Air Subcision — Releasing the Tethering Beneath a Scar

Three-line summary

• Air subcision releases pressurised CO2 at the dermal-subcutaneous junction to cut the fibrotic bands tethering the floor of a scar downwards. The air is not filling the dent; what stays behind is the tethering the gas cut as it passed through.
• It shares its principle with needle subcision and differs in how the cutting is done. Gas spreads along the tissue plane, releasing broadly and evenly, and bruising and bleeding are reported to be comparatively less. The cutting force itself is more direct with a needle, so in practice the two are often used one after the other.
• It counts most in rolling scars where downward tethering dominates, and in shallow boxcars. A released plane can re-adhere, so it is not left to stand alone: an injection to support the space and a laser to work the surface are placed alongside it. Outcome and recovery vary between individuals.

Not a procedure that fills with air, but one that cuts what is stuck

The word subcision combines sub, meaning below, with incision, meaning a cut. It refers to cutting the tissue that is stuck beneath a scar without opening the surface of the skin. Adding air to the name means that the cutting is done by gas pressure rather than by the edge of a needle. Depending on the source it is also called air dissection or CO2 gas subcision.

Here is what it actually looks like. A fine needle is advanced to the junction of dermis and subcutis beneath the floor of the scar, and pressurised CO2 is released from that needle tip. The gas spreads along the path of least resistance and pushes apart the fibrotic bands strung across it. All that is left on the surface is the needle entry point; there is no incision.

The pocket of air this creates is easy to mistake for the aim of the procedure. It is closer to evidence that a release took place, and a space held briefly open so the cut surfaces do not meet again. The gas itself is absorbed and gone within a few hours to a day. What remains is not air but released tethering, and the change comes as new collagen fills that space.

It goes by several names

The same manoeuvre is described as air subcision, air dissection or CO2 gas subcision, all in circulation together. Because CO2 is injected into the skin, it is sometimes filed under carboxytherapy-style names as well. With that many names, people either mistake them for different procedures or, going the other way, lump different procedures together because the names match.

Rather than sorting by name, it is more accurate to look at the depth the gas is placed at and what it is meant to cut. Even with the same gas, spreading a thin layer near the surface and releasing at the dermal-subcutaneous junction to target tethering under a scar are done for different reasons. The air subcision discussed in acne scarring is the latter. Checking only the name of the procedure at consultation leaves this distinction invisible.

The device we use at ABLE Dermatology

At ABLE Dermatology this procedure is performed with TriFill (TriFill Pro). It enters the skin as a needle and releases gas from the needle tip, so tethering can be released exactly as in conventional needle subcision and gas release then added at the same site. On top of that, injecting a material directly into the released space is connected within the one device, which suits working through scars one at a time with some precision.

That said, the device does not determine the outcome. With the same device, the course depends on the depth the needle sits at, how wide a release is made, and what is placed there afterwards. Checking that plan tells you more than the name of the procedure does.

Why CO2 rather than another gas

CO2 is produced in the body already and cleared through the bloodstream, so it has a clear route out rather than staying in the tissue. Beyond that, injecting CO2 into the dermis is known to increase new vessel formation and release oxygen, which stimulates collagen synthesis. Separately from its role as a cutting tool, the shift towards better blood flow and oxygen supply is understood to support recovery.

Why a scar looks pressed in — pulled from below, not pushed from above

When a scar is depressed it is easy to assume something is missing at that spot. Sometimes the dermis has genuinely been damaged and lost volume, but in a fair number of scars there is also a floor held by the tissue beneath it and dragged downwards. As acne inflammation burrows into the dermis and heals, fibrotic bands form, and these bands keep pulling on the surface.

Watching how these bands form makes it easier to follow. When inflammation reaches deep into the dermis, fibrous tissue is laid down to fill the damaged area, and if that process does not run smoothly it hardens in a form that bridges between the surface and the tissue below. The acne has settled, but the connection left underneath keeps drawing the surface down. Over time this tissue tends to mature and stiffen.

This distinction matters because it changes the approach completely. Repeat surface treatment on a scar that is being pulled from below and, however much collagen is built up top, it cannot overcome that force and is drawn back in. That is why a plan of energy-based treatment alone, repeated over tethered skin, tends not to lift as much as hoped. What is stuck has to come apart before the next treatment has anywhere to land. Change the order and the same treatments over the same number of sessions give a different result.

