Tips to remember this classification include:
- If the trapezio-metacarpal joint (1st CMCJ) is widened: stage is ≥1
- If the trapezio-metacarpal joint (1st CMCJ) is narrowed: stage is ≥2
- If osteophytes are >2mm: stage is ≥ 3
- If scapho-trapezial joint is narrowed: stage is ≥ 4
| Eaton Stage | Joint | Subluxation | Osteophyte | Surgery |
| I | 1st CMCJ widened | <1/3 | No | Volar Ligament Reconstruction |
| II | 1st CMCJ narrowed | <1/3 | <2 mm | 1. Ligament reconstruction with tendon interposition (LRTI) 2. Single interposition 3. Suspensionplasty 4. Metacarpal osteotomy |
| III | 1st CMCJ severely narrowed | ≥1/3 | >2 mm | Same as above |
| IV | 1st CMCJ obliterated + STT joint narrowed | Major | >2 mm | 1. LRTI 2. Double interposition 3. Suspensionplasty 4. Simple trapeziectomy |
Before proceeding to surgery, non-operative treatment trial includes:
- NSAIDs for 2-3 weeks
- Activity modification
- Splint for 3-6 weeks
- +/- Corticosteroid injection (Second-line)
Further reading: Basal Thumb Osteoarthritis: Anatomy, Pathophysiology, Diagnosis, Treatment