Analysis of Epineurial Lidocaine Injection for Nerve Transfers in a Rat Sciatic Nerve Model

Nerve transfers for peripheral nerve injuries can result in variable outcomes. We investigated the neuroprotective effect of epineurial lidocaine injection in the donor nerve prior to transection, with the hypothesis that proximal axon loss would be decreased with consequent increased neuroregeneration and functional recovery. A rat sciatic nerve model was used with 4 intervention groups: (1) lidocaine; (2) lidocaine/calcium gluconate (CG); (3) CG; or (4) saline (control). Behavioral testing and qualitative and quantitative histological evaluation was performed at 8 and 12 weeks. Histological assays included transmission electron microscopy, retrograde fluorogold labeling, and whole mount immunostaining. Functional assessments through the sciatic functional index and Basso, Beattie, and Bresnahan scale showed a statistically significant increase in recovery at 8 and 12 weeks with lidocaine treatment. Significantly higher axonal counts were obtained in the lidocaine-treated groups. Fragmentation and increased myelin damage was present in the CG and saline groups. Retrograde fluorogold labeling showed a statistically significant increase in the number of L4-6 dorsal root ganglion neurons in the lidocaine-treated groups. Whole mount immunostaining identified extension of the axonal growth cone past the nerve coaptation site in lidocaine-treated groups, but not in CG and saline groups. Our results suggest that epineurial lidocaine injection prior to donor nerve transection for nerve transfer has a neuroprotective effect, resulting in increased proximal axon counts and improved functional recovery. These findings may have direct clinical application because epineurial lidocaine can be used in surgery as a simple and inexpensive intervention for promoting improved clinical outcomes after nerve transfer.