1. Department of Surgery, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea
2. Department of Surgery, Korea University Hospital, Korea University College of Medicine, Seoul, Korea
3. Department of Otorhinolaryngology-Head and Neck Surgery, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea
4. Department of Surgery, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Korea