The Optimum Tensile Strength in Rotator Cuff Repair in Rats

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We performed this experimental study to clarify the optimum t ensile strength in rotator cuff repair. We used 160 SD rats/320 shoulders. On the right side, 2 mm of supraspinatus tendon defect was created, opposite side was sham operated as control. Rotator Cuffs were repaired 8 categories of initial tensile strength (0g, 50g, 100g, 150g, 200g, 250g, and 300g).Specimens were obtained, 3 days, 1 week, 3 weeks, and 6weeks after the operation. Muscle volume of the supraspinatus, minor axis of muscle fibers, cell number in collagen fiber, configuration of collagen fiber were measured histologically, and maximum load, cross sectional area of the time, and maximum stress were assessed biomechanically.The volume of supraspinatus decreased postoperatively. Significant difference was not fount between repaired groups and controls. Initial tensile strength in cuff repair was not influent to the Amyotrophy of supraspinatus. Increase of round cell in collagen fiber was observed and collagen fiber was disheveled in comparison with a group of control where the supraspinatus tendon retouched. In cases that initial tensile strength was small, disorder of collagen fiber was large at 3 weeks postoperatively. However thes e no difference as compared with controls 6 weeks after the repair. The capillary neogenesis revealed no difference compared with control. Maximal loads at the sixth week were largest in 200g group. Maximum load of this group was significant greater than 0g, 50g groups.In conclusion, existence of optimum tension in rotator cuff repair was suggested. In the present experiment, 200g neighborhood can be said to be optimal tension.