Long-Term Filler Complications: Polyacrylamide Versus Hyaluronic Acid

Injectable fillers have been used in cosmetic medical practice for many years now and have generally been regarded as being safe products. However, problems do arise with their use. They may be divided into 3 groups relating to duration of action: non-permanent, semipermanent and permanent fillers. The authors examine long-term adverse outcomes of injectable fillers and compare the largest group of fillers, hyaluronic acid (HA), and the ‘permanent’ filler polyacrylamide gel (PAAG). In each group, there is a core element, HA and PAAG respectively, associated with various adjuvants. Hyaluronic acid fillers have broadly the same molecular structure and are comparable as with long-term adverse events. There are larger relative differences in the PAAG grouping. Polyacrylamide gel under the name Aquamid has been available and widely used from 2001 in Europe, Asia and South America. Even though multiple clinical research was conducted on efficacy and safety, several papers describing complications have gained attention. The authors sought to assess the safety profile and long-term complications of Aquamid PAAG and compare them with the HA. They conducted a narrative review of all the relevant studies describing long-term complications of Aquamid and HA used as dermal fillers for facial soft tissue augmentation for aesthetic purposes. A PubMed search for articles published from 2003 to 2023 was undertaken. Papers where Aquamid was injected in patients with HIV-related facial lipoatrophy were included and papers where Aquamid was used for augmentation purposes of other parts of the body were excluded. Papers focusing on early complications, PAAG other than Aquamid, animal studies and papers not in English were also excluded. The overall complication rate after Aquamid injection was between 0.14% and 2% with no convincing evidence of classic foreign body granuloma (FBG) formation in large cohorts, though inflammatory nodules have been reported in selected cases. The incidence of delayed inflammatory reactions after HA filler injection is 1.1% per year, while the incidence of type 4 hypersensitivity reactions and FBG is 0.06% and 0.02% to 1% per year, respectively. Complications related to the permanent filler Aquamid or any other filler could be related to the product, the patient or the injector. They can also be classified as immediate or long term. Careful attention to patient selection, education and injection technique can minimize their incidence therefore selecting appropriate patients is the first step in reducing the complication risk. It is our view that both permanent (PAAG) and temporary fillers (HA) may be the cause of devastating complications.