Abstract
Introduction
Hip modular implants provide real advantages to patients and surgeons: the opportunity to restore the natural anatomy, to correct discrepancy is positioning, etc…
Nevertheless, recent publication showed the weakness of these prostheses. A review of the literature on this phenomenon is carried out, and shows that fretting fatigue and fretting wear is often pointed out to explain these issues.
Objectives
The goal of this project is to optimise these products, carrying out advanced simulations with criterion that allow to compare the behaviour regarding fretting in the modularity.
Methods
Different parameters are considered:
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Geometric (length, width and height of the neck basis)
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Material (CrCo, TA6V4)
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Tribology (different friction coefficient to simulate different roughness)
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Environmental (load impaction)
Several FEA simulations are carried out (Fig 1) in order to assess the sensitivity of these parameters. The choice of the criterion is of course an important point, and 2 main criterions are proposed to compare the designs regarding fretting wear and fretting fatigue.
The experiment plan is exploited in order to find the best solutions for next designs.
Fatigue tests are also carried out in ISO 7206–6 conditions (fig. 2): failure analyses are conducted and results are compared to simulation.
Results and conclusion
To be correctly simulated, a failure of fretting fatigue need to be considered with appropriated criterion: FEA with Smith Watson Topper, a multi axial fatigue criteria, is an efficient way of improving the modularity design. The study also allows us to identify important parameters, like load impaction: it appears that a load too high or too low conducts to non-optimum behaviour. Similarly, simulations shows that a friction coefficient about 0, 4 leads a good behaviour regarding fatigue fretting as well as fatigue wear.
