The latest advance in aesthetic technologies has been the development of “micro-fractional” RF systems in which energy is delivered to the skin in a “fractional” manner (as opposed to treating the whole surface) via an array of multi-electrode pins. Radiofrequency current is delivered sequentially between each of the pin electrodes and the large electrode which surrounds the pin matrix. Due to this design, relatively high RF current densities are formed in the tissue under each pin electrode, resulting in localized fractional treatment micro-wounds in the epidermis which are in direct contact with the electrodes while heat is delivered deeper into the dermis. This fractional manner of energy delivery leaves intact zones in between the targeted areas which serve as a reservoir of healthy cells to promote faster, more effective wound healing.
Origins of Fractional Technology
The concept of treating the skin in a “fractional” manner utilizing lasers was introduced by Huzaira and colleagues in 2003. The fractional concept was developed to overcome the drawbacks in the treatment of photo damaged skin with “traditional” (whole beam) CO2 lasers. “Ablative” CO2 laser resurfacing is a powerful tool for the treatment of several skin conditions such as fine and coarse wrinkles, scars of various origin, uneven pigmentation, dilated pores, etc. However, a number of major drawbacks have progressively limited the use of CO2 lasers in the past decade, incliding: The need for effective anesthesia; significant “downtime” requirements, risk of dyspigmentation and scarring; the need for intensive postoperative care; long-lasting erythema; and the long avoidance of sun exposure.
“Non-ablative” fractional laser resurfacing, initially utilizing “mid-infrared” lasers, was the first attempt to escape the problems resulting from the use of traditional CO2 lasers. Mid-infrared lasers, such as the Fraxel (Reliant/Solta) utilizing the 1550nm wavelength and the Lux 1540 (Palomar) use invisible laser beams which are strongly absorbed by water, in order to reverse the effects of skin aging and scarring. Unfortunately, mid-infrared wavelengths cause significant pain and require some form of anesthesia. This is a time consuming and costly aspect. Another disadvantage for the operator is that most of these devices are only capable of performing this one type of procedure. The use of ablative lasers in a fractional mode was introduced in 2006. The lesser depth of immediate tissue necrosis, in comparison to the mid-infrared wavelengths, together with the possibility of further heat deposition in the dermis, significantly reduced the pain caused by the procedure, without decreasing its efficacy. New C02 lasers (i.e., Active FX, Lumenis, 10600nm) with less depth of penetration were shown to be more tolerable than the mid-infrared lasers, but the large (1.3 mm) spot size still made some local anaesthesia and\or cooling necessary. The spot distribution is not distributed as uniformly as with the mid-infrared devices. In more recent years, other fractional CO2 laser systems have been developed with smaller fractional beams