Implants: synthetic fillers

Although most of the injected and implantable materials used to increase the volume of soft tissues are of biological origin, a number of synthetic materials have also been used for this purpose, with varying success.

Some of the newly developed materials are promising for their permanence and stability.

[1], [2], [3]

Liquid silicone

Silicone is a polymer of dimethylsiloxanes. Liquid silicone is a clear, colorless and relatively inert liquid. As an injectable material, before entering the United States, it was first used in Asia, Europe and Latin America. In 1963, Dow Corning (USA) created liquid medical silicone 360, and later - a cleaner form of silicone, MDX 4-4011.

The technique of silicone administration is probably the most critical moment of successful treatment. It must be introduced into the dermis and fat in the smallest amounts. Each particle is closed in a fibrous capsule during the following weeks. The increase and filling of the tissue is the result of a fibroblastic reaction, and not just the presence of silicone. The fibrotic reaction and the formation of the capsule occur within a few weeks. Since the implantation of silicone leads to a permanent result, extreme care must be taken, and a deliberately inadequate correction is strongly recommended here.

Implantation of silicone is accompanied by already described serious complications, including inflammation, densification, discoloration, ulceration, displacement and the formation of silicone granulomas. It should be noted that many of the complications described are the results of using silicone implants of unknown purity or even falsified silicone containing olive oil or other components, rather than purified Dow Corning silicone (MDX 4-4011). Liquid silicone obtained the permission of the Office for Control and Quality of Food and Drugs for Ophthalmic and Orthopedic Use in 1994. However, injection silicone has not yet received approval for use in order to increase tissue and remains dangerous due to the irreversibility of the procedure.

Polymethyl methacrylate (Artecoll)

Microspheres of polymethyl methacrylate (PMMA) (Artecoll, manufactured by Rofil Medical International, the Netherlands) are used in Europe as an injectable filler. The microspheres are 20-40 μm in size - large enough to not undergo phagocytosis, but small enough to use them intradermally. PMMA is supplied in a 3.5% collagen solution containing 0.3% lidocaine. Microspheres have a smooth surface and in the first 2 days are covered with a layer of monocytes, after 2 months - with a layer of fibroblasts and after 7 months - with a fibrous capsule. The main indications for the use of Artecoll are natural wrinkles and wrinkles on the face. Usually, 1 ml of the drug is sufficient to correct the folds in the area of the nadriposity, nasolabial folds, sagging of the corners of the mouth and to increase the lips. Artecoll is not suitable for correction of "crow's feet", because they are too superficial.

Frequent reactions to injections of Artecoll are edema, erythema, mild pain and itching, which last for several days. Other, serious complications are rare. However, due to the irreversibility of the effect, patients who are displaced, have an inflammatory reaction or infection, can not offer any alternative treatment other than extensive tissue excision. In cosmetic terms, this makes the material less attractive and even dangerous. The experience of its application is limited and the long-term results are unknown. Artecoll is not approved for use by the Food and Drug Administration.

Bioplastique

Bioplastique (manufacturer of Uroplasty, the Netherlands) is a white, highly textured, two-phase polymer with a solid phase containing microparticles of textured vulcanized silicone rubber and a liquid phase containing a biocompatible plasdon hydrogel. It is an inert injection material with the limitations inherent in injectable silicone. Since microparticles have a diameter of 100-400 μm, they are not captured by macrophages, since phagocytosis is limited to particles having a size of less than 60 μm. Because of the large particle size, Bioplastique can not be injected into surface tissues, but it is ideal for subcutaneous placement. The drug can be used to correct retracted scars, sunken cheeks, deformities of the back of the nose, subcutaneous contour defects and to increase the lips. Bioplastique is too bulky to correct creases, wrinkles and superficial nets. Since the fibroblast reaction and collagen deposition continue for several weeks, give an additional increase in volume and a life-long result, a deliberately inadequate correction of scar defects is recommended. Hyper-correction can lead to contour violations.

Several studies have revealed a giant cell reaction to Bioplastique as a foreign body. Histological analysis showed an acute moderately pronounced inflammatory reaction, which changes into chronic inflammation as the gel carrier dissolves. The hydrogel is replaced by fibrin, and then - by fibroblasts. After 7 days, macrophages merge into giant cells, since they can not phagocyte these particles. Giant cells remain in a stable form on the surface of the particles.

Complications arise if the material is injected superficially into the skin, or too much material is injected to form a dense palpable mass. In such cases, the implant and surrounding tissue can be removed with microliposuction or surgical excision. Considerations about the irreversibility of changes and the possibility of developing a chronic inflammatory reaction limit the spread of this drug. It is not available in the United States, and its use is not authorized by the Food and Drug Administration.

