Fractional laser technology: a trade-off between efficiency and safety

Today, the arsenal of modern dermatocosmetology has a fairly wide range of methods for the elimination of various aesthetic imperfections of the skin - chemical peels, mechanical dermabrasion, laser restoration, microdermabrasion, contouring. and others, nevertheless, new trends and technologies in the beauty industry are constantly evolving and improving

This trend is particularly characteristic of hardware methods, mainly laser medicine. There is an impressive period for the use of lasers first in dermatology and then in cosmetology. Even more than 25 years have passed since one of the latest emerging laser treatments - selective photothermolysis. Pioneers in the field, Americans RR Anderson and JA Parrish, had determined the fate of fractional lasers in medicine, making them indispensable in the treatment of such aesthetics. skin imperfections such as capillary hemangiomas. Port stains, hypertrichosis, tattoos, rosacea, pigmentation disorders, aging, wrinkles, etc.

Modern skin remodeling techniques

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

Plastic surgery can restore the shape of the face by removing excess skin. However, at the same time, the skin is still altered by time (aging) or external factors (aging). Also important is what 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 its actual regeneration?

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, provoking fibrosis, which further causes its tightness and compaction.

There are currently three main types of skin modification effects used in dermatocosmetology, including:

• chemical stimulation - chemical peels with acids (trichloroacetic acid, glycolic acid, etc. );
• mechanical stimulation - mechanical dermabrasion, microdermabrasion, mesotherapy, fillers, needle subcision;
• thermal stimulation - laser ablation, thermolifting using lasers and broadband light sources, radiofrequency boosting, fractional techniques.

Chemical stimulation

Historically, acid peeling (peeling) was the first method of skin rejuvenation. The principle of peeling is the partial (as well as superficial peeling) or almost complete (like medium and deep peeling) destruction of the epidermis, damaging fibroblasts and dermal structures. This damage activates the inflammatory response (the stronger the greater the amount of destruction itself), which leads to the formation of additional collagen in the skin.

However, the peel must be sacrificed to the epidermis to achieve the desired result. Experiments with burns have misled many, believed to be "proving" that the epidermis is a self-healing organ that quickly recovers from damaged area. In this regard, peels became increasingly aggressive against the epidermis (for example, deep phenol peeling) for some time, until the accumulated problems eventually led professionals to realize this method of malignancy, which eventually leads to skin thinning.

Deep peelers ignored the new issues. Their essence was that due to the destruction of the dermal papillary and the weakening of the diet, the epidermis becomes thinner, and compared to the Indian layer, the number of cells is significantly reduced from what was before peeling. A severe decrease in corneal barrier function leads to a decrease in skin hydration. (Therefore, almost all patients develop severe dry skin for a long time after deep peeling). At the same time, the introduction in practice of lighter peels (using trichloroacetic acid and fruit acids) did not live up to expectations of effective skin tightening.

Mechanical stimulation

Dermabrasion using rotating devices (at speed v; rotator rotation up to 100, 000 rpm) deserves special attention for stimulation methods that cause accidental skin changes. Modern Schumann-Schreus devices (Germany)

are currently in use

The method can only be used in a surgical hospital, as the procedure requires anesthesia, postoperative treatment of the wound surface, special eye and mouth toilet, and devices to feed patients (due to the fact that severe postoperative edema occurring 2-3 days after the procedure is difficulteye and mouth opening).

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

• persistent postoperative hyperemia;
• Appearance of depigmentation zones due to melanocyte destruction when the cutter penetrates the basement membrane;
• wound surface infection;
• scars (if the cutter is too deep into the skin)

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

Thermal stimulation

Ablative Transformation <strongx

Since the late 1980s, a laser has been used to regenerate the skin by removing layers by layer (ablation) [4]. Careful, low-traumatic removal of the skin's surface using a carbon dioxide laser stimulates the synthesis of collagen itself, the amount of which increases several times after the procedure. Then rearrange it gradually.

