Fatigue Experiment And Finite Element Simulation Of Non-fusion Artificial Vertebral Body

In recent years,lumbar damage disease caused by lumbar disc herniation,tumor or trauma has become common in life.The normal movement of lumbar spine of patients is limited.Now spinal fusion is mainly used for reconstructing lumbar physiological function and mechanical properties.Although this technology can reconstruct vertebral physiological structure,it is not able to recover the original movement of vertebral bones.As a result,our research group has designed a new type of non-fusion artificial vertebral body based on the spinal biomechanics and the materials science.After implantation,the artificial vertebral body is able to reconstruct the spine structure,and maintain the basic movement of adjacent vertebral segmental.The artificial vertebral body and intervertebral are always exposed to disc axial compression,lateral bending,buckling and torsion force after implantation.Hence,it is necessary to carry out mechanical experiments and finite element simulation to check the design of artificial vertebral body.We use universal tension and compression testing machine to conduct an axial compression fatigue experiment to test the artificial vertebral body samples.Cyclic loading was carried out by sinusoidal axial pressure of 2 Hz,0.3 KN for 5 million times and the fatigue characteristics of samples are observed.In the beginning of the experiment and every 1 million loading cycles,we carry out an axial compression experiment to measure the stiffness of the samples.The artificial vertebral body samples are cleaned by ultrasonic cleaning before and after the experiment.Then their weight is measured by electron scale to test the mechanical wear.The torsion experiment was carried out with a micro controlled torsion test machine to measure the relationship of the torsional angle and the torque between the artificial vertebral body and the artificial intervertebral disc.Then a stress and strain analysis of an artificial vertebral body and disc implantation model,and fatigue analysis of artificial vertebral body and artificial intervertebral disc are conducted in ANSYS Workbench.The structure design of artificial vertebral body and intervertebral disc assembled by titanium alloy plate,column and medical silicone nucleus is reasonable.In the axial compression and torsion test,the range of motion and mechanical properties of the artificial vertebral body is similar to the original organization in vivo.After 2-3million cycles of axial compression,its performance tends to be stable.After 5 millioncycles of axial compression,failure such as cracks and damage are not detected,and the materials are wear-resisting.So the stress caused by the foreign body into the internal environment is reduced and it is far below the yield strength.Results of finite element simulation analysis has showed that the stress distribution is uniform in an artificial vertebral body displacement model.Results of fatigue analysis has showed that the artificial vertebral body has a higher fatigue life.The non-fusion artificial vertebral body structure design is reasonable,vertebral body implantation can restore the original activity of human body,It has little effect on the biomechanical properties of adjacent segments and can meet the requirements of human long-term implantation.