A cadaver model to evaluate the accuracy and reproducibility of plain radiograph step and gap measurements for intra-articular fracture of the distal radius.

Purpose: The purpose of this study was to determine the accuracy and reproducibility of intra-articular step-off and gap displacements measured on plain radiographs using a standard cadaver model.

Methods: Twenty-two physicians, in a blinded randomized fashion using a standard technique, examined the radiographs of 12 unique combinations of step and gap displacement created by a 3-part intra-articular osteotomy of the distal radius. Observer accuracy, inter- and intraobserver agreement, and tolerance limits were calculated.

Results: The results of this study suggest that observers, independent of skill level, may measure step-off and gap displacements accurately to within .62 +/- .53 mm (95% confidence interval = .59-65). The accuracy of measurement was influenced by the quality of the radiograph. Intraclass correlation coefficient scores showed "substantial" (.78) to "almost perfect" (.81) inter- and intraobserver agreement.

Conclusions: These data can aid in the interpretation of clinical studies of acute distal radius fractures that are based on plain radiography.