Foundmental And Clinical Study Of Complicated Bone Defect With Osteomyelitis

Bone Defect is one of the toughest jobs to do in clinical practice. The mostcommon reason includes comminuted fracture by high-energy trauma, bone nonunionby repeated operations, bone tumor and removal of mass bone by osteomyelitis. Themost difficult obstacles to cross for complicated bone defect are infection andmalfunction of adjacent joint. Infection would restrain the process of bonereconstruction or even lead to severe systematic disorders. Malfunction of jointsdirectly infect normal anatomy and function of patients. Critical bone defect byhigh-energy trauma is often accompanied by infection of the injured location, whichwould cause necrosis and cavities of bone. And this in turn exacerbates severity ofbone defect. Besides, bone tumor often occurs in metaphyseal of long bone which isadjacent to joint such as tibia, humerus and distal femur of young patients. Afterexcision of bone tumor, large volume of bone defect will also lead to malfunction ofjoint. In this study, we focus on the most formidable task of bone defect mentionedabove. According to the sequence of regular treatment, we attempted application ofhydroxyapatite and vancomycin composited electrospun polylactide mat forosteomyelitis and bone repair in SD rats for the first stage of treatment.3D printingtechnique was put into clinical practice of joint anatomy and function reconstructionfor the second stage of treatment.Part Ⅰ The antimicrobial application of biodegradable polymer materialsin biomedical area.The first part concentrated on current situation of treatment for complicated bonedefect with osteomyelitis. A better routine was proposed that slow-releasebiodegradable polymer biomaterials could be used at early stage to eliminate infectionand generate osteoinductive effect, then3D printing was used for reconstruction ofmalfunction caused by bone defect. The antimicrobial biomaterials which can providea promising way to cure osteomyelitis were discussed. Among which hydrogels andelectrospun fibers were the most important ones because of their high porosity and drug loading capacity. The advantages and disadvantages of antimicrobial hydrogelswere expounded and finally electrospun nanofibers were selected to be the one to treatosteomyelitis and bone defect in this study.Part Ⅱ Hydroxyapatite and vancomycin composited electrospun polylactidemat for osteomyelitis and bone defect treatmentFabrication and characterization of electrospun nanofiber mat: novel electrospunmat was established from polylactide (PLA), hydroxyapatite-graft-polylactide(PLA-g-HA) and vancomycin to treat osteomyelitis and bone defect. HA wascomputed with the content of HA in PLA-g-HA and then grafted onto PLA.Electrospun nanofiber mats were grouped according to whether HA or VA wasincluded in the content. PLA, HA and Van were electrospun into fiber mats accordingto different groups. Morphology of fibers was observed by SEM, distribution of VAand HA were inspected by spectrum analysis and Mapping analysis. The diameters ofthe fibers were around500nm. Electrospun fiber mats were put into pure PBS andElastase PBS solutions to test in vitro degradation performance, which exhibited fineperformance especially when VA and HA were put into fiber mats.Antimicrobial Test: Gram-positive bacterium (i.e., Staphylococcus aureus) andGram-negative one (i.e., Escherichia coli) were selected as standard strains. SpraidTest was carried on each group of fiber mats. Photos of12h and24h were recorded toanalyze the inhibitory effect. Then bacteria were also put into liquid medium whichcontains the same amount of fiber mats from different groups to check if the fibermats can maintain antimicrobial effects. Finally all groups of fiber mats wereimmersed into liquid medium with S.aureus and E.coli. Then morphology,distributionand quantity of bacteria on the fiber mats were oberseved by SEM. Both thequantitative tests in liquid medium and qualitative ones on solid matrix revealedsuperior antimicrobial effect of the electrospun mat. SEM of bacteria on differentmats provided intuitive antimicrobial effects.On this basis, an osteomyelitis and bone defect model was established by makinga6mm×2mm defect on the proximal end of femur in male Sprague-Dawley (SD)rat by injecting104CFU Staphylococcus aureus into the femur.1week later,debridement was performed and the electrospun mat was implanted. Blood test andX-ray were performed on8and16weeks, and rats were sacrificed for pathologicaland real-time polymerase chain reaction analyses. All results demonstrated that the composite platform above displayed bright prospects for application in treatingosteomyelitis and bone defect.Animal Experiments:Sprague Dawley Rats (SD rats) were taken in preliminary experiments to creatosteomyelitis and bone defect models. Bone defect were operated on the proximalthird segment of the left femur by critical size of6×2mm, different concentrationsfrom102CFU/ml to107CFU/ml0.1ml were injected into defect location. One weeklater HE section were taken out from the femur,104CFU was the right concentrationfor rat models.SD rats were divided into7groups in formal experiments to creat diseasemodels，debridement were performed one week later, electrospun fiber mats were putinto6groups and VA powders were put into1group. X ray examination, routineblood test, anatomical photographs, femur bone and surrounded muscle HE section.Comparison between all groups revealed groups with electrospun fiber mats hadsignificant high survival than the group with pure VA. Groups with mats containingVA had significant lower white cell number than those without VA, groups with matscontaining HA had better bone formation effect than those without HA.All experiments above demonstrated that hydroxyapatite and vancomycincomposited electrospun polylactide mat can have higher survival, better antimicrobialeffect and bone formation effects in osteomyelitis and bone defect treatmentcompared with traditional clinical practice.Part Ⅲ Applications of3D printing in clinical practice of complicated bonedefect.Traditional treatment of severe and complicated bone defect will lead to jointfusion, shortened limb and even amputated extremity. Here in this study we take onepostoperative infective wrist with severe bone defect, one vulnerarious shoulder withsevere bone defect and several bone tumors for examples to explore3D printingtechnique for treatment of severe bone defect in clinical practice. The process includescollection of patient CT or MR data, removal of image artifact,3D reconstruction inmimics, optimization in Geomagic Studio, union design in UG NX and generation ofsupport in Magics RP. Finally preoperative models, patient-specific instruments wereprinted by EOS powder printing machine and SLA printing machine, patient-specificmetal implants were printed by EBM printing machine. Through all these processes, we can achieve three stages of3D printing application in orthopedics. That is precisemodel and preoperative design of specific patient, patient-specific instrument andpatient-specific implant. Finally normal anatomical structure and part of joint functionof the patient was obtained.In summary, this study explored treatment of complicated bone defect withinfection from foundamental reseach and clinical practice. The results demonstratedthat the valuable plan to treat complicated bone defect with infection is application ofbiodegradable antimicrobial biomaterials at the first stage to eliminate infection andreconstruction of normal joint anatomy and functionality with3D printing at thesecond stage.