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 scaphoid is flexed and lunate is extended as scapholunate ligament no longer restrains this articulation login to view 2 more bullets resultant scaphoid flexion and lunate extension creates abnormal distribution of forces across midcarpal and radiocarpal joints malalignment of concentric joint surfaces initially affects the radioscaphoid joint and progresses to capitolunate joint notably the radiolunate joint is spared 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 patients may have positive Watson scaphoid shift test early in the process, will not be positive in more advanced cases as arthritic changes stabilize the scaphoid technique login to view 4 more bullets Imaging Radiographs obtain standard PA and lateral radiographs PA radiograph will reveal greater than 3mm diastasis between the scaphoid and lunate login to view 6 more bullets lateral radiograph login to view 1 more bullet stress radiographs unnecessary MRI unnecessary for staging, but will show thinning of articular surfaces of the proximal scaphoid scaphoid facet of distal radius and capitatolunate joint with synovitis in radiocarpal and midcarpal joints Differential SNAC wrist Treatment Nonoperative NSAIDs, wrist splinting, and possible corticosteroid injections indications login to view 1 more bullet Operative radial styloidectomy indications login to view 1 more bullet technique login to view 2 more bullets PIN and AIN denervation indications login to view 1 more bullet technique login to view 2 more bullets proximal row carpectomy indications login to view 1 more bullet contraindications login to view 2 more bullets technique login to view 1 more bullet outcomes login to view 1 more bullet scaphoid excision and four corner fusion indications login to view 1 more bullet Contraindications login to view 1 more bullet technique login to view 2 more bullets outcomes login to view 1 more bullet wrist fusion indications login to view 2 more bullets outcomes login to view 1 more bullet