How we check for tethering in clinic

• Stretching the skin sideways — if the floor of the scar comes up with it and flattens when the surrounding skin is pulled to either side, the tethering is on the weaker side; if it stays put rather than following, we read that as a sign it is being held from below.
• Changing the angle of the light — the shape of the shadow cast under oblique light distinguishes a scar with a standing border from one that slopes gently into a depression.
• Recording region by region — within one face, the outer cheek is often dominated by tethering while the inner cheek is dominated by dermal loss, so the judgement is made by region rather than scar by scar.

Sorting acne scars by shape into ice pick, rolling and boxcar is the first thing that comes up at consultation, but that classification alone does not settle the treatment. Two rolling scars call for different plans depending on whether the tethering is firm. Classification by shape is covered in detail in a separate column, so here we will concentrate on the axis of tethering.

Not every depressed scar is tethered

The opposite case is real too. A scar whose floor comes up readily when stretched, one with an angular standing border where the wall itself is the problem, and skin thinned overall by a reduction in dermal volume are not what a release procedure addresses. Repeating subcision-type work on these builds up bruising and recovery time without much change. Establishing whether there is anything there to cut comes before choosing a procedure.

What differs from needle subcision

These are not two separate families of treatment. The goal is the same and so is the layer they target. The one point where they part company is whether the tethering is cut by the edge of a needle or by the pressure of gas. That difference shapes the pattern of the release and the burden of recovery slightly differently.

Read the table alone and gas looks better on every line, but in practice it is not that simple. Gas spreads along planes of least resistance, which makes it well suited to releasing widely and evenly; conversely, the force needed to target one firmly hardened band and cut it precisely is more direct with a needle. Old, thickened tethering does not always come away with pressure alone.

So clinically, rather than choosing one of the two, the common sequence is cutting the firm parts with the needle first, then releasing gas from the same needle tip to widen the release into the surrounding area. A device such as TriFill, where both manoeuvres follow on within one needle, is well suited to carrying out that sequence as it stands. Rather than air subcision replacing needle subcision, it is more accurate to understand it as adding force from a different direction towards the same goal.

What "less painful" does and does not cover

Reports that the gas technique produces less bleeding and bruising come up consistently across sources. But this is a relative tendency at a comparable extent of release, not a claim that there is no burden. Advancing the needle to the floor of the scar is identical in both, and pressure or a dull ache is felt as gas pushes tissue apart. Numbing cream is used, with local anaesthetic added where needed, and how much people feel varies between individuals.

The wider the release, the more bruising and swelling follow. Cutting as widely as possible in one go may look like the efficient route, but weighing the recovery burden and the interval before the next session, dividing the area covered in a single session is easier to manage against a real schedule.

Spreading widely is both a strength and a limit

Gas moves towards lower pressure and less resistance. That is what lets it release evenly into areas the needle never touched, but put the other way it means the gas chooses its own route. It may skirt round a spot where the tethering is particularly firm and spread further into an area already loose.

What actually makes the difference in this procedure, then, is less the strength of the gas than the depth the needle is placed at. Too shallow and it spreads near the surface without reaching the floor it was meant to cut; too deep and it disperses in a layer that has nothing to do with the scar. The release you were aiming for happens only when the plane at the floor of the scar is found precisely and the gas is released there. This is the point at which the same device over the same time produces different results.

What the space left behind actually does

The heart of this procedure is not the moment of cutting but the process that follows it. The reported mechanism is generally set out in three stages.

• Releasing the tethering — pressurised CO2 mechanically cuts the fibrotic bands in the lower dermis, removing the force that was drawing the depressed scar downwards.
• Lifting the dermis — once the tethering is released, a space opens there, and the compressed dermis rises slightly, creating a footing from which it can flatten. That space becomes the site where new collagen is later laid down.
• Wound healing and collagen remodelling — the micro-stimulus created by the gas injection increases the release of growth factors such as TGF-β, PDGF and VEGF and activates fibroblasts, so collagen is laid down again across the released area.

In short, it is a chain running release of tethering → lifting of the dermis → activated healing → collagen reorganisation → improved blood flow. This is also why there is little change immediately after the procedure. The first step finishes on the treatment couch; the rest takes weeks to months.

The second step is worth dwelling on. Cut and then leave the area as it is, and the surfaces that have just come apart can heal back against each other. The space the gas creates briefly holds that contact off while the healing response gets going. The air itself is not pushing the scar up; it is closer to keeping a place open for the tissue that is about to be built. Seen this way, the question of re-adhesion discussed below and the question of what to place immediately after the release come from the same root.

