119. Anatomic Thresholds for Significant Jowling Following Lower Facial Third Facial Feminization Osteotomies

PURPOSE: FFS procedures targeting the lower third of the face, such as gonial angle reduction or genioplasty can create inadequate skeletal support to the lower facial third, leading to a deflated soft-tissue envelope known as iatrogenic jowling. Although clinical experiences and recommendations regarding iatrogenic jowling are discussed anecdotally in the literature, quantitative data linking the extent of bony volume reduction in the lower facial third to iatrogenic jowling is currently lacking METHODS: This study investigated jowling in 13 patients who underwent FFS at a single academic medical center. Patients had undergone lower facial third procedures (i.e., genioplasty and/or mandibular contouring) and had both pre- and post-operative skull craniofacial computerized tomography (CT) and VECTRA three-dimensional (3D) imaging. Frontal and bilateral sagittal views of the face were captured using the Mimics and VECTRA 3D imaging modalities. Mimics was used to create 3D soft tissue models from CT imaging, as well as to assess the following hard tissue measurements: left and right gonial angle surface area, angle volume, intergonial distance, chin surface area, chin volume, height, and projection. Pre- and post-operative Iatrogenic jowling was assessed by two plastic surgeons using a validated 5-point photonumeric scale. RESULTS: Average age at surgery was 38 ± 12 years, average time between surgery and post-operative imaging was 7.5 ± 3.5 months for CT imaging and 9.6 ± 8.6 months for VECTRA. Average BMI was 26.8 ± 7.4 kg/m2. Zero patients were active smokers, and seven 79 (53.8%) patients were former smokers. BMI and smoking status were not significantly correlated with jowling grades. Average jowling grade was 1.77 pre-operatively and 3.15 post-operatively. Jowling grade negatively correlated with intergonial distance (r = -0.464) and chin surface area (r = -0.615). The pre- to post-operative change in jowling grade negatively correlated with the change in right gonial angle surface area (r = -0.554) and chin height (r = -0.587). A larger than 8% decrease in chin height was associated with a greater post-operative increase in jowling grade (2.0 vs 1.0), larger than 18% decrease in chin surface area was associated with a greater post-operative increase in jowling grade (2.0 vs.1.0), and larger than 12% decrease in total gonial angle surface area was associated with a greater post-operative increase in jowling grade (2.3 vs. 1.0). CONCLUSION: These findings underscore the importance of patients anticipating the risk of iatrogenic jowling, with implications for enhancing surgical outcomes in the era of virtual surgical planning, as this technology enables the quantification of expected bony reductions, offering a predictive measure for post-operative jowling based on this study’s thresholds.