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Laser therapy for hypertrophic scars and keloids

Laser therapy for hypertrophic scars and keloids
Authors:
C Scott Hultman, MD, MBA, FACS
Shunsuke Yoshida, MD, MS
Section Editors:
Robert P Dellavalle, MD, PhD, MSPH
Moise L Levy, MD
Deputy Editor:
Rosamaria Corona, MD, DSc
Literature review current through: Jul 2022. | This topic last updated: Feb 24, 2022.

INTRODUCTION — Hypertrophic scars and keloids are cutaneous lesions resulting from an excessive tissue response to dermal injury (eg, surgical procedures, trauma, burns, inflammatory skin conditions) and characterized by local fibroblast proliferation and overproduction of abnormal collagen. The clinical features and classification of hypertrophic scars and keloids are summarized in the table (table 1).

Hypertrophic scars present as raised lesions with varying degree of erythema depending upon the maturation stage that typically do not exceed the margins of the original wound. They usually develop two to six months after the initial insult and show a tendency to regress at 18 to 24 months following injury [1]. Associated symptoms include pain, pruritus, and functional limitations. Keloids can occur months or years after injury, extend beyond the limits of the initial injury, and show no tendency to regress.

Many treatments have been tried, with limited success, to reduce the symptoms associated with abnormal scarring, such as redness, pain, pruritus, or functional limitations, and to improve the clinical appearance. These treatments range from minimally invasive interventions (eg, massage, moisturizing agents, pressure garments, silicone sheeting) to topical or intralesional corticosteroids, surgical excision with various reconstructive techniques, or radiation therapy [2,3]. Unfortunately, recurrence rates are high, and multiple or combination therapies are often required to reduce the scar volume and achieve functional and/or cosmetic improvement.

Laser therapy is a relatively new treatment modality for keloids and hypertrophic scars. In particular, the utilization of specific laser platforms has emerged as a successful strategy in the treatment of symptomatic hypertrophic scars following burn injury.

This topic will discuss the available modes of laser therapy for the treatment of hypertrophic scars and keloids, with a focus on treatment of hypertrophic burn scars. Other treatment modalities for hypertrophic scars and keloids are discussed separately. The principles of laser therapy and the use of laser for the treatment of other skin conditions are also discussed separately.

(See "Keloids and hypertrophic scars".)

(See "Hypertrophic scarring and keloids following burn injuries".)

(See "Principles of laser and intense pulsed light for cutaneous lesions".)

(See "Laser and light therapy for cutaneous vascular lesions".)

(See "Laser and light therapy for cutaneous hyperpigmentation".)

(See "Ablative laser resurfacing for skin rejuvenation".)

(See "Nonablative skin resurfacing for skin rejuvenation".)

(See "Light-based, adjunctive, and other therapies for acne vulgaris".)

PRINCIPLES — Lasers are focused beams of light energy released in the form of photons. The light energy is produced and amplified in a lasing cavity flanked by two parallel mirrors. Within the cavity is a lasing medium, consisting of a solid, liquid, or gas compound that is stimulated by an external power source. The excited electrons produce energy in the form of photons when they spontaneously return to the resting state. This organized stream of photons exits the cavity and is guided towards a focusing lens to produce a laser beam. The wavelength of photons is determined by the choice of lasing medium. Lasers can be delivered continuously, in short high-energy pulses, or in nanosecond pulses, called Q-switching.

The number of photons, measured in Joules (J), constitutes the amount of energy delivered by the laser. Power is the rate of energy delivered, measured in watts (W = J/s). Fluence is the energy delivered per unit area (J/cm2), while irradiance is measured as the power per unit area (W/cm2).

Only the light that is absorbed by chromophores produces tissue effects. Common skin chromophores include hemoglobin, oxyhemoglobin, and melanin. Tissue effects can be mechanical, thermal, or chemical and depend upon both the properties of the light and the interaction of the light with chromophores [3].

The parameters by which light can be used to destroy targets in the skin through the selective absorption of light by chromophores and spatial confinement of the effect were first described in the theory of selective photothermolysis in 1983 [4]. The majority of subsequent developments in laser technology for cutaneous disorders have been based upon this theory.

