Secondary Logo

Journal Logo

Prevention of postoperative scars in dark skin types using a fractional carbon dioxide laser: a clinical and histopathological split-scar study

Darwish, Abdou M.a; Abdel-Razek, Wael H.b; Hassan, Khaled M.a; Moftah, Noha H.b; Abdel-Aziz, Mohamed F.a

Journal of the Egyptian Women's Dermatologic Society: May 2017 - Volume 14 - Issue 2 - p 137–145
doi: 10.1097/01.EWX.0000508418.56653.5e
Original articles
Free

Background Treatment of mature postoperative scars is frustrating for both patients and doctors. Accordingly, a fractional carbon dioxide (CO2) laser could be used during the early postoperative period as a prophylaxis against scarring. However, its safety in patients with dark skin types and the histopathological changes during early treatment remain controversial.

Objective To evaluate the efficacy and safety of a fractional CO2 laser in the prevention of postoperative scars in patients with dark skin types, with assessment of its histopathological effect.

Patients and methods Six fractional CO2 laser sessions were performed at 2-week intervals on one part of early postoperative wounds of 20 patients in comparison with other untreated parts 3 months after the last session using the Vancouver scar scale (VSS). Using histopathological and computerized morphometric analysis, morphological changes in collagen and elastic fibers were assessed and a quantitative evaluation of epidermal thickness was performed 3 months after the last session.

Results In treated parts, there was a significant improvement in pliability, height, and total VSS score (P≤0.05), with no significant difference in vascularity and pigmentation (>0.05), compared with untreated parts. Hypertrophic scars appeared in untreated parts of 40% of the patients. Histopathologically, collagen fibers were fine and well organized in treated parts (75%); however, they were arranged as fairly thickened hyaline bundles (75%), either disorganized (35%) or randomly, within nodules with some parallel fibers to the epidermis (40%) in untreated parts. Dense elastotic tissues, in untreated biopsies (80%), became less with the appearance of fine and well-organized fibers in treated biopsies (70%). There was a significant increase in the epidermal thickness of treated parts compared with untreated ones (P<0.05).

Conclusion A fractional CO2 laser was effective, tolerable, and safe in the prevention of postoperative scars, especially the hypertrophic type, in patients with dark skin types. Histopathologically, remodeling of collagen and elastic fibers occurred with an increase in the epidermal thickness after its use.

Department of aPlastic and Reconstructive Surgery

bDepartment of Dermatology, STD’s and Andrology, Minia University, Minia, Egypt

Correspondence to Noha H. Moftah, MD, Department of Dermatology, STDs and Andrology, Minia University, 191 El-Horya Street, Minia, Egypt Tel: +20 122 219 0267; e-mails: nohamoftah2013@yahoo.com, nohamoftah1971@gmail.com

Received October 13, 2016

Accepted October 28, 2016

Back to Top | Article Outline

Introduction

Patients undergo various kinds of surgery for therapeutic or cosmetic reasons 1. Of these, ~15% have excessive scar formation, especially in populations with Fitzpatrick skin type III or higher skin pigmentation 2. However, surgical reconstruction can result in disfiguring of these postoperative scars, which causes considerable distress to patients 1. Accordingly, various types of lasers have been used to treat scars 3.

Ablative lasers used for skin resurfacing, such as the carbon dioxide (CO2) and erbium-doped yttrium aluminum garnet (Er:YAG), lead to the greatest improvement in scars with a single treatment 3. However, a long downtime and a high incidence of adverse effects have limited its use 4. Moreover, it can destabilize a healing tissue bed or disrupt the epidermal barrier before sealing of the incision. Therefore, the optimal time for treatment is during the scar formation phase. Meanwhile, nonablative pulsed or fractionated lasers place minimal mechanical stress on tissues, making an argument for earlier treatment 5.

A fractional ablative 10 600 nm CO2 laser has gained popularity in the treatment of scars because it targets the tissue producing microscopic thermal zones of injury surrounded by areas of untreated skin and intact epidermis 6,7, enabling much deeper treatment with fast healing and reduction of side effects 4, which in turn stimulates progressive collagen remodeling 6.

