An Experimental and Numerical Investigation of the Mechanical Properties of Spinal Cords

Studies concerning the mechanical properties of the spinal cord are crucial for the understanding of various related pathologies. The present study introduces the results of an analysis focused around the mechanical properties of the two types of the mammalian spinal cord: domestic pig (Sus scrofa f. domestica) and domestic rabbit (Oryctolagus cuniculus f. domesticus). The research has been conducted in an in vitro environment, and the freshly dissected cords have been subjected to uniaxial tension testing. A series of preliminary tests allowed for the selection of the optimum method for fixing the cord in the chuck of the testing machine. All preparations were tested for 3 hours after the death of the animal, while an appropriate level of hydration, and the temperature and the strain rate of 0.08s-1 have been maintained. The nonlinear response of the tested tissues has been obtained under the force-displacement conditions. On the basis of the experimental studies the mechanical properties of the samples have been described. Additionally, numerical calculations have been performed on a simplified model of the spinal cord with the use of the finite element (FE) method, which were finally compared with the actual behavior of the sample tissues. An analytical approach with the hyperelastic Ogden material model and FE model of the spinal cord were employed to derive mechanical properties of the tested spinal cords. The results demonstrate that a non-linear FE model is able to predict the mechanical behavior of the spinal cords in the uniaxial tension.