A scar is a trace of healed damaged skin. In other words, when the deep dermis is damaged due to surgery or trauma, the collagen in the dermis layer, which maintains skin tension, proliferates excessively, pushing out the thinned skin even after the wound is healed, leaving a scar. Therefore, even when the wound is deep and large, it is important to try to achieve early healing (within 3 weeks) as much as possible to minimize scarring.
Recently, many attempts have been made to prevent and minimize scarring through early laser treatment, and there is a lot of literature reporting excellent results. Laser treatment to minimize scarring now plays a major role in scar treatment, but there is still no clear treatment guide for this and there is some controversy about this.
In addition, in the case of scars that occur after burns, frank scars and hypertrophic scars that appear in a relatively wide area are common, and various types of scars are observed, such as bleached skin color or atrophic scars that have a thin and shiny texture unlike normal skin. It appears mixed, and is often accompanied by not only unsightly scars but also serious functional impairment due to scar contracture.
Among them, one area that has seen a lot of recent progress is laser scar treatment. Now, laser and energy-based devices have not only been applied to treat burn scars and contractures, which were difficult to treat with existing treatments, but the concept of rehabilitation treatment to improve early range of motion and function has also been introduced.
If a linear scar lies at an angle of more than 30 degrees to the skin tension line (usually in the direction of wrinkles), during plastic surgery to improve the scar, W-plasty or Z-plasty is performed to divide the scar into several segments and make it less visible. However, in this case, a bumpy skin surface occurs.
In this way, mechanical peeling is suitable for irregular scars on the skin surface, relatively shallow depressed scars caused by scratches or abrasions with fingernails, or hyperpigmented scars. However, with the introduction of the carbon dioxide laser (Ultrapulse CO2 laser), laser resurfacing began to receive attention for these indications due to its advantages of reducing bleeding and enabling more reliable depth control.
On the other hand, the application of 585nm PDL to hypertrophic scars and keloids has become active after reports that 585nm flashlamp-pumped pulsed-dye laser showed improved response in 75% of patients with hypertrophic scars.
Therefore, a 585-nm pulsed dye laser was applied to treat early red erythematous scars, and local CO2 laser skin regeneration was used to treat atrophic scars.
Of course, patients should be made to understand the limitations of scar revision, as it is not a surgery to completely remove scars, but rather a surgery to make scars less visible. In other words, the purpose is to make uneven scars flat and deep scars to be at the same level as the surrounding skin, making them similar to the surrounding skin. Since the laser itself does not perform scar revision, but rather the operator, the operator's experience and skills are considered important. However, the traditional CO2 laser minimizes thermal damage to surrounding tissues and can vaporize tissues without bleeding, clinically safely removing aged tissues by dermabrasion and delivering thermal stimulation to dermal tissues to promote regeneration of dermal tissues. It has been widely applied to various atrophic scars and resurfacing, including chickenpox, acne, trauma, and surgical scars.
However, although the ablative CO2 laser is effective in removing scars, since it peels off the entire skin, caution is needed in that the duration of edema and erythema after the procedure is long and the risk of infection and pigment discoloration is high. Additionally, CO2 laser dermabrasion is contraindicated in areas where skin appendages have been lost due to burn scars or chemical peeling scars due to reduced skin epithelialization ability.
And, if laser skin regeneration is performed 6-8 weeks after the initial damage, that is, around the time collagen remodeling occurs, scars caused by surgery and scars caused by trauma will be less different from the surrounding skin, and old scars will be reduced to some extent. But it will not respond as well as early treatment, so the concept of inducing scar minimization through early laser resurfacing was also introduced.
With the introduction of the concept of fractional photothermolysis in 2004, various fractional lasers using this emerged. Even if the epidermis and dermis of the MTZ (microthermal treatmenet zone) area are damaged, they can be epithelialized from the surrounding undamaged normal skin. It is achieved quickly and the duration of edema and erythema is reduced, which not only has a cosmetic effect on scar removal and peeling, but also increases patient satisfaction and enables a quick return to daily life.
