A Review and Update of Treatment Options Using the Acne Scar Classification System

Monica Boen, MD* and Carolyn Jacob, MD†

BACKGROUND An unfortunate consequence of acne vulgaris is residual scarring that can negatively affect a patient’s quality of life.

OBJECTIVE Jacob and colleagues have previously described an acne scar classiﬁcation system based on acne scar pathology that divided atrophic acne scars into icepick, rolling, and boxcar scars, and this review will evaluate new and developing treatment options for acne scarring.

METHODS A Medline search was performed on the various treatments for acne scars, and particular attention was placed on articles that used the acne scar classiﬁcation system of icepick, rolling, and boxcar scars.

RESULTS Therapies for acne scarring included surgical modalities, such as subcision, and punch excision and elevation, injectable ﬁllers, chemical peels, dermabrasion, microneedling, and energy-based devices. In the past decade, there has been a trend toward using cosmetic ﬁllers and energy-based devices to improve acne scarring.

CONCLUSION There were few high-quality evidence-based studies evaluating the management of acne scarring. Many disparate acne severity scores were used in these studies, and the acne scar type was frequently undeﬁned, making comparison between them difﬁcult. Nonetheless, research into interventions for acne scarring has increased substantially in the past decade and has given patients more therapeutic strategies.

The authors have indicated no signiﬁcant interest with commercial supporters.

cne is a very common inflammatory disorder of classification system has allowed a consistent and Athe pilosebaceous unit that consists of standardized definition of acne scars that has been comedones, inflammatory papules, pustules, and adopted into clinical research and has aided in treat- nodules involving the face, chest, and back.1 The ment regimens. Each of these scar types has been pathogenesis of acne is complex and involves classified based on the underlying scar pathology. By inflammation and release of cytokines around the classifying acne scars into distinct types, treatment pilosebaceous unit, abnormal keratinization, options can be better tailored to each individual increased sebum production, and Propionibacterium patient (Table 1). acnes.2 An unfortunate sequelae of acne is residual scarring and disfigurement. Acne and acne scarring Icepick scars are narrow (<2 mm) and extend verti- can have a detrimental impact on the quality of life and cally into the deep dermis or subcutaneous tissue.4 lead to feelings of embarrassment and low self- Because of the deep extension of icepick scars, con- esteem.3 ventional skin resurfacing options will not ade- quately treat these types of scars. Rolling scars have Jacob and colleagues4 have previously described a sloped and shallow borders with a normal skin tex- classification system to define atrophic acne scars into ture at the base and are about 4 to 5 mm wide.4 These 3 basic types: icepick, rolling, and boxcar scars. This scars result from abnormal fibrous bands anchoring

*Department of Dermatology, University of Illinois at Chicago, Chicago, Illinois; †Department of Dermatology, Northwestern Feinberg School of Medicine, Chicago, Illinois

© 2019 by the American Society for Dermatologic Surgery, Inc. Published by Wolters Kluwer Health, Inc. All rights reserved. ISSN: 1076-0512 · Dermatol Surg 2019;45:411–422 · DOI: 10.1097/DSS.0000000000001765

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TABLE 1. Acne Scar Classiﬁcation

Acne Scar Treatment Subtypes Description Treatment Options Efﬁcacy* Icepick <2 mm and narrow Punch excision +++ Tapers as extends to deep TCA CROSS ++ dermis Radiofrequency + Laser skin resurfacing +

Rolling 4–5 mm wide Subcision +++ Sloped and shallow borders Fillers +++ Dermabrasion ++ Caused by dermal tethering of Microneedling ++ otherwise normal skin Radiofrequency ++ Laser skin resurfacing ++

Boxcar 1.5–4 mm wide Shallow boxcar: Round to oval depressions with Punch elevation +++ sharply demarcated vertical edges Dermabrasion ++ Can be shallow (0.1–0.5 mm) or Microneedling ++ deep ($0.5) Radiofrequency ++ Laser skin resurfacing ++

Deep boxcar: Subcision ++ TCA CROSS ++ Punch excision/ ++ elevation Laser skin resurfacing ++

*(+++) highly effective (++) effective (+) adequate. CROSS, chemical reconstruction of skin scars; TCA, trichloroacetic acid.

