0:00

The first case we're going to tackle

0:02

is a 16-year-old with medial knee pain and instability

0:06

following an American football injury.

0:09

Of course,

0:10

there's European football and they are querying

0:14

an ACL tear.

0:16

So generally,

0:17

when I approach a knee case,

0:20

because the axial comes up first,

0:24

it's usually the first thing I look at.

0:26

I have a high volume of cases that I read during

0:29

the day, so I try and be as expedient as possible.

0:32

But if I had to say what the sequence is,

0:34

that gives me the most information.

0:36

as an experienced reader,

0:38

it's the coronal water weighted image.

0:41

So, I can usually tell everything that's

0:43

happening off that image alone.

0:45

But let's go in the order how I might go if I was

0:49

less experienced and I would start out with

0:52

the axial, I'd look at the patellar shape,

0:54

I'd look at the trochlear shape,

0:57

and then I would look at the

0:58

Medial Patellofemoral Ligament

1:00

and the lateral retinaculum.

1:01

I'd look for chondromalacia,

1:03

I'd look at the size of the effusion,

1:04

that gives me an idea whether anything's wrong.

1:07

And then after that,

1:10

I scroll and I read to the history,

1:13

and I always read to the history for every single

1:16

case, whether it's a spine, a liver, or a knee.

1:21

And in my head, I have this thought

1:24

that no matter what,

1:26

whatever the patient says is true.

1:29

There are very few patients who will malinger.

1:32

Maybe in a personal injury case

1:35

and maybe in a workman's compensation case,

1:38

but that's rare.

1:39

So the patient has a symptom.

1:42

There was always a reason for that symptom.

1:44

So I do read normal MRIs,

1:46

but I'm very uncomfortable when I do because

1:48

I know that there is something

1:50

there in most instances.

1:52

So, I continually drill mentally into the case

1:56

until I either find it or I've exhausted every option.

1:59

So here, we have an effusion.

2:02

And just looking at the axial,

2:03

I can tell right away,

2:04

because I'm reading to the history,

2:06

that in the axial projection,

2:09

I know that this is lateral,

2:10

because the patellar almost always tilts laterally.

2:13

So I can tell this is the lateral side,

2:16

and that means that the anterior cruciate ligament

2:18

is going to be on the lateral side.

2:20

So here's my posterior cruciate ligament,

2:22

somewhat round or oblong, fat and dark.

2:26

The ACL, not so much.

2:28

When I follow that ACL, it's fairly gray,

2:32

and I have a great deal of difficulty finding

2:34

it as a contiguous line from anteromedial

2:38

to posterolateral.

2:39

So, I already know that I have an anterior cruciate

2:43

ligament injury of some kind and that

2:45

it's likely to be high grade.

2:47

And this is what they were looking for.

2:49

I'm also looking at the collaterals.

2:51

I can see the lateral collateral

2:53

complex over here.

2:55

I'm not going to articulate all the anatomic

2:57

structures right now in this projection,

2:58

but I can see everything,

2:59

it's pretty dark.

3:01

On this side,

3:02

on the medial side, everything is not so dark,

3:05

especially anteriorly,

3:07

where the tibial collateral ligament lives,

3:09

right here.

3:10

And so, I'm suspicious of a medial

3:12

collateral ligament injury,

3:14

and I have yet to look at anything else.

3:16

I already know that the posterior cruciate

3:18

ligament because of its contour and its signal is intact.

3:22

So without even looking at any other sequence,

3:25

I now know that I have an anterior cruciate

3:28

ligament injury, an MCL injury, an intact PCL,

3:32

and an intact LCL.

3:35

And so,

3:36

I'm going into my next sequences with a lot of knowledge.

3:40

Because there's been a somewhat violent injury.

3:43

You know, it's a football injury.

3:44

It's a contact sport. There's an ACL.

3:47

There's an MCL.

3:48

I am discreetly checking the neurovascular bundle.

3:53

You know, if you miss an ACL,

3:54

not horrible.

3:56

If you miss a vascular injury,

3:57

horrible.

3:58

So, we're checking out the flow voids in the vessels

4:03

in the back and the artery, which is deepest,

4:05

and we're looking at the neurovascular bundle,

4:08

although usually the neurovascular bundle is not

4:11

injured, unless you have a varus insole.

