One-stage free transfer of latissimus dorsi-serratus anterior combined muscle flap with dual innervation for smile reanimation in established facial paralysis

Abstract Microneurovascular free muscle transfer is the gold-standard surgical procedure for the reanimation of established facial paralysis. However, the innervation of the transferred muscle by the contralateral facial nerve is usually insufficient to produce a stable smile. Besides, the corner of the mouth sometimes moves unnaturally as if it were being pulled up because of the single-direction movement. Thus, we propose one-stage facial reanimation using free latissimus dorsi (LD)-serratus anterior (SA) combined muscle flap transfer with dual innervation. The LD-SA combined muscle flap was harvested with the thoracodorsal artery and vein as common vessels to move the corner of the mouth bidirectionally for natural smiling. The LD muscle was located in the same direction as the zygomaticus major muscle and reinnervated by dual innervation. The contralateral facial nerve was coapted with the thoracodorsal nerve, and the ipsilateral masseter motor nerve was inserted into the LD muscle by intramuscular neurotization. The 6th or 7th SA muscle was located in the same direction as the risorius muscle and reinnervated by neurorrhaphy of the long thoracic nerve and the thin branch of the ipsilateral masseter motor nerve. Since 2015, seven patients have been treated with this method without complications. On average, SA muscle movement was detected in voluntary biting at 3.1 months, and spontaneous smiling occurred 7.7 months after surgery. All patients developed a spontaneous natural smile. This method for established facial paralysis has the potential to improve the quality of the reconstructed smile and the unstable results of conventional single-innervation-single-muscle transfer.