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So we're ready to begin our discussion

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of the carpal instability classification by the Mayo system.

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We're gonna deal first with carpal instability dissociative.

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This is called Sid, CID.

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The definition derangement within a between bones

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of the same carpal row.

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I'm gonna concentrate only on the proximal carpal row,

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but the distal carpal row can be involved in a variety

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of axial carpal dislocations.

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With regard to the proximal carpal row,

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there are four patterns that I've listed them here.

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We're gonna go through each of these four.

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Let's start with scapholunate dissociation.

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This is a common instability pattern,

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perhaps the most common sca O lunate ligament disruption.

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The initial, uh,

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morphologic step results from hyperextension

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and ulnar deviation.

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So let's look at, at this as we go through it.

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Let me show you. The patient now

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is in fact hitting the ground.

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You can see that the scaphoid has ligament attachment

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to the distal carpal row

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and the lunate is attached to the radius.

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So those ligaments are gonna be vulnerable.

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Let's continue the injury.

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So there's more dorsiflexion that's going on here,

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right extension.

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All right. Uh, and you can see the beginning of failure,

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failure of the scap lunate interosseous ligament

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become begins vol.

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You can see that in that portion.

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And then as we go further, the central portion

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of the scapholunate interosseous ligament is involved

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and eventually the dorsal portion is involved.

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So that scapholunate ligament disruption.

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Now over a period of time, static carpal collapse may occur

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with lar flexion, okay, of the scaphoid

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and dorsal tilting of the lunate.

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So we now have a DC deformity

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and the scapholunate interosseous space is widen.

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To show you an example here,

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these are old gradient echo images,

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but you can appreciate here the arrow is showing you

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disruption of all components

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of the scap O lunate interosseous ligament with widening.

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There were other ligaments involved.

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We'll be talking about it.

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There's a dorsal tilt

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of the lunate on your right in the sagittal plane,

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and this was an acute problem.

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And you can see that there is edema involving the bola

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aspect of the lunate.

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The fourth stage that may occur over time is

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progressive failure of secondary stabilizers.

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That will lead to carpal mal alignment.

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And you can see these various stages here.

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These are pictures taken from Garcia Elias on YouTube.

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So here there's slight widening.

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Now the capitate is migrating proximally.

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The degree of widening is getting more,

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and eventually it may even contact the radius.

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The fifth stage is called rotary

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subluxation of the skateboard.

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The next step and what occurs now is the distal pole

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of the scaphoid flexes even more significantly in

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a vola direction.

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So when you get a radiograph, you are seeing a lot of

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that tilted distal portion.

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It appears as a ring on a pa radiograph of the wrist.

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This is known as the ring sign.

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And then finally, in the final pa, uh, pathway

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of this particular scapholunate problem, you can end up

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with scapholunate advanced collapse.

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It's a, a consequence of chronic scape lunate dissociation.

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The arthropathy is distinctive narrowing

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between the radius and the scaphoid.

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You can see it on plain film

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and Mr deepening of the scaphoid fossa,

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a more prominent ridge between that fossa

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and the lunate fossa narrowing between the lunate

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and capitate, and often abnormal tilting of the lunate

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and severe, uh, disease

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in the mid carpal joint.

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So if we put those stages together using this number stage

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one, a cult meaning in fact that this is

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by mainly by symptoms

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and signs that the orthopedic surgeon will suggest there may

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be scapholunate dissociation.

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The ligament abnormality at that stage is a partial pair

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of the scapholunate ligament.

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The next is dynamic, which means, in fact,

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during stress testing, the orthopedic surgeon will suspect

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that there is a problem.

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This often relates to partial

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or complete tears of the scapholunate in osseous ligament.

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The third stage is scapholunate dissociation.

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And what must occur there to get widening

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between the scaphoid

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and lunate is not only should the scapholunate ligament be

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torn, but there are vola

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and dorsal extrinsic ligaments that are likely torn.

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And then finally, stage four DC stage five slack.

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More extensive injuries of the extrinsic ligaments.

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So let me just show you a few examples.

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These are taken from a web clinic we did

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about three years ago.

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So if anyone's interested, they could look at that.

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They were very nice. Uh, images.

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This is stage three SCA lunate dissociation.

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We see disruption of all portions of the scapholunate

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interosseous ligament.

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It's shown in blue.

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There's altered signal in the dorsal intercarpal ligament.

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It's shown by the

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Green arrow, an intact DCSS.

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Okay, shown by the orange arrow here,

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an abnormal interosseous space, okay, shown

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by the red asterisk

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and dorsal tilting of the lunate shown by the yellow arrow.

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So this is stage three scapholunate dissociation.

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This is stage four DC here.

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The abnormalities include tearing of all portions

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of the scapholunate interosseous ligament shown

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by the blue arrows, a torn DCSF,

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beautifully shown here by the orange triangle.

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The DIC is also injured.

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You can see that where the green arrow is an abnormal

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interosseous space.

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That's the red arrow.

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And dorsal tilting of the lunate is the yellow arrow.

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So this is stage four DC

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and this is the final stage slack, same abnormality

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as stage four, including the widen scape, illuminate

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interosseous space, uh, narrowing

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of the radio scaphoid portion

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of the radiocarpal compartment.

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And note now mal alignment between that proximal pole

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of the scaphoid and the radius

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because the scaphoid has migrated dorsally

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in terms of how they treat these with the first stages, one,

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two, and three, ligament repair, ligament reconstruction,

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there's a variety of procedures with regard

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to stages four and five, and sometimes stage three as well.

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A variety of salvage procedures are used. I.