SLAC (scapholunate advanced collapse) refers to a specific pattern of osteoarthritis and subluxation which results from untreated chronic scapholunate dissociation or from chronic scaphoid non-union. In the case example, the likely culprit is chronic scaphoid non-union. The pattern of sequential degenerative arthritis of the wrist includes arthritis between the scaphoid, lunate, and radius (57%), arthritis between the scaphoid, trapezium, and trapezoid (27%) and a combination of these two patterns (15%).¹