the dermis to the subcutis, which produces a dell in Cosmetic Fillers the skin. Treatment is aimed at correcting the In the past decade, there has been a rapid influx of abnormal fibrous anchoring of these scars. Finally, cosmetic injectable fillers, from temporary hyaluronic boxcar scars are round to oval, or rectangular, acid (HA) fillers to semipermanent and permanent depressions with sharply defined vertical edges that fi 5 fi can be shallow (0.1–0.5 mm) or deep ($0.5). Shal- llers (Table 2). Several of these cosmetic llers have low boxcar scars, rather than deep boxcar scars, are been used for atrophic acne scars to increase tissue more amenable to treatment with resurfacing volume in these lesions and to stimulate collagen 6 modalities. Other scar types, including, hypertro- production. Superficial rolling and boxcar scars phic, keloidal, and sinus tract scars are less common. respond best to cosmetic fillers and have been com- In this review, we will provide an update on the bined with subcision to enhance results.7 A recent treatment options available for acne scarring, Cochrane review found moderate-quality evidence for focusing on the 3 types of atrophic acne scars. the efficacy of cosmetic fillers in atrophic acne scars.8

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scars who were treated with 1 to 2 injections of CaHA, TABLE 2. Soft tissue fillers used to treat acne scars 30% of patients showed greater than 75% improvement and 60% of patients showed between a 50% to Duration 75% improvement in acne scars after 12 months.15 No Soft-Tissue Fillers of Action Examples improvement was seen in icepick scars. Hyaluronic acid filler 3–12 mo Restylane, Juvederm, Belotero Poly-L-Lactic Acid Calcium hydroxylapatite 1–2 yrs Radiesse Poly-L-lactic acid 1–2 yrs Sculptra, Poly-L-lactic acid (PLLA; Sculptra, Galderma, Fort Newfill Worth, TX) is a nonimmunogenic and biodegradable Polymethylmethacrylate Permanent Artecoll, Artefill, synthetic polymer that induces the production of col- Bellafill lagen by increasing the number of fibroblasts through a foreign-body reaction, which improves skin Our article only summarizes the available treatment texture over time.16 Several injections of PLLA are options for cosmetic fillers approved by the United needed to restore volume because of its biostimulatory States Food and Drug Administration (FDA); how- mechanism of action. PLLA has been shown to ever, there are many injectables available interna- improve acne and varicella scarring in an open-label 17 tionally that can also be suitable for the treatment of prospective study with 20 patients. After 7 treat- acne scarring. ments, there was a cumulative reduction of 46.4% in the severity of the scars. Sapra and colleagues18 Hyaluronic Acid performed a study on the treatment of hill and valley acne scarring, also known as rolling scars, in 22 Hyaluronic acid is composed of a water-retaining patients with 3 to 4 treatments of PLLA, and 54.4% of glycosaminoglycan polysaccharide, which is a natu- patients had very good results. A new modality of

rally occurring component of the body’s connective fractionated CO2 laser–assisted delivery of topical tissue. Hyaluronic acids are temporary fillers that last PLLA led to a 33% improvement in atrophic scars, for 3 to 12 months. Hasson and Romero9 showed that including acne scars, in 20 patients after a single 19 in 12 patients with atrophic scars from various etiol- treatment. Poly-L-lactic acid necessitates the use of ogies treated with HA (Esthelis,´ Anteis, S.A., Geneva, more treatment sessions than other cosmetic fillers but Switzerland), 74% had good to excellent results can produce sustained results for over 2 years. 1 month after treatment. A 68% reduction in acne scars was seen in a recent study in 5 patients who had 2 Polymethylmethacrylate treatments of HA in a modified vertical tower technique.10 Although few studies have been performed to Polymethylmethacrylate (PMMA) is a permanent fi investigate the use of HAs for acne scars, HAs are ller composed of 20% PMMA microspheres, 30 to 20 widely used by dermatologists to treat atrophic acne 50 mm in diameter, suspended in bovine collagen. scars.11,12 PMMA adds volume to acne scars and stimulates collagen production, and it can be a cost-saving Calcium Hydroxyapatite alternative to the temporary fillers because only one treatment is usually required. In 2015, PMMA became Calcium hydroxyapatite (CaHA; Radiesse, Merz the only FDA-approved cosmetic filler for the treat- Pharma, Frankfurt, Germany) is a semipermanent and ment of facial acne scars.21 A pilot study using sub- biocompatible filler composed of 25- to 45-mm fi microspheres of synthetic CaHA in an aqueous gel cision followed by one treatment of PMMA (Arte ll; containing water, glycerin, and carboxymethylcellu- Suneva Medical Inc., Santa Barbara, CA) in 14 lose.13 Calcium hydroxyapatite stimulates collagen patients showed a 96% improvement in acne scars by production by invoking a local response of histiocytes investigator ratings 8 months after treatment without and fibroblasts.14 In a study of 10 patients with acne adverse events.22 Karnik and colleagues23 performed a

