Abstract:Background and Aims To overcome the limitations of the transoral endoscopic thyroidectomy vestibular approach, such as restricted operative space and high complication risks, our team proposed a modified technique—endoscopic thyroidectomy via oral vestibule and submandibular approach (ETOSA). Preliminary studies have confirmed its safety and feasibility. This study aims to systematically evaluate the key factors affecting postoperative complications and operative time in ETOSA, explore the interactions among these variables, and construct a learning curve model to support its broader clinical adoption.Methods A retrospective analysis was conducted on 125 patients with papillary thyroid carcinoma who underwent ETOSA at Xiangya Hospital, Central South University, between March 2022 and March 2023. Clinical characteristics, surgical parameters, and postoperative complications were extracted. A random forest model was employed to identify the major influencing factors for complications and operative time, as well as their interaction effects. Partial dependence plots based on case sequence were used to generate the learning curve.Results All 125 patients successfully underwent ETOSA with no conversion to open surgery. The median operative time was 95.0 min, and the median intraoperative blood loss was 15.0 mL. The overall postoperative complication rate was 16.0%, with no cases of permanent hypoparathyroidism or hypocalcemia. The average neck appearance score was 1.05, indicating high patient satisfaction. The random forest analysis identified case number, surgical extent, lymph node yield (LNY), Hashimoto's thyroiditis (HT), and body mass index (BMI) as the key predictors of postoperative complications, while surgical extent, case number, LNY, HT, and blood loss were the key factors affecting operative time. A significant positive interaction was observed between case number and both surgical extent and HT, particularly in the first 20 cases, suggesting a higher risk during the early learning phase. The learning curve analysis indicated that surgical proficiency stabilized after 20 cases. Operative time and complication rate in the proficient phase were significantly lower than those in the learning phase (90.0 min vs. 102.5 min; 11.4% vs. 40.0%, both P<0.05).Conclusion ETOSA is a safe and feasible technique characterized by minimal invasiveness, favorable cosmetic outcomes, and a relatively short learning curve. case number, surgical extent, LNY, HT, BMI, and blood loss are key factors affecting complications and operation time.