Fractional laser technology: a compromise between efficiency and safety

At present, in the arsenal of modern dermatocosmetology there is a fairly wide range of methods to correct various aesthetic skin imperfections: chemical peels, mechanical dermabrasion, laser resurfacing, microdermabrasion, contour plastics. and others. However, new directions and technologies in the beauty industry are constantly developing and improving.

This trend is especially typical for hardware methods, primarily laser medicine. The use of lasers, first in dermatology and then in cosmetology, has an impressive period. Even since the appearance of one of the newestLaser treatment methods (selective photothermolysis) have passed more than 25 years. The pioneers of this direction, the Americans RR Anderson and JA Parrish, predetermined the fate of fractional lasers in medicine, making them indispensable in the treatment of such aesthetics. skin imperfections such as capillary hemangiomas. Port wine stains, hypertrichosis, tattoos, rosacea, pigmentation disorders, photoaging, wrinkles, etc.

Modern skin reshaping techniques

We live in a time when more people are reaching old age than ever. And since many of them continue active life, one of the most important problems in aesthetic medicine is the fight against skin aging.

Plastic surgery can rejuvenate the shape of the face by removing excess skin. However, at the same time, the skin is still altered by time (age-related aging) or external factors (photoaging). It is also important that most patients want to look younger without surgery.

In this case, what method should be used to influence the skin and what must happen to it for its true rejuvenation?

All the methods that can be used to improve the appearance of the skin are united by one principle: they use a traumatic effect on the skin, causing fibrosis, which leads to its tension and compaction.

Currently, dermatocosmetology uses three main types of skin reshaping effects, including:

• chemical stimulation: chemical peels with acids (trichloroacetic, glycolic, etc. );
• mechanical stimulation: mechanical dermabrasion, microdermabrasion, mesotherapy, fillers, subcision with needles;
• thermal stimulation: laser ablation, laser heat setting and broadband light sources, radiofrequency surveying, fractional methods.

Chemical stimulation

Historically, acid exfoliation (peeling) was the first method of skin rejuvenation. The principle of peeling is partial (as with superficial peeling) or almost complete (as with medium and deep peeling) destruction of the epidermis, damaging fibroblasts and structures of the dermis. This damage triggers an inflammatory reaction (the more powerful, the greater the volume of destruction itself), which leads to additional collagen production in the skin.

However, to achieve the desired result, the peel has to sacrifice the epidermis. The burn experiments have misled many, supposedly "proving" that the epidermis is a self-renewing organ that quickly recovers from damage. zone. In this sense, peels until some time ago became more and more aggressive towards the epidermis (for example, deep phenolic peeling), until finally the accumulated problems made specialists realize the cruelty of this method that finally leadsto thinning of the skin.

Deep peel advocates ignored emerging issues. Its essence was that due to the destruction of the dermis papillae and the weakening of nutrition, the epidermis becomes thinner and the number of cells in the spiny layer is significantly reduced in comparison. with what was before the peeling. A decrease in the barrier function of the stratum corneum leads to a decrease in the hydration of the skin. (Therefore, almost all patients after deep peeling for a long time experience severe dryness of the skin) At the same time, the introduction into practice. the lighter peels (using trichloroacetic and fruit acids) did not live up to their hopes of effectively tightening the skin.

Mechanical stimulation

Of the methods of mechanical stimulation of involutional changes in the skin, dermabrasion with the use of rotary devices (with a speed of v; rotation of cutters up to 100, 000 rpm) deserves special attention. Currently, modern devices from Schumann-Schreus (Germany) are used

The method can only be used in a surgical hospital, as the procedure requires anesthesia, postoperative treatment of the wound surface, a special toilet for the eyes and mouth, as well as devices to feed the patients (due to thefact that the pronounced postoperative edema that occurs 2-3 days after the procedure makes it difficult to open the eyes and mouth).

The method is very effective, but unfortunately with mechanical dermabrasion there is a high risk of complications such as:

• Persistent postoperative hyperemia;
• the appearance of areas of depigmentation due to the destruction of melanocytes when the cutter penetrates through the basement membrane;
• infection of the wound surface;
• scars (if the cutter dives too deeply into the skin)

All of the above has determined the limited application of this method in clinical practice.

Thermal stimulation

Ablative remodeling

Since the late 1980s, a laser has been used to rejuvenate the skin by removing tissue layer by layer (ablation) [4]. Gentle and minimally traumatic removal of the top layer of the skin with a carbon dioxide laser stimulates the synthesis of your own collagen in it. the amount of which increases several times after the procedure. Then it gradually rearranges itself.