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controlled and blinded study with 147 patients with collagen is formed in a plane that is more even with rolling acne scars who were treated with one injection the surface of the surrounding skin.27 Usually, sev- Artefill or placebo, and improvement in acne scars was eral treatments are necessary. Adverse events include observed in 64% of patients treated with PMMA temporary swelling and bruising, and rarely sub- versus 33% of control subjects. The most common dermal nodule formation. adverse effect was injection site reaction. Subcision works best for rolling scars and is less effec- Cosmetic fillers provide a minimally invasive option to tive for deep boxcar scars and icepick scars. Several treat acne scars by adding volume to the scar and also studies have demonstrated subcision as a stand-alone stimulating collagen production to improve skin tex- therapy for acne scarring. A study with 34 patients who ture. They can also be used in combination with other had undergone 1 to 3 subcision treatments reported laser procedures to achieve the best results (Figure 1). downgrading of acne severity from severe and moder- The literature evaluating the use of fillers for acne scars ate grade acne to mild grade in 53% of patients is limited, and more studies are needed to determine with minimal side effects.28 Subcision has shown the optimal filler type and number of treatments for superior results to 100% trichloroacetic acid (TCA) soft-tissue augmentation of acne scars. chemical reconstruction of skin scars (CROSS) method in 20 patients with fewer side effects.29 Subcision has also been combined with other acne scar treatment Subcision modalities. Recently, subcision has been combined Subcision is a simple surgical procedure that was with the use of cosmetic fillers and nonablative 1,320- initially described by Orentreich and Orentreich24 in nm neodymium-doped:yttrium aluminum garnet 1995. Traditionally, it involves the use of a tribeveled (Nd:YAG) laser to enhance the appearance of scars and hypodermic needle to free the tethering subdermal skin texture.22,30 Finally, although subcision has been fibrous bands that are responsible for rolling scars, shown mostly to reduce rolling acne scars, a recent although several other instruments have been used study of 18 patients who underwent subcision with a such as conventional needles and blunt blades (Fig- blunt blade under tumescent anesthesia showed ure 2).4,25 The needle is placed in a horizontal plane marked to moderate improvement in 15 of the 18 in the upper subcutaneous tissue and advanced in a patients treated, and deep boxcar and icepick scars gentle back and forth motion parallel to the skin to demonstrated partial leveling as well.25 release the fibrous bands. This causes subdermal bleeding, and the formed blood clot creates a Subcision is a well-tolerated and effective procedure to potential space in the tissue to elevate the skin within treat rolling and shallow boxcar scars and can be the scar tissue.26 Thus, when the area heals, new combined with other treatments for acne scarring.

Figure 1. Before (left) and after (right) 3 treatments with polymethylmethacrylate dermal ﬁller and RF microneedling. Photo courtesy of Douglas C. Wu, MD, PhD. RF, radiofrequency.

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icepick scars.34 Recently, punch elevation combined

with fractional CO2 laser showed better results for acne 35 scarring than fractional CO2 laser alone.

Few studies exist in the literature examining the use of punch excision and elevation for acne scarring; however, they can be excellent options for deep icepick scars and boxcar scars.