Lasers generate heat, which initiates inflammation and increases vascular permeability, matrix metalloproteinase production, and collagen fiber fascicle decomposition [5]. The tissue hypoxia caused by targeted vascular destruction leads to cell catabolism and prevents collagen deposition. Based upon these considerations, early application of lasers is thought to shorten the duration of acute inflammatory response and accelerate the time to scar maturation [5].

Lasers are categorized into ablative and nonablative types. Ablative-type lasers reach their targets in the dermis by ablating the epidermis. The prolonged recovery period and risks of complications, such as dyspigmentation and further scarring, stimulated the development of fractional and nonablative lasers [6]. Fractional resurfacing creates microscopic columns of ablation, thereby approaching the effect of ablative techniques while reducing the risk of complications and shortening the time to recovery. Nonablative lasers are able to target chromophores in the dermal layer while preserving the epidermis, yielding coagulation of tissues rather than vaporization.

LASER AND LIGHT-BASED PLATFORMS — There are at least four types of lasers commonly used for hypertrophic scars that have documented efficacy in treating various components of these abnormal scars. Platforms include pulsed dye laser (PDL), fractional carbon dioxide (fCO2) laser, alexandrite and diode lasers, and intense pulse light (IPL). Often, two or more of these modalities are combined to improve the outcome [7]. In addition, alexandrite laser and diode laser are used to destroy problematic hair follicles in the scar tissue that can potentially lead to skin irritation and infection.

Traditional or nonfractional ablative lasers, including CO2 and argon lasers, which induce nonspecific thermal damage with significant postoperative pain, prolonged erythema, and high recurrence and infection rates, are no longer used [8-11].

Pulsed dye laser — The PDL at 585 nm and 595 nm wavelengths has been studied extensively for scar remodeling since its introduction in the mid-1990s [12]. This laser selectively targets hemoglobin and has become the standard of care in the treatment of port wine stains, capillary malformations, and some hemangiomas. (See "Laser and light therapy for cutaneous vascular lesions".)

The energy delivered to the dermis coagulates the microvasculature up to a depth of 1.2 mm [13]. This leads to an overall decrease in inflammation by selective photothermolysis of pathologic, neovascularized tissue [7,14]. The resulting tissue hypoxia leads to neocollagenesis, collagen fiber heating, dissociation of disulfide bonds, and subsequent collagen fiber realignment [13]. At the cellular level, PDL decreases fibroblast proliferation, type III (but not type I) collagen deposition, and histamine release [15-17].

Decrease of the scar erythema and pruritus is the main clinical effect of PDL therapy [18,19]. Additional benefits include reduced scar height and volume and improved texture and pliability [9].

Efficacy — The efficacy of PDL 585 nm and 595 nm for the treatment of hypertrophic scars has been evaluated in a few randomized and nonrandomized trials and two systematic reviews [5,20]. However, the heterogeneity in the type and settings of the laser device used across studies makes the comparison among studies difficult. In addition, most studies have significant methodologic flaws that limit the conclusions that can be drawn.

A systematic review of 10 studies (248 patients) of PDL therapy for the treatment of hypertrophic scars found a low or moderate improvement in erythema, scar volume, and pliability associated with treatment with PDL 585 nm and 595 nm, respectively [20].

In a subsequent small, randomized trial including 13 children, PDL 595 nm was applied to graft seams of healed skin grafts placed for reconstruction after burn injury [14]. One-half of the seams were treated with PDL, and the entire scar received standard compression therapy through the duration of the study. After two to three treatments, a greater improvement in vascularity, pigmentation, pliability, scar height, and skin elasticity (assessed by clinician evaluation and Vancouver Scar Scale [VSS]) was noted in the areas treated with PDL plus compression therapy compared with compression therapy alone.

