In 200 shoulders from cadavera, we studied the pathological changes on
the undersurface of the acromion as associated with tears of the rotator
cuff. After radiographic and histological analysis, we found that in the
specimens that had a partial tear of the cuff the undersurface of the
acromion was almost intact. Although a lesion in the anterior one-third of
the undersurface of the acromion was always associated with a tear of the
cuff, the reverse was not true. We concluded that the pathogenesis of most
of the tears probably is a degenerative process.