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

Objectives 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. Materials and methods 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 1 year after the operation. The relationship between these measurements regarding lateral pterygoid muscle and disc position by magnetic resonance image (MRI) was also examined statistically. Results 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