To determine the interobserver agreement of the Eaton-Littler classification system for radiological osteoarthritis of the first carpometacarpal (CMC1) joint and the interobserver agreement of the most appropriate treatment modality.
Forty cases of CMC1 osteoarthritis were independently presented to 5 musculoskeletal-experienced radiologists and 8 hand surgeons. These observers were asked to stage the radiographs according to Eaton and Littler's classification system (stages I-IV). The hand surgeons were also asked to choose their treatment of choice (1, conservative; 2, ligament reconstruction or extension osteotomy; 3, hemitrapeziectomy with interposition; 4, arthrodesis; 5, trapeziectomy; 6, hemiarthroplasty or total arthroplasty).
The overall mean interobserver agreement of the radiological classification was in the moderate range of agreement. The hand surgeons' mean interobserver agreement was just slightly better than the radiologists' mean. The mean interobserver agreement of treatment indicated fair strength of agreement.
The moderate interobserver agreement of the radiological classification of Eaton and Littler for staging of CMC1 osteoarthritis questions the efficiency of Eaton and Littler's classification system. The interobserver agreement in choice of treatment shows a fair agreement. These varieties in classification and in choice of treatment indicate the need for evidence-based research to define optimal classification and treatment of CMC1 osteoarthritis.