In fractional photothermolysis, a regular array of pixelated light energy creates focal areas of epidermal and dermal tissue damage or microthermal treatment zones (MTZ) (Fig. 6.1). Since its inception, several different lasers have been developed to take advantage of this technological advance. Each laser has parameters that can modify the density, depth, and size of the vertical columns of MTZs. The individual wounds created by FP are surrounded by healthy tissue resulting in a much quicker healing process when compared with traditional ablative skin resurfacing. This targeted damage with MTZ is hypothesized to stimulate neocollagenesis and collagen remodeling leading to the clinical improvements seen in scarring and photoaging. In the original study by Manstein et al., the histologic changes seen after NAFR were elegantly described. Immediately following treatment, lactate dehydrogenase (LDH) viability staining showed both epidermal and dermal cell necrosis within a sharply defined column correlating with the MTZ. There was continued loss of dermal cell viability 24 hours after treatment, but via a mechanism of keratinocyte migration, the epidermal defect had been repaired. One week after treatment, individual MTZs were still evident by LDH staining, but after 3 months there was no histologic evidence of loss of cell viability. Water serves as the target chromophore allowing for thermal damage to epidermal keratinocytes and collagen.

Figure 6.1 Diagram showing the differences between traditional ablative, non-ablative fractional, and ablative fractional resurfacing. With the fractional laser technology, microthermal treatment zones are created with intervening islands of unaffected tissue. Healing time is significantly less, and the energy can safely reach deeper into the dermis.

Hantash and colleagues demonstrated a unique mechanism of tissue repair with fractional photothermolysis. In 2006, they demonstrated, using an elastin antibody, that damaged dermal content was incorporated into columns of microscopic epidermal necrotic debris (MEND) and shuttled up through the epidermis and extruded in a process of transepidermal elimination. This mechanism, which had not been described with previous laser technologies, explains the elimination of altered collagen in photoaging and scars and was also hypothesized to provide novel treatment strategies for pigmentary disorders like melasma as well as depositional diseases like amyloid and mucinoses.

Epidemiology

According to the American Society for Plastic Surgery statistics, which provides a comprehensive estimate on the total number of cosmetic procedures performed in the United States, minimally invasive cosmetic procedures have increased by more than 100% since 2000. In 2010, over 300 000 non-ablative laser skin resurfacing procedures were performed with the majority done on females.

Equipment

As the technology of fractional photothermolysis continues to evolve, new devices continually come to market. A list of currently available NAFR systems is given in Table 6.1. The table is not comprehensive and, as one can imagine, the devices will change constantly. This section will provide a brief description of a few of the more commonly used devices.

Table 6.1 Non-ablative fractional lasers

The original non-ablative fractional resurfacing system described by Manstein featured a scanning handpiece with a 1500 nm wavelength. The updated, currently available model, the Fraxel re:store (Solta Medical, Hayward, CA), employs a 1550 nm erbium glass laser. The device has tunable settings to adjust the density of the MTZs and energy depending on the treatment. Density can be varied to treat anywhere from 5 to 48% while energy settings can be adjusted to control depth of penetration from 300 to 1400 µm. Most of the studies available on non-ablative fractionated lasers are based on this device.

Solta Medical’s newest addition, the Fraxel Dual, couples the 1550 nm erbium laser with a 1927 nm thulium fiber laser in one platform. The thulium laser provides a more superficial treatment option and better addresses dyspigmentation while the 1550 nm penetrates deeper to stimulate collagen remodeling. The system increases flexibility, allowing the practitioner to switch between the two lasers to tailor treatment accordingly. Parameters can be adjusted similarly to the Fraxel re:store. Cooling is also built in with the Fraxel Dual.

Palomar Medical Technologies (Burlington, MA) offers an intense pulsed light platform with individual handpieces that attach to a single unit to cover a wide range of uses. The Lux1440 and Lux1540 handpieces provide two wavelength options (1440 and 1550 nm) for fractional non-ablative photothermolysis. In addition, the company has developed a new XD Microlens for their non-ablative laser handpieces. In their study, the company claims that, as the dermis is compressed by the optical pins on the handpiece, the pins are brought closer to deeper targets and the interstitial water is displaced from the dermal–epidermal junction into the surrounding spaces. With less water to absorb, scattering of the laser light is reduced enabling increased absorption of the light by deeper targets.

The Affirm (Cynosure, Inc., Westford, MA) is a 1440 nm Nd : YAG laser device that utilizes a proprietary Combined Apex Pulse (CAP) technology. The technology creates columns of coagulated tissue surrounded by uncoagulated tissue columns, which purportedly improves treatment efficacy. The Affirm uses a stamping handpiece with two spot sizes and energies that penetrate up to 300 µm in depth. A recent advance has been the addition of their multiplex technology, which stacks a 1320 nm wavelength with the 1440 nm system, allowing for penetration down to 1000–3000 µm.

Applications

While NAFR is currently approved by the US Food and Drug Administration for the treatment of benign epidermal pigmented lesions, periorbital rhytides, skin resurfacing, melasma, acne and surgical scars, actinic keratoses, and striae, it has been reported to be used in many other clinical settings (Box 6.1).

