Finite Element Analysis Of The Influencing Factors Of Adjacent Vertebral Fractures After PKP For Vertebral Compression Fractures

Objective:During percutanouskyphoplasty(PKP)of osteoporotic vertebral compression fractures(OVCFs),the finite element analysis method was used to evaluate the physiological anatomy of recurrent fractures after PKP and the effect of bone cement on the biomechanical changes of adjacent vertebral bodies.Among the influencing factors,which factor is the main factor.Methods:A healthy volunteer with no history of spinal trauma,spinal deformity,spinal pain,or degenerative changes was screened by Siemens GE64-slice spiral CT tomography.CT scan data was imported into Mimics 21.0 software in DICOM format.Through the set image threshold,layer by layer segmentation processing was performed to eliminate the surrounding soft tissue shadow and artifact,and STL format model was generated.In this study,each vertebra was treated as an independent image for operation,and the required model was obtained by layer segmentation technology,during which a lot of manual operation was paid.The Geomagic Wrap software was used to remove features,remove studs,define boundaries,generate curved sheets,etc.Solid Works 2017 software was used to define the structure of the articular process cartilage,endplate and intervertebral disc system.Finally,Workbench 17.0 software was used for grid division,ligament simulation,and material properties.A three-dimensional finite element model of osteoporosis was established for T10-L3,and its material properties were assigned to generate an osteoporotic thoracolumbar vertebral body model,which was set as the control group.Then,two cylinders were placed in L2 vertebral body,and the most commonly used polymethyl methacrylate(PMMA)bone cement material was allocated to simulate the PKP operation of L2 vertebral body,and the postoperative model of L2 vertebral body PKP was generated,which was set as the experimental group.The 1200 N vertical compression load was applied to all models,and the effects of physiological anatomic factors and bone cement factors on postoperative recurrent fractures were evaluated by observing the changes of the first vertebral segment with compression fracture before and after PKP and the changes of Von Mises stress on the vertebral body with compression fracture.Results:(1)In the osteoporotic vertebral model without bone cement injection,the Von Mises stress on the associated structure of the T12 vertebral body was greater and more concentrated,resulting in earlier and more likely fracture.(2)The maximum Von Mises stress on cortical bones of all vertebral bodies was transferred from T12 to L1,and the maximum Von Mises stress on other vertebral bodies was still the maximum,but the maximum Von Mises stress on related structures of T12 vertebral bodies showed a decreasing trend.However,the related structures of the adjacent vertebra(L1,L3)showed an upward trend,which was more obvious than that of the T12 vertebra.Among them,the cortical bone of L1 vertebral body and L1 inferior endplate had the greatest influence.Conclusions:(1)When osteoporosis patients initially develop OVCFs,physiological curve factors play a dominant role;(2)When recurrent fractures occurred after PKP surgery,both physiological curvature and bone cement affected the stress on the vertebral body,but the biomechanical change of bone cement on the adjacent vertebral body was the main factor,and the effect on the upper vertebral body was the greatest.