The most effective was the use of a CO2 laser, when it was exposed to a deep thermal effect in all layers of the dermis, externally manifested by the tightening effect of the skin. The method is called "laser dermabrasion" or "laser skin resurfacing", and in terms of efficacy it could not be opposed to any other skin resurfacing method that existed at the time (Fig. 1).

Fig. 1. Traditional laser skin resurfacing scheme (laser dermabrasion)

However, the CO2 laser also causes a lot of complications. Furthermore, subsequent studies have shown that such a profound effect on the dermis stimulates the formation of fibrous tissue to a greater extent than it contributes to the synthesis of new normal tissue. oriented collagen [5]. The fibrosis that develops can make the skin look abnormally pale. The collagen synthesized after treatment is reabsorbed after a few years, like any collagen formed at the site of the scar. As a result of thinningthe epidermis caused by the atrophy of the papillary layer of the dermis, fine wrinkles begin to appear on the skin. Due to the weakening of the barrier function of the stratum corneum, the level of hydration of the skin decreases and it looks atrophic.

Erbium-aluminum-yttrium garnet-erbium lasers appeared somewhat later. Such advantages of an erbium laser as a lower thermal penetration depth (erbium lasers penetrate to a depth of 30 μm, CO2 lasers - up to 150 μm) and (as a result) the lower risk of burns and charring of tissuesAs well as their relative cheapness (compared to carbon dioxide lasers), they attracted the attention of many specialists around the world.

However, as the experience of working with these two types of installations accumulates, the opinion has developed among specialists that CO2 lasers are more efficient [6]. Despite the negative effects of carbon dioxide laser dermabrasion described above, this method remains indispensable for the correction of acne scars. Furthermore, it can be considered as an alternative to surgical skin tightening: of all reshaping methods, only exposure to a CO2 laser can cause a pronounced collagen contraction with visible clinical lifting effect.

The problem with all the methods described above is that they often "sacrifice", that is, they significantly damage the epidermis. To rejuvenate your skin and look really young, you need a perfect epidermis with dermal papillae, good hydration, normal skin tone and elasticity. The epidermis is a very complex and highly specialized organ, up to 200 microns thick, which is our only defense against the effects of negative environmental factors. Therefore, whatever we do to rejuvenate the skin, we must ensure that its underlying normal architecture is never damaged.

This concept contributed to the emergence of non-ablative skin reshaping technology.

Non-ablative remodeling

The most common devices for non-ablative skin reshaping are neodymium lasers (Nd-YAG) and diodes, as well as broadband light sources (IPL). The principle of its action, selective photothermolysis, consists in the heating and destruction of structures, which contain a sufficient amount of melanin or oxyhemoglobin. In the skin, they are, respectively, accumulations of melanocytes (lentigo, melasma) and microvessels (telangiectasia). The emitted wavelengths used in non-ablative lasers correspond to the maximums of the absorption spectra of oxyhemoglobin or melanin. The procedure for treatment with non-ablative lasers and IPL is quite safe, the rehabilitation period is minimal, however, such treatment removes only cosmetic pigments and vesselsdefects. In this case, there is a certain thickening of the skin, but the effect obtained is short-lived.

Fractional skin reshaping techniques

The constant search for new, highly effective and safe skin rejuvenation methods has led to the emergence of a revolutionary technology: fractional delivery of laser radiation. The proposed skin rejuvenation method has been specially designed to overcome some of the above difficulties. Unlike "conventional" ablative and non-ablative laser methods, which are designed to achieve uniform thermal damage to the skin at a specific depth, fractional methods allow to achieve their selective microscopic thermal damage in the form of numerous altered columns and leave areasunaffected around these micro-wounds. The industry currently produces two types of fractional lasers: non-ablative and ablative.

The first uses an erbium-doped optical fiber that generates radiation at a wavelength of 1550 nm. The fractional laser forms thousands and tens of thousands of column-shaped microdamages on the skin - microthermal treatment zones (MLZ) - with a diameter of 70-150mk depth up to 1359mcm

As a result, about 15-35 skin is photocoagulated in the treated area. The chromophore of the laser is water and coagulation occurs mainly in the lower layers of the epidermis and dermis. The stratum corneum remains intact because it contains a relatively small amount of water, and this significantly reduces the risk of infection. Epidermal recovery is rapid due to the low volume of the lesion and the short migration distance of the keratinocytes. The healing period is accompanied by moderate edema and hyperemia, followed by desquamation, which appear on day 5-7. The patient practically does not lose social activity.

