Sexual dimorphism and geographic variance: their impact on the reliability of the antilingula as a landmark in human mandibular surgery

Abstract The intraoral vertical ramus osteotomy (IVRO) is an orthognathic procedure used to correct dentofacial abnormalities, performed by approaching the lateral aspect of the mandibular ramus. This approach precludes visualisation of the inferior alveolar nerve (IAN) on the medial side, thereby placing it at risk of iatrogenic damage. The antilingula, a bony prominence on the lateral mandibular ramus, has been proposed as a landmark for prediction of IAN location during IVRO. The current study aimed to evaluate variation in incidence and position of the antilingula, and therefore determine its suitability as a surgical landmark during IVRO. This study included 480 dry hemimandibles from 8 geographic populations from the Duckworth Collection in Cambridge. Skulls were sexed by visual analysis of dimorphic traits. Positional relationships were determined through digitisation of 9 anatomical landmarks. The antilingula was identified in all specimens. No significant difference was identified in the positional relationship between the antilingula and mandibular foramen between sexes. Multiple differences were identified in this relationship between geographic populations. Our data showed that, irrespective of geographical variation, an osteotomy performed 8 mm posterior to the antilingula would avoid the mandibular foramen in 98.8% of cases.