Morphological analysis and three-dimensional reconstruction of the SMAS surrounding the nasolabial fold

Histomorphological analysis of the superficial musculoaponeurotic system in Macaca mulatta species

INTRODUCTION

The superficial musculoaponeurotic system (SMAS) is a well described facial functional unit in humans. SMAS connects mimic musculature to the skin having many implication in facial mimic expression. One of the various morphological and physiological analogies in human and Macaca mulatta species is the facial mimic. The present study analyzed Macaca mulatta species SMAS morphology and its facial topographical differences and compared this with human SMAS tissue morphology.

MATERIAL AND METHODS

Macaca mulatta full-graft tissue blocks of skin, subcutaneous tissue and mimic muscles from five topographical different facial regions (Regio Temporalis, Regio Buccalis, Regio Infraorbitalis, Regio Angulus Oris and Regio Mandibularis) were collected postmortem from eight individuals (n = 8) at the German Primate Center, Leibniz Institute for Primate Research in Göttingen (DPZ) and studied histologically. Haematoxylin-eosin and azan stained histological serial sections of full-graft tissue blocks were analyzed and SMAS topographical differences evaluated.

RESULTS

SMAS typical tissue morphology was recognized in all Macaca mulatta histological serial sections (n = 780). Regio Infraorbitalis Macaca mulatta SMAS (MmSMAS) morphology was similar to human infraorbital SMAS morphology (type I SMAS). Suborbicularis oculi fat pad was recognized in Macaca mulatta samples. Human type I similar SMAS morphology was demonstrated over Macaca mulatta Regio Temporalis and Regio Buccalis. Regio Angulus Oris and the cranial area of the Regio Mandibularis presented human type II similar SMAS morphology. Type IV MmSMAS was closely related to the parotid gland tissue presence. The cervical area of the Regio Mandibularis presented human type V similar SMAS morphology.

CONCLUSIONS

SMAS is a complex fibro-musculo-adipose tissue network and probably an important pivot in Macaca mulatta facial system supporting mimic expression. This study provided insights into MmSMAS typology and similarity with human SMAS tissue morphology.

"Untying the knot": The primitive orofacial muscle architecture in the gorilla (Gorilla gorilla) as a key to the evolution of hominin facial movement

The anatomical underpinnings of primate facial expressions are essential to exploring their evolution. Traditionally, it has been accepted that the primate face exhibits a "scala natura" morphocline, ranging from primitive to derived characteristics. At the primitive end, the face consists of undifferentiated muscular sheets, while at the derived end there is greater complexity with more muscles and insertion points. Among these, the role of the human modiolus ("knoten" in German) has been emphasized. Recent studies have challenged this view by revealing significant complexity in the faces of several non-human primates, thereby rejecting the linear notion of facial evolution. However, our knowledge of the facial architecture in gorillas, the second closest living relatives to modern humans, remains a significant gap in the literature. Here, we present new findings based on dissection and histological analysis of one gorilla craniofacial specimen, alongside 30 human hemifaces. Our results indicate that while the number and overall arrangement of facial muscles in the gorilla are comparable to those of chimpanzees and modern humans, several orofacial features distinguish the gorilla's anatomy from that of hominins. Among these are the absence of a modiolus, the continuity of muscular fibers over the region of the mouth corner, the flat (uncurving) sheet of the orbicularis oris muscle, and the insertion of direct labial tractors both anterior and posterior to it. Collectively, the anatomical characteristics observed in the gorilla suggest that the complex anatomy of the hominin face should be considered synapomorphic (shared-derived) within the Pan-Homo clade.

