Fractional laser technology: a compromise between efficiency and safety

26 August 2020

Today, in the arsenal of modern dermatocosmetology there is a very wide range of methods for correcting various aesthetic skin imperfections - chemical peels, mechanical dermabrasion, laser reappearance, microdermabrasion, plastic contour and others. However, new guidelines and technologies in the beauty industry are constantly evolving and improving.

This trend is particularly typical of hardware methods, mainly laser medicine. The use of lasers, first in dermatology, and then in cosmetology, has an impressive period. Even more than 25 years have passed since the introduction of one of the newest methods of laser treatment - selective photothermolysis. The pioneers of this area, the Americans RR Anderson and JA Parrish, predetermined the fate of refractive lasers in medicine, making them indispensable in treating such an aesthetic skin imperfections as capillary hemangiomas. Port wine spots, hypertrichosis, tattoos, rosacea, pigmentation disorders, photography, wrinkles, etc.

Modern skin remodeling techniques

We live in a time when more people are living in old age than ever before. And given that many of them continue to live active lives, one of the most important problems in aesthetic medicine is the fight against skin aging.

Plastic surgery is able to renew the shape of the face by removing excess skin. However, at the same time, the skin still remains altered by time (aging in relation to age) or external factors (photography). It is also important that most patients want to look younger without surgery.

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

All 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, provoking fibrosis, which further leads to its tension and compactness.

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

chemical stimulation - chemical peels with acids (trichloroacetic, glycolic, etc. );
mechanical stimulation - mechanical dermabrasion, microdermabrasion, mesotherapy, fillers, needle subdivision;
thermal stimulation - laser ablation, thermolysis using lasers and broadband light sources, radiofrequency ablation, fractional methods.

Chemical stimulation

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

However, to achieve the desired result, the peel must sacrifice the epidermis. Burning experiments have deceived many, ostensibly "proving" that the epidermis is a self-renewing organ that heals quickly on damaged areas. phenolic), to the end the accumulated problems made specialists understand the evil of this method that eventually leads to thinning of the skin.

Deep shell advocates ignored the problems that emerged. Their essence was that due to the destruction of the papillae of the dermis and the weakening of food, the epidermis becomes thinner, and the number of cells in the prickly layer is significantly reduced compared to what it was before peeling. A decrease in the barrier layer barrier function leads to a decrease in skin hydration. (Therefore, almost all patients after deep skin for a long time experience severe dryness of the skin) At the same time, the introduction into practice lighter peels (using trichloroacetic and fruit acids) did not meet their hopes for tighteningeffective skin.

Mechanical stimulation

Of the methods of mechanical stimulation of inclusive changes in the skin, dermabrasion with the use of rotating devices (at a speed of v; rotation of openers up to 100, 000 rpm) deserves special attention. Currently, modern Schumann-Schreus equipment (Germany)

are used

The method can only be used in a surgical hospital, as the procedure requires anesthetic assistance, postoperative treatment of the wound surface, a special toilet for the eyes and mouth, as well as equipment for feeding patients (due to the fact that edemapronounced after surgery 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 hyperemia after surgery;
appearance of depigmentation areas due to melanocyte destruction when the incision penetrates the basement membrane;
infection on the wound surface;
(if the presser is deeply embedded in the skin)

All of the above has defined 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 layer-by-layer tissue (ablation) [4]. Careful and low traumatic removal of the surface layer of the skin using a carbon dioxide laser stimulates the synthesis of its own collagen in it, the amount of which increases several times after the procedure. It is then gradually reorganized.

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

laser dermabrasion

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

However, the CO2 laser also causes a large number of complications. Moreover, further studies have shown that such a profound effect on the dermis stimulates the formation of fibrous tissue to a greater extent than contributes to the synthesis of a new, normal-oriented collagen [5]. Developed fibrosis can make the skin look unnaturally pale. Collagen synthesized after treatment is restored after a few years, like any collagen formed at the scar site. As a result of rare epidermis caused by atrophy of the papillary layer of the dermis, fine wrinkles begin to appear on the skin. Due to the weakening of the barrier layer function of the layer, the skin hydration level decreases, and it looks atrophic.

