Histologic evidence of degeneration at the insertion of 3 rotator cuff tendons: A comparative study with human cadaveric shoulders

We determined on histologic examination the degree of degeneration at the i nsertion of 3 rotator cuff tendons in 76 cadaveric shoulders, 17 of which h ad a partial tear of the supraspinatus. Fiber thinning, the presence of gra nulation tissue, and incomplete tearing of fibers, all evidence of degenera tion, were quantified separately for each tendon. Among the shoulders that were intact on macroscopy, no significant difference in degeneration score could be found. in all 3 tendons degeneration was more prominent on the art icular sides compared with the bursal sides (P < .0001). The degeneration s core of partially torn supraspinatus was significantly higher than that of the intact tendons (P < .0001). The extent of granulation tissue, 1 criteri on of degeneration, seemed to contribute mostly to this difference, intrins ic degeneration occurred foremost in the articular side of the rotator cuff and might constitute the primary cause of rotator cuff tearing.