CATEGORIZATION OF ACROMIAL SHAPE - INTEROBSERVER VARIABILITY WITH MR-IMAGING AND CONVENTIONAL RADIOGRAPHY

OBJECTIVE. Our purpose was to determine interobserver variability in t he interpretation of the shape of the acromion on sagittal oblique MR images and conventional radiographs. The shape of the acromion was def ined according to a previously described classification scheme. MATERI ALS AND METHODS. We reviewed 26 sets of sagittal oblique MR images and corresponding conventional Y- or outlet-view radiographs of the shoul der. The shape of the acromion was graded for each study independently by four reviewers. Interobserver agreement was measured by using the kappa statistic. Analysis of variance and the chi(2)-test were used fo r univariate analysis. RESULTS. The acromion was interpreted most ofte n as being curved. The observers scored 9% of MR images and 28% of con ventional radiographs as nondiagnostic (p <.001) (41% of transscapular Y views and 3% of supraspinatus outlet views were also considered non diagnostic [p <.0001]). Kappa values were .23 for MR images and .43 fo r conventional radiographs. Variability in interpretation between tech niques when controlled for observer was not statistically significant. CONCLUSION. Although sagittal oblique MR images were significantly mo re likely than conventional radiographs to be considered diagnostic by observers, interobserver agreement for MR examinations was poor. Ther e was moderate agreement with conventional radiographs. This calls int o question the usefulness of the previous system of interpretation and suggests that it might be more applicable with conventional radiograp hs than with MR images.