An image-based method for quantification of lateral pterygoid muscle deformation

The aims of this study were to present a method quantifying and visualizing the deformation of subject-specific lateral pterygoid muscles (LPM) during a simulated jaw-opening movement. A normal adult male subject underwent magnetic resonance (MR) scans of the head at three mandibular positions: mandibular rest (M0), medium jaw-opened (M1), and maximum jaw-opened (M2) positions. The 3D models of the LPM were reconstructed from the three sets of MR images. The deformations of each muscle in the two cases (M0->M1 and M1->M2) were quantified in terms of the displacements of region correspondences between the muscle models before and after the mandibular position changed. The 3D models of the subject-specific LPM were reconstructed, and the directions and magnitudes of deformations of each muscle in the two cases were accurately quantified and visualized in the three anatomic planes. The functional activities along the entire body and at specific compartments of subject-specific LPM were quantified and visualised using the quantified 3D deformations of the LPM as a new descriptor. The presented method defined the deformations of the subject-specific LPM, and revealed the anatomic architectural and biomechanical characteristics of the subject-specific LPM appropriately and meaningfully in the simulated jaw-opening movement.