HISTOLOGICAL AND BIOMECHANICAL OBSERVATIONS OF THE RABBIT PATELLAR TENDON AFTER REMOVAL OF ITS CENTRAL ONE-3RD

Using 35 Japanese white rabbits, a study was made of tissue regenerati on and the mechanical properties of the patellar tendon after removal of its central one-third, After removal of the central one-third of th e patellar tendon on one side, in experiment 1 the strength of the ent ire patellar tendon including the regenerated tissue was compared with that of the patellar tendon on the opposite side with the central one -third removed at the time of killing, and in experiment 2 the strengt h of only the regenerated tissue was compared with that of the patella r tendon on the opposite side with two-thirds of the medial and latera l sides removed at the time of death. In experiment 1, the maximum loa d showed no significant difference between the operated side and the c ontrol. In one-half of the cases, the strength of the operated side in cluding the regenerated tissue was weak, suggesting weakening of the p atellar tendon on the residual bilateral sides. In experiment 2, the m aximum load of the regenerated tissue was significantly lower than tha t of the control, the former being 25% of the latter even at 6 months. Histologically, the characteristics of the cells and collagen fibers gradually approached those of normal tissue, but the crimp pattern of the collagen fibers and fibrils was evidently smaller than that of the control. These results indicate that regenerated tissue was still mec hanically weak and immature at 6 months.