Radiographic optimization of the Eaton classification.

Thumb basal arthritis is evaluated using the Eaton classification. However, the shape and orientation of the trapezium do not allow easy visualization of this bone. The purpose of this study was to determine if the intra- and interobserver reliability of the Eaton classification could be improved using a combination of X-rays. Six hand surgeons independently evaluated 40 sets of X-rays. First, the X-rays were staged using the posterior-anterior and lateral views of the wrist, and then using just the Bett's (Gedda's) view. Subsequently, all three views were evaluated together. The process was repeated at least 1 week later. Intra- and interobserver reliability was measured using kappa statistics. Results show a trend toward increased reliability when the three views are used. Agreement between the stages using the posterior-anterior and lateral X-rays and the Bett's view was only fair. With three views, intraobserver reproducibility is good while interobserver reliability is moderate.