Computational models for biological tissues and biomedical implants

This paper aims at showing that the finite element method is the most important numerical tool to analyse bio‐solids or bio‐fluids because of the constitutive complexity and unusual clinical input data and requirements involved. These features are absolutely mandatory and modify the mentality of an expert of FEM when he wants to contribute really to the progress of medical practice in their several forms, from biological basis to the surgical assistance. In this context, a clear view of the hierarchic importance of the phenomena involved is necessary to reply correctly to medical operators and to choose the right level of scale. While a scholarly culture of FEM and relative developments have to appeal the attention of biomedical engineers, at the same time their attention mainly is focused on the problem to solve, which must be validated clinically and experimentally. So while convergence remain a typical goal of the analyst, accuracy must be compared with the medical sensitivity. To do this, some physical conditions, less important in other application fields, as the boundary conditions, must be modelled in order to avoid that any model refinement gives unappreciable precision while tends to disregard what a clinician or a surgeon is able to understand and to use in the context of his professional practice. Setting up correct boundary conditions is an emblematic topic because it concerns a typical approach of computational methods applied to biomedical engineering which must consider two separate scale into analysis or a design approach. When a district of the body is to be analysed, the main goal should be to define correctly the subdomain that the district represents with respect to the whole and then to analyse other subdomains inside, at a level more and more micro, as into a system of Chinese boxes. When a medical device is to be designed a systemic view must be acquired. In this paper, we will start from this underlying feature concerning just FEM applications of a knee design carried out by the research staff of the Laboratory of Biological Structure Mechanics. Then other uses of FEM will be described as analysis fragments through problems studied by the authors and referenced in bibliography.