An experimental study on inserting an EMG electrode to the superior head of the human lateral pterygoid muscle.

To elucidate a safe and accurate method for inserting an EMG electrode into the superior head of the lateral pterygoid muscle (SLP), the anatomical relationship between the maxillary artery and SLP was examined, and the direction and distance of the EMG electrode inserted via an intra-oral route were measured in 22 human cadavers.An intra-oral approach was better than an extra-oral approach, because the maxillary artery generally ran laterally in close relation to the SLP. To avoid injuring the maxillary artery, the electrode should be inserted through the mucobuccal fold around the distal root of the upper first molar. The optimal angle of the electrode against the Camper plane was approximately 40° upward. As well against the sagittal plane was approximately 7° outward. The optimal distance from the intra-oral inserting point to the muscle was 40-45mm.Although these findings are useful for recording EMG activity of this muscle, it is necessary to consider carefully various differences in recording sides, sex and dentition of upper molars.