This technology, fractional photothermolysis (FF), is a highly effective method of non-ablative fractional skin reshaping. To achieve the desired effect, a course treatment is prescribed. Depending on the clinical situation, it is recommended to perform 3 to 6 procedures with an interval of 4-6 weeks. As with any other non-ablative skin reshaping method, the end result can be seen only 4-8 months after the procedure (cumulative effect).

In cases where a more aggressive effect on the skin is required, for the correction of scars, the removal of deep wrinkles and excess skin, the fractional ablation method is used (FA or fractional deep dermal ablation -FDDA).

The fractional ablation method combines the advantages of a CO2 laser and the fractional principle of laser radiation delivery. Unlike traditional CO2 lasers, which remove the entire skin surface layer by layer, AF units form a large number of microablativezones (MAL) up to 300 µm in diameter at a vaporization depth of 350 to 1800 µm(Fig. 2).

Therefore, during this procedure, laser radiation, penetrating the deep layers of the skin, destroys the upper layer of the epidermis. In terms of efficiency, ablative fractional laser resurfacing can be compared to plastic surgery, this is the depth at which the laser beam resurfaces.

Fig. 2. The principle of operation of the ablative fractional laser: the formation of microablative zones - MAZ (a); dependence of the MAZ formation depth on the laser radiation power (b)

As in the case of FF, 15 to 35% of the skin in the treated area is actually exposed (in some cases, up to 70%). Recovery after the AF procedure is faster than after layer-by-layer ablation. This is due to the fact that important parts of the epidermis and the stratum corneum remain intact. Skin bleeding is observed for some time immediately after the procedure, but soon stops (Fig. 3 a, b).

Fig. 3. Step-by-step skin restoration after fractional ablation procedure: see immediately after treatment (a); every other day (b); after 5 days (c); 14 days (d) after a procedure

Numerous microbleeds appear in the dermis, inducing a complex cascade of changes that lead to the production of new collagen. Once the bleeding stops, it is necessary to remove the serous fluid that remains on the surface of the skin. Its release is observed within 48 hours after the procedure, until complete epithelialization of the microablative areas occurs. During this period, the patient uses special external agents to heal wounds. It usually starts in 3 to 4 days. flaking and swelling are increased (Fig. 3 c). By the seventh day, these phenomena gradually subside and erythema remains the only perceptible side effect (Fig. 3d). The duration of the erythema depends on the parameters of laser exposure. and characteristics of the vascularization of the skin. According to the author's observations, the erythema does not last more than 3 months.

The patient's loss of social activity after the FA procedure lasts 5-10 days.

To prevent scars and the manifestation of post-inflammatory pigmentation, it is necessary to take careful care of the skin. Decorative cosmetics can be used for 4-5 days. A prerequisite for a good result is the use for at least 3 months after the procedure of sunscreen cosmetics with a high degree of protection (SPF at least 50). The risk of post-inflammatory pigmentation occurs in 20% of patients and is generally higher in patients with skin types IV-V. Such hyperpigmentation is transient in nature and can last from 1 week to 3 months, which also depends on the depth of treatment and the area of ​​the treated area. For its prevention 1-2 weeks before the procedure and for another 2 weeks after, external agents based on hydroquinone (4%) and tretinoin (0. 1%) are prescribed. The main effects on the facial skin after the AF procedure are the following: pronounced tightening and reduction of excess skin, leveling the surface wrinkled skin, as well as skin affected by acne scars, reduction of dyschromia, porosity.

This method was tested by the author and his colleagues also to remove stretch marks from the skin. As clinical studies show, the method has shown high efficacy in removing almost all types of stretch marks, both acquired in the puberty period and postpartum. It was observed that the healing processes in the skin of the body are different from those of the facial skin.

Mechanism of skin remodeling when fractional lasers are used

Let's consider the skin reshaping mechanisms when using fractional lasers.

After laser exposure, aseptic inflammation develops in the area of ​​the micro-wounds formed. The more aggressive the laser exposure, the more pronounced the inflammatory response, which, in fact, stimulates post-traumatic release. growth factors and infiltration of tissues damaged by fibroblasts. The next reaction is automatically accompanied by a burst of cellular activity, which inevitably leads to the fact that fibroblasts begin to produce more collagen and elastin. The skin reshaping process includes three classic phases of regeneration:

• phase I - alteration (tissue inflammation). Starts immediately after damage;
• phase II - proliferation (tissue formation). It begins 3 to 5 days after injury and lasts about 8 weeks;
• phase III - tissue remodeling. Lasts from 8 weeks to 12 months.

It should be noted that the three phases of skin remodeling are observed both after fractional photothermolysis and after fractional ablation. But in the first case, the damaging effect of the laser is moderately aggressive, as a result of which a cascade of inflammations, the change is never too wild.

