What it means for a patient
- The SMAS, a layer central to facial rejuvenation surgery, is not the same across the face.
- Outside the nasolabial fold it is looser and contains fat; inside the fold it is dense and mixed with muscle.
- The authors conclude surgery may need to differ by region. Ask how your surgeon handles the cheek and the area near the nasolabial fold.
- This is a cadaver study. It does not report surgical results.
Why this paper matters
It gave a region-by-region anatomical description of the SMAS and defined two structural types divided by the nasolabial fold. It supports region-specific surgical planning in facial rejuvenation.
Overview
The SMAS matters in facial rejuvenation, but a clear anatomical definition was lacking. The authors examined the SMAS in 18 cadavers with several visual and microscopic methods. They describe its structure in the forehead, parotid, cheekbone and below-eye regions, the nasolabial fold and the lower lip.
Findings
- 18 cadavers; macroscopic and microscopic techniques.
- Regions described: forehead, parotid, zygomatic, infraorbital, nasolabial fold, lower lip.
- The SMAS is one continuous, organized fibrous network connecting the facial muscles to the dermis.
- It is a three-dimensional scaffold of collagen fibers, elastic fibers and fat cells.
- Type 1 SMAS: outside (lateral to) the nasolabial fold; small fibrous septa enclose lobules of fat.
- Type 2 SMAS: inside (medial to) the nasolabial fold; a dense meshwork of collagen and muscle fibers.
- Different facial regions have specific structures.
- The authors conclude region-specific surgical approaches may be needed.
- The abstract gives no measurements.
Terms
- SMAS (superficial musculoaponeurotic system): the layer of muscle and fibrous tissue under the facial skin and fat.
- Nasolabial fold: the crease from the side of the nose to the corner of the mouth.
- Dermis: the deep layer of the skin.
- Septa: thin fibrous walls that divide tissue.
- Lobules: small rounded clusters, here of fat cells.
- Lateral / medial: toward the side of the face / toward the center.
- Macroscopic: visible to the naked eye.