4:14

In other words,

4:15

an injury to the lateral side of the knee.

4:17

So that's good news.

4:18

Let's turn our attention now

4:20

to the water-weighted sequences.

4:22

And this is really how I do it.

4:24

I go right to the water-weighted sequences,

4:26

because, again, for me, time is very important.

4:29

And I know for you, most of you are,

4:31

in private practice, time is very important.

4:34

And even outside of practice,

4:36

time is your most valuable asset.

4:38

So, we're scrolling back and forth.

4:40

We see that there are a series of bone injuries

4:44

which tell you the mechanism of injury.

4:46

First of all,

4:47

there is a microtrabecular injury of

4:50

the inferior patella.

4:52

Right there.

4:54

And what do I mean by microtubecular injury?

4:56

Anything other than a macro fracture.

4:58

Anything other than a visible fracture is a

5:00

microtubecular injury.

5:02

What's in that category?

5:04

Low grade contusion, high grade contusion,

5:07

microtubecular infraction,

5:09

and microtubecular fracture.

5:11

Those are the four stages before you actually have

5:14

a macro fracture.

5:17

So, what's a low-grade contusion?

5:20

You only see it on a water-weighted image.

5:22

What's a high grade contusion?

5:24

You see it on a water-weighted image

5:25

and a T1-weighted image.

5:27

What's a microtubecular infraction?

5:30

Little spidery lines that don't really involve the cortex.

5:33

What's a microtrabecular fracture?

5:35

Little spidery lines that do involve the cortex.

5:40

And then a macro fracture,

5:41

zigzag lines that go through the cortex.

5:44

So now, as we scroll back and forth,

5:46

we get an idea of what the mechanism of injury is.

5:49

We have an anterior femoral terminal sulcus,

5:52

microtubecular injury with slight depression and

5:55

a non-kissing lesion in the back of the tibia.

5:58

So what that means is, this is what happened.

6:00

The femur went back on the tibia with the foot in

6:06

external rotation and the tibia in internal rotation.

6:09

And basically, the tibia subluxed

6:12

relative to the femur.

6:13

And this impartial knee flexion

6:16

banged against that.

6:18

That takes a lot of force to do that.

6:21

So, when that happens...

6:23

Look at my fists.

6:24

The structures in the back will take a stretch.

6:28

They'll also take a compression.

6:31

So, this is a kid.

6:32

It's a young kid.

6:33

The structures are very pliable.

6:35

So to injure these structures back here

6:38

in a child, takes a lot of force.

6:40

So now let's go to the back of the knee,

6:42

and we're scrolling sagittally,

6:44

and we're looking specifically at

6:46

the posterolateral corner.

6:47

And we're very interested in the

6:49

popliteofibular ligament.

6:51

Now remember, I said I didn't see

6:54

a lateral side injury,

6:56

but the posterolateral and

6:57

posteromedial corners,

6:58

you really have to look at the sagittal projection.

7:01

So things look a little bit wavy and a little

7:03

bit stretchy, but they're intact.

7:06

Here is the arcuate ligament back here,

7:08

this little thin structure posteriorly.

7:10

Here's the popliteofibular ligament.

7:12

It's a little bit wavy right there,

7:14

but it's still present,

7:16

still inserts on the fibular head.

7:18

So, that's okay.

7:20

What's not okay is there should be two attachments

7:26

from the posterior meniscus.

7:28

There should be attachment up high

7:30

and an attachment down low,

7:32

and it pretty much goes all the way across from

7:36

lateral to medial, or from lateral to midline.

7:39

Now, let's have a look.

7:40

Let's scroll.

7:41

There's one of the attachments.

7:43

It's flopping in the breeze.

7:46

The other attachment is not visible either.

7:48

So, there is a meniscopopliteal fascicular

7:52

detachment from that stretch.

7:55

Some people might call this a

7:57

meniscocapsular separation.

7:59

I reserve that phrase for when the meniscus

8:02

actually displaces more than a centimeter to a

8:06

centimeter and a half, which hasn't happened here.

