DEVELOPMENT OF AN IN VIVO ULTRASOUND PROTOCOL TO STUDY THE MUSCULOAPONEUROTIC ARCHITECTURE OF THE MASSETER DURING MANDIBULAR PROTRUSION AND LATERAL EXCURSION

Abstract

Background Temporomandibular disorders (TMDs) affect 5% to 12% of the population and lead to disability and pain. It has been suggested that architectural changes occur in the masseter muscle (MM) in TMDs. However, studies on normal in vivo MM architecture are scarce. Previously, our laboratory examined MM architectural changes during maximum intercuspation. Objective This work is an extension of our earlier studies in that it incorporates border jaw movements. It is hypothesized that a prototype in vivo ultrasonography protocol that will detect MM architectural changes during mandibular protrusion and lateral excursion can be developed. Materials and Methods The study was on the development of a prototype in vivo ultrasonography protocol based on cadaveric data. Results A protocol was successfully developed by identifying optimal probe positions and sites to visualize the MM laminae in mandibular protrusion and lateral excursion. The development involved correlation of anatomic specimens with in vivo ultrasonography, which enabled quantification and comparison of fiber bundle length, muscle thickness, and aponeurotic height. Discussion A novel ultrasonography protocol that will facilitate better understanding of normal MM morphology during mandibular protrusion and lateral excursion was developed. In the future, this protocol could be used as a basis to study MM changes in TMDs. Temporomandibular disorders (TMDs) affect 5% to 12% of the population and lead to disability and pain. It has been suggested that architectural changes occur in the masseter muscle (MM) in TMDs. However, studies on normal in vivo MM architecture are scarce. Previously, our laboratory examined MM architectural changes during maximum intercuspation. This work is an extension of our earlier studies in that it incorporates border jaw movements. It is hypothesized that a prototype in vivo ultrasonography protocol that will detect MM architectural changes during mandibular protrusion and lateral excursion can be developed. The study was on the development of a prototype in vivo ultrasonography protocol based on cadaveric data. A protocol was successfully developed by identifying optimal probe positions and sites to visualize the MM laminae in mandibular protrusion and lateral excursion. The development involved correlation of anatomic specimens with in vivo ultrasonography, which enabled quantification and comparison of fiber bundle length, muscle thickness, and aponeurotic height. A novel ultrasonography protocol that will facilitate better understanding of normal MM morphology during mandibular protrusion and lateral excursion was developed. In the future, this protocol could be used as a basis to study MM changes in TMDs.