The Biomechanical Effect Of Different TSF Dynamic Configurations On Tibial Diaphysis Fracture Healing

Objective:To compare the stability of 6 different dynamic configurations of Taylor Spatial Frame(TSF)in axial compression test and torsion test by using the method of biomechanical experiment,and to explore the clinical application of TSF in the treatment of tibial diaphysis fracture with different dynamic configurations to promote the healing of fracture.Methods:6 polyethylene plastic rods from the same manufacturer were randomly divided into six groups of A~F.The external fixator selected the same material,type full rings and olive needles to eliminate the interference of the materials and other factors on the experimental results.Group A was fixed with 6 Fast-FxTM Struts.Group B was fixed with 6 Fast-FxTM Struts + 2 threaded rods.Group C was fixed with 4 Fast-FxTM Struts.Group D was fixed with 4 Fast-FxTM Struts + 2 threaded rods.Group E was fixed with 3 Fast-FxTM Struts + 2 threaded rods.Group F was fixed with 2 threaded rods.After fixation,20 mm length was cut in the middle section of PE bar to manufacture the tibia A3 fracture model according to the AO/ASIF classification standard.Fix the fracture models on the mechanical test machine.First,the axial compression test was carried out on each group of fracture models to test the displacement of fracture ends under different axial stress.After the replacement of the olive needles and bolts,the torsion test of each group of fracture models was carried out to determine the angle of the torsion at the bone fracture ends under different torque.Then the axial and torsional stiffness of this 6 groups were compared,and the biomechanical test results of different configurations were analyzed.Results:In the process of experiment,with the gradual increase of vertical load,the distance of the fracture model of each group decreased gradually,and with the increase of torque,the relative torsion angle of fracture model was also increasing.After the experiment,no damage or breakage occurred.In the Group C fracture model,when the axial loading came to 200 N,the fracture ends of the model fracture had obvious flexion deformity.Likewise in the torsion test,when loaded to 5Nm,the fracture end appeared the obvious rotation deformity.After the fixed fixture on the upper end of the machine released,the Group C fracture model even could not maintain its original configuration.The axial compression test results of other groups: the average axial stiffness of different configurations is not the same(P<0.05).The difference between Group A and Group B,Group A and Group D,Group A and Group E,Group A and Group F,Group B and Group D,Group B and Group E was statistically significant(P<0.05).There was no significant difference in axial stiffness between Group D and Group E(P>0.05).Therefore it could not considered that the axial compression stability of this two configurations was different.The torsion test results of other groups: the average torsional stiffness of different configurations is not the same(P<0.05).The difference between Group A and Group D,Group A and Group E,Group A and Group F,Group B and Group D,Group D and Group E,Group E and Group F was statistically significant(P<0.05).However,there was no significant difference in torsional stiffness between groups A and B(P>0.05).It could not considered that the anti-torsional stability of this two configurations was different.Conclusion:Our experimental results confirm that this 6 different TSF dynamic configurations have different axial stiffness and torsional stiffness.In the stability of anti axial stress,the 6 Fast-FxTM Struts + 2 threaded rods configuration is superior to the 4 Fast-FxTM Struts + 2 threaded rods configuration and the 3 Fast-FxTM Struts + 2 threaded rods configuration.The latter two configurations are superior to the 6 Fast-FxTM Struts configuration and 2 threaded rods configuration.In the stability of torsional stress resistance,there is no significant difference between the 6 Fast-FxTM Struts + 2 threaded rods configuration and the 6 Fast-FxTM Struts configuration.This two configurations are superior to the 4 Fast-FxTM Struts + 2 threaded rods configuration,and the 4 Fast-FxTM Struts + 2 threaded rods configuration is superior to the 3 Fast-FxTM Struts + 2 threaded rods configuration and the 2 threaded rods configuration,while the 4 Fast-FxTM Struts configuration has the worst stability.