Instrumented spinal cord surrogate using optical fiber: Role of the fiber's location

In vitro replication of traumatic spinal cord injury is necessary to understand its biomechanics and to improve prevention devices and care. During the trauma, the spinal cord withstands an impaction at high velocity. In order to fully assess spinal cord compression, a physical spinal cord surrogate instrumented with bare optical fibers is a promising avenue. The sensing is based on light transmission loss observed in optical fibers subjected to bending. In this paper, the role of the fibers' position within the surrogate is presented and discussed. The closer the fiber from the surface of the spinal cord, the more sensitive it is to small compression magnitude. A threshold value of 15 % was observed for the fiber located at the upper surface of the surrogate. However, this fiber was not able to record compression over 40 %. Another fiber located in the middle of the surrogate was needed to record compression between 40 % to 85 %. Using two fibers allows continuous recording of compressions ranging from 15 % to 85 %. This study shows the relevance of using multiple fibers in order to fully assess the compression of the spinal cord surrogate.