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Experimental Study On The Treatment Of Chronic Infectious Bone Defects In Rabbits Based SF/VANCO/PLGA/β-TCP

Posted on:2024-07-16Degree:MasterType:Thesis
Country:ChinaCandidate:B XuFull Text:PDF
GTID:2544307082451854Subject:Clinical Medicine·Orthopedics (Professional Degree)
Abstract/Summary:PDF Full Text Request
Objective:In this experiment,we proposed to construct a simple and reliable model of chronic infected bone defects in rabbit tibia,and after a phase I thorough debridement,the scaffold was placed into the animals to study its effects on inhibiting bacterial growth and promoting osteogenesis.In order to obtain a new biomaterial that can both control infection and promote bone defect healing efficiently,and provide some theoretical and experimental basis for its application in the treatment of infected bone defects.Experimental methods:1.Two different methods to prepare a rabbit tibial chronic osteomyelitis modelTwo different methods were used to construct a rabbit tibial chronic osteomyelitis model and to compare them.Methods:Forty-five male New Zealand rabbits were randomly divided into the following five groups:small-bore cotton thread experimental group(A1),small-bore cotton thread control group(A2),large-bore gelatin experimental group(B1),large-bore gelatin control group(B2),and blank group.10rabbits in each group,except 5 in the blank group,were used for the A1 group.In group A2,the rabbit was drilled with a 2-mm drill in the upper middle tibia and 0.1 ml of saline was injected through the hole;in group B1,the rabbit was drilled with a 5-mm drill in the upper middle tibia and 1×10~8cfu suspension of Staphylococcus aureus was injected through the hole with a gelatin sponge needle,and in group B2,the rabbit was drilled with a 5-mm drill in the upper middle tibia and 0.1ml of saline was injected through the hole.After drilling,0.1 ml of saline was injected into the rabbit tibia;groups A and B closed the holes with bone wax and sutured the incisions layer by layer after the injection of bacterial solution or saline;the blank group did not perform any manipulation.The right hind limb,trauma and infection of the experimental animals were closely observed during 28 d after surgery.Venous blood was taken from each group of experimental animals at 1,4,7,14 and 28 d after surgery to detect the changes of erythrocyte sedimentation rate(ESR)and C-reactive protein level(CRP)in the blood,and the body temperature of the animals was measured at each time period.2.Animal experimental study of 0.1%SF/VANCO/PLGA/β-TCP composite scaffold for the treatment of infected bone defectsIn order to further treat chronic infected bone defects in rabbits,according to the findings of the first part of the experiment,the large-hole sponge method was chosen to inject Staphylococcus aureus(1×10~8 cfu)suspension with a gelatin sponge needle after drilling a 5-mm drill in the middle and upper tibia of 40 rabbits.36 New Zealand rabbits were selected by postoperative general condition and X-ray examination for further experiments and divided into four groups as follows:group A Group A:Clear control group(9 rabbits);Group B:Implanted with VANCO/β-TCP material(9 rabbits);Group C:Implanted with vancomycin/PLGA/β-TCP composite(9 rabbits);Group D:Implanted with 0.1%SF/VANCO/PLGA/β-TCP composite(9 rabbits).Another 6blank control groups were set up.The general condition of the animals in each group was observed after surgery,and the erythrocyte sedimentation rate,C-reactive protein concentration and blood vancomycin concentration were measured at 1,4,7,14 and 30d after surgery to observe the infection control in each group,and the local osteogenic effect and scaffold degradation by X-ray and Micro-CT at 4,8 and 12 w after surgery.Three tibia specimens were taken from each group at 4w,8w and 12w for gross observation,pathology,immunohistochemistry and bacterial culture.The complete tibia was taken for biomechanical examination at 12w postoperatively.Results:1.The survival rate after 30 d was 89%in the A1 group,90%in the B1group,and 100%in the A2 and B2 control groups and the blank group.Postoperatively,body temperature,blood sedimentation and C-reactive protein were elevated to different degrees in A1 and B1 rabbits,and the elevation was more obvious in A1 group than B1 group,while the change from preoperative was not significant in control and blank groups.At 1w postoperatively,swelling,pus drainage and sinus tracts were observed in the right lower limb of both A1 and B1 groups.At 4w postoperatively,the imaging manifestations of both groups A1 and B1 showed signs of chronic osteomyelitis such as local soft tissue swelling,bone cortical thinning,osteolysis,osteosclerosis,reduction in the number of bone trabeculae,osteosclerosis,and dead bone formation.Pathological findings:A large amount of necrotic tissue in the medullary cavity with a large number of inflammatory cell infiltration,obvious periosteal reaction,incomplete bone cortex,and destruction of bone trabeculae were seen in both A1 and B1 groups at 28 d after surgery.After 30 d,bacterial cultures were obtained by grinding purulent tissue from the medullary cavity of tibia and fine dead bone bitten off in A1 and B1 groups,and Staphylococcus aureus was cultured in both groups,while A2 and B2 control groups and blank group were negative.The results showed that the A1 group could simulate the chronic osteomyelitis model and the B1group could simulate the chronic infected bone defect model.2.In the 0.1%SF/VANCO/PLGA/β-TCP composite scaffold group,vancomycin could be detected in the blood within 30 days after operation,and the erythrocyte sedimentation rate and C-reactive protein showed a decreasing trend until they returned to normal,which effectively controlled the infection.In the simple debridement group,all patients had re-infection,and the infection involved the medullary cavity,and there was proliferative sclerotic bone around it.The vancomycin-loaded scaffold group and VANCO/PLGA-loaded scaffold group had poor effect on infection control due to the rapid release of vancomycin in the local area.The vancomycin-loaded scaffold group and VANCO/PLGA-loaded scaffold group could also induce new bone formation,but the effect was poor,and the cortex of bone was discontinuous.Only the loaded0.1%SF/VANCO/PLGA/β-TCP group successfully controlled the infection and induced new bone formation in the bone defect by releasing vancomycin within 30 days after operation.X-ray showed that only 0.1%SF/VANCO/PLGA/β-TCP composite scaffold group could effectively control the local inflammation around the bone defect,the material began to fuse with the surrounding bone tissue,and the bone cortex around the material began to become continuous.After 8 weeks,the material began to break down,and a large number of new bone grew through the pores.A large amount of new bone formation around the SF composite scaffold was observed in gross specimens,Micro-CT,and pathological sections,indicating that the new bone was generated around the scaffold material and had an obvious osteogenic effect.Immunohistochemistry showed that the 0.1%SF composite scaffold had a large number of OCN expressions around the new bone.The other groups had poor inflammation control and osteogenesis.At 12 weeks after operation,the 0.1%SF composite stent group had good mechanical strength.Conclusions:3D printed 0.1%SF/VANCO/PLGA/β-TCP composite scaffold has good results in the treatment of chronic infected bone defects with effective delayed drug release,greater advantages in local anti-infection and osteogenesis,as well as good biocompatibility and mechanical strength.This experiment provides a strong experimental basis in the future clinical treatment of infected bone defects.
Keywords/Search Tags:Chronic osteomyelitis, Bone defect, Silk fibroin, Vancomycin, Composite scaffold
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