Complications of fillers in the lips and perioral area: Prevention, assessment, and management focusing on ultrasound guidance

An ever-increasing interest in perioral rejuvenation with dermal fillers reflects the esthetic importance of this region. However, filler injections in the lips and perioral area have been associated with various complications. Such complications are classified according to severity (mild, moderate, severe) or by the time of onset: immediate (within 24 h after injection), early (24 h to 4 weeks post-procedure), and late or delayed (>4 weeks after injection). While most complications are mild and manageable, vascular compromise, infections, and the development of delayed-onset nodules may significantly undermine the ultimate esthetic outcome and cause substantial morbidity. These more serious complications often require more invasive treatment modalities. This article details the prevention and management of such adverse events and discusses safe filler injection principles, including safety recommendations for the lips. Lastly, we highlight the use of ultrasound guidance in complication prevention (vascular mapping, filler identification, location, and extent), assessment (identification of intravascular embolus or external vascular compression by the filler implant), and management (real-time imaging of hyaluronidase or other drug injection in the affected area). Esthetic practitioners should be versed in injection anatomy, and the prevention, recognition, and management of filler complications in the perioral area.

Study of the functional relationships between the buccinator muscle and the connective tissue of the cheek in humans

BACKGROUND

The buccinator muscle derives from the mesenchyme of the second pharyngeal arch. In adults, it has a quadrilateral shape, occupying the deepest part of the cheek region. Its function is complex, being active during swallowing, chewing, and sucking. To our knowledge, there are no studies that have specifically analyzed the relationship of the buccinator muscle fibers and neighboring connective tissue of the cheek in humans, neither during development nor in adults. Such relationships are fundamental to understand its function. Thus, in this study the relations of the buccinator muscle with associated connective tissue were investigated.

METHODS

The buccinator muscle region was investigated bilaterally in 41 human specimens of 8-17 weeks of development. Moreover, four complete adult tissue blocks from human cadavers (including mucosa and skin) were obtained from the cheek region (between the anterior border of the masseter muscle and the nasolabial fold). All samples were processed with standard histological techniques. In addition, subsets of sections were stained with picrosirius red (PSR). Furthermore, immunoreactivity against type I and III collagen was also studied in adult tissues.

RESULTS

The buccinator muscle showed direct relationships with its connective tissue from 8 to 17 weeks of development. Collagen fibers were arranged in septa from the submucosa to the skin through the muscle. These septa were positive for type I collagen and presented elastic fibers. Fibrous septa that were positive for type III collagen were arranged from the lateral side of the muscle to the skin.

CONCLUSIONS

The intimate relationship between buccinator muscle fibers and cheek connective tissue may explain the complex functions of this muscle.

The 7-point Shape and The 9-point Shape: An Innovative Nonsurgical Approach to Improve the Facial Shape

Treatment with injectable fillers is considered to be intrinsically associated with the understanding of facial anatomy and appropriate techniques. However, a more comprehensive understanding of facial structure is critical to improving facial shape. This article presents two Nonsurgical approaches developed from the MD Codes system denominated "The 7-point Shape" and "The 9-point Shape." Both techniques were designed to help create a more feminine and masculine look, respectively. The aim is to provide foundation for the midface (cheek) and contour for the lower face (chin and jawline) and indirectly improve the facial signs that patients usually focus on when looking for aesthetic treatment (lines, folds, jowls, double chin, etc.). The MD Codes platform aims to deliver an alternative to surgery with injectables. The 7-point Shape and The 9-point Shape may provide visible results immediately after treatment.

The selection of hyaluronic acid when treating with the nasolabial fold: A meta-analysis

BACKGROUND

Hyaluronic acid (HA) gel is a widely used dermal filler for the correction of facial volume loss. The relationship between the characteristics of HA and clinical efficacy remains unclear. The aim of this systematic review and meta-analysis was to compare the efficacy and safety of monophasic and biphasic HA in the treatment of nasolabial folds (NLFs).

METHODS

Studies were identified by searching the electronic databases PubMed, Embase, and Web of Science from inception to May 2021. Randomized controlled trials (RCTs) were selected according to the inclusion criteria. Outcomes included the Wrinkle Severity Rating Scale (WSRS) score, Global Aesthetic Improvement Scale score, and incidence of adverse events.

