Tubulization increases axonal outgrowth of rat sciatic nerve after crush injury

It is important to develop methods which increase nerve regeneration since restoration of function following injury to peripheral nerves often requires outgrowth of the injured axons over long distances. In this study, axonal outgrowth after bilateral crush injury to the sciatic nerve of the rat was measured. One group with large-diameter nonpermeable silicone tubes and one group with large diameter permeable silicone tubes applied around the crush site on one side had regeneration following nerve injury compared to controls on the other side. The length of regeneration of the regenerating axons were then measured 4, 5, and 6 days following the crush injury using the "pinch reflex test." The presence of axons at the pinch level was confirmed by immunocytochemical staining for neuro-filaments. The length of regeneration for rats with nonpermeable tubes was significantly greater than that of the contralateral control side and was so at all times (p < 0.05). The effect was present but not that pronounced where permeable tubes were used. We conclude that the outgrowth of regenerating sensory axons after sciatic nerve crush injury in the rat can be increased by enclosing the regeneration site in a silicone tube. The observed effect may be due to local mechanisms such as macrophage invasion or prevention of rapid wash-out of fluid from the crush zone.