HR-pQCT-based homogenised finite element models provide quantitative predictions of experimental vertebral body stiffness and strength with the same accuracy as μFE models

Abstract

This study validated two different high-resolution peripheral quantitative computer tomography (HR-pQCT)-based finite element (FE) approaches, enhanced homogenised continuum-level (hFE) and micro-finite element (μFE) models, by comparing them with compression test results of vertebral body sections. Thirty-five vertebral body sections were prepared by removing endplates and posterior elements, scanned with HR-pQCT and tested in compression up to failure. Linear hFE and μFE models were created from segmented and grey-level CT images, and apparent model stiffness values were compared with experimental stiffness as well as strength results. Experimental and numerical apparent elastic properties based on grey-level/segmented CT images (N = 35) correlated well for μFE () and hFE models (). Vertebral section stiffness values from the linear μFE/hFE models estimated experimental ultimate apparent strength very well (). Calibrated hFE models were able to predict quantitatively apparent stiffness with the same accuracy as μFE models. However, hFE models needed no back-calculation of a tissue modulus or any kind of fitting and were computationally much cheaper.

Keywords:

• vertebral body
• finite element modelling
• stiffness
• strength
• fabric

Acknowledgements

Computer resources were available through the Swiss National Supercomputing Centre. We thank Cyril Flaig and Peter Arbenz, ETH Zürich, for the ParFE support.