A computational method for determining tissue material properties in ovine fracture calluses using electronic speckle pattern interferometry and finite element analysis

For numerical simulations of biological processes the assignment of reliable material properties is essential. Since literature data show huge variations for each parameter, this study presents a method for determining tissue properties straight from the investigated specimens by combining electronic speckle pattern interferometry (ESPI) with finite element (FE) analysis in a two-step parameter analysis procedure. ESPI displacement data from two mid-sagittal ovine fracture callus slices under 5 N compressive load were directly compared to data from FE simulations of the respective experimental setup. In the first step a parameter sensitivity analysis quantified the influence of single tissues on the mechanical behavior of the callus specimens. In the second step, material properties (i.e. Young's moduli and Poisson's ratios) for the most dominant material of each callus specimen were determined through a parameter sampling procedure minimizing the mean local deviations between the simulated (FE) and measured (ESPI) equivalent element strains. The resulting material properties showed reasonable ranges downsizing the variability of previous published values, especially for Young's modulus which was 1881 MPa for woven bone and 16 MPa for cartilage in average. In conclusion, a numerical method was developed to determine material properties straight from independent fracture callus specimens based on experimentally derived local mechanical conditions.