Indented scars, known medically as atrophic scars, are depressions in the skin that result from a disruption in the body’s natural wound-healing process. This indentation occurs because underlying skin tissue, primarily collagen and fat, was lost or damaged during the initial inflammation or injury. When the skin attempts to repair itself after trauma from severe acne or chickenpox, it fails to produce sufficient structural material to fill the void. While the appearance of these scars may soften over time, the structural deficit that causes the indentation generally remains permanent without medical intervention.
Understanding Atrophic Scars and Their Types
Atrophic scars are classified into three distinct morphological types based on their shape, depth, and how they affect the dermal tissue. The specific category results directly from the severity and location of the tissue destruction that occurred beneath the surface. Understanding these differences is important for determining the most effective method for correction.
Ice Pick Scars
Ice pick scars are the most narrow and deep, characterized by a sharp, V-shaped, pitted appearance. These deep tracts extend into the dermis, often making them the most challenging type to treat effectively with surface-level procedures. They typically form following a severe, deep-seated inflammatory lesion, such as a cyst, that destroyed a column of tissue.
Boxcar Scars
Boxcar scars are wider than ice pick scars, presenting as round or oval depressions with well-defined, vertical edges and a relatively flat base. They resemble the scars left behind by chickenpox and are created when localized inflammation destroys collagen. The depth of boxcar scars can vary, but their defined walls distinguish them from other types.
Rolling Scars
Rolling scars are broad, shallow depressions that give the skin an undulating, wave-like texture rather than a sharp pit. This wavy appearance is caused by damage to the underlying subcutaneous layer, where fibrous bands of tissue form between the skin and the deeper fat layer. These scars are typically the least defined, as their edges are sloping and not sharply vertical.
The Biological Reason They Remain Indented
The reason atrophic scars do not spontaneously fill in is rooted in the structural mechanics of dermal repair and tissue loss. During the initial wound healing phase, particularly after deep inflammation, the skin’s fibroblasts are unable to synthesize enough collagen to completely replace the destroyed tissue. This results in a volume deficit where the scar tissue heals below the level of the normal surrounding skin.
Even years later, the body does not possess a mechanism to spontaneously generate the necessary new collagen and elastin fibers required to fully elevate the sunken area. The scar tissue itself is composed of disorganized collagen that lacks the strength and scaffolding of healthy skin. While the scar may lighten in color over time as post-inflammatory changes resolve, the actual depth of the indentation remains fixed.
In the case of rolling scars, an additional structural problem contributes to their permanence: the formation of fibrous tethers. These tough, cord-like bands of scar tissue anchor the base of the scar to the deeper subcutaneous tissue. This tethering actively pulls the overlying skin downward, preventing the scar from rising to the surface, even if new collagen were to form.
Modern Approaches to Correcting Indentation
Since the body will not naturally correct the structural tissue deficit, modern approaches focus on either replacing the lost volume or stimulating the skin to rebuild its own support structure. The selection of a corrective method is highly dependent on the type and depth of the atrophic scar. Subcision is a technique specifically designed to address the fibrous tethering associated with rolling scars.
During subcision, a specialized needle is inserted beneath the scar to mechanically sever the bands that pull the skin down, allowing the depressed area to lift and encouraging new collagen formation. Dermal fillers, often composed of hyaluronic acid, offer a direct method of volume replacement and are injected directly beneath the scar to immediately raise the indentation. Fillers are particularly effective for broad, rolling scars and some boxcar scars, though their results are temporary and require maintenance.
For scars that require generalized resurfacing or collagen stimulation, energy-based treatments and microneedling are frequently employed. Laser resurfacing, such as fractional CO2 lasers, creates controlled micro-injuries in the dermis to trigger a robust wound-healing response that culminates in the creation of new collagen. Microneedling, sometimes combined with radiofrequency, achieves a similar goal by using fine needles to create thousands of channels that stimulate dermal remodeling and structural protein synthesis.