In addition, the pinhole method, which is one of the other laser irradiation methods, is a procedure that uses a carbon dioxide gas laser to cut a fine hole (pinhole) in the dermis layer of the skin and break hard fibrous tissue. It can be relatively effectively applied to surface scars caused by burns. Fractional lasers can also be divided into non-ablative and ablative types. Based on the same theory as the pinhole method, in the case of burn scars, CO2 fractional lasers are thought to be more effective when they can penetrate thick scar tissue more deeply. Recently, rotary electric coring devices have been introduced and are being applied clinically.
In addition, pigment lasers and IPL with wavelengths of 532nm, 694nm, 755nm, and 1064nm are used to treat hyperpigmentation and dark-colored scars.
In particular, the irradiation method of fractional photothermolysis has been introduced to these pigment lasers and is used to treat post-inflammatory hyperpigmentation (PIH).
It is a picosecond laser developed for more precise treatment of pigmented lesion areas, including tattoos. The U.S. FDA first approved tattoo removal using a picosecond 755 nm alexandrite laser in 2012, and a micro-lens array (MLA) for facial wrinkles and scars. As many studies using the picosecond laser with a MLA tip have reported excellent results, in 2014 the FDA approved the 755nm picosecond alexandrite laser not only for the treatment of pigmented lesions and tattoos, but also for the treatment of scars and wrinkles.
Fractional irradiation is possible by increasing the focusing power of energy with a small beam spot, which generates laser induced optical breakdown (LIOB) in the dermis below the epidermis.
This LIOB is absorbed by melanin when irradiated with a focused beam with a near-infrared wavelength laser of sub-nanosecond pulse duration, producing a photoacoustic effect. Plasma is generated along with cavitation, which stimulates fibroblasts and promotes the production of new collagen, elastin, glucosaminoglycan such as hyaluronic acid, and glycoprotein, thereby improving scars and improving skin tone. It shows the effect of revitalization. It also has a similar effect to subcision by preserving the epidermis and has a remodeling effect on scar tissue or dermis.
In particular, the fractionated 1064nm picosecond Nd:YAG laser shows good results in improving hyperpigmented scars and depressed and contracted scars caused by burns or road abrasions. Also, additional application of a picosecond laser with MLA after fractional CO2 laser treatment can be a safe and effective way to further improve outcomes in patients with post-traumatic facial scars including pigmented or depressed scars.


References
1. Kim BJ, Kim SH, Cha HG, Park ES. Combination treatment for post-traumatic facial scars: 1,064-nm Nd:YAG picosecond laser with micro-lens array after fractional ablative CO2 laser. Med Lasers. 2022;11(2):92-96.
2. Choi WJ, Park ES, Tak MS, Kang SG. Combination Treatment of Nd:YAG Picosecond-domain Laser and Fractional CO2 Laser for Contracted Neck Scar with Hyperpigmentation. Med Lasers. 2021;10(1):52-54.
3. Ahn KH, Park ES, Choi CY. Effectiveness of a Fractional Picosecond 1,064-nm Laser in Improving Traumatic Scars with Depression. Med Lasers. 2020;9(2):179-183.
4. Choi Y, Park ES. Subsurface Fractional Ablative Resurfacing of a Periareolar Scar Using 1,064-nm Picosecond Laser with Micro-Lens Array. Arch Aesthetic Plast Surg. 2018;24(1):36-38.
5. Lee D, Park ES, Tak MS, Nam SM. The Effectiveness of Ablative Fractional Carbon Dioxide Laser with Autologous Platelet Rich Plasma Combined Resurfacing for Hypertrophic Scar of the Shoulder. Arch Aesthetic Plast Surg. 2016;22(1):40-44.
6. Hong SC, Park ES, Kim YB, Nam SM. Effects of Minimizing Scar Formation by Early Fractional CO2 Laser Resurfacing. Arch Aesthetic Plast Surg. 2014;20(2):109-113.