Incidence of Pneumothorax Experienced After Orthognathic Surgery The purpose of this study is to evaluate the frequency of pneumothorax following orthognathic surgery and describe its clinical presentation. A retrospective analysis of a hospital database was carried out on consecutive patients with normal presurgical clinical assessment, laboratory findings, and chest X-ray who underwent orthognathic surgery from January 2007 to September 2018 in the Department of Oral and Craniomaxillofacial Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine. Two patients (0.038%), 1 male (age 20 years) and 1 female (age 32 years), complained of respiratory difficulty and chest pain and were clearly diagnosed with postoperative pneumothorax by radiographic chest X-rays from a sample of 5229 consecutive patients during the study period. Intercostal drainage under local anesthesia was performed immediately and the treatment effects for both patients were satisfactory. The present study findings indicate that although orthognathic surgeries can be safely performed in patients with craniofacial anomalies, some unexpected complications such as pneumothorax may occur. Therefore, accurate postoperative follow-up must be done in every patient to monitor possible clinical complications. Patients who experience respiratory difficulty and postoperative chest pain may have pneumothorax, and once it is diagnosed, treatment should be promptly carried out to eliminate further severe sequelae. Address correspondence and reprint requests to Xudong Wang, DDS, MD, and Lei Zhang, DDS, PhD, Department of Oral and Craniomaxillofacial Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhi-Zao-Ju Road, Shanghai 200011, People's Republic of China; E-mail: xudongwang70@hotmail.com; oral66@126.com Received 26 April, 2019 Accepted 11 May, 2019 KL and TZ contributed equally to this work. This project was supported in part by the Three-Year Plan for Clinical Skill and Innovation Ability Training in Shanghai Municipal Level Hospitals (grant no. 16CR3019A), the Clinical Research Program of the Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine (grant no. JYLJ006), the Interdisciplinary Program of Shanghai Jiao Tong University (project number YG2017ZD03), and the Shanghai Science and Technology Committee (project no. 18410712000). The authors report no conflicts of interest. © 2019 by Mutaz B. Habal, MD.