| In the clinical using of locking nail, there is a contradiction between the hard fixation and the flexible fixation. It had been confirmed that the delay union and ununion is high after hard fixation. In order to resolve it, the patients who operate with hard fixation need to extract it after 6 to 8 week.. These results in the patients not only need to operate many times but bone is easier to refracture. Recent years, it is confirmed by clinic and experiment that micromovement can promote the formation and calcification of the bone and accelerate the healing course of fracture and the circular micromovement stress provides optimum biomechanical surroundings. The auto-control micromovement locking nail (AMLN) devised in this experiment has dentate structure between 0.8-1.2mm. With the muscle contraction or weight carrying of the body, it can produce axial micromovement in 1mm between fracture gaps, at the same time, control the bent, scissor, and spiral stress. This make the end of fracture have physiology stress stimulation and conduct in the course of the healing of fracture, which avoids the stress concentration and stress protection.Bone tissues, as a motive tissues and received stress organs, apart from weight carrying of the body, bear motive stress produced by the motion of joint and muscle contraction. We imitate this mode of motive healing of fracture and create bettermechanical surroundings--make joint and muscle motion early. This physiologicalstress producing by it can make bone tissue bear and conduct early, resulting in the balance and stability of bone-muscle system and then accelerate the healing of fracture. Objection:In this experiment, the author applied goat femoral transverse fracture model, observing fracture healing process because of internal fixation with two kind of internal fixative instrument and researching the mechanism of fracture healing in the condition of micromovement according to the stress of biomechanics and stress protection in different stages. Materials and methods:1. The structure of auto-control locking intramedullary nail: on the basis of common intramedullay nail composition, we improve the structural projection of intramedullary nail and add the auto-control equipment to its structure. Our auto-control locking intramedulary nail composed of proximal nail, distal nail, blade for prohibition and envelope. The proximal and distal are connected by dentate locking structures. The blade for inhibition is inserted into the nick between the two nails, and then the whole structure is fixed by an envelope from external. The space should be retained between the proximal and distal nails when they are being connected. So both of them could slide to median line as the muscle contraction or weight carrying of the body. Then the auto-control could achieve, and the normal compress could produce.2. Making of the experimental sample: selecting age between2-3 years healthy local goat 14, fix the experimental leg with auto-control locking intramedullary nail and the control one with G-K nail, kill them at 1, 2, 4, 8 week in the different healing stages. Then measure the x-ray, strength, still, stress level, stress protection at the different healing stages, and evaluate the macroscopic and microscopic biomechanics mechanism, which accelerate the healing of fracture.3. The establishment of experimental biomechanical model: animal femoral models of adult were obtained. Before experiment, all soft tissue was researched. Then the distal end of the model was fixed with bone sticker to maintain it stand with single foot echomotically. The models were divided into experimental group and control grouprandomly.4. Loading status of the experimental biomechanical model: Load ranging from one to 250 N was added to the experimental model. Experimental was ended when the models were destroyed. The shift was monitored by shift sensor with high accuracy. Variation was read by digital apparatus. Loading speed of experimental apparatus was controlled less than 1 .4 mm per...
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