THE COLLAGEN TYPES IN THE ATTACHMENT ZONE OF ROTATOR CUFF TENDONS IN THE ELDERLY - AN IMMUNOHISTOCHEMICAL STUDY

Objective. The attachment zone of the rotator cuff tendons in the elde rly was studied immunohistochemically in order to determine how degene rative changes affected the pattern of collagen fiber distribution. Me thods. Twenty-seven cuffs with their bony insertion were obtained from 22 postmortem cases of both sexes ranging in age from 52 to 90 years and without a history of shoulder ailments. In addition, 3 cuff specim ens from cadavers in the 3rd and 4th decades were examined for compari son. Sections of formalin fixed tissues were stained by peroxidase ant iperoxidase (PAP) technique using monoclonal antibodies against types I, II and III collagen. Results. Degenerative changes affecting the fi brocartilage primarily were characterized by calcification, fibrovascu lar proliferation and microtears. In addition, they were found in all the cuff tendons of elderly individuals but not in those from younger subjects. Immunohistochemically, the attachment zone in areas without degenerative lesions showed collagen type I labelling strongly in bone but only moderately in the fibrocartilage. The predominant labelling in the fibrocartilage was for collagen type II, and collagen type III labelled principally in perichondrocytic areas. The tidemark showed in consistent labelling for any of the collagen types. In the presence of degenerative lesions, the disposition of fiber types was interrupted by calcification and microtears. Collagen type II composition of the f ibrocartilage was markedly altered by the presence of fibrovascular ti ssue which labelled only for collagen type III. Conclusion. We conclud e that severe degenerative changes in the cuff tendons of elderly indi viduals, alter the collagen characteristic of the rotator cuff and tha t the changes could be associated with impairment of biomechanical pro perties of the attachment zone, and may give rise to the clinical synd rome of enthesopathy.