RESULTS

A total of 1190 patients from 14 RCTs were included in the meta-analysis. The mean WSRS score improvement in the biphasic HA group was much lower than that in the monophasic HA group (MD = 0.18, 95% CI: 0.16-0.20, p < 0.00001). The subject satisfaction percentage was significantly higher for monophasic than biphasic HA (RR = 1.95, 95% CI: 1.09-3.48, p = 0.02). There was no significant difference in the adverse event rate between the monophasic and biphasic HA groups (RR = 0.96, 95% CI: 0.75-1.24, p = 0.77).

CONCLUSIONS

Regardless of whether improvement in NLFs or patient satisfaction is considered, monophasic HA is better than biphasic HA. Regarding the adverse event rate, there is no difference between monophasic and biphasic HA.

Micro-computed tomography with contrast enhancement: An excellent technique for soft tissue examination in humans

Manual dissection and histologic examination are commonly used to investigate human structures, but there are limitations in the damage caused to delicate structures or the provision of limited information. Micro-computed tomography (microCT) enables a three-dimensional volume-rendered observation of the sample without destruction and deformation, but it can only visualize hard tissues in general. Therefore, contrast-enhancing agents are needed to help in visualizing soft tissue. This study aimed to introduce microCT with phosphotungstic acid preparation (PTA-microCT) by applying the method to different types of human tissue. Specimens from human cadavers were used to examine the orbicularis retaining ligament (ORL), nasolabial fold (NLF), and the calcaneal tunnel of the sole. Using PTA-microCT, relevant information of human structures was identified. In the ORL study, tiny and delicate ligamentous fibers were visualized in detail with multidirectional continuity. In the NLF study, complex structural formation consisting of various types of soft tissue were investigated comprehensively. In the calcaneal tunnel study, the space surrounded by diverse features and its inner vulnerable structures were examined without damage. Consequently, we successfully applied the PTA-microCT technique to the analysis of specific human soft tissue structures that are challenging to analyze by conventional methods.

Immunohistochemical evidence of striated muscle cells within midfacial superficial musculoaponeurotic system

INTRODUCTION

The superficial musculoaponeurotic system (SMAS) is a controversial functional fibro-adipose layer that connects the mimic muscles to the skin and is involved in a variety of facial mimic expressions. The presence of muscle fibers within SMAS fibrous septa is hypothetical. The present study analyzed SMAS fibrous septa composition for the existence of striated muscle cells.

METHODS

Histological serial sections of the sample borders (n=107) of 19 in sano-resected and diagnosed cutaneous tumors of the midfacial region were investigated. Immunohistochemical (actin and myosin) and hematoxylin and eosin staining were performed to detect striated muscle cells in SMAS fibrous septa.

RESULTS

A fibro-neuro-musculo-vascular functional unit within SMAS fibrous septa was demonstrated. SMAS striated muscle cells were morphologically independent from preparotideal and periorbital mimic muscles. Intraseptal blood vessels draining the superficial and deep SMAS vascular system were described.

CONCLUSIONS

Striated muscle cells were demonstrated within SMAS fibrous septa. Nerve cells and vascular tissue together with the SMAS fibro-muscular meshwork demonstrated an autonomous operating functional unit that hypothetical modulated individual mimic expression contributing to the diversity of mimic expression. The SMAS develops with mimic muscle contractions as a synergetic effect during facial crease and fold formation processes.