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

att. 1. Traditional laser skin regeneration scheme (laser dermabrasion)

However, the CO2 laser also causes many complications. In addition, additional studies have shown that such a deep effect on the dermis stimulates the formation of fibrous tissue more than it promotes new, normal synthesis. oriented collagen [5]. Developed fibrosis can make the skin unnaturally pale. After treatment, the synthesized collagen is absorbed after a few years in the same way as any collagen formed at the scar site. As a result of thinning of the epidermis, which is 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 function of the stratum corneum, the hydration level of the skin decreases and it looks atrophic.

Erbium-aluminum-yttrium grenade-erbium lasers appeared a little later. The advantages of an erbium laser such as a shallower heat 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 tissue carbonation, as well as relative cheapness (compared to carbon dioxide lasers) have attracted many professionals. worldwide attention.

Despite the experience gained with these two types of installation, there is a perception among professionals that CO2 lasers are more efficient [6]. Despite the negative effects of carbon dioxide laser dermabrasion described above, this method remains indispensable for correcting pimple scars. In addition, it can be considered as an alternative to surgical skin tightening - of all its modification methods, only the CO2 laser effect can actually cause a pronounced collagen contraction with a visible clinical lifting effect.

The problem with all of the methods described above is that they often "sacrifice", that is, significantly damage the epidermis. To rejuvenate the skin and really look young, you need a flawless epidermis with naturally occurring papillae, good hydration, normal skin tone and elasticity. The epidermis is a very complex, highly specialized organ with a thickness of up to 200 microns, and it is our only remedy against the negative effects of environmental factors. So no matter what we do to rejuvenate the skin, we need to make sure that its normal architecture is never damaged.

This concept has led to the emergence of non-ablative skin remodeling technologies.

Abnormal transformation

The most common non-ablative devices for skin reconstruction are neodymium (Nd-YAG) and diode lasers, as well as broadband light sources (IPL). Their principle of operation - selective photothermolysis - consists in heating and destroying structures that contain sufficient amounts of melanin or oxyhemoglobin. The skin has an accumulation of melanocytes (lentigo, melasma) and micronuclei (telangiectasia), respectively. The radiated wavelengths used in non-ablative lasers correspond to the peaks in the absorption spectrum of oxyhemoglobin or melanin. The procedure for treatment with non-blasting lasers and IPL is quite safe, the rehabilitation period is minimal, however, such treatment eliminates only pigmentary and vascular cosmetic defects. In this case, there is some thickening of the skin, but the effect obtained is short-lived.

Fractional skin modification techniques

The constant search for new, highly effective and at the same time safe methods of skin rejuvenation has led to the emergence of a revolutionary technology - the partial delivery of laser radiation. The proposed skin rejuvenation method is specially designed to overcome some of the above difficulties. Unlike "conventional" ablation and non-ablation laser methods, which are designed to achieve even thermal thermal damage to the skin at a given depth, fractional methods allow selective microscopic thermal damage in the form of many altered columns and leave unaffected areas around these micro-wounds. The industry currently produces two types of fractional lasers: anti-bleach and ablative.

The first uses an erbium-doped optical fiber that emits radiation at a wavelength of 1550 nm. The fractional laser forms thousands and tens of thousands of micro-disorders in the skin in the form of columns - microthermal treatment zones (MLZs) with a diameter of 70-150. mk depth up to 1359 mcm

As a result, about 15-35 skins photocoagulate at the treated area. The laser chromophore is water. Coagulation occurs mainly in the epidermis and lower layers of the dermis. The strategy remains intact as it contains a relatively small amount of water and significantly reduces the risk of infection. Epidermal regeneration is rapid due to the small amount of damage and the short migration distance of keratinocytes. The healing period is accompanied by edema and hyperemia, followed by desquamation, which appears in 5. -7. day. The patient practically does not lose social activity.

This technology - fractional photothermolysis (FF) - is a very efficient method of transforming non-bleached fractionated skin. To achieve the desired effect, the course of treatment is determined. It is recommended to perform 3 to 6 procedures at 4-6 week intervals, depending on the clinical situation. As with any other method of immature skin regeneration, the final result can only be seen 4-8 months after the procedure (cumulative effect).