8:08

So, I'm just going to call it a meniscal vesicular

8:11

lateral detachment. Does that matter?

8:14

It absolutely does matter,

8:15

because the meniscus can start to do this.

8:17

It can start to turn on itself,

8:19

which is not great.

8:20

Then, as we go a little bit deeper, we see this.

8:23

Now, taking off from the lateral meniscus is a small

8:27

ligament called the ligament of Wrisberg.

8:29

I think we can see it right...

8:31

Let's see.

8:33

There.

8:34

On the coronal.

8:35

Now, that's a point of weakness.

8:38

So at that takeoff,

8:40

you can often get a little bit of a slit,

8:43

and you should have that slit appear

8:45

here normally.

8:46

So, normally,

8:47

the Wrisberg ligament would be separated

8:49

from the meniscus by this little slit,

8:50

and this would be the Wrisberg ligament.

8:52

So let's go in tight into the midline,

8:56

and here is your Wrisberg ligament.

9:01

And look at that interface.

9:02

Now, it's persisting.

9:03

It's still persisting.

9:05

It's persisting on too many slices.

9:07

It's still persisting.

9:08

So there is what we call a posterolateral

9:12

pivot shift Wrisberg rip injury.

9:16

Let's keep going, shall we?

9:18

Let's go to...

9:19

And there's the Wrisberg ligament,

9:21

behind the posterior cruciate ligament.

9:23

There's the Humphrey ligament in front

9:25

of the posterior cruciate ligament.

9:27

Now, let's go to the medial side.

9:29

On the medial side, in children,

9:32

I don't mind if there's signal in the outer third

9:34

of the meniscus. I don't mind at all.

9:36

But I don't want the signal to go like this.

9:40

I don't want the signal to go up and down.

9:42

I don't want the signal to hit the tibial surface.

9:45

And it does.

9:46

So, there's a very low-grade meniscal tear

9:50

posteromedially, right there.

9:52

And what would we do with that?

9:54

Absolutely nothing.

9:55

What would we do with the lateral meniscus?

9:58

The lateral meniscus,

10:00

we might have to tap down with sutures

10:04

because of its hypermobility.

10:05

So that'll be determined at surgery

10:08

when they take the meniscus and see how

10:10

hypermobile it is.

10:12

They won't sew this meniscus.

10:14

They will not repair that Wrisberg rip.

10:16

Let's go back over to the medial side.

10:19

Now with this huge stretch,

10:21

with this massive stretch that's

10:23

occurred in a child,

10:24

where the tibia is translated anterior to the femur,

10:28

the posteromedial capsule is under a stretch.

10:30

What gave way on the lateral side?

10:32

On the lateral side,

10:33

the meniscal vesicular attachment is torn.

10:36

But over here, the meniscocapsular reflection,

10:40

with its multiple short ligaments

10:42

that are hard to see, have been injured.

10:44

This is too swollen.

10:46

There is normally a meniscal posterior tibial ligament.

10:50

Here it is very stretched out.

10:53

That should attach over here.

10:56

So, this is known as a posteromedial ramp lesion.

11:02

Now, another thing that's happening.

11:04

The child is not even standing up.

11:06

Look at what's happening to the meniscus.

11:08

It is prolapsing posteriorly.

11:13

It's a little puffed out right there.

11:15

That's called a brake-stop mechanism injury

11:18

because the posteromedial stabilizers

11:21

at the meniscocapsular reflection are injured.

11:25

Now, a ramp lesion.

11:27

A ramp lesion is a stretch-type injury

11:31

that occurs at the meniscocapsular reflection.

11:35

And we only use this term posteromedially.

11:38

We don't use it anywhere else.

11:40

What are the five types of ramp lesions?

11:44

Well, the first type is this type

11:46

where you've injured

11:47

this posterior meniscal tibial ligament.

11:50

The capsule is swollen and there's nothing else

11:53

vertically orient it.

11:55

That would be a Ramp 1.

11:56

Then you have ramps 2 and 3

11:58

where you might have a vertical partial depth tear

12:01

from the top or from the bottom.

12:04

What's a 4?

12:05

A 4 would be when you have a line in the

12:08

meniscus going all the way from top to bottom.

