Facial folds: choosing an implant

Facial folds are the result of repeated and habitual contractions of the underlying facial muscles. Contraction of the facial muscles is not accompanied by shortening of the skin and results in the formation of folds. Other factors such as the amount of subcutaneous fat, the water content of the skin, the distribution and ratio of collagen and elastic fibers, and biochemical changes in the connective tissue and interstitial spaces can affect skin texture and, therefore, facial folds. The main mechanisms that affect one or more of the above factors are aging, actinic damage, and skin diseases. With gradual relaxation of the skin, over time, the effects of gravity on facial tissues can lead to deepening of folds, especially the nasolabial and buccal folds.

There are many publications devoted to the processes of human skin aging. Skin aging is generally an atrophic process. There is a slight change in the thickness of the stratum corneum, but the dermal papillae are lost. The number of Langerhans cells and melanocytes decreases. With age, the total volume of connective tissue in 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 to collagen changes in favor of the former. Skin appendages are also subject to aging. The sebaceous glands increase in size, although their number remains relatively constant. The number of Pacinian and Meissner corpuscles decreases.

In contrast to normal skin, actinically damaged skin thickens with age. The main characteristic of these changes is the presence of thickened, degraded elastin fibers, a condition described as "basophilic degeneration" or "elastosis." The amount of mature collagen decreases, with immature type III collagen becoming predominant instead of the normally abundant type I collagen. It is now known that actinic damage to the skin is caused by both ultraviolet A (UVA) and ultraviolet B (UVB). Harmful doses of UVA have been documented in normal sunlight, most fluorescent lights, and the radiation used in tanning beds. Even exposure to UVA alone can cause skin aging, but elastosis develops much more rapidly when combined with UVB from normal sunlight. Superoxide radicals are involved in the ultrastructural changes induced by UV radiation. Unfortunately, many commercial sunscreens that effectively block UVB do not block UVA. In addition, heat increases the damage caused by ultraviolet radiation.

Certain dermatological conditions manifest as excessive stretching of the skin or premature aging. These conditions include Ehlers-Danlos syndrome, progeria, pseudoxanthoma elasticum, and cutis laxa.

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Historical aspects

The modern history of soft tissue augmentation attempts begins in the late 19th century, when Neuber reported the use of small fragments of fat taken from the upper arm to reconstruct depressed facial defects following tuberculous osteitis. Gersuny was the first to use low-melting paraffin as an injectable material for the correction of cosmetic deformities. In the following years, a large number of injectable materials were tried, including vegetable oils, mineral oil, lanolin, and beeswax. It soon became apparent that injections of paraffin and other oils were very often accompanied by an inflammatory reaction, the formation of foreign body granulomas, and were therefore unsafe. The use of paraffin ceased in Europe with the outbreak of World War I.

Severe tissue reactions and unpredictable long-term results with early materials led investigators in the early 1960s to clinical testing of new highly purified polymers. Pure liquid injection silicone, marketed in 1962 by Dow Corning as "medical grade silicone," was accepted as the ideal synthetic polymer. Despite warnings in a significant number of reports, silicone soon became widely used for the correction of many soft-tissue defects by direct injection of, in some cases, large quantities of material. Severe complications associated with the implantation of large volumes of liquid silicone eventually led the Food and Drug Administration to deem it unacceptable for direct injection. However, some controversy remains regarding the efficacy and safety of the so-called microdroplet injection technique popularized by Orentreich, Webster, et al. Orentreich and Orentreich reported that injection of pure liquid silicone "was found to be safe and without serious adverse effects in approximately 1,400 patients." Many of the adverse effects from silicone injections were the result of unknown, sometimes adulterated silicone preparations, not the Dow Corning product. However, this product has not received FDA approval. This reflects the perceived danger of implanting millions of microparticles into tissues without an effective way to remove them if complications develop.

Research over the following decades yielded many alternative materials derived from both biological and synthetic materials. Among them are injectable collagen, gelatin, and fat. Polytetrafluoroethylene (Teflon) paste, also used to reconstruct vocal cords, was used to increase the volume of facial tissue, but the difficulty of injecting the thick paste and the excessive inflammatory reaction prevented its widespread use. Currently, the range of alloplastic materials used includes such synthetic substances as silicone, polyamide mesh, porous polytetrafluoroethylene, and polyester.