Fractional ablation (FA or fractional deep dermal ablation - FDDA) method is used for cases where more aggressive effects on the skin are required - for scar correction, removal of deep wrinkles and skin remnants. the principle of radiation supply. Unlike traditional CO2 lasers, which remove the entire skin surface, FA units form a huge number of microablative zones (MALs) up to 300 µm in diameter, with an evaporation depth of 350 to 1800 µm (Fig. 2).

During this procedure, the laser radiation penetrates the deep layers of the skin and destroys the top layer of the epidermis. In terms of efficiency, ablation fractional laser restoration can be compared to plastic surgery, that is, how deep the laser beam regenerates.

att. 2. The principle of operation of the ablation fractional laser: formation of microablative zones - MAZ (a); DEPENDENCE of LOW formation depth on laser radiation power (b)

Like FF, 15 to 35% of the skin at the treated area is exposed (up to 70% in some cases). Recovery after FA procedure is faster than after layer ablation. This is due to the fact that a significant part of the epidermis and stratum corneum remain intact. Skin bleeding is observed for some time immediately after the procedure, but soon stops (Fig. 3 a, b).

att. 3. Gradual regeneration of the skin after the fractional ablation procedure: view immediately after treatment (a); every other day (b); after 5 days (c); 14 days (d) after one procedure

A lot of micronutrients appear in the dermis, causing a complex cascade of changes that leads to the production of new collagen. After the bleeding has stopped, the serous fluid that remains on the surface of the skin must be removed. Its release is observed within 48 hours after the procedure until complete epithelialization of the microablastic zones. During this period, the patient uses special external wound healing products. Peeling and swelling usually increase from 3-4 days (Fig. 3 c). By day 7, these effects gradually disappear and erythema remains the only noticeable side effect (Fig. 3d). The duration of erythema depends on the laser exposure parameters and the signs of skin vascularization. According to the author's observations, erythema lasts no more than 3 months.

Loss of a patient's social activity after an FA procedure lasts from 5 to 10 days.

Careful skin care is required to avoid scarring and post-inflammatory pigmentation. Make-up can be used from 4-5 days. A prerequisite for a good result is at least 3 months after a tanning cosmetic procedure 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 cutaneous IV-V phototypes. Such hyperpigmentation is transient and may last from 1 week to 3 months, depending on the depth of treatment and the area to be treated. For its prevention 1-2 weeks before the procedure and for a further 2 weeks after it are prescribed external funds based on hydroquinone (4%) and tretinoin (0. 1%). The main effects on the facial skin after the FA procedure are as follows: pronounced tightening and reduction of excess skin, smoothing of the surface, wrinkled skin, as well as skin affected by acne scars, reduction of dishromy, porosity.

This method was also tested by the author and his colleagues for removing skin stretch marks. As clinical studies have shown, this method has proven to be highly effective in the prevention of almost all types of stretch marks, both acquired during puberty and postpartum. It was noted that the healing processes on the body skin are different than on the facial skin.

Skin Transformation Mechanism Using Fractional Lasers

Let's look at the mechanisms of skin transformation using fractional lasers.

Aseptic inflammation develops in the area of ​​laser-formed micro-wounds. The more aggressive the laser effect, the more pronounced the inflammatory response, which actually stimulates the post-traumatic release of growth factors and infiltration of damaged tissue with fibroblasts. The next reaction is automatically accompanied by a break in cell activity, which inevitably leads to fibroblasts starting to produce more collagen and elastin. The skin remodeling process involves three classic regeneration phases:

• Phase I - changes (inflammation of the tissues). Starts immediately after damage;
• Phase II - proliferation (tissue formation). Begins 3-5 days after injury and lasts for about 8 weeks;
• Phase III - Tissue Transformation. Lasts from 8 weeks to 12 months.

It should be noted that all three phases of skin remodeling are observed after both fractional photothermolysis and fractional ablation. But in the first case, the destructive effect of the laser is moderately aggressive, resulting in an inflammatory cascade change that is never too wild.

