Evaluation of Masseter Muscle Volume after Contouring of Prominent Mandible Angle by Measurement of CT Scan Image

Abstract

Purpose: The prominent mandible angle, otherwise known as “square face”, has been recognized as an aesthetic problem that needs correction by many in the Asian community. Many surgeons considered that mandible angle ostectomy alone, brings about hypotrophy of the masseter muscle. However, it was only proven indirectly (by clinical experience and histological animal experiments) and not objectively. In this study, we evaluated the volume of masseter muscle to prove the effect, objectively. Materials and method: Computed tomography (CT) images were used to measure the masseter muscle volume of normal female group (n=6), and of female patient group n=8, preoperative and early & late postoperative volumes) presenting the symptom of prominent mandible angle. The data was analyzed statistically by two-sample t-test and paired t-test using SAS (version 8.2). Results: In normal female group, volume average was 16,142±2,829.8mm. In patient group, preoperative volume averaged 24,447±4,544.5mm (p<0.0001) , early postoperative volume measured average of 31,966±50,421mm which is a 30% increase from the preoperative volume (p<0.0001). Late postoperative measurement was 20,202±4,092.3mm, which is a 20% decrease from the preoperative volume (p<0.0006). Conclusion: The bone reduction of prominent mandible angle induce the hypotrophic effect of masseter muscle after long term follow up (5 more months). This result mean that the result of mandible angle contouring surgery can be considered as combined effect of bony angle reduction and subsequent masseter muscle hypotrophy.