| Research objectives:1.To establish a model of femoral stem oblique fracture and compare the mechanical performance of four-dimensional structured splints with conventional locking splints for fixing femoral stem oblique fractures by three-dimensional finite element analysis method.2.To investigate the feasibility of fixing oblique fractures of the femoral stem by comparing the biomechanical strength of the four-dimensional structural splint with that of the conventional locking splint on the oblique fracture model of the femoral stem through in vitro biomechanical tests.Research methods:1.Finite element analysis:A healthy adult female volunteer was selected to obtain the femur CT data of the volunteer,and the oblique fracture model of the femoral shaft was established by Mimics,a medical image reconstruction software.The experimental group and the control group were respectively subjected to internal fixation with four dimensional structural bone plates with different gaps and conventional locking bone plates.Then,the structures of femur and bone plate are endowed with real material properties.Load tests under 600 N axial compression,250 N internal and external "four-point" bending and 15000N·mm torsion were simulated,and finite element analysis was carried out.The deformation distribution and peak value,equivalent elastic strain distribution and peak value,equivalent stress distribution and peak value,stress intensity distribution and peak value were observed under different load modes.2.In vitro biomechanical loading test:The 18 standard synthetic femurs were randomly divided into 2 groups(n=9).Then,according to the AO classification(AO-A2)standard,the middle part of the synthetic femur was truncated diagonally to make the oblique fracture model of the femoral shaft with the same position and shape.The experimental group was fixed with four dimensional structure bone plate,and the control group was fixed with conventional bone plate.In vitro loading experiments of axial compression,internal and external four-point bending and torsion were carried out.The independent sample t test method was used to observe and compare the compressive stiffness,bending stiffness,torsional stiffness and displacement of the whole sample between the two groups.Results:1.Finite element analysis results:(1)In the 600 N axial compression load mode,the overall deformation of the femur-joint plate model was 1mm 4-D model < 0mm 4-D model < 0.5mm4-D model < conventional locking model,while the deformation of the screw,joint plate,and slider in each group of models was the smallest in the0 mm 4-D model.The overall equivalent elastic strain of the femur-joint plate model was < 1 mm 4-D model < 0 mm 4-D model < 0.5 mm 4-D model for the conventional locking model,but the equivalent elastic strain of the screw,joint plate,and slider was the largest for the conventional locking model in each group of models.The overall equivalent elastic strain of the femur-joint plate model was 0.5mm 4-D model < 0mm 4-D model< 1mm 4-D model < conventional locking model,and the equivalent elastic strain of the screw,femur,and slider in each group of models was the smallest in the 0mm 4-D model.The overall stress intensity of the femoral-joint plate model was 0.5mm 4-D model < 0mm 4-D model < 1mm 4-D model < conventional locking model.(2)Under the 250 N internal and external "four-point" bending load mode,the overall deformation of the femor-bone plate model was 1mm four-dimensional model < 0mm four-dimensional model < 0.5mm four-dimensional model < conventional locking model,and the deformation of the screw,bone plate,femur and slider in the 1mm four-dimensional model was the minimum.The overall equivalent elastic strains of the femur-joint plate model were 1 mm 4-D model < 0 mm 4-D model< conventional locking model < 0.5 mm 4-D model.The strains of the femur in the 1 mm 4-D model were the smallest,the strains of the screw were the smallest in the 0 mm 4-D model,and the strains of the joint plate were the smallest in the conventional locking model(0.00030422),while the strains of the joint plate in the 1 mm 4-D model(0.00046102)was close to it.The overall equivalent force of the femoral-adjacent plate model was < 0.5mm 4-D model < 0mm 4-D model < 1mm 4-D model for the conventional locking model,while the smallest equivalent force was 0mm4-D model for the screw and femur,and the smallest equivalent force was0.5mm 4-D model for the adductor plate and slider.The overall stress intensity of the femur-joint plate model was conventional locking model< 0mm 4-D model < 0.5mm 4-D model < 1mm 4-D model.(3)Under the 15000N·mm torsional load mode,the overall deformation and equivalent elastic strain of the femur-joint plate model were 1mm4-dimensional model < conventional locking model < 0mm 4-dimensional model < 0.5mm 4-dimensional model,and the deformation and equivalent elastic strain of the screw,joint plate,femur,and slider of the 1mm4-dimensional model were the smallest.The overall equivalent stresses of the femoral-joint plate model were < 1mm 4-D model < 0mm 4-D model <0.5mm 4-D model for the conventional locking model,but the equivalent stresses of the screw,joint plate,femur,and slider were all the smallest for the 1mm 4-D model.The overall stress intensity of the femoral-joint plate model was 1mm 4-D model < conventional locked model < 0.5mm 4-D model< 0mm 4-D model.2.In vitro biomechanical loading test results:(1)Under the axial compression of 1400 N,the compression stiffness of the four-dimensional bone plate group(577.97±5.71)N/mm)was higher than that of the conventional locked bone plate group(529.53±20.26)N/mm,and the difference was statistically significant(P < 0.05).The displacement of the four-dimensional structure plate group was(3.67±0.42)mm > that of the conventional locking plate group(3.27±0.56)mm,and the difference was not statistically significant(P > 0.05).The deformation and strain of fracture end in the four dimensional structure plate group were smaller than those in the conventional locking plate group.(2)Under the internal and external four-point bending test of 500 N,the bending stiffness of the four-dimensional bone plate group(469.63±89.42)N/mm was lower than that of the conventional locked bone plate group(542.50±43.22)N/mm,and the difference was not statistically significant(P > 0.05).The displacement of the four-dimensional structure plate group was(1.60±0.17)mm > that of the conventional locking plate group(1.23±0.06)mm,and the difference was statistically significant(P < 0.05).(3)Under the 15N·m static torsion test,the torsional stiffness of the four-dimensional structure plate group(1.05±0.08)N/mm was lower than that of the conventional locking plate group(1.12±0.13)N/mm,and the difference was not statistically significant(P > 0.05).The angular displacement of the four-dimensional structure plate group(15.90±1.25)deg was higher than that of the conventional locking plate group(14.93±0.95)deg,with no statistical significance(P > 0.05).Conclusion:Under three different loads of static axial compression,static internal and external four-point bending,and static torsion,the four-dimensional structure bone plate shows reliable biomechanical stability,which can meet the basic mechanical property requirements for the treatment of FSF,and has certain effectiveness and feasibility in the treatment of FSF,these conclusions provide important biomechanical basis for further animal experiment and clinical application research. |
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