0:01

So I don't know what the history was, but again,

0:03

I think a young patient with knee injury start with the sagittal

0:08

images. A lot of abnormality here, a lot of edema.

0:13

We starting with the medial side, that's the semimembranosus coming in,

0:18

inserting we can see a lot of edema here.

0:24

There is SMA edema in the posterior medial tibial plateau, again, like an,

0:29

uh, osteochondral impaction injury.

0:32

And we see that the medial meniscus is almost entirely absent.

0:37

We just minimal residual meniscal tissue seen.

0:43

And as we go more centrally towards the intercondylar notch,

0:47

we start seeing as if there are two interior horns. One here,

0:52

second one here, and the posterior horn is completely missing.

0:56

So this is known as the double delta sign. This suggests that there is a, a,

1:01

a longitudinal medial meniscal tear and more along the

1:06

posterior half, and then the torn meniscus has flipped anteriorly.

1:10

So this is an example of a bucket handle tear with an anterior flip.

1:17

And as

1:17

We, that's the question.

1:18

Yes.

1:19

Um, sorry to interrupt. Uh,

1:21

when do you use the terminology osteochondral fracture,

1:24

subc chondral fracture and microtrabecular fracture?

1:28

Okay. So osteochondral injury is something like this where, uh, we have,

1:33

um, um,

1:35

in like my edema just beneath the subc chondral bone, and you see that,

1:40

um, uh, evidence of impaction here,

1:42

like it's not completely hyperintense.

1:45

You see this like slight hypo intense linear area,

1:48

which suggests that there has been an impaction. And you'll often see, um,

1:53

abnormality in the overlying cartilage.

1:54

It's better appreciated when you see it along those, uh,

1:57

like the pivot shift mechanisms of injury. I think we have it in this case.

2:01

I can, um, show it to you. I'm going to go towards the,

2:07

yeah, so this would be a classic example. So there,

2:09

there is injury to the cartilage, and then, uh, there is an, um,

2:14

there's marrow edema right in that area of subc chondral bone.

2:17

So suggest that there has been like an osteochondral impaction injury,

2:21

whereas microtrabecular injuries are, um, um,

2:25

they don't have to be perfectly in the subc chondral area,

2:28

so you'll know that no, it was not directly like an injury to the cartilage. So,

2:32

um, but they, the most common site is, um, um,

2:35

like metaphysis and you see them sometimes with injury. Uh, like for example,

2:40

the patient had a direct fall on the knee.

2:42

They will often get a microvascular injury in the proximal tibia.

2:46

So doesn't have to be perfectly in the subc chondral bone.

2:49

You'll have a geographic area of marrow edema, and you'll see, uh, uh, uh,

2:54

irregular linear hyper intensity. That's your fracture line,

2:57

you call it as a micro fracture when it's not a complete fracture.

3:00

So if it goes through and through from one cortex to other cortex,

3:03

it's a complete fracture. If it's not displaced,

3:06

it's a non-displaced complete fracture. But if it's an incomplete fracture,

3:09

non-displaced, um, and if it doesn't involve the cortex,

3:13

you'll only see it on mri.

3:14

Those are the fractures that you cannot call on x-rays because the cortex is

3:17

intact.

3:18

And sometimes those are even hard to call on CT because you don't like the, the,

3:22

the clue to that micro presence of microtrabecular fracture is just marrow edema

3:27

around it. And that, um, and also you see the fracture line, uh,

3:31

very nicely on MR images. Um,

3:33

because of the contrast resolution on images on ct,

3:36

you have the trabecula and it's very hard to pick up any disruption of the

3:40

trabecula on ct.

3:41

So the best imaging modality to pick up microtrabecular fractures is Mr,

3:44

where we see a geographic area of marrow edema.

3:47

And in the center of that geographic area of marrow edema,

3:50

we have that irregular, um, hyperintense linear signal abnormality.

3:54

That's your impaction fracture line of the trabecula. So we've, we saw,

3:59

um, the, um, you can call this as a marrow contusion too,

4:03

along the posterior aspect of the medial tibial plateau. We have the, uh,

4:08

bucket handle tear of the medial meniscus with an anterior flip.

4:12

And as we move, uh, centrally towards the intercondylar eminence,

4:16

uh, this is a, like we see as if there are two PCLs.

4:21

This is known as the double PCL L sign.

4:23

This is also a sign that's associated with bucket handle tear.

4:27

We already see that there's a bucket handle tear of the medial meniscus.

4:30

And once we come laterally, uh, we,

4:34

we see that the posterior hand of the lateral meniscus is missing.

4:40

Okay, I take it back,

4:41

like this double data sign is seen on the lateral side and this double PCL,

4:46

it's, it's probably coming from the,

4:48

from the medial meniscus because a large portion of the medial meniscus was

4:52

missing. And I think that entire, um,

4:55

the to meniscal tissue has flipped centrally in the interocular eminence.

5:00

And that gives rise to the double PCL sign. So, um,

5:03

bucket handle tears of both medial and lateral meniscus as we, and,

5:08

um, this is your PCL increased signal.

5:12

There's some fiber disruption at tibial attachment.

