DEVELOPMENT OF A COMPUTATIONAL APPROACH TO MODEL AXON MECHANICS IN WHITE MATTER

摘要

Mechanical damage to axons is a proximal cause of deficits following traumatic brain injury and spinal cord injury. Axons are injured predominantly by tensile strain, and identifying the strain experienced by axons is a critical step towards injury prevention. To simulate traumatic events, an accurate representation of the material behavior of the tissues is required. White matter, in particular, demonstrates complex non-linear mechanical behavior at the continuum level, and even more complex, dynamic, composite behavior between axons and the 'glial matrix' at the micro-level. At low levels of tissue stretch, axons demonstrate non-affine behavior, but transition to affine behavior as stretch increases. Herein, we present a representative volume element approach to finite element modeling of white matter that captures essential aspects of the microkinematic coupling between the constitutive elements of the tissue. The degree of coupling significantly affected average stress-strain properties extracted from the model. Predicted changes in axon undulation better matched experimental observations when the degree of axon coupling was decreased.