![]() ![]() It is also a common cause of shoulder pain in athletes whose sports involve throwing and overhead motions. The mean age of onset of this complication is in the sixth decade (age 50 to 59), and it is more frequent in diabetic patients. Image: Overview of the rotator cuff muscles - sagittal view Epidemiology/Etiology The supraspinatus enthesis is a highly specialised in homogeneous structure that is subjected to both tensile and compressive forces. ![]() This effective bone-tendon attachment is achieved through a functional grading in mineral content and collagen fibre orientation. The fourth zone is bone and is largely type I collagen with a high mineral content. The third zone is mineralised fibrocartilage and consists of type II collagen, with significant amounts of type X collagen and aggrecan. The second zone is fibrocartilage and consists of largely types II and III collagen, with small amounts of types I, IX and X collagen. The first zone is proper tendon, made up of largely type I collagen and small amounts of decorin. The anatomy of the supraspinatus’ insertion is of key relevance in terms of its extracellular matrix composition and has been categorised into four transition zones. Collagen is the major matrix protein of supraspinatus tendons, consisting of > 95% type I collagen, with lesser amounts of other collagens including collagen type III. The supraspinatus and infraspinatus tendons fuse 1.5 cm proximal to their insertions. Īn anatomic dissection study of the supraspinatus footprint found that the mean anterior to posterior dimension of the supraspinatus tendon was 25 mm, with a mean medial to lateral thickness of the footprint of 12 mm - the mean distance from the cartilage to the supraspinatus footprint was 1.5 mm at mid tendon. The anterior portion of the supraspinatus is composed of a long and thick tendinous component whereas the posterior portion has been shown to be short and thin. ![]() The posterior margin of the supraspinatus is marked by the extension of the raphe between supraspinatus and infraspinatus around the scapular spine. The anterior margin of the supraspinatus is defined by the posterior edge of the rotator interval that separates the supraspinatus from the rolled superior border of the subscapularis. ![]()
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