The characteristics of the superficial musculoaponeurotic system (SMAS), including the morphology of each part and the connection between tissues, remain controversial. The purpose of this study is to clarify the anatomy of the SMAS using our new dissection method. In this study, six hemi-sides of heads from formalin-preserved cadavers were used. Three were used for creating a horizontal section and three were used for creating the section along the axial line perpendicular to the surface of the skin, resulting in a gradual change from the coronal section at the lateral to the sagittal section at the median. The resected head was cut into slices with widths of 7 mm. The stretched tissue dissection method was performed by fixing a tissue slice to a board and pulling the skin outward to stretch the soft tissue. Blunt dissection was then performed under a microscope. The SMAS comprises three layers: superficial, intermediate, and deep. The superficial layer is a thin membrane directly connecting to the septa in the subcutaneous fat. The deep layer is the connective tissue in contact with the sub-SMAS structure. The layer surrounded by the superficial and deep layer of the SMAS is the intermediate layer, containing connective tissue, adipose tissue, and facial muscles. The detailed findings of the SMAS obtained using this method resolve theoretical discrepancies and provide important insight for the field of facial surgery.
Background: In recent years, structures including the superficial musculoaponeurotic system and retaining ligaments that support the facial soft tissue have been clarified. However, these structures are very difficult to observe in their entirety by the standard gross anatomical procedure (ie, dissection from superficial to deep layers). Furthermore, accurate descriptions of these structures are rare in both anatomical and plastic surgery textbooks. The aim of this study was to clarify the facial fibrous structures in a gross anatomical view. Methods: The authors’ novel method used soft facial tissue and bone. The tissue was fixed in gelatin and sectioned at a thickness of 5 to 10 mm. Each section was placed on a wooden board; the bone was then pinned, and the skin was pulled outward with sutures to hyperextend the soft tissue. Subsequently, the loose connective tissue was torn and fat tissue was removed under a surgical microscope. After the removal of fat tissue, the fibrous facial structures (eg, the superficial musculoaponeurotic system and retaining ligaments) could be observed clearly. Results: The thickness of the sections allowed three-dimensional observation, such that a structure located deep within a section could be clearly observed. The expansion of soft tissue facilitated observation of the facial layer and fibrous structures, and the locations of nerves and vessels. Therefore, the facial layer structure was readily discerned. Conclusion: This method is likely to be very useful in the field of plastic surgery because it enabled intuitive identification of facial layers and their characteristics. Clinical Relevance Statement: The dissection method developed by the authors reveals the connected morphology of each tissue of the face, thus providing basic data for analyzing soft tissue changes due to aging and gravity. This will be useful for the development of anti-aging medicine.
Background Acute inflammatory reactions (AIRs) are a rare complication following esthetic treatment with hyaluronic acid (HA) and/or human collagen fillers. However, a substantial increase in the frequency of AIRs was observed in the first author's clinic since May 2020. Aims To report AIR cases, we experienced and discuss potential underlying mechanisms. Methods This was a retrospective review of patients representing AIR symptoms following filler injection with HA or human collagen in our clinic. Results Although only one case of an AIR with an incidence rate of 0.01% was recorded following filler treatment between September 2008 and April 2020 in our clinic, we observed 14 AIR cases without anaphylaxis, with an incidence rate of 1.18% between May 2020 and June 2021, in line with the spreading of the new coronavirus pandemic. All cases were females aged 40–57 years, and the time of onset was within hours after filler injection. Three patients had been treated with HA fillers only, 2 with HA plus human collagen, and 9 with human collagen only. Most patients had been treated with these products in the past. Nine patients were treated with oral prednisolone. In all cases, symptoms resolved entirely within a week without sequelae. Conclusions The marked increase in AIRs coincided with the COVID‐19 pandemic. Possible explanations include immune system alterations caused by extensive changes in domestic and personal hygiene, prolonged and elevated stress levels, and subclinical COVID‐19 infection. Further studies may be warranted.
The purpose of this study was to clarify the subcutaneous structures involved in the morphology of the gluteal region for clinical application. Thirty‐seven formalin‐fixed cadavers and one soft‐fixed cadaver were used in this study. Gluteal tissue was removed from five formalin‐fixed cadavers. A horizontal section and sections parallel to the long axis of the body were made from the excised tissue, and the subcutaneous fat was removed to observe the fibrous structure within the subcutaneous fat. Two formalin‐fixed cadavers and one soft‐fixed cadaver were used to perform conventional gross anatomical dissection and histological examination. On 30 formalin‐fixed cadavers, the thickness of the subcutaneous fat was measured in various areas of the buttocks. The thickness of subcutaneous fat was thicker in the center of the buttocks and thinner on the lateral buttocks. Superficial fascia (SF) was found only in the upper buttock, being indistinct in the lower buttock. In the sacral and coccygeal areas, the dermis was tightly adhered to the bone as a single mass. Fibers arose from around the iliac crest to the SF. On the medial side of the gluteal fold, a strong fiber arose from the sciatic tubercle and inserted into the gluteus maximus and dermis. By identifying the characteristic subcutaneous structures of the gluteal region, we were able to identify the anatomical structures that shape the three‐dimensional morphology of the buttocks. These findings may be useful in surgical treatments such as improving the buttock shape.
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