The selectivity of regenerating motor and sensory axons.

Functional results of peripheral nerve repair have been hampered by misdirection of regenerating axons. The purpose of this study was to determine in a rat femoral nerve model whether regenerating motor and sensory axons from a proximal nerve stump select the appropriate distal motor or sensory branch. In two experiments, the proximal stump of the motor or sensory branches was sutured to the distal motor sensory stumps, so that the three branches were parallel and the three transected ends faced in the same direction. More regenerated axons from both the proximal motor and sensory stumps entered the distal sensory stump. The number of misdirected axons did not decrease over time. The selective regeneration of motor axons toward the distal motor stump could not be validated. In this study, neurotropism appeared to play a measurable role in sensory axon regeneration, but not in motor axon regeneration. Pruning of the misdirected axons was not demonstrated.