A fractional ablative CO2 laser has been used for mature scars for at least 2 months in most previous studies 1. Meanwhile, few reports have focused on early treatment of postoperative scars using fractional CO21,8 to prevent or at least reduce the apparition of scars 9. Meanwhile, on review of the literature, there were no studies discussing the safety of a fractional ablative CO2 laser and the treatment guidelines in patients with dark skin types. Moreover, there were no evidence-based publications discussing its effect at the histopathological level. Accordingly, the aim of the present study was to evaluate the clinical efficacy and safety of a fractional ablative CO2 laser in the prevention of postoperative scars in patients with dark skin types with assessment of its histopathological effect.

Back to Top | Article Outline

Patients and methods

Patients

This study included 20 patients with early postoperative facial wounds of 2–3 weeks’ duration. These patients were recruited from the out-patient Clinics of Dermatology and Plastic and Reconstructive Surgery departments, Minia University. An informed written consent was obtained from each patient for treatment and to obtain skin biopsies. The study was approved by the Committee for Postgraduate Studies and Research of Minia University.

Patients with Fitzpatrick skin types III or more were included in this study. The patients had not been treated with topical and systemic medication or laser before starting the study. Patients with a history of keloidal tendency, isotretinoin use, pregnancy, immunosuppressive drug use, and postoperative infection of the wound were excluded from the study.

Back to Top | Article Outline

Treatment protocol

One part of the wound was subjected to six sessions using a fractional CO2 laser [Multixel, DS-40U (B), 10 600 nm; Deashin Enterprise (D.S.E) group, Seoul, Korea]; however, the other part was left untreated, serving as a control. A 2.5% lidocaine/prilocaine cream (EMLA cream; AstraZeneca AB, Södertälje, Sweden) was used as a topical anesthetic and applied to the treated areas under occlusion 1 h before treatment. Three passes in each session, with a 2-week interval between sessions 1, were performed. Laser parameters were established according to the device manufacturer using a fluence of 30 mJ, depth of level 3 (1.5–2 mm), a spot density of 100 dots/cm2, and a pulse duration of 900 ms. The scanner size was adjusted according to the length and width of the scar, with an increase in its size by 2 mm all around the scar.

After treatment, the treated areas were cooled with ice packs for 10 min to protect the spared epidermis. Patients were instructed to use a moisturizer to both the treated and the untreated areas for a week after the treatment with application of a full-spectrum sunscreen (>SPF 50) in between sessions up to the clinical assessment. Photographs were taken before, at every laser session, and after 3 months of the last session.

Back to Top | Article Outline

Clinical assessment of the response

Assessment of the response was performed 3 months after the last laser session through grading of both treated and untreated parts by two blinded independent dermatologists using the Vancouver scar scale (VSS), where the average of their evaluation was calculated. This scale included pigmentation (0=normal, 1=hypopigmented, 2=mixed pigmentation and 3=hyperpigmented), pliability (0=normal, 1=supple, 2=yielding, 3=firm, 4=ropes and 5=contracture), height (0=flat, 1 is <2 mm, 2 is 2–5 mm, and 3 is ≥5 mm), and vascularity (0=normal, 1=pink, 2=red and 3=purple). The score for each parameter was assessed separately and all four scores were added and averaged 10. The scores range from 0 to 14. The maximum score is 14, indicating the worst result. The minimum score is 0, indicating the best result, that is, normal skin.

Three months after the treatment sessions, the patients were surveyed about their overall level of satisfaction using quartile-grading scale as follows: very satisfied, satisfied, slightly satisfied, and unsatisfied 1. The patients were asked about sequels and side effects observed during every session and after 3 months of the last laser session, namely, erythema, edema, pain, crusts, hyperpigmentation, hypopigmentation, and hypertrophic scars.