Morphological study of human facial fascia and subcutaneous tissue structure by region through SEM observation

Fascia of the facial area is contiguous between fat tissues of the subcutaneous and connective tissue layers and does not envelope the muscle surface like other parts of the human body. This structure is called the superficial musculoaponeurotic system (SMAS), which is accepted as an international anatomical terminology. This special structure is commonly used to pull facial muscles during plastic surgeries such as a face lift. Most reports regarding the facial subcutaneous tissue structure including SMAS are in the field of plastic surgery, and only a few studies from a morphological perspective has been reported. Since the facial fascia does not envelope the muscular surface layer which is different from the deep fascia found on the general skeletal muscle surface, a clear definition of this structure has not been established yet. The purpose of this study was to clearly identify the basic morphological structure of the subcutaneous tissue layer containing the SMAS three-dimensionally through a scanning electron microscope using dissected specimen rather than living subjects. Moreover, this study explores structural differences among seven aging facial areas; thereby further clarifying the properties of the structure and add clinical significance and considerations.

Upper Lip Horizontal Line: Characteristics of a Dynamic Facial Line

Background: Upper lip appearance received major attention with the introduction of diverse treatment modalities, including lip augmentation, rhinoplasty surgery, and dental treatment designed to support the upper lip. Our objectives were to define the prevalence and characteristics of the upper lip horizontal line (ULHL), which is a dynamic line appearing during a smile, in relation to gender, malocclusions, aging, and facial morphology. Methods: First, the prevalence and gender distribution of ULHL was examined from standardized en-face imaging at full smile of 643 randomly selected patients. Second, cephalometric and dental cast model analyses were made for 97 consecutive patients divided into three age groups. Results: ULHL appears in 13.8% of the population examined, and prevailed significantly more in females (78%). The prevalence of ULHL was not related to age nor to malocclusion. Patients presenting ULHL showed shorter upper lip and deeper lip sulcus. The skeletal pattern showed longer mid-face, shorter lower facial height and greater prevalence of a gummy smile. Conclusions: Female patients with short upper lip, concavity of the upper lip, and gummy smile are more likely to exhibit ULHL. The ULHL is not age-related and can be identified in children and young adults. Therefore, it should be considered when selecting diverse treatment modalities involving the upper lip.

Funktionelle Morphologie der Gesichtshaut

Die Gesichtshaut stellt eine Besonderheit dar, da sie neben den allgemeinen Funktionen der Haut auch der Informationsvermittlung durch die Mimik dient. Sie gliedert sich in 3 Schichten: Epidermis, Dermis und Subkutis. Letztere ist im Gesicht als superfizielles muskuloaponeurotisches System (SMAS) differenziert. Dieses SMAS verbindet die mimische Muskulatur mit der Haut und induziert als eigenständig agierende funktionelle Einheit die differenzierte Mimik. Die regionale unterschiedliche dreidimensionale Architektur des SMAS trägt zur spezifischen Morphogenese der Gesichts- und Halsfalten bei. Bei chirurgischen Eingriffen im Gesichtsbereich sind die Besonderheiten des SMAS in den verschiedenen Regionen des Gesichts zu beachten.

Facial fold and crease development: A new morphological approach and classification

Facial folds and creases are established descriptive anatomical terms for structures of which the morphological characteristics and origins are not clearly defined. The aim of this study was to perform a morphological investigation of the nasolabial fold (NLF), mandibular fold (MF), deep transverse forehead (DTFC), infraorbital fold (IOF) and upper eyelid fold (UEF), correlating their phenotypes to differences in the superficial musculoaponeurotic system (SMAS), noting morphological differences and similarities. Full-graft tissue blocks of skin, subcutaneous tissue, and mimic muscles collected postmortem were studied histologically. Serial histological sections were stained with Azan. Location- and composition-specific morphological differences were determined. Histological serial section digitalization and three-dimensional reconstruction of the tissue blocks were performed. Three different types of SMAS architecture were identified. Type I SMAS consisted of parallel-aligned fibrous septa connecting the mimic muscles to the skin that covered the cheek, infraorbital and supraorbital, and forehead areas. Type II SMAS morphology appeared as a condensed Type I SMAS architecture with stronger fibrous septa and smaller fatty tissue compartments covering the lower and upper lip areas. Type III SMAS consisted of loose connective tissue covering the lower and upper eyelid regions. NLF, MF, IOF, and UEF are habitual primary folds induced by morphological changes in the underlying SMAS architecture. The secondary, accidental creases (DTFC) are cutaneous depressions derived from interacting dermal-skeletal-muscular changes without SMAS structure changes. The upper and lower eyelid wrinkles were tertiary, age-related undulating skin redundancy formations. Clin. Anat. 32:573-584, 2019. © 2019 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

