Dual versus Single Innervation of Gracilis Free Functional Muscle Transfer in Facial Paralysis: Long-Term Resting and Dynamic Outcomes

Background: The purpose of this study was to compare long-term tone and excursion in single- versus dual-innervated free functional muscle transfer (FFMT) in patients with longstanding facial paralysis. Methods: Patients with longstanding facial palsy treated with an FFMT innervated either by a nerve-to-masseter graft (single-innervation group) or nerve-to-masseter and cross-facial-nerve grafts (dual-innervation group) were included. One-year minimum follow-up was required. Outcome measures, based on standardized photographs, included excursion, smile angle, teeth exposure, commissure height deviation, and upper lip height deviation in repose and in closed and open-teeth smile preoperatively and at 3 months, 1 year, and 3 years postoperatively. Emotrics software and ImageJ software were used to take measurements. Between-group and within-group longitudinal comparisons were analyzed. Results: At 3 years (single, n = 24; dual, n = 13), significance was found between groups in commissure position (single, 26.42 mm versus dual, 31.51 mm; P < 0.0001) and excursion with open-mouth smile (single, 31.32 mm versus dual, 26.59 mm; P < 0.001). Single-innervation FFMT within-group analysis lacked significant improvement in commissure height deviation and upper lip height deviation at 3 years in repose, whereas the dual-innervation group revealed significant improvements (3.67 mm [P < 0.001], 3.17 mm [P < 0.001], respectively). Teeth exposure revealed an increase in the dual-innervation group (single, 35.753 mm2 versus dual, 64.177 mm2), but significance was not observed. Conclusion: Dual-innervated FFMT revealed improvements in resting tone and teeth exposure with minimal decrease in smile excursion compared with single-innervated FFMT.