Functional and mechanical evaluation of nerve stretch injury

Peripheral nerves undergo tensile loading in common physiological conditions, but stretch can also induce nerve pathology, impairing electrophysiological conduction. The level of strain nerves can tolerate and the functional deficits which result from exceeding this threshold are not thoroughly understood. To examine these phenomena, a novel system for tensile electrophysiology was created using a grease gap-recording chamber paired with a computerized micromanipulator and load cell. Guinea pig sciatic nerves were stretched beyond their maximum physiologic length to examine the effects of tension on signal conduction. Mechanical and electrophysiological data such as load, position, compound action potential amplitude, and signal latency were recorded in real-time. While 5% strain did not affect conduction, further elongation decreased amplitude approximately linearly with strain. These experiments verify the findings of prior studies into nerve stretch, and demonstrate the utility of this apparatus for investigating the mechanical and electrophysiological properties of nerves undergoing strain.