| Objective: The specimens of long tubular fractures were fixed by external fixator with titanium alloy pin and carbon fiber resin rod(magnetic resonance compatibility).To investigate the fixation effect and CT imaging effect of titanium alloy pin and carbon fiber resin rod external fixator and stainless steel pin and carbon fiber resin rod external fixator on the fixation of long bone fractures in animals and MRI imaging effects of titanium alloy pin and carbon fiber resin rod external fixator.It provides a biomechanical basis for clinical application of titanium alloy pin-carbon fiber resin rod(magnetic resonance compatibility)external fixator.Methods: Choose 12 fresh sheep tibia,all through X-Ray examination,the elimination of deformities,bone abnormalities of the tibia.According to the AO principle,transverse fractures were made with a pendulum saw.The experimental group was divided into a titanium alloy pin external fixator with carbon fiber resin rod and the control group was divided into a stainless steel pin external fixator with carbon fiber resin rod.After the anatomical reduction of the fracture specimens,the experimental group was fixed with a titanium alloy pin-carbon fiber resin rod external fixator,and the control group was fixed with a stainless steel pin-carbon fiber resin rod external fixator.CT scans were performed for the experimental group and the control group,and MRI scans were performed for the experimental group.Finally,the experimental group and the control group were placed on the biomechanical test machine,respectively,axial compression experiment,torsion experiment and four-point bending experiment.Conduct biomechanical experiments.Results:1.CT imaging of specimens in titanium alloy group and stainless steel group: two experienced radiographers performed CT imaging of the two groups of external fixation models,and independently scored the image quality using the 4-point method.If there were different opinions,the third physician was invited to discuss and decide.Evaluation criteria: 1 point,severe artifacts around the metal,unclear surrounding bone;2 points,there is a small amount of artifact around the metal,the surrounding bone is acceptable;3 points,no obvious artifacts around the metal,bone is clear;4 points,no artifacts around the metal,excellent image.The rank sum test was used for data analysis between the two groups,P <0.01,and there was a significant statistical difference between the two groups.2.MRI of titanium alloy external fixation frame Group under 1.5T: Sample magnetic resonance imaging of titanium alloy pin-carbon fiber resin rod external fixing frame group has a little pseudo-shadow,but does not affect the overall imaging effect.3.Axial compression experiment: the fracture models of the two groups were firmly fixed on the biomechanical experimental machine to ensure that the axial pressure was in line with the axis of the experimental tibia model.Axial pressure was applied from the tip of the tibia,the maximum load was set at 200 N,and the pressure increased by 10±5N,and the displacement of the fracture end was recorded under different loads.The displacement of the two groups increased with the increase of load pressure.Under the vertical loads of 50 N,100N,150 N and 200 N,the fracture end displacements of the control group were 1.547 ±0.154 mm,3.084± 0.331 mm,4.640 ±0.463 mm and 6.169 ±0.664 mm,respectively.The fracture end displacements of the experimental group were 1.586± 0.152 mm,3.171± 0.306 mm,4.749± 0.446 mm,and 6.343 ±0.615 mm,respectively.Independent sample t test was used for data analysis,P>0.05,and there was no statistically significant difference between the two groups of sample data.4.Torsion experiment: the fracture models of the two groups were firmly fixed on the biomechanical experimental machine to ensure that the axial pressure was in line with the axis of the experimental tibia.The gradual torque of the pressure of 0-5Nm was given to the model,and the torsion Angle under different torques was recorded.In this range of torque,two groups of specimens torsion Angle along with the increase of torque increase,under the maximum torque,the control group torsion Angle to an average of 16.257±1.128°,experimental group torsion Angle to an average of 17.333±0.895°.P>0.05,there was no significant difference in torsion Angle between the experimental group and the control group.5.Four-point bending experiment: The two groups of fracture models were firmly fixed on the biomechanical experiment machine,to ensure that the bending stress with the experimental vertical tibia,four-point bending pressure load,uninterrupted gives 0-100 N pressure load,different displacement of the fracture pressure load on the record,within the scope of the load,fracture with the pressure and increase of load,the displacement under the maximum load,the control group was 2.668±0.082 mm,the average displacement experimental group was 2.779±0.122 mm,the average displacement using independent sample t test for data analysis,the experimental group and control group there was no statistically significant difference between the displacement of the change.Conclusion: Titanium alloy pin-carbon fiber rod external fixator and stainless steel pin-carbon fiber rod external fixator have good fixation effect on animal long bone fracture.However,the titanium alloy pin and carbon fiber rod external fixator has more advantages in CT and MRI imaging.For those patients who need MRI or CT examination.Titanium alloy material has good magnetic resonance imaging effect and CT imaging advantages.Therefore,the titanium alloy pin and carbon fiber resin rod(magnetic resonance compatibility)external fixator can be used as the preferred external fixator for patients with trauma who need MRI examination for temporary fixation. |
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