A comparative morphological study of direct nerve implantation and neuromuscular pedicle methods in cross reinnervation of the rat skeletal muscle
Bielecki M, Skowronski R, Skowronski J

Purpose: The study was undertaken to evaluate the recovery of rat skeletal muscles reinnervated by crossed direct nerve implantation and crossed neuromuscular pedicle graft.
Material and methods: The animals (157) were divided into 3 groups. In the first group – direct nerve implantation – (DNI) 52 animals, the peroneal nerve was transected and implanted into the gastrocnemius muscle of the hind limb of the rats. In the second group (53 animals) – the neuromuscular pedicle (NMP) of the peroneal nerve was elevated and transferred to the gastrocnemius muscle. The third group consisted of 52 healthy animals. Muscle function was examined by electrophysiological methods (evoked electromyography and muscle isometric tetanic tension) and by morphological methods (reinnervated muscle weight, microscopic examinations, morphometric and histochemical examinations).
Results: The weight of reinnervated muscles in the first 3 weeks decreased. The lowest values of muscle weights were noted at 4 weeks. At the end of the experiment muscle weight in the first group was 64.3% of the control group and in the second group 65.2%. Morphometric, histological and histochemical analysis were performed after 12 and 36 weeks. At 12 weeks of the experiment the diameter of reinnervated muscle fibers in the second group was statistically higher than in the first group. At that time the process of reinnervation was more advanced than in the first group. At 36 weeks there were no statistical differences between the two groups. An increase in the number of muscle fibers was noted as the processes of reinnervations progressed. 
At the site of nerve (or pedicled nerve-muscle) implantation new motor end plates were formed.
Conclusions: We consider that reinnervation of the experimentally paralyzed muscle is possible after crossed DNI and after NMP neurotization. The reinnervation with the NMP technique is quicker than with the DNI. Based on the morphological examinations – both methods guarantee only a partial recovery of the function of the paralyzed muscle.

Key words:   denervation, direct neurotization, neuromuscular pedicle, muscle reinnervation, motor end plates.