Coaptation region selection and functional monitoring in direct muscle neurotization: An experimental study with sprague-dawley rats

This study aimed to identify suitable muscle regions for direct muscle neurotization and the effects of muscle neurotization on functional status. This is an experimental in vivo study. Forty 40 Sprague-Dawley rats were divided into 5 groups, and each group included 8 rats. Muscle neurotization was not performed in group 1. In group 2, end-to-end anastomosis was performed between the free endings of the peroneal nerve and the tibial nerve. In groups 3, 4, and 5, the peroneal nerve was implanted inside a 2 mm pouch opened at the proximal, median, and distal ends of the medial gastrocnemius muscle, respectively, and dissected. The results were assessed using the modified Sihler staining method and electromyography. In the rats in group 1, which did not undergo any muscle neurotization procedure, new nerve branches did not form, and peripheral nerves branched out and became thinner. In group 2, the peroneal nerve and tibial nerve endings were anastomosed using the end-to-end technique, and a few new nerve branches formed. The placement of the free ending of the peroneal nerve in the rats in group 3, 4, and 5 in the pouches opened in the proximal, median, and distal parts of the medial gastrocnemius muscle and its end-to-side dissection were associated with the formation of new nerve branches. Among groups 3, 4, and 5, where direct muscle neurotization was performed, the highest rate of new nerve branch formation was in group 3. The muscle neurotization procedure applied to the proximal, median, and distal regions of the gastrocnemius muscle in this study facilitated the formation of new nerve branches, whereas the best outcome was achieved in the proximal region of the muscle and by the end-to-side dissection of the nerve ending when end-to-end nerve ending anastomosis was excluded.