Volume changes of supraspinatus and infraspinatus muscles after supraspinatus tendon repair: a magnetic resonance imaging study.

Muscle volume was measured, by use of magnetic resonance imaging (MRI), as a direct indicator of functional recovery of the supraspinatus and infraspinatus muscles after supraspinatus tendon repair, because atrophy of the supraspinatus and infraspinatus muscles was observed in all patients with a torn supraspinatus tendon. Seventy-three patients who had a cuff tear limited only to the supraspinatus tendon were included in this study. The University of California, Los Angeles score improved significantly after surgery. MRI was carried out before surgery and 6, 12, and 24 months postoperatively in all patients. Muscle volume of the supraspinatus was assessed on images of the oblique coronal plane, and that of the infraspinatus was assessed on images of the axial plane. The width of the supraspinatus muscle did not recover until 6 months postoperatively. Direct measurement of the infraspinatus muscle volume by use of MRI can be a good indicator when evaluating whether the repaired rotator cuffs are actually functioning.