Experimental Study Of Calvarial Defect Reconstruction By Transport Distraction Osteogenesis

Traumatic or postsurgical calvarial defects are commonly encountered clinical problems in craniofacial surgery. Calvarial defects are particularly challenging because they do not heal spontaneously in humans older than 18 to 24 months of age. Alloplastic metallic and nonmetallic grafts have been used to close calvarial defects; however, biocompatibility concerns regarding infection have largely limited their use. Presently, bone autografting and split calvariectomy are the treatments of choice for adult calvarial defects. These procedures can be painful and have inherent donor-site morbidity, in an attempt to circumvent the potential problems associated with bone grafting,new methed should be explored to treat calvarial defects.Distraction osteogenesis(DO) in the treatment of congenital and acquired craniomaxillofacial deformities has been an alternative and widely used. The indications of distraction osteogenesis for reconstruction operation have been rapidly widened in the fields of orthopedic,craniofacial,and maxillary surgery,but there were litter paper about calvarial defect reconstruction Therefore, we used transport distraction osteogenesis to facilitate closure of calvarial defects.Although numberous experiments and clinical studies on DO appeared,thereare still some questions unclear,including long duration of treatment and incidence of complications.Attempts should be made to accelerate osteogenesis and promote maturity of the distracted callus.Based on above knowledges, An animal model was established in goats for calvarial defect reconstruction by transport DO,then gross, X-Ray, histological and scanning electron microscopy(SEM) analysis were performed to evaluate the state of the bone healing and regeneration; To evaluate the effect of the structure and function of the brain during transport distraction osteogenesis ,expression of PCNA and bFGF of dura mater were assessed by immunohistochemical staining; CCP and S100B was quantitatively measured. To investigate the possible osteogeneic effect of mesenchymal stem cells(MSCs) on ditracted callus,goat MSCs were harvested and cultured in vitro, and then transplanted to the gap of distracted callus immediately after distraction had been terminated. The effect of transplantation of MSCs on callus formation were evaluated by histologic , histomorphometric examinations and SEM analysis . Bone mineral density (BMD) in the distracted callus was evaluated using QCT during DO.The results of this study showed:all defect were repaired by transport distraction osteogenesis, and the newly formed bone was found in the distraction gap. The biomechanical properties, expression of PCNA and bFGF of dura mater were significant increase after 0,2, 4weeks in the consolidation compared with the control groups;There was no significant change about Cerebral blood flow and S100B in differet time during DO;A great number of MSCs with high purity could be obtained by culture in vitro in our studt ; Histologic and SEM analysis indicated a significant increase in bony union of the distraction regenerate in the MSCs treated groups compared with the control groups.Corresponding to the histologic and SEM analysis findings, the Bonehistomorphometry showed an earlier and more intensive bone formation in the treated side after 2, 4, weeks compared to the control side; QCT showed a significant increase BMD in the distracted callus in the treated side after 2, 4,and 6 weeks compared to the control side.Based on these findigs, the technique of transport distraction osteogenesis may be an alternative method in repair of calvarial defect.The goat is an ideal animal model for calvarial defect reconstruction by transport distraction osteogenesis, and there was no negative effect on the dura mater and brain during DO; Transplantation of autologous MSCs may have beneficial effect on bone formation following distraction osteogenesis in a goat model of calvarail defect.