Determining the location of the internal maxillary artery on ultrasonography and unenhanced magnetic resonance imaging before orthognathic surgery.

The purpose of this study was to examine the efficacy of ultrasonography (US) and unenhanced magnetic resonance imaging (MRI) to determine the location of the internal maxillary artery (IMA) before orthognathic surgery. The study subjects were 19 patients (seven males and twelve females) with mandibular prognathism seen at the authors' institution between March 2012 and April 2013. The distance from the skin to the IMA (S-IMA) and the distance from the mandibular notch to the IMA (MN-IMA) were measured. Using the US and coronal MRI images, S-IMA(cl) and MN-IMA(cl) in the closed position and S-IMA(op) and MN-IMA(op) in the open position were measured at a total of four points in each cross-section. There were significant correlations between the distances measured on coronal MRI and US for all groups (P<0.05). A total of 35 (92%) IMAs were classified as clear and three (8%) as unclear based on the US findings. Regarding the location of the IMA, 37 of the 38 sides studied (97%) were of the lateral type, while only one (3%) was of the medial type. The results of this study indicate that US can be used effectively to determine the location of the IMA.