Back to Top | Article Outline

Skin biopsy

Skin biopsy specimens were taken 3 months after the last laser session, using 2-mm punch probes, from both treated and untreated parts of the scar. All biopsies were fixed in 10% buffered formalin, embedded in paraffin, and sectioned into 5 µm thick sections. These sections were subjected to a histopathological examination using Hematoxylin and Eosin, Masson trichrome, and Orcein stains. A light microscope [Accu-Scope # 3025 five headed (A3025-5); Olympus, Tokyo, Japan] with a built-in camera (digital camera E-330 SLR; Olympus) was used to examine and photograph the sections.

Back to Top | Article Outline

Histopathological assessment of the response

The histopathological evaluation of both treated and untreated parts, 3 months after the last session, included examination of the epidermis (normal, flattened or hyperplastic) and the dermis [collagen; site (papillary or reticular), arrangement (disorganized, nodules or parallel to the skin surface) and thickness (thickened or fine fibers) of elastin, and site (papillary or reticular) and appearance (thickened elastotic tissues or fine fibers)].

Back to Top | Article Outline

Histometric evaluation of epidermal thickness

A computer-assisted program (analySIS Five; Olympus Soft Imaging Solutions GmbH, Munster, Germany) was used to measure the epidermal thickness in hematoxylin and eosin-stained sections from the two biopsy specimens 3 months after the last laser session. The mean epidermal thickness was determined after measuring the distance between the outermost surface of the epidermis excluding the stratum corneum and the dermoepidermal junction at five points through the entire length of the three examined sections.

Back to Top | Article Outline

Statistical analysis

Data were statistically analyzed using SPSS for Windows (version 16.0.1; SPSS Inc., Chicago, Illinois, USA). Quantitative data were expressed as range and mean±SD, whereas qualitative data were expressed as number and percent. Statistical analysis included the Mann–Whitney test for nonparametric quantitative data and Chi-square test for qualitative data. Significance was expressed in terms of the P-value, which was considered significant when it was 0.05 or less.

Back to Top | Article Outline

Results

The study included 20 patients [eight females (40%) and 12 males (60%)] with early facial postoperative wounds. The age of these patients ranged from 10 to 51 years, with a mean of 22.45±11.46 years. In terms of Fitzpatrick skin types, three (15%), 15 (75%), and two (10%) patients had skin types III, IV, and V, respectively.

Back to Top | Article Outline

Clinical assessment

Vancouver scar scale

Three months after the last laser session, there was a significant improvement in pliability, height, and the total VSS score (P≤0.05) in treated parts, with no significant difference in vascularity and pigmentation (>0.05) compared with untreated parts (Fig. 1 and Table 1).

Figure 1

Figure 1

Table 1

Table 1

Back to Top | Article Outline

Patients’ satisfaction

The patients themselves assessed the improvement in the treated part as follows: very satisfied in 10 (50%) patients, satisfied in eight (40%) patients, and slightly satisfied in two (10%) patients. For the control part, two (10%) patients were satisfied, seven (35%) patients were slightly satisfied, and 11 (55%) patients were unsatisfied. Accordingly, there was significant patient satisfaction in the treated parts compared with the untreated ones (<0.001).

Back to Top | Article Outline

Safety and tolerability

Post-treatment side effects after each session included erythema, edema, and dark crusts, which resolved within 7–10 days after treatment with removal of the dark crusts. There was mild pain during the laser session, which subsided shortly after the session in 18 (90%) out of 20 cases and lasted several hours to 2 days in the remaining two (10%) cases. Hyperpigmentation and hypopigmentation occurred in two (10%) patients and one (5%) patient, respectively, after the last session and disappeared 3 months after the last laser session. No side effects were noted 3 months after the last session in the treated parts. However, only in the untreated areas, hypertrophic scars were apparent in eight (40%) patients (Fig. 1).

Back to Top | Article Outline

Histopathological evaluation

Epidermis

In untreated parts, flattening of the epidermis was prominent in 18 (90%) patients. Meanwhile, treated parts showed a normal epidermis with well-developed rete ridges in 15 (75%) patients (Figs 2–4).