Box 6.1

Clinical indications for non-ablative fractional resurfacing

Photoaging

Scarring (atrophic, hypertrophic, hypopigmented)

Disorders of pigmentation (melasma, nevus of Ota, drug-induced pigmentation)

Poikiloderma of Civatte

Premalignant conditions (actinic keratoses, disseminated superficial actinic porokeratosis)

Striae distensae

Vascular disorders (telangiectatic matting, residual hemangioma)

Photoaging

With their seminal study in 2004 using a prototype non-ablative fractional resurfacing device, Manstein and colleagues first demonstrated the clinical effectiveness of fractional photothermolysis by showing improvement in periorbital rhytides. Three months after four treatments with the fractionated device, 34% of patients had moderate to significant improvements and 47% had improvement in texture as rated by blinded investigators. Overall, 96% were noted to be ‘better’ post-treatment. The skin tightening seen after non-ablative fractional resurfacing is similar to ablative resurfacing with tightening within the first week after treatment, apparent relaxation at 1 month, and retightening at 3 months (Case study 1).

Case Study 1

The right patient

A 58-year-old Caucasian male with mild rhytides and mild to moderate photodamage with scattered facial lentigines presents for consultation. You recommend a series of non-ablative fractional resurfacing laser procedures. Six months after the sixth laser procedure, you see the patient back in follow-up. He is delighted with his improvement in both texture and skin tone and subsequently refers a couple of his friends to see you.

The above patient is the ideal patient for non-ablative fractional resurfacing. These results are typical of the improvement we see in our patients when selected appropriately.

Subsequent reports have confirmed the efficacy of NAFR beyond just periorbital lines. Wanner and colleagues showed statistically significant improvement in photodamage of both facial and non-facial sites with 73% of patients improving at least 50%. In 2006, Geronemus also reported his experience with fractional photothermolysis, finding it to be effective in treating mild to moderate rhytides. Figures 6.2 and 6.3 show typical improvement in rhytides and pigmentation after treatment with non-ablative fractional resurfacing. For deeper rhytides, such as the vertical lines of the upper lip, improvement is also seen but not nearly to the same degree as in ablative approaches.

Figure 6.2 Improvement in moderate rhytides 1 month after two treatments with Fraxel 1927 nm.

(Photo courtesy of Solta Medical.)

Figure 6.3 Improvement in rhytides and dyspigmentation 1 month after three treatments with Fraxel re:store.

(Photo courtesy of Solta Medical.)

NAFR is also considered to be an effective and safe treatment modality for photoaging off the face including the neck, chest, arms, hands (Fig. 6.4), legs, and feet. These body sites are typically very challenging to treat with other treatment modalities given either increased risks of complications (e.g. scarring) associated with ablative technologies or lack of efficacy that has been previously observed with other non-ablative devices. Jih et al reported statistically significant improvement in pigmentation, roughness, and wrinkling of the hands in ten patients treated with non-ablative fractional resurfacing. In our experience, we have found NAFR to be very safe when settings are adjusted accordingly.

Figure 6.4 Improvement in rhytides and dyspigmentation of the hands 1 month after two treatments with Fraxel re:store.

(Photo courtesy of Solta Medical.)

Scarring

Scarring can induce a tremendous psychological, physical, and cosmetic impact on individuals. Previous therapeutic modalities in scar treatment include surgical punch grafting, subcision, dermabrasion, chemical peeling, dermal fillers, as well as laser resurfacing with ablative and non-ablative devices. Published studies have demonstrated that NAFR can be successfully utilized in the treatment of various forms of scarring, including acne scarring, with a very favorable safety profile (Fig. 6.5). Mechanistically, fractional photothermolysis allows controlled amounts of high energy to be delivered deep within the dermis resulting in collagenolysis and neocollagenesis, which smoothes the textural abnormalities of acne scarring. In a large clinical study, Weiss showed a median 50–75% improvement of acne scars using a 1540 nm fractionated laser system after three treatments at 4-week intervals with 85% of patients rating their skin as improved. Alster showed similarly impressive results in a study of 53 patients with mild to moderate acne scarring; 87% of patients who received three treatments at 4-week intervals showed at least 51–75% improvement in the appearance of their acne scars. Non-ablative fractional resurfacing, in our estimation, is the treatment of choice for facial acne scarring.

Figure 6.5 Significant improvement in texture and rolling acne scars 2 months after four treatments with Fraxel re:store.

Pearl 1

Patients with deep acne scarring or severe rhytides often require high-energy settings, which correlates with deeper penetration of the laser and subsequent remodeling of collagen deeper in the cutis.

NAFR can also be safely used to treat acne scarring in darker-pigmented patients (Fig. 6.6). A study of 27 Korean patients with skin types IV or V that were treated with three to five non-ablative fractional resurfacing treatments revealed no significant adverse effects, specifically pigmentary alterations. Furthermore, all forms of acne scarring including ice-pick, boxcar, and rolling scars improved with eight patients (30%) reporting excellent improvement, 16 patients (59%) significant improvement, and three patients (11%) moderate improvement. With such a good efficacy and safety profile, many clinicians prefer NAFR to ablative fractional photothermolysis when it comes to treating acne scarring.