title: [Finite element analysis of stress changes of posterior spinal pedicle screw infixation].
abstract: OBJECTIVE
  To evaluate the mechanical response of L3-L4 segment after posterior interfixation with a transpedicle screw system.
  
  
  METHODS
  Spiral CT machine was used to conduct continuous parallel scan on the L3-L4 section of a 40-year-old healthy male Chinese. The image data thus obtained were introduced into MIMICS software to reconstruct the 2-D data into volume data and obtain 3-D models of every element.. Pro/3-D model construction software system was used to simulate the 3-D entity of L3-L4 fixed by screw robs through spinal pedicle via posterior approach that was introduced into the finite element software ABAQUS to construct a 3-D finite element model. The stress changes on the vertebrae and screw under the axial pressure of 0.5 mPa was analyzed.
  
  
  RESULTS
  Under the evenly distributed pressure the displacement of the L4 model was 0.00125815 mm, with an error of only 0.8167% from the datum displacement. The convergence of the model was good. The stress of the fixed vertebral body, intervertebral disc, and internal fixators changed significantly. The stress concentration zone of the intervertebral disc turned from the posterolateral side to anterolateral side. The stress produced by the fixed vertebral bodies decreased significantly. Obvious stress concentration existed in the upper and lower sides of the base of screw and the fixed screw at the upper vertebral body bore greater stress than the lower vertebral body.
  
  
  CONCLUSIONS
  Integration of computer aided device and finite element analysis can successfully stimulate the internal fixation of L3-IA visa posterior approach and observe the mechanic changes in the vertebral column more directly.
authors.affiliation: Department of Orthopedics, Peking Union Medical College Hospital, Peking Union Medical College, Beijing 100730, China.
authors.forename: Jia-Zhi
authors.initials: JZ
authors.lastname: Yan
authors.forename: Zhi-Hong
authors.initials: ZH
authors.lastname: Wu
authors.forename: Ri-Xin
authors.initials: RX
authors.lastname: Xu
authors.forename: Xue-Song
authors.initials: XS
authors.lastname: Wang
authors.forename: Ze-Jun
authors.initials: ZJ
authors.lastname: Xing
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhao
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Zhang
authors.forename: Jian-Xiong
authors.initials: JX
authors.lastname: Shen
authors.forename: Yi-Peng
authors.initials: YP
authors.lastname: Wang
authors.forename: Gui-Xing
authors.initials: GX
authors.lastname: Qiu
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001863:Bone Screws; D020342:Finite Element Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male