The Study On Distraction Osteogenesis For Rehabilitation Of Canine Mandibular Bone Defect Injured By High Velocity Projectile

Between 1945-1987, there were 214 local wars, with 100 million casualties and 25 million deaths. Since then, contrary to expectation, local wars have increased dramatically. With the increase in the efficacy of sophisticated weaponry, so the number of victims increased, and local wars should claim more attention from the medical professions. In a war zone, the face more then other part of body, remains uncovered and exposed to injury. The architecture conception and anatomical variation of essential skeletal construction of the middle and lower-third of the face lead to different types of injury when exposed to high velocity projectiles.The defect of mandible tissue injured by high velocity projectile is very popular in wartime, and the rehabilitation of mandibular tissue defect is very important and difficult for maxillofacial surgeons. DO (Distraction osteogenesis)is a new technique for rebuilding mandible which has been applied in maxillofacial surgery more and more popular and got big success. But it is still not reported that DO is used for rebuilding the mandible defect caused by high velocity projectiles. It is well known that new bone formation depends on sufficient blood supply and nutrition. But in high velocity projectile injury, the blood supply is destroyed greatly. Whether mandible defect can be rebuilt by DO in this condition should be researched. TGF- β is a multifunctional polypeptide. TGF-β diffusely participate in the inflammatory reaction,immune regulation, signal transmission, and so on. TGF- β also is a significant role in bone regeneration.In this experiment, we used a new multifunctional Bio-impact device to establish a standard animal model of mandible bone defect injured by high velocity projectile. Then we observed the changes of microcirculation in mandible after injured by high velocity projectile. We used a Titanium disgracer to rebuild the injured mandible by DO and observed the histological changes of bone in DO period. We also observed the expression of TGF- β₁ in new formed bone in various time point in the histoimmunochemistry way to investigate the role of TGF- β₁ in DO of mandible injured by high velocity projectile. The research works is as follows:1. Application and assessment of Multifunctional Bio-impactor DeviceObjective: We used a new multifunctional Bio-impact device to do the animal experiment of maxillofacial impact injury and projectile injury, and accessed this bio-impact device. Methods: Dogs were chosen to be the experimental animals. We used the I and II impact system of the new multifunctional Bio-impact to impact and shoot the dogs on maxillofacial region respectively. All mechanics signals and injury parameters were recorded synchronization by a signal record system which controlled by a computer. Result: I impact system can lead to soft tissue injury and maxillofacial fracture , and II impact system can lead to soft tissue cavity defect, maxillofacial fracture and bone defect.2. The animal model of mandible defect injured by high velocity projectileObjective: To build a canine model of mandible defect injured by high velocity projectile. Methods: we used II impact system of new multifunctional Bio-impact to shoot dogs mandible with different driving pressures and the projectile is 2.0g iron ball. We observed the pathological changes of the bone at various time after injury by histological way. Result: when the driving pressure is l.OMPa, shooting iron ball to dog's mandible can lead to a bone defect which the mandible is still continuous and the dog is alive. The bone is destroyed obviously within the region of 5mm around the defect, and thrombus can be observed in all tubes. The bone out of the region of 5mm around defect is relatively normal.3. The study on the changes of canine's mandible blood supplying after shoot by high velocity projectileObjective: To observe the changes of canine's mandible blood supply after injured by high velocity projectile and confirm the area of microcirculation changes at various time point. Method: we observed the changes of canine's mandible after shoot by high velocity projectile in different area at various time points by the means of China ink perfusion and color Doppler flow imaging (CDFI). Result: The mandible's microcirculation is affected severely in the range of 5mm around the defect, while the bone out of this range is normal.4. The experiment of rehabilitation of canine mandibular bone defect injured by high velocity projectile by primary distraction osteogenesis in situObjective: To study the treatment of mandibular bone defect caused by high velocity projectile and the biological basis. Method: The canines with high velocity projectile mandibular bone defect were treated by primary distraction osteogenesis. The new bone formation was observed by X-ray, histological section and scan electron microscope. And 3-point bending test was used to assess its mechanical property. Result: The mandibles were lengthened 18.6mm on average in experimental group, and formation of new bone is obviously without bone nonunion and deformity healing. In X-ray examination, bone defect was connected by new bone and bone trabecula can be observed. In histological section, new bone is obviously and lamellar bone can be seen. And there were no statistical differences in strength detected between the experimental and control groups. The new bone was formed by intramembranous ossification.5. Expression of TGF- β₁ in rehabilitation of canine mandibular bone defect injured by high velocity projectile by primary distraction osteogenesisObjective: To investigate the expression of TGF-β₁ in rehabilitation of canine mandibular bone defect injured by high velocity projectile by primary distraction osteogenesis. Method: The canines with high velocity projectile mandibular bone defect were repaired by primary distraction osteogenesis. The regenerating tissue samples of animals lengthened mandibles were harvested at different time points to have immunohistochemistric research of TGF- β₁ protein and analysis TGF- β₁ by using Western-Blot semi quantitative mean. Result: After...