Product

Aquamid^® is a non-absorbable soft volume filler for aesthetic and reconstructive purposes. The polyacrylamide hydrogel (PAAG) Aquamid^® is one of the new macromolecules that are used as implants and tissue fillers in reconstruction and aesthetic dermatology. Aquamid^® hydrogel is a 2.5% cross-linked PAAG made from acrylamide and N,N′-methylene-bis-acrylamide, ammonium persulphate/tetramethyl ethylenediamine (AMPS / TEMED) redox initiator system, and 97.5% purified water. It is not biodegradable and offers a long-lasting effect. Each batch is analyzed for consistency and compliance with product specification, including narrow tolerances of elasticity modulus, pH and impurities, and degradation products from the polymerization reaction. Aquamid^® is developed, produced, and commercialized by Contura International A/S, Søborg, Denmark. It was approved and CE marketed in Europe in 2001 for facial augmentation and minor body contouring and is available in more than 40 countries worldwide in Europe, Asia, the Middle East, and Latin America.

Aquamid^® has been evaluated in clinical trials by Von Buelow and colleagues, Christensen et al, Narins et al, and Wolter & Pallua, involving more than 5000 patients including a comparative trial in the USA. Data from these trials have been used to support a PMA application to the US Food and Drug Administration (FDA). Aquamid^® is not yet approved for sale in the USA, but is expected to get FDA approval by the end of this year.

Studies by Bello and colleagues and by De Cassias Novaes & Berg have shown that this PAAG does not migrate within the tissue after subcutaneous injection because of its large molecular size and high cohesive properties. Christensen found that cells grew well in the Aquamid^® gel, which allows vessel ingrowth from adjacent tissue. It is kept in place by means of a fibrous capsule (endoprosthesis) that develops after being injected in the subcutaneous tissue. These capsules are surrounded by fibroblasts and macrophages (Fig. 11.1). Another study by Zarini and colleagues emphasized the importance of the microstructure and porosity of hydrogels in relation to their functions and interactions with surrounding medium and tissue. Hydrogels could behave as an accessible foreign body that creates the appearance of infections that are untreatable. PAAG can exchange both physiological and non-physiological constituents very efficiently with the surrounding medium. In the context of hydrogels as tissue fillers, Brahm et al considered the ability of water and solutes (including an antibiotic) to cross between the hydrogel and the surrounding tissue to be attractive.

Figure 11.1 Microphoto of Aquamid^® injected into the chin 4 years previously. The gel (in blue) is surrounded by muscle cells (MC in red), fat cells (FC in white) and connective tissue (CT in pale red). Aquamid^® is anchored by a fine network of host connective tissue strands (see arrows).

Courtesy of Dr Lise Christensen.

The hydrogel is homogeneous, containing no microparticles or microspheres, and its filling effect is immediate. It relies exclusively on adding volume from the gel itself, unlike tissue fillers that are particle based and depend on foreign-body reaction to achieve the desired effect.

Patient selection

Patients have to have clear insight into their treatment goals and the permanent nature of Aquamid^®. It should not be injected into patients with dental caries and chronic bacterial sinusitis. The safety of PAAG has not been studied in pregnant women. Common aesthetic indications for Aquamid^® are nasolabial folds, cheek contouring, jawline contouring, nose enhancement, and marionette lines, as well as for lip augmentation, and for volumizing temples, cheeks, and chin. Aquamid^® is also used to correct signs of facial lipoatrophy or fat wasting in HIV-positive patients, as in the trial by Von Buelow.

Technique / treatment