EFFECTS OF DIABETES MELLITUS ON VISCOELASTICITY OF ULTRASTRUCTURES OF PERIPHERAL NERVES: THREE-DIMENSIONAL FINITE ELEMENT ANALYSES

Diabetes mellitus induces a variety of neuropathies and causes various symptoms. Understanding how diabetes affects mechanical properties of nerves is useful for preventing complications of diabetes mellitus such as the carpal tunnel syndrome. In a previous study, a two-dimensional hyper-viscoelastic finite element model (FEM) of the ultra-structures of normal rat sciatic nerves was developed using an optical coherence tomography (OCT) microscope and in vitro parallel compression tests. The main goal of this study was to extend the FEM from two to three dimensions and use it to explore hyper-viscoelasticity of ultra-structures of sciatic nerves of diabetic rats. A modification of the compression testing system to enhance OCT cross-sectional images of the nerve samples was also conducted. The results showed that the instantaneous shear moduli of the perineurium, epineurium, and endoneurium of the diabetic rat were all greater than those of the normal rats. Due to high instantaneous shear moduli and low percentage of relaxation, the diabetic nerve is prone to damage when subjected to prolonged mechanical loads.