[Definition and classification of basal joint osteoarthritis. A critical analysis and proposals. Treatment options]

Several definitions and classifications of basal joint osteoarthritis exist. Each of them can be criticized. The authors propose to define basal thumb osteoarthritis as osteoarthritis of the trapezometacarpal joint associated or not with lesions of scapho-trapezio-trapezoid and/or metacarpophalangeal joints. The proposed classification is derived from the Eaton-Littler classification. Stage O is identical to stage I of the Eaton-Littler classification: trapeziometacarpal instability without cartilage lesions. Stage I is osteoarthritis of the trapeziometacarpal joint only, without metacarpophalangeal deformity. Stage II is trapeziometacarpal osteoarthrites combined with reductible hyperextension deformity of the metacarpophalangeal joint. Stage III is trapeziometacarpal osteoarthrites combined with irreductible metacarpophalangeal deformity. Stage IV is identical to stage IV of the Eaton-Littler classification: combined trapeziometacarpal and scapho-trapezio-trapezoid osteoarthritis. The advantage of the proposed classification is that basal joint osteoarthritis is not only defined as real or potential (stage O) osteoarthritis of the trapeziometacarpal joint, but also includes precise evaluation of two other joints at the base of the thumb. This classification can be a guide for treatment options.