Non-uniform assignment method for skeletal materials based on slope difference distribution and experimental validation.

A modeling method of non-uniform material assignment based on Slope Difference Distribution (SDD) is proposed to establish a complete and effective finite element (FE) model of the lower limb tibia. The validity and accuracy of the model based on in vitro mechanical experiments are verified. An initial tibia model was established based on Computed Tomography (CT) images. The numerical distribution of the extracted Hounsfield Unit histograms of the tibia mesh elements was fitted as a smooth curve. The critical point of the slope difference distribution curve was computed and selected to establish a tibia FE model with non-uniform material properties through numerical variations. The composite tibia's area of interest was subjected to data acquisition and analysis of displacement and strain at three gaits through a Digital Image Correlation (DIC) device. The slopes of the stress-strain straight fitting lines for slope difference distribution and structural FE models are 47.17 and 36.45. A comparison of the results of the previous experiments revealed that the FE model based on the material assignment method of slope difference distribution is more accurate. The assignment method is not limited to tibia models but also provides a method for modeling other human bones and reduces the cost of mechanical testing for accurate prediction in the simulation of bone biomechanics.