Figure 2

Figure 2

Figure 3

Figure 3

Figure 4

Figure 4

Back to Top | Article Outline

Collagen fibers (Masson trichrome)

There was a significant improvement in collagen fibers (0.002), which became fine and well organized and parallel to the epidermis with decreased interfibrillary spaces in the entire dermis in the treated parts of 15 (75%) patients and the untreated parts in five (25%) patients. The rest of the untreated parts (15 biopsies, 75%) showed fairly thickened hyaline bundles, either disorganized (seven biopsies, 35%) with increased interfibrillary spaces in the entire dermis or randomly within nodules (cigar-shaped) in the middle and deep dermis with some parallel fibers to the epidermis outside the nodule in the superficial dermis (eight biopsies, 40%) (Figs 2 and 3, Table 2).

Table 2

Table 2

Back to Top | Article Outline

Elastic fibers (Orcein stain)

There was dense elastotic material throughout the entire dermis in 16 (80%) untreated parts and six (30%) treated parts. Meanwhile, the treated areas of 14 (70%) patients showed a significant improvement (0.001) with less elastotic material and appearance of newly synthesized elastic fibers, which became finer and well organized (Fig. 4 and Table 2).

Back to Top | Article Outline

Histometric evaluation of epidermal thickness

After treatment, the epidermal thickness of the treated part ranged from 65.19 to 79.99 (mean, 70.81±3.32 µm), with a significant increase compared with the untreated part (range, 46.13–62.99; mean, 55.15±4.76; P<0.001) (Fig. 5 and Table 2).

Figure 5

Figure 5

Back to Top | Article Outline

Discussion

Skin injuries because of trauma or surgery are relatively common, and patients are very concerned about scar formation. Although normal wound healing and scar remodeling continue to occur until 2–3 years after surgery 11, many patients prefer treatment of scars as soon as possible 1, especially when they are located on visible sites 7. Moreover, focus has recently been directed toward early laser treatment for scar prevention to yield better cosmetic results 1.

Specifically, early surgical scars have been treated successfully using a pulsed dye laser (PDL) on the day of suture removal 12, a 1550-nm fractional Erbium glass laser on new thyroidectomy scars 13, fractional ablative 2940 nm Er-YAG in combination with PDL 14, and fractional ablative 10 600 nm CO21,7,8. Meanwhile, on review of the literature, there were no studies discussing the safety of a fractional ablative CO2 laser and the treatment guidelines in patients with dark skin types. Moreover, there were no evidence-based publications discussing its effect at the histopathological level in terms of tissue remodeling during the early postoperative period. Accordingly, the aim of the present study was to assess the clinical efficacy and safety of a fractional ablative CO2 laser in the prevention of postoperative scars in dark skin types, with evaluation of its histopathological effect.

In the present study, a fractional ablative CO2 laser was used during the early postoperative period (2–3 weeks after surgery) on one part of the wound, leaving the rest untreated, serving as a control. We chose this timing of treatment because re-epithelialization would be complete at this point and treatment initiation at this point of time was shown to yield positive results in previous reports 1,8. Moreover, this timing occurred after the end of the inflammation phase of wound healing (4–6 days) and was either in the late proliferative phase of wound healing (4–14 days), where fibroblasts migrate into the wound site and start producing collagen 15, or in the early remodeling phase, which starts roughly at day 8 after the injury and lasts for over a year 16, and during which the extracellular matrix is dynamic, balanced between synthesis and degradation 17.

Six fractional CO2 laser sessions, at 2-week intervals 1, were performed using a pulse energy of 30 mJ. Meanwhile, Lee et al.1 performed two sessions using a fractional CO2 laser, but with a high pulse energy of 80 mJ. Moreover, Jung et al.8 performed one session of fractional CO2 with a pulse energy of 50 mJ on patients with thyroidectomy scars. These previous two studies were carried out on Asian patients with Fitzpatrick skin types III and IV. Meanwhile, this study applied more number of sessions with low fluence on facial wounds of Egyptian patients with Fitzpatrick skin types III to V to ensure efficacy while avoiding prolonged erythema and permanent pigmentation as Egypt is characterized by a sunny climate. Moreover, the scanner size was adjusted according to the length and width of the scar, with an increase in its size about 2 mm all around the scar to stimulate collagen remodeling from healthy skin around wounds.

