Degenerative and regenerative processes in the peripheral nerve after disconnection and reanastomosis using the Neodym Yag laser

Neuroma formation in a rat median nerve model: influence of distal stump and muscular coating

BACKGROUND

The purpose of this study was to investigate neuroma formation in a rat median nerve model.

METHODS

In three groups, the median nerve was exposed and a gap was created. In the first group, a short gap of 1 cm (n = 12) was created; in the second, a long gap of 2 cm (n = 12) was created in the nerve. Another group was used to analyze the development of neuroma formation when the proximal stump was buried in adjacent muscle with an additional gap of 2 cm (n = 12). The use of different lengths should allow one to gain information about dilution effects of distal stump factors that may contribute to neuroma formation. Nine months later, specimens were gathered and histologically analyzed. The cross-sectional areas of neuromas were measured and the neural/connective tissue ratios were estimated.

RESULTS

The cross-sectional areas demonstrated that neuroma formation was significantly higher in the short-gap group than in the long-gap group, and smallest in the muscle-covered group. The percentage of neural tissue was highest in the muscle-covered and long-gap groups and lowest in the short-gap group.

CONCLUSIONS

These results demonstrate an association between neuroma formation and distal stump distance. This observation may be explained by the factors originating from the distal stump that were blocked when the proximal nerve stump was completely buried in the muscle. For clinical application, the authors recommend not only burying the proximal stump in a muscle but also surgically augmenting the gap between the proximal and distal stumps.

Is laser repair effective for secondary repair of a focal lesion in continuity?

It is possible to seal nerve ends together with the laser, and this can be effective for sharp injuries that are repaired relatively acutely or primarily. The possibility of utilizing the laser for secondary nerve repair after resection of a lesion in continuity was investigated in a rat sciatic nerve model. After baseline recording of nerve and muscle action potentials (MAP), a 3-mm-long crush injury of the sciatic nerve was performed bilaterally in 12 rats. Two weeks later, the crushed segment was resected, and the nerve on one side was repaired by end-to-end anastomosis using epineurial sutures and on the other side by sealing the nerve ends together with the CO2 laser. At reexploration 50 days postoperatively, all 12 suture repairs were anatomically in continuity and conducted a nerve action potential (NAP), while 10 of the 12 laser-repaired nerves had distracted. Laser repairs not distracted showed electrical and histologic evidence of regeneration. It is concluded that laser repair is not effective for delayed repair of lesions in continuity unless tension at the repair site can be lessened.