[Purpose] Experimental study has been performed on the repair process of the rotator cuff tear using rabbits or dogs. However, the degeneration of rotator cuff was not concerned in these studies. In this study, it was attempted to make a degenerative tendon using patella tendon of the rat.
[Subjects and Methods] Female Wistar rats (12 weeks after birth) were used. Lateral half of the patella tendon was detached from the tibia. The detached tendon was turned up subcutaneously in right leg (subcutaneous group), and was turned down into the patello-femoral joint in left leg (intra-joint group). At 1,2 and 3 weeks after operation, the patella tendons (N= 4; 1 week, N= 3; 2 weeks, N= 5; 3 weeks) were removed and examined histologically. Numbers of tenocyte was measured by histologic findings and the density of tenocyte was obtained.
[Results] In intra-joint group, wavy appearance disappeared and the collagen fibers were longitudinal splitting at 3 weeks after operation: But, neither hyaline degeneration nor hyperplasia of intima were observed in any tendon. Density of tenocyte in intra-joint group was significantly lower that those in subcutanecus group at 3 weeks after operation.
[Discussion] It is speculated that the degeneration of the patella tendon was caused by insufficiency of blood flow due to detachment and mechanical stress between patella and femur. In This study, all tendons were able to be degenerated in a short period, and this model seems to be useful for experimental study of the rotator cuff tear.
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