Abstract
Background
Understanding vertebral fracture is important in order to reduce fracture risk. Previous studies have used FE to investigate mechanical behaviour, typically using a linear material response. This study aimed to establish a novel model that could represent the plastic behaviour leading to fracture.
Method
Porcine vertebrae were mCT scanned and they were loaded to failure in a material test machine (Instron 5965). The specimens were then rescanned. From the first scan, specimen specific FE models were created (ScanIP, Simpleware, UK). Mesh convergence was studied and tetrahedral elements with an approximate element size of 0.7 were used for computational simulations. The relationship between greyscale values (GS) and Young's modulus (E) was optimised to match the experimental load displacement data using Ansys. Further, a plastic material response was modelled.
Results
The experimental data showed an initial toe region followed by a linear response, which then displayed plastic deformation prior to failure. The following relationship was stablished for greyscale values of images and E: E=0.98GS+50.836 MPa. The following yield parameters, yield stress=2.2E/227.63 MPa and tangent=6.64E allowed FE prediction of the non-linear part of the experimental data.
Conclusion
A mathematical relationship between E and greyscale values combined with plastic response allowed for the first time an FE model to fully represents the actual response of vertebral prior to failure.
Level of Evidence
3b: Individual case-control study.
