Comparative study of neuroma formation in the rat sciatic nerve after CO2 laser and scalpel neurectomy

Recent reports have suggested that peripheral neurectomy with the CO2 laser may be effective in preventing subsequent neuroma formation. To study this question further, we performed bilateral sciatic nerve sections in 31 rats using a steel scalpel on one nerve and a CO2 laser on the opposite side. The animals were killed 30 days after neurectomy and specimens were removed for gross observation, light microscopy, and electron microscopy. Axon composition studies were carried out in selected animals and axon diameter histograms were prepared. Well-formed neuromas were present in nerves transected by both the scalpel and the CO2 laser. The scalpel neuromas were characterized by a greater degree of interfascicular collagen deposition and perineurial cell proliferation. Laser neuromas demonstrated less perineurial compartmentalization and scar tissue formation. In addition, a foreign body reaction with multinucleated giant cells surrounding carbonaceous debris was seen that was not present in the scalpel neuromas. Analysis of axon composition studies revealed that both neuromas had a greater density of axons and a higher percentage of small diameter myelinated and unmyelinated axons as compared to control nerves. Laser neuromas had more axons per unit area than scalpel neuromas, but the percentage composition of axons was very similar in the two groups. We could find no evidence in the rat sciatic nerve model that CO2 laser neurectomy is less likely to result in neuroma formation than is conventional scalpel neurectomy.