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    STP1591

    Factors Related to Imprinting Corrosion in Modular Head-Neck Junctions

    Published: 29 January 2016


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    Abstract

    Varying degrees of corrosion have been seen at the head-neck junction of modular femoral arthroplasty components. Historically, smooth finishes were applied to both the male and female tapers and most work describing corrosion (e.g., fretting, intergranular attack, etc.) investigated such smooth junctions. To decrease the risk of fracture of ceramic heads, microgrooving or threading has been applied to the majority of total hip arthroplasty male stem tapers. Retrieved metal femoral heads and taper sleeve adaptors mated with microgrooved tapers have been observed to have imprinting or corrosion on the female side of the taper, which directly mirrors the male thread pattern. We reviewed a series of clinically retrieved modular heads employing a taper sleeve adaptor and consistently observed such imprinting corrosion. Although imprinting corrosion of some degree was uniformly observed at the sleeve-to-taper femoral interface, neither corrosion nor imprinting was observed at the smoother sleeve-to-head interface. Furthermore, little to no evidence of sustained micromotion was observed at either of the taper interfaces, suggesting that the intended role of the threads to limit gaps or motion was achieved. We propose that imprinting is primarily driven by electrochemical processes facilitated by the greater geometry factor associated with the 10–15 μm thread depth on the grooved male tapers as compared with the approximately 1–2 μm depth observed at the smooth head-to-sleeve interface. Larger geometry factors are associated with decreased crevice pH, which may drive the rate of electrochemical corrosion. Estimates suggest that although imprinting corrosion is a common finding in heads mated with grooved tapers, the overall volumetric material loss is small. Although the presence of imprinting is indicative of a corrosion process, the lack of associated fretting motion may be indicative of a well-locked construct relatively sealed against particulate transport.

    Keywords:

    taper corrosion, metrology, arthroplasty, imprinting corrosion


    Author Information:

    Van Citters, Douglas W.
    Thayer School of Engineering at Dartmouth, Hanover, NH

    Martin, Audrey J.
    Thayer School of Engineering at Dartmouth, Hanover, NH

    Currier, John H.
    Thayer School of Engineering at Dartmouth, Hanover, NH

    Park, Sang-Hyun
    UCLA, Orthopaedic Institute for Children, Dept. of Orthopaedic Surgery, Los Angeles, CA

    Edidin, Avram A.
    Relievant Medsystems/Drexel Implant Research Center, Redwood City, CA


    Committee/Subcommittee: F04.22

    DOI: 10.1520/STP159120140138