Evaluating Dynamic Smile Outcomes of Free Gracilis Muscle Transfer in Pediatric Facial Palsy Using Image-Based Analysis

Background: Facial nerve palsy in children leads to significant functional impairment and facial asymmetry. While free gracilis muscle transfer (FGMT) is a cornerstone technique for smile reanimation in both pediatric and adult patients, its evaluation has mainly focused on the single metric of commissure excursion. This study seeks to evaluate the effectiveness of FGMT in restoring dynamic smiles in pediatric patients with facial palsy using image analysis. Methods: A retrospective review was conducted in children who underwent FGMT for facial palsy at a major children’s hospital between 2007 and 2020. Data collection included pre- and post-operative chart reviews and image analysis. Anthropometric measurements were obtained using a machine learning-based smile analysis software. Primary outcomes included commissure excursion, commissure angle, dental show, and smile symmetry. Statistical analysis was performed using Wilcoxon sign-rank test. Results: A total of 31 patients with an average age of 10 years underwent FGMT for smile reanimation during the study period. The most common diagnosis was Moebius Syndrome (48%). Donor nerves for gracilis neurotization included 18 ipsilateral trigeminal nerves (58.1%) and 12 contralateral facial nerves via cross-face sural nerve grafts (38.7%). Overall, 84% of patients demonstrated active gracilis contraction within a mean of 2.5 years postoperative follow up. Commissure excursion increased by 9.7 mm at one year (p<0.05) and symmetry significantly improved for commissure height, commissure excursion, upper lip height and smile angle. There were no significant improvements in dental show, commissure angle, and symmetry of dental show and lower lip height. Furthermore, only 16% of patients demonstrated clinically symmetric smiles within the follow up period. Conclusion: While FGMT effectively restores commissure excursion in pediatric patients with facial palsy, achieving multidimensional smile reanimation remains a challenge. New techniques in multi-vector free tissue transfer may help optimize FGMT outcomes in pediatric patients.

Publication History

Received: 24 March 2025

Accepted after revision: 27 July 2025

Accepted Manuscript online:
30 July 2025