Chemical Peels

Figure 2. Tribeveled 18G hypodermic needle used for A chemical peel is a quick outpatient procedure that subcision. can be used to treat acne scarring. Mild acne lesions and shallow atrophic acne scars can respond well to Punch Excision mild and medium depth peels, such as 20% to 35% Punch excision is an excellent option for the treatment TCA, alpha hydroxy acids, salicylic acid, and Jess- of icepick and deep boxcar scars. In this method, a ener’s solution.36 However, these chemical peels usu- punch biopsy instrument is used to remove deep atro- ally work best for macular scars, have limited use for phic scar tissue to the level of the subcutaneous fat and deeper atrophic scars, and should be used cautiously in then closed with sutures. The scars should be at least 4 darker-skinned patients because of the potential for to 5 mm apart to prevent excess traction in the skin, or pigmentary alterations. Deep chemical peels have at least a 4-week interval between procedures can avoid fallen out of favor for the treatment of acne scars these adverse cosmetic effects. For scars larger than because of their significant side effect profile, such as 3.5 mm, elliptical or punch elevation is recommended dyschromia and scarring.11 for best cosmetic outcome.4 Although a new scar is formed in this method, it is usually less noticeable than In the past decade, chemical reconstruction using TCA the previous deep atrophic scar.26 Using a resurfacing (CROSS) has come into favor for icepick scars and has procedure 4 to 6 weeks after punch excision can also also been used for rolling and boxcar scars. In the improve the appearance of the scar.31,32 Punch excision CROSS method, high concentrations of TCA are can be safely and effectively combined with laser skin applied on a sharp wooden applicator and then resurfacing on the same day for acne scarring.33 pressed firmly into the atrophic acne scars, and white frosting is observed.37 The high concentrations of TCA cause coagulative necrosis of the epidermis, and Punch Elevation the resultant wound healing causes an increase in the Punch elevation is a useful tool for shallow and deep production of collagen and improvement in scar boxcar scars. This technique combines aspects of punch appearance.26 The CROSS method allows for shorter excision and grafting. A punch biopsy tool is used to recovery time than medium to deep chemical peels excise the scar down to the subcutaneous fat, and the because the peel is applied to only select areas of the tissue is then elevated slightly above the plane of the skin skin. Several treatments with TCA CROSS are usually and fixed into place with sutures or steristrips. During needed, and the degree of clinical improvement is the wound healing process, the elevated graft retracts proportional to the number of treatments. This tech- slightly tothe surfaceof the surrounding skinto improve nique has been shown to significantly improve deep the appearance of the scar.26 As with punch excision, a icepick scars, rolling, and boxcar scars.38–40 Tri- resurfacing procedure performed 4 to 6 weeks after chloroacetic acid has been compared with the 1,550- procedure can enhance results. Punch elevation and nm erbium:glass laser in 20 patients with darker skin

punch excision has been combined with CO2 laser types, and both procedures were shown to be equiv- treatment and dermabrasion to effectively treat deep alent in efﬁcacy for icepick scars, but the 1,550-nm

