Facial paralysis disrupts the innate connection between mimetic muscles and emotions. This functional impairment poses a barrier to social interaction and consequently decreases quality of life (Nellis et al., 2017; Guntinas et al., 2007; Lassaletta et al., 2006). In the last decade, free functional muscle transfer has been the gold standard treatment approach for chronic facial paralysis. Until now, numerous reconstruction options, including options involving two mainstream donor muscles (gracilis muscle and latissimus dorsi muscle), have been introduced (Dong et al., 2018; Bianchi et al., 2016; Bae et al., 2006; Manktelow et al., 2006; Harii et al., 1998; Cuccia et al., 2005; Biglioli et al., 2012a).

As advances in the field of facial reanimation have been made globally, recovering a spontaneous smile is one of the most important goals for patients with facial paralysis. To restore a spontaneous smile, physicians have used dual innervation methods that combine the ipsilateral masseteric motor nerve and contralateral normal facial nerve branch in a single free muscle flap (Cardenas-Mejia et al., 2015; Biglioli et al., 2012b; Sforza et al., 2015; Watanbe et al., 2009; Okazaki et al., 2015; Dusseldorp et al., 2019). However, controversies still exist regarding whether the dual nerve innervation method is superior to the method involving a single motor nerve (the masseteric nerve or hypoglossal nerve) in terms of the outcomes of smile restoration after reanimation surgery (Manktelow et al., 2006; Lifchez et al., 2005).

We performed a technique involving a free latissimus dorsi muscle flap with nerve splitting (partial LD transfer) using the dual innervation method in patients with unilateral facial paralysis. An assessment was carried out to compare outcomes between the single and dual innervation methods.