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21-year-old man who fell with wrist pain.

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Simple search pattern involving the

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skeleton demonstrates a wide gap between

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the scaphoid and the lunate immediately.

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There's no secret that this patient

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has scapholunate dissociation.

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But there's more.

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There is hypertrophy of the radial styloid due

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to arthritis of the distal pole of the scaphoid

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as it rubs abnormally against the distal radial

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styloid, causing its hypertrophic response.

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This is one of the earliest signs of scapholunate

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advanced collapse, or slack wrist.

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In fact, it's considered stage one.

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There's a little inflammatory reaction around it.

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Slack wrist, by the way, is the most common

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cause of degenerative arthritis of the wrist,

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and Watson and Ballet coined the term in 1984.

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Oh, but there's more.

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We're not done looking simply at the skeleton

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of the wrist in the coronal AP projection.

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What is stage 2 slack wrist?

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In this scenario, stage 2, there is arthritis

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between the entire scaphoid and the radius.

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Now it doesn't have to be every inch of it,

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but let's look at the base of the scaphoid.

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Oh, there's an erosion there.

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There's narrowing of the joint space.

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So the proximal aspect of the joint is involved,

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and the distal aspect of the joint is involved.

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Now, frequently, in slack wrist, you may

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see erosions all the way from proximal to

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distal on the radial side in its fossa.

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That's not the case here.

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But there is involvement of

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more than just the distal pole.

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What would be stage 3 slack wrist?

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We would see narrowing, sclerosis, irregularity,

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and erosions of the capitolunate articulation,

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and we do, right there on the T1-weighted image,

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right there on the water-weighted image, with joint

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space narrowing at the lunate and the capitate.

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And in stage 4, which this patient does

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not manifest, there would be generalized

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degeneration in the intercarpal space,

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and perhaps involvement in the

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remaining radial carpal articulation

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and the radial ulnar articulation,

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which in this case is relatively spared.

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So we have features of stages one, two, and

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three slack wrist that we have demonstrated.

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Now, as said previously, with scapholunate

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dissociation, there is a high risk of

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DISSI, or dorsal intercalary segmental

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instability, which this patient has.

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Although we haven't mentioned it, there

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are four causes or basic types of DISSI.

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It can occur as a result of a scaphoid fracture.

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This is known as bony DISSI.

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Distal radius fracture, compensatory DISSI, radius

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malunion, known as adaptive DISSI, and this type,

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dissociation of the scaphoid and lunate, so-called

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ligamentous DISSI, producing a dorsal-facing lunate.

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And if we look at the angle between the lunate and this

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angle is the long axis of the radius, let's scroll it.

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Actually, we won't scroll it.

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You'll have to take my word for it.

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This is the long axis of the radius.

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Sorry.

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The long axis of the scaphoid.

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This is the perpendicular axis of the lunate.

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And we look at this angle.

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This angle should be less than

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60 degrees. Over 70 degrees,

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it's almost always DISSI.

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And this angle will be markedly decreased in the

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opposite, ventral-facing lunate, so-called VISSI.

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So now, we've highlighted

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the manifestations of slack wrist in a patient

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with scapholunate dissociation and DISSI,

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giving you the four progressive stages of

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slack wrist, originally described in 1984.