0:01

So next case, this is a 20-year-old skateboarder, uh,

0:04

with injury two months earlier

0:06

and he had chronic recurrent instability,

0:09

although on further interrogation,

0:11

I mean this is a skateboarder, right?

0:13

So he's fallen multiple times.

0:14

So he is had multiple injuries over his years

0:16

of skateboarding and I believe he was professional

0:19

or maybe semi-professional.

0:22

He had some, uh, uh, on physical exam, some vari laxity

0:26

and a positive quad active test.

0:28

And basically what that is is when you have a PCL tear,

0:32

your knee rests with slight sag, meaning

0:35

that tibia translates posteriorly.

0:38

And so when the patient's on the exam table

0:40

with their knee flexed,

0:41

once they activate their quadriceps tendon,

0:43

that pulls the tibia forward.

0:45

And hence that is a positive quad activation test.

0:50

Now the reason why I pull up this case is

0:52

'cause this patient is a chronic injury.

0:55

So if you've reviewed the images ahead of time,

0:57

this is his left knee, this is the symptomatic knee

1:02

and he doesn't have a lot of edema

1:04

or he doesn't have any edema frankly,

1:06

to really draw your attention to where the pathology is.

1:10

So what I've actually done is he had bilateral, uh,

1:12

knee MRIs done with in within close proximity to each other,

1:16

but it was advantageous for us

1:17

because we could compare his, uh, contralateral knee,

1:21

which was actually relatively more stable compared

1:23

to his injured knee.

1:25

And so I wanna focus on this fibular collateral ligament.

1:29

Again, find this apex of this femoral epicondyle

1:31

and you'll find the fibular collateral ligament.

1:33

And as we followed inferiorly,

1:35

here's the biceps semus muscle

1:36

and tendon, there's the fib collateral.

1:40

We can see that it just sort of dies and disappears

1:42

before we even get to the fibula.

1:44

Again, biceps fems tendon.

1:47

If I show you the contralateral side,

1:48

maybe that'll convince you

1:49

that there's something wrong about this knee.

1:51

Here's fibular collateral ligament,

1:53

we're gonna follow it inferiorly.

1:55

And here it is again, interdigitating with the biceps fems.

2:00

And one more time, we follow this guy down inferiorly,

2:04

the collateral ligament right here

2:08

and it just sort of disappears there.

2:10

So because this is not acute injury, again, you may be,

2:14

you may easily miss this.

2:15

And in fact, this was missed.

2:17

This was that these were outside MRIs

2:19

and I was asked to review it at the request

2:21

of the orthopedic surgeon.

2:23

Alright, so let's look at the coronal images.

2:26

Here's the normal knee and then here's the injured knee.

2:30

And you'll notice on the injured side,

2:31

there's a little slight dip

2:33

or redundancy of that fibular collateral ligament.

2:36

Lemme go ahead and blow that up.

2:38

Here's that slight redundancy.

2:40

And you notice you can't really quite follow

2:42

it down to the fibula.

2:44

And here's the other knee, the uninjured knee.

2:47

And here at least on this one slice, you can

2:50

for the most part, follow

2:51

that fibular collateral ligament all the way down.

2:54

So this was the basis of this patient's

2:56

chronic varus instability. But,

2:59

Uh, from the history, the patient also had some degree

3:01

of posterior instability or posterior laxity.

3:05

So if you interrogate both knees,

3:07

this is the uninjured injured side.

3:08

You can see that there's a little bit of the thickening

3:11

of the posterior crucet ligament.

3:13

There are some fibers that are intact,

3:15

but here, kind of this posterior, uh, bundle

3:18

or poster medial bundle, if you will, is thickened,

3:20

uh, with increased signal.

3:22

So this tells us that there's been some sort of injury

3:25

to the posterior cruciate ligament

3:26

before, whereas on the normal side we can see it's nice

3:29

uniform and thickness and signal intensity.

3:32

And I think Dr. Chang showed you a beautiful case

3:35

of a patient who had a posterior cruciate injury,

3:38

posterior cruciate ligament injury

3:39

with subsequent follow-up, how it can fibrosis

3:42

and look almost for all intents

3:43

and purposes, normal on follow-up exam.

3:47

So just a good example of more of a chronic injury

3:49

to keep, uh, a lookout for.

3:52

So this patient I follow-up, was not,

3:54

hadn't undergone surgery, was leaning more towards surgery

3:58

to include a poster lateral corner reconstruction with

4:01

or without a posterior cruciate ligament reconstruction.

4:08

Oh, one more, uh, cherry on the top.

4:11

Uh, I put that slide in to remind me and I think Dr.

4:14

Pather will discuss this in her popal fossa talk.

4:17

Um, shortly is in this injured knee, you notice that the,

4:22

um, anterior tibial artery has a high origin from

4:27

the popal artery.

4:28

Usually this takes off more inferiorly below the joint line.

4:31

So here it takes off, uh, just at

4:34

or above, above the joint line.

4:35

And this is an aberrant, anterior tibial artery.

4:38

You can see how it's closely opposed to the posterior aspect

4:41

of the proximal tibia.

4:43

If you go to his other knee, you'll notice

4:45

that he doesn't have this configuration.

4:46

So it's not always bilateral.

4:48

And if you look at the literature, the incidences

4:50

of this aberrant anterior tibial artery, it's 2%.

4:56

So you should be seeing it around every 50 knee cases.

4:59

And if you aren't seeing this at all,

5:01

you're not looking hard enough.

5:03

And this definitely has implications in this case

5:05

because remember,

5:06

this patient may undergo a posterior cruise ship

5:08

ligament reconstruction.

5:10

So often they'll have to put trans osseous tibial tunnels

5:13

to get to the posterior aspect of the tibia.

5:16

And when you have this vascular structure right behind it,

5:19

well that might result in an intraoperative

5:22

consult to vascular surgery.

5:24

So you definitely wanna alert your orthopedic surgeon

5:26

to this anatomic variant.