0:01

As we consider the mechanism of injury

0:03

for ulnar collateral ligament abnormalities at the thumb.

0:07

Historically this was referred to as the gamekeeper's thumb,

0:11

and as we think about the times when we had hunters trapping

0:15

small animals, sacrificing them on site, they would do so

0:19

by breaking the neck of the animal

0:21

between the thumb and index finger.

0:23

And we can imagine that that could be a chronic, repetitive

0:27

injury or it could be an acute injury

0:30

or even acute on chronic, of course.

0:33

Now the more common mechanism would be something like this,

0:37

the thumb being, uh, exposed

0:41

to this abduction force through falling in this case

0:45

with the ski pole in the hand that that the, uh,

0:48

more classic again, contemporary injury.

0:50

And again, we could imagine this being a chronic repetitive

0:53

microtrauma perhaps for the beginning skier

0:56

and acute on chronic or specifically an acute lesion.

1:01

So as we think about the injuries that can occur here,

1:06

we see the hyper abduction force at the level

1:09

of the metacarpal phal joint.

1:11

And you can imagine here again, a stretching phenomenon,

1:15

a plastic bowing type deformity

1:17

with chronic repetitive microtrauma

1:20

and acute post traumatic event again, or acute on chronic.

1:25

As we consider how this diagnosis with historically made,

1:29

it was through stress radiographs of the thumb.

1:32

Here you see the fingers

1:34

of the examiner placing stress at the MCP

1:38

to determine whether there's widening at the ulnar

1:41

aspect of the joint.

1:43

As we look at the radiograph lines placed along the long

1:46

axis of the metacarpal long axis of the proximal phx,

1:50

that angle is what we're looking for.

1:53

If it's greater than 35 to 45 degrees considered

1:58

to be abnormal.

1:59

If you have the other side for comparison,

2:02

if there's a greater than 10 degree difference

2:05

between the normal slash asymptomatic or uninjured side

2:09

and the injured side, that would be considered abnormal.

2:13

With the advent of more advanced cross-sectional imaging

2:17

techniques, such as mr, there is no need now

2:19

to add an additional hyper abduction force

2:22

to the stress radiograph.

2:24

Rather, we can non-invasively

2:26

and directly visualize those structures.

2:30

As we think about a classification system

2:33

for ulnar collateral ligament injury, we can have

2:36

that elongation, that plastic bow deformity.

2:40

In this setting, we would either have an injury

2:43

that didn't result in a complete failure,

2:45

or again, perhaps chronic repetitive microtrauma.

2:49

Other areas in the body you may, uh,

2:52

encounter such an injury.

2:54

Think about the medial patella reac where it becomes

2:57

attenuated and lax, where you'll see subluxation at

3:02

that patella femoral articulation.

3:04

Something similar can happen with the UCL, again,

3:08

considering that hyper abduction force

3:11

with failure at the distal attachment.

3:14

This consider the type one lesion.

3:18

Remember that if there's no osseous component,

3:20

the plain fill may look completely normal In these cases,

3:24

because we're dealing with the ulnar aspect

3:26

of the articulation, soft tissue prominence

3:30

and those findings are sometimes obscured by

3:33

that first web space.

3:35

Here's a variation of that type one.

3:38

We're seeing failure at the UCL

3:40

but not at its distal attachment,

3:42

rather at its proximal attachment.

3:44

As you look at the fluid sensitive sequence,

3:47

the secondary finding of seeing

3:48

that high signal intensity extend proximally down the

3:51

metacarpal shaft telling us, alerting us to the fact

3:55

that we've got capsular insufficiency.

3:58

In this case, we can clearly see the torn and detached end.

4:02

However, you can imagine if this person presented

4:05

to us more sub acutely, perhaps the presence

4:08

of granulation tissue

4:09

and synovial hypertrophy, soft tissue changes may obscure

4:15

that distal, or excuse me,

4:16

proximal discontinuous attachment site arrow here again

4:20

pointing to that discontinuity.

4:23

Much more high resolution study here acquired

4:27

with a focal microscopy coil.

4:30

The advantage you can clearly understand,

4:33

very high resolution imaging, the disadvantage,

4:36

very limited field of view in this case.

4:39

As you look at the ulnar collateral ligament,

4:42

we can clearly see the discontinuous distal end from the

4:46

base of the proximal vein links.

4:48

We can see the intact relationship

4:51

of the abuc diap neurosis lying superficial to that

4:55

inside two UCL.

4:57

By inside two, I mean it has not retracted proximally.

5:01

And we can even see detail with respect

5:03

to articular cartilage at the articular surfaces

5:06

and easily identify things like bone marrow edema,

5:10

subcutaneous edema as well.

5:15

When we think about the type two lesion,

5:17

this probably least encountered failure in the mid substance

5:20

of that ulnar collateral ligament

5:23

and the type three lesion, O osteos AULs.

5:26

And now we move into the territory

5:28

where these lesions are identified on plain film.

5:32

When we look at the plain film,

5:34

we should not only identify the irregularity

5:37

of the ulnar base of the proximal pH length,

5:40

but really get every piece

5:41

of inflammation we can out of that plain film.

5:44

In this case, the displaced fragment coming

5:47

to lie proximal at the level of the joint line.

5:51

That may give us a clue with respect

5:53

to a potential complication with the

5:56

Ligament, the torn component with the osseous fragment.

6:00

And again, its relationship with the overlying a neurosis.

6:05

As you look at the T one weighted mr, we know

6:08

that we're gonna closely look at the subc chondral bone

6:11

plate, look for irregularity, in this case,

6:14

a small osseous fragment.

6:16

As you look at the soft tissues distorted, in this case,

6:19

thickened, but difficult to really assess again,

6:23

the ligament proper in the subacute setting,

6:26

this can be the case

6:27

because you've got this granulation tissue

6:30

that ultimately develops.