Histological, SEM and three-dimensional analysis of the midfacial SMAS - New morphological insights

INTRODUCTION

The superficial musculoaponeurotic system (SMAS) of the midface has a complex morphological architecture, and a multitude of controversial opinions exist regarding its in vitro appearance and clinical relevance. The aim of this study was to investigate the three-dimensional architecture of the midfacial SMAS.

METHOD

Histological and SEM analyses were performed on tissue blocks of the skin, subcutaneous tissue and mimic musculature of the midfacial region between the anterior parotid gland pole and lateral to the nasolabial fold and tissue blocks of the skin, subcutaneous tissue and parotid fascia. Blocks were collected postmortem from six formalin-fixed donor bodies. Serial histological sections were made, stained with Azan and digitized. Three-dimensional reconstructions and visualization of the tissue blocks were performed using AutoCAD.

RESULTS

Two different SMAS architectures were found in the midfacial region: parotideal (type IV) and preparotideal (type I) SMAS. Type I SMAS showed three-dimensional interconnecting fibrous chambers embracing fat tissue lobules that cushioned the space between the skin and mimic musculature. Fibrous septa divided the mimic musculature surrounding the muscular bundles. Beneath the mimic muscular level, SMAS septa were oriented parallel to the muscular plane. Above the mimic muscular plane, SMAS septa were oriented perpendicularly, inserted into the skin. Type IV SMAS showed a parallel alignment of the fibrous septa to the skin level, anchoring the skin to the parotid fascia, presenting lymphatic nodes in the fat tissue compartments. The fat cells of the SMAS were enveloped in a fibrotic membrane at the border of the fibro-muscular septa. The SMAS blood supply comprised two subcutaneously epimuscularly spreading anastomosing vascular systems.

CONCLUSIONS

Midfacial SMAS represents a functional unit with physical and immunological tasks appearing in two different morphological architecture types. A well-defined nomenclature is needed to prevent controversy.

Three-dimensional reconstruction of the suborbicularis oculi fat and the infraorbital soft tissue

The aim of this study was to reveal the histomorphological connections among the suborbicularis oculi fat (SOOF), the orbicularis oculi muscle (OOM), the superficial musculoaponeurotic system (SMAS), the infraorbital fat and the skin.

Full graft tissue blocks of the infraorbital region with the skin, SMAS, OOM and SOOF were collected post mortem from one female and two male formalin-fixed body donors. Serial histological sections were made, stained and digitized. Digitalization and three-dimensional (3D) reconstruction of the histological meshwork were performed.

SOOF was revealed as a fibro-adipose tissue underlying the OOM, which was strictly separated from the intraorbital fat pad by the orbital septum. SOOF, OOM and SMAS were connected by fibrous septa derived from the SOOF, traversing the OOM with division into multiple muscular bundles, continuing above the muscular plane by forming the SMAS and ending with skin insertion. In the infraorbital region, two different types of SMAS bordering the infraorbital fold have been recognized. Muscle cells have been demonstrated in the SMAS fibrous septa of both SMAS types.

Together with the OOM, the SMAS and the skin, SOOF forms an anatomical functional unit. Muscular contraction of the OOM could be transferred by the SMAS to the skin level, producing periorbital mimic expression. The 3D reconstruction facilitates the comprehension of the morphological structure, its connections and space correlations in the infraorbital area. The morphological and topographical peculiarities of the infraorbital structures make it possible to conclude that surgical interventions in this area need to be elaborated and individualized.