Analysis of mechanical properties of cancellous bone under conditions of simulated bone atrophy

The mechanical properties of cancellous bone have been shown to depend on bone density and on the anisotropy of the trabecular bone structure. By means of high-resolution quantitative computed tomography (QCT), providing a nominal resolution of 0.17 mm, it became possible to assess both apparent density and trabecular microstructure of intact bones. In order to study the influence of age- and disease-related bone loss on the mechanical properties of cancellous bone, a more phenomenological approach was used to develop a novel bone resorption algorithm, called simulated bone atrophy. The algorithm, which is principlally based on constrained Gauss filtration of segmented data volumes, was applied to create derived microstructural models. The mechanical behavior of the cancellous bone can be expressed as a function of the anisotropic bone properties of the microstructural model on the continuum level. To study the influence of bone atrophy on bone strength we compared three models: the originally noninvasively measured bone biopsy and two derived models simulating moderate and pronounced atrophy. For the comparison of the three models, the apparent Youngʹs moduli in the three orthogonal directions were predicted for each model with the help of three-dimensional finite-element analysis. Realistic results for the apparent Youngʹs moduli were found for the tissue moduli chosen. The results siggest that the prediction of anisotropic material properties of cancellous bone based on noninvasive measurements of trabecular microstructures and the application of simulated bone atrophy may be helpful to understand the influence of age- and disease-related bone loss on bone strength.