Fractional laser resurfacing — Fractional laser resurfacing was first introduced for the treatment of photoaging and is largely used for cosmetic indications [21,22]. With this technique, microscopic columns of skin called microscopic treatment zones (MTZs) are treated with either ablative or nonablative lasers, resulting in the generation of microscopic thermal wounds with sparing of the tissue surrounding each wound (figure 1).

fCO2 10,600 nm and erbium:yttrium aluminum garnet (Er:YAG) 2940 nm ablative lasers are the primary lasers used for hypertrophic scars [8]. These devices produce MTZs that are 70 to 100 microns in diameter and 250 to 800 microns in depth. Since the target chromophore of CO2 (10,600 nm) laser is intracellular water, treatment results in tissue vaporization and coagulation of surrounding extracellular proteins [3]. In contrast, nonablative lasers induce coagulation only.

At the molecular level, fractional laser treatment induces fibroblast apoptosis, upregulation of matrix metalloproteinases and heat shock proteins, downregulation of transforming growth factors and basic fibroblast growth factor, and alteration of types I and III procollagen levels [11,23,24]. These changes are seen throughout the dermis, beyond the MTZs, with the spared skin surrounding the MTZs contributing to rapid and controlled wound healing with relative normalization of collagen structure and composition [23].

Settings for fCO2 laser include depth, density, pulse energy, shape, and size. The depth of penetration corresponds to pulse energy level and should be tailored to scar thickness. Whether laser depth should penetrate beyond the scar thickness is still being investigated [3]. Density sets the number of MTZs per unit area. Recommended density is less than 10 percent [3]. An inverse relation between density and pulse energy should be applied for safety. Pulse shape and size can be adjusted to fit the scar.

Efficacy — The use of ablative and nonablative fractional laser resurfacing for the treatment of hypertrophic scars and keloids has been evaluated in a small number of randomized trials and uncontrolled studies [7,25-27].

In a split-lesion trial, 25 patients with scars from surgery or trauma received three treatments with an ablative fractional 10,600 nm CO2 laser at eight-week intervals in one of two selected test areas [28]. At six-month follow-up, mild improvement by physician global assessment was noted in only seven patients, with no difference between the treated and untreated areas. Adverse effects occurred in three patients and included persistent erythema, postinflammatory pigmentary changes, and scarring after ulceration.

In another study, 17 adult patients with Fitzpatrick skin types I to IV and mature burn scars were assigned to three treatments at four-week intervals with 1540 nm erbium fractional laser or no treatment in two side-by-side test areas. At 4 and 12 weeks following laser treatments, the treated areas showed a greater improvement in texture compared with the untreated adjacent areas [26]. Superficial burn scars responded better than deeper scars, likely due to the limited penetration depth of nonablative lasers.

In another study, side-by-side scar areas in 17 patients received three monthly nonablative fractional laser treatments or no treatment [29]. At six months, improvement in thickness and texture without change in pigmentation was greater in the treated areas than in the control areas, as assessed by clinicians and patients. Histologic examination at six months showed collagen remodeling from thick surface-paralleled hyalinized bundles to interwoven fibers with higher vascularization and uniform density, and reduced inflammation. Adverse effects at six months occurred in 11 patients and included erythema, hyperpigmentation, and laser grid imprintings.

In a prospective study that included 187 patients with burn scars, the outcome of fCO2 laser treatment (n = 167) was compared with conservative scar treatment (n = 20) [30]. After an average follow-up time of 11.5 months, a greater improvement in ultrasound-measured scar thickness and VSS, as well as in subjective scores (Patient and Observer Scar Assessment Scale [POSAS], neuropathic pain score, and pruritus score), was reported in the laser treatment group compared with the control group. Moreover, patients in the fCO2 laser group consistently reported increases in overall quality of life scores, whereas quality of life scores decreased over time in the conservative treatment group.

fCO2 laser resurfacing of hypertrophic scars has been shown to be efficacious in the pediatric burn population as well. A prospective cohort study examining 49 patients over two years showed significant improvements as assessed by both clinicians and patient family members [31]. The majority of the patients had Fitzpatrick skin type IV or greater. Laser-assisted glucocorticoid delivery was incorporated in over 90 percent of treated patients. Complications were limited to allergic reactions to the surgical preparation solution.

Researchers are starting to study fractional Er:YAG as an alternative laser in treating hypertrophic burn scars. A prospective study examined the efficacy of a single laser treatment over the course of three months [32]. An untreated area of the scar on the same patient served as control. Response measures were objective, including pliability, thickness, transdermal water loss, and contour. No significant differences were found between the two groups. This was attributed to low power, single treatment, and short time interval.

