Aims: the recent ten years have seen a growing interest in termino-lateral (end-to-side) neurorrhaphy; this interest mainly originates from the prospected possibility to recover the function of a damaged nerve without loosing the function of a donor nerve.

We investigated voluntary control recovery after termino-lateral neurorrhaphy in the upper limb of mixed rat nerves (median and ulnar nerves) to assess functional recovery and nerve fibers regeneration.

Methods: We made a termino-lateral neurorrhaphy between median (lesioned) and ulnar nerve (donor) on left upper limb of 24 Wistar female rats. After 6 months, functional recovery of the limb was investigated using grasping test and electrical stimulation; then, rats were sacrificed and we studied morphological changes in muscles and regenerated nerves with light microscopy and stereology.

Results: We observed a functional recovery up to 15 % ± 5% of the normal at grasping test, while electrostimulation was positive in all cases; muscle trophism was good (40 % > than denervated muscles).

On microscope median nerve presented the typical structure of a regenerated nerve; in ulnar nerve some slight signs of degeneration can be detected distally to the site of suture. At the point of suture, nerve fibers of ulnar nerve sprouts into median nerve (collateral sprouting).

Conclusions: Termino-lateral neurorrhaphy induces a collateral sprouting from the donor nerve (as described in the literature); fiber regeneration in the severed nerve leads to a recovery of voluntary functional control.

In the donor ulnar nerve distally to the suture site we found some slight signs of damage, but they do not impair motor function.

In conclusion, termino-lateral neurorrhaphy can be used to repair peripheral nerve lesions with large substance loss where other types of repair strategies cannot be attempted.