| Purposes1.Compare the stability effect of the titanium alloy suture anchor and Ni-Ti memory alloy suture anchor,compare the holding force of the two suture anchors in different proximal humeral bone mineral density models,and explore the biomechanical characteristics of the two suture anchors under normal bone and osteoporosis conditions.2.Use physical polishing and acid etching to change the surface morphology of Ni-Ti alloy.On this basis,introduce chitosan-sodium alginate composite coating and characterize it to explore its effect on osteoblast activity.3.To determine the efficacy of chitosan quaternary ammonium salt-coated modified suture anchor in the treatment of osteoporosis with rotator cuff injury on animal models.Methods1.Biomechanical comparative study of titanium alloy suture anchor and nickel titanium alloy suture anchor:three kinds of rigid polyurethane foam blocks with different densities were used to build the humerus model with normal bone density and osteoporosis.The nickel titanium alloy wire suture anchor and titanium metal wire suture anchor were implanted into the humeral model at 90°angle,and the traction direction of the suture anchor under physiological conditions and the traction direction of the suture anchor during knotting were simulated at 45°and 90°respectively.Carry out continuous pull-out test,and each group shall carry out 8 tests without interruption,and record the maximum failure load.2.Surface modification of nickel-titanium alloy: polish the surface of suture anchor,and use 60 ml of 98% concentrated sulfuric acid and 30% hydrogen peroxide to corrode the surface of suture anchor nail.Chitosan with a degree of substitution of26% was synthesized and the product was detected by Fourier transform infrared spectroscopy.Chitosan-sodium alginate composite coating was introduced into the surface of Ni-Ti alloy by glutaraldehyde crosslinking method and electrostatic layerby-layer self-assembly method.The contact angle of different surfaces was measured and observed by electron microscope,and the effect on osteoblast activity was detected by CCK-8 experiment.3.Evaluation of therapeutic effect of shoulder sleeve repair in osteoporosis rabbits:36 female New Zealand white rabbits at the age of 5 months were selected.Osteoporosis model was established by castration combined with glucocorticoid method,and the model was successfully established by using Micro CT 7 weeks after operation.After successful modeling,an acute injury model of rabbit supraspinatus muscle was established.Titanium alloy suture anchor,nickel-titanium alloy suture anchor and surface-modified nickel-titanium alloy suture anchor were used to repair the injury.Samples were taken at 6 and 12 weeks after operation for overall observation,and the efficacy was evaluated by biomechanics(cross-sectional area of supraspinatus muscle,maximum failure load,stiffness),Micro CT,histology(HE staining).Results1.Biomechanics: The failure load of Ni-Ti memory alloy suture anchor in the direction of 45 ° and 90 ° traction force in the osteoporotic bone model is greater than that of titanium suture anchor(P<0.05).In the normal bone model,there was no statistical difference between the two failure loads.In the normal bone mineral density model and osteoporosis model,the failure load of titanium suture anchor and nickel titanium alloy suture anchor in the 45 ° traction direction was greater than that in the90 ° traction direction(P<0.05).Under the same traction direction,the failure load of titanium suture anchor osteoporotic model was smaller than that of normal bone mineral density model(P<0.05).2.Material characterization:Fourier transform infrared spectroscopy proved that the quaternary ammonium salt of chitosan was synthesized.The electron microscope pictures showed that the surface area of the material increased after acid corrosion.After coating,the surface of the material was filled with quaternary ammonium saltsodium alginate.The contact angle test found that the contact angle after surfacemodification was significantly smaller than that of the unmodified material.CCK-8results showed that mechanical combined chemical modification and composite coating can promote the proliferation of osteoblasts.3.Evaluation of curative effect in rabbit osteoporosis model: Micro CT results showed that castration combined with dexamethasone sodium reduced bone mineral density,surface area volume ratio,bone trabecular thickness,bone trabecular number of proximal humerus,and increased bone trabecular space,with statistical difference(P<0.05).HE staining found that the bone trabeculae of the experimental group were slightly thicker than those of the control group,and the bone trabeculae of the experimental group 2 were thicker than those of the experimental group 1.12 W after operation: the bone trabeculae of the experimental group and the control group were thicker than those of the 6W bone trabeculae,the bone trabeculae of the experimental group were thicker than those of the control group,and the bone trabeculae of the experimental group 2 were thicker than those of the experimental group 1.Biomechanics: The area,maximum tensile strength,and stiffness of the supraspinatus tendon-bone junction in the repair group of each group increased with the passage of time after surgery,but they were all smaller than the contralateral normal group.There was no statistical difference between the area of the tendon-bone junction in the experimental group and the control group at each period.The maximum tensile strength and stiffness were greater than the control group at each period,and the difference was statistically significant.Conclusions1.The dual wing structure design of the nickel titanium memory alloy suture anchor can significantly enhance its maximum failure load under osteoporosis conditions and enhance the initial fixation strength of the shoulder sleeve.2.The combined coating of N-propyl-3-trimethylammonium chloride chitosan and sodium alginate can promote the proliferation of osteoblasts on the suture anchor surface.3.Chitosan quaternary ammonium salt coated nickel titanium alloy suture anchor can increase the number and thickness of bone trabeculae at the greater tubercle of the humerus in osteoporotic rabbits,thereby enhancing the fixation strength of the rotator cuff,increasing the tendon bone healing strength of the rotator cuff,and facilitating the repair of osteoporotic and rotator cuff injuries. |
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