The super-element, stiffness-matrix approach to interrogate 3D intervertebral disc mechanics

Finite element ( FE ) models of intervertebral discs ( IVD ) are inherently complex, requiring multiple tissue parameters to be defined for tissues which can be difficult to characterise experiment ally. Due to this complexity, understanding how each parameter combines to produce the overall mechanics of the IVD is challenging. To overcome these challenges we used the super-element approach to provide a novel means of interrogating the IVD mechanics. Of p articular interest in the current study, was the coupled, three dimensional (3D) mechanical response of the lumbar spine IVD and to what extent the 3D IVD stiffness is reliant upon the collagen fibre network.