Evaluation of surgical techniques for end-to-side neurorrhaphy in a rat model: A quantitative and qualitative analysis of postoperative neural repair and recovered nerve function.

Introduction: There are two basic techniques to surgically reconstruct peripheral nerves for recovery of function after traumatic nerve injuries. The end-to-end-neurorrhaphy (EtE) and in case of loss of the proximal stump the end-to-side-neurorrhaphy(EtS) where the distal end of the acceptor nerve is connected to the side of a donor nerve. The current study was designed to further contribute to finding the best surgical technique for an EtS neurorrhaphy comparing the functional outcome in a rat model.

Methods: Using a rat sciatic nerve model qualitative and quantitative analyses were performed to evaluate peripheral nerve regeneration after EtS. A total of 22 female Lewis rats (Charles River Wiga, 190g, 8 weeks old) were used for this study. In one test group (E1 / n=6) an EtS was conducted without and in the other(E2 / n=8) with performing a partial neurotomy (PN) through the EPF (epineurial partial flap).

Results: In the test groups (E1 / E2) animals with EtS neurorrhaphy without PN reached the best mean functional score of 1.8 points according to our grading scale. Animals with EtS and PN scored in the mean with 2.2 points. These rats with EtS neurorrhaphy and partial neurotomy had the poorest outcome. The control group C1 with EtE neuroraphies showed the best functional outcome with an average score of 1.

Conclusions: The EtE represents the best surgical option for reconstruction of a nerve's anatomical continuity after transection if both ends are preserved. The EtS on the other hand represent a good alternative with almost equally good functional outcome in cases where the proximal nerve stump was lost. Results also indicate that an EPF should be created for optimal collateral axonal sprouting and best possible results when performing an EtS. However, all other additional injuries of the donor nerve such as a PN should be avoide.