Tribocorrosion by Anna Igual Munoz & Nuria Espallargas & Stefano Mischler

Author:Anna Igual Munoz & Nuria Espallargas & Stefano Mischler
Language: eng
Format: epub
ISBN: 9783030481070
Publisher: Springer International Publishing

Figure 5.6 shows an example of three different experimental configurations for biomedical applications. The goal is to characterize and determine the tribocorrosion response of hip joint implant materials. The system can only be tested under real conditions by monitoring the state of the implant in a patient. Of course, in this specific case, the operating conditions are just partially known (as an example one could determine the loading, dynamic and kinematics, by a motion study) but the chemical and/or electrochemical conditions of the joint can be hardly determined. In addition, the system (human body) cannot provide output information such as friction. Therefore, this case of real test can only be carried out by analysis of the loading conditions, in situ visualization of the implant and surrounding tissues through NMR techniques and by analysing the implant once extracted from the patient. The study of explants would allow identifying the cause of failure and the main degradation mechanism occurring in the system after it fails.

Biomedical implants can also be tested using instruments such as hip simulators. In this case, it is possible to reproduce the operating conditions of the hip prosthesis by testing the real components, but in simulated body fluids. In this case, the geometry, the material and the loading conditions can be reproduced but not the chemical composition of the environment, neither the mechanical interaction between the body elements (bones, tissues) with the implant itself. These tests allow for checking the behaviour of the components used in the real geometry of the hip joints and obtaining actual output data, although the limitation of the unknown properties of the environment makes the obtained output difficult to extrapolate to the real practice.

Finally, the materials used in the fabrication of hip implants can be tested in laboratory tribometers, which allow an almost perfect control of the operating conditions in an idealized way. With the output obtained from these tests, the material behaviour can be defined under a relatively high variety of conditions (chemical, electrochemical and mechanical) and also theoretical models allowing for scale up can be developed (as clearly shown in Cao et al. [17] work, Chap. 4).

Finally, the selection of the type of test depends on several factors including the availability of the equipment and cost.

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