Facial folds: choosing an implant

Folds on the face are the result of repeated and habitual contractions of the subject mimic muscles. The contraction of the facial muscles is not accompanied by a shortening of the skin and leads to the formation of folds. Other factors, such as the amount of subcutaneous fat, the water content in the skin, the distribution and ratio of collagen and elastic fibers, and biochemical changes in connective tissue and interstitial spaces, can affect the texture of the skin and, consequently, the facial creases. The main mechanisms affecting one or more of the above factors are aging, actinic damage and skin diseases. With the gradual relaxation of the skin, over time the effect of gravity on the facial tissues can lead to deepening of the folds, especially nasolabial and buccal-labial.

Many publications have been devoted to the aging of human skin. Aging of the skin, in general, is a process of atrophy. There is a slight change in the thickness of the stratum corneum, but the papillae of the dermis are lost. The number of Langerhans cells and melanocytes decreases. With age, the total volume of connective tissue of the dermis, consisting of glycosaminoglycans and proteoglycans, decreases. In aging skin, there is a significant loss of collagen fibers, so that the ratio of elastin and collagen changes in favor of the former. Appendages of the skin are also subject to aging. Sebaceous glands increase in size, although their number remains relatively constant. The number of Pacinian and Meissner corpuscles is decreasing.

Unlike normal skin, actinically damaged skin thickens with age. The main characteristic of such changes is the presence of thickened, degraded elastin fibers. This condition is described as "basophilic degeneration" or "elastosis." The amount of mature collagen decreases, and instead of usually abundant type I collagen, the immature III type of collagen begins to predominate. Now it is known that actinic skin damage causes both ultraviolet A (UVA) and ultraviolet B (UVB). Harmful doses of UVA were recorded in ordinary sunlight, most types of fluorescent radiation and in radiation used in solariums. Even exposure to UVA alone can cause skin aging, but when combined with UVB of conventional sunlight, elastosis develops much faster. In ultrastructural changes caused by ultraviolet radiation, superoxide radicals participate. Unfortunately, many commercial sunscreens that effectively block UVB do not delay UVA. In addition, heat increases the damage caused by ultraviolet radiation.

Certain dermatological conditions are manifested by excessive stretching of the skin or premature aging. Among these conditions are the Ehlers-Danlos syndrome, progeria, elastic pseudocanthoma and cutis laxa.

[1], [2], [3], [4]

Historical Aspects

The modern history of attempts to increase the volume of soft tissues begins at the end of the XIX century, when Neuber reported using small fragments of fat taken from the upper arm to reconstruct depressed face defects after tuberculous osteitis. Gersuny was the first who applied the low-melting paraffin as an injectable material to correct cosmetic deformities. In subsequent years, a large number of injecting materials were tested, including vegetable oils, mineral oil, lanolin and beeswax. It soon became apparent that injections of paraffin and other oils are very often accompanied by an inflammatory response, the formation of granules of foreign bodies and therefore unsafe. The use of paraffin ceased in Europe with the outbreak of the First World War.

Severe tissue reactions and unpredictability of the long-term results of the use of early materials led researchers in the early 1960s to the clinical testing of new highly purified polymers. The pure liquid injectable silicone, which was distributed in 1962 by Dow Corning to the acrylonitrile of medical quality, was accepted as ideal among synthetic polymers. Despite warnings that sounded in a significant number of reports, silicone soon began to be widely used to correct many soft tissue defects by direct injections in some cases of large amounts of material. The severe complications that accompanied the implantation of large volumes of liquid silicone ultimately forced the Office of Control and Quality of Food and Drugs to declare it unacceptable for direct administration. However, there were some contradictions regarding the efficacy and safety of the so-called microdroplet injection technique, popularized by Orentreich, Webster et al. Orentreich and Orentreich reported that the introduction of pure liquid silicone "was really safe and free from serious shortcomings in about 1,400 patients." Many of the undesirable effects of silicone injections were the result of the use of unknown, sometimes falsified silicone drugs, rather than Dow Corning's products. However, this product has not been approved by the Office for Control and Quality of Food and Drugs. This reflects the conscious danger of implanting millions of microparticles in the tissue in the absence of an effective method of removing them in case of complications.

Studies over the following decades have yielded many alternative materials, both from biological and synthetic materials. Among them - injectable collagen, gelatin and fat. Polytetrafluoroethylene (Teflon) paste, also used to restore the vocal cords, was used to increase the volume of tissues on the face, but the difficulty of introducing a thick paste and the excessive inflammatory reaction were an obstacle to its widespread distribution. At present, the range of alloplastic materials used is represented by synthetic substances such as silicone, polyamide meshes, porous polytetrafluoroethylene and polyester.