[Pathological study of the supraspinatus tendon].

To clarify the aging process and pathogenesis of rotator cuff tears, left supraspinatus tendons from 268 cadaveric specimens (171 men and 97 women, ages 0 to 87 years) were studied. The incidence of complete thickness tear was 6.7%, and that of incomplete thickness tear was 13.8% (bursal side tears: 2.6%, intratendinous tears: 7.5% and joint side tears: 3.7%). Microscopic examinations were conducted topographically in five sites near the supraspinatus insertion. In the articular side of the tendon, there were fewer tenocytes, fewer arterioles and more chondrocyte like cells than in any other portions. The incidence of hyperplasia of intima was higher in the specimens of aged persons in all portions. At the insertion in the aged specimens the arrangement of four transitional zones became much more irregular and the numbers of tidemark was occasionally increased with granulomatous tissue. The pathogenesis of the rotator cuff tear can be ascribed to the combination of aging, enthesopathy, inherent property of the supraspinatus tendon, injury and subacromial impingement.