A new type of "bioartificial" nerve graft for bridging extended defects in nerves.

In the rat sciatic nerve, a gap of around 10 mm in nerve continuity seems to be the maximal distance which can be successfully repaired by silicone tubes. In this study we tested if a new artificial nerve graft, composed of eight polyamide filaments (diameter 250 microns) placed inside silicone tubes (1.8 mm inner diameter), could be used to bridge an extended gap (15 mm) in rat sciatic nerve. Silicone tubes containing eight polyamide sutures were found to support regeneration across such a gap. After 4 weeks sensory fibres had bridged the gap and grown into the distal nerve segment as revealed by a positive pinch reflex test as well as positive staining for neurofilaments in the distal nerve segment. Myelinated axons could be observed in the tissue matrix formed in between and peripheral to the synthetic filaments along the whole length of the tube. In contrast, when silicone tubes without filaments were used to bridge the 15 mm gap, the tubes contained only fluid or in two cases a thin tissue strand. No positive pinch reflex response was elicited in the nerve segment distal to such a tube. We conclude that the new artificial nerve graft can be used to support regeneration across extended gaps in nerves.