ANATOMY OF THE FACE
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Layers of the Face
The face is arranged in a series of concentric layers6 from superficial to deep: the skin, superficial fascia (SMAS), and the deep fascia (Figure 1). The SMAS is well-defined laterally over the parotid but thins out as it extends medially.2 In the lower face it tends to be muscular, being the cranial extension of the neck platysma.2 In the mid- and upper face, however, it is usually aponeurotic and continues across the zygomatic arch as the superficial temporal (temporoparietal) fascia, which blends superiorly with the frontalis muscle, the galea aponeurotica, and the orbicularis oculi (Figure 2).2 Any dissection superficial to this plane is safe. Once the SMAS is breached, further sub-SMAS surgery requires 3-dimensional (3D) knowledge of the facial nerve branches, especially beyond the boundaries of the parotid gland (Figure 3).2,6-8,40-44 Understanding the nuances of this anatomy, superficial to deep, is perhaps more difficult for young surgeons to visualize and master.
Layers of the face from superficial to deep. The first layer is the skin and subcutaneous fat, followed by the superficial-musculo-aponeurotic-system. Caudally, the superficial-musculo-aponeurotic-system is continuous with the platysma and cephalically with the superficial temporal fascia (temporoparietal fascia) and galea. The third layer is the parotidomasseteric fascia, which is adherent to the parotid gland, and superiorly it blends with the deep temporal fascia.
Cadaver dissection of the left face. Skin and subcutaneous tissue have been reflected medially. The zygomatic arch and the lower mandibular border are delineated with blue dots. The superficial-musculo-aponeurotic-system (SMAS) is continuous across the zygomatic arch with the superficial temporal fascia and blends with the orbicularis oculi. It lies in the same plane as the galea aponeurotica and frontalis muscle. The superficial-musculo-aponeurotic-system is muscular in the lower face being continuous with the platysma in the neck. Further cephalad it is fibro-fatty. Age and gender of the cadaver are unknown.
Cadaver dissection of the left face. Skin and subcutaneous tissue have been reflected medially. The superficial-musculo-aponeurotic-system (SMAS) is incised and undermined for a short distance (red dots delineate the incised edges of the superficial-musculo-aponeurotic-system). A small superficial-musculo-aponeurotic-system flap is held in ovum forceps. Underneath the superficial-musculo-aponeurotic-system the parotid gland can be seen, and the frontal rami of the facial nerve travelling to cross the zygomatic arch can be appreciated (black arrows). The outline of the zygomatic arch and the lower mandibular border are marked in blue. A red arrow points to a sub-superficial-musculo-aponeurotic-system retaining filament with a blue background. A green arrow points to a fibrous filament retaining the skin to the lower mandibular border with a blue background. Age and gender of the cadaver are unknown.
Retaining Ligaments
These are fibrous attachments that fix the superficial layers of the face to the underlying deeper tissues. Not only do they restrict facial mobility in different anatomical regions and dictate the ways tissues yield in response to gravity, but when released they allow superior soft tissue mobilization distal to their attachments. They also constitute important surgical landmarks that herald the proximity of facial nerve branches.5-7,42,45,46 A clear distinction between ligaments, septa, and zones of adhesion has been emphasized by a number of authors.42-45 Nevertheless, these terms remain somewhat debatable.45-48
Ligaments are cylindrical structures retaining the face to bone and fascia. In the mid-face, the zygomatic ligaments5 along the arch and body of the zygoma, and in the lower face the mandibular ligaments5 at the lower portion of the anterior mandible, should ideally be released for optimum fascial mobility and thus superior tissue redraping (Figures 4 and 5) (Videos 1-2; a detailed description of each video is available online as Appendix A at www.aestheticsurgeryjournal.com).7,42 During the release of the major zygomatic ligaments, the zygomatic and buccal rami of the facial nerve will be found caudal to the zygomatic ligaments,7 as it is here that these nerve branches pass from deep fascia to an immediate sub-SMAS plane. Further sub-SMAS dissection in the mid-face separates a series of masseteric ligaments that hold the SMAS to the masseteric fascia and are closely related to zygomatic, buccal, and marginal mandibular rami.5,6 The location of the marginal mandibular nerve cranial to the mandibular ligaments should also be recognized (Figure 6).42
Cadaver dissection of the left face. Skin and subcutaneous tissue have been reflected medially. A red arrow points to the mandibular ligament, which can be appreciated as a cylindrical fibrous structure holding the skin of the lower face to the anterior mandible with a blue background. The outline of the lower border of the mandible is delineated with blue dots. Age and gender of the cadaver are unknown. SMAS, superficial-musculo-aponeurotic-system.
