Rahul Shah, Milan Kapur, Cecilia Brassett, Vijay Santhanam
Introduction & aims
The intraoral vertical ramus osteotomy (IVRO) is an orthognathic procedure used in the correction of dentofacial abnormalities. During this procedure, the osteotomy is performed from the lateral aspect of the mandibular ramus, precluding direct visualisation of the inferior alveolar nerve (IAN), as it enters the mandibular foramen on the medial aspect. As such, identification of a landmark on the lateral ramus with a reliable relationship to the IAN would enable its position to be identified decreasing risk of iatrogenic damage. The antilingula is a bony prominence, formed from the action of masseter on the lateral aspect of the mandibular ramus, and has been posited as one such landmark. Variation in the position and presence of the antilingula has been described previously, however, this study looked to formally evaluate these variations across different populations and sexes.
478 dry hemimandibles from 8 different geographic populations were obtained from the Duckworth Collection, Cambridge. These were used to map the relationship between the lingula, antilingula, mandibular foramen and midwaist point of the ramus on each hemimandible. Skulls were sexed by discriminant function analysis of visually assessed sexually dimorphic traits. Positional relationships were determined through the digitisation of 9 anatomical landmarks per hemimandible.
The antilingula was identified in all 478 specimens. The antilingula was, on average, located 1.50mm anterior and 5.73mm superior to the mandibular foramen. No significant sex difference was identified in the spatial relationship between antilingula and the mandibular foramen. Multiple differences were identified in this relationship between geographic populations. Irrespective of geographic population or sex, the mandibular foramen was less than 5mm posterior to the antilingula in 90.4% of cases.
An osteotomy performed 8.6mm posterior to the antilingula during IVRO should prevent damage to the inferior alveolar nerve in 98.8% of cases.