A completely different image is observed after fractional ablation laser exposure. The trauma caused by this laser ruptures the blood vessels, and the blood cells, along with the serum, are released into the surrounding tissues. The mechanism of complete skin regeneration - phase transformation begins - aseptic inflammation develops. Platelets released from damaged vessels play an important role in activating blood clotting and releasing chemical toxic factors, which in turn bind other platelets, leukocytes and fibroblasts. Leukocytes, especially neutrophils, participate in the cleansing of destroyed tissues by removing fragments of necrotic tissue, which are partially destroyed by phagocytes, and partially on the skin surface in the form of microscopic debris consisting of epidermal and dermal tissue substrates and melanin-microepidermal necrotic residues (MENO).

The proliferation phase begins in approximately 5 days. During this period, neutrophils are replaced by monocytes. Monocytes, keratinocytes and fibroblasts continue to affect growth factors and at the same time are reversed. Keratinocytes stimulate epidermal growth and the release of growth factors needed to stimulate collagen production by fibroblasts. During this phase, new blood vessels form and the extracellular matrix is ​​intensively formed.

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

By day 5 post-injury, the fibronectin matrix "fits" along the axis along which the fibroblasts are arranged and along which collagen will be formed. Modification of growth factor β (TGF-β is a potent chemically toxic agent for fibroblasts) as well as other growth factors play an important role in the formation of this matrix. The main form of collagen in the early phase of wound healing is type III collagen (this type of collagen is located in the upper layer of the dermis, just below the base layer of the epidermis). The longer the transformation phase, the more type III collagen will be produced, but in any case the maximum amount will increase from 5 to 7 days after damage. Over a period of about a year, collagen III is gradually replaced by type I collagen, which strengthens the skin's resilience. Blood circulation is gradually normalized, the skin becomes smoother and acquires a natural color.

Comparative analysis of skin reconstruction laser methods

In summary, here is a diagram showing the relationship between the effectiveness and safety of skin laser modification techniques.

Partial advantages of track restoration methods. The advantages of fractional methods used in clinical practice are:

• controlled minimal skin damage. Histological examinations performed after the procedure show an increased number of papillae in the dermis, which characterizes the changes that have taken place in the skin as a productive regeneration;
• its effective regeneration: the skin becomes thicker, the production of collagen and elastin increases significantly (more than 400% (! ));
• short healing time: average 3 days after FF and 7-14 days after PA;
• minimal risk of hyperpigmentation;
• option to perform the procedure on patients with thin skin;
• Ability to achieve a healing effect on any part of the body;
• possibility to use mild forms of anesthesia: with fractional photothermolysis only local anesthesia is used; fractional ablation requires a combination of conduction and infiltration anesthesia;
• Disappearance of telangiectasias (due to the rupture of blood vessels in so many places that it is not possible to restore them).

Main indications for fractional treatment

Fractional photothermolysis indications:

• increase in skin density in the early stages of aging. The FF procedure is relatively easy and can be administered without fear. Therapeutic effect may be on the neck, décolleté, arms, abdomen, thighs, mammary glands;
• skin aging;
• hyperpigmentation, melasma;
• hypertrophic scars;
• stretch marks.

Fractional ablation indications:

• Wrinkles of varying severity - from fine lines to pronounced (furrow-shaped);
• age-related loss of skin elasticity and firmness;
• Excessive eyelid, neck, facial skin (as an alternative to plastic surgery);
• uneven skin texture;
• severe skin aging;
• pimple scars;
• skin cicatricial deformity after injuries, surgeries;
• hyperpigmentation: melasma, lentiginosis, mottled pigmentation, etc.
• vascular dishromy;
• skin stretch marks;
• actinic keratosis.

Finally, a few words about the prospects of using laser technology 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 was constantly evolving. However, quite often the security of the method was sacrificed to increase its effectiveness. Or otherwise. A compromise was found on a new principle - the transfer of laser radiation to tissues. It should be noted that the type lasers remained unchanged: erbium, carbon dioxide, neodymium. This suggests that:

• , first of all, laser skin rejuvenation is considered to be the most effective today;
• Secondly, the range of aesthetic and dermatological problems solved by these methods is enormous, from skin rejuvenation to the treatment of congenital and acquired skin pathologies;
• Third, with the advent of fractional technologies, the safety and effectiveness of treatment has become more predictable.