[4], [5], [6], [7], [8]

PTTPE (porous polytetrafluoroethylene)

Porous polytetrafluoroethylene (Ultrasoft, manufacturer of Tissue Technologies Inc., USA, Gore-Tex, producer of WL Gore, USA) is an extremely biocompatible, inert alloplast on a carbon base that has been used for more than 20 years to produce reliable and effective vascular prostheses. After the beginning of use as a vascular material in the 70s of the last century, the field of application of pPTFE was expanded to the plasty of hernias and reconstructive-cosmetic operations. The advantages of this prosthetic material are well established and documented. The PCTFE has a multi-axis microstructure consisting of nodules connected by thin fibrils, and is produced with a different "pore size". It is easy to work with, it causes minimal tissue reaction and is non-pathogenic. After implantation, the material retains its strength, thickness, size and flexibility. Its microfibrillar structure allows insignificant penetration of cells and ingrowth of connective tissue. Comparative studies of various forms of PPTPE showed the superiority of the tubular form (Soft-Form) with respect to the stability and ingrowth of the tissue. Longitudinal tissue ingrowth and lumen of the implant better fix it and minimize the risk of migration. Meanwhile, the relatively small migration of fibroblasts into the implant wall makes it easily removable.

SoftForm is available in a kit that includes material for implantation and a cutting trocar placed in an external cannula. Implants are 5, 7 and 9 cm long and 2.4, 3.2 and 4 mm in diameter. They are used to correct nasolabial folds and perioral area, scars on the face, soft tissue defects and to increase the lips. The procedure is performed in the medical office under local anesthesia, after careful labeling of a soft tissue defect, crease or wrinkle in the patient's upright position. To achieve the desired correction, it is necessary to accurately tunnel the trocar cavernter of the subcutaneous tissue under the defect.

When using Softform, there are two unacceptable long-term complications. It is noticed that in a few weeks after implantation the material becomes denser (more palpable). It is assumed that this is due to ingrowth into the walls of the material - for example, into the walls of the tube. In addition, many patients noted its shortening in the longitudinal direction, especially in the lips. This is a consequence of the "accordion" effect in the thick walls of the tubes. Ultrasoft for implantation in the lips is made with thinner walls (softer before and after implantation) and longer. Early results show that the characteristics of this implant are significantly improved compared to Softform.

To correct the nasolabial fold, small punctures are made in the fold, approximately at the level of the oral adhesion, and in the furrow at the wing of the nose. Tunneling of the subcutaneous tissue is made by the end of the trocar. Excessive resistance to its progress means an incorrect depth, while the trocar should be removed and moved, as a rule, a bit deeper. When the implant becomes visible in both the input and output punctures, the cannula and trocar are extracted. The skin over the implant is massaged to evenly position the material, and its excess is cut off. Both lumens of the implant are left open (for ingrowth of the connective tissue), they sink into the wound, and the incisions are sutured with non-absorbable monofilament threads. For several days locally and orally administered antibiotics. In most cases, the input and output punctures become invisible after a short healing period, but if the punctures are not properly sewn, it may require a slight grinding.

When the lips are enlarged, the same principles are used as in the correction of nasolabial folds. For the upper lip, better results are obtained by an increase in the red border with two segments of the implant, with the preservation of cupid onions. Implant immediately under the edge of the red border of the upper lip. The installation of the third implant after 3 months after the initial correction of the red rim can give a "wrenching effect", increasing the magnification. Such a "triangular" technique increases the vertical height of the lip. The lower lip is usually enlarged by one long (9 cm) implant on the entire lip, located under the edge of the red border. Complications involving repression are rare and, in most cases, involve defects in technique. Short-term swelling and redness above the implantation site are expected. Ultrasoft is approved for use by the Office of Control and Quality of Food and Drugs and is available in the United States.

Botulinum exotoxin

The use of botulinum exotoxin in cosmetic surgery has recently become widespread. Its introduction into cosmetology is based on the fact that folds on the face are significantly reduced in patients treated with botulinum exotoxin A (BTX-A) for idiopathic blepharospasm. The effect of BTX-A on folds and lines is due to the fact that many of them are formed as a result of reduction of the underlying muscles. Weakening or paralyzing the corresponding muscle, BTX-A can lead to a smoothing of the face.

