Nerve lengthening and subsequent end-to-end repair yield more favourable outcomes compared with autograft repair of rat sciatic nerve defects

Outcomes of end-to-end nerve repairs are more successful compared with outcomes of repairs bridged by nerve grafts. However, end-to-end repairs are not always possible for large nerve gaps, as excessive tension may cause catastrophic failure. In this study, we built on previous nerve-lengthening studies to test the hypotheses that gradual lengthening of the proximal stump across a large nerve gap enables an end-to-end repair and such a repair results in more favourable regenerative outcomes than autografts, which represent the gold standard in bridging nerve gaps. To test these, we compared structural and functional outcomes in Lewis rats after repair of sciatic nerve gaps using either autografts or a novel compact internal fixator device, which was used to lengthen proximal nerve stumps towards the distal stump over 2 weeks, prior to end-to-end repair. Twelve weeks after the initial injury, outcomes following nerve lengthening/end-to-end repair were either comparable or superior in every measure compared with repair by autografting. The sciatic functional index was not significantly different between groups at 12 weeks. However, we observed a reduced rate of contracture and corresponding significant increase in paw length in the lengthening group. This functional improvement was consistent with structural regeneration; axonal growth distal to the injury was denser and more evenly distributed compared with the autograft group, suggesting substantial regeneration into both tibial and peroneal branches of the sciatic nerve. Our findings show that end-to-end repairs following nerve lengthening are possible for large gaps and that this strategy may be superior to graft-based repairs.