Intense pulsed light — IPL delivers focused, controlled, noncoherent light energy through a coupling gel, across the 515 to 1200 nm spectrum and at a fluency of up to 40 J/cm2 [7]. Technically not a laser, IPL has been previously used for cosmetic indications, including coagulation of vascular lesions, treatment of hyperpigmentations, and hair removal [33,34].

Specific filters in the handpiece allow the user to select from a window of wavelengths (eg, 755 nm for collagen stimulation, 695 nm for superficial leg vein removal, 515 nm for rosacea treatment). The exact mechanism of action is unknown, and no negative long-term effects have been observed. For hypertrophic scars, IPL may be an attractive alternative to more expensive platforms, such as PDL and fCO2 laser [7].

Efficacy — IPL is US Food and Drug Administration (FDA) approved for the treatment of a variety of dermatologic conditions, including melasma, acne vulgaris, and telangiectasia. Evidence for its efficacy in hypertrophic scars is scant.

In one observational study, 109 patients with hypertrophic scars due to surgical, traumatic, or burn wounds were treated with an average of eight IPL treatments administered at two- to four-week intervals [35]. Improvement in scar height, erythema, and hardness was observed in over 90 percent of patients.

A small observational study evaluated the efficacy of IPL for the treatment of burn scar dyschromias in 20 patients, 1 to 15 years after the injury [36]. After one to three IPL treatments, 16 patients reported mild to moderate improvement in color, whereas four patients had no response. Complications occurred in seven patients and included significant pain, blistering, and postinflammatory hyperpigmentation.

The efficacy of IPL has been studied as a combination treatment in conjunction with fCO2 lasers. A small, randomized trial including 23 patients examined hypertrophic scars treated with IPL combined with fCO2 laser and fCO2 laser alone versus untreated controls [37]. Individual scars were divided into three treatment regions. Treated scars showed significant improvements over untreated scars using subjective scar assessment scales. The addition of IPL appeared to have some benefit in the overall color of the scar after six months.

Other lasers — Laser diode is a common type of laser in which the laser light is produced by semiconductor amplification. The 830 nm diode laser was introduced in the 1990s as a low-level light therapy to treat scars and keloids [38]. The mechanism of action is similar to PDL, with hemoglobin and melanin as its chromophores [39].

The long-pulsed alexandrite laser (755 nm) is commonly used for hair removal. The delivered energy is absorbed by melanin in the hair shafts, and the surrounding follicular structures sustain secondary damage leading to destruction of the stem cells in the bulge region of the hair follicle [40]. In patients with large scars, the alexandrite laser may be used to treat retained ingrown hair follicles, which cause folliculitis and are refractory to destruction by the PDL, intense pulsed light, or the diode laser. (See "Removal of unwanted hair", section on 'Laser and intense pulsed light'.)

GOALS OF TREATMENT — Symptoms from hypertrophic scarring can impair quality of life [41]. In particular, itchy and painful scars can reduce sleep, wound contracture can lead to loss of function in multiple joints, and loss of hair follicles and sweat glands can lead to decreased protection from mechanical trauma, ultraviolet (UV) radiation, and loss of thermoregulation [42]. Psychologically, scars can be debilitating by affecting both self-esteem and body image [43].

The goals of laser therapy for hypertrophic scars and keloids are twofold [44]:

Accelerating the time to maturation of a hypertrophic scar

Improving the final endpoint predicted by nonoperative, conventional management

INDICATIONS AND TIMING — Updated international guidelines for the prevention and treatment of pathologic scarring based upon expert consensus have been published in 2014 [45,46]. These guidelines are summarized as follows:

Immature or linear hypertrophic erythematous scars resulting from surgery or trauma that present with persistent erythema for more than one month despite preventive treatment with silicone gel or sheeting, hypoallergenic paper tape, or onion extract preparations may be treated with pulsed dye laser (PDL) once monthly for two to three months. Fractional laser therapy is reserved for scars that are refractory to PDL.

Widespread hypertrophic burn scars that failed to improve with treatment with silicone gel or sheeting, pressure garments, and/or onion extract preparations for 8 to 12 weeks may be treated with fractional laser therapy.

