Background: Muscle atrophy and fatty degeneration of the rotator cuff muscles has been reported as a negative predictor after rotator cuff repair. However, reliable and reproducible methods of evaluating these pathologic conditions are not established yet. Although the Y-shaped view is widely used for measuring cross-sectional areas (CSA) of the supraspinatus muscle, we have to consider the contribution of retraction of the torn tendon as well as muscle atrophy. The purpose of this study was to clarify the relationship between CSA and tendon retraction or size of the tear.
Methods: This study included ninety-five shoulders which were evaluated for the presence and size of tears arthroscopically. There were 16 shoulders with impingement syndrome, 15 small tears, 32 medium tears, 17 large tears, and 15 massive tears. CSA of supraspinatus muscle was measured on from the Y-shaped view to two more medial slices. The retraction of torn tendon was also measured on the oblique coronal images.
Results: On the Y-shaped view, CSA of supraspinatus decreased in conjunction with the increase in tear size. Significant decrease in CSA was only noted in large and massive tears on more medial slices from the Y-shaped view. A negative correlation was found between tendon retraction and CSA, which was strongest on the Y-shaped view.
Conclusion: To prevent an influence of retraction of supraspinatus tendon, sufficiently medial slices from the musculotendinus junction should be used for evaluation of muscle atrophy.