Photoelastic Analysis of the Vertebral Fixation System Using Different Screws

  • S. F. Fakhouri Department of Biomechanics, Medicine and Rehabilitation of the Locomotor Apparatus Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, Brazil
  • M. M. Shimano Department of Mechanical Engineering Federal University of Triangulo Mineiro, Brazil
  • C. A. Araujo Laboratory of Mechanical Projects Professor Henner Alberto Gomide School of Mechanical Engineering of Federal University of Uberlandia, Brazil
  • H. L. Defino Department of Biomechanics, Medicine and Rehabilitation of the Locomotor Apparatus Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, Brazil
  • A. C. Shimano Department of Biomechanics, Medicine and Rehabilitation of the Locomotor Apparatus Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, Brazil
Keywords: photoelasticity, biomechanics, pullout strength, vertebral fixation system


The purpose of this study was to compare using photoelasticity, the internal stresses produced by two types of pedicular screws (Synthes™) with three different diameters, when submitted to different pullout strengths. The fringe orders were evaluated around the screws using the Tardy compensation method. In all the models analyzed, the shear stress was calculated. Results showed that, independently of the applied load, the screw of smaller outer diameter had larger values of shear stress. According to the analysis realized, we observed that the place of highest stress was in the last thread, close to the head of the screws.


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