Investigating mesh parameters to achieve clinically applicable finite element analysis of vertebrae

Numerical modeling of bones and especially mechanical analysis using the finite element method is a popular procedure for the investigation of the mechanical behavior of intact bones. Spine is an anatomical site, which is susceptible to degenerative pathologies and trauma. Consequently the need for mechanical analysis of its components is imperative. There are two ways to perform mechanical analysis; the first one is destructive, includes experimentation and can not be held in vivo while the second is non destructive and its main tool is the finite element method. The question of essential accuracy in order to attain reliable results arises when using the finite element method. Important parameters influencing the accuracy of finite element models are the mesh density and the element type. The objective of the present study is to review the results of the mechanical analysis of a 3D vertebra model, using different mesh densities and element types, in order to acquire a satisfactory compromise between computational time that ensures the clinical applicability of the method and accuracy. For this reason five patient specific models of the same first lumbar vertebra belonging to a young male have been created. The first one is built with voxel elements and the four others with tetrahedral or a combination of hexahedral and tetrahedral elements. Different quantities and mechanical magnitudes have been studied and compared. The finer mesh resulted in a model that was difficult to handle and did not offer essentially different results. On the other hand the coarser one needed a lot less computational time, and its results of the mechanical analysis can be considered reliable.