Background: The aim of this study was to compare the incidence of neuroma formation and neuropathic pain following different techniques of nerve ablation in a rat sural nerve model.
Methods: Rat sural nerve was subjected to four different techniques of ablation with standardized creation of a 1-cm gap (n = 15 in each group). These included nerve avulsion, transection and burying in muscle, transection and folding of nerve, and transection alone. Animals were killed after 3 months. Explanted nerves were sectioned and stained with Masson trichrome and S-100 stain against neural tissue. The maximal neural cross-sectional area and neural-to-connective tissue ratio was quantified. Quantitative reverse-transcriptase polymerase chain reaction (n = 5) was used to analyze relative mRNA expression of ciliary neurotrophic factor and calcitonin gene-related peptide.
Results: Neural cross-sectional area was statistically increased (p < 0.05) compared with controls in folded, muscle buried, and transected specimens but decreased in avulsed specimens. The neural-to-connective tissue ratio was statistically decreased in the avulsed group. Relative mRNA expression of ciliary neurotrophic factor was lowest in muscle buried (4 percent of control) (p < 0.05) and avulsed specimens (15 percent of control) (p < 0.05) and higher in folded (52 percent of control) and transected specimens (75 percent of control). Relative mRNA expression of calcitonin gene-related peptide was highest in folded specimens (302 percent of control) (p < 0.05).
Conclusions: Folding and transection lead to increased histologic evidence of neuroma formation, whereas folding leads to neuropathic pain, assayed by calcitonin gene-related peptide expression. Avulsion and muscle burying are preferable techniques for nerve ablation and inhibit nerve regeneration, evidenced by decreased ciliary neurotrophic factor expression. Avulsion offers an alternative to muscle burying when there is no muscle in the vicinity to bury the transected nerve.