0:00

Let's talk about some of the other

0:02

sequences, besides the standard axial PD

0:07

and T2, and the series of sagittal images

0:10

that you might use for the foot and ankle.

0:12

I'd like to start with this one,

0:14

which many people might call coronal.

0:18

You can see it's actually paracoronal,

0:20

and the foot is plantarflexed.

0:23

So, what do we use this for?

0:27

We use it to look at the talonavicular dome,

0:29

and in fact there is a very subtle

0:31

talonavicular dome abnormality, which I don't

0:33

think you'd pick up if it wasn't for some

0:35

other support that we've given you here.

0:38

But the paracoronal or coronal with the

0:41

foot plantarflexed or dorsiflexed is

0:44

the sequence to look at the talonavicular dome.

0:48

It's also an excellent supplementary sequence

0:52

to look at the collaterals like the deltoid.

0:54

Although, you know, the

0:55

deltoid never gets operated on.

0:57

So if you miss deltoid tears,

0:59

it's usually not a big deal.

1:00

They usually heal on their own.

1:01

I'm not telling you to miss them, but you

1:03

might also use this sequence to look at

1:05

some of the lateral collateral ligaments

1:07

whose anatomy we'll detail later on.

1:10

But perhaps the greatest strength of this

1:14

sequence, when the foot is plantarflexed, and

1:17

only when it's plantarflexed, and only when

1:20

the field of view is big, is the ability to

1:23

look at the intertarsal ligaments of the foot.

1:27

Like that one right there.

1:30

Or, the most important one of all, the one that

1:33

goes between the cuneiform and the base of the

1:35

second, also known as the Lisfranc ligament.

1:39

And you're gonna learn that there are

1:40

several components to the Lisfranc ligament.

1:43

There are central and plantar

1:45

components, so it gets a little dicey,

1:47

but that's a story for another day.

1:49

But there she is, there's a

1:51

small little erosion nearby.

1:53

But that is one of the great

1:54

strengths of this projection.

1:58

Now, the projection was obtained with a long TR

2:01

and a long TE, so it's a T2 with fat suppression.

2:04

And that particular pulsing sequence, T2 with

2:08

fat suppression, is an excellent identifier and

2:12

modifier of ligamentous anatomy and pathology.

2:18

But it's not the ultimate detector sequence.

2:20

That designation falls to the PD SPUR.

2:23

So if you want to see swelling, if you

2:25

want to see where the abnormalities

2:27

are located, generally use the PD spur.

2:30

If you want to then drill into the

2:31

ligament and see that it's contiguous

2:34

and black, then you use the T2.

2:38

Now pitfall, what's the signal of scar?

2:43

What's the signal of hemosiderin?

2:45

Dark.

2:46

What's the signal of old blood?

2:48

What's the signal of ligaments?

2:50

Dark.

2:51

So you can get fooled if you just look at the

2:54

T2 into thinking that a scarred hemorrhagic

2:58

ligament, which is nice and straight.

2:59

That happens a lot in the anterior

3:02

cruciate ligament of the knee.

3:05

But don't let it happen to you.

3:06

And especially, don't let it happen

3:08

to you in the Lisfranc area, or you're

3:10

going to make a very heinous miss.

3:13

Okay, let's zoom out a little bit, and let's

3:16

go over to another sequence that I didn't

3:18

show you earlier, in the series of axials.

3:22

Now, if I'm interested in, say, the peroneus

3:27

brevis tendon, or the posterior tibial tendon,

3:30

I am most often going to get a series of axial

3:33

obliques that include Proton density spur,

3:38

gradient echo, and T1.

3:41

Or, I can use the T2 and

3:44

substitute it in for one of those.

3:45

I usually do not get four.

3:48

So it's going to be dealer's

3:49

choice for any one of those four.

3:52

If I was going to drop one, I usually drop the T1.

3:58

Now, the T1 does have some

4:00

strengths in this projection.

4:01

One of its strengths is it probably

4:03

does, if not the best job, close to

4:06

the best job at seeing the talonavicular dome.

4:09

Thank you.

4:10

And in this case, very subtle anteromedial

4:14

abnormality of the talonavicular dome.

4:16

You probably would have missed it.

4:18

Let's cross reference it on the

4:21

accompanying water-weighted image.

4:24

Let's see if it'll let us do it.

4:27

There it is, right there.

4:28

Ooh, that's subtle, isn't it?

4:31

Look at that little ding right there.

4:33

Let's see if I can blow it up for you.

4:35

Oh, it won't let me.

4:36

There it is.

4:38

Tiny little ding.

4:39

So T1 really comes into play.

4:43

That is, particularly when bone

4:46

marrow and the edge of the cortex are

4:49

critical for ligaments, not so much.

4:53

I'd encourage you when you're looking

4:54

at these tendons in the axial oblique

4:57

projection to have at least three sequences.

5:00

The T1 can be one of them, but you may

5:03

choose to drop the T1 knowing that you

5:06

have to look at another T1 and another

5:08

projection to be sure you don't miss

5:11

a very subtle cortical or subcortical

5:15

bone abnormality.

5:16

And finally, just as a recap, this coronal

5:20

is not a straight up and down coronal.

5:22

It's an oblique coronal that goes along the

5:24

long axis of the axis of the metatarsals so that

5:30

you can image all the ligaments of the midfoot.

5:33

That's the purpose of having this obliquely

5:38

oriented coronal projection and the one

5:40

that you are most interested in every single

5:43

case where the midfoot is on the image.

5:46

You better check that Lisfranc ligament.