Cadaver dissection of the right face. Skin and subcutaneous tissue have been reflected medially. The outline of the zygomatic arch and lower mandibular border are denoted with blue dots. Black arrows point to the location of the zygomatic and mandibular ligaments. The red arrow points to the extension of the orbicularis retaining ligament from the orbicularis oculi to the skin. Age and gender of the cadaver are unknown. SMAS, superficial-musculo-aponeurotic-system.
Cadaver dissection of the right face. Skin and subcutaneous tissue have been reflected medially. The superficial-musculo-aponeurotic-system has been removed. The parotid gland has been removed and the facial nerve dissected. Red arrows point to the location of the zygomatic and mandibular ligaments. The black arrows point to the related zygomatic and marginal mandibular rami of the facial nerve. Note the relationship to the location of the ligaments. The buccal branch can be seen between these 2 rami (green arrows). Age and gender of the cadaver are unknown. DAO, depressor anguli oris. ZM, zygomaticus major muscle.
Septa constitute longitudinal lines of attachment of superficial tissues to underlying bone or fascia. In the upper face, the superior temporal septum represents the fusion of the deep temporal fascia to the periosteum at the cranial extent of the temporalis muscle. It extends inferiorly towards the superior lateral corner of the orbital rim terminating in the temporal ligamentous adhesion.45 Its release is important in brow and forehead elevation (Figure 7).45 The inferior temporal septum, on the other hand, stretches from the superior lateral corner of the orbital rim to the external auditory canal.45 The frontal branches of the facial nerve run inferomedial and parallel to it,45 approximately 1 cm cranial to the sentinel vein (Figure 7).49 Thus, in craniocaudal dissection during browlift, once the resistance of the inferior temporal septum is felt, further caudal progression should proceed with care, hugging the surface of the deep temporal fascia or proceeding a bit deeper to it to avoid any injury to the frontal rami.45
Cadaver dissection of the right face. The location of the superior temporal septum is marked with red dots. The location of the inferior temporal septum is marked with blue dots. The location of the temporal ligamentous adhesion is marked with a black star. Note the relation of the frontal rami of the facial nerve (black arrows) to the inferior temporal septum. Age and gender of the cadaver are unknown.
Zones of adhesions are areas of wide surface attachments between the superficial and deeper tissues. Both temporal septa (see above) in the upper face join at the superior lateral corner of the orbital rim to form a confluence of fibrous attachments described as the temporal ligamentous adhesion (Figure 7).45 This is a triangular condensation of fibrous tissue that has both temporal septa radiating out from it laterally and the supraorbital ligamentous adhesion extending from it medially (Figure 7).45 Comprehensive temporal, brow, and forehead elevation requires release of all these structures in addition to the brow depressors.45
Around the orbital rim, another fibrous structure holds the orbicularis oculi muscle and its overlying skin to bone and is known as the orbicularis retaining ligament (ORL) or orbitomalar ligament (Figures 5, 8, and 9).46,50 Release of this ligament is instrumental in blending the lid-cheek junction in lower blepharoplasty and achieving a mid-facelift through a subciliary approach.46,51,52 On the lateral orbital rim and the adjoining deep temporal fascia exists another triangular fibrous condensation that is continuous with the ORL and is termed the lateral orbital thickening.46 Knize considers it synonymous with the superficial head of the lateral canthal tendon.53 Alternatively, the superficial head of the canthal tendon fuses with this structure (the lateral orbital thickening) (Figure 10). Release of this condensation is necessary if lateral canthal lifting is to be obtained.46,53
Dissection of the left face viewed from profile. The skin of the lower eyelid and cheek is reflected medially. A filamentous extension of the orbicularis retaining ligament across the orbicularis oculi muscle to the skin can be seen highlighted with blue background and blue arrow. Note the zygomaticus major muscle (ZM) inferior to the orbicularis oculi. The zygomatic rami of the facial nerve traveling to the zygomaticus major muscle are dissected with blue background underneath (black arrows). Age and gender of the cadaver are unknown.
