Deep Boxcar Acne Scars: How Do You Choose the Right Treatment?

With deep boxcar scars, the treatment choice starts with why the scar sank, not with the name of a device. Your breakouts have calmed down, but sharp-edged pits are left on your cheeks, and even under makeup they cast shadows in side lighting. Many people also tell us they've had several laser sessions and the deepest spots still look the same.

This article explains how boxcar scars with steep, vertical edges are sorted, which part of the problem lasers, TCA CROSS and subcision each handle, and what's worth checking before you start treatment.

Why don't deep boxcar scars fill in on their own?

Why don't deep boxcar scars fill in on their own?

When acne inflammation runs deep and lasts a long time, collagen in the dermis is lost and that spot sinks. These depressed scars are the most common kind of acne scar, and they rarely disappear completely on their own. Over time, red or brown discoloration fades, but the depth usually stays.

Boxcar scars are round or angular with sharp edges and a fairly flat floor. The more vertical the edge, the more shadow it casts when light hits it at an angle, so the scar looks deeper than it is. That's why treatments that only even out the surface don't lower the height of this wall very much.

There's one more thing to look at: the fibrous bands under the scar. If the scar floor is firmly attached to the tissue below, it keeps getting pulled down no matter how much collagen you try to build from above. So the deeper the scar, the more it matters to ask not only "how deep is it?" but also "what's holding it down?"

Dermis: the layer under the epidermis where collagen and elastic fibers give skin its thickness and strength.

Is your scar boxcar, ice pick or rolling?

Is your scar boxcar, ice pick or rolling?

Depressed scars fall into three main shapes. Many faces have a mix of shapes, so the starting point is to look at each scar separately.

To get a rough idea at home, gently spread the skin on both sides of a scar with your fingers. If the scar almost flattens, a pulling force from below is a big part of it. If the wall stays even when you stretch, depth and edges are the bigger problem. Ice pick scars are reported to be the most common shape, at 60 to 70% of acne scars, so it's also worth checking whether they're mixed in with your boxcar scars. The real assessment is done in the clinic, changing the light and angle.

Is your scar boxcar, ice pick or rolling?

Why does each scar shape call for a different treatment?

Why does each scar shape call for a different treatment?

Each treatment reaches a different part of the scar. A fractional laser makes tiny columns of injury close together, so new collagen forms as the skin heals, and it's used to even out the height around a scar. Subcision uses a fine needle or instrument to cut the fibrous bands pulling the scar floor down, which gives the skin room to rise again.

Subcision: a procedure that cuts the fibrous bands under a scar from inside the skin to release the sunken floor.

TCA CROSS applies a high-strength acid as a tiny dot only to the scar floor to trigger collagen renewal in that spot. It's the same acid used in peels, but because it goes only inside the scar rather than across the whole face, the strength is much higher. A literature review reported using 50% or higher for CROSS, and lowering it to 50 to 70% for darker skin.

Why does each scar shape call for a different treatment?

These strengths are ranges gathered from several studies, so they aren't numbers to apply directly to any one person. The same review concluded that TCA CROSS suits ice pick and deep boxcar scars well but works less well on rolling scars. Darkening of the skin after treatment was more frequent in darker skin, and it usually faded within 3 to 6 months with sun protection.

How STON Clinic looks at deep boxcar scars

How STON Clinic looks at deep boxcar scars

When STON Clinic looks at a deep boxcar scar, it first assesses the depth, the edge shape, the state of the scar floor, whether fibrous tethering is present, and the thickness and elasticity of the surrounding skin. Shallow scars with gentle edges can be approached with a fractional CO2 laser or another resurfacing device, while deep scars with vertical edges call for a combination of treatments. Scars that stay stuck down when the skin is stretched are candidates for subcision, and small, deep scars are candidates for TCA CROSS. Wide scars with a flat floor may not be suited to TCA CROSS, because the edges can widen or pigmentation can develop.

That's why the clinic prefers staged combination treatment over trying to finish in one go: first releasing the floor with subcision, then softening the edges with a fractional CO2 laser and other resurfacing devices. Very deep scars may be considered for punch elevation. Skin thickness, a tendency toward post-inflammatory pigmentation, any history of keloids, and whether acne is still active all need to be considered too. Asian skin carries a risk of pigmentation after strong ablative lasers or TCA CROSS, and punch surgery can leave a suture scar. The key is to identify what caused the scar to sink.

After treatment, redness, swelling and crusting can appear and usually settle within several days to about ten days. Don't wait if you notice any of the following; contact the clinic that treated you.

• The treated area gets more swollen and hot, or pus appears
• Pain doesn't ease and gets worse day by day
• After the crust falls off, the spot looks wider or rises up hard

If you're still getting new breakouts, it's better to calm the inflammation first and then plan scar treatment. At your consultation, try starting with "Is depth or tethering the bigger problem with my scars?" When you contact the clinic, include when the scars appeared, whether you're still breaking out, and a photo of the scars that bother you taken in side lighting.