Disc Torsion Mechanics: Comparison of Animal Models to Human

The intervertebral disc plays a critical role in providing structural support to the spine while permitting extensive flexibility in a number of orientations. Axial rotation is a key parameter in spine function and torsional instability is related to spinal degeneration [1]. Animal models are integral components in many in vivo disc studies, however each animal varies in availability, size, cost, and scientific criteria such as cell phenotype and biomechanics. Selection of an appropriate animal model requires knowledge of the similarities and differences in biomechanical and biochemical factors between the model and human discs. Previous studies have often compared the characteristics of a single animal model with the human disc [2, 3]. However, variations in animal models and testing protocols between groups hinder comparisons and interpretations between different studies. This is especially relevant in torsion mechanics, where the magnitude of an applied compressive load and other testing parameters significantly affect the apparent torsional stiffness of the disc [4]. The objective of this study was to measure and compare the torsion mechanical properties of the human disc and 11 disc types from 8 mammalian species.