ANATOMY OF THE FACE
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.
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
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
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
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).