The erbium-aluminum-ytrium garnet-erbium laser appeared somewhat later. Advantages of such an erbium laser as a shallow thermal penetration depth (erbium lasers penetrate to a depth of 30 μm, CO2 lasers - up to 150 μm) and (as a result) lower risk of burns and carbonization oftissue, as well as relative freedom (compared to carbon dioxide lasers), attracted the attention of many specialists around the world.

However, as experience working with these two types of installations has accumulated, the opinion has been 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 correcting acne scars. In addition, it can be considered as an alternative to surgical skin tightening - of all the methods of its remodeling, only exposure to a CO2 laser can actually cause a pronounced emphasis on collagen shrinkage with noticeably clinically enhancing effect.

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

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

Non ablative remodeling

The most common devices for non-ablative skin remodeling are neodymium (Nd-YAG) and diode lasers, as well as broadband (IPL) light sources. The principle of their action - selective photothermolism - consists in heating and destroying structures, which contain a sufficient amount of melanin or oxyhemoglobin. In the skin, these are, respectively, accumulations of melanocytes (lentigo, melasma) and microvessels (telangiectasia). The emitted wavelengths used in non-ablative lasers correspond to the maximum absorption spectrum of oxyhemoglobin or melanin. The procedure of non-ablative laser treatment and IPL is quite safe, the rehabilitation period is minimal, however, such treatment eliminates only pigmentary and cosmetic vascular defects. In this case, there is a certain thickening of the skin, but the effect obtained is short-lived.

Fractional skin remodeling techniques

The constant search for new highly effective and at the same time safe methods for skin rejuvenation has led to the emergence of a revolutionary technology - the partial delivery of laser radiation. The proposed method of skin rejuvenation is specifically designed to overcome some of the above difficulties. Unlike "conventional" and non-ablative laser ablation methods, which are designed to achieve uniform skin damage at a specific depth, fractional methods allow to achieve its selective thermal microscopic damage in the form of multiple altered columns andleave unexplained areas around these wounds. Currently, the industry produces two types of fractional lasers: non ablatived and ablative.

The first uses an erbium-emitted optical fiber that generates radiation at a wavelength of 1550 nm. The fractional laser forms on the skin thousands and tens of thousands of microdermages in the form of columns - microthermal treatment areas (MLZ) - with a diameter of 70-150mk depth up to 1359 mcm

As a result, about 15-35 skins are photocagulated in the treated area. The chromophore for the laser is water. 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. The epidermis heals quickly due to the low volume of lesions and the short migration distance of keratinocytes. The healing period is accompanied by moderate edema and hyperemia, followed by desquamation, appears on day 5-7. The patient practically does not lose social activity.

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

laser action

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

Fractional ablation method combines the advantages of a CO2 laser and the fractional principle of laser radiation scattering. Unlike traditional CO2 lasers, which remove the entire surface of the skin layer by layer, FA units form a large number of microablatives. areas (MAL) up to 300 μm in diameter at an evaporation depth of 350 to 1800 μm (Fig. 2).

Thus, during this procedure, laser radiation, penetrating into the deeper layers of the skin, destroys the upper layer of the epidermis. In terms of efficiency, abstract fraction laser rejuvenation can be compared to plastic surgery, this is how deep the laser beam reappears.

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

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

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

$stages of skin restoration after fractional fractionation procedure$

Numerous microbreds appear in the dermis, which cause a complex cascade of changes leading to the production of new collagen. After stopping the bleeding, 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 wound healing agents. It usually starts from 3-4 days and the swelling increases (Fig. 3 c). By day 7, these phenomena gradually fade, and erythema remains the only apparent side effect (Fig. 3D). The duration of erythema depends on the parameters of laser exposure and the features of skin vascularization. According to the author's observations, erythema lasts no more than 3 months.

Loss of social activity by the patient after the FA procedure lasts from 5 to 10 days.

To prevent pain and the appearance of pigmentation after inflammation, it is necessary to take good care of the skin. Decorative cosmetics can be used from 4-5 days. A prerequisite for a good result is the use of it at least 3 months after the procedure of sun cosmetics with a high degree of protection (SPF at least 50). The risk of pigmentation after inflammation occurs in 20% of patients and is generally higher in skin patientsPhototypes IV-V. Such hyperpigmentation is temporary 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 it, external agents based on hydroquinone (4%) and tretinoin (0, 1%) are prescribed. The main effects on the facial skin after the FA procedure are as follows: pronounced tightening and reduction of excess skin, leveling of wrinkled skin surface, as well as skin affected by acne scars, reduction of dyschromia, porosity.

