What is the SMAS and why it governs a facelift

If you have read about facelifts, you will have come across these four letters in the first line of almost everything. SMAS appears on clinic websites, in the names of techniques and in consultation conversations, almost always without anyone stopping to explain what it is.

It is worth understanding, because it is the layer that separates surgery that repositions from surgery that only stretches, and that is what decides whether a result looks natural or not.

What SMAS stands for

It is the abbreviation of Superficial Musculo-Aponeurotic System. It is a sheet of fibrous and muscular tissue that runs across the face beneath the subcutaneous fat and above the deep structures, and that wraps and connects the muscles of facial expression.

The simplest way to picture it is to think of the face as a layered structure. From the outside in: the skin, the subcutaneous fat, the SMAS, a gliding plane, and below that the deep muscles, the facial nerve and the bone.

The SMAS is continuous. Downwards it carries on into the neck and becomes the platysma, the muscle responsible for neck bands. Upwards it continues with the layer that covers the temple and the forehead. That continuity explains why surgery that works this layer well can change the cheek, the jawline and the neck at the same time.

What it does

It has three functions that matter for understanding facial ageing:

• It transmits movement. It spreads the contraction of the expression muscles to the skin, which is what lets the face move as a whole rather than in pieces.
• It supports. It is the scaffolding that keeps the facial fat in place, divided into compartments.
• It protects. The branches of the facial nerve run beneath it. That relationship is what makes the SMAS the key anatomical landmark in facial surgery: knowing which plane you are working in means knowing how far away the nerve is.

What happens to it with age

The SMAS loses elasticity and slackens. As it does, it stops holding the fat in position, and the fat descends and gathers where it was not before.

That is where the signs people name without knowing they share a common origin come from: the sagging cheek, the loss of a clean jawline, the appearance of jowls, the fold that runs down from the corner of the mouth and the vertical bands on the neck. They are not five problems, they are the same layer giving way in five places.

It is worth separating this from what happens to the skin, which ages on its own and for other reasons: sun, smoking, loss of collagen. That is why some people have excellent skin and a sagging facial outline, and the other way round.

Why this changes the surgery

This is the heart of the matter. If the problem is that the supporting layer has given way, pulling on the skin does not correct it: the skin is not what provides the support.

A facelift that only tightens the skin achieves two unwanted things. First, the effect does not last long, because the skin soon gives way again with nothing underneath to hold it. Second, and more visibly, the pull shows: stretched skin drags the corners of the mouth and the features backwards rather than upwards, and produces that pulled look everyone recognises from a distance and nobody asks for.

A facelift that works the SMAS repositions the supporting layer and returns the fat to its compartment. The skin then redistributes over a structure that is already in place, and it is closed without tension. That is the technical reason why some results look natural and others do not, and it has nothing to do with removing more or less skin.

Ways of treating it

There is no single way of working on this layer, and the commercial names cause a fair amount of confusion. In general terms:

SMAS plication

The layer is folded over on itself and secured with stitches, without cutting it. It is the most conservative approach and the one with the lowest risk to the nerve, with a more limited lifting effect.

SMASectomy

A strip of tissue is removed and the edges are sutured, which creates tension in the desired direction. It allows better control of the direction of pull.

SMAS elevation and the deep plane

Instead of working the layer from the outside, the surgeon goes underneath it and releases it from its attachments to the bone, the retaining ligaments. That makes it possible to move the SMAS, fat and skin together as a single unit. It is the basis of the deep plane technique, which works in the gliding plane that lies just beneath.

Which approach suits each case depends on the anatomy, the degree of sagging, the thickness of the skin and which area weighs most. It is not a scale from less to more: they are different tools for different situations.

What the SMAS does not solve

Working this layer well does not fix everything that ages in a face:

• It does not improve skin quality, pigmentation or fine lines.
• It does not restore lost bone volume, which is reabsorbed over the years and mainly affects the cheekbone and the rim of the eye socket.
• It does not correct the eyelids, which have their own anatomy and their own surgery.
• It does not stop the process. The repositioned SMAS keeps ageing from the very next day.

That is why a serious assessment does not talk about a single technique, it talks about which plane is most affected in that particular face.

Frequently asked questions

What does SMAS stand for?

Superficial Musculo-Aponeurotic System, in Spanish sistema musculoaponeurótico superficial. It is the sheet of fibrous and muscular tissue that lies between the subcutaneous fat and the deep structures of the face, and that wraps the muscles of expression.

Is the SMAS the same as the platysma?

They are the same structure in different areas. The SMAS runs across the face and continues down the neck, where it becomes the platysma. That continuity is why the face and the neck are treated in the same operation, and the neck muscle has its own page.

Do all facelifts work on the SMAS?

No. Some approaches only act on the skin, and those are the ones that give short-lived results with a pulled look. A technique having SMAS in its name does not tell you which plane is actually being worked on either: that is a fair question to ask in consultation.

Can the SMAS be tightened without surgery?

Not with the treatments available today. Radiofrequency and focused ultrasound act on the skin and the subcutaneous tissue, with a limited and temporary tightening effect. They do not reposition the layer or release its attachments. What each option can achieve is covered in the post on thread lifts and radiofrequency.

Why is the SMAS said to protect the facial nerve?

Because the branches of the nerve run beneath that layer. Knowing which plane you are working in is the same as knowing how far away the nerve is, and that is why it is the key anatomical landmark in this surgery.

How long does a facelift that works the SMAS last?

Repositioning the supporting layer gives a more stable result than tightening only the skin, but it does not stop ageing afterwards. The tissues keep giving way from the very next day, at a rate that depends on genetics, skin quality and each person's habits.

What this surgery corrects and what it does not is explained in cervicofacial facelift: what it is, and the detail of the technique on the facelift page.

A medical consultation, in person or online, is essential before any treatment is decided, surgical or not: the same diagnosis can have several treatment options. Dr. Mauricio Verbauvede, registered with the Madrid Medical Association (ICOMEM), no. 281509742.