12:11

What's a 5?

12:13

A 5 would be where you have a double tear

12:16

along with all this going on in the back.

12:19

So now we've got an ACL tear,

12:23

a Wrisberg rip injury,

12:26

a lateral menisco fascicular detachment,

12:29

injury to the brake stop mechanism with a ramp 1 lesion.

12:34

A tiny little, but mostly intra-substance tear

12:36

of the meniscus, we're not going to touch.

12:38

Let's go to the cruciate.

12:40

Let's zoom out.

12:42

And right there in the middle,

12:43

the anterior cruciate ligament stump.

12:46

The distal posterior cruciate ligament stump.

12:50

And there is a giant hole in the middle.

12:53

You can drive a large Toyota through that hole.

12:59

Posterior crucial ligament, as we suspected.

13:01

Fine.

13:02

All right,

13:03

let's go to the coronals and

13:05

look at the collaterals.

13:07

Popliteal origin, tendon origin, normal.

13:11

Fibular collateral ligament, intact.

13:15

Scant swelling, but intact.

13:18

The biceps femoris and conjoined insertion

13:21

on the fibular head, intact.

13:23

The medial collateral ligament, as we suspected,

13:27

torn anterior and proximal.

13:30

There's also a meniscofemoral ligament.

13:32

It's intact right there.

13:35

There's also a meniscotibial ligament.

13:37

It's intact right there.

13:39

When you get anteriorly,

13:41

this is known as the meniscopatellar ligament.

13:44

This should go towards the patella and it should

13:46

arc off towards the superomedial aspect of

13:50

the knee as it does.

13:51

This is normal.

13:52

That's normal. That's not a detachment.

13:55

All right,

13:55

let's look at the T1-weighted image for giggles,

13:58

because we're not going to get

13:58

a lot more out of it.

14:00

Now, I know in Aus, you guys do a lot of proton-density

14:04

imaging instead of T1 imaging.

14:06

I'm against that.

14:08

And you do it because it helps your visualization

14:11

of meniscal tears. But you don't need that.

14:13

If you combine the T1 and the proton-density

14:15

fat suppression, you don't need that.

14:17

And a proton density will obscure the

14:20

bone findings, including fractures,

14:22

including osteomyelitis.

14:24

So, I'd much rather have a true T1.

14:26

You can also see our very low grade

14:29

meniscal injury right there.

14:31

You can see our swelling and the slight

14:34

corrugation of the posterior meniscotibial ligament.

14:38

How are the growth plates?

14:39

They're open. They're fine.

14:41

That's important because it's a child.

14:43

To fix this ACL,

14:45

you want to avoid drilling through

14:48

open growth plates.

14:49

We have an effusion with a dilute hemarthrosis

14:52

with a little methemoglobin staining.

14:55

There is your fracture.

14:57

There is your fracture,

14:58

microtrabecular fracture with cortical involvement

15:01

in the posterior tibia.

15:03

You're not going to see that on an x-ray.

15:06

Then, you've got your ramp lesion on your medial side,

15:10

and you're pretty much done.

15:11

There is a T2.

15:12

It doesn't add much except showing you,

15:14

once again, the hole, the size,

15:18

the sheer absolute rupture of the mid portion

15:22

of the anterior cruciate ligament.

15:26

Now, there's one other finding here that's

15:28

a little bit confusing.

15:29

Some of the fibers of the anterior cruciate

15:31

ligament have folded down on themselves,

15:34

creating the impression of a mass right there.

15:37

So, that might be a little confusing.

15:39

You want to go back and make sure, see,

15:41

there's the ACL twisted down on itself.

15:45

You want to make absolutely sure you

15:47

don't have a bucket handle tear.

15:48

You look for meniscus truncated and separated

15:52

from itself into two pieces.

15:54

The patient does not have that.

15:56

That would completely change the management of

15:58

this case and how long you wait for surgery.

16:00

They will let this knee cool off.

16:02

They will try and repair the ACL while

16:05

avoiding the growth plate.

16:07

They will leave the medial meniscus alone.

16:09

They will test the lateral meniscus at surgery

16:12

to see if it needs to be tacked down.

16:14

They will leave the MCL alone.