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erbium:glass laser was slightly more effective for roll- Microneedling ing scars.41 Rare complications of TCA CROSS Microneedling is an inexpensive treatment option for include dyschromia, erythema, scarring, and atro- acne scars. It consists of a sterile rolling device with phy.42 Nonetheless, high-concentration TCA CROSS several fine sharp needles applied to acne scars to has been used in dark-skinned patients with minimal create multiple small micropunctures in the papillary or without any prolonged pigmentary changes or to mid-dermis. By creating these small wounds in the scarring.37–39 dermis, a cascade of growth factors is initiated that results in collagen stimulation and production.36 As Optimal concentration of TCA and number of treat- microneedling penetrates only to the depth of the ments should be tailored to patient response to each upper dermis, it is most useful for shallow boxcar and treatment and observation of possible side effects. rolling scars. A usual treatment course with micro- Deep boxcar and icepick scars are especially hard to needling consists of 3 to 5 sessions spaced 4 weeks treat, and TCA CROSS can be a useful method to apart, and results are seen in 3 months. Patients usu- manage these lesions. ally experience a moderate improvement in acne scar appearance. Dermabrasion Several recent studies have shown the efficacy of Dermabrasion involves the use of manual derma- microneedling in the treatment of acne scars. El- sanding using sandpaper and hydrogen peroxide for Domyati and colleagues47 showed a 51% to 60% hemostasis, or a rotating motorized hand piece improvement of acne scars after 6 sessions of micro- attached to either a serrated wheel, wire brush, or needling. In this study, skin biopsies were also per- diamond-embedded fraises to remove the epidermis formed before and after the microneedling and upper dermis.43,44 By removing the superficial procedures, and they showed a statistically significant layers of the skin, the wound healing process creates a increase in collagen Types I, III, and VII. When smoother and more regular appearance of the scar, microneedling was combined with platelet-rich and new collagen is formed.45 Dermabrasion is useful plasma or glycolic acid peels, improvements in acne for superficial atrophic acne scars, such as rolling or scar appearance increased to 62%.48,49 A study shallow boxcar scars, but is less effective for icepick comparing microneedling with fractional non- scars.26 ablative erbium 1,340-nm laser in 46 patients showed improvement in both groups and no statistically sig- Advantages of dermabrasion include improvement in nificant difference between the 2 treatments.50 the appearance of superficial atrophic scars with only Approximately 14% of the patients in the laser group one treatment. However, the dermabrasion technique experienced postinflammatory hyperpigmentation is operator-dependent, and that the procedure is and, no pigmentary changes were seen in the micro- painful and requires local or general anesthesia. There needling group. is significant postoperative pain and a lengthy healing time lasting up to several weeks with prolonged ery- Microneedling has shown benefit in the reduction of thema and postprocedural dyschromia.11 There are shallow boxcar and rolling scars and can be a good other resurfacing modalities that offer fewer side option for darker-skinned patients because there is a effects and have a quicker recovery time, such as low risk of hyperpigmentation. fractional ablative lasers. Jared Christophel and col- leagues46 demonstrated in a split-face study of scars from Mohs procedures that dermabrasion and frac- Platelet-Rich Plasma tional ablative CO2 lasers produced similar improvements in scar appearance, but the fractional ablative Plasma-rich plasma (PRP) is an emerging therapeutic

CO2 laser had a better side effect proﬁle and quicker tool that consists of a preparation of the patient’s healing time. own concentrated platelets in plasma to promote

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wound healing through several growth factors and showed at least a 25% to 50% improvement after 6 to cytokines present in the concentrate. Plasma-rich 8 sessions with bipolar RF in improvement in 3 of the 4 plasma has been used in several areas of medicine, patients with acne scars. Adverse effects included including for tendon injury, chronic ulcers, and alo- transient erythema (Table 3). pecia.52–54 Only a few studies have investigated PRP for acne scars, and they have shown that this treat- In the past few years, there have been several studies ment is safe and mild to moderate clinical improve- using fractional RF for the treatment of acne scars. ment after intradermal or laser-assisted PRP Fractional RF is a newer technology that consists of delivery.48,55–57 Lee and colleagues56 treated 14 the application of bipolar RF to the skin by electrodes

