New Insights Into 3-Dimensional Anatomy of the Facial Mimetic Muscles Related to the Nasolabial Fold: An Iodine Staining Technique Based on Micro-Computed Tomography.

Abstract

This study aimed to introduce a novel approach to study the facial mimetic muscles (FMMs) related to the nasolabial fold (NLF) and realize the visualization of complex 3-dimensional (3D) structures of the FMM. Micro-computed tomography (micro-CT) and iodine staining technique were used to obtain the 2-dimensional radiographs of the FMM. Materialise Mimics software was then used to reconstruct the 3D model of the FMM. The zygomaticus major muscle was not directly connected to the orbicularis oris muscle (OOM). The terminal fibers of the zygomaticus major muscle were located in the levator anguli oris. The surface of the FMM was covered with some unknown muscle fibers in the NLF. The terminal fibers of the zygolabialis ended in the middle of the ipsilateral OOM rather than the edge of the OOM. At the same anatomical level, the FMM fibers were so closely connected to each other that they were not separated by adipose tissue. A detailed 3D sequence of the muscle fibers in the modiolus at the corner of the mouth was determined. The muscle fibers in the modiolus were organized rather than disorganized. The terminal fibers of the levator anguli oris were located at the terminal fibers of the musculus depressor anguli oris at the corner of mouth. Although the micro-CT had many disadvantages, the micro-CT combined with iodine staining technique enabled the 3D anatomical study of the FMM related to NLF. We imported the 2-dimensional images obtained by micro-CT scanning into Mimics software, successfully reconstructed the FMM related to the NLF, and finally obtained images of complex 3D structures of the FMM related to the NLF. The shapes, positions, and 3D spatial relationships between the FMM related to the NLF were clearly visualized. The novel insights into the 3D anatomy of the FMM related to NLF may help understand the formation of the NLF. Finally, the results of this study may help improve rejuvenation surgery of the NLF in the near future.