Dermal fillers are injectable gel-like substances used to restore volume, smooth lines, and enhance facial contours without surgery. A common concern is the possibility of the injected material moving from its intended location, a displacement known as filler migration. This phenomenon depends heavily on variables related to the product used and the administration process. Migration is not an inevitable outcome for all filler treatments.
Understanding What Filler Migration Is
Filler migration is the unintended movement of the injectable substance away from the precise area where it was placed. This movement results in an undesirable aesthetic outcome, such as an uneven appearance or altered contour, shifting the filler to a distinct anatomical area.
It is important to distinguish true migration from localized spread, which is often mistaken for it. Localized spread includes temporary post-treatment swelling or the slight expansion caused by hydrophilic hyaluronic acid (HA) fillers attracting water. A common example of genuine migration is lip filler moving above the vermillion border, creating a less defined lip line or a puffy appearance often dubbed a “filler mustache.”
Why Migration Depends on Filler Type and Injection Technique
Filler Properties
The question of whether all fillers migrate is answered by examining the fundamental properties of the filler material itself. Hyaluronic Acid (HA) fillers, the most common type, are engineered with different levels of viscosity and elasticity to suit various areas of the face. Viscosity refers to the gel’s thickness and resistance to flow, while elasticity, measured by the G-prime (\(G’\)) modulus, indicates the filler’s ability to maintain its shape under pressure.
Fillers with low viscosity and elasticity, often described as “soft,” are designed for fine lines and superficial placement but are generally more prone to displacement or diffusion. Conversely, “harder” fillers with high \(G’\) are used for deep volume restoration near the bone, such as in the cheeks or jawline. These harder fillers resist deformation and have negligible product migration.
Furthermore, HA fillers are hydrophilic, meaning they absorb water. If a less cohesive filler is injected excessively, the subsequent expansion can contribute to movement within the tissue.
Injection Technique
The skill of the practitioner and the specific injection technique employed are equally significant factors in preventing filler migration. Injecting the filler too superficially, or into an area with high muscle movement or tissue pressure, significantly increases the risk of displacement. For example, the delicate tissues around the lips and eyes are particularly susceptible to movement if the filler is not placed at the correct depth. Using an excessive volume of product in a single session, or repeatedly layering filler over time in the same area, can also create pressure that forces the gel to spread into surrounding, unintended tissue planes.
Identifying and Addressing Migration
Recognizing migration involves noticing a change in contour outside the treated area weeks or months after the procedure. Common visible signs include lumpiness or a doughy texture beyond the intended border, general puffiness, or a blurred definition of the treated feature. In areas with thin skin, such as under the eyes, a bluish tint known as the Tyndall effect may appear, which indicates filler placed too close to the surface.
Migration involving HA fillers is manageable due to their reversible nature. The standard solution is the injection of hyaluronidase, an enzyme that rapidly breaks down the hyaluronic acid molecules. This dissolving process typically results in the noticeable reduction of the unwanted filler within 24 hours. For non-HA fillers, such as calcium hydroxylapatite or poly-L-lactic acid, options are more limited, usually involving waiting for the body to metabolize the product or, rarely, surgical removal.