Repair of peripheral nerves of unequal diameters.

Four techniques for anastomosis were investigated for the anastomosis of a large proximal segment to a smaller distal segment of rat peripheral nerve with a size disparity of approximately 3 to 1. The techniques were perineural sutures (group I), KTP laser annealing (group II), collagen tubes with a 5-mm gap between the nerve segments (group III), and collagen tubes without a gap between the nerve ends (group IV). At 6 weeks there were no gross nerve distractions in groups I or IV. There were two failures in group II and three in group III. The percentage of fibers that crossed intact anastomoses were: group I, 89%; group II, 75%; group III, 115%; group IV, 125% (P less than .05 for the collagen tube repairs). Our results indicate that the suture technique is still the most reliable method of nerve repair. However, collagen tubes were effective in increasing the percentage of axons crossing the anastomosis.