Minor keloids that failed to improve within 8 to 12 weeks with silicone gel sheeting and intralesional corticosteroids may be treated with ablative fractional laser or PDL therapy.

Major keloids that failed to improve with intralesional corticosteroids and fluorouracil may be treated with ablative fractional laser or PDL therapy.

In the authors' experience, PDL can be successfully used at six months postinjury to reverse or diminish the inflammatory response in hypertrophic burn scars [7,13]. Although PDL therapy has been shown to completely resolve persistent erythema up to 17 years following burn injury, the greatest gains in improvement of hypertrophic burn scars appear to occur when laser sessions are started less than 12 to 18 months after injury [13,42,44]. PDL is usually less effective in scars with depths greater than 1.2 mm [13].

PDL treatments should continue until the erythema, hyperemia, and pruritus responses reach a plateau. On average, this takes approximately four sessions [9], at which time fractional carbon dioxide (fCO2) laser treatment can be started to improve scar texture and pliability [19,44]. The optimal interval between laser treatments has not been established. Intervals ranging from four weeks to two to three months have been used, with most studies suggesting six weeks as the optimal interval [3,5,7,13,26,29,42].

CONTRAINDICATIONS — There are no absolute contraindications to laser treatment for hypertrophic scars and keloids [27]. Pulsed dye laser (PDL) fluence levels can be altered based upon the individual patient’s skin phototype. Thus, patients with dark skin tones should not be excluded from laser treatment. Relative contraindications to ablative laser treatment include fresh healing wounds with unstable epidermal coverage in the first one to three months after injury and active infection [47]. In addition, history of herpes simplex virus infection should prompt prophylactic antiviral treatment before laser therapy is offered.

PREOPERATIVE MEASURES

Patient preparation — Some experts recommend skin preparation with chlorhexidine solution and moistening hair-bearing areas prior to treatment [8,9]. We apply laser treatments to clean, dry skin without specific preparation. Hypertropic scar tissue and keloid scars are usually devoid of hair. When removing hair follicles with alexandrite laser, the hair should be shortened to reveal the skin surface. Leaving a short segment of hair allows determination of fluence levels, especially when applying the laser for the first time.

Anesthesia — The type of anesthesia employed prior to laser therapy depends upon several factors, including the mode of laser treatment (eg, ablative lasers are more painful than nonablative lasers), size of the scar, and age of the patient. Children may require general anesthesia, whereas adults can be treated with topical anesthesia [9]. Tumescent anesthesia has been tried and abandoned due to the pain experienced by patients during infiltration. In adults with relatively small treatment areas who undergo nonablative laser treatments, we use a lidocaine cream, applied to the skin surface for 30 minutes prior to the procedure. One prospective study examined the efficacy of a lidocaine/prilocaine mixture applied to the skin prior to fractional carbon dioxide (fCO2) laser treatment and found improvements in pain scores and need for postprocedural opioid administration [48].

Higher energy settings and treatment of large scars or scars located in sensitive areas, such as the hands and face, generally require more than topical anesthesia also in adult patients. In these situations, intravenous sedation and analgesia or general anesthesia with spontaneous ventilation are appropriate [8,44]. This obviates the need for an operating room with a qualified anesthesiologist monitoring patient care.

In burn patients, especially those who may have had tracheostomies or are limited in cervical range of motion due to scars, the delivery of appropriate anesthesia is critical [44]. Hospital-based ambulatory surgery centers are ideal for this setting.

SAFETY MEASURES — Protective eyewear is required for all personnel in the treatment room, including the patient, and metal eye shields are placed on the orbit when treating periocular lesions [49]. It is important to avoid excessive thermal injury by [3]:

Limiting to a single laser modality per treatment area in a given session

Applying fractional treatments at low densities with a relatively narrow beam diameter and pulse width

Minimizing the number of passes

When higher pulse energy settings are chosen, a concomitant decrease in treatment density is required. Treatment can safely include a rim of normal skin at the scar periphery.

When using fractional carbon dioxide (fCO2) laser, it is helpful to verify the laser density on a tongue depressor before using it on the patient. A test treatment in an inconspicuous area to judge the skin's response to pulsed dye laser (PDL) is a strategy that should be considered [50].

