Background The superficial musucloaponeurotic system (SMAS) is an important structure to understand for face-lift surgeries. However, the detailed distribution and imaging findings of the SMAS have not been established yet. Objectives The aim of this study is to establish the accurate distribution and CT imaging findings of the SMAS based on cadaveric studies. Methods This study was designed in a three-step procedure. First: Seven cadaver faces were used to understand the distribution and histology of the SMAS. Second: The SMAS’s findings from the cadaveric studies were compared to the CT images. Third: CT images were enrolled for the SMAS interpretation. Results In seven cadaveric studies, the SMAS was observed as a subcutaneous fibro-membranous structure extending from the galea aponeurotica to the platysma muscle, and laterally connected to the parotid fascia. On the medial side, it also connects with major and minor zygomatic muscles. The SMAS consisted of muscular fibers, collagen fibers and elastic fibers, histologically. Eighteen CT images (all females; age range, 21-82 years) showed the thin linear structures corresponding to the fibro-membranous structures in the cadaveric studies. CT density of the SMAS was similar with the muscle’s, and the SMAS was able to be recognized in all 18 subjects. Conclusions The SMAS is a definite anatomical structure that can be demonstrated as a thin membranous structure on CT. This clinical application could be applicable to the development the cosmetic surgical procedures.

Background Age-related changes in the periocular areas are mainly caused by anatomical changes of the bony orbit and orbicularis oculi muscle (OOM). To achieve effective rejuvenation, it is necessary to understand these anatomical changes according to age. Objectives We analyzed the configuration of the bony orbit and OOM using computed tomography (CT) and evaluated the effects of aging on these structures. Methods A total of 220 orbits and OOMs of 110 Japanese participants (55 males, 55 females) aged 20-87 years were enrolled. The long diameter of the orbits, orbital ellipticity, OOM thickness, and OOM attachment to the inferior orbital rim were analyzed. These variables were statistically evaluated for their relationship with age. Results The long diameter of the orbit was significantly longer in those over than in those under 60 years, with a moderate and significant positive correlation between orbital ellipticity and age. OOM thickness and age showed a strong negative correlation. The degree of OOM attachment to the inferior orbital rim decreased significantly with age. Conclusions This study showed that age-related changes of the bony orbit in Japanese individuals tended to be the same as those in Caucasians, but there were differences in degree of changes observed. As a new finding in the Japanese population, the OOM not only thins with aging, but also gradually loosens from the facial bone. In the elderly, only the nasal side of the OOM was attached to the bone. In clinical application, this could contribute to the development of cosmetic surgeries.

Background The superficial musculoaponeurotic system (SMAS) is an anatomical structure involved in facial aging. Objectives This study focused on SMAS thickness, and aimed to establish age-related changes in SMAS thickness. Methods A total of 100 adult Japanese female participants (aged 20–79 years) were enrolled in the study. The participants were divided into 3 age groups: Y, M, and E, comprising 20 to 39, 40 to 59, and 60 to 79 years, respectively. Anatomical structures were used as landmarks to standardize the SMAS analysis sites. The SMAS in a fixed analysis area (FAA) was quantified using multi-detector computed tomography (MDCT), and the relationship between SMAS thickness and age, as well as body mass index (BMI), was analyzed. Results In 96 participants (four were excluded due to imaging artifacts), a moderate yet significant negative correlation was found between the average (A)-SMAS thickness within the FAA and age. The A-SMAS thickness in groups M and E was significantly lower than that of group Y, and the mean value of group E was significantly lower than that of group M. SMAS thickness was greater in the young population. The SMAS gradually became thinner with aging. A statistically significant correlation was not found between SMAS thickness and BMI. Conclusions Using MDCT technology, age-related changes in SMAS were successfully analyzed. This highly objective analysis method corroborated the aesthetic surgical knowledge of the SMAS features related to facial aging. In clinical applications, our findings may help elucidate the mechanisms involved in facial aging.