Dissection of the left orbit viewed from above. The bony edge of the inferior orbital rim is denoted with a blue dotted line. The deep aspect of the orbicularis oculi muscle is denoted with a red dotted line. Between the two lies the orbicularis retaining ligament (ORL). Note that medially, the orbicularis oculi muscle arises directly from the inferior orbital rim. Further lateral (approximately at the medial limbus), the orbicularis oculi muscle is attached indirectly to the inferior orbital rim by way of the orbicularis retaining ligament (orbitomalar ligament). Age and gender of the cadaver are unknown.
Dissection of the left orbit viewed from profile. The orbicularis oculi muscle has been separated from its attachments to the orbital rim by way of the orbicularis retaining ligament (orbitomalar ligament) and the lateral orbital thickening, which is marked with blue dots. Note that the lateral orbital thickening is triangular and continuous with the superficial head of the lateral canthal tendon (highlighted here with a blue background and red arrow). Inferior to it, the arcuate expansion (a condensation of the orbital septum that marks the junction between middle and lateral lower eyelid fat pockets) can be appreciated (the arcuate expansion is highlighted with a blue background and blue arrow). Age and gender of the cadaver are unknown.
Facial Nerve
All facial nerve branches are located deep to the SMAS-platysma-superficial temporal fascia plane (Figures 11 and 12) (Video 3; a detailed description of each video is available online as Appendix A at www.aestheticsurgeryjournal.com).
Dissection of the left face viewed from profile. The skin has been undermined in a subcutaneous plane and reflected medially. A superficial-musculo-aponeurotic-system (SMAS) flap has been elevated and is highlighted with blue dots. It is held up with clamps. Deep to the superficial-musculo-aponeurotic-system, the parotid gland has been exposed and the facial nerve branches have been dissected and are highlighted with blue background and black arrows. Age and gender of the cadaver are unknown. ZM, zygomaticus major; OO, orbicularis oculi.
Lateral facial view. Skin/subcutaneous fat reflected as the first layer and the superficial-musculo-aponeurotic-system/parotid-masseteric fascia as the second layer. The zygomatic (ZL) and mandibular (ML) ligaments are osteocutaneous, while the masseteric (MSL) ligaments are fasciocutaneous. When the zygomatic ligament is released, the zygomaticus major muscle (ZM) comes into view. At this point, the dissection should be transitioned from sub-superficial-musculo-aponeurotic-system to subcutaneous to avoid injuring the zygomatic nerve branches (green). The frontal nerve (yellow) hugs the periosteum of the zygomatic arch, deep to both the superficial-musculo-aponeurotic-system and parotid-masseteric fascia. Superior to the arch, it travels on top of the superficial layer of the deep temporal fascia. This relationship continues for 1.5 to 3.0 cm, then the nerve initiates its transition through the superficial temporal fascia to merge with the anterior branch of the superficial temporal artery as they approach the orbicularis oculi and frontalis muscles. The sentinel vein (SV) (located approximately 0.5 cm lateral to fronto-zygomatic suture) serves as a landmark, because the frontal branch is found 1.0 cm cephalad to it. The upper zygomatic ramus (green) passes between the main zygomatic (ZM) and upper masseteric (MSL) retaining ligaments, deep to the deep fascia and under the upper third of the zygomaticus major muscle (ZM). The lower zygomatic nerve (green) runs immediately inferior to the upper masseteric retaining ligaments in a more superficial plane than the upper zygomatic nerve branch (green), becoming visible just distal to the ligament. The buccal ramus (light blue) crosses through the lower masseteric ligaments. The marginal mandibular branch (orange) lies deep to the superficial-musculo-aponeurotic-system and platysma and is typically within 1.0 cm of the inferior mandibular border at the gonial angle. Posterior to facial vessels (FA, FV), it is most commonly found cranial to the mandibular border. Anterior to the vessels, they are always found superior to the mandibular border and 1.0 cm cranial to the mandibular ligament (ML). OO, orbicularid oculi.