This method was tested by the author and his colleagues also for removing stretch marks on the skin. As shown by clinical studies, the method has demonstrated high efficiency in eliminating almost all types of stretch marks, both acquired during puberty and postpartum. It has been observed that healing processes on the skin of the body are different than on the skin of the face.

Skin remodeling mechanism when using fractional laser

Let's examine the mechanisms of skin remodeling when using fractional lasers.

After laser exposure, aseptic inflammation develops in the area of the formed wounds. The more aggressive the laser exposure, the more pronounced is the inflammatory response, which, in fact, stimulates the release after traumatic growth factors and the infiltration of fibroblast-damaged tissue. The next reaction is automatically accompanied by an explosion of cellular activity, which inevitably leads to the fact that fibroblasts begin to produce more collagen and elastin. The skin remodeling process involves three classic stages of regeneration:

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

It should be noted that all three stages 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 inflammation change is never too wild.

A completely different view is observed after fractional fraction laser exposure. The trauma caused by this laser destroys the blood vessels, and the blood cells, along with the serum, are released into the surrounding tissue. The full mechanism of skin regeneration - the pha change begins - aseptic inflammation develops. Platelets released by damaged vessels play an important role in activating blood clotting and releasing chemotoxic factors that, in turn, attract other platelets, leukocytes, and fibroblasts. Leukocytes, in particular neutrophils, participate in the cleansing of destroyed tissue, the removal of fragments of necrotic tissue, which are partially destroyed by phagocytes, and partially emerge on the surface of the skin in the form of microscopic debris composed of dermal and dermal tissue substratesand melanin - microepidermal necrotic debris (MENO).

The proliferative phase begins in about 5 days. During this period, neutrophils are replaced by monocytes. Monocytes, keratinocytes and fibroblasts continue to influence growth factors and at the same time be under their opposite influence. Keratinocytes stimulate the growth of the epidermis and the release of growth factors necessary to stimulate collagen production by fibroblasts. At this stage, new blood vessels are formed and the extracellular matrix is intensively formed.

The final, reconstructive, healing phase after laser fraction exposure lasts several months.

By day 5 after injury, the fibronectin matrix "fits" along the axis along which the fibroblasts are lined up and along which collagen will be built. An important role in the formation of this matrix is played by converting 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 early stage of wound healing is type III collagen (this type of collagen is located in the upper layer of the dermis, just below the basal layer of the epidermis). The longer the change phase, the more type III collagen will be produced, but in any case, its amount increases to a maximum of 5 to 7 days after injury. Type III collagen is gradually replaced by collagen over about a year Type I, which strengthens the skin. Blood circulation is gradually normalized, the skin becomes softer and acquires a natural color.

Comparative analysis of laser skin remodeling methods

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

Advantages of partial renewal methods. The advantages of fractional methods used in clinical practice include:

controlled minimal skin damage. Histological studies performed 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, it significantly (more than 400% (! )) increases the production of collagen and elastin;
Short recovery time: 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;
ability to have a healing effect on any part of the body;
possibility of using light types of anesthesia: with fractional photothermolysis, only local application anesthesia is used; for fractional ablation, a combination of conduction and penetration anesthesia is required;
disappearance of telangjectasias (due to the fact that there is a rupture of blood vessels in so many places that their restoration is impossible).

Main indications for fraction treatments

Indications for fractional photothermolysis:

increase in 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;
skin photography;
hyperpigmentation, melasma;
hypertrophic wounds;
alignment marks.

Indications for fractional inflation:

wrinkles of varying severity - from fine lines to strong accents (in the form of grooves);
age-related loss of skin elasticity and firmness;
uneven skin quality;
accentuated skin photography;
acne scars;
scarring of the skin after injuries, surgeries;
hyperpigmentation: melasma, lentiginosis, spot pigmentation, etc.
vascular dyschromia;
skin stretch marks;
actinic keratosis.

In conclusion, a few words about the prospects of using laser technologies in aesthetic medicine. We must pay tribute to the manufacturers that they began to pay more attention to the safety of medical procedures using lasers. Technology constantly evolved. However, quite often the safety of the method was sacrificed in order 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 lasers remained the same: erbium, carbon dioxide, neodymium. This suggests that:

First, laser skin reshaping is recognized as the most effective today;
second, 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;