After 3 months of the last laser session, there was a significant improvement in the total VSS score of the treated parts in addition to significant patient satisfaction compared with the untreated ones. This is in agreement with Lee et al.1 Moreover, Hong et al.7 and Jung et al.8 found a significant decrease in the mean total VSS after treatment with a fractional CO2 laser compared with the baseline state only without involvement of the control untreated part.

In the subset analysis of VSS, there was a significant improvement in pliability and height scores in treated parts, with no significant difference in vascularity and pigmentation compared with the untreated parts. This is in agreement with Lee et al.1. Meanwhile, Kim et al.14, who used both PDL and an Er-YAG laser, found that the best response was found in pliability. Meanwhile, Hong et al.7 and Jung et al.8, using fractional CO2 in early scars, reported a total VSS score without describing its four components separately.

A fractional ablative CO2 laser enables treatment of scars with fewer side effects and less downtime than traditional CO2 lasers 1,6,8,18. This was evident in the present study, where post-treatment mild pain, erythema, edema, and dark crusts were transient and resolved within 7–10 days after each session with removal of the dark crusts. The pain subsided shortly after the session in 90% of the patients and lasted several hours to 2 days in 10% of the patients.

In terms of the pigmentation abnormalities detected in treated parts of the scars in this study, hyperpigmentation and hypopigmentation were observed in two (10%) patients and one (5%) patient, respectively, after the last session and disappeared spontaneously 3 months after the last session. This is similar to Lee et al.1 and Jung et al.8, who observed transient post-treatment hyperpigmentation in one patient and two patients, respectively, on the treated area of the scar. Meanwhile, Chapas et al.19 detected permanent delayed-onset hypopigmentation, which can markedly detract from overall clinical outcomes.

In this study, hypertrophic scars were apparent in the untreated parts only in eight (40%) patients. Meanwhile, Lee et al. 1 observed hypertrophic scarring in one patient on both treated and untreated parts of the scar. Therefore, it is difficult to state that the fractional laser was the sole cause of the scar elevation, although the treated side became thicker and wider than the untreated side, and thus the risk of developing hypertrophic scarring after fractional CO2 treatment cannot be excluded. They recommended using low power (<80 mJ).

Generally, collagen fibers form a network with elastic fibers resulting in a highly ordered structure in the dermis. Meanwhile, collagen is considered the main structural and most abundant extracellular matrix component of the dermis, and plays an essential role in the strength and elasticity of healthy skin and scar tissue 20. In contrast, elastic fibers compose only 1–2% of the dermis and they are critical to the ability of the skin to stretch and recoil 21. Therefore, it is important to study the remodeling of collagen and elastic fibers during wound healing after early laser therapy.

In this study, there was a significant improvement in collagen fibers, which became fine and well organized and parallel to the epidermis with decreased interfibrillary spaces in the entire dermis in the treated parts of 15 (75%) patients and the untreated parts in five (25%) patients.

The rest of the untreated parts (15 biopsies, 75%) showed fairly thickened hyaline bundles, either disorganized (seven biopsies, 35%) with increased interfibrillary spaces in the entire dermis or randomly within nodules (cigar-shaped) in the middle and deep dermis, with some parallel fibers to the epidermis outside the nodule in the superficial dermis (eight biopsies from hypertrophic scars, 40%). On review of the literature, Oliae et al.22 described the scar histopathologically after 4 months of incision without treatment; the collagen fibers became thicker and denser. Moreover, the state of collagen in untreated hypertrophic scars in this study was similar to that described by Linares and Larson 23, Lee et al.24, and Verhaegen et al.25.

