Page 15 - Demo

General introduction and overview113There are four true mastication muscles which make direct contact with the TMJ. Three of these muscles help to close the mouth. The masseter muscle is the ‘main closer’ of the mouth, and is further aided by the medial pterygoid muscle, which could be seen as the counterpart to the masseter muscle, yet on the medial side of the mandible. The third muscle to help close the mouth, is the temporal muscle, which inserts onto the coronoid process. However, as mastication is more than rather just opening and closing, the lateral pterygoid muscle can be seen as vital to proper masticatory function. Whereas the superior belly of the LPM inserts into the disc, allowing proper disc movement, the inferior belly inserts into the condyle and allows for protrusion of the condyles when both side contract simultaneously, leading to the mouth opening. Additionally to allowing proper disc movement, the superior belly also participates in contralateral and protrusive moment. Despite this involvement of the superior belly, the inferior one is the principal muscle for laterotrusive movement. In case of a unilateral contraction, a laterotrusive movement will occur, which is extremely important for being able to properly chew. Important to note is that, with current TMJ TJR, the LPM’s function is not retained, thus losing the possibility of laterotrusive movement.(8–11)Equally important for every surgeon to the structure of the joint are the main blood vessels and nerves surrounding the joint. The maxillary artery and superficial temporal artery provide the main vascularization to the joint. The superficial temporal artery is the terminal branch of the external carotid and can be found relatively superficially, posterolaterally to the condyle. It makes for a point of attention during a surgical exploration, especially when taking a pre-auricular approach. The maxillary artery branches from the external carotid as well, yet passes on the medial side of the mandible, between the ramus and the sphenomandibular ligament, below the sigmoid notch. This artery is important, as the arteria meningea media branches off at the level of the condyle and passes medially from it, risking being damaged when performing a condylectomy. Venous drainage is realized mainly through the pterygoid plexus and superficial temporal vein, as well as several other maxillary veins, forming the retromandibular vein.(12,13)Nikolas de Meurechy NW.indd 13 05-06-2024 10:14