Finite Element Analysis Of Vertebroplasty Biomechanics Based On Abaqus

Objective: To establish three types of three-dimensional finite element model by Abaqus,to obtain a comparison of the stress changes in the centrum under different states(normal vertebral body,osteoporotic vertebral compression fracture,vertebroplasty).Methods: Nine cadaveric lumbar vertebrae were scanned,meeting the inclusion criteria.The original CT data were collected.The 3D geometric model of L2-L3 vertebrae and intervertebral disc was constructed by importing the DICOM format into the medical image control system(Mimics15.0).The constructed geometric model was imported into Geomagic Studio12.0,a reverse processing software produced by Raindrop Company of USA,to smooth surfaces.Finally,Abaqus6.13 was introduced to carry out finite element analysis of the plane model.According to the different magnitude and direction of the force applied by Abaqus,five kinds of physiological activities of lumbar vertebrae(standing,flexion,extension,lateral flexion,rotation and rotation)were simulated,and the stress on the intervertebral disc and adjacent vertebrae were recorded in these states.The biomechanical tests of the lumbar vertebrae of the cadaveric specimens were performed at the same time.Combining the two sets of data,the reliability of the model was verified.The osteoporotic vertebral compression fracture(OVCF)model was reconstructed by changing the parameters of the established finite element model(Young's modulus,Poisson's ratio),and then the virtual bone cement was filled by simulating the percutaneous kyphoplasty(PKP)operation.According to different injection pressure,injection methods and dosage of bone cement,the stress changes and bone cement leakage were evaluated.So that we established a digital PKP evaluation system.Results: This model was similar to the physiological function of cadaveric specimens.After PKP,the stress reduced significantly on the L2 fracture vertebral endplate.There was no significant difference between the stress changes and the puncture mode of bone cement(all P > 0.05),the distribution of bilateral injection of bone cement was more uniform.With the increase of injection dose of bone cement,the stress of L2 fracture vertebral endplate decreased gradually(all P < 0.05),the distribution of bone cement is more concentrated.Yield point appears when 8ml cement is injected.There was no significant difference between the stress changes and the injection pressure of bone cement(all P >0.05),with the increase of pressure,the distribution of bone cement was more dispersed.After PKP,the stress of the inferior end plate of the upper centrum decreased and the stress of the upper end plate of the inferior centrum increased.Conclusion: The finite element model simulates the operation of PKP.The puncture mode does not affect the efficiency of the operation,compared with unilateral puncture,bilateral puncture can avoid the stress bias caused by uneven distribution of bone cement.To obtain better vertebral strength and stiffness,4ml bone cement filling should be selected,It can avoid fracture caused by 8ml cement reaching the yield point of adjacent centrum,and 2ml bone cement is insufficient to restore the physiological curvature of vertebral body.To avoid the risk of bone cement leakage,low pressure filling should be chosen.The evaluation system can reflect the changes of vertebral stress in PKP operation.To work for the operation planning and clinical work.