Prediction of local cellular deformation in bone--influence of microstructure dimensions.

A multilevel finite element approach is applied to predict local cell deformations in bone tissue. The loads applied to a whole femur during the stance phase of the gait cycle were related to the strain at the level of a single lacuna and of canaliculi. Cell deformations were predicted from detailed linear FE analysis of the microstructure, consisting of an arrangement of cells embedded in bone matrix material. The local macroscopic stress assigned to each point was used to calculate the mesoscopic and consequently the microscopic nodal forces. The actual tissue principal strain along the femur deviated considerably from an average tissue value. The predicted bone matrix strains around osteocyte lacunae and canaliculi, were nonuniform and differed significantly from the macroscopically measured strains. Peak stresses and strains in the walls of the lacuna were up to six times those in the bulk extracellular matrix. Significant strain concentrations were observed at sites where the process meets the cell body. The dimensions of the lacunar axes influenced slightly the local strain.