Facelift anatomy

The layers of the face

• From the surface down: skin, fat, a fibrous layer that wraps the flat facial muscles, the muscles themselves, a deep fascia, and the plane that holds the facial nerve branches, the saliva duct and the buccal fat pad (PMID 1741467).
• In the cheek, the facial nerve branches lie beneath the deep fascia, so a lift that stays above it keeps them covered (PMID 1741467, PMID 25919245).
• The SMAS, short for superficial musculoaponeurotic system, was named by Mitz and Peyronie in 1976. Lifting under it was safe over the parotid gland in front of the ear and dangerous further forward (PMID 935283).
• The SMAS is not one continuous sheet. Cadaver studies found a distinct SMAS layer only over the parotid gland and where the flat facial muscles lie; between those muscles the fat under the skin meets the deeper fat directly, and the layer is thin or absent in the cheek (PMID 37039509, PMID 12560687). The "SMAS" a surgeon lifts is a flap of fat, facial muscle and thin fascia, of varying thickness (PMID 37039509, PMID 8248400).
• The space beneath that flap, floored by a thin deep fascia in the midface, is the "deep plane" (PMID 36261112, PMID 38354840).

Ligaments: what holds the face up

• Retaining ligaments are fibrous bands that run from the bone or deep fascia to the skin and hold the soft tissue in place (PMID 23855010). In 1989 Furnas described the main ones in the cheek and jaw, and showed that the zygomatic (cheekbone) and mandibular (jaw) ligaments must be released for the skin to move fully (PMID 2909050).
• Ligaments sit in constant places, between soft-tissue spaces and fat compartments, and nerve branches run close to them, which makes them landmarks for the surgeon (PMID 23855010).
• A zygomatic nerve branch passes between the main cheek ligaments and lies very shallow just below one of them, a danger area for deep lifts (PMID 23358020).

How the face ages

• Spaces stretch. Under the SMAS over the lower jaw muscle lies a space lined by membrane. Its lower border weakens with age, the space expands, and the jowl forms (PMID 18183455). A similar space lies over the cheekbone, with nerve branches in its walls rather than crossing it (PMID 12172155).
• Fat compartments deflate. The fat under the skin sits in separate compartments divided by thin walls, and each ages on its own (PMID 17519724, PMID 18454006). Loss of the deep inner cheek fat makes the cheek look as if it has dropped and deepens the fold beside the nose (PMID 18520902).
• Bone recedes. The upper jaw, parts of the eye socket rim and the jaw in front of the jowl lose bone with age (PMID 22580543).
• The jowl has more than one cause. In one comparison, adding fat to the hollow in front of the jowl corrected jowls better than releasing the jaw ligament (PMID 39001648).

What the surgeon changes

• Facelift techniques differ by the layer lifted (skin only, SMAS, deep plane or under the bone lining), by which ligaments are released and by the direction of pull (PMID 25919245, PMID 36261112).
• Knowing the fat compartments tells the surgeon how far to lift the skin and where the cheek has deflated and may need volume (PMID 31688754).

Where the nerves are, and how surgeons protect them

• Nerve injury after facelift has long been uncommon: under 1 in 100 in 1979 data, with recovery in more than 4 in 5 within six months (PMID 515227).
• The exact position of a nerve branch varies from person to person, but its relation to the layers is constant, so surgeons rely on the layers to stay safe (PMID 25919245). The depth of the lower face and neck branches is predictable in three dimensions (PMID 31881610).
• Danger areas are where a branch rises toward the surface: the forehead (temporal) branch over the temple, a lower cheek branch, an upper branch over the jaw muscle, and the lower lip branch where it crosses the facial artery (PMID 2315394).
• The forehead branch runs along a line from the ear to the outer brow, as Pitanguy described in 1966 (PMID 5926990, PMID 20335873). It lies on the underside of a fascia over the temple and is shallow over the cheekbone arch (PMID 2911626). Over the arch a separate deep fascia covers it, and lifts that divide the SMAS above the arch left it intact (PMID 20335873).
• In the neck, the cervical branch lies under the deep neck fascia after it leaves the parotid and can be injured by electrocautery during midline neck work (PMID 38748536).

The neck muscle

• The two halves of the platysma join under the chin in most people, lower in some, and not at all in others (PMID 7433553, PMID 34529598).
• A fascial attachment zone helps explain bands that sit just off the midline (PMID 34529598). On ultrasound, a band thickens when it contracts without gliding, while the rest of the muscle glides (PMID 37418617).
• The platysma's nerve supply is segmental: the lower lip branch supplies the face part and cervical branches the neck part (PMID 37186556).

Questions to ask a surgeon

• Which layer will you lift, and why for my face? (PMID 25919245)
• Which ligaments will you release? (PMID 2909050)
• Where are the nerve danger zones in my operation? (PMID 2315394)
• Is my jowl from sagging, lost fat or lost bone? (PMID 39001648)
• Do I need volume as well as a lift? (PMID 18520902)

Open questions

• What the SMAS is: cadaver work finds a distinct layer only in some regions (PMID 37039509, PMID 12560687), and its tissue varies by region and person (PMID 8248400). Deep plane terms were restated in 2024 (PMID 38354840).
• Jowl: ligament tethering (PMID 2909050) against fat loss corrected by fat grafting (PMID 39001648).
• Ligaments as separate structures or as fused walls between compartments (PMID 17519724, PMID 23855010).
• Neck bands: muscle activity (PMID 37418617) against fascial adhesion and laxity (PMID 34529598).
• Mitz reviewed fifty years of the SMAS and the facelift in 2026 (PMID 42481023).

Terms

• SMAS (superficial musculoaponeurotic system): the fibrous layer that wraps the flat facial muscles (PMID 1741467); named by Mitz and Peyronie (PMID 935283); a distinct layer only over the parotid and the flat muscles (PMID 37039509).
• Deep plane: the space under the SMAS whose floor is the deep fascia (PMID 36261112); Hamra introduced the term (PMID 38354840).
• Retaining ligament: a fibrous band from bone or deep fascia to skin (PMID 23855010).
• McGregor's patch: the zygomatic ligament area of the cheek (PMID 2909050).
• Premasseter space: the space under the SMAS over the lower jaw muscle (PMID 18183455).
• Prezygomatic space: the space over the cheekbone under the eye muscle (PMID 12172155).
• Fat compartment: a separate pocket of facial fat bounded by thin walls (PMID 17519724).
• Parotid-temporal fascia: the deep fascia that covers the forehead branch over the cheekbone arch (PMID 20335873).
• Danger zone: an area where a nerve branch rises close to a common plane of dissection (PMID 31881610).
• Pseudoptosis: apparent sagging caused by deep fat loss (PMID 18520902).

Papers