Abstract
A spinal cord injury (SCI) is recognized as one of the most devastating type of injuries in the world, and the development of a reliable computational prediction scheme of traumatic SCIs involved in traffic accidents and contact sports will be useful to elucidate its injury mechanism. In the present study, we built a micro-indentation tester to precisely characterize mechanical properties of the porcine spinal cord. A spherical indenter with a 0.5-mm diameter was slightly pressed into a transverse cross-section of the smoothly sliced samples at the rate of 30 and 150 μm/s, and its stress relaxation responses were recorded for 180 s. By applying Hertzian contact theory, we found that the instantaneous Young’s modulus of gray matter is significantly greater than that of white matter (P < 0.05) when intended at the higher loading rate (150 μm/s), while Young’s moduli of the gray and white matters are almost the same at the equilibrium state irrespective of a five-fold difference in the employed loading rates. We also found that the white matter is relatively insensitive to the loading rate compared to the gray matter, which may contribute to a mechanical protection of white matter even during the injurious deformation process. Although the specimen size is still limited, these results may enhance the capability of a computational prediction of traumatic SCIs in the future.