What biopsy showed

In one study, 14 patients with acne scarring underwent three sessions of CO2 gas subcision and two sessions of fractional CO2 laser, with tissue compared by punch biopsy before and after in 10 of them. Clinical improvement was observed in all patients, and on biopsy increased dermal collagen, increased dermal thickness, and tidier arrangement of elastic fibres in the reticular dermis were reported.

That said, this study combined gas subcision with laser, so these results alone cannot separate which side the observed changes came from. It is a part people often miss when reading the evidence.

Studies that separated the two

• A split-face comparison (20 patients) — fractional CO2 laser was applied to the whole face over three sessions while CO2 gas subcision was added to the scars on one side only. Improvement in atrophic scars on the combined side was reported to be greater than on the laser-only side.
• Subcision alone versus combined — a study comparing a group receiving subcision alone with groups that added fractional CO2 laser or cross-linked hyaluronic acid found a higher proportion showing marked improvement in the combined groups. Side effects were largely swelling, pain and erythema, settling within about 3-10 days.
• Same-day versus sequential (34 patients) — one study compared performing fractional CO2 laser and subcision on the same day against separating them. Randomisation was not carried out, however, and the authors themselves state the possibility of selection bias as a limitation.

Two things need reading together here. One is that the tendency for improvement to be greater in combined designs repeats across several studies; the other is that these studies generally have small samples and, in some cases, no randomisation. The evidence so far is closer to material for judging direction than a stage at which individual outcomes can be promised as figures.

Where it counts, and where it does not

What this procedure targets is one element: tethering. So the larger the share tethering takes in a scar, the more there is to gain, and where that share is small the same procedure produces change that is hard to see. Set out by shape, it looks like this.

There are clear cases where it is not the answer

• Red marks (post-inflammatory erythema) — not a depression but a vascular response left after inflammation. There is no tethering to cut, so a vascular laser such as V-Beam takes this on.
• Raised scars (hypertrophic, keloid) — scars formed in the direction of excess tissue, which runs opposite to an approach that releases tissue to induce regeneration.
• Skin thinned without tethering — where the floor comes up readily on stretching, restoring dermal volume comes first.
• Active acne still in progress — releasing tissue where inflammation remains can irritate it and leave room for new scarring. Treatment to settle the acne comes first in the order.

One person's face usually carries several types together — broad rolling scars on the outer cheek alongside narrow ice pick scars further in. So the real plan is built not around "should this face have air subcision" but around "which scars, in which area, should be handled this way".

A released plane can re-adhere

This is something to know before the procedure. Cutting tethering is still a process of wounding tissue, and the body lays down fibrous tissue again as it heals that wound. As a result, an area that was released can partly re-adhere over time. This is called re-tethering, and it is one of the reasons a single session does not finish the job.

So rather than a plan built on release alone, it is usual to place something alongside it that supports the released space and keeps it from being drawn back down. TriFill can inject a material into the same needle track immediately after the release, which suits placing it precisely into the space just opened. What goes in depends on the depth of the scar and the condition of the skin.

• HA filler — immediately restores the depth of the depression and physically supports the space. The change is visible straight away, balanced against the fact that it is absorbed over time.
• Juvelook Volume (PDLLA) — a material aimed at stimulating collagen formation rather than providing immediate volume. Change appears gradually, but it is closer to tissue the body has built filling the space itself.
• Sculptra (PLLA) — the same collagen-stimulating family, considered where the aim is to raise density across a wider area.
• Re2O — an hADM (ECM) material, aimed at replenishing the extracellular matrix that tissue uses as its foundation as it settles back in.

Whatever the material, we do not recommend filling first while the tethering is still intact. With the downward pull still in place, the volume that has been added is held down by that force and does not lift as hoped. It is a clear example of order deciding the result.

Placed alongside treatments that work other layers

The layer air subcision works on is the floor of the scar. The other layers that make up a scar are handled by other treatments.

• Potenza (microneedle RF) — delivers radiofrequency to a target depth through fine needles to remodel the dermis. Surface damage is comparatively limited, which suits repeating it while managing the recovery burden.
• Fractional CO2 — creates microscopic thermal damage from the surface down into the dermis, rebuilding the walls and texture of a scar. Its role is substantial in boxcar scars with standing borders.
• CO2 laser (pinhole) — an approach that works the floor of a narrow, deep scar vertically. It is the axis in ice pick scarring.
• Dot peel (TCA CROSS) — not a laser but a chemical method applying high-concentration TCA as a point inside the scar only, considered alongside the others in narrow, deep scars.
• V-Beam — takes on the vascular response where redness remains in the scar as well.

