| Objectives: There are many ways to promote tendon-bone healing after the repair of the rotator cuff injury.In this experiment,simvastatin / methylcellulose gel was applied locally to the rabbit rotator cuff injury model.To study the effect of local application of simvastatin / methylcellulose gel on tendon-bone healing after repair of rotator cuff injury in rabbits,the biomechanical and histological staining results of the tendon-bone interface were tested after the operation.Methods: The first part:24 adult male New Zealand white rabbits were selected and the rabbit rotator cuff injury model was established after a period of observation.The rabbits were randomly divided into the experimental group(n=12)and the control group(n=12).One week after the modeling,the second operation was performed.In the experimental group,the simvastatin / methylcellulose gel was injected into the bone trough of the large tuberosity of the humerus and the supraspinatus was sutured back to the foot print area.In the control group,the methylcellulose gel was only injected into the bone trough of the large tuberosity of the humerus and the supraspinatus was sutured back to the foot print area.Gentamicin(3 mg / kg)was injected for 3 days after the operation without immobilization.To investigate the tendon-bone healing of supraspinatus,all rabbits were killed at 2,4 and 8 weeks after operation and subjected to general observation、HE staining、Toluidine blue staining and VEGF immunohistochemical staining.The second part:54 adult male New Zealand white rabbits were randomly divided into experimental group,experimental control group and blank control group,with 18 rats in each group.In the experimental group,the simvastatin / methylcellulose gel was injected into the bone trough of the large tuberosity of the humerus and subjected to tendon-bone suturing.The experimental control group was injected with methylcellulose gel and subjected to tendon-bone suturing.The blank control group was given no intervention and subjected to tendon-bone suturing.All rabbits were sacrificed at 4,8 and 12 weeks after surgery for biomechanical testing.Results: The first part:The gross observation showed that all rabbits survived and the incision healed well after surgery.There was no exudate、infection and the adverse reaction of simvastatin.At 2 weeks in the experimental group,inflammatory reaction and granulation tissue hyperplasia were observed in some experimental groups at the tendon-bone interface.The control group had poor healing of tendon-bone interfaces and severe tissue adhesion.The histological examination at 2 weeks in the experimental group revealed that a large number of new capillaries can be seen at the tendon-bone interface.In week 4,the proliferation of cartilage cells at the tendon-bone interface were observed in the experimental group.In week 8,the structure of "Tide line" and dense Sharpey fiber were observed in the experimental group.In week 2,the tendon-bone interface was combined loosely and the proliferation of spindle forming fibroblasts can be seen in the control group.In week 4,we have found no cartilage cells in the control group.In week 8,the loose and disordered Sharpey fibers were observed in the control group.Toluidine blue staining showed that there were some fibroblasts at the tendon-bone interface in the experimental group at 2 weeks.A large number of chondrocytes were seen in 4 weeks,and the "tidal line" structure appeared in 8 weeks.In the control group,the tendon and bone were loosely bonded for 2 weeks,and at 4 weeks,there were fewer new chondrocytes.At 8 weeks,some new bone cells and chondrocytes were seen.Immunohistochemical staining showed that the expression of VEGF positive cells in the experimental group was significantly higher than that in the control group at 2 weeks after operation.At 4 and 8 weeks after operation,the expression of VEGF at the tendon-bone interface tended to decrease.VEGF statistical results showed that the VEGF expression of the tendon-bone interface in the experimental group was higher than that of the control group at 2 weeks after the operation(P < 0.05),and there was no difference in the VEGF expression of the tendon-bone interface between the experimental group and the control group at 4 and 8 weeks after the operation(P > 0.05).The second part: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 difference was statistically significant(P < 0.05).There was no difference in the maximum load and stiffness of the tendon-bone interface between every two groups at 4 weeks after the operation(P > 0.05).The maximum load and stiffness of the tendon-bone interface in the experimental group were significantly higher than that of the remaining two groups at 8 and 12 weeks after the operation.The difference was statistically significant(P < 0.05).There was no difference between the experimental control group and the blank control group(P > 0.05).Conclusions: Simvastatin can enhances the biomechanical strength of tendon-bone interface after acute rotator cuff injury operation in rabbits and promotes tendon-bone healing. |
