Nerve repair using a composite graft of vein and denatured skeletal muscle: morphologic analysis.

Five groups of six rats each underwent sciatic resection, bridged with a 20-mm-long graft. Five different types of graft were used: (1). vein; (2). fresh muscle; (3). denatured muscle; (4). vein and fresh muscle; and (5). vein and denatured muscle. Denaturation was obtained by dry thermal shock in a microwave oven. Morphologic analysis took place at 6 months. The macroscopic appearance of the graft was continuous in all type 4 and 5 animals. Morphometric analysis within the graft revealed a significantly greater number of fibers in type 3 animals. Average fiber diameter and g ratio were higher, although not significantly, in type 5 animals. Distal to the graft, average fiber diameter and g ratio were significantly higher in type 5 rats. Denaturation by exposure to thermal shock significantly improves axonal regeneration, both quantitatively and qualitatively. The regeneration rate seems to be more rapid within denatured muscle. Denaturing muscle by exposure to thermal shock provides an excellent guide for axonal regrowth, but axonal leaks may occur. This problem is solved by a muscle-in-vein graft technique.