Implants tribological conditions

Tribological contacts exposed to corrosive environments are found in many industrial situations such as mineral processing, metal forming, orthopaedic implants and marine equipment. Under these conditions the contact materials are subject to both mechanical and chemical solicitations. The rate of material degradation cannot be predicted simply by adding the wear rate in absence of corrosion to the corrosion rate in absence of wear. The reason is that corrosion and wear do not proceed independently and synergistic effects usually result in accelerated degradation (tribocorrosion). 

A representative viscosity of 0.9 mPas for the 25% bovine serum frequently used in simulator studies has been suggested by Dowson (2002). It is important to distinguish between the effective viscosity of the joint fluid bafiiing implants in vivo and that of the fluids used in simulator tests. The later is important in the analysis of experimental data on wear, friction and lubrication undo carefully controlled conditions, while the fr mer determines the tribological performance of implants in the body. The viscosity of synovial fluid from arthroplasty patients is probably somewhat higher than that of most of the lubricants adopted in simulator tests, as pointed out by Mazzucco et al (2002), and therefi)re a representative value of between 1.5 and 5 mPas appears to be reasonable fi>r in-vivo evaluations. 

---