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If the proximal nerve stump is not available after a peripheral nerve injury, end-to-side anastomosis of its distal stump remains the only treatment modality promising potential recovery of the injured nerve’s function. Sensory return after end-to-side anastomosis has been investigated in only one study in which the donor nerve was interrupted distally to the anastomosis. There have been no reports on the use of an uninjured donor nerve to date. The present study was undertaken to test the hypothesis that recovery of sensory function of a transected nerve can be induced by using end-to-side anastomosis to an uninjured nerve. The distal stump of the transected peroneal nerve was approximated end to side to the intact sural nerve using epineural sutures. Sprouting of sensory axons into the anastomosed peroneal nerve was assessed by the nerve pinch test, and the number of myelinated axons was determined on a tissue cross-section stained with Azur II. The myelinated axons were counted and their cross-section areas were determined for the sural nerves of both the operated and control animals. Pain sensitivity of the foot instep skin was assessed by the skin pinch test. Over the period of 18 weeks after end-to-side anastomosis of the transected peroneal nerve to the intact sural nerve, the axons sprouted into the peroneal nerve in all the 11 animals operated. The pinch test in the anastomosed distal stump of the peroneal was positive in all animals as far as it was possible to test. There were 277 ±119 myelinated
axons in the anastomosed peroneal nerve, their cross section area being mostly smaller than 10 μm² 18 weeks after anastomosis, partial sensitivity of the instep skin (19–40 % of the surface area of the peronneal nerve innervation territory) was documented in three of the 11 animals. The remainder showed no pain sensitivity in this region. Return of sensory function of the transected peripheral nerve sutured end to side to an uninjured peripheral nerve can occur in principle, but may be delayed or prevented by some yet unknown factors.