A rat model of functional free muscle transfer for facial reanimation and establishment of a thoracodorsal artery-based muscle flap

Introduction: Facial paralysis is a debilitating condition that can have a significant impact on a person's quality of life. Functional free muscle transfer (FFMT) is a surgical technique that has been used to improve facial paralysis, but there are limited studies on the anatomical approach and use of an animal model. The purpose of this study was to establish a rat model of FFMT in facial paralysis. Methods In this study, a total of twelve Wister rats weighing over 250 g were used to establish a rat model for FFMT using the ipsilateral motor nerve. All procedures were conducted under general anesthesia, and a preauricular incision with a mandibular extension was made to expose the buccal and marginal branches of the facial nerve. An axillary incision was also made to identify and dissect the thoracodorsal vessel and nerve. A partial latissimus dorsi muscle was then transferred to the facial region and the facial vessels and mandibular branch of the facial nerve were anastomosed to the thoracodorsal vessels and thoracodorsal nerve, respectively. Results Our study successfully established a functional muscle flap based on the thoracodorsal vessel in a rat model. A total of 10 rats underwent the surgical procedure, and nine survived the postoperative period. Four months after surgery, the transferred muscle flaps were assessed, and six out of nine were viable. Among the viable flaps, five showed successful innervation. Conclusion This study has successfully established a rat model of FFMT surgery, which is a commonly performed procedure for treating facial paralysis. This model has the potential to be used in various experimental applications aimed at improving surgical outcomes, not only for facial paralysis but also for other muscle transfer procedures.