| Objective: Tibial,as one of the shinbone,located in the medial leg,plays an important roles on upper weight,as the main load-bearing bone in the leg.Tibial fractures are the most common long bone fractures with an incidence of about 26/10 0000.Male tibial fracture probability is 3 times higher than women,the average age of the male patients is about 37 years old.Fractures of the tibia in men are common in young people and are generally high energy trauma,such as motor vehicle accidents.Because of the anatomical structure of the tibia and the specificity of the surrounding soft tissue,and the fractures mostly caused by violent injure,Tibial fractures are mostly open or comminuted fractures,and prone to infection,delayed union or nonunion,and eventually lead to osteomyelitis,bone necrosis,and ultima need tobone extension treatment or even amputatio.Therefore,the clinical treatment of severe open fractures of the tibia and fibula is confronted with many difficulties.With the deeply research on the biomechanics of the tibia and the rapid development of the surgical technique in the Department of orthopedics,the prognosis of the tibial fractures has been greatly improved and the quality of life of the patients has been improved.At present,for the treatment of severe open fractures of tibia and fibula,most advocate that the external fixator can effectively fix the fracture end in the early time,which provides favorable conditions for closed wound,the second stage according to the soft tissue conditions to choose the internal fixation or external fixator as the final fixation.The objective of this study was to explore the effects of external fixation systems with two different modulus of elasticity on the stress,and discuss its distribution at tibial fracture through biomechanical testing,to provide theoretical basis for selecting suitable external fixation materials and devices.Methods: 8 sets of adult cadaveric tibia were selected,and the middle of tibias was sawn with an electric saw to form tibia facture models.After anatomic reduction,the fracture samples were fixed with different external fixators group.A group:high elastic modulus(elastic modulus of 110 GPa)which was made of aluminum alloy material,B group :the low elastic modulus(elastic modulus of 11.4 GPa)made of carbon fiber resin material.Then the model is placed on the biomechanics experiment machine,with a line respectively axial compression stress,torsion experiment and four-point bending experiments,of the two kinds of material of external fixator for biomechanical research.Results:1 Axial compression pressure experimental results:In the axial compression stress test,the load pressure is 0-1000 N.Within the scope of the load,the fracture displacement and load pressure curve of straight line,reacted a linear relationship between the two groups.Two groups of specimens displacement increases along with the increase of pressure.Under the maximum axial pressure,the displacement of polymer external fixation group was10.164±0.090 mm,the displacement of traditional metal external fixator group was9.633 ± 0.042 mm.The displacement of two groups of different materials of external fixator fracture model difference was statistically significant.(Z=-8.627,P<0.01).The stiffness of the polymer external fixator group was142.139±31.322,and the stiffness of the traditional metal external fixator group was 108.310±13.019,and there was no significant difference in the stiffness of the external fixator between the two groups(Z=-1.443,P=0.149>0.01).2 Torsion test results:in the torsion test,The load torque was 0-4N.m.Within the scope of the load,the fracture roration and load torque curve of straight line,reacted a linear relationship between the two groups.Two groups of specimens rotation increases along with the increase of torque.Under the maximum torque,the rotation of polymer external fixation group was 8.302±0.031,the rotation of traditional metal external fixator group was 6.161±0.052.The ratation of two groups of different materials of external fixator fracture model difference was statistically significant(Z=-8.617,P<0.01).The stiffness of the polymer external fixator group was 1.712±0.243,and the stiffness of the traditional metal external fixator group was 1.446±0.530,and there was no significant difference in the stiffness of the external fixator between the two groups(Z=-0.577,P=0.564>0.05).3 Four point bending test results:in the four point bending test,The load pressure was 1000 N.Within the scope of the load,the fracture dispiacement and load pressure curve of straight line,reacted a linear relationship between the two groups.Two groups of specimens dispiacement increases along with the increase of pressure.Under the maximum pressure,the dispiacement of polymer external fixation group was2.909±0.292,the dispiacement of traditional metal external fixator group was 2.256±0.052.The dispiacement of two groups of different materials of external fixator fracture model difference was statistically significant(Z=-8.617,P<0.001).The stiffness of the polymer external fixator group was 496.647±63.454,and the stiffness of the traditional metal external fixator group was 547.577±35.944,and there was no significant difference in the stiffness of the external fixator between the two groups(Z=-1.732,P=0.083>0.05).Conclusion: The use of traditional metal external fixator and polymer external fixator for the treatment of tibial fractures both have good biomechanical stability.The use of polymer materials in the treatment of open tibial fractures with external fixation compared with traditional metal external fixation,more conducive to stress conduction,meet the biodynamical requirement,which can effectively avoid stress shielding effect,promote fracture healing.At the same time can reduce the rotation torque,make the fracture is more stable,but also To a certain extent,reduce the bending load caused by the stress concentration phenomenon.It may reduce the bone absorption around the nail or half needle loose,which are the complications of clinical use of external fixator.Therefore,its mechanical performance is better,can promote the use from the Angle of biomechanics. |
PDF Full Text Request