ESTIMATION OF TOTAL COLLAGEN AND TYPE-I AND TYPE-III COLLAGEN IN CANINE ROTATOR CUFF TENDONS

The collagen composition of the supraspinatus, infraspinatus, and subs capularis tendons, which form part of the rotator cuff of the shoulder , was determined. Tendons were obtained from adult, male beagle dogs a nd total collagen was estimated by measurement of hydroxyproline. Ther e was little variation in collagen content among the three major cuff tendons and the quantity approximated that cited in the literature for other tendons. However, the collagen content in the insertion zone of the supraspinatus tendon was significantly higher than in the tendon proper. NaCl fractionation of supraspinatus collagen indicated that ty pe I was the predominant collagen but significant amounts of type III and possibly some type II and type V were also present. Interestingly, there appeared to be more type III collagen in the insertion zone tha n in the tendon proper, cyanogen bromide digestion and peptide mapping confirmed this finding. The differential collagen composition of the supraspinatus tendon may contribute to the high incidence of tear that is associated with this rotator cuff tendon.