Chemical Reconstruction of Skin Scars (CROSS) Technique

Published on 15/03/2015 by admin

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10 Chemical Reconstruction of Skin Scars (CROSS) Technique

Sung Bin Cho, Kee Yang Chung, Kwang Hoon Lee, Jung Bock Lee

Introduction

Atrophic scars can be induced by various causes, including severely inflamed acne, chicken pox, and trauma. Among them, acne scarring is a common dermatologic condition that causes problems cosmetically and psychologically. Several modalities have been suggested to treat acne scars, including surgical techniques (punch graft, punch excision, and subcision), resurfacing techniques (dermabrasion, ablative fractional or non-fractional laser treatments, and chemical peels), autologous fat transfer, and injection of dermal fillers. However, acne scarring still remains a therapeutic challenge to dermatologists.

The term enlarged skin pore usually refers to the visible feature on the skin surface that corresponds to enlarged openings of pilosebaceous follicles. They appear as cornified cylindrical plugs, corresponding to comedones, or as empty funnel-shaped structures, which are physiologically present in all individuals, but the appearance of pores differs between individuals, and accordingly, subjective needs for treatment vary widely. Previous reports have shown variable clinical outcomes for treatments such as intense pulsed light, topical retinoic acid, oral isotretinoin, tretinoin iontophoresis, chemical peels, a 1064 nm Nd:YAG laser, a nonablative 1550 nm erbium glass fractional photothermolysis system, and an ablative carbon dioxide fractional laser.

The chemical reconstruction of skin scars (CROSS) method is a technique for the treatment of atrophic scars and enlarged pores using a sharpened wooden applicator to deeply deliver trichloroacetic acid (TCA) in higher concentration. The CROSS method is used to maximize the effects of TCA and to overcome complications such as scarring and postinflammatory hyper- and hypopigmentation, which are known to develop frequently in dark-skinned patients. The technique was developed to induce neosynthesis of dermal components such as collagen, elastin, and ground substance. This would result in dermal thickening followed by elevation of the depressed scars or narrowing of the enlarged pores. The technique basically consists of firmly pressing down an applicator soaked in TCA on the depressed atrophic acne scars and enlarged pores to produce a confluent frost. However, there are modifications to deliver the TCA in a more controlled manner and to expedite the treatment time (see Box 10.1).

Box 10.1

Key features

• Before performing CROSS, preconditioning the skin with agents such as tretinoin cream are not recommended due to the risk of unpredictable and excessive TCA penetration.

• To achieve a pronounced clinical improvement, five or more courses of CROSS treatment must be delivered at a four- to six-week intervals.

• The skin is monitored carefully until it reaches a ‘frosted’ appearance after a single application of TCA, which usually occurs within 10 seconds.

• Patient selection

Relevant history should be obtained, including any history of prior hypertrophic scarring, keloids, allergies, or herpes simplex virus infection. Before performing CROSS, preconditioning the skin with agents such as tretinoin cream are not recommended due to the risk of unpredictable and excessive TCA penetration. A history of drugs that depress adnexal glands, such as isotretinoin, is a relative contraindication to medium to deep chemical resurfacing because of the increased risk of developing hypertrophic scars. However, we believe that a drug history of isotretinoin is not a contraindication and does not influence the clinical results because CROSS spares the adjacent normal skin.

• Expected benefits

After five or six courses of treatment, about 80–85% of the patients experience good clinical responses using 65% TCA, whereas 90–95% of the patients present with good clinical responses using 100% TCA. To achieve a pronounced clinical improvement, five or more courses of CROSS treatment must be delivered at a 4–6week intervals. According to the results of an animal study, treatment using the CROSS method is more effective than simple application of TCA in activating fibroblasts in the dermis and increasing the amount of collagen. These changes were more prominent in the areas treated with a CROSS method, particularly when 100% TCA was used, than the areas treated with simple application of TCA.

Traditionally, due to higher rate of pigmentary or scarring complications in Asian skin, many dermatologists use one or two TCA applications of lower concentration, 10–30%, using a cotton-tipped applicator until even white frostings form. However, multiple, deep, and firm applications are needed to treat a single scar using the CROSS method in contrast to a single or double simple applications in the traditional method. While more effort and time are needed compared to conventional chemical resurfacing methods, the CROSS technique is being widely used due to the superior clinical results, rapid healing time, and lower complication rate.

Major side effects, such as persistent erythema, permanent hyperpigmentation, hypopigmentation, herpes simplex flare-up, scarring, or keloids, have not been reported at the treatment sites when using 65% TCA CROSS treatment. Even when 100% TCA was used, only transient side effects have been noticed; posttreatment erythema, which usually fades over 2–8 weeks, and transient postinflammatory hyperpigmentation, which spontaneously disappears in 6 weeks.

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