Low, conservative fluence levels are recommended, especially when treating darker skin where the test treatment may not be as revealing. Multiple treatments are almost always necessary, and changes in the settings can be made based on the previous treatment and the outcomes observed by the treating surgeon [3].

At our center, mid- to upper-level providers operate the laser, but a clinician must be in the operating suite at all times. Two individuals are required to perform the procedure: the operator, who discharges the laser and aims the pulse at the targeted tissue, and the technician, who manages the settings of the laser and is immediately available to assist with any emergency situations, such as an operating room fire, device malfunction, or inadvertent discharge of the laser [7].

TECHNIQUE

Pulsed dye laser — Pulsed dye laser (PDL) treatment targets hemoglobin, and therefore lasers with a wavelength close to the oxyhemoglobin absorption peak (542 mm) are the most effective [51]. Most authors report using PDL wavelengths of 585 or 595 nm with fluences of 5 to 8 J/cm2, 7 to 10 mm spot size, cryogenic cooling at 30 ms spray/20 ms delay, and pulse duration of 1.5 ms [7,9,13,44]. We use a vascular-specific 595 nm pulsed dye laser to reduce hyperemia and edema of the immature burn scar by selective photothermolysis [44].

Studies have shown that scars respond better to lower, short-pulse fluences, which induce local damage to the vascular endothelium followed by the formation of mural platelet thrombi [52]. Higher fluences do not appear to increase the rate of favorable responses to treatment [5].

Fluence is also selected on the basis of the patient's Fitzpatrick skin type, with lower fluences used for patients with darker phototypes, in an effort to reduce the risk of blistering and postprocedure hypo- or hyperpigmentation [7].

The endpoint of PDL therapy for each session is a purplish discoloration of the targeted area. Adjustments can be made at subsequent treatments in small increments (0.5 to 1 J/cm2), based upon the clinical response. Asking about post-treatment blistering will allow the proper adjustments in fluence for the upcoming laser session. The subsequent laser session should be placed on hold until the skin is fully healed.

Fractional carbon dioxide laser — Thick and stiff hypertrophic scars may regain pliability by applying fractional carbon dioxide (fCO2) laser. We use a fractional 10,600 nm CO2 laser to improve abnormal texture, thickness, and stiffness of more mature scars by ablative destruction and resurfacing [44].

Thick scars are primarily treated using a handpiece with a density of 5 to 15 percent, frequency of 300 to 600 Hz, and 15 to 30 mJ per micropulse, yielding a depth of 375 to 825 micrometers [7,8,24]. Higher energy levels, in terms of mJ/micropulse (which mandate reducing density), are used for thicker scars on the extremity and torso, while lower energy levels (which can permit higher density) are used for thin scars, areas that have been grafted with split-thickness skin grafts, areas on the face, and when treating young patients.

Surface ablation of textural abnormalities is successfully performed using a handpiece at a frequency of 150 Hz and 70 to 90 mJ per micropulse. Other reported ranges for this modality are 90 to 125 mJ, corresponding to a penetration depth of 66 to 112 micrometers, density setting of 3 to 5 percent, frequency of 200 Hz, and 1.3 mm spot size [8,24]. Lower densities are favored in patients with light Fitzpatrick skin types (I to III).

Other lasers — Noncoherent intense pulsed light (IPL) may improve burn scar dyschromia and mild persistent inflammation in hypertrophic burn scars in some patients [7]. We use a workstation with IPL/neodymium-doped yttrium aluminium garnet (Nd:YAG)/light sheer diode with a filter of 515 to 590 nm and a fluence of 18 to 24 J/cm2. The 755 nm alexandrite laser is used to destroy ingrown hair follicles and obstructed sweat glands.

Our approach — In the authors' experience, a combination treatment with PDL and fCO2 laser is more effective than treatment with a single type of laser in improving the pigmentation, pliability, height, vascularity, pain, and pruritus of hypertrophic burn scars (picture 1A-G). We typically use PDL to decrease inflammation, erythema, and pruritus in the early stages of hypertrophic burn scar maturation and fCO2 laser for later stages when improvement in stiffness, contour, and pliability are desired, as shown in the algorithm (algorithm 1).

