STP1563: The Tribo-Corrosion of Nitinol in Pedicle Screws

    Reigrut, Julie L.
    Research and Development Engineer, Biocompatibility, K2M, Inc., Medical Device Testing, Biomechanics, Biomaterials Technology Laboratory, Leesburg, VA

    Schmidt, Daniel S.
    Research and Development Intern, Scanning Electron Microscopy, K2M, Inc., Medical Device Testing, Biomechanics, Biomaterials Technology Laboratory, Leesburg, VA

    Williams, Peter J.
    Research and Development Intern, EDS Analysis, K2M, Inc., Medical Device Testing, Biomechanics, Biomaterials Technology Laboratory, Leesburg, VA

    Schmidt, John A.
    Director of Biomaterials Technology, Material Science, Statistics, Metal Fatigue, K2M, Inc., Medical Device Testing, Biomechanics, Biomaterials Technology Laboratory, Leesburg, VA

    Pages: 20    Published: May 2013


    Abstract

    The use of the superelastic version of Nitinol in spinal constructs has the potential to allow increased motion adjacent to the construct. Nitinol rods were investigated for this application in conjunction with Ti-6Al-4V pedicle screws using electrochemical and mechanical testing. Nitinol underwent typical galvanic corrosion when in contact with this alloy. However, there was also an accelerated corrosion mechanism that resulted in very different surface morphology of the rods which is attributed to tribo-corrosion. When present, tribo-corrosion resulted in significantly reduced fatigue life of the rods, and a radical reduction in nickel at the corrosion site. Tribo-corrosion was not seen in every instance. This unpredictable behavior makes the material an unacceptable long-term implant material for this application in the spine.

    Keywords:

    Nitinol, galvanic corrosion, tribo-corrosion, spine, pedicle screws, contact area, fretting


    Paper ID: STP156320120041

    Committee/Subcommittee: G02.40

    DOI: 10.1520/STP156320120041


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