Spontaneous gait recovery after sciatic nerve transection impairs the non-invasive evaluation of artificial nerve-guides in rats

The study of the in-vivo regeneration of a nerve, made by purely histological methods, requires a high number of animals: this poses serious problems of technique, ethics and funding. A cheaper analysis, performed on the same animal along the duration of a study, is seeked with favour and Authors wanted to evaluate gait recovery after sciatic nerve transection as a non-invasive method to evaluate the performance of an artificial nerve-guide in rats. Male Wistar rats (n=16) were divided into three groups: in group A (n=5) the experimental gap produced was bridged by a custom-made guide; in group B (n=7) animals were “sham-operated”; in group C (n=4) a PMMA cap sealed the proximal nerve stump. In group A a regenerated nerve was retrieved after 8 weeks, in all animals. In group B it was possible to retrieve mostly bulbous neuromatous stumps. In group C all the animals presented a voluminous neuroma. Signs of auto-mutilation had the following distribution: 1/5 in group A; 4/7 in group B; 3/4 in group C. A clear difference in gait recovery exists only between group C (no recovery) and the two other groups (early recovery in both). The present study highlights that in the male Wistar rat sciatic model a spontaneous recovery in gait pattern occurs very early (within the first or second week); with this animal model, a recovery in gait is likely to ensue irrespective of the kind of device eventually tested since it may happen even without a device.