The Superficial Musculo-Aponeurotic System (SMAS), as originally described by Tessier and his fellows Mitz and Peyronie, has been the subject of countless surgical and anatomical studies.1 Prior to our anatomical and surgical research, the SMAS was thought to invest the mimetic muscles of the mid-face and overlay the facial nerve. The authors defined a fascial plane in the infraorbital region described it as above the previously unrecognized “deep fascia”, dubbing it “Chiara’s fascia.” 2,3
The authors have correlated anatomical work to explain the new concepts linked to the description of this fascia with over 100 fresh cadaver heads performed in Paris – Laboratoire d’Anatomie, Ecole de chirurgie du Fer à Moulin and over 900 fresh facelift dissections over 10 years in Santa Barbara- California.
Our studies have demonstrated that, in the infra-orbital region, there is, similar to other areas of the body, a deep fascial layer. This deep fascial layer is continuous with the deep temporal fascia, particularly the superficial layer of deep temporal fascia.
It extends from the temporal area to the infra-orbital region, after inserting over the zygomatic bone, continues into the mid-face, investing the zygomaticus major and minor, the levator labii superioris, and the levator anguli oris muscles. It divides the fat layers deep to the orbicularis oculi muscle into the sub-orbicularis oculi fat (SOOF) and supra-periosteal fat (SPF). The branches of the facial nerves and the zygomatico-facial nerve lie under this thin deep fascial layer, which protects them. This layer plays also an important role in forming the true and false ligaments of the midface.
These new surgical and anatomical concepts implies a safer and better performed dissection during facelift procedures preserving the facial nerve.
References:
1. Mitz V, Peyronie M. The superficial musculo-aponeurotic system (SMAS) in the parotid and cheek area. Plast Reconstr Surg. 1976 Jul;58(1):80-8.
2. Andretto Amodeo C, Casasco A, Icaro Cornaglia A, Kang R, Keller GS. The suborbicularis oculi fat (SOOF) and the fascial planes: has everything already been explained? JAMA Facial Plast Surg. 2014 Jan-Feb;16(1):36-41.
3. Andretto Amodeo C, Eggerstedt M, Kim IA, Nabili V, Keller GS. The Deep Fascia of the Infraorbital Region, Deep Plane, and Suprafibromuscular Facelift: New Anatomy for Safer Facelifting. Facial Plast Surg. 2022 Dec;38(6):623-629.