Finite Element Analysis Of Vertebroplasty After Posterior Fixation And Visualization Of The Preoperative Design

Purpose:(1) To reconstruct the3D model and finite element model of the thoracolumbar spine (T10-L2) and make the validation.(2) To analysis the influence of the vertebroplasty on the property of thoracolumbar burst fracture with transpedicular fixation by finite element models.(3) To investigate the visualization of the preoperative design and its application in thoracolumbar fractures by posterior instrumentation.Methods:(1) Computed tomography scans performed on T10-L2motion segment of a young healthy subject were used to establish the normal finite element model. Validation was conducted by comparing the range of motion with other studies.(2) By simulating transpedicular fixation and vertebroplasty, eight finite element models of the T11～-L1segments for transpedicular fixation, and fixation plus three kinds of vertebroplasty were established. Based on the three-column theory, the superior1/2cancellous bone of the T12body was removed for burst fracture model one. both cortical and cancellous bone were removed for burst fracture model two. Both endplates were given the material property of the cancellous bone, and some ligaments were removed. Biomechanics were evaluated when these models were under compression, anteflexion. extention. laterofiexion. and rotation.(3) Reconstruct the fractured spine with the CT data of ten patients treated in Tianjin Hospital from March to June in2012by the MIMICS software. Make sure the location and extent of fractures, measure some impantent parameters of the pedicle such as hight, width, angle and the length of the screw, locate the input point of the screws and measure the defect of fractured vertebrea.Result:(1)I successfully constructed the normal finite element model and validation test showed that the model could be used in the later biomechanics test.(2) The stress of the instrumentations, the inferior endplate of T11and superior endplate of L1was not decreased for burst fracture model one while it was significantly decreased for burst fracture model two by50%for screws and40%for rods. Different kinds of vertebroplasty had similar effect. The stress of inferior endplate of T11for fracture model increased by24%. and43%for superior endplate of L1.(3) We can get total understanding about fractures of the spine and enough paremeters of the pedicle before operation. The outcomes of the posterior fixation are perfect without any complications.97.8%of the bone defects were filled from2.63cm3before operation to2.57cm3after operation.Conclusion:(1) I successfully constructed the normal finite element model and validation test showed that the model could be used in the later biomechanics test.(2) For severe burst fracture, the vertebroplasty could significantly lower down the stress of the spine and instrumentation after transpedicular fixation, which could prevent complications.(3) Visualization of the preoperative design can play an impantant role in the personal surgery program and improve the clinical outcome.