[Purpose] We investigated changes in the supraspinatus muscle with a rotator cuff tear by dissecting the shoulders in cadavers.
[Materials and Methods] We dissected the 76 shoulders in 38 cadavers to study changes of the supraspinatus muscle with cuff tear and advancing in age. We made the transverse section of the supraspinatus muscle and stained by van Gieson method. Then we analyzed changes of the supraspinayus muscle belly with cuff tear and by age, measuring the short and long diameter of a slice of the muscle belly and the area of tendon fiber.
[Results] In the group with normal cuff, there was a negative correlation between aging and the short diameter of the slice of the supraspinatus muscle but no significant correlation between aging and the long diameter of the slice. In the group with a cuff tear, not only the short diameter but also the long diameter of the slice of the supraspinatus muscle decreased with increase in the length of cuff defect. The area of tendon in the slice was increased with the length of cuff defect.
[Conclusions] We concluded that measuring the long diameter of the slice of the supraspinatus muscle was more efficient than measuring the short diameter to evaluate the suprapinatus muscle atrophy with a rotator cuff tear.
