Motor functional and morphological findings following end-to-side neurorrhaphy in the rat model

Nerve repair cannot always be achieved by the conventional end-to-end technique. This study evaluated the functional recovery of nerves repaired with end-to-side neurorrhaphy in a rat model. The right peroneal nerves of 80 female rats were transected and divided into four groups. In group A, the nerve ends were separated and remained unrepaired; in group B, the distal peroneal ends were directly sutured to the epineurium of the tibial nerves in end-to-side fashion; in group C, the distal ends were sutured through an epineurial window at the repair site in end-to-side fashion; and in group D, the nerve ends were reconnected by the traditional end-to-end technique. Evaluation included gait analysis by calculation of a peroneal functional index, measurement of contractile function of the extensor digitorum longus muscle, wet weight of the extensor digitorum longus, and histological examination. The findings of this study suggested the following: (a) end-to-side neurorrhaphy allows effective motor functional recovery, demonstrated by earlier improvement of the peroneal functional index, stronger muscle contractile function, greater muscle weight, and higher density of regenerated axons compared with unrepaired nerves; (b) removal of the epineurium of the donor nerve at the nerve coaptation site increases the effectiveness of end-to-side neurorrhaphy, but the epineurium appears to be a partial barrier to axonal regeneration; (c) removal of the epineurium does not affect the structure and function of the donor nerve; and (d) end-to-end repair achieved the best functional recovery among the four groups; therefore, end-to-side repair should be considered as a potential alternative only when no proximal nerve is available.