Treatment begins within the first 6 to 36 months after burn injury with the use of PDL to reduce the scar hyperemia and thickening [7,44,53]. A six-month period following injury usually allows us the appropriate amount of time to determine which scars are likely to mature with conventional medical therapy, thus avoiding overtreatment. Burn scars without significant pruritus, erythema, hypertrophy, or stiffness can be safely and effectively treated without laser therapy.

Subsequent treatment with fCO2 ablative laser can be started at 12 months after injury or following the conclusion of PDL treatment. Laser treatments are delivered at four- to six-week intervals until a plateau in improvement is observed. Generally, only one modality is used per session, but more than one platform can be used on different sites in the same session.

The treatment of hypertrophic burn scars with a combination of laser treatments has been evaluated in a prospective, before-after study at our center [44]. In this study, 147 patients with hypertrophic burn scars involving a mean body surface area of 16 percent underwent an average of three laser treatments with PDL, fCO2 laser, IPL, and intralesional steroid injections when indicated. Outcomes were measured by the Vancouver Scar Scale (VSS), which assesses scar pigmentation, erythema, pliability, and height, and by the University of North Carolina "4P" scale (UNC4P), which assesses patient-reported pain, pruritus, paresthesias, and pliability. A significant reduction in both VSS and UNC4P scores was observed after a mean follow-up time of 4.4 months.

Further reduction in the VSS score was achieved in a subgroup of patients who underwent an average of five laser treatments and were followed up for a median time of 26 months [44]. The improvement was greater than would be predicted by standard decay curve modeling for untreated patients. Complications occurred in 13 percent of patients and included moderate to severe blistering, postinflammatory hyperpigmentation, and infection.

POSTOPERATIVE CARE — Ice packs are commonly used on the skin immediately following treatment [27]. Most experts suggest topical application of petrolatum or antibiotic ointments on laser-treated sites for one week [3,13,44]. Patients may resume normal activity almost immediately, including physical or occupational therapy, with the exception of full immersion in water in cases of treatment with an ablative laser [3,44]. Depending upon the discomfort level and the desired type of activity, patients may return to school or work after one to three days.

Because compression garments may cause some sheer of the treated tissue, we now recommend waiting for several days, until edema subsides, wounds re-epithelialize, and discomfort lessens, before getting back into these garments [44]. Sun avoidance and use of broad-spectrum sunscreens with sun protection factor (SPF) of at least 30 is mandatory [3,27,44].

Adequate analgesia is usually achieved with nonsteroidal anti-inflammatory agents, although some patients with chronic intense pain may need a short course of narcotic pain medication [44].

COMPLICATIONS — The overall complication rate for pulsed dye laser (PDL) ranges from 0 to 20 percent [5]. Similar rates have been reported for other nonablative lasers [26,29].

Common complications of PDL therapy include transient purpura and mild to moderate erythema or edema that usually resolves in 7 to 10 days [5,13,27,42]. However, in some cases, a mild erythema can persist up to three months post-treatment [27]. Occasionally, skin blistering or crusting may occur in the early post-treatment phase. Hypo- or hyperpigmentation may also occur, especially in patients with darker skin types [3,5,9,13,42,50]. Overtreatment of burn scars may induce scarring exacerbation, especially in skin with darker pigmentation, in which melanin acts as a competing chromophore [54]. Intraprocedural cryogenic cooling of the skin may limit these adverse reactions.

Fractional ablative lasers have an improved adverse effect profile compared with nonfractional ablative devices. However, delayed wound healing, ulceration, postinflammatory hyperpigmentation, and scarring, particularly in areas of thinner skin and decreased adnexal structures such as the neck, have also been reported with fractional lasers [55]. This may be due to bulk heating of tissue and penetration of laser energy beneath the dermis [24].

One study examined the adverse event profile of 373 successive treatments with fractional 10,600 nm CO2 laser for cosmetic indications in 287 patients [56]. Adverse events occurred in approximately 14 percent of patients and included allergic or contact dermatitis (4.6 percent), acneiform eruption (3.5 percent), prolonged erythema (1.1 percent), and herpes simplex virus infection (1.1 percent).

