RESUMEN
Light and polarization microscopic appraisal of the pathways of fibers and blood vessels in the region of the rotator cuff shows branches of the suprascapular artery. These initially radiate into the insertion tendon parallel to the muscle fibers. They do not continue there, i.e. the vessel branches have blind endings, or they branch and anastomose with each other. Outliers of the transverse branch of the anterior circumflex artery of the humerus come from lateral (from the direction of the deltoid muscle). They pass from the bony insertion of the supraspinatus tendon into the tendon plate, but only run together with the fibers for a short distance. Consequently, a zone low in vessels or free of vessels can be constantly demonstrated under a magnifying glass in the course of the supraspinatus and to a small extent also of the infraspinatus in the fetus or neonate as well as in the adult in the region of the zone of interweaving of the tendinous muscle outlier with the capsule at length magnification. In the genesis of rotator cuff rupture, the presence of hypovascularity must be considered to be a predisposing factor which is present from birth onwards. It affects the clinical course during the process of aging as the point of least resistance in consequence of arteriosclerosis, collagen degeneration physiological wear and tear friction at the lower surface of the acromion and inflammatory swellings of the subacromial bursa.
