0:00

So let's discuss lunate and peri lunate dislocations.

0:05

Here's our first case where we see an abnormal configuration

0:08

of the lunate companion case,

0:11

also abnormal configuration of the lunate.

0:15

If we go back to the first case, we see

0:17

that the lunate has a pie shaped on the frontal projection

0:20

and is not articulating

0:22

with the distal radius on the lateral projection

0:24

and is projecting palmar

0:27

or volar along its distal articular surface.

0:30

Whereas in this companion case, while we have a abnormal

0:35

configuration on the frontal projection,

0:37

that almost looks like a pie shape

0:40

on the lateral projection.

0:42

The radius and lunate are still articulating.

0:46

So the proximal lunate is articulating with the radius,

0:49

but the distal lunate is not articulating with the carpus.

0:54

Here are our normal carpal arcs, also known

0:56

as the arcs of gula.

0:58

So one refers to that the base

1:00

of the proximal carpal row should all line up as well

1:04

as the distal cortices of that proximal carpal row.

1:08

As for line two, line three is the cortices

1:13

of the distal carpal bones.

1:15

So these are our carpal arcs.

1:17

And example on the right shows obvious disruption

1:20

of those carpal arcs

1:22

with a pie shaped configuration to the lunate.

1:25

So these are two companion examples of a peri lunate

1:28

and lunate dislocation.

1:30

So in a peri lunate dislocation, there's failure

1:32

of the radio capitate ligament.

1:34

The capitate becomes disarticulated from the lunate.

1:38

The lunate remains in anatomic alignment with the radius.

1:41

Whereas in a lunate dislocation, you have failure

1:45

of the radio capitate and also the volar

1:48

and dorsal radial carpal ligaments.

1:50

The capitate is disarticulated but remains coline

1:54

or aligned with the radius.

1:56

However, the lunate now is completely disarticulated

2:00

and rotated and projected Palmer Lee from the radius.

2:05

These injuries occur along these carpal arcs, which is known

2:08

as the zones and vulnerability.

2:10

So the zones encompass the area around the lunate,

2:13

the region of the proximal carpal row,

2:16

and then the mid carpal row,

2:17

and then can also involve fractures

2:20

through the scaphoid 'cause.

2:22

The scaphoid is a bone that traverses both the proximal

2:25

and distal carpal rows.

2:28

And compare that to this example here,

2:31

distal radius and ulnar are intact.

2:33

We've lost the carpal arcs on the frontal projection.

2:36

If we go to our lateral projection,

2:39

can identify the distal radius here,

2:42

the lunate and the capitate.

2:44

However, the scaphoid has an abnormal position

2:48

going back to the frontal.

2:49

Rather than having a fracture,

2:51

we actually have a ligament disruption.

2:54

So there's widening of the SFA Luna interval,

2:56

and in this case, it represents a sca FFA

2:58

Lunate ligament disruption,

3:01

which is now distorting the carpal arcs.

3:03

And because the scaphoid resides in both the proximal

3:06

and distal carpal rows,

3:08

once it's disconnected from the proximal carpal row,

3:11

it prefers to have a resting position that's more palmar.

3:14

And so now it has this abnormal angulation

3:16

where it's more transverse compared to the carpus.