Chronic rotator cuff tears often involve muscle atrophy and fatty degeneration. It has been reported that the re-tear rate after surgery is relevant to muscle atrophy and fatty degeneration. The purpose of this study is to demonstrate that muscle atrophy and fatty degeneration are improved by successful repair. 24 patients with massive rotator cuff tear were repaired with Surface-holding repair technique. We investigated spuraspinutus and infraspinatus atrophy judged by occupation ratio (=actual occupied area/anatomical occupied area), fatty degeneration judged by Goutallier's classification and repair integrity judged by Sugaya's classification on MRI. We could find improvement from severe preoperative muscle atrophy and fatty degeneration in well repaired shoulders. On the other hand, when re-tear occurred, muscle atrophy and fatty degeneration got worse. Our results suggested that a successful repair may partially reverse muscle atrophy and fatty degeneration.
