Is end-to-side neurorrhaphy effective? A study of axonal sprouting stimulated from intact nerves

The purpose of this study was to determine if axonal sprouting across an end-to-side coaptation could be stimulated and if so, to identify the source of the regenerating axons. Mechanical trauma, the method used to stimulate axonal sprouting, was compared to a control group with coaptation only and an additional non-grafted control group. After a 20-week recovery period, electrical stimulation revealed that the target muscles had been reinnervated in all groups except the non-grafted control group. Axonal counting demonstrated a significant increase for the mechanical trauma group compared to the control group with coaptation only [ratio of the density of axons/microm2 of the experimental to the contralateral control side: 2.78+/-0.11 vs. 0.96+/-0.15, respectively, p<0.002). Tibialis anterior muscle weights were significantly increased for both groups vs. the non-grafted control group (ratio of experimental to the contralateral control side: coaptation-only control, 0.539+/-0.024; mechanical trauma, 0.538+/-0.036 vs. nongrafted control, 0.220+/-0.003, p<0.002). Of importance, this study provides evidence that the intact tibial nerve functions as a bridge for regenerating axons derived from the proximal peroneal stump. This suggests an alternative explanation to successful end-to-side axonal sprouting, and questions the clinical utility of end-to-side coaptation.