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Facial Anatomy and Patient Evaluation

Timothy Osborn1,2 and Bradford M. Towne1

1 Department of Oral and Maxillofacial Surgery, Boston University, Henry M. Goldman School of Dental Medicine, Boston, MA, USA

2 Private Practice, C.M.F.‐Cranio‐Maxillofacial Surgery Associates, Boston and Somerville, MA, USA

1.1 Facial Anatomy

A comprehensive understanding of facial anatomy is a critical component of any facial esthetic procedure. A comprehensive review of facial anatomy is beyond the scope of this text, and this chapter will focus on regional anatomy as it pertains to minimally invasive rejuvenation. All aging changes manifest in different ways for each individual patient, thus an understanding of the changes pertinent for the individual must be understood when considering patient evaluation, planning, and treatment. Incorporating the anatomic effects of aging into the treatment plan will allow the treating provider to target the specific areas to reverse those signs of aging.

1.2 Anatomy of Facial Skin

The face has a layered structure that is best described from superficial to deep and includes the following: skin, subcutaneous fat, superficial musculo‐aponeurotic system (), deep fat, and deep fascia/periosteum. This architecture is preserved throughout the head and neck, with some areas further subdivided into fascial or fat compartments that will be addressed individually. These different compartments and layers may carry different names as they cross anatomic barriers making nomenclature difficult. A special section of the chapter will focus on these terms and clarify some key relationships.

The skin layer is divided into epidermis and dermis. The epidermis is the outermost layer and contains a continually renewing, keratinizing stratified squamous epithelium. The epidermis is anchored to the underlying dermis by hemidesmosomes and anchoring fibrils at the basement membrane. This dermal–epidermal junction provides the mechanical support to the epidermis and acts as the barrier to chemicals and other substances. Immediately below the epidermis, the dermis is the connective tissue composed of collagen, elastin, ground substance, the pilosebaceous unit, and accommodates a complex neurovascular network.

The dermis gives the skin it's pliability, elasticity, and tensile strength. The dermis is divided into two components: the papillary and reticular dermis. The papillary dermis is the thin layer adjacent to the epidermal papillae and sits atop the thicker reticular dermis. The papillary dermis consists of loose connective tissue, fibroblasts, immunocytes, and a capillary network. The reticular dermis is thicker and is composed of more densely organized collagen (which runs horizontally) and elastin fibers (which are loosely arranged). Variation in the thickness of the dermis is what accounts for regional variation in skin thickness. Ground substance is composed of glycoproteins, proteoglycans, and has a remarkable capacity to hold water.

These different subcutaneous arrangements vary in thickness between individuals of different ages, ethnicities, and lines of demarcation into distinct compartments [1]. There is heterogeneity of the facial fat in these compartments, with each compartment having different adipocyte morphology, and extracellular matrix [2]. These different compositions provide unique and specific mechanical and histiochemical properties yet there is little known about the characteristics of facial fat tissue and how that relates to facial aging.

1.3 Anatomy of the Superficial Fat Compartments

The subcutaneous fat is immediately deep to the dermis and is a discrete anatomic plane superficial to the SMAS. There is also a deeper layer of facial fat below the SMAS that will be discussed separately. The superficial layer of fat, or subcutaneous fat, can be further subdivided into two different arrangements with different microstructures. In the medial and lateral midface, temple, neck, forehead and periorbital areas, the adherence of the underlying structures to the skin is loose and easily separated from the skin [3]. The fat is classified as “structural” with a meshwork of fibrous septa enveloping lobules of fat cells that act as small pads with specific viscoelastic properties [4]. In the perioral, nasal, and eyebrow regions, there is a stronger linkage between the facial muscles, the collagenous meshwork surrounding the adipocytes, and the skin making any blunt dissection difficult. The collagenous and muscular fibers directly insert into the skin and connect the skin to the underlying muscles of facial expression. The fat is classified as “fibrous” with a meshwork of intermingled collagen and elastic fibers as well as muscle fibers.

