Histological study of the capsular and discal insertions of the lateral pterygoid muscle

Abstract

Many variations of the lateral pterygoid muscle (LPM) anatomy have been described and, because of its assumed insertions on the intra-articular disc, the muscle is supposed to pull it during mouth movements. In clinics, the LPM has been held responsible for some temporomandibular joint (TMJ) internal derangement. The aim of this study was therefore to verify the insertions of the LPM onto the disc and joint capsule, using macro-anatomical dissection of human material and histological analysis under the microscope. The results showed great variability in the measurements (percentage coefficient of variation: 25 < CV% < 82). No correlation could be found between the different parameters measured (Spearman correlation coefficient: 0.17 < rho < 0.61), nor any significant difference between the parameters measured on the left and right TMJs of the same specimen. Scarcity and small thickness of LPM fibers attaching directly onto the intra-articular disc raises doubts about its ability to mobilize it. The authors estimated that it would be useful to improve the anatomical knowledge of the muscle in order to better understand its action on TMJ, the behavior of the disc and for the purpose of future tri-dimensional (3D) biomechanical study.