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The influence of the "penetration-" and the "filling-ratios" on the pull-out strength of transpedicular screws

    Research output: Contribution to journal › Article › peer-review

    Abstract

    The stress field developed in the human lumbar vertebral bone due to the presence of transpedicular fixation screws is studied in an attempt to quantify the force required to pull the screw out of the bone. The study is focused on the pure pull-out phenomenon, namely the case in which the external loads act parallel to the longitudinal axis of the screw. The parameters considered are the penetration ratio, i.e. the ratio of the screw length divided by the distance from the posterior pedicle entrance site to the anterior vertebral cortex, and the filling ratio, i.e. the ratio of the major diameter of the screw divided by the transverse diameter of the pedicle. The study is carried out numerically with the aid of the finite element method. The analysis takes into account both the variation of the mechanical properties of the bone in terms of the distance from its surface as well as the geometrical details of a typical transpedicular screw. The results of the analysis are compared with existing experimental data from the literature and the comparison is very satisfactory.

    Original languageEnglish
    Pages (from-to)283-300
    Number of pages18
    JournalJournal of Mechanics in Medicine and Biology
    Volume9
    Issue number3
    DOIs
    Publication statusPublished - Sept 2009

    Keywords

    • Filling ratio
    • Finite element method
    • Penetration ratio
    • Pull-out force
    • Transpedicular screws

    ASJC Scopus subject areas

    • Biomedical Engineering

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