Abstract： Objective:To explore the feasibility and clinical efficacy of closed reduction and percutaneous pinning fixation for treating Jakob II lateral condylar humeral fractures in children under arthroscopy by direct visualization.Methods:From January 2019 to December 2021, retrospective analysis was performed for 46 hospitalized children with Jakob II lateral condylar humeral fractures. There were 30 boys and 16 females with an average age of (6.2±2.1)(2-10) years. The involved side was left (n=20) and right (n=26). Operative duration, healing time, complications and elbow motion were recorded. Elbow function was assessed by the scores of Broberg & Morrey.Results:All fall fractures were fresh with an average interval from injury to surgery (2.7±0.7)(2-4) days. The fractures involved olecranon (n=3) and radial neck (n=2). All fractures were successfully reduced intraoperatively under arthroscopy by direct visualization. Percutaneous pinning and internal fixation was performed after reduction. Intraoperative radiograph revealed satisfactory reduction. Average healing time was (7.4±0.8)(6-8) week and average operative duration (37.6±4.2)(36-45) min. During an average follow-up period of (21.5±5.2)(13-30), there was no instance of pin tract infection, nonunion, delayed union or malunion. At the final follow-up, range of motion of affected elbow joint was lost in flexion (3.3±1.1)° and in extension (2.8±0.9)° as compared with contralateral side. According to the scale of Broberg & Morrey, elbow functions were excellent (n=43) and decent (n=3).Conclusions:Arthroscopic direct reduction and percutaneous fixation are both safe and efficacious for lateral humeral condylar fractures in children. It not only minimizes soft tissue dissection, but also lowers the risks of malunion or avascular necrosis.