Bifocal Distraction Osteogenesis For Reconstruction Of Mandibular Defects In Goats

Bifocal Distraclion Osteogenesis for Reconstrucdon of Mandibular Defects in Goats The concept of distraction osteogenesis was introduced by Gavriel flizomv and has been used and developed over the past 45 years, it has gained acceptance and been ~dely used for the elongation arid itconstmction of long bones. Studies by Constantino et al and Phillips et al have shown this technique to be successful in bridging segmental mandibular defects in dogs with newly fom~d bone. We designed this study to evaluate the feasibility and effectiveness of this technique in bridging segmental defects in mandibles using the bifocal distraction devices, which are made by ourselves. MATERIALS AND MEFHODS: Three goals served as the experimental subjects. The pure Tai2 was adopted as the metal material to fabricate the self .made distraction device in mechanic way. An external incision was made parallel to the mandibular body; distraction appliance maintained the proximal and distal mandibular stumps in anatomic position and provided the mechanism by which the transport disk of bone could be moved across the segmental mandibular defect A 15 mm segmental of mandibular body was then removed by a through 梐nd -through osteotomy. An conticotomy was made creating a transport disk approximately 1.0cm wide. The entire intermedullany cavity, inchiding the inferior alveolar artery was protected One subject was in acute cxperiment. The other subjects were in chronic, beginning on day 8, the transport disk was advanced 0.5mm, two times per day, for a total of 1mm each day. The 8 weeks and 12 weeks after the transport disk reached the distal mandibular stump, the goats were killed Roentgenograms were taken at 2,4,8, until 12 weeks. After death, the resultant bemimandiIles were sectioned encluding uitximal, transport dislc new formed bone and distal mandibular stump. The sections were decalcified in hydrochloric acid solution and embedded in paraffin; representative sections were stained with hematoxylin-eosin, trichrome stain and were examined using a light microscope (Olympus) at magnifications of 13 and 30. RESULTS:Acute subject indicates the BDO operation method could be well performed at the experiment; the inferior alveolar artery can be distracted with normal appeinnce.Ai1 of the subject -5- goats in chronic survived the entired duration of the study There were neither wound infections, nor any major or minor complications. The subject goats bad no difficulty maintaining adequate oral nutrition during the entire length of the study and did not demonstrate any physical deficit while the distraction appliances weit in place. The regenerate segment was comparable in diameter ~th the native mandible and the exact location of the junction between the regenerate and the preexisting bone could not be determined easily After the first 2 weeks of distraction completation, the regenerate borne was radiogmphically isodense, even through the reconstructed areas were firm and felt no different on palpation from the preexisting mandible. Over the following 10 weeks, the new bone became progressively radiodense. Histologic evaluation revealed calcified irabecular and dense cortical bone filling d~ region of the segmental defects. The junction between the regenerate bone and the mandibular distal stump demonstrated osseous union ~th multiple mature bones and no evidence of fibrous union. The junction between the transport disk and the proximal segment of...