Small And Medium Rotator Cuff Tears Return

Objective:The main purpose of the experiment is to study the histological and biomechanical effects of small and medium-sized rotator cuff injury in rabbits treated by operative treatment and relatively conservative therapy.So it will be helpful to provides experimental basis for the treatment of small and medium-sized injury in clinical rotator cuff.Methods:Supraspinatus tenotomy was performed in the right shoulder of 30 skeletally matured male New Zealand white rabbits to establish the animal model of acute rotator cuff tear.The rabbits were randomly divided into 2 groups:group of surgical repair,repaired at 1 week after tenotomy;and group of conservative treatment,used as control.At 2 weeks,4 weeks and 8 weeks after repair healing of tendon-bone interface was observed by HE staining.The rabbits were sacrificed at 2,4 and 8 weeks postoperatively with 2 rabbits sacrificed each time.Tissue samples of the tendon-bone interface was taken for histological examination and biomechanical test was performed to assess the strength of tendon-bone junction.Results:The gross observation showed that all rabbits survived and the incision healed well after surgery,There was no exudate and infection.Histologic observation and results: 8weeks after repair,the tendon-bone interface was basically formed,which has a typical four-layer shift belt structure."tidal line" is visible and Sharpey fiber is dense,the inflammatory cells were basically absent and a new enthesis of supraspinatus was observed,but the new stop lack of mineralized fiber cartilage.At 8 weeks after modeling,The tendon-bone interface in the conservative group revealed scar healing mainly,and chondrocytes and fibrocartilage that were not observed.Biomechanics research results: The results of biomechanics test showed that the maximum load and stiffness of the tendon-bone interface increased continuously in the three groups with the prolongation of time.The maximum load and stiffness of the tendon-bone interface on the experimental side after conservative treatment weresignificantly lower than that of the control group at 2,4 and 8 weeks after the operation.The difference was statistically significant(P < 0.05).The maximum load and stiffness of the tendon-bone interface on the experimental side in the surgical group were significantly lower than that of the control group at 2 and 4 weeks after the operation.The difference was statistically significant(P < 0.05).The maximum load and stiffness of the tendon-bone interface in the surgical group were significantly higher than that of the control group at 8 weeks after the operation(P > 0.05).The maximum load and stiffness of the tendon-bone interface in the surgical group were significantly higher than conservative group at 2,4 and 8 weeks.The difference was statistically significant(P <0.05).Conclusion:Surgical repair of small and medium-sized rotator cuff tear in rabbits can lead to formation of a new enthesis of supraspinatus and improvement of biomechanical properties of supraspinatus.