The microvascular pattern of the rotator cuff.

Very little investigation has been undertaken into the microvascular bed of the rotator cuff. Lindblom (1939) described areas of relative avascularity in the supraspinatus tendon adjacent to its point of insertion, and a similar zone in the long head of the biceps near its origin from the supraglenoid tubercle. Moseley and Goldie (1963) also noted a zone of diminished vascularity near the insertion of the supraspinatus. They termed this the “critical zone” and they believed that it represented an area of anastomosis between the vessels derived from the bone at the point of insertion and the longitudinally directed vessels arising from the arterioles in the muscle belly. Rothman and Parke (1965) stated that the “critical zone” of relative avascularity was not a pathological state but was associated with advancing age. It is, however, of interest that this zone of relative avascularity of the supraspinatus corresponds to the most common site of breakdown changes in the rotator cuff. It is at this site that rotator cuff tendinitis, calcification and spontaneous ruptures occur. In order to understand the significance of this