Topography and Morphology of the Medial Pterygoid Muscle for the Surgical Approach of the Mandibular Ramus

Yang, Seung Jun; Hu, Kyung Seok; Kang, Min Kyu; Youn, Kwan Hyun; Kim, Hee Jin

Abstract

It has been known that the medial pterygoid muscle influences the mandibular functions related to mandibular movements. In addition, the muscle bundle of the medial pterygoid muscle influences the stability of a complete denture. Therefore, the topography of this muscle is clinically important. However, researches on the clinical anatomy related to the insertion area, and innervation, of this muscle were rare. Therefore, authors investigated the morphological and topographic characteristics of the medial pterygoid muscle by dissection of 31 Korean cadavers. The following are the results:The middle portion of the medial pterygoid muscle was the longest with the length of 59.4 degrees +/-7.1mm, and upper one third of the total length of the muscle was composed of tendon. When comparing the morphology of the insertion area of the medial pterygoid muscle and the masseter muscle in the mandibular angle region, there was no difference of the length of the insertion from the gonion to the superior margin of the insertion on the ramus. However, the length from gonion to the anterior margin of the insertion on the ramus in the masseter case was twice as long as the medial pterygoid muscle case. Insertion of the medial pterygoid was morphologically classified into six groups based on the insertion pattern and the mylohyoid groove. Type V, which the muscle fibers in the insertion of the medial pterygoid muscle were divided and did not invade the mylohyoid groove, were found the most (26.6%). Most of pterygoid branch of trigeminal nerve entered the medial pterygoid muscle through the posterior one third area or the posterior marginal area. The average length between hamulus and the region where the pterygoid branch of mandibular nerve entered the medial pterygoid muscle was 10.1mm. In conclusion, the anatomical relationship between the medial pterygoid muscle and the surrounding structures will be able to provide useful data for clinical applications.