Motor collateral sprouting through an end-to-side nerve repair.

The outcome of end-to-side repair of peripheral nerves was investigated. The sciatic nerve in 10 male Sprague-Dawley rats was dissected to its tibioperoneal junction. The nerve to the medial gastrocnemius muscle, branching from the tibial nerve, was ligated at its origin and divided. Its distal end was sutured to an epineurial window on the side of the intact tibial nerve 1 cm distally. At 12 weeks, physiologic evaluation of the medial gastrocnemius muscle and analyses of histologic preparations of nerve and muscle were performed. The results showed that reinnervation successfully occurred in 8 rat media gastrocnemii. The mean weight of the reinnervated medial gastrocnemius was 73% of the contralateral normal muscle, the mean muscle fiber cross-sectional area of the reinnervated muscle was 72%, and the force of contraction was 60%. Analyses of histologic preparations revealed evidence of myelinated axons in the medial gastrocnemius nerve and no evidence of damage to axons of the donor tibial nerve.