Anatomy And Three-dimensional Visualization Reconstruction Of Labiomandibular Fold Area Using Serial Sections

Objective: The aim of this study is to observe the locations, characteristics and adjacent relationships of the anatomical structures of the labiomandibular fold by anatomy and serial tissue sections. Discussing how to establish a three-dimensional visible virtual labiomandibular fold model and conducting the research can provide anatomical basis for the morphological study of the labiomandibular fold and the improvement of facial rhytidectomy.Methods:(1) The methylene blue dye was injected into the jowl fat compartment and the labiomandibular fat compartment which were located in one side of the face of adult fresh cadaveric head(3 male, 1 female), the labiomandibular fold area was the uncolored region which between the two colored fat compartments.(2) On the other side of the face, combining with the observation by eyes, we selected symmetrical region of the objectively marked labiomandibular fold to dissect layer by layer, meanwhile, the locations, characteristics and adjacent relationships of the anatomical structures of the labiomandibular fold were observed carefully. During the experiment, some related tissues were measured by vernier caliper and recorded by the text and image.(3) The symmetrical region of the marked labiomandibular fold with the methylene blue dye(step(1)), about 40.90×11.23×13.00 mm, was cut, dehydrated, imbedded in paraffin and serially sliced in cross-section with the thickness of 10 μm. The means of screening sections was to retain one piece in every eight pieces, and finally, the total number of the collected sections was 450. After that, one-tenth of the prepared sections(45 pieces) were extracted in equal interval, which were used to perform Masson stain. The others(405 pieces) were stained with HE. The sections with HE stain were photographed by HD digital camera, then the two-dimensional images were registrated by Adobe Photoshop CC software. Image segmentation and reconstructing three-dimensional model of the labiomandibular fold were both operated on the computer with 3D-DOCTOR 4.0 software.Results:(1) Results of the anatomy: The labiomandibular fold is the area of the face which located in the surface of the depressor anguli oris muscle and extends from the mouth corner to the mandibular border. The anatomical levels of the labiomandibular fold, from top to bottom, are skin, subcutaneous fat, muscles, submucosa and mucosa. However, when the labiomandibular fold is distributed in the mandible body, the anatomical levels of which are skin, subcutaneous fat, muscles, loose connective tissue and periosteum. There are two planes of muscles in the labiomandibular fold area: the risorius muscle, the depressor anguli oris muscle and the platysma muscle appear in the first plane, the depressor labii inferioris muscle occurs in the second plane. The above mentioned muscles which close to the corner of the mouth interdigitate among the muscle fibers of the orbicularis oris muscle. The superior boundary of the labiomandibular fold is formed by the cutaneous insertion of the depressor anguli oris muscle around the mouth corner. The labiomandibular fold ligament is a kind of false ligament, which is on the upper one-third or one-half of the crease. The lower half of the labiomandibular fold has no distinct anatomic component until the level of the mandibular ligament. The inferior boundary of the labiomandibular fold is the mandibular ligament. It originates from bone along a line that is about a centimeter above the mandibular border and which extends along the anterior third of the mandibular body. The fibrous bundles of the mandibular ligament crisscross with the muscle fibers of the platysma muscle.(2) Results of the histology and the three-dimensional visualization: The results of the histologic evaluation are consistent with the findings of the gross anatomy. The 3D model reproduces the morphology of the labiomandibular fold in a tridimensional way, which shows the spatial positions and the adjacent relationships of some primary structures, such as skin, subcutaneous fat, the depressor anguli oris muscle, the mandibular ligament and so on. Moreover, the recognized structures can be displayed singly or in the pattern of collocation. The three-dimensional model of the labiomandibular fold can also be freely rotated, enlarged, condensed and cut in an arbitrary direction.Conclusion:(1) The labiomandibular fold represents an anatomical border between the jowl fat compartment and the labiomandibular fat compartment. The superior and inferior boundaries of the labiomandibular fold are the labiomandibular fold ligament and the mandibular ligament, respectively.(2) The serial sections of the labiomandibular fold are acquired successfully through the tentative study of the larger tissue serial sections with paraffin method. In the end, the three-dimensional visible model of the labiomandibular fold is established by means of the image processing softwares. The finished model has excellent showing features, which can provide several cognitive platforms about the morphological characteristics and the anatomical structures of the labiomandibular fold. In addition, it also has a certain degree of directive significance to modify the rhytidectomy of the lower face.