femoral neck in this fashion.

3:01

When we do that, we're going to look

3:03

down the barrel of that femoral neck.

3:07

So this femoral neck, when we make a

3:09

slice like this, what is it going to do?

3:12

It's going to create an image of

3:14

the neck that's relatively circular.

3:18

Okay, so up here is going to be the 12

3:20

o'clock position of that femoral neck,

3:22

corresponding to this area right here, and

3:26

this is going to be our 3 o'clock position

3:30

corresponding to this area over here.

3:33

So if we see any abnormalities in contour

3:36

from here to here, like a bump, for example,

3:40

that means that area is going to get

3:42

impinged in the acetabulum from here to here.

3:47

I think that makes sense as a preamble, okay?

3:50

And now let's take a look at the MR images.

3:53

And see what that looks like.

3:55

This is our radial image that we just drew.

3:59

Okay?

3:59

So this is the result of us taking

4:03

that femoral neck and slicing it right

4:05

through there, perpendicular to the

4:06

long axis of the femoral neck and

4:08

generates an image that looks like this.

4:11

Okay?

4:12

So this is our 12 o'clock position up here

4:15

and this is our 3 o'clock position up here.

4:17

So 3 o'clock is anterior,

4:19

12 o'clock is superior.

4:21

Okay?

4:22

And what we're going to do is we're going to

4:24

generate radial images that go too too too too

4:26

too too too too too too too too too too too.

4:27

Just like this, okay.

4:28

So let me show you on this image

4:31

right here, what we're talking about.

4:32

So you can follow along, and

4:34

you can see a little yellow line

4:36

here that tells you where I am.

4:37

I'm going to go right to the

4:38

12 o'clock position first.

4:40

So this is the 12 o'clock position, right

4:42

here, and this is the image that's generated.

4:44

If we go two slices this way, that's the one

4:47

o'clock position of the femoral head. That's

4:50

the two o'clock position of the femoral head.

4:52

And finally, this is the three

4:54

o'clock position of the femoral head.

4:56

So we have to evaluate the femoral

4:58

head-neck junction in all those, all

5:00

those positions because, like I said,

5:03

impingement can happen anywhere along

5:05

the superior to the anterior margin.

5:08

So let's go ahead and see what

5:09

kind of measurements we make.

5:10

Let's go back to our 12 o'clock

5:12

position, which is this right here.

5:15

This is superior.

5:16

We can tell because here is the iliac wing.

5:18

Here's the greater trochanter.

5:20

And let's go ahead and make our circles.

5:23

So what we're going to do now is draw a circle,

5:25

a perfect circle, outlining the femoral head.

5:31

So now we're going to draw our alpha angle.

5:35

For that, we need to choose

5:37

our Cobb angle measurement.

5:39

We're going to go from the center of

5:40

that circle, bisect our femoral neck.

5:45

And the second angle we draw is going to be

5:48

where that femoral head or projected femoral

5:51

head transitions into becoming the neck.

5:54

It's going to be somewhere around here.

5:56

So let's go ahead and draw that line.

6:00

So that gives us an angle of about 47 degrees.

6:04

So that's normal.

6:05

Basically, anything less

6:06

than 55 degrees is normal.

6:08

But check that with your local

6:10

orthopedic surgeon because everybody

6:12

has slightly different measurements.

6:14

At our institution, it can range between 55 and

6:17

60 degrees and also on the clinical symptoms.

6:19

So at the 12 o'clock position,

6:22

we have a normal alpha angle.

6:24

Let's take that same measurement

6:25

at the 1 o'clock position, which

6:27

is, again, you see it's over here.

6:29

This is our 1 o'clock position.

6:32

We're going to go through the

6:33

same process of drawing our circle

6:35

to best fit that femoral head.

6:39

You have to be a little meticulous about this.

6:41

And so I think the line is going to

6:44

be like, I'm just going to draw a

6:45

little shadow line with the cursor.

6:49

It's going to go somewhere probably along

6:53

this way, but let's go ahead and make

6:54

the measurements and see how it looks.

6:56

So again, bisecting the femoral neck

6:59

and then where the neck and head meet,

7:03

which is probably around there, and that

7:05

gives me an angle of about 48 degrees.

7:08

Difficult to read, but it says 48 degrees.

7:10

That also is normal.

7:11

Okay?

7:12

So now let's go to the 2 o'clock position.

7:18

The head-neck junction is not quite right.

7:21

Here, let me show you the previous image.

7:23

See how nice and beautiful?

7:24

There's a little, little sculpted out area.

7:28

In our 3 o'clock position, 2 o'clock position,

7:31

you don't see that little indentation, do you?

7:33

All you see is a little lump right here.

7:35

So I have an idea that this is probably

7:37

going to be abnormal, but let's go through

7:39

the motions of actually drawing our curve.

7:43

And we have a best fit.

7:45

Here, maybe just a little bigger.

7:48

Like that.

7:48

I think everybody will agree that

7:51

that is being pretty generous and

7:54

fair as far as our best fit circle.

7:57

So at this point, I would say the head-neck

7:59

junction is probably somewhere over here.

8:02

It's probably somewhere over here.

8:03

So let's see what that angle

8:04

actually turns out to be.

8:05

And actually, I'm being a little

8:06

too generous with this circle.

8:08

I'm going to move this back a little bit.

8:09

Maybe something like that.

8:11

Okay.

8:11

Because I can, you don't

8:12

want to see any cartilage.

8:13

You want to have nice cortex all around.

8:16

So, let's go ahead and draw our

8:17

lines, again, bisecting that

8:21

femoral neck, something like this.

8:24

And our second line is going to be along that

8:27

neck, and it's probably somewhere over here.

8:29

And that comes out to be about 61,

8:34

62 degrees, so we know that's abnormal.

8:36

Okay?

8:37

So, now let's look at the final position at

8:39

3 o'clock, right over here, corresponding to this.

8:42

And 3 o'clock, we said,

8:43

is the anterior position.

8:45

And that makes sense.

8:47

Let's go ahead and draw our circle.

8:54

That looks about right.

8:55

So let's go ahead and draw our angles as before.

8:58

Bisecting the femoral neck.

9:02

And head neck junction is

9:04

probably right about there.

9:06

And that ends up being also 61 degrees.

9:09

So, what can we conclude?

9:10

We can conclude that there is an abnormal bump

9:14

at the head neck junction from the two o'clock

9:17

position to the three o'clock position.

9:20

So when they go in and do the surgery,

9:22

this is the part of the femoral neck

9:24

that they'll have to go and carve out to

9:27

relieve the impingement-type syndrome.

9:29

What has that impingement caused?

9:31

So let's take a look at that.

9:33

And that's going to take

9:33

just a few seconds here.

9:35

I'm going to go back to my, um, one-on-one view.

9:38

And this time I'm going to bring in just a

9:43

Axial image, and if we go through that very

9:46

carefully, we can see, in fact, anteriorly,

9:50

there is an area of high signal, and this

9:52

patient has had an orthogram indicating

9:55

a labral tear at the anterior position.

9:58

And that makes sense because that's also

10:00

where we have the contour abnormality

10:02

between the head and neck junction.