Establishment And Preliminary Study Of Animal Model Of Injury Of Rotator Cuff Tear

Objective:A rabbit model of rotator cuff tear(RCT)was established of rabbit subscapular muscles.On the premise of no surgical treatment,the tendon healing of rotator cuff tendon injury in rabbits from 2 to 8 weeks after injury was observed by biomechanical,histological and MRI studies.Methods:Forty adult male New Zealand white rabbits were randomly numbered.Selection of 4rabbit without any treatment for preliminary preparation and debugging and were not included in the experimental results.The other 36 rabbits operate disruption of the subscapllaris muscles on the right side,established a rotator cuff tears model,and the left with the sham operation.Postoperative activity is not restricted.The healing of rotator cuff tendon was observed by MRI at 2,4,6 and 8 weeks after operation.HE staining was used to observe tendon healing of fat infiltrating muscle,Masson staining was used to observe muscle fiber healing,and biomechanical test was used to check tendon strength.Result:The subscapularis muscle of rabbit has similar anatomical structure and tissue structure to that of human.It is suitable for establishing RCT model.The operative procedure is simple and repeatable.Get rid of four rabbit due to anesthesia.The collagen fibers in the right tendon of the experimental animals were arranged regularly and tightly with a small amount of loose connective tissue after 8 weeks of HE staining and Masson staining,which basically restored the normal fibrous structure.Two weeks after operation,MR imaging showed localized signal enhancement in the injured tendon,irregular tendon structure,poor tendon shape,obvious tendon injury,and signal enhancement in the shoulder joint cavity.At2-6 weeks after operation,the limited enhancement shadow in the injured tendon gradually decreased,and the high signal shadow in the articular cavity gradually decreased.At 8weeks,there was no high signal in tendon,the shape of tendon was smooth,and there was no high signal in articular cavity.The biomechanical results revealed that the maximum load at 2,4 and 6 weeks after operation was(36.49 ±2.59)N,(48.40 ±4.53)N and(71.46 ±2.61)N,respectively,which were significantly lower than those at sham operation side(77.25 ± 2.85)N,(78.66 ± 2.86)N and(79.40 ± 4.60)N,respectively.The difference was statistically significant(P < 0.05).At 8 weeks,the maximum load was(77.12+2.52)N after operation and(79.83+1.83)N at sham-operated side.The difference was not statistically significant(P >0.05).The biomechanical results revealed that the stiffness at 2,4 and 6weeks after operation was(22.14 ± 1.58)N/mm,(28.50 ± 2.67)N/mm and(43.78 ±1.59)N/mm,respectively,which were significantly lower than those at sham operation side(48.18 ± 1.78)N/mm,(49.06 ± 1.78)N/mm and(49.51 ± 2.87)N/mm,respectively.The difference was statistically significant(P < 0.05).At 8 weeks,the stiffness was(48.67±1.64)N/mm after operation and(49.78±1.14)N/mm at sham-operated side.The difference was not statistically significant(P >0.05).Conclusion:At 8 weeks after rotator cuff tendon injury in rabbits,the histological staining showed that the tendon arrangement returned to normal.And there was no statistical difference in the maximum load and stiffness between the injured tendon and the normal tendon strength.The injury signal basically disappeared in imaging,and the rotator cuff tendon injury basically healed in this animal model.The establishment of a model of rotator cuff injury in rabbits' subscapularis muscle can be used to observe the healing of rotator cuff injury under conservative treatment.