| Background:Large defect of long tubular bone caused by severe trauma,bone tumor resection and osteomyelitis debridement has always been a difficult problem in orthopedics.Bone nonunion and other complications caused by large bone defect often lead to serious consequences such as limb disability,causing much pain and heavy economic burden to patients.At present,autologous bone graft is still the gold standard in the clinical treatment of large defect of long tubular bone.But in the case of large bone defect,the source of autologous bone graft is limited.Massive autologous bone graft causes many complications,such as nerve and vascular injury,infection and chronic pain.In addition to autologous bone graft,some other methods have also been used in the repair and treatment of long tubular bone defects,including Ilizarov technique,Masquelet technique and bone tissue engineering.However,there are still many deficiencies in the above methods.Ilizarov technique requires complex external fixator,and in the process of distraction,the pressure of soft tissue often leads to continuous pain,combined with the risk of force line deviation,infection and nerve injury.Masquelet technique induces the formation of induction membrane through occupation of polymethyl methacrylate(PMMA)in the first stage.In the second stage,it still relies on autologous bone graft.In addition,the treatment cycle of Masquelet technique is very long,which also increases the uncertainty.Bone tissue engineering is one of the research hotspots in recent years.The three main biological elements required for bone tissue engineering include seed cells,extracellular matrix scaffolds and cytokines that promoted growth,differentiation and angiogenesis.There is still no material to completely solve the problem of large bone defects.Fracture healing is a complex biological process,which contains many elements.If any element is damaged,it may delay the process of fracture healing and eventually leads to bone nonunion.If bone healing cannot be formed in one-stage treatment,most of the long tubular bone defects will lead to atrophic nonunion due to the lack of bone and blood supply.Therefore,the treatment of large defect of long tubular bone should realize bone healing in the first stage as far as possible,to avoid bone nonunion,reduce the pain of patients,and improve the quality of life and limb function.Masquelet technique arouses strong interest of our research group.We attempt to make further exploration and improvement in this study based on Masquelet technique,so as to obtain a better bone induction technique.At the same time,to explore whether a new induction technique can be used to repair large defect of long tubular bone without bone graft and seed cells.At present,silicone rubber materials have been widely used in biomedical fields,with good safety and biocompatibility.Some researchers use silicone rubber tube to induce nerve regeneration,and achieve good results.However,there is still no literature report on the use of silicone rubber in the treatment of large defect of long tubular bone.Based on Masquelet technique and the inspiration of silicone rubber tube induced nerve regeneration,our research group try to use silicone rubber sealed channel to repair large defect of long tubular bone,and we design relevant experiments in both vivo and in vitro.Objectives:To prove the effectiveness of silicone rubber sealed channel induced repair of large defects of long tubular bone in rabbits through experiments in vivo and in vitro,and explore its osteogenic process and mechanism.Methods:1.BMMSCs of SD rats were isolated and identified.2.In vitro experiments,the extracted BMMSCs were used to verify the biocompatibility of silicone rubber materials and the feasibility of implantation in vivo.3.In vivo experiment,the radius defect model in rabbits was established,and the silicone rubber sealed channel was implanted for induction.The materials were removed at eight time points of 1 day,3 days,7 days,14 days,4 weeks,8 weeks,12 weeks and 16 weeks to prove the effectiveness of silicone rubber sealed channel in inducing the repair of large defect of long tubular bone.The process of osteogenesis induced by silicone rubber sealed channel was further explained by X-ray,Micro CT,bone tissue fluorescence labeling and pathological staining.Results:1.BMMSCs from SD rats were successfully extracted.Based on BMMSCs,in vitro experiments we proved that the silicone rubber material met the implantation standards in terms of cytotoxicity,hemolytic reaction,cell adhesion and the effect on the osteogenic ability of BMMSCs.It was feasible as an osteogenic induction material.2.In vivo experiments,we proved that silicone rubber sealed channel could induce the repair of large defect of long tubular bone in rabbits,which is a process of endochondral osteogenesis.In the initial stage of induced osteogenesis,hematoma tissue was formed in the sealed silicone rubber channel.The hematoma tissue was rich in osteogenesis related protein,angiogenesis related protein and TGF-?1.And then the hematoma tissue gradually turned into vascularization and endochondral osteogenesis.Finally,the cartilage tissue was replaced by mature bone tissue,and the new bone had good blood supply.This induction method depended on the sealed environment of silicone rubber channel.Conclusion:This experiment proved that silicone rubber material had good biocompatibility.Silicone rubber sealed channel could induce the repair of large defects of long tubular bone in rabbits and realize bone regeneration.In this experiment,this process did not rely on bone grafting and could achieve bone healing.The process of osteogenesis induced by silicone rubber channel was an endochondral osteogenesis process.The hematoma tissue formed in the early stage was rich in osteogenesis and angiogenesis related proteins,and gradually turned into vascularization and endochondral osteogenesis,and finally realized bone regeneration.In this process,the complete and sealed environment of silicone rubber channel was the key factor.This experiment provided a new idea for the clinical treatment of large bone defect in the future.The innovation of this study:1.In this study,a method of "silicone rubber sealed channel induced repair of large defect of long tubular bone" was proposed for the first time.The sealed silicone rubber channel was used to connect the two ends of the bone defect.It created a closed environment,and prevented the fibrous tissue from entering bone defect.It effectively avoided bone nonunion.The experimental results showed that the silicone rubber material could not directly induce the osteogenesis and mineralization of BMMSCs,which further showed that the key factor of osteogenesis was the sealed environment of the channel.2.Compared with Masquelet technique,the main advantage of method used in this research was that there was no need for bone grafting in the treatment process.Different from tissue engineering technique,this method did not need seed cells and complex synthetic materials.It was a new method of bone induction and the new concept of osteogenesis.3.The defect length was more than 4.5 times the bone diameter in this research,which was longer than that of similar experiments.It showed that this induction method had a good treatment effect.The results reveal that the mechanism of "silicone rubber sealed channel induced repair of large defect of long tubular bone" was a process of endochondral osteogenesis.Hematoma tissue was formed in the sealed channel in the early stage,and bridging was formed at both ends of bone defect.The hematoma tissue was rich in osteogenesis related protein,angiogenesis related protein and TGF-?1 which could effectively induce osteogenesis.This induction method depended on the sealed environment of silicone rubber channel. |
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