Intraoral vertical ramus osteotomy (IVRO) is a useful surgical procedure for mandibular setback in patients with mandibular prognathism or mandibular asymmetry. IVRO has some intraoperative complications, such as the medial trapping of the proximal segment. Several techniques have been described to overcome this problem, but none can prevent it. This technical report describes a method that prevents the medial trapping of the proximal segment during IVRO.