patients with acne scars with an ablative CO2 laser, or pairs of microneedles to create small columns of and on one side of the face applied PRP. They showed thermal damage.59 Peterson and colleagues64 used a slightly faster healing and clinical improvement on new device that combined RF with FRF for acne the PRP-treated side. Nofal and colleagues57 com- scarring in 15 patients and showed a 73.4% reduc- pared intradermal PRP, TCA CROSS, and combi- tion of the scars after 5 procedures. The investigators nation of PRP and microneedling for a mixture of found that rolling and boxcar scars responded better atrophic acne scar types and showed that half of the than icepick scars. Ramesh and colleagues65 showed patients had a one-grade improvement in acne and no that FRF had good to excellent results in 22 of 30 difference between the treatment groups. Further patients after 4 sessions. Unlike the previous study, research and comparative studies are needed to icepick scars responded better than rolling and box- evaluate the efﬁcacy of PRP for acne scars. car scars. Gold and Biron66 used an FRF to treat 15 patients for 3 sessions and showed a 60% marked improvement in acne scars. Fractional bipolar RF Radiofrequency was studied by Cho and colleagues67 in 30 patients Radiofrequency (RF) is an evolving tool that was treated with 2 sessions with a 73.3% reduction in used initially in dermatology for skin rejuvenation. acne scars. In addition, skin surface roughness This device uses electromagnetic radiation to gen- improved, and there was a decrease in the size of erate an electric current that heats the dermis facial pores. Adverse effects included pain with the causing neocollagenesis and skin contraction.58,59 procedure and transient erythema. Another study Radiofrequency has decreased downtime and risk with FRF showed an improved appearance of scars of scarring and infection compared with ablative lasers, and it can be safe to use in all skin types as it is chromophore-independent, unlike other energy- Table 3. Types of radiofrequency devices used to 60 based modalities, such as CO2 laser. The initial treat acne scars RF device was monopolar and has evolved into Radiofrequency bipolar and later fractional bipolar RF (FRF) (RF) Devices Description (Table 2). Monopolar RF Two electrodes with one in contact with the skin and the other as the The earliest studies using RF to treat acne scars were grounding pad to target deep dermis. with the monopolar and bipolar RF devices. In one Bipolar RF Two active electrodes that are study, 22 patients with active cystic acne and acne placed a short distance apart scars were treated with a monopolar RF device for 1 to from the intended treatment area to create more focused energy 2 sessions (ThermaCool TC; Thermage Inc., Hay- delivery and less painful than ward, CA), and 82% showed an excellent improve- monopolar RF. ment in acne.61 No side effects were observed, and Fractional bipolar Creates fractional zones of RF electrothermal damage in the there was no downtime after the procedure. Bipolar dermis using electrodes or RF delivers a more focused current to the dermis than microneedles inserted into the skin. monopolar RF.62 A study by Montesi and colleagues63

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Figure 3. Before (left) and after (right) 2 radiofrequency microneedling treatments. Photo courtesy of Douglas C. Wu, MD, PhD.

without damaging the epidermal layer in all 31 The ablative lasers produce excellent results for acne patients after 4 sessions.68 As with previous FRF scars. In one study, there was a 75% mean improve- studies, a major adverse effect was procedural- ment in atrophic facial scars with high-energy pulsed 72 related pain, even with nerve blocks, or topical CO2 laser. A long-pulsed Er:YAG laser in a study anesthesia. with 35 dark-skinned patients for pitted facial acne scars showed good to excellent results in 74% of Of the RF devices available, FRF offers the best results patients.73 However, postinﬂammatory hyperpig- 69 for acne scarring. An improvement of 25% to 75% mentation occurred in 29% of patients, and all in acne scars can be expected after 3 to 4 sessions patients experienced prolonged erythema. Because of (Figure 3). Radiofrequency is a safe and effective the long recovery time and side effects from ablative approach to treat all 3 types of atrophic acne scars with lasers and the development of new nonablative and limited downtime and adverse effects, but further fractional lasers with less downtime, ablative lasers studies are needed for optimal treatment parameters. have become a less popular option for the treatment of acne scars. Lasers

Lasers are another popular treatment option for acne Nonablative Lasers scarring (Table 4). They are grouped into the tradi- Nonablative lasers are a more noninvasive way to treat tional ablative lasers that cause epidermal and dermal acne scars. Commonly used nonablative lasers include destruction and the less-invasive nonablative lasers the 1,064-nm Nd:YAG, 1,320-nm Nd:YAG, and 585/ that target the dermis but leave the epidermis intact. 595-nm pulsed dye laser (PDL) (Table 4). Nonablative More recently, fractional laser resurfacing has been lasers target tissues in the dermis by selective photo- used for acne scarring and consists of delivering energy thermolysis to stimulate collagen and dermal remod- in microscopic columns of epidermal and dermal tis- eling to reduce acne scar appearance.74 They work best sue.70 Each of these laser modalities has varying risks, for shallow boxcar and rolling scars and are less downtime, and varying efficacy on the 3 atrophic acne beneficial for icepick scars. scar types. There have been several studies using different types of Ablative Lasers nonablative lasers for acne scarring with mild to fi The ablative lasers, CO2 10,600-nm and Er:YAG moderate bene t, and usually 4 to 6 treatments are 2,940-nm lasers, are considered the gold standard for required. The 1,064-nm Nd:YAG laser is used fre- treating acne scars with a laser modality. They target quently for acne scarring and has shown to produce a water in the skin causing dermal injury, along with 20% to 50% improvement in these lesions.75,76 In one damage to the epidermis, and in this process create the study, PDL has shown similar efficacy to the 1,064-nm formation of new collagen.71 Nd:YAG for acne scars with a mean improvement of

