Ablative laser technologies in scar correction

Yana Goncharova, M.D. , Professor of the Department of Dermatovenereology and Cosmetology of Donetsk National Medical University, Director of the Lege Artis Aesthetic Medicine Clinic (Donetsk), Consultant of the Queen Medical Clinic (Doha, Qatar )

Facts about scar tissue

Scar changes in the skin are connective tissue growths that replace defects that arise due to the destruction of the dermis, as well as underlying tissues. In essence, a scar is a localized focus of sclerosis that has replaced a wound defect or focus of necrosis.

From the point of view of etiology and pathogenesis, the following cicatricial or sclerotic changes are distinguished:

• as an outcome of inflammation due to an infectious process - viral, bacterial, parasitic (for example, scars after chickenpox, inflammation of the pilosebaceous follicle, etc.);
• as an outcome of systemic or localized disorganization of connective tissue in systemic diseases (discoid lupus erythematosus, scleroderma, etc.);
• post-traumatic (after surgical interventions, spontaneous injuries, etc.).

In young scar (connective) tissue, active proliferation of fibroblasts is observed, which intensively synthesize collagen, which leads to the maturation of fibrous scar tissue. From the point of view of the reversibility of sclerosis, all sclerotic and cicatricial processes can be divided into:

• labile (involving), that is, easily reversible;
• stable, partially reversible over time or under the influence of treatment;
• irreversible, progressive.

Clinically, the scar lacks skin appendages (hair follicles, sebaceous and sweat glands, as well as blood vessels and elastic fibers). In size and shape they correspond to the skin defect being replaced.

It is generally accepted to divide scars into flat (lying at the same level with the surrounding normal skin), hypertrophic (rising above the surface of the surrounding skin) and atrophic (with a thinned surface, lying below the level of the surrounding normal skin).

Basic correction methods

In the practice of a dermatocosmetologist, scar changes most often occur after acne, acne of any other origin, as well as scars resulting from wound defects, injuries and surgical interventions.

If we do not take into account the problem of treating fresh hypertrophic and keloid scars, the principle of treating the rest comes down to various types of peelings and abrasions. These include medium chemical peeling with trichloroacetic acid 25–30%, microcrystalline, mechanical and laser dermabrasion. Often, a combination of several methods is used to increase efficiency.

There are also patented scar treatment combinations. Thus, Whang and Lee [1] proposed a step-by-step approach to the treatment of atrophic scars after acne and chickenpox on the face, including 1-3 procedures of focal median chemical peeling with trichloroacetic acid 25%, followed by microsurgical correction, laser CO2 abrasion and the final stage - mechanical dermabrasion of the skin. And Fulton and Silverton [2] proposed to conduct a course of treatment with retinoic acid 0.05% in combination with 3–4 passages of chemical peeling with trichloroacetic acid 25% and/or Jessner’s solution before laser CO2 abrasion.

In the process of abrasive procedures (resurfacing), several layers of the epidermis are purposefully removed with the formation of a wound surface, often of a significant area. Moreover, the success and effectiveness of the procedure largely depend on the correct management of the postoperative period. The very course of the postoperative period is determined by the method of dermabrasion, which can be mechanical, laser or microcrystalline.

More about lasers

Lasers for cosmetic skin resurfacing have been actively used since 1989. These are so-called ablative lasers, which include laser systems that generate radiation in the infrared range. For such systems, the water content of the fabric is essential, since infrared radiation is highly absorbed by water. Since the skin is a tissue with a high water content, infrared radiation has a relatively shallow penetration depth due to its strong absorption by the upper layers of the epidermis.

For laser ablation, laser systems such as a carbon dioxide CO2 laser operating in the mid-infrared (10.6 µm) range and an erbium (Erbium:YAG) laser operating in the near (2.94 µm) infrared range are used. The penetration depth of the CO2 laser is 100 microns, and that of the erbium laser is 10 microns.

