Curvilinear Distraction Osteogenesis With A New Internal Curved Distractor In Beagles

BackgroundMandibular defects that arise from congenital mandibular hypoplasia,trauma,oncological resection can cause maxillofacial morphology abnormalities and dysfunction.Traditional repair methods such as autologous bone grafting is limited due to source scarcity,complications,and prolonged repair time.The special anatomical shape of mandibular also severely restricts the repair effect.Since 1990,MaCarthy successfully used the distraction osteogenesis(DO)for the first time to achieve the extension of the mandible,solving the difficult problem of traditional surgical approaches.Since then it has been widely used in the treatment of maxillofacial surgery deformity and reconstruction of the jaw.In recent years,the external one-way distractor has been unable to meet the actual needs.In order to make new bones closer to the jaw contour to correct complex jaw deformities,the study of internal curved distraction osteogenesis has become one of the main research directions.ObjectiveIn order to realize the curved distraction osteogenesis to treat complex jaw deformities,our team have invented and manufactured a new internal curved distractor to investigate the feasibility of using the new internal curved distractor in the application of mandible extension in dogs.Material and MethodsA mandibular osteotomy section was made in each of 6 adult dogs.The internal curved distractor was implanted.After 7 days of latency,the distraction was performed at the rate of 1mm per day,followed by 12 weeks consolidation period.CT examination is performed during the distraction process and the consolidation period.At the end of the consolidation period,sacrifice the dog and take specimens.The mandibles were evaluated by X-ray examination,general observation,Micro-CT and histological analysis.ResultsCurvilinear distraction was successful performed in four of the six dogs(distraction separately lasted 10、15、18 and 21 days).The mandible is extended,the length and height of the mandible were separately increased by 15.5±5.5 mm and 4.6±1.6 mm.Radiographically,there was no visible difference in the osteogenic density between the distraction gap and the natural bone.Micro-CT results showed that the new bone in the distraction gap has matured.The trabecular bone density and thickness of the new bone were lower than the cortical bone of the natural mandibular body,but much higher than the condylar cancellous bone.The new bone density and thickness of the upper part of the new bone was higher than that of the lower part.The BMD,BV/TV and Tb.Sp values were significantly different(P<0.001),and there was no significant difference in Tb.Th(P=0.584)and Tb.N(P=0.058)values.Micro-CT three-dimensional reconstruction found that the trabecular bone arrangement was directional and consistent with the direction of the distraction.Histological examination showed mature new bone,and large trabecular bone parallel to the direction of distraction was seen.The results further demonstrate the consistency of new bone osteogenesis direction and distraction direction.ConclusionThe new internal curved distractor can realize the curved distraction osteogenesis and extend the mandible in a curved shape.