Biomechanical analysis of pedicle screw instrumentation systems in a corpectomy model

R. B. Ashman, R. D. Galpin, J. D. Corin, C. E. Johnston

Research output: Contribution to journalArticlepeer-review

130 Scopus citations


Five different spinal implants, all using pedicle screw attachment to vertebrae, were examined in a one above/ one below corpectomy model, to determine 1) the relative stiffness of each construct, 2) the stresses generated in the implant during loading, and 3) the relative fatigue susceptibility of each implant. Resiults indicated that the relative axial and torsional stiffnesses were similar for all the implants tested (DKS/Zielke, VSP/Steffee, AO Fixator Interne, Luque plate, AO Notched plate). Hence, each of the devices impart approximately the same stability to the spine in this highly unstable model. Stresses measured at the root of the pedicle screws were found to exceed the endurance limit of stainless steel In those systems in which the pedicle screws were attached rigidly to the plates (VSP/Steffee, AO Fixator Interne). Good agreement was found between the measured stresses and stresses derived from static calculations. Comparisons between the stresses from each implant gave a relative measure of fatigue susceptibility that was validated by in vitro cyclic testing, implants with stresses exceeding the endurance limit failed during the cyciic test.

Original languageEnglish (US)
Pages (from-to)1398-1405
Number of pages8
Issue number12
StatePublished - Dec 1989


  • Biomechanical testing
  • Burst fracture
  • Pedicle screw
  • Spine implants

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Clinical Neurology


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