Contractile properties of canine thyroarytenoid muscle reinnervated from the ansa cervicalis

In an attempt to obtain data on the contractile properties of vocal fold muscle reinnervated from the ansa cervicalis, we severed the recurrent nerve and connected its distal stump to the ansa cervicalis by an end-to-end anastomosis in a series of dogs. Each dog was allowed to heal for 5 months. Then the section of the thyroid cartilage on which the vocal fold muscle inserted was detached, connected to an isometric force transducer, and activated by indirect stimulation successively on both the operated and unoperated sides. A series of twitch contractions was recorded from each side. In two dogs no contractile response was obtained. In the three others, the twitch contraction time was increased significantly, by 23% to 60%. In two of three dogs, the operated muscle was significantly weaker than the unoperated muscle. The reinnervated thyroarytenoid muscle changed its speed in the direction of the donor sternothyroid muscle.