STP859: Fatigue of Ball-Joint Rods for External Fixation

    Donald, GD
    Medical student, Burlington, VT

    Seligson, D
    Kosair professor and chief, University of Louisville School of Medicine, Louisville, KY

    Brown, CA
    Research assistant, University of Vermont, Hinesburg, VT

    Pages: 8    Published: Jan 1985


    Abstract

    Twenty-three Hoffmann ball-joint rods were subjected to sinusoidal loads, each at approximately constant amplitude, between ±400 and ±975 N at a frequency of 5 Hz. Ball-joint rod compliance was plotted against number of cycles for each specimen. The point of component failure was defined as an increase of compliance of 5% from its initial value. Fractographic methods were employed to substantiate a similarity of failure mode in specimens tested and a clear difference from non-tested specimens taken to failure. Experimental loads and number of cycles to failure were well within the clinical range. The fatigue limit of the ball-joint rods is less than 400 N (550 N/mm2). The likelihood of a given component failing is not predictable by inspection or manual manipulation.

    Keywords:

    fatigue (materials), ball-joint rods, external fixation, implant materials


    Paper ID: STP33249S

    Committee/Subcommittee: F04.19

    DOI: 10.1520/STP33249S


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