A historical review of both laboratory and clinical wear performance of orthopaedic bearing materials and surfaces is presented. Over time, laboratory wear tests have been developed and used more frequently to support the introduction of new material couples. Historically, these methods have been unreliable, and, despite recent improvements, predicting clinical wear performance is still a challenging task. Orthopaedic wear is a highly multi-factorial process—successful simulation depends on the identification, modeling, and control of many critical factors. Clinical results themselves are highly variable, complicating efforts to establish clinical validation criteria for test methods. It is recommended that improvements be made in identifying the appropriate clinical targets for laboratory tests, and that increased effort be directed toward the optimization and standardization of wear test methods.

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Modular connections have been commonly and successfully utilized in orthopaedic implant systems for the last 15 or so years, particularly at the head/neck junction in total hip arthroplasty (THA). However, recent retrieval studies have shown that some of the tapered junctions between femoral heads and stems in total hip arthoplasty can be prone to fretting corrosion, and may be a cause for concern in the longevity of implants. Fretting corrosion, which may release metallic products (particulate debris and ions) into the joint space, is a complex phenomenon in which the interplay between mechanically induced interfacial micromotion (fretting) and electrochemical corrosive activity play an important role, along with materials selection and processes. This suggests that interfacial fretting corrosion at modular implant interfaces can be significantly affected by the design variables of the modular junction. The working hypothesis of this study was that different designs of the modular head/stem combination of femoral hip prostheses exhibit different release of fretting corrosion metal products during fatigue testing used to simulate ten years of in vivo service. Three designs of femoral head (Co-Cr-Mo alloy) and stem (Ti-6Al-4V alloy) combinations were investigated in this study. The study included detailed taper metrology followed by environmental fatigue testing of the tapered junctions. The results of this study showed that important taper design differences do exist in the three constructs tested, and these differences manifested in different fretting corrosion behavior.

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