Reliability of the grading system for fatty degeneration of rotator cuff muscles.

UNLABELLED: Fatty degeneration of the rotator cuff muscles is considered one of the most important factors for the outcomes of cuff repair. However, the reliability of the grading system is not well validated. Two specialists in musculoskeletal radiology and three shoulder fellowship-trained orthopaedic surgeons reviewed the fatty degeneration grades of each cuff muscle of consecutive 75 full-thickness cuff tears. Fatty degeneration grades were assessed according to the systems of Goutallier et al. and Fuchs et al. using preoperative MR and postoperative CT arthrographies. The interclass correlation coefficient was analyzed to assess interobserver and intraobserver reliabilities. For interobserver reliability using the system of Goutallier et al. the interclass correlation coefficient was higher in MR arthrography (0.6-0.72) than in CT arthrography (0.43-0.6) and higher for radiologists (0.58-0.78) than for orthopaedic surgeons (0.32-0.68). There was no difference between the systems of Goutallier et al. and Fuchs et al. Intraobserver reliabilities showed a similar pattern (0.26-0.81), but the level of experience should be considered. Although the system of Goutallier et al. is most widely used in orthopaedics, reported data should be interpreted carefully because of the relatively low reliability. LEVEL OF EVIDENCE: Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.