The Design Of T Type Anatomical Plate And The Finite Element Biomechanical Analysis For The Posterolateral Tibial Plateau Fracture

Objective:1.To design a new "T" type anatomical plate for the fracture of the posterior lateral plateau of the tibia.2.Using the finite element analysis software to verify that the new design plate biomechanical properties and biomechanical testing experiment to compare the biomechanical characteristics differences of the new design plate and lateral tibia plateau "L" type plate fixation the fracture of the posterior lateral plateau of the tibia,which can provide a theoretical basis for the future clinical treatment Methods:1.Selecting 50cases(100knees)adult healthy volunteers from April 2017 to June2017.CT scanning on their double knees,to get the original DICOM format image files,and then importing Mimics16.0 graphical analysis software to rebuild normal tibia three-dimensional model,and using the Geomagic Studio2012 software smoothing the tibia model,next using SolidWorks2014 to measure posterolateral parameters of different types of tibial model,combining with the characteristics of posterolateral anatomy of tibial plateau drawing the new plate.Finally,building the posterolateral tibia plateau fracture model,assembling the plate and fracture model then importing ANSYS14.5 finite element analysis software,putting the assembly model an axial stress of 500 N,1000N,1500 N,recording the maximal displacement of the posterolateral tibia plateau fracture block and the equivalent stress of internal fixation as well as observing the biomechanical characteristics of the new type plate.2.Choosing twelve pairs of synthetic tibia models.They were randomly divided into two groups according to the random number table,using oscillating saw building all the artificial bone for posterolateral tibia plateau fracture model.After the modelswere builded,the first group was fixed with a new type plate,the second group was fixed with the "L" plate.The lateral fracture block and the tibia metaphysis end were marked with a vertical distance of 20 mm between the two points.Fixing two groups of tibia models in SHMADZU universal material experiment machine,longitudinal load test on two groups of models,loading rate of 1 mm/min,using electronic vernier caliper measured the vertical distance between two points at load500 N,1000N,1500 N,and repeated the measurement to take the average.Calculated the difference of vertical displacement of two points as the fracture block vertical displacement,and recorded the failure load(load that posterolateral bone fracture block vertical displacement to be 3 mm).For the measurement of the all the collected data in the form of mean ± standard deviation,if all of data conformed to the independence,normality and homogeneity of variance using two independent sample t test statistical methods.If all of data conformed to the independence,normality,but not conformed to the homogeneity of variance,using two independent sample t' test statistical methods.Using SPSS22.0 statistical software for the comparison of differences between two groups of data,inspection level ?= 0.05,P <0.05 suggesting the difference was statistically significant.Results:1.A "T" anatomical plate for the fracture of the posterior lateral plateau of the tibia was successfully designed.2.Finite element analysis results:The maximum displacement of the lateral fracture block at 500 N was 0.012 mm.The maximum displacement of the posterior lateral fracture block at 1000 N was 0.024 mm and at 1500 N the maximum displacement was0.036 mm.The maximum equivalent stress of the new posterior lateral anatomical plate at 500 N was 8.757 MPa.The maximum equivalent stress of the new posterior lateral anatomical plate at 1000 N was 17.514 MPa.The maximum equivalent stress of the new posterolateral anatomical plate at 1500 N was26.271 Mpa.The stress of screws in various parts of the new posterolateral anatomical plate was gradually increased under different loads at 500 N,1000N and 1500 N.The maximum equivalent stress of the screw at the 500 N was 9.143 MPa.The maximum equivalent stress of the screw at the 1000 N was 18.287 MPa.The maximum equivalent stress of the screw at the 1500 N was 27.430 MPa.3.Biomechanical experimental results:(1)Posterolateral fracture block vertical displacement in the two groups under different stress contrast:when the load stresswas at 500 N,posterolateral fracture block displacement of the new type plate fixation group was(0.574±0.017)mm,posterolateral fracture block displacement of the lateral "L" type plate fixation group was(0.980±0.037)mm,the difference comparison between the two groups was statistically significant(t=34.104,P=34.104).When the load stress was at 1000 N,the posterolateral fracture block displacement of the new plate fixation group was(1.097±0.052)mm,and the displacement of the lateral "L" type plate fixation group was(1.577±0.030)mm,the difference comparison between the two groups was statistically significant(t=27.597,P=0.000).When the load stress was at 1500 N,the displacement of the new plate fixation group was(1.618±0.117)mm,and the displacement of the lateral "L" type plate fixation group was(2.260±0.073)mm,the difference comparison between the two groups was statistically significant(t=16.166,P=0.000).(2)Internal fixation failure load contrast:Failure load of new type plate fixation group was(2793 ± 124)N,while the lateral "L" type plate fixation group failure load was(1947 ± 130)N.The difference comparison between the two groups was statistically significant(t=-16.308,P=0.000).Conclusion:1.This study through using the finite element analysis software designed a new type posterior lateral anatomical plate for the fixation of posterolateral tibial plateau fracture.At 500 N,1000N and 1500 N three different loads,the maximal displacement of the new type plate internal fixation of fracture block was less than 3 mm,which was acceptable in the tibial plateau fractures for the articular surface steps.Stress distribution of internal fixation was uniform and the equivalent stress of each part of the plate was less than 600 MPa,lower than the maximum yield stress of titanium alloy.It is indicated that the new plate is stable in the fixation of posterolateral tibial plateau fracture.And there isn't obvious stress concentration and stress occlusion.2.Biomechanical testing has compared the stability and maximum failure load of new plate and lateral "L" plate,in the fixation of posterolateral tibial plateau fracture.The results show that the biomechanical properties of new plate fixation in fracture block displacement and maximum failure load are better than the lateral "L" plate fixation.