The study of position of antilingula, midwaist of mandibular ramus and midpoint between coronoid process and gonion in relation to lingula of 92 Thai dried mandibles as potential surgical landmarks for vertical ramus osteotomy

This study aims to investigate positions of the antilingula (AL), the midwaist of the mandibular ramus (MW) and the midpoint between the coronoid process and the gonion (MCG) in relation to the lingula of dried mandibles. Bilateral rami of 92 Thai dried mandibles were studied. The AL, the MW, the MCG and the corresponding position of the tip of lingula (L) were marked on the external aspect of the mandibular ramus. The distances from the AL, the MW and the MCG to the L were measured in the anterior–posterior and the superior–inferior planes using computerized image analysis. The results showed the AL was discernible in 80.4% of lateral mandibular rami studied. The most of the AL was found anterior–superior to the L with a maximum distance of 5.9 mm anteriorly and 8.2 mm superiorly. The MW was frequently located anterior–inferior to the L with a maximum distance of 9.3 mm anteriorly and 9.9 mm inferiorly. The majority of the MCG was found anterior–superior to the L with a maximum distance of 9.6 mm anteriorly and 8.9 mm superiorly. A 5 mm radius from the L included 84.5% of the AL, 81.5% of the MW and 79.4% of the MCG. Medians (interquartiles) of distances from the AL, the MW and the MCG to the L were 3.4 (2.3–5.0) mm, 3.8 (2.5–5.3) mm and 4.1 (2.8–5.3) mm, respectively. In conclusion, the AL was identified in 80.4% of lateral mandibular rami studied. The AL and the MCG were commonly found anterior–superior to the lingula, whereas the MW was mostly observed anterior–inferior to the lingula. Therefore, a cut made more than a 5 mm posterior or superior to these landmarks would be in 79% of cases, within a statistically safe area avoiding encroaching upon the inferior alveolar neurovascular bundle passing immediately lateral to the lingula. Although the MW and the MCG might be alternative surgical guides when the AL is absent, their use alone as surgical landmarks is not recommended.