Abstract:

Objective To dissect soft tissue structure around the mandibular angle and the mandibular nerve canal accurately, as to provide anatomical reference for the mandibular angle hypertrophy operation. Methods Twenty formalin-fixed adult head-and-neck specimens were observed and measured for facial arteries and veins, the marginal mandibular branch of the facial nerves, and the vessels and nerves of masseter muscle. Five lines positioned according to the characteristic structures of the mandible were used for the measurement of mandibular nerve canal. The safety range of the soft tissue structure and the mandibular nerve canal，external carotid artery, maxillary artery, and transverse facial artery were calculated. Results The distance between the facial artery and the mandibular angle is 23.18-36.28 mm. Facial artery to the anterior margin of masseter muscle is -9.51-9.27 mm. Separation between the facial vein and the mandibular angle is 17.79-32.03 mm. The marginal mandibular branch of the facial nerve is close to the mandibular angle and the lower edge of the mandible, measurements showed a distance of -8.57-10.70 mm towards mandibular angle. At anterior masseter muscle, separation between mandibular branches and the lower edge of the mandible is-8.83-11.06 mm. The four major sources of masseter arteries are the masseter branch of the facial artery, external carotid artery, maxillary artery, and transverse facial artery. The masseter nerve entered the masseter muscle alongside with the masseter artery. In the five cross sections, the disctance from mandibular nerve canal to the lateral mandibular point is more than 10.50 mm, 14.72 mm, 15.60 mm,8.53 mm and 6.74 mm, respectively. Conclusion Attention should be paid, when undermining soft tissue in the mandibular angle, three main structures specifically the facial artery and the marginal mandibular branch of facial nerve located at the anterior aspect of mandibular muscle, and the mandibular marginal branch of the facial nerve located at the mandibular angle are prerogative. Layers removed from the masseter muscle are best done at the thickest region of the middle inferior aspect. A guide safety line can be drawn quickly during osteotomy on the buccal bone palate of the mandible based on the safety range of mandibular nerve canal.

Key words: Mandibular angle hypertrophy, Mandibular nerve canal, Osteotomy, Anatomy, Adult