Experiment Study On Mandbular Bucco-directional Distraction Osteogenesis

Objective1. To discuss the characteristics of the mandibular deformity of hemifacial microsomia;2. To design a new type of distractor that could achieve the purpose of mandbular bucco-directional distraction osteogenesis.3. To establish an animal model for testing and evaluation the effect of the distraction process during mandibular bucco-directional distraction osteogenesis, which gives reference for further clinic application.Methods1.32 cases of HFM from 2006 to 2010 were collected in our hospital. CT scanning is performed for all patients. Then, summarized the mandibular deformity characteristics through four steps:3D reconstruction, mirror, discrepancy analysis and partition.2. Reviewed the anatomy of the mandible and the theories related with distraction osteogenesis. Design the distractor and the surgical process for mandbular bucco-directional distraction.3. An osteotomy was made in the same position of the mandible in goats. A customised bucco-directional distraction device was used to distract the mandible. After a 7-day latency period the device was activated at a rate of 0.5 mm twice per day (1 mm/d). The distraction devices were removed after consolidation for 3 months. The histology examination, biomechanical analysis, X-ray spectrograph analysis were conducted at different points in time after surgery to examine the osteogenic situation and evaluate the distraction strategy.Results1. The mandibular deformity characteristics of hemifacial microsomia shows regular diversity. Compared with the unaffected side, affected side shows a "hollow-bulge-mid bulge" process from ramus to chin.88% of all cases present the characteristics of the angle region missing, in which 53% of the cases show the width insufficiency of the mandible.2. The mandibular bucco-directional distraction device consists of three parts:the base, guide rod and screw. When the screw of the distraction device rotates a circle in a clockwise direction, the distraction device will extend 0.40 mm in axial direction. Working together with micro-hinge, the distraction device achieves the purpose to widen the mandible in bucco-directional direction.3. Animal experiment results show that from 0 to 12 weeks post the bucco-directional distraction osteogenesis, the ossification mode in the distraction gap is intramembranous ossification, and the distraction gap will be filled by new bone gradually. On the other hand, after the distraction the biomechanical property of the mandible could catch up with the unaffected side, and with six month follow-up of mandibular distraction osteogenesis, the mandibular bucco-directional distractor is an effective tool that achieves a stable mandibular distraction.ConclusionIn this paper, we proposed a new method for measuring the mandible of the patients with hemifacial microsomia syndrome precisely. The method is based on 3D medical image reconstruction technology and computer graphics and image processing technology. According to the Measurements, there are certain laws on the deformity of the mandible. The conclusion will put forward some references for the treatment of HFM.In this study, we design a new type of distractor that could achieve the purpose of mandibular bucco-directional distraction osteogenesis. By a number of experiments, which were performed on goats, a conclusion which appears to be confirmed is that our distraction strategy is effective. The conclusion provides a new breakthrough in the field of 3D distraction osteogenesis, and has certain prospect for clinical application and socio-economic value.