For the elastic fibers, dense elastotic material was found throughout the entire dermis in 16 (80%) untreated parts and six (30%) treated parts. Meanwhile, the treated areas of 14 (70%) patients showed a significant improvement, with less elastotic material and appearance of newly synthesized elastic fibers, which became finer and well organized.

Accordingly, it is important to differentiate between normal healing and abnormal scarring. Normal healing occurs when the newly synthesized collagen is not excessive 26 and organized in a well-organized fine network 17 as a natural process of the remodeling stage of wound healing and the skin has sufficient elasticity not to restrict movements. Accordingly, areas of normal scarring should not be distinct from the surrounding skin 26.

For the epidermis, there was a significant increase in the mean epidermal thickness of the treated parts compared with the untreated parts. Accordingly, the interaction between epidermal keratinocytes and dermal fibroblasts could play an important role in regulating tissue homeostasis and processing scar formation 27.

To the best of our knowledge, this study was the first to examine the state of remodeling of collagen and elastin and epidermal thickness following an early intervention of wound during the early postoperative period.

Some authors have hypothesized about how the laser affects the scar-remodeling phase after trauma or surgery. One hypothesis involves thermal injury to the dermis, where neocollagenesis and remodeling occur 8. Other theories focus on the stimulation of growth factors and cytokines by lasers 28 or the initiation of collagen signaling cascades 29. Meanwhile, earlier intervention can theoretically alter the inflammatory phase of wound healing and alter fibroblast migration, leading to a reduction in the appearance of scars 5.

Back to Top | Article Outline

Conclusion

The fractional CO2 laser was effective, tolerable, and safe in the prevention of postoperative scars, especially hypertrophic types, in dark-skinned patients. Histologically, the collagen fibers became fine and well organized, with rectification of the elastic fiber degeneration in addition to increased epidermal thickness. Accordingly, fractional CO2 could act through remodeling of the dermis to activate deposition of its normal architecture (collagen and elastin) in addition to increasing the epidermal thickness.

Back to Top | Article Outline

Conflicts of interest

There are no conflicts of interest.

