Tribological testing of implants-bone pair and coefficient of friction of coated knee implants

The bone-implant interface plays an important role in the osseointegration of metallic implants. While the mechanical properties of implants and bone are generally well known, the frictional properties at the bone-implant interface are much less understood despite strongly affecting post-operative integration. This application report begins with a tribological study where the coefficient of friction between hip implant materials and bone was measured in relevant physiological conditions. The report is completed by a tribological study of coated knee implants against an Ultra high molecular weight polyethylene (UHMWPE) counterbody in bovine serum

Friction between bone and hip implant shaft

The bone-implant interface (Figure 2) plays a key role in the clinical success of orthopedic and dental implants. The desired secondary stability of such implants relies on extensive osseointegration which is a direct result of the primary stability achieved during surgical implantation.

While the mechanical properties of the bone dominate the structural behavior of the bone-implant complex, friction between bone and implant may contribute to primary stability. Although frictional behavior has been explored in isolated studies, its systematic investigation is lacking. Several authors have measured coefficient of friction values ranging between 0.14 to 1.75 for a variety of test conditions (pressure, dry/liquid, material) between bone and assorted metallic counterbodies[1,2].

To fill this gap of knowledge, we investigated the influence of applied load, sliding speed, material and surface treatment on the tribological behavior of bovine bone with common metallic implant materials. These results should allow for more realistic modelling of the bone-implant interface during the primary postoperation period[3].

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