Summary Scaphoid Lunate Advanced Collapse (SLAC) describes the specific pattern of degenerative arthritis seen in chronic dissociation between the scaphoid and lunate. Diagnosis is made clinically with progressive wrist pain and wrist instability with radiographs showing advanced arthritis of the radiocarpal and midcarpal joints (radiolunate joint spared). Treatment involves observation, NSAIDs and splinting in early stages of disease. A variety of operative procedures may be indicated depending on severity of disease and patient's symptoms. Etiology Pathoanatomy chronic SL ligament injury creates a DISI deformity login to view 3 more bullets resultant scaphoid flexion and lunate extension creates login to view 2 more bullets initially affects the radioscaphoid joint and progresses to capitolunate joint login to view 1 more bullet Classification Watson classification describes predictable progression of degenerative changes from the radial styloid to the entire scaphoid facet and finally to the unstable capitolunate joint, as the capitate subluxates dorsally on the lunate key finding is that the radiolunate joint is spared, unlike other forms of wrist arthritis, since there remains a concentric articulation between the lunate and the spheroid lunate fossa of the distal radius Watson Classification Stage I Arthritis between scaphoid and radial styloid Stage II Arthritis between scaphoid and entire scaphoid facet of the radius Stage III Arthritis between capitate and lunate note: radiolunate joint spared While original Watson classification describes preservation of radiolunate joint in all stages of SLAC wrist, subsequent description by other surgeons of "stage IV" pancarpal arthritis observed in rare cases where radiolunate joint is affected validity of "stage IV" changes in SLAC wrist remains controversial and presence pancarpal arthritis should alert the clinician of a different etiology of wrist arthritis Presentation Symptoms difficulty bearing weight across wrist patients localize pain in region of scapholunate interval progressive weakness of affected hand wrist stiffness Physical exam tenderness directly over scapholunate ligament dorsally decreased wrist ROM weakness of grip strength Watson scaphoid shift test login to view 7 more bullets Imaging Radiographs obtain standard PA and lateral radiographs login to view 9 more bullets stress radiographs unnecessary MRI unnecessary for staging, but will show login to view 2 more bullets Differential SNAC wrist Treatment Nonoperative NSAIDs, wrist splinting, and possible corticosteroid injections login to view 2 more bullets Operative radial styloidectomy login to view 5 more bullets PIN and AIN denervation login to view 5 more bullets proximal row carpectomy login to view 9 more bullets scaphoid excision and four corner fusion login to view 9 more bullets wrist fusion login to view 5 more bullets