Overview
- Motion sparing salvage for SLAC and SNAC wrist arthritis
- PRC removes scaphoid, lunate and triquetrum, so the capitate sits in the lunate fossa
- PRC is simpler with no union needed, but needs healthy capitate and lunate fossa cartilage
- Four-corner fusion excises the scaphoid and fuses lunate, capitate, hamate and triquetrum
- Four-corner fusion preferred when the capitate is worn
- Both keep about half to two thirds of motion, with similar grip and pain relief
Pathology
- Radiolunate joint spared as the lunate articulates concentrically with its fossa
- Radioscaphoid joint degenerates from abnormal scaphoid loading
Classification
SLAC (Watson)
| Stage | Arthritis |
|---|---|
| I | Radial styloid and scaphoid |
| II | Entire radioscaphoid joint |
| III | Capitolunate joint |
| IV | Pancarpal arthritis including the radiolunate joint |
Original publication Watson HK, Ballet FL. The SLAC wrist: scapholunate advanced collapse pattern of degenerative arthritis. J Hand Surg Am. 1984;9(3):358-65.
SNAC
| Stage | Arthritis |
|---|---|
| I | Radial styloid and distal scaphoid fragment |
| II | Scaphocapitate joint |
| III | Capitolunate joint, with the proximal pole articulation usually preserved |
Original publication Vender MI, Watson HK, Wiener BD, Black DM. Degenerative change in symptomatic scaphoid nonunion. J Hand Surg Am. 1987;12(4):514-9.
Management
- Both need a preserved lunate fossa, SLAC IV needs total wrist fusion or arthroplasty
- PRC needs healthy capitate head cartilage and suits SLAC II and SNAC II
- PRC is less predictable in young patients and heavy manual workers
- 4CF suits stage II and III, even with a degenerate capitate
- PRC preserves the volar radioscaphocapitate ligament to prevent ulnar translation
- 4CF fuses lunate, capitate, hamate and triquetrum after scaphoid excision
- Correct lunate DISI to neutral radiolunate alignment before fixation, or dorsal impingement follows
Prognosis
- Pain relief broadly similar
- PRC gives slightly better motion, 4CF slightly better grip
- Radiocapitate arthritis after PRC correlates poorly with symptoms
- Total wrist fusion is the salvage for both
Complications
- PRC, ulnar translation and weakness
- 4CF, non-union, more often with some circular plates
- 4CF, dorsal impingement and hardware prominence
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.