Muscle Foreshortening after Free Gracilis Transfer for Smile: Where? When? Why?

BACKGROUND: Gracilis free muscle transfer (GFMT) remains the standard for smile restoration in patients with longstanding facial palsy. Resting oral commissure lateralization (ROCL) following GFMT is aesthetically unappealing and can cause functional problems including dysarthria and oral incompetence. The risk factors for ROCL following GFMT are poorly understood. METHODS: Of all patients who underwent GFMT for smile restoration from 2003 to 2021, patients with subsequent ROCL were identified from a facial nerve database using predetermined search criteria. Medical records were reviewed to identify potential risk factors for muscle foreshortening. RESULTS: Of 412 patients who underwent successful GFMT since 2003, 41 patients (10%) subsequently developed ROCL. ROCL rates varied significantly based on gracilis innervation source, with ipsilateral cranial nerve VII innervation and dual innervation (crossfacial nerve graft plus ipsilateral-to-masseter nerve) demonstrating the highest foreshortening rates (27.3% and 15.4%, respectively), compared with the lowest rates of foreshortening when the gracilis muscle was innervated by the crossfacial nerve graft alone (3.2%) ( P = 0.005). Patients with a history of irradiation to the surgical field were significantly more likely to develop ROCL (22%) compared with those without a history of irradiation (8.6%) ( P < 0.001). Furthermore, the rate of ROCL was significantly higher among patients who underwent concurrent stabilization of the nasolabial fold using a wide band of fascia lata (20.8%), compared with those who did not (6.6%) ( P < 0.001). CONCLUSION: The authors report potential risk factors for ROCL following GFMT for smile restoration, including innervation source, radiation history, and concurrent fascia lata static suspension. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.