Computed Tomography‐based Morphological Analysis for Intraoral Vertical Ramus Osteotomy in Patients with Mandibular Prognathism

AimIntraoral vertical ramus osteotomy (IVRO) is an orthognathic surgery for patients with jaw deformity. To avoid complications associated with IVRO, understanding the position of the mandibular foramen and shape of the mandibular ramus in patients with mandibular prognathism is important, which only few studies have reported. Most studies have been performed with dry skulls of older people without jaw deformity. This study aimed to examine the position and shape of the mandibular foramen and ramus, respectively, using computed tomography in patients with mandibular prognathism. MethodsThe study was performed on 50 Japanese patients who underwent IVRO. We examined the position of the mandibular foramen against the occlusal plane, distance between the posterior border of the mandible and mandibular foramen, and thickness of the mandibular ramus. ResultsThe mandibular foramen was vertically located above the occlusal plane at a distance of 2.6 +/- 5.1 and 1.2 +/- 5.1 mm in men and women, respectively. The distances between the mandibular ramus and foramen, measured with the posterior border line of the mandibular ramus as a criterion, were 15.9 +/- 2.2 and 14.4 +/- 2.1 mm in men and women, respectively. The thickest parts of the mandibular ramus were 6.8 +/- 1.6 and 6.9 +/- 0.9 mm in men and women, respectively. ConclusionKnowledge of the accurate position of the mandibular foramen is important for a safe IVRO. Mandibular ramus osteotomy line should be within 10 mm from the posterior border of the mandibular ramus, to avoid inferior alveolar nerve damage.