Fractional Laser Skin Resurfacing

November 2012 | Volume 11 | Issue 11 | Original Article | 1274 | Copyright © 2012

Macrene R. Alexiades-Armenakas MD PhD,a,b Jeffrey S. Dover MD,a-c and Kenneth A. Arndt MDc-e

Abstract

Laser skin resurfacing (LSR) has evolved over the past 2 decades from traditional ablative to fractional nonablative and fractional ablative resurfacing. Traditional ablative LSR was highly effective in reducing rhytides, photoaging, and acne scarring but was associated with significant side effects and complications. In contrast, nonablative LSR was very safe but failed to deliver consistent clinical improvement. Fractional LSR has achieved the middle ground; it combined the efficacy of traditional LSR with the safety of nonablative modalities. The first fractional laser was a nonablative erbium-doped yttrium aluminum garnet (Er:YAG) laser that produced microscopic columns of thermal injury in the epidermis and upper dermis. Heralding an entirely new concept of laser energy delivery, it delivered the laser beam in microarrays. It resulted in microscopic columns of treated tissue and intervening areas of untreated skin, which yielded rapid reepithelialization. Fractional delivery was quickly applied to ablative wavelengths such as carbon dioxide, Er:YAG, and yttrium scandium gallium garnet (2,790 nm), providing more significant clinical outcomes. Adjustable laser parameters, including power, pitch, dwell time, and spot density, allowed for precise determination of percent surface area, affected penetration depth, and clinical recovery time and efficacy. Fractional LSR has been a significant advance to the laser field, striking the balance between safety and efficacy.

J Drugs Dermatol. 2012;11(11):1274-1287.

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INTRODUCTION

Procedural treatments for rhytides, photoaging, and acne scars have ranged from aggressive and highly effective to conservative with minimal efficacy. Traditional or standard ablative laser skin resurfacing (LSR) with carbon dioxide (CO2) and erbium-doped yttrium aluminum garnet (Er:YAG) lasers were highly effective in reducing rhytides, photoaging, and acne scars but were associated with significant side effects and complications.1 Dermabrasion and chemical peeling were also very effective, but their side effects and complication rates were high.2,3 In an effort to increase safety and decrease side effects and complications, nonablative lasers and light-based devices, which neither ablate nor vaporize tissue, were developed. Nonablative technologies targeted chromophores in the epidermis and dermis and induced dermal thermal injury without epidermal wounding.1 Although nonablative modalities proved to be very safe, requiring no recovery time and rarely causing side effects or complications, they provided low or inconsistent efficacy, particularly in the reduction of rhytids.1

Fractional Laser Resurfacing

Most recently, a resolution of this therapeutic challenge was developed with fractional LSR, which treated a fraction of the skin surface with microscopic arrays of laser- or light-mediated effects at higher dosages than nonablative LSR, but with intervening zones of untreated skin for rapid recovery and excellent safety.4 By targeting microscopic spots of the skin with individual microbeams of laser light, and sparing skin and stem cells in between, rapid recovery and increased safety were achieved (Figure 1). Arrays of microscopic columns of focal areas of energy-mediated effects were created, such as to focally target a fraction of the skin with many separate microbeams of laser or light.4 The microscopic columns were termed microthermal treatment zones (MTZs), extending from the epidermal layer into the dermis at varying depths, and determined by several parameters, including laser energy output and spot size.4 The categories of fractional LSR included nonablative fractional LSR, which neither ablated nor vaporized tissue, but caused microcolumns of thermal injury in the dermis with a relatively intact superimposed epidermal layer left in place. The second category was the ablative type, which ablated or vaporized microcolumns of epidermis and dermis. Of the 2 types of fractional lasers, nonablative and ablative, the latter yielded higher efficacy with a small sacrifice in safety.

Fractional Nonablative Resurfacing

Technologic Properties
The first fractional laser was the nonablative 1,550-nm Er-doped fiber laser delivering 2,000 MTZs per cm2 (Fraxel, Solta, Hayward, CA; formerly Reliant Technologies).4 Microscopic laser spots were scanned across the skin through an optical scanner that laid down an array onto the skin. As the first attempt at implementing the fractional concept, the new technology, while clever, was cumbersome. It used an optical scanner that originally required the application of a blue dye to the patient's skin to facilitate tracking. Even with the application of topical anesthesia and the use of cool air, many found it unreasonably uncomfortable (Figure 2).

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