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TABLE 4. Laser Modalities Available for Acne Scarring79

Traditional Ablative Traditional Nonablative Fractional Nonablative Fractional Ablative

Ablative 10,600-nm CO2 1,320-nm Nd:YAG Fractional 1,550-nm Er-doped Fractional 10,600-nm CO2 Ablative 2,940-nm Er:YAG 1,064-nm Nd:YAG Fractional 1,540-nm Er:glass Fractional 2,940-nm Er:YAG 1,450-nm Nd:YAG Fractional 2,790-nm YSGG 755-nm picosecond 585-/595-nm PDL 532-nm KTP Intense pulse light*

*Not a laser. PDL, pulsed dye laser.

about 18%. Wada and colleagues77 treated 24 Japa- proportional to the degree of improvement.79 Sar- nese patients with various atrophic scars with 5 ses- dana and colleagues80 classified each acne scar sub- sions of the 1,450-nm diode laser, and 75% of the type and recorded the response of each scar to the patients had moderate to marked improvement in acne treatment with the 1,540-nm fractional nonablative scars. Patients with a combination of rolling and laser. After 6 treatments with the 1,540-nm frac- boxcar scars responded best in this study with minimal tional laser, boxcar and rolling scars were found to adverse events; however, one patient did have post- respond better than icepick scars, with a 52.9% and inflammatory hyperpigmentation. When nonablative 43.1% improvement in boxcar and rolling scars, lasers are compared with fractional ablative lasers for respectively, while icepick scars only responded in acne scarring, fractional ablative lasers overall pro- 25.9% of patients. The 1,550-nm erbium-doped duce better results albeit can cause more complica- fiber fractional laser has also been shown to be safe tions. Asilian and colleagues78 compared the and effective in treating acne scarring with multiple sessions in Fitzpatrick skin Type IV to VI; however, fractional CO2 and Q-switched 1640-nm laser in a some patient developed self-limited post- study of 64 patients and found that the fractional CO2 fl 81 laser produced better outcomes for acne scars. Adverse in ammatory hyperpigmentation. Some authors events were similar in both laser groups and consisted advocate using lower total treatment densities, of postinflammatory hyperpigmentation. decreased number of passes, and pre-treatment and post-treatment with hydroquinone in darker- Nonablative lasers are becoming more popular for skinned patients to decrease the risk of post- fl 81,82 acne scarring because they have a faster postin ammatory hyperpigmentation. procedural recovery time and a better side effect profile than ablative lasers. However, more sessions are Ablative laser has been evaluated for acne scarring by 83 required, and acne scar improvement may not match Jung and colleagues who performed a study to the level of the ablative lasers. compare the optimal laser settings for the treatment of scars with a fractional CO2 laser in 10 patients in a fl Fractional Lasers split-face study. They showed that high- uence and low-density settings showed greater improvements in Fractional lasers are divided into nonablative laser acne scar appearance than on the low-fluence and (NAFL) and ablative laser (AFL) and have been high-density settings. A study by Cho and colleagues

evaluated in several studiesforthetreatmentofacne compared one treatment with fractional CO2 laser scars. Improvement in acne scarring for NAFL with a nonablative fractional 1,550-nm erbium:glass ranges from 25% to 75% in several studies, and laser in a split-face randomized, blinded study for some patients show greater than 75% improvement. atrophic acne scarring in 8 patients. At the 3-month

The number of treatment sessions with NAFL is follow-up, the authors found that the fractional CO2

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Conclusion

A myriad of treatment options are available for the 3 atrophic acne scar types, but there is a paucity of high- quality clinical studies for many of these therapies.8 Furthermore, the studies use many disparate acne severity scores, which make comparison between them difﬁcult. In daily practice, combinations of these various therapies are used, and correct patient selection for each treatment modality is necessary to obtain optimal results.

Acknowledgments The authors thank Dr. Mitchel P. Goldman and Dr. Douglas C. Wu for providing patient photographs.

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