The use of modular head/Morse taper joints in total hip replacements has become a preferred surgical practice in consideration of the flexibility in surgical procedures and reduced inventory. The modular joints also offer an advantage in selection of appropriate material for components of a prosthesis depending upon the performance requirements. These modular joints have performed successfully in vivo for well over a decade. Recently, however, the release of fretting wear particulates from prosthetic implants in total hip arthroplasty has received greater attention, and a concern has been expressed for the modular head/taper joint to be a source of metal debris.
In this paper, an experimental setup is described for conducting fretting/corrosion fatigue testing of modular head/taper assemblies in simulated body environments. The test setup consisted of a special cell designed to contain simulated body environment and to retain all particles greater than 0.20μm, generated due to fretting fatigue. For this purpose, in-line filters were used and the environmental chamber was made of acrylic material to avoid any contamination. The test environment was aerated Ringer's solution circulated in a closed loop at 37°C. The fatigue load was applied on the head in 15°C mediolateral anatomic orientation. The functional capabilities of this setup was demonstrated by testing alumina ceramic and cobalt-chromium-molyb-denum femoral heads fitted on titanium alloy tapers, at a fatigue load of 5.34 kN and a stress ratio of 0.1. The results are summarized in terms of characterization and quantification of any particulates generated, and surface topographical changes on both head and taper contact surfaces.