# Polyacrylamide Injection vs. Polylactic Acid in HIV Related Lipodystrophy: A RCT Systematic Review
## 4 Discussion  
Facial lipoatrophy is a distressing clinical condition for HIV patients treated with antiretroviral therapy. The psychological impact is significant in many patients, and it may even lead to a lack of compliance and adherence to the treatment [12]. Biological and synthetic fillers have been developed for soft tissue augmentation and facial contouring, but none of these have been considered the method of choice to treat lipoatrophy. Humans, since the dawn of time, have searched for eternal youth as a key to happiness. Facial features have always been an important region where we concentrated efforts. Facial painting, tattooing and piercing have been used to enhance appearance. Over the years, aging leads to a modification of the countenance, genetic factors and environment playing an essential role. Even if skin shows the most visible aging damage, modification of the deeper anatomic levels has an important role, especially in the skull and facial fat pad [33]. Considering facial filler agents, the aim of their use is to find the perfect substance to replace volume and fill lines in the face. The first filler developed was paraffine in the 1850s, and the late 1800s introduced autologous fat injections for facial augmentation. Its use is still popular today but presents unpredictable longevity [34; 35]. The 1940s saw the first introduction of liquid silicone, first used in Japan for breast augmentation, and in the 1960s it became a popular cosmetic treatment all over the world. In 1979 the FDA condemned the use of injectable silicone for its disastrous sequelae, such as granuloma and fistula [36]. In 1981, the FDA approved bovine collagen for cosmetic use, released as a product called Zyderm (Allergan, Inc., Irvine, CA, USA) [37]. The movie industry and society of the 1980s and 1990s gave a big boost to the use of filler. A turning point was the approval of hyaluronic acid (HA) in 2003. It is a highly hydrophilic glycosaminoglycan that is part of the extracellular matrix of a large variety of tissues in all organisms. Thanks to its features, HA remains the most widely used filler material [35]. Polyacrylamide gel is a volumetric gel, consisting of 2.5% cross-linked polyacrylamide and 97.5% pyrogen-free water. This filler has been proven to be stable, nontoxic, nonallergenic, nonembryotoxic and nonabsorbable [38]. PH produces an increase in subcutaneous thickness of both nasolabial lines, which is maintained even after 36 months from its application [39]. Although, some cases of significant complications, such as cold and hot abscesses 10 years following the injections, have been reported [40; 41]. Poly-l-lactic acid (PLA) is a biocompatible, biodegradable synthetic polymer derived from lactic acid that has been used since the mid-1990s in various maxillofacial and orthopaedic procedures [41]. Intradermal injections overlying facial lipoatrophic areas leadto a dermal width increase due to fibroblast recall and collagen deposition, which reduce the physical signs of lipoatrophy [42]. PLA is generally well tolerated, usually showing minimal adverse events. Occasionally, there can be more serious adverse effects, such as subcutaneous nodules or granulomas formation. Some of the causes are thought to be derived from inadequate dilution, an allergic or aberrant inflammatory response or a superficial injection technique [43]. Standard criteria for the use of permanent filler in HIV-related lipodystrophy are still lacking. [PERSON] et al. proposed 2 mL of product (1 vial = 1 mL) be injected in every filling session. This kind of approach was made to induce a very minimal tissue response [44]. The study compared outcomes between a mega-filling approach and a gradual build-up, but it did not show differences in terms of safety. Nevertheless, he concluded that with the mega-filling procedure patient satisfaction is achieved earlier, and it also leads to a reduction of hospital costs. [PERSON] et al.