In another study, the overall rate of adverse events following PDL and/or fractional carbon dioxide (fCO2) laser treatments for hypertrophic burn scars was 25 percent [50]. Most common adverse effects were pain (37 percent) and blistering (27 percent), followed by hypopigmentation (12 percent), fever (10 percent), rash (7 percent), laryngospasm (3 percent), hyperpigmentation (2 percent), and infection (2 percent). In this study, scald burn patients had an increased risk of blistering, rash, and post-treatment fever, whereas flame burn patients were more likely to develop post-treatment blistering.

In a systematic review, adverse events associated with ablative fractional laser occurred in 2.5 percent of patients (15 studies, 681 patients) and included skin discoloration (40 percent), pain/swelling (20 percent), erythema (12 percent), blistering (8 percent), paradoxical scar overgrowth (8 percent), infection (2 percent), and ulceration (2 percent) [57].

The results of these studies suggest that lower fluence and density settings should be selected initially to reduce the rate of adverse events. A test treatment in an inconspicuous area to judge the skin's response to PDL is a strategy that should be employed in these patients.

ADJUVANT TREATMENTS — Z-plasty is a surgical technique that creates local transposition flaps to relieve tension along a scarred wound (see "Z-plasty"). Combining pulsed dye laser (PDL) therapy with Z-plasty appears to have a synergistic effect in the treatment of hypertrophic burn scars, in which tension is deemed to play a role in hypertrophy, and may reduce the need for surgical excision [13].

In a few small, uncontrolled studies of patients with mature hypertrophic scars, the application of topical corticosteroid suspensions in combination with fractional laser therapy resulted in improved scar texture and appearance without significant adverse events [8,58]. The pinholes created by the laser beam are thought to maximize drug absorption by providing an avenue for precise placement of the drug while avoiding adverse sequelae such as fat atrophy. At the authors' institution, the lasered pinhole sites are covered evenly using triamcinolone acetonide suspension 10 mg/mL or 40 mg/mL, titrated to the patient's body weight at a dose of 1 mg/kg.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Keloids and hypertrophic scars".)

SUMMARY

Laser therapy is a relatively new treatment modality for keloids and hypertrophic scars. In particular, the utilization of specific laser platforms has emerged as a successful strategy in the treatment of symptomatic hypertrophic scars following burn injury. (See 'Introduction' above.)

Lasers that are commonly used for the treatment of hypertrophic scars and keloids include pulsed dye laser (PDL), fractional carbon dioxide (fCO2) laser, and intense pulsed light (IPL). (See 'Laser and light-based platforms' above.)

Indications for therapy with PDL or ablative fractional laser include:

Immature or linear hypertrophic erythematous scars resulting from surgery or trauma that present with persistent erythema for more than one month despite preventive treatment with silicone gel or sheeting, hypoallergenic paper tape, or onion extract preparations.

Widespread hypertrophic burn scars that failed to improve with treatment with silicone gel or sheeting, pressure garments, and/or onion extract preparations for 8 to 12 weeks.

Minor keloids that failed to improve within 8 to 12 weeks with silicone gel sheeting and intralesional corticosteroids.

Major keloids that failed to improve with intralesional corticosteroids and fluorouracil. (See 'Indications and timing' above.)

In the authors' experience, a combination treatment with PDL and fCO2 laser is more effective than treatment with a single type of laser in improving the appearance and reducing the symptoms associated with hypertrophic burn scars. We typically use PDL to decrease inflammation, erythema, and pruritus in the early stages of hypertrophic burn scar maturation and fCO2 laser for later stages when improvement in stiffness, contour, and pliability are desired (algorithm 1). (See 'Technique' above and 'Our approach' above.)

Common complications of PDL therapy include transient purpura and mild to moderate erythema or edema that resolves in 7 to 10 days. Occasionally, skin blistering or crusting may occur in the early post-treatment phase. Hypo- or hyperpigmentation may also occur, especially in patients with darker skin types. Delayed wound healing, ulceration, postinflammatory hyperpigmentation, and scarring may occur with fractional laser therapy. (See 'Complications' above.)

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References