Short communicationConcept and development of an orthotropic FE model of the proximal femur
Introduction
In literature, many isotropic simulation models of the proximal femur have been described to calculate the functional adaptation of cortical and cancellous structures, (Couteau et al., 1998; Jacobs et al., 1997; Lengsfeld et al., 1996; Weinans et al., 1992). Since bony materials are not isotropic but rather anisotropic and orthotropic, respectively (Carter et al., 1989; Savvidis and Stabrey, 1996; Wirtz et al., 2000; Yang et al., 1999), it was the object of our study to develop an orthotropic finite-element (FE) “femur reference model” to simulate bone remodelling more reasonably adapted to the physiological situations in vivo.
Section snippets
Materials and methods
For orthotropic modelling of bony structures, four main developing steps had to be performed: (step 1) the three-dimensional reconstruction of femoral geometry and the generation of an FE mesh for the bone model, (step 2) the allocation of the material properties of the bone according to their density for each FE, (step 3) the exact definition of the principal stiffness directions for each FE, (step 4) the implementation of a numerical algorithm for time- and load-dependent remodelling of bone.
Discussion
Although since several years, some studies have been performed to generate anisotropic FE modelling of the proximal femur (Bagge, 2000; Doblaré and Garcia (2001), Garcia et al. (2001); Jacobs et al., 1997), no real solution exists to the problem of finding the orthotropic material orientation to an optimal structure within a three-dimensional bone remodelling tool.
The presented new simulation tool is a more comprehensive approach to this “three-dimensional problem” of orthotropy. Each FE has
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