The superficial fat compartments are partitioned as distinct anatomic compartments (nasolabial, jowl, cheek, forehead/temporal, and orbital [Figure 1.1]).

Figure 1.1 The superficial fat compartments of the face.

The nasolabial fat compartment lies medial to the cheek fat and while separate, overlaps the jowl fat. The orbicularis retaining ligament () represents the superior border and the lower border of the zygomaticus major and is adherent to this compartment. The jowl fat is adherent to the depressor anguli oris, bound medially by the lip depressors, and inferiorly is a membranous fusion with the platysma muscle in the area of the mandibular‐cutaneous ligament [5].

The cheek fat compartments contain three distinct compartments: the medial, middle, and lateral temporal cheek fat. The medial cheek fat is a small compartment lateral to the nasolabial fold (), bordered superiorly by the ORL and lateral orbital compartment, and the jowl fat lies inferior. The middle cheek fat is a larger compartment found anterior and superficial to the parotid gland. At its superior portion, the zygomaticus major is adherent at a confluence of septa corresponding to what has been described as the zygomatic ligament [6]. The lateral temporal‐cheek compartment is the most lateral compartment of the cheek fat. This fat lies immediately superficial to the parotid gland and connects the temporal fat to the cervical subcutaneous fat. There is an identifiable barrier medially called the lateral cheek septum which is consistent with the subcutaneous extension of the parotid‐cutaneous ligament.

The subcutaneous fat of the forehead is composed of three compartments. The central compartment is midline and abuts the nasal dorsum inferiorly, and the middle temporal fat laterally on either side. The middle temporal fat borders the orbicularis retaining ligament inferiorly and the superior temporal line laterally. Just lateral to this is the lateral–temporal cheek fat described earlier.

The orbital fat compartment consists of three compartments around the eye. The most superior compartment is bounded by the orbicularis retaining ligament as it courses around the superior orbit and sits immediately below the middle‐temporal fat. The inferior orbital fat lies immediately below the lower lid tarsus and is bound by the lower limb of the orbicularis retaining ligament. The lateral orbital fat lies below the inferior temporal septum, above the superior cheek septum just above the zygomaticus muscle. The lateral orbital fat compartment interdigitates superiorly and laterally with the lateral temporal cheek fat, and above the middle cheek fat.

1.4 Anatomy of the Facial Fasciae

Explanations of the facial and cervical fasciae are often complex, inconsistent, and very confusing. The concept of the SMAS was first introduced by Mitz and Peyronie, and while it is a discreet anatomic layer surgically, there are many who debate or seek to adequately define the layer [3, 7]. The SMAS is an organized and continuous fibrous network connecting the facial muscles with the dermis and consists of a three‐dimensional architecture in two different architectural models as described by Ghassemi. Type 1 is seen in the posterior part of the face and is a meshwork of fibrous septa that envelops lobules of fat cells. The interconnecting fibrous network is anchored to the periosteum or connected to the facial mimetic muscles and has dynamic properties. This morphology is found in the parotid, zygomatic, infraorbital regions, and just lateral to the nasolabial fold. Type 2 is a meshwork of collagen and elastic fibers intermingled with fat cells and muscle fibers that reach up to the dermis of the skin. This SMAS morphology is found in the upper and lower lip/perioroal region where the action of the facial mimetic muscles has a direct relationship to movements of the lip/perioral skin.

The subcutaneous zone of the face is divided into superficial and deep strata by the facial muscles and superficial fascia which serve as their origin. In the neck, the space of the superficial fascia is occupied by the platysma muscle and it's thin investing fascia. The SMAS and the temporoparietal fascia serve as the superficial facial fascia of the face (Figure 1.2).

Figure 1.2 Relationship of the facial fasciae in the lateral cheek/temporal region. The figure demonstrates the complex relationship between the fascia, facial nerve, and the often confusing nomenclature of the continuous layers.

The continuation of the...