Summary Scaphoid Nonunion Advanced Collapse (SNAC) describes the specific pattern of progressive arthritis of the wrist that results from a chronic scaphoid nonunion. Diagnosis is made clinically with progressive wrist pain and wrist instability with radiographs showing scaphoid fracture nonunion with advanced arthritis of the radioscaphoid joint. Treatment involves observation in early stages of disease. A variety of operative procedures may be indicated depending on severity of disease and patient's symptoms. Etiology Pathophysiology pathoanatomy natural history of degenerative changes first occurs at the radioscaphoid area followed by pancarpal / midcarpal arthritis Anatomy Scaphoid anatomy blood supply major blood supply is dorsal carpal branch (branch of the radial artery) enters scaphoid in a nonarticular ridge on the dorsal surface and supplies proximal 80% of scaphoid via retrograde blood flow minor blood supply from superficial palmar arch (branch of volar radial artery) enters distal tubercle and supplies distal 20% of scaphoid motion both intrinsic and extrinsic ligaments attach and surround the scaphoid the scaphoid flexes with wrist flexion and radial deviation and it extends during wrist extension and ulnar deviation (same as proximal row) also see Wrist Ligaments and Biomechanics for more detail Classification Radiographic Classification Stage I Arthrosis localized to the radial side of the scaphoid and radial styloid Stage II Scaphocapitate arthrosis in addition to Stage 1 Stage III Periscaphoid arthrosis (proximal lunate and capitate may be maintained) Presentation Symptoms weakness reduced grip and pinch strength stiffness stiffness with extension and radial deviation Physical exam palpation localized tenderness of the radioscaphoid articulation motion decreased wrist motion on extension and radial deviation Imaging Radiographs recommended view ap and lateral of wrist findings see radiographic classification above Differential SLAC wrist Scaphoid fracture nonunion Treatment Nonoperative observation alone indications medically frail and low functioning patients only Operative radial styloidectomy plus scapholunate reduction and stabilization indications stage I distal pole excision indications stage I proximal row carpectomy indications stage II and III outcomes disadvantages reduction of wrist motion and grip strength procedure should be avoided if there are capitate head degenerative changes four-corner fusion or capitolunate arthrodesis indications stage II and III outcomes retains 60% of wrist motion and 80% of grip strength wrist arthrodesis indications stage II and III Prognosis Patients with scaphoid nonunions of > 5 years duration or proximal pole necrosis have less favorable outcomes Punctate bleeding of bone during surgery is a good prognostic indicator of union 92% union with obvious bleeding, 71% with questionable bleeding, 0% with no bleeding results show decreased rate of arthritis (down to 40-50%)