Modern Study Review (AI-Generated)
High-Yield Summary
Scaphoid Nonunion Advanced Collapse (SNAC) is a progressive wrist arthritis pattern resulting from untreated or malunited scaphoid fractures. It mirrors the natural history of Scapholunate Advanced Collapse (SLAC) wrist but is driven by altered scaphoid anatomy and biomechanics. Early recognition and staging of SNAC are critical to guide treatment aimed at preserving wrist motion and function while minimizing pain. Modern management balances joint preservation with stabilization or salvage procedures depending on the extent of degenerative changes.
Key Diagnostic Findings
| Aspect | Details |
|---|---|
| Anatomy | Scaphoid bone, radioscaphoid joint, scaphocapitate joint, lunocapitate joint, radial styloid |
| Clinical Presentation | Wrist pain, decreased range of motion, weakness, tenderness over radial wrist, history of scaphoid fracture or nonunion |
| Imaging | X-rays: show scaphoid nonunion, sclerosis, collapse, and progressive arthritis; CT/MRI for nonunion and cartilage status |
| Classification (Stages) | Stage I: Arthritis localized to distal scaphoid and radial styloid Stage II: Radioscaphoid + scaphocapitate arthritis; lunocapitate spared Stage III: Periscaphoid arthritis involving radioscaphoid, scaphocapitate, and lunocapitate joints |
Current Gold Standard Treatment
| Stage | Treatment Options | Indications |
|---|---|---|
| Stage I | Radial styloidectomy + bone grafting of scaphoid nonunion | Symptomatic arthritis localized to radial styloid and distal scaphoid; viable proximal scaphoid fragment |
| Stage II | Proximal scaphoid fusion to capitate and lunate with distal scaphoid excision (Viegas technique) or scaphoid excision + four-corner fusion | Radioscaphoid and scaphocapitate arthritis with preserved lunocapitate joint |
| Stage III | Scaphoid excision + four-corner fusion or total wrist arthrodesis | Advanced arthritis involving lunocapitate joint; salvage procedures for pain relief and stability |
– Non-operative management: Reserved for low-demand patients or early stages; includes immobilization, NSAIDs, and activity modification.
- Proximal Row Carpectomy (PRC): Alternative to four-corner fusion in select cases; preserves more motion but may risk arthritis progression.
- Total wrist arthrodesis: Last resort for end-stage arthritis; sacrifices motion for pain relief and strength.
Modern Complications & Outcomes
| Complication/Outcome | Notes |
|---|---|
| Progression of arthritis | Even after union, altered scaphoid anatomy can lead to degenerative changes over time |
| Nonunion persistence | Risk of continued instability and collapse if untreated |
| Postoperative stiffness | Common after fusion or arthrodesis; rehabilitation critical |
| Loss of motion | Four-corner fusion and arthrodesis reduce wrist motion; PRC preserves more motion but less strength |
| Arthritis progression | Possible after PRC and partial fusions; requires long-term monitoring |
| Functional outcomes | PRC offers better motion, less strength; four-corner fusion balances motion and strength; arthrodesis maximizes strength but eliminates motion |
Classic Clinical Notes
SNAC
Scaphoid Nonunion Advanced Collapse – SNAC Wrist
- Similar in natural history to SLAC wrist, with comparable stages of joint degeneration.
- Can occur after malunion or after established nonunion.
- It is felt that degenerative arthritis is almost inevitable after a scaphoid nonunion.
- The fact that this joint degeneration can occur even after healing of the scaphoid fracture emphasizes the precise role that the scaphoid plays in normal wrist kinematics.
- If the scaphoid shape or volume is altered (by malunion, or by nonunion and subsequent bony resorption), the process of degeneration can be initiated.
- Ligamentous injury can also occur with scaphoid fracture and contribute to the pathogenesis of degenerative change.
- With an unstable scaphoid fracture, the distal segment flexes, the proximal fragment extends under the influence of the lunate (if the scapholunate ligament is still intact). Joint congruity between the distal radius and scaphoid and between the scaphoid and capitate is decreased.
Stages
| Stage | Description |
|---|---|
| I | Arthritis localized to the distal scaphoid and radial styloid |
| II | Radioscaphoid plus scaphocapitate arthritis, but preservation of the lunocapitate joint |
| III | Periscaphoid arthritis involving radiostyloid, distal scaphoid, scaphocapitate, and lunocapitate joints |
Surgical Treatment – SNAC Wrist
| Stage | Treatment |
|---|---|
| I | Radial styloid excision plus bone graft of scaphoid nonunion |
| II | Proximal scaphoid fused to capitate and lunate with excision of distal scaphoid (Viegas) Scaphoid excision, four-corner fusion |
| III | Scaphoid excision, four corner fusion Wrist arthrodesis |
– In the end, comparison of results for motion, strength, and functional use does not demonstrate vast differences between any of the procedures.
- In general, proximal row carpectomy provides more motion, a little less strength, and progression of arthritis in some cases.
- Midcarpal fusion with scaphoid excision provides fair-good motion and strength equal to complete fusion, but with some risk of arthritis progression.
- Total wrist arthrodesis provides good strength, but leaves no motion.
Last Updated on January 24, 2026 by orthonet
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