Effect of a modified Nd : YAG laser technique on neuroma formation: An experimental study in rat sciatic nerve

Background and Objectives: Traumatic transection of a peripheral nerve is i nherently associated with the development of neuroma at the end of the prox imal stump, often leading to therapy-resistant pain. This study was designe d to evaluate whether the neodymium:yttrium aluminum garnet (Nd:YAG;) laser could prevent neuroma formation after neurectomy. Study Design/Materials and Methods: The sciatic nerves of 14 rats were diff use coagulated by defocused Nd:YAG laser (12 W power), and subsequently tra nsected with additional focused laser energy. The control group consisted o f contralateral nerves transected by microscissors. The nerves were reexpos ed at different time intervals up to 9 weeks after surgery, and evaluation consisted of macroscopy, and light and transmission electron microscopy. Results: True neuroma formation could not be observed after laser transecti on, and only five nerves formed a neuromatous bulb, with minimal adhesions to surrounding tissue. Microscissor transection resulted in widespread ampu tation neuromas, consisting of regenerating axons and connective tissue, an d nervous tissue regenerating into surrounding tissue. Laser-transected ner ves showed degenerative changes of the axons and myelin, while proliferatio n of Schwann cells could not be observed. No outgrowth of axons could be ob served outside the coagulated proximal stump. An epi/perineurial layer was present, covering the nerve stumps. Microscissor-transected nerves showed p roliferation of fibroblasts and Schwann cells, forming minifascicles, and v igorous outgrowth of axons into the tissue and even into the distal nerve s tump. Conclusions: Within the limitations of this study it is concluded that the formation of amputation neuromas is suppressed by Nd:YAG laser application by thermal coagulation of the nerve and suppression of Schwann-cell prolife ration. (C) 1999 Wiley-Liss, Inc.