A completely different image is seen after fractional ablation laser exposure. The trauma caused by this laser breaks the blood vessels and the blood cells, along with the serum, are released into the surrounding tissue. The full-right mechanism of skin regeneration - pha alteration begins - aseptic inflammation develops. Platelets released by damaged vessels play an important role in activating blood clotting and releasing chemotoxic factors, which, in turn, attract other platelets, leukocytes, and fibroblasts. Leukocytes, in particular neutrophils, participate in the cleaning of destroyed tissue, removing fragments of necrotic tissue, which are partially destroyed by phagocyitis, and partially exit to the surface of the skin in the form of microscopic debris consisting of substrates of epidermal tissue. and dermal and melanin: microepidermal necrotic debris (LESS).

The proliferative phase begins in approximately 5 days. During this period, neutrophils are replaced by monocytes. Monocytes, keratinocytes and fibroblasts continue to influence growth factors and at the same time are under their inverse influence. Keratinocytes: Stimulate the growth of the epidermis and the release of growth factors necessary to stimulate the production of collagen by fibroblasts. In this phase, new blood vessels are formed and the extracellular matrix is ​​intensely formed.

The last phase of reconstructive healing after fractional laser exposure lasts for several months.

By the fifth day after injury, the fibronectin matrix "snaps" along the axis along which fibroblasts align and along which collagen will build. An important role in the formation of this matrix is ​​played by transforming growth factor β (TGF-β is a strong chemotoxic agent for fibroblasts), as well as other growth factors. The main form of collagen in the initial phase of wound healing is type III collagen (this type of collagen is found in the upper layer of the dermis, just below the basal layer of the epidermis). The longer the breakdown phase, the more type III collagen will be produced, but in any case, its amount peaks 5-7 days after damage. Type III collagen is gradually replaced by collagen over about a year Type I, which strengthens the skin. Blood circulation gradually normalizes, the skin becomes smoother and takes on a natural color.

Comparative analysis of laser skin reshaping methods

Summarizing the above, here is a diagram showing the relationship between the effectiveness and safety of laser skin reshaping techniques.

Advantages of fractional pathway rejuvenation methods. Advantages of fractional methods used in clinical practice include:

• controlled for minimal skin damage. Histological studies carried out after the procedure show an increase in the number of papillae in the dermis, which characterizes the changes that have occurred in the skin as productive regeneration;
• its effective rejuvenation: the skin becomes thicker, significantly increases (more than 400% (! )) the production of collagen and elastin;
• short healing time: on average 3 days after FF and 7-14 days after PA;
• minimal risk of hyperpigmentation;
• the possibility of performing the procedure in patients with thin skin;
• the ability to have a healing effect on any part of the body;
• the possibility of using light types of anesthesia: with fractional photothermolysis, only local anesthesia is used; For fractional ablation, a combination of conduction and infiltration anesthesia is required;
• disappearance of telangiectasias (due to the fact that there is a rupture of blood vessels in so many places that their restoration is impossible).

Main indications for fractional treatments

Indications for fractional photothermolysis:

• increased skin density in the early stages of aging. The FF procedure is relatively easy and can be administered without fear. The therapeutic effect can be exerted on the neck, décolleté, arms, abdomen, thighs, mammary glands;
• photoaging of the skin;
• hyperpigmentation, melasma;
• hypertrophic scars;
• striae.

Indications for fractional ablation:

• wrinkles of varying severity, from fine lines to very pronounced (furrow-like);
• age-related loss of elasticity and firmness of the skin;
• excess skin on the eyelids, neck, face (as an alternative to plastic surgery);
• uneven skin texture;
• pronounced photoaging of the skin;
• acne scars;
• scar deformity of the skin after injuries, operations;
• hyperpigmentation: melasma, lentiginosis, mottled pigmentation, etc.
• vascular dyschromia;
• stretch marks on the skin;
• actinic keratosis.

In conclusion, a few words about the prospects for the use of laser technologies in aesthetic medicine. We must pay tribute to the manufacturers who began to pay more attention to the safety of medical procedures using lasers. Technology constantly evolving. However, the safety of the method was often sacrificed to increase its effectiveness. Or vice versa. A compromise was found in a new principle of delivering laser radiation to tissues. It should be noted that the typeslasers remained the same: erbium, carbon dioxide, neodymium. This suggests that:

• First of all, laser skin reshaping is recognized as the most effective today;
• secondly, the breadth of coverage of aesthetic and dermatological problems solved by these methods is extremely large, from skin rejuvenation to the treatment of congenital and acquired skin pathologies;
• Third, with theWith the advent of fractionated technologies, the safety and efficacy of treatment have become predictable.