Clinical Implication of the Regional Thickness of the Lower Facial Skin, Superficial Fat, and Superficial Musculoaponeurotic System on High-Intensity Focused Ultrasound Treatment

Knowledge of the topographic thickness of the skin and soft tissues is necessary when performing a high-intensity focused ultrasound (HIFU) procedure. Thermal tissue injury to the superficial musculoaponeurotic system (SMAS) or deeper can injure the facial nerve and its branches.To demonstrate the topographic thickness of the lower facial skin, superficial fat, and SMAS.The ultrasound data of 200 healthy patients who underwent lower facial rejuvenation were retrospectively reviewed.The mean age was 41.1 ± 13.7 years (range, 19-76 years). The jowl had thinner skin, thicker superficial fat, and deeper superficial and deep margins of the SMAS than the preauricle or lower cheek. The thickness of the superficial fat decreased with age, especially on the preauricle, lower cheek, and jowl. Women had thicker superficial fat than men on the preauricle and lower cheek. The superficial and deep margins of the SMAS were located more superficially in old and male patients with a slim facial figure than in young and female patients with a chubby facial figure.The present findings provide anatomical information regarding the superficial fat and SMAS, which is useful in determining the focal penetration depth of HIFU treatment for lower face rejuvenation.