NUMERICAL ANALYSIS ON THE INFLUENCE OF TAPER JUNCTION CORROSION PROFILE WITH EMPHASIS ON TI-ALLOY MODULAR HIP ARTHROPLASTY

Modular designs give orthopaedic surgeons a greater flexibility to custom fit the implant to the patients bone while performing total hip arthroplasty. Titanium alloy (Ti6Al4V (ASTM F-136)) is typically used for modular hip implant stems. This highly corrosion resistant alloy forms passive surface oxide films spontaneously. However, with modular designs, micro-motion may occur at the taper junctions during mechanical loading. Crevices between the taper junctions may allow the body fluids to enter and remain stagnant. These conditions make the modular tapers susceptible to fatigue and mechanically assisted crevice corrosion. The in vivo degradation of metal alloy implants compromises the structural integrity. The influence of stress corrosion induced pits of a titanium-alloy modular implant in cement less total hip arthroplasty was numerically investigated. The effect of pit geometry parameters - cylindrical, conical, and hemispherical dimple are compared and discussed in terms of taper performance.