0:00

Okay, so now that we're talking about the deep part

0:03

of the iliotibial band, we can now introduce the concept

0:07

of the Kaplan fiber system.

0:09

And these are, uh, basically collagen fibers

0:13

that run in two directions.

0:14

You have a transverse bundle,

0:16

more along the distal femoral shaft attaching, uh,

0:19

to the postal lateral aspect of the femur.

0:22

And then you have longitudinal

0:23

or vertical fibers extending to the supracondylar ridge

0:27

of the distal femur.

0:31

Now, the biomechanical importance

0:33

of the Kaplan fiber system has been studied,

0:35

and here I list the tensile strengths of both those proximal

0:38

or horizontal bands and those distal and vertical bands.

0:41

And if you do the math, this is about 15 pounds

0:44

and about 40 pounds of, uh,

0:46

tensile strength within those respective components

0:49

of the captain fiber system.

0:51

And these have been found to support the ileal tibial band

0:55

and rotary stability of the knee.

0:59

This is nice, uh, picture,

1:00

I believe this is also from a Labra article.

1:03

And, uh, Dr. Rustic has mentioned several Lara articles at

1:05

this point showing the architecture

1:09

of the Kaplan fiber system, again, proximal

1:12

and horizontal fibers, and then your distal

1:14

and vertical fibers.

1:16

And here they've also drawn the superior lateral gen artery.

1:19

These genant vessels actually are going to play a role over

1:23

and over again when you're trying to identify structures

1:27

of the posterolateral knee.

1:29

So if you can find these structures,

1:30

you can often find components of the Kaplan fiber system.

1:35

So how confident are we identifying these

1:38

Kaplan fibers on MRI?

1:41

Uh, well, uh, one study from American Journal

1:44

of Sports Medicine 2019 found

1:45

that they could identify it mostly on sagal images

1:49

and axial images, but were less confident on coronal images.

1:53

But this other study in, uh, 2020, just a year later,

1:57

using 3D sequences,

1:59

so those are your high resolution isotropic sequences,

2:02

could fi, could visualize the Kaplan fiber system in a

2:05

hundred percent of needs.

2:07

And they found that the coronal in the

2:09

this case was most accurate.

2:12

So can you really see these?

2:13

Yes, I think you can see these even on routine sequences.

2:16

You don't necessarily need high resolution 3D isotropic

2:20

sequences, but again, if you can identify

2:23

the lateral superior lateral ululate vessels.

2:26

And here in red I've marked the artery.

2:28

But as you know, these often traveled with a pair of veins.

2:31

So this is the, the vascular bundle.

2:33

And right next to it you'll often see some vertical fibers.

2:37

And this, it comprises the vertical fibers of

2:40

that Kaplan fiber system.

2:41

And of course, you can trace out those, uh,

2:44

superior lateral genal vessels coming from the popal, uh,

2:47

neurovascular bundle, more posteriorly.

2:49

Likewise, we can visualize these on axial images.

2:52

If you can find that vascular bundle,

2:55

then you can find those KAPLAN fibers. And here at our

2:59

Superior most axial cuts,

3:00

we can also visualize the horizontal fibers.

3:02

Depending on how high your axial cuts go, you may

3:06

or may not be able to see the horizontal component,

3:08

but certainly we can visualize the vertical component

3:11

of this Kaplan fiber system.

3:13

Here it is on Sal images.

3:16

Again, if you can find the vessels, then again,

3:19

you can find those Kaplan fibers.

3:21

And here they are coming down to insert on the su uh, kind

3:24

of supracondylar ridge of the distal femur.

3:27

And again, you can see this, uh, vascular bundle.