The listed laser systems are pulsed, that is, they generate high-density power over a short period of time. A powerful pulse of radiation heats an area of tissue to a temperature higher than the boiling point of water. In this case, it is vaporized, during which the remaining tissue is removed with water vapor. Evaporation (ablation) of the surface layer of the epidermis gives a polishing effect.

Laser dermabrasion of atrophic post-acne scars on the face is currently the method of choice and gives the best results when the procedure is carried out within the first three years after scar formation. Both zonal treatment and full face abrasion are acceptable, which, according to some data, improves the appearance of scars by 50–75%.

However, the laser effect is not limited to the polishing effect alone: the CO2 laser radiation indirectly stimulates the process of neocollagen formation, which is observed from the 6th month after the procedure and continues for 18 months.

From the point of view of the pathophysiology of the process, CO2 laser resurfacing is a superficial thermal burn of the second degree with preservation of skin appendages. From the 1st to the 3rd day after the procedure, an acute alteration phase is observed, sometimes characterized by very pronounced swelling, which appears a few hours after the manipulation and can last from 24 to 72 hours. In some cases, swelling can persist for up to six days. The exudative phase increases gradually from the 8th to the 10th day. Subjectively, painful sensations of varying severity are noted, having the nature of a sunburn. For the purpose of pain relief during this period, non-steroidal anti-inflammatory drugs of moderate severity (paracetamol) are used. From days 4 to 7–10, the re-epithelialization phase is observed .

Side effects of lasers for scar correction

When performing CO2 laser resurfacing, there is a risk of unwanted effects, the most common of which are erythema and hyperpigmentation . According to American experts, when combining laser resurfacing and chemical peeling, the risk of hyperpigmentation and erythema is 40 and 32%, respectively.

Erythema after laser resurfacing lasts up to three months. Longer erythema is considered a mild complication. Persistent erythema is observed later throughout the year, and its outcome may be erythrocouperosis.

Hyperpigmentation, depending on the degree of its severity, is regarded as a complication of moderate to severe severity. Transient hyperpigmentation (primarily in the periorbital zone) is a fairly common phenomenon (30% of cases), especially in patients with skin phototype III according to Fitzpatrick.

The search for effective laser resurfacing methods with the lowest risk of complications resulted in the emergence of fractional lasers. The same ablative CO2 laser is used, but only the ablation area is not continuous, but dotted, with the formation of many microscopic zones of thermal damage surrounded by intact tissue. In the case of fractional resurfacing, regeneration occurs faster, with the formation of neocollagen in the treated areas.

DOT technology

Of particular interest is the use of DOT technology (dermal optical thermolysis), which makes it possible to regulate and individually select the power, the distance between points of influence, exposure time, as well as the shape and size of the scanning device, which creates additional ease of use. In this case, partial treatment of the impact area also occurs with alternating zones of thermal damage and zones of undamaged tissue. At the same time, the additional function SmartStack (stack), which consists in emitting a number of pulses and hitting them at the same point, adds a thermal effect to the ablative effect of the laser. The number of pulses directed to one point can be adjusted (from one to five). With each subsequent pulse, the depth of the thermal effect increases.

The use of DOT technology is of particular interest in the issue of resurfacing scar tissue, as it allows not only to partially remove scar tissue, but also to smooth out the relief of the underlying dermis due to the formation of neocollagen. However, we must keep in mind that the effect of smoothing the relief of scars is often delayed and we can see the final result no earlier than 6 months after resurfacing.

It has been shown that laser resurfacing using DOT technology makes it possible to achieve repigmentation of hypopigmented normotrophic and atrophic scars, improve the structure and smooth out the sharp border of atrophic scars, make them less deep, eliminate the bluish tint of hypertrophic scars, reduce their height and improve their texture. This method can also be used as an additional method in the combined treatment of keloid scars at the stage of their active growth and as monotherapy for the treatment of long-existing keloid scars.

First published: Les Nouvelles Esthetiques Ukraine, No. 1 (83), 2014