Some properties of BTX-A make it attractive for correcting skin folds, as an alternative to surgery and filling techniques. BTX-A is safer, locally more effective, and it is easier to apply. In addition, the toxin acts selectively and reversibly; so it gives relatively few adverse reactions.

Botulinum neurotoxin (BTX) is produced by the anaerobic bacterium Clostridium botulinum. It exists in seven serotypes, from A to G, of which the most powerful with respect to the paralysis of the muscles of a person is BTX-A. Although other serotypes (for example, BTX-B and BTX-F) are currently being studied, only BTX-A is commercially available.

BTX-A causes muscle paralysis due to presynaptic fixation on the cholinergic nerve endings and blockade of the release of acetylcholine into the neuromuscular synaptic cleft. The unique mechanism of action of BTX-A makes it very specific, allowing a small amount of toxin to exert a pronounced effect. This makes it possible to obtain a curative effect from small doses, making systemic effects unlikely.

In therapeutic doses, BTX-A begins to act 2 to 3 days after administration. The maximum muscle relaxation occurs approximately 1-2 weeks after the injection, when the muscle fibers begin to atrophy. This process lasts up to 4 weeks. Although BTX-A leads to an irreversible blockade of cholinergic nerve endings, the restoration of normal muscle activity occurs as a result of renewal and healing, resorption of inactive endings, axon growth and the formation of new neuromuscular synapses. The effect of BTX-A lasts 3-6 months, after which enzyme activity returns to the neuromuscular synapses. That is, the effect of the drug is prolonged. However, histological changes after the introduction of BTX-A can persist for up to 3 years. Despite this, muscle fibers are normal in activity and strength.

Currently, three BTX preparations are available: Botox (manufactured by Allergan, USA), Dysport (manufactured by Ipsen, UK) and Mysbloc BTX-B (manufactured by Elan Pharmaceutical, USA). Clinically, Botox is three to four times higher than Dysport in strength (in mouse units), and its dose must be selected according to this. Botox is available in vials and must be diluted with sterile saline solution before intramuscular injection. Each vial contains 100 units of toxin type A C. Botulinum, 0.5 mg of human albumin and 0.9 mg of sodium chloride in a sterile, lyophilized form, without preservative. 100 Botox units are significantly less than the calculated average lethal dose - (LD50) for an average person weighing 70 kg (2500-3000 units).

BTX-A is successfully used to treat folds above the bridge of the nose, "crow's feet", horizontal lines on the forehead, neck, chin creases and fine lines. It is also used for asymmetry or paralysis of the face to reduce the expressiveness of the healthy side. BTX-A is administered intramuscularly along the folds. The toxin exposure can range from slight weakening to complete paralysis of the muscle, which mainly depends on the dose administered. The clinician must determine the number of injection sites and the severity of the effect after paralysis. Obviously, it is necessary to carefully consider individual differences in anatomy and muscle function.

Injections of BTX-A have recently been successfully used as a minimally invasive measure for temporary lifting of the eyebrows. In this case, 8-10 Botox units are inserted into the lateral and lateral fibers of the circular muscle of the eye, under the lateral third or half of the eyebrow. This injection weakens the lateral part of the circular muscle, leaving the lifting effect on the eyebrow an eye unaffected, which results in a slight uplift of the lateral part of the eyebrow. At the same time, the goose paw correction is usually performed at the lateral angle of the eye.

Introduction BTX-A gives very few complications, and its effects are reversible. Known complications include ptosis after insertion into the area of the nadperium, as a result of toxin migration through the orbital septum to the lifting muscle, and temporary sagging of the lower eyelid after correction of the goose paw. Also, omission of the eyebrows after correction of the frontal folds is reported. Moreover, BTX-A has immunogenic properties, although no cases of antibody production as a result of the use of BTX-A in therapeutic doses for cosmetic purposes have been observed.

A newer form of BTX, botulinum toxin type B, in clinical trials showed promising results. It acts much faster, indefinitely stable in solution (can be stored) and approved by the Office of Control and Quality of Food and Drugs for neurological use. The duration of action of this drug is not yet clear.

In the minimally invasive correction of the folds of the facial skin and the increase in soft tissues, significant advances have been made. Although there is no single material or method for all clinical cases, doctors are given a wide range of options. Meanwhile, as modern methods are being developed, research is continuing on the development of new materials. The methods of injection and implantation, as part of the clinical arsenal for facial rejuvenation, are welcomed by both the medical community and the general population. Since many of the methods have been developed recently, in order to guarantee the expected results, further accumulation of experience and analysis of long-term results is required.

[9], [10], [11], [12]