Bridging defects in nerve continuity: influence of variations in syntheticfiber composition

Synthetic filaments introduced into a silicone tube may help to enhance axo nal growth over extended defects in nerve continuity [1]. Here we test the influence of number (0, 3, 7 or 15), size (diameter 150 or 250 mu m) and ma terial of filaments (polyamide or catgut) enclosed in such tubes (inner dia meter 1.98 mm) on axonal growth across a 10 mm defect in rat sciatic nerve. The morphology of the tube content was analyzed four weeks post-surgery. T he area of the formed tissue matrix inside the tube showed no difference be tween the groups. Myelinated axons were observed in the formed tissue matri x inbetween and peripheral to the filaments, however, separated from the fi laments by concentric cell layers. The number of myelinated axons was less in the tubes with 15 filaments, most pronounced when catgut filaments were used. In most cases, except in tubes with 15 catgut filaments, fibers had g rown into the distal nerve segment (pinch reflex test/light microscopy). We conclude that an intrinsic framework consisting of a limited number of syn thetic filaments inside an extrinsic framework (silicone tube) does not dis turb nerve regeneration. The formed tissue matrix was neither influenced by the presence or the numbers (if less than or equal to seven filaments), ty pe of filaments nor the size of the filaments indicating the importance of the inserted nerve segments. (C) 1999 Kluwer Academic Publishers.