0:00

We're talking Lisfranc injuries and anatomy,

0:04

and we've already said that there is a short, stubby

0:07

dorsal C1 M2 ligament, kind of a long, thinner

0:12

but important stabilizer: the plantar C1 M2

0:16

ligament, and then there's the proper one that

0:18

sits in between these two, so it's kind of like

0:21

a sandwich. And that one isn't drawn in yet,

0:24

but that one is also thick and short and stubby,

0:28

and helps stabilize the tarsometatarsal junction.

0:31

There are a few other stabilizers,

0:33

though, ancillary stabilizers, which is

0:35

kind of the title of this section here.

0:37

And these include the anterior tibial

0:39

tendon, which has a broad insertion on

0:41

C1 and the dorsal medial aspect of M1.

0:46

So, the tibialis anterior is

0:48

going to insert in this region.

0:49

The posterior tibial tendon and the

0:52

peroneus longus tendons contribute to

0:54

stabilization of the midfoot, as does the

0:57

plantar fascia, the long plantar ligament,

1:00

and the intrinsic midfoot and forefoot muscles.

1:03

So now let's talk about mechanisms of injury.

1:07

Low-impact midfoot sprains, the exact

1:10

mechanism depends on the direction of force

1:13

and the position of the foot in impact.

1:16

The two most common mechanisms of indirect

1:20

low-impact injuries are forefoot abduction

1:24

and forced plantar flexion injuries.

1:28

And sometimes there's a mixture of

1:29

these two mechanisms at the same time.

1:33

Forced abduction injuries are almost

1:35

always associated with sudden

1:37

rotational change in direction.

1:39

So you see this a lot in big people whose

1:43

foot gets stuck in the ground, and then

1:45

they try to make a rotational movement.

1:47

The foot is in plantar flexion as they

1:49

push off, and the rotational force cracks.

1:52

There goes the Lisfranc ligament.

1:54

And you'll see this a lot in people,

1:56

and people that play the sport of American

1:58

football because they're big,

2:01

they're on turf, they're lumbering,

2:04

so the impact is relatively kind of a

2:06

slow, lower-impact rotational force.

2:10

Forced plantar flexion injuries occur

2:12

when the forefoot is rigidly planted,

2:14

just like we described, in the plantar flex

2:16

position, and the force is applied through

2:19

the metatarsal along its longitudinal axis.

2:23

This produces a compressive force

2:25

through the TMT, or the tarsometatarsal joint.

2:28

Now, you might say, "Well, okay, that's

2:30

obvious, you just explained that."

2:31

But when I say compressive force, I mean,

2:34

this is being tabulated against that.

2:38

So these two crush each other.

2:40

And that is why it's virtually impossible

2:43

to have a serious Lisfranc injury

2:46

without having fractures or microtrabecular

2:48

fractures here, here, here, and here.

2:52

And that is why you look at your STIR,

2:54

your SPARE, your special, your high-quality fat

2:57

suppression images, looking for swelling

2:59

and bone injuries in this location.

3:03

Now, a Lisfranc injury can occur when a

3:05

force, like a falling body, is applied

3:08

to the heel of a plantar flexed foot in

3:10

a patient whose knee is on the ground.

3:13

So say your toe is pointed,

3:16

sorry, your toes are dorsiflexed up.

3:19

The ball of your foot is on the ground.

3:22

And this would be my heel where my wrist is.

3:25

And somebody falls on the back of your

3:27

heel and forces the heel down towards

3:30

the ground when you're in this position.

3:32

That is another obvious but

3:34

important mechanism of injury.

3:36

And you also see that a lot in

3:37

the sport of American football.

3:41

It wouldn't be a bad idea if you linked

3:43

this discussion with our discussion of

3:46

classification of Lisfranc injuries,

3:48

which are coming up when you have time.