Development And Experimental Study Of Mini-invasive Plate

Objective: To develop three kinds of mini-invasive plate. Machanical tests and animal tests were carried out with the plates to examine and compare their properties with Bridge plate and LC-DCP.Methods: Cone plate, Window plate and Point plate were made with the same size of Bridge plate and LC-DCP. Three-point bending test and torsion test were carried out with the plates fixed to plastic composite bones to compare the mechanical property of these five kinds of plate. 28 adult goats were used in the experiment. 3 of them was used as normal control. 25 of them were divided into 5 groups randomly, there were 5 goats in every group. After the transverse osteotomy of middle shaft of both tibiae was operated on 5 goats of each group, fixed with the five kinds of plate randomly ( 2 of every plate). One group of goats was sacrificed at 1 days, 2 weeks, 4 weeks, 8 weeks and 12 weeks after surgery. The changes of the cortical microcirculation beneath and opposite these five kinds of plate were evaluated by image analysis of the vessels after the ink perfusion.Results: Cone plate has the same bending property with Window plate, they have better bending property than LC-DCP and Pointplate, Bridge plate has the worst bending property. Cone plate has the same torsion property with LC-DCP, they have better torsion properties than Window plate, Point plate and Bridge plate. The experiment showed that the cortical blood flow volume beneath these five plates reduced obviously at the early stage after operation. The cortical blood flow volume beneath the LC-DCP was still lower than the normal control even at 12 weeks after operation. The cortical microcirculation beneath the Cone plate and Bridge plate were better than Window plate, Point plate and LC-DCP. The blood flow volume of Cone plate and Bridge plate reached the highest at 4-8 weeks after operation was over 4 times that of LC-DCP. However, the cortical ischemia opposite the plate was temporary in the all five kinds of plate. The blood flow volume resumed to normal level at 2 weeks after operation.Conclusion: The Cone plate has better machanical property than Bridge plate and LC-DCP. The Cone plate has the same effect to protecting the cortical microcirculation with Bridge plate and was much more favorable to LC-DCP.