We evaluated postoperative recovery of muscle atrophy in shoulders with rotator cuff tears using MRI. Ten shoulders of 10 patients (avg age 54yrs) were examined. There were 6 full-thickness tears of the supraspinatus and infraspinatus and 4 partial-thickness tears of the supraspinatus. TI-weighted images in sagittal oblique plane at a level 1 cm proximal to the glenoid were used for the measurement of cross-sectional area of the cuff muscles. The cross-sectional area of each muscle was measured using NIH image and normalized by the area of the humeral head. The measurements before and one year after the operation were compared. All cuff muscles showed recovery one year after the operation: 38%±21%(mean±SD)increase in the supraspinatus, 5%±3%in the infraspinatus, 6%±4%in the subscapularis. The degree of recovery was less in full-thickness tears than in partial-thickness tears and less in large tears then in small tears. From these results, we recommend that tears be repaired before muscle atrophy advances too much.