The fact that most published studies use combined rather than standalone designs runs along the same lines. The mechanical effect of cutting tethering and the effect of rebuilding the surface complement different layers, so a plan that repeats only one of them generally leaves people less satisfied. Release the tethering and leave the surface alone and the rough texture and residual tone stay visible; work only the surface and the floor is drawn back down.

Sessions and intervals

For rolling scars and shallow boxcar scars, a plan of around 3-5 sessions is common. Intervals of 3-4 weeks are possible if it is done on its own, but in practice it is combined with other treatments, so we suggest allowing a little more time between sessions. How treatments that need recovery time and those that do not are arranged forms the backbone of the whole schedule. Adjustment is needed according to the type and depth of the scar and the skin type, and there is individual variation.

After the procedure — downtime and effect run on different clocks

Taking as given that individual variation is considerable, here is the general course stage by stage.

• Day of the procedure — the area where gas was injected swells slightly and feels as though air has got under the skin. You may feel or hear a faint crackle on touch (crepitus), and this air is usually absorbed naturally within a few hours to a day.
• Days 2-3 — the point at which bruising and swelling are most noticeable. This is because cutting tethering produces some microscopic bleeding, and it is more pronounced the wider the release.
• Weeks 1-2 — bruising fades and the visible changes largely settle. From this point, regeneration begins as new collagen fills the released area.
• Weeks to months — actual improvement in the scar appears gradually, following that process of regeneration. Comparing photographs between sessions makes the change easier to see.

In other words, the downtime you can see and the point at which the effect appears sit on different clocks. There is a stretch where the bruising has gone and the scar feels unchanged; that is closer to a natural part of the course than a sign of failure.

Known side effects and signs to have checked

The most common are bruising, swelling and temporary pain, and these usually settle within 1-2 weeks. In the published studies too, swelling, pain and erythema largely resolved within about 3-10 days. Pigmentation and infection are possible though uncommon, so following the aftercare you are given affects the result.

• Pain that worsens as time goes on
• Redness and a feeling of heat coming up together
• Swelling that keeps increasing beyond the expected period

If any of these appear, it is better to have the area looked at than to judge it yourself. Sun protection also matters during the recovery period. Post-inflammatory pigmentation often turns on aftercare more than on the procedure itself.

What we check between sessions

The extent and interval of the next session are set by reviewing how the last one went. There are broadly three things we look at.

• The response when the same area is stretched again — whether the area released last time comes up more readily than before. If there is almost no change, we also consider that tethering may remain or have re-adhered.
• How quickly the bruising and swelling cleared — for anyone whose recovery took a while, we narrow the extent of the next release or lengthen the interval.
• The character of the scarring that remains — what is left once tethering is released is usually a matter of walls or surface texture. From that point, the treatment taking the lead changes.

Scars shift in character a little with each session. An area dominated by tethering at the start may, several sessions on, have become a question of surface texture. Rather than following the original plan through to the end unchanged, switching the means to match whatever problem remains at the time tends to be more efficient in practice.

The order we follow at ABLE Dermatology

We do not settle on a device first when building a scar plan. What we check in clinic comes first, and the result of that decides which means sits at the centre.

• Is there tethering — we check region by region whether the floor follows when the skin is stretched. Where it does not follow, the role of air subcision grows.
• How the scar shapes are distributed — we record separately how rolling, boxcar and ice pick scars are mixed across the regions.
• Skin thickness and how it recovers — this becomes the basis for setting the extent of release and the interval to the next session.
• Is active acne still present — if it is, treatment to reduce the inflammation comes before the scar plan.

In regions where tethering dominates, needle release and gas release are carried out one after the other with TriFill, and where needed a supporting material is placed into the same site. Scars with standing walls are taken on by fractional CO2, narrow deep scars by pinhole or dot peel (TCA CROSS), and overall dermal density by Potenza (microneedle RF). Where redness is also present, V-Beam is brought into the sequence.

Finally, we align expectations first. The goal in scar treatment is improvement rather than complete flattening; it takes sessions and time, and results vary between individuals. That is why we set out separately, before starting, which scars this plan can change and which move on to the next stage. Start without that distinction and it is easy to be left feeling things fell short of expectation, even though the plan was in fact followed.

From consultation to procedure

A board-certified dermatologist examines you directly, identifies the layer the cause sits in, decides the device and the parameters, and the same dermatologist carries on to perform the procedure. This is not a structure in which a consultant recommends the treatment.

Sessions, intervals, maintenance timing and cost are agreed together before the first procedure.