Back to Top | Article Outline

References

1. Lee SH, Zheng Z, Roh MR. Early postoperative treatment of surgical scars using a fractional carbon dioxide laser: a split-scar, evaluator-blinded study. Dermatol Surg 2013; 39:1190–1196.
2. Monstrey S, Middelkoop E, Vranckx JJ, Bassetto F, Ziegler UE, Meaume S, et al. Updated scar management practical guidelines: non-invasive and invasive measures. J Plast Reconstr Aesthet Surg 2014; 67:1017–1025.
3. Alster T, Zaulyanov L. Laser scar revision: a review. Dermatol Surg 2007; 33:131–140.
4. Majid I, Imran S. Efficacy and safety of fractional CO2 laser resurfacing in non-hypertrophic traumatic and burn scars. J Cutan Aesthet Surg 2015; 8:159–164.
5. Sullivan T, Smith J, Kermode J, McIver E, Courtemanche DJ. Rating the burn scar. Burn Care Rehabil 1990; 11:256–260.
6. Manstein D, Herron GS, Sink RK, Tanner H, Anderson RR. Fractional photothermolysis: a new concept for cutaneous remodeling using microscopic patterns of thermal injury. Lasers Surg Med 2004; 34:426–438.
7. Hong SC, Park ES, Kim YB, Nam SM. Effects of minimizing scar formation by early fractional CO2 laser resurfacing. Arch Aesthetic Plast Surg 2014; 20:109–113.
8. Jung JY, Jeong JJ, Roh HJ, Cho SH, Chung KY, Lee WJ, et al. Early postoperative treatment of thyroidectomy scars using a fractional carbon dioxide laser. Dermatol Surg 2011; 37:217–223.
9. Capon A, Souil E, Gauthier B, Sumian C, Bachelet M, Buys B, et al. Laser assisted skin closure (LASC) by using a 815-nm diode laser system accelerates and improves wound healing. Lasers Surg Med 2001; 28:168–175.
10. Baryza MJ, Baryza GA. The Vancouver Scar Scale: an administration tool and its interrater reliability. J Burn Care Rehabil 1995; 16:535–538.
11. Atiyeh BS. Nonsurgical management of hypertrophic scars: evidence-based therapies, standard practices and emerging methods. Aesthetic Plast Surg 2007; 31:468–494.
12. Nouri K, Jimenez GP, Harrison-Balestra C, Elgart GW. 585-nm pulsed dye laser in the treatment of surgical scars starting on the suture removal day. Dermatol Surg 2003; 29:65–73.
13. Choe JH, Park YL, Kim BJ, Kim MN, Rho NK, Park BS, et al. Prevention of thyroidectomy scar using a new 1550-nm fractional erbium-glass laser. Dermatol Surg 2009; 35:1199–1205.
14. Kim HS, Kim BJ, Lee JY, Kim HO, Park YM. Effect of the 595-nm pulsed dye laser and ablative 2940-nm Er:YAG fractional laser on fresh surgical scars: an uncontrolled pilot study. J Cosmet Laser Ther 2011; 13:176–179.
15. Shin D, Minn KW. The effect of myofibroblast on contracture of hypertrophic scar. Plast Reconstr Surg 2004; 113:633–640.
16. Janis JE, Kwon RK, Lalonde DH. A practical guide to wound healing. Plast Reconstr Surg 2010; 125:230e–244e.
17. Bond JS, Duncan JA, Sattar A, Boanas A, Mason T, O’Kane S, et al. Maturation of the human scar: an observational study. Plast Reconstr Surg 2008; 121:1650–1658.
18. Lapidoth M, Halachmi S, Cohen S, Amitai DB. Fractional CO2 laser in the treatment of facial scars in children. Lasers Med Sci 2014; 29:855–857.
19. Chapas AM, Brightman L, Sukal S, Hale E, Daniel D, Bernstein LJ, et al. Successful treatment of acneiform scarring with CO2 ablative fractional resurfacing. Lasers Surg Med 2008; 40:381–386.
20. Bernstein EF, Andersen D, Zelickson BD. Laser resurfacing for dermal photo-aging. Clin Plast Surg 2000; 27:221–240.
21. Uitto J, Olsen DR, Fazio MJ. Extracellular matrix of the skin: 50 years of progress. J Invest Dermatol 1989; 92 (Suppl):61S–77S.
22. Oliaei S, Nelson JS, Fitzpatrick R, Wong BJ. Laser treatment of scars. Facial Plast Surg 2012; 28:518–524.
23. Linares HA, Larson DL. Early differential diagnosis between hypertrophic and nonhypertrophic healing. J Invest Dermatol 1974; 62:514–516.
24. Lee JY, Yang CC, Chao SC, Wong TW. Histopathological differential diagnosis of keloid and hypertrophic scar. Am J Dermatopathol 2004; 26:379–384.
25. Verhaegen PD, van Zuijlen PP, Pennings NM, van Marle J, Niessen FB, van der Horst CM, et al. Differences in collagen architecture between keloid, hypertrophic scar, normotrophic scar, and normal skin: an objective histopathological analysis. Wound Repair Regen 2009; 17:649–656.
26. Carney SA. Hypertrophic scar formation after skin injury. J Wound Care 1993; 2:299–302.
27. Köse O, Waseem A. Keloids and hypertrophic scars: are they two different sides of the same coin? Dermatol Surg 2008; 34:336–346.
28. Alster TS, Tanzi EL, Lazarus M. The use of fractional laser photothermolysis for the treatment of atrophic scars. Dermatol Surg 2007; 33:295–299.
29. Alster TS, Handrick C. Laser treatment of hypertrophic scars, keloids and striae. Semin Cutan Med Surg 2000; 19:287–292.
Keywords:

CO2 laser; fractional; postoperative; scar

© 2017 Egyptian Women's Dermatologic Society