5:15

So there is PCL sprain with probably a, a low grade partial tear.

5:19

Largely it's intact. And then, uh, I don't see an intact ACL.

5:24

And you can see this dump of the ACL. You can see, uh,

5:27

the tibial insertion here. And this is the torn free end, um,

5:32

uh, the stump of the ACL with this torn free end here.

5:36

So complete tear of the ACL bucket handle tears of menisci,

5:40

um, impaction injury along the,

5:45

the lateral femoral condyle and the posterior aspect of the lateral tibial

5:49

plateau. So when you have, this is a classic, uh,

5:52

marrow contusion pattern that suggests a pivot shift mechanism of injury. Um,

5:57

so in field, uh, when, um, the player is, uh, um,

6:01

with the flexed knee, if the, um, um, the knee undergoes in valgus force,

6:06

uh, that's your pivot mechanism of injury,

6:09

and you get this classic narrow contusion pattern. So when you have a,

6:12

a pattern like this, you can s you can like, um,

6:16

guess what the mechanism of injury was. We also have mar edema here.

6:21

And, uh, we see the, the, the linear high point density here.

6:24

So there's a non-displaced fibular fracture, I think to see the fracture line,

6:29

uh,

6:29

fracture line is better seen on T one weighted images you see that appreciate

6:33

that non-displaced fibrillary tip fracture.

6:36

And also now that we have the non-displaced fracture of the fibrillary tip, um,

6:40

that makes us think that there are very high chances, uh,

6:43

or this is an indirect evidence of, um,

6:46

that there is post lateral corner injury. Um, so we'll, uh,

6:51

we looked at the lateral collateral ligament complex, uh, of the knee,

6:55

like water ligaments constitute the postal lateral complex.

6:58

This is how they're seen on sagittal the two main constitutes.

7:01

This is the biceps tendon posteriorly,

7:04

and they form almost like AV on the sagittal images. This is the biceps tendon.

7:08

This is the fibular collateral ligament coming in,

7:11

inserting onto the tip of the fibula. So there is an injury to its insertion.

7:16

Before we move on to axial images,

7:17

another thing that we saw that marrow contusion along the posterior aspect of

7:21

the medial tibial plateau,

7:22

this is a counter co injury in your pivot shift mechanism of injury.

7:26

So that is also an expected finding in an injury pattern like this.

7:33

We didn't talk about the extensor mechanism on the sagittal images. Um, you can,

7:37

um, review the extensor mechanism. This is the quadricep tendon,

7:41

patella particular tendon, and which inserts onto the tibial tuberosity.

7:45

So that looks okay, part of joint effusion. Uh,

7:49

we move on to axial images review. So again,

7:55

no trochlear dysplasia butler is central.

8:00

This is the adductor tocal with the MCL inserts,

8:06

which I was on the other side. This is the median side,

8:10

that's the adductor tocal with the MCL inserts. This is MPFL.

8:14

Now you see that nice black band of M-M-P-F-L,

8:17

which we didn't see it on the earlier example.

8:22

And this is the poster medial corner again. And this one see how, uh,

8:26

nice and impacted seen, whereas in the first example,

8:28

this is what was disrupted. So this is your posterior oblique ligament,

8:31

this is your semiosis, and this will be a oblique popal ligament.

8:37

Whereas in this case, um, this is like a nice contrast.

8:40

We have injury on the postral lateral side.

8:42

So this is an example of A-C-L-P-C-L injury with posterolateral complex injury.

8:47

So here what we are looking at this popliteus, um, muscle

8:52

as we follow it,

8:57

this is the populous tendon now,

9:02

and we see a focal discontinuity, um, in the tendon.

9:07

So this is, uh, a high grade partial tear of the populous tendon.

9:11

So non-displaced fibrillate fracture, uh, with injury to the FCL.

9:15

And then now we have a high grade partial tear of the pletus uh,

9:20

tendon. So all this constitutes a post lateral coronary injury.

9:24

This little structure here is the popple fibular ligament.

9:28

This is an important constitute of post lateral complex.

9:31

So as we can see it arises from the, if you follow it,

9:36

this is fibula.

9:37

So it arises from the tip of the fibula and goes and inserts onto the,

9:42

the popple myotendinous junction. So if you follow it,

9:45

it'll go and insert onto the popliteus tendon. So if you see, again,

9:49

it's not a nice discrete contiguous structure.

9:52

So there's entry to the pope fibula ligament,

9:57

and there's another,

9:59

another ligament that is a constitute of post lateral complex is the A ligament.

10:04

So that's nothing but con condensation of the post lateral joint joint capsule.

10:08

So again, as we saw here, this is a non fat side, so the edema is not,

10:13

uh, that evident. But if you see here, all these structures are conduced and,

10:18

uh, injured. So this is,

10:20

this is where your AIC ligament will be the condensation of the postal lateral

10:23

joint capsule. So there's a sprain, there's sprain of the AIC ligament. So, um,

10:28

how will we summarize the findings on this case? Um, we have, um,

10:33

we can go from the, um, starting from the medial side,

10:36

we have the medial meniscal tear with a bucket, which is a bucket handle tear,

10:40

and it has flipped centrally in the intercondylar notch.

10:44

So giving rise to double PCL sign, PCL sprain,

10:49

complete ACL tear. Then, uh,

10:54

tear of the lateral meniscus, which is also a bucket a**l tear.

10:58

But here the flip is anterior.

11:01

Then we have injury to the post lateral complex with non-displaced FI

11:05

fracture,

11:06

tear of the high grade partial tear of the pope tendon injury to the accurate

11:10

ligament, um, and the popal fibular ligament. And then we have,

11:15

um,

11:17

osteocondral impaction injury along the lateral femoral condyle marrow contusion

11:21

of the posterior lateral tibial plateau.

11:23

So that suggests pivot shift mechanisms of injury.

11:26

And then you have counter co contusion along the posterior aspect of the medial

11:31

tibial plateau. And, um, we have, um,

11:37

a large joint effusion and some mechanism is impact,

11:42

I think, um,

11:45

that is all on this case. Again, the importance of, um, like how,

11:50

uh, we talked about the significance of picking up post medial coronary injuries

11:54

along with, um, other ligament injuries of the knee. Uh, similarly,

11:59

it's very important to talk about the post lateral complex. Um,

12:04

and when we have ligament injuries, particularly the cruciate ligament injury,

12:07

and it's the same thing, just this complex is really important. Mm-hmm.

12:11

And maintaining the stability of the joint. And if this is not taken care of,

12:15

um, and the surgeon plans, just the, the cruciate ligament repair,

12:20

that repair is going to fail early. So they have to, uh,

12:24

take care of the posterolateral, uh,

12:25

con as well and make sure the joint is stable before they do an ACL

12:30

look graft there.

12:33

And I think this is more commonly seen as compared with the post medial complex

12:38

injuries. So any questions on this one?

12:43

It's extended to, uh,

12:44

include the mechanism of injury in your conclusion of the report. Uh,

12:48

Um, no, not, not really. You don't have to report, uh, put it in your reports,

12:52

but it's just, um, uh, good for our understanding. So, uh, for me, I think the,

12:56

the real importance of, uh, like once you get an idea of mechanism of injury,

13:01

uh, uh, you know what to expect.

13:04

So your chances of missing other findings gets really low. So like, for example,

13:08

the other ca uh, case was me valgus mechanism. So when you know that, uh,

13:13

in valgus, if there is stretch on the medial side,

13:15

there is going to be impaction on the lateral side.

13:18

So you know what associated injuries to look for. It just makes your, uh,

13:23

uh, uh, picking up a findings faster and, uh, less chances of misses.

13:28

Um, 'cause you know, what is expected, like for, in this case, for example,

13:32

like, you know, if it's a pivot shift mechanism of injury, water limb expected,

13:35

there will be, um, a cruciate ligament tear.

13:38

There'll be associated collateral ligament tear, meniscal tears,

13:41

and I'm going to get a, like,

13:42

I may or may not get an counter co injury along the posterior aspect of the

13:46

medial tibial plateau. So even before you look at the case, you know,

13:50

this is what you, what, um, um, uh,

13:53

you looking for and this makes it easier and the chances of missing other small

13:57

findings becomes less.

13:59

Certainly when you look at the postal catal postal lateral corner,

14:03

you get to see the complexity of the structures there.

14:06

And some of them are very closely adhered to each other. Yes. Uh,

14:09

of the structures, what is the most critical thing that you should not miss,

14:12

and what's the hardest to describe?

14:15

Okay, so I think, um, the really, the, the, the big structures,

14:20

and actually they're easy to see there. You will never, uh,

14:23

because these are big structures.

14:25

Once you get a little comfortable reading Mr knees,

14:28

I think the two important structures are your fcl L and your biceps tendon.

14:32

Yeah. So, uh, fcl L and biceps tendon, populous tendon, the,

14:36

these are the three main constituents of the postal lateral con uh, con.

14:39

And these are big structures, so it's not, um,

14:42

a difficult to really pick up injuries to these structures.

14:45

What gets challenging are these small ligaments, the popo fibular, uh,

14:49

the a uh, the fave fibular ligaments. Those are the comp, uh,

14:53

constituents of postal lateral coronary injury. Now,

14:57

the good part is when there is injury, there is edema,

14:59

and that edema can make these structures look more prominent.

15:04

For example, uh, we saw the, the pop, um,

15:07

popularity of fibular ligament. In a normal knee,

15:10

it's hard to pick up this ligament,

15:12

but now because we have fluid and edema around it,

15:14

you can see the structure slightly more, uh, uh,

15:18

like better as compared to anoma knee. So that helps.

15:21

But even if you can't identify the ligament, it's still,

15:24

if you know the anatomic location and if you see a lot of edema and fat

15:27

stranding there, like for example, aqua complex,

15:30

like it's not a discreet band that you'll see. It's just the, the the,

15:33

like how we have this whole capsule here, and this is posterior oblique.

15:38

This is oblique post, uh, populated ligament. Similarly,

15:41

whatever is on the lateral side is like this part is aqua ligament.

15:44

And if there is edema and inflammation there, you,

15:47

you may call that there is a sprain of the OID ligament.