Anatomical localization of submandibular gland for botulinum toxin injection

The aim of this study was to document the anatomical landmarks of the submandibular gland (SMG) for a botulinum toxin injection. Thirty-four SMGs from 20 cadavers were examined. The mean length of a reference line between the angle of the mandible and the gnathion was 94.8 ± 5.9 mm, the proximal and distal point of the SMG from the angle of the mandible was 10.6% (11.5 ± 3.5 mm) and 41.8% (40.9 ± 5.2 mm), respectively. The facial artery came out of the SMG at 11.6% (14.6 ± 3.4 mm) and the position of the intersection of the facial artery with the inferior border of the mandible was located at 24.4% (28.0 ± 5.5 mm) from the angle of the mandible. The shape of the SMG was generally triangular or irregular round on the anatomical position. The mean superior-inferior diameter, anterior-posterior diameter and medial-lateral diameter of the gland was 28.8 ± 4.1, 30.0 ± 6.1 and 15.1 ± 3.5 mm, respectively. The safety zone for the injection was 20-35% from the mandible angle on the inferior view and 1.5 cm below the inferior line of the mandible on the lateral view. In addition, the needle should be inserted to a depth of 2.0 cm from the skin surface on the inferior view. These results may assist in determining a accurate localization of injection sites for the SMG, particularly for injections without ultrasound guidance.