Nerve bypass grafting for the treatment of neuroma-in-continuity: an experimental study on the rat

The treatment of neuroma-in-continuity is controversial. To bypass neuroma-in-continuity with a nerve graft using end-to-side neurorrhaphy is considered to be theoretically a good option. To test this therapeutic modality, we performed a nerve bypass graft in a neuroma-in-continuity rat model. An obstructive neuroma-in-continuity was created in a transected peroneal nerve by interposition using the aponeurosis of the spinal muscles. In the experimental animals, (1) immediate, (2) 3-week delayed, or (3) no ulnar nerve bypass graft was performed. The peroneal functional index (PFI), conduction velocity, tibialis anterior muscle weight, and histomorphometric analyses were performed and compared with control (simply cut and repair) animals. On postoperative day 70, the recoveries of the PFI values, conduction velocity, and tibialis anterior muscle weight in the bypassed animals showed no significant differences as compared with the control animals, and the extent of these recoveries in the bypassed animals were significantly superior to those in the no-graft animals. In the histomorphometric analysis, the mean percent nerve in the bypassed animals was significantly larger than that in the no-graft animals. In conclusion, this technique may be a good alternative to the current therapeutic techniques for neuroma-in-continuity when there is a significant retained function.