Others suggest that an epineurotomy or perineurotomy, exposing but not injuring donor axons facilitates spontaneous collateral sprouting ( Bertelli, et al. Some have suggested that collateral axonal sprouts repopulate the terminal limb without axotomy, attributing this spontaneous phenomenon to neurotrophic influences ( Caplan, et al. 1992), the ETS literature has become rife with contradictory studies including those investigating the number of axons recruited by this technique, and the functional deficit imposed upon the donor nerve ( Cederna, et al. Unfortunately, since the utility of this technique was revisited ( Viterbo, et al. In theory, it would have strong clinical value for reconstructing avulsed or proximally injured peripheral nerves. We conclude that ETS repair relies upon injury to the donor nerve.Įnd-to-side (ETS) nerve repair, also known as terminolateral neurorrhaphy is a microsurgical technique where the distal, or terminal, limb of a transected nerve is reinnervated by coapting it into the side of an intact, donor nerve ( Fig. These differences were manifest by 150 days, at which point quantitative evidence for pruning was obtained. Progressively more injurious models were associated with improved recipient nerve reinnervation (epineurotomy: 184±57.6 myelinated axons compression: 78.9☑3.8 atraumatic: 0), increased Schwann cell proliferation (epineurotomy: 72.2% increase compression: 39% increase) and cAMP response-element binding protein expression at the expense of a net deficit in donor axon counts distal to the repair. Either compression or epineurotomy with inevitable axotomy were required to facilitate axonal regeneration into the recipient limb. To evaluate the source, and target innervation of these regenerating axons, nerve morphometry and retrograde labeling was further supplemented by confocal microscopy as well as Western blot analysis. We serially imaged living transgenic mice (n=66) expressing spectral variants of GFP in various neuronal subsets after undergoing previously described atraumatic, compressive, or epineurotomy forms of ETS repair (n=22 per group). Significant, unresolved questions include whether the donor nerve needs to be injured to facilitate regeneration, and whether a single donor neuron is capable of projecting additional axons capable of differentially innervating disparate targets. Some work suggests that the recipient limb is repopulated with regenerating collateral axonal sprouts from the donor nerve that go on to form functional synapses. In this technique, the transected end of an injured nerve, representing the “recipient” is sutured to the side of an uninjured “donor” nerve.
End-to-side (ETS) nerve repair remains an area of intense scrutiny for peripheral nerve surgeon-scientists.
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