Change of lateral pterygoid muscle and temporomandibular disc position after bi-maxillary surgery in class II and III patients.

Abstract

The purpose of this study was to examine changes in lateral pterygoid muscle and temporomandibular joint (TMJ) disc position in classes II and III patients, before and after bi-maxillary surgery. The subjects were comprised of 48 patients (96 sides), 23 of whom were diagnosed as class II and 25 as class III patients who underwent Le Fort I osteotomy and sagittal split ramus osteotomy (SSRO). The cross-sectional measurements of the lateral pterygoid muscles were measured at two levels of horizontal plane images (condyle and mandibular notch levels) by computed tomography (CT), before and 1year after the operation. The relationship between these measurements regarding lateral pterygoid muscle and disc position by magnetic resonance image (MRI) was also examined statistically. Preoperatively, class II was significantly larger than class III in condylar angle at the upper level and in long diameter, square, condylar angle, and muscle angle at the lower level (P < 0.05). After 1year, class II was significantly larger than class III in condylar angle, long diameter, and muscle angle at the upper level and in long diameter, short diameter, square, condylar angle, and muscle angle at the lower level (P < 0.05). TMJ disc position classification correlated significantly with condylar angle at the upper level and long diameter and condylar angle at the lower level (P < 0.0001). This study suggested that there were differences in the cross-sectional measurements of the lateral pterygoid muscles between class II and class III patients, before and after bi-maxillary surgery.