Influence Of Temporalmandibular Joint After Intracapsular Condylar Fracture:An Experimental Study In Growing Miniature Pigs

Condylar fracture is the most common in mandibular fracture,Accounting for 18%⁵7%^[1].With the development of imaging technology?CT,MRI?,revealing that the condylar fracture could be the cause of the temporomandibular joint dysfunction,Especiallythe comminuted fracture and mandibular branch height shorten fracture,prognosis is poor^[2,3].At the same time,the accuracy rate of diagnosis is also gradually improved.Reports indicate that intracapsular condylar fracture especially the sagittal fracture and comminuted fracture can cause the serious injury of cartilage and traumatic osteoarthrosis.Intracapsular condylar fracture in children and adolescents may damage the condylar cartilage cap and hinder the growth of mandibular branch,and then the mandibular deviation?unilateral fracture?or mandibular retraction?bilateral fracture?deformity appeared.There are many factors such as age,damage degree and so on^[4].Osteogenesis is active and blood vessels are rich in chidren,so the repairment is hyperplasia and lead to traumatic osteoarthrosis and ankylosis easily and then affect the mandibular development.The treatment of condylar fracture has not reached a consensus till now,the treatment of intracapsular condylar fracture especially the pediatric/children's intracapsular fracture is an academic controversy.In this study,the growth and reconstruction of temporomandibular joint after condylar intracapsular fracture was discussed based on the experimental findings;The results will provide the basis for clinical treatment.Materials and methords:1.To build the intracapsular condylar fracture model in miniature pigs and make the three-dimensional computed tomography analysis based on the datas.Eighteen growing miniature pigs?2-3 months?were selected to buildanimal models,computerized tomography was used to scan the skull 4 or 12 weeks postoperatively and to analyse the mandibular branch height by ProPlan CMF1.3 software and then to evaluate the growth and development of mandibular branch.2.The histopathologic evaluation of TMJ after intracapsular condylar fracture in natural healing processAll animals were put to death 4weeks and 12 weeks after operation respectively.The specimens were observed generally,and compared the influence on PT-OA between each group with H&E?toluidine blue stain and sarranine O stain.3.The expression of Ihh?PTHLH/PTHrP and Runx2 in condylar cartilage and relative quantitative analysisTo observe the distribution and expression of Ihh?PTHLH/PTHrP and Runx2 in PT-OA specimen from miniature pig models with immunohistochemistry and Real time PCR methods and learn about the influence on cartilage extracellular matrix.Results:1.The author successfully established condylar intracapsular fracture model by miniature pigs and there are statistical significance between the experimental group and control group?p<0.05?based on the analysis of ProPlan CMF1.3.2.Cartilage structure,cell number,cell cloning,tide mark and synovial membrane have the statistical significance in ICF-B+disc displacement?ICF-B and control groups.3.Ihh?PTHLH/PTHrP and Runx2 distributed in proliferation and hypertrophy zone in cartilage of miniature pig TMJ;in addition,as time goes on,Ihh,PTHLH/PTHrP and Runx2 mRNA expression levels drop and there are statistical differences between the experimental group and control group at each time point?p<0.05?.Conclusion:1.The growth of mandibular branch is restrained because ofintracapsular condylar fracture and there are statistical significancesin ICF-B+disc displacement?ICF-B and control groups.2.In PT-OA,the most serious degenerative change was disc displacement combined with condylar fracture;condylar fracture was second.There are statistical significances in experimental group and control group.3.Ihh,PTHLH/PTHrP and Runx2 protein affect the condylar cartilage cell proliferation and mature and then influence the endochondral ossification.They play a vital role in the occurrence and development of PTOA.But the mechanism?mutual adjustment or interdependent?of Ihh,PTHLH/PTHrP and Runx2 in PTOA still needs further research.