The authors verified the anatomical location of the mandibular foramen, lingula and antilingula in dry mandibles, aiming to obtain information that could be used when performing mandibular osteotomies. Forty-four mandibles (88 sides) were evaluated. The distances were measured using a sliding calliper, with the mandibles fixed in a reproducible position. Results showed that the mandibular foramen is on average 5.82 mm below the lingula. Regarding the statistical comparison between the mandibular foramen entrance and the antilingula position, there is no correlation between the position of those two structures in the studied sample. The mandibular foramen is slightly posterior in relation to the centre of the ramus. The lingula is an important anatomic landmark for ramus surgery, and for determining the distance to the mandibular foramen entrance. The use of the antilingula as a landmark for the position of the vertical ramus osteotomy is not recommended.
The sagital split ramus osteotomy was first described by S chuchardt in 1942 and later modified by T rauner and O bwegeser in 1957 . It is the most widely used surgical technique for correction of mandibular positioning, owing to several advantages, such as the intraoral approach, broad bone interface, the possibility of rigid internal fixation and early jaw function. Other surgical osteotomy techniques may be necessary, such as the vertical ramus osteotomy or the inverted L osteotomy. The vertical ramus osteotomy may be advantageous for mandibular setbacks, regarding inferior nerve hypoesthesia and passive condylar position .
Some anatomic landmarks are described in textbooks as surgical reference marks for these surgical procedures. The lingula of the mandible is a tongue-shaped bone projection on the medial aspect of the ramus. It is a very important landmark as it lies in close proximity to the mandibular foramen and these two anatomic structures are of clinical significance for the maxillofacial surgeon because of their relation to the inferior alveolar nerve .
The antilingula is a bone tubercle on the lateral surface of the mandibular ramus. Some authors describe the antilingula as the expression of the underlying mandibular foramen on the medial side of the mandible. Thus, surgical procedures could be performed superior and posterior to the antilingula without risk of damage to the inferior alveolar nerve . Other studies have shown that when utilising the vertical ramus osteotomy from either an intraoral or extraoral approach, with the antilingula as a guide, it does not guarantee the absence of nerve injury. Those studies show an incidence of inferior alveolar nerve palsy in up to 30% of those cases .
Other studies have been carried out to determine whether the antilingula can be consistently identified and whether there was a variation between different observers, because that is another issue when using this landmark. Many mandibles seem not to have any antilingula, or at least its recognition was not possible .
Materials and methods
Forty-four human cadaver dry mandibles were used for this study. The age and sex of the mandibles were unknown. The presence of teeth in the mandibles was noted. In a first stage, two independent observers palpated the lateral aspect of the ramus of the mandible in an effort to identify the antilingula and determine the antilingula spot for future measurement.
The mandibles were measured according to predetermined points for the mandibular foramen, lingula and antilingula ( Figs 1–3 ). The mandibles were measured over an Erickson platform using a digital sliding calliper (Brow & Sharpe Digit-Cal Plus), and the distances were always measured in millimetres. For the horizontal distances a special apparatus with the union of two callipers at exactly 90° between them was developed and used ( Fig. 4 ).
All the measurements were carried out by the same person, and at the antilingula region they were taken at the spot that was predetermined by palpation. The lingula point used in this study was the most medial prominence of the lingula, independently of its shape. The X measurement indicated the distance in millimetres found between the most anterior part of the mandibular foramen, lingula and antilingula points to the anterior border of the mandibular ramus in a straight horizontal line; the Y measurement represented the distance between the most posterior part of the mandibular foramen, lingula and antilingula points to the posterior border of the mandibular ramus in the same horizontal orientation; the W measurement determined the distance between the lower point of the mandibular foramen, lingula and antilingula points to the mandibular base in a vertical straight line; the Z measurement determined the distance between the same initial points as for the W distance, to the lower point of the sigmoid notch. The horizontal distances were taken always parallel to the mandibular base, whilst the vertical were always taken perpendicular to the horizontal measurements.
Measurement A was defined as the distance between the lingula point and the most inferior part of the mandibular foramen in a superoinferior direction and B as the distance between the most anterior point of the mandibular foramen to the lingula point in a anteroposterior direction, to define average values for the distance between the lingula and mandibular foramen entrance ( Fig. 5 ). H measurement was defined as the distance between the lower point of the mandibular foramen entrance to a point determined by a straight line parallel to the alveolar bone border plane and continuous to those structures, attempting to show the average height between the mandibular foramen entrance and the alveolar bone border ( Fig. 5 ).
The values obtained were tabulated, the mean average and respective standard deviations (SDs) were calculated for all distances studied and statistical analysis was carried out to verify if there was any positional relation between the mandibular foramen entrance and the antilingula. The Wilcoxon test was applied due to lack of normal distribution. The significance level adopted was 5% ( p < 0.05). The SAS for Windows (Statistical Analysis System), version 9.1.3, SAS Institute Inc., 2002–2003, Cary, NC, USA was used.
The two examiners were not able to find the antilingula point by palpation in 15 sides of the studied sample specimens (15%). Another 7 specimens presented no antilingula at the booth sides, whilst in one it was unilateral. The average respective SDs are given in Tables 1–3 for the values in each one of the four directions or measurements studied, regarding the three anatomic structures (mandibular foramen, lingula and antilingula).