[Functional adaptation processes of gliding tendons].

Structure and blood supply of the inserting tendons of supraspinatus and biceps brachii as well as the biceps brachii long head tendon are analyzed in respect of tendon rupture. Due to their course the three tendons investigated are gliding tendons. The part of the tendon adjacent to the pulley consists of fibrocartilage, the part looking away from the pulley having the structure of a traction tendon. The occurrence of fibrocartilage inside the investigated tendons is physiological and not a pathological finding. Development of fibrocartilage is a functional adaptation to pressure and shearing forces acting on the tendon at the pulley. In the investigated samples injection techniques and immunohistochemical methods show an avascular area in the part of the tendon that is adjacent to the pulley. The size of this area is identical with the fibrocartilage. The avascular zone in gliding tendons is due to structure, fibrocartilage is usually avascular. Localisation of rupture and fibrocartilage is nearly identical in the investigated tendons. Unphysiologically increased tensile stress which is inadequate for gliding tendons and occurs in certain kinds of sport may be responsible for the development of ruptures of the tendons of supraspinatus and biceps brachii.