Effect of donor nerve injury distal to an end-to-side neurorrhaphy model.

In end-to-side neurorrhaphy, "noninjury" models of the donor nerve do not seem to offer worthwhile functional outcomes. The role of donor nerve injury distal to the coaptation site remains unclear. End-to-side neurorrhaphy was studied in a rat model in which the proximal stump of the transected musculocutaneous nerve was sutured to the median nerve by end-to-side coaptation. Twenty Sprague-Dawley rats were randomized to four groups of five animals each, in which three different types of donor injury (crush, ligation, or transection injury) distal to the coaptation site were executed; findings were compared with a similar end-to-side model without donor nerve injury (control). Behavioral analysis, electrophysiological studies, muscle morphometric studies, and nerve fibers counts showed no significant differences among groups. However, there was a significant difference regarding mean myelin area (P = 0.0362) and mean fiber diameter (P = 0.0159) for the crush injury group as compared with the control group. No significant differences were found among the other groups. These data suggest that donor crush injury distal to the coaptation site may increase the rate of myelin formation in regenerating axons across an end-to-side model; however, at 4 weeks of follow-up, there was no significant behavioral or functional significance in this treatment group.