Morphometric and Functional Analysis of Axonal Regeneration after End-to-end and End-to-side Neurorrhaphy in Rats

BACKGROUND: End-to-side neurorrhaphy is controversial in the literature and has sparked debate over its degree of recovery. In this study, nerve regeneration was assessed in rats after end-to-side neurorrhaphy by morphometric analysis, electromyography, electron microscopy, and retrograde horseradish peroxidase (HRP) and Fluoro-Gold (FG; Fluorochrome Inc., Denver, Colo.) transport and then compared to end-to-end neurorrhaphy and sham operation. METHODS: Thirty-seven animals were operated on and divided randomly into 4 groups: group 1, sham; group 2, end-to-end neurorrhaphy; group 3, end-to-side neurorrhaphy with an epineural window; and group 4, end-to-side neurorrhaphy without an epineural window. Three months after surgery, HRP was injected into the peroneal muscles. After 48 hours, nerve segments and lumbar spine segments were collected. Electromyography data were compared between groups, and FG uptake was compared in 20 other animals. Analysis of variance with Tukey-Kramer correction was used for group comparison. RESULTS: The fiber count after end-to-end neurorrhaphy was higher than after end-to-side neurorrhaphy with an epineural window (q = 5.243 and P < 0.01) or without an epineural window (q = 4.951 and P < 0.01). HRP labeling showed a difference between group 2 and end-to-side neurorrhaphy with an epineural window (q = 5.291 and P < 0.01) and without an epineural window (q = 5.617 and P < 0.01). There was also a difference in mean area labeled with FG. Furthermore, the amplitudes of the action potentials were significantly higher in groups 1 and 2. CONCLUSIONS: There was nerve regeneration in all groups studied. However, the end-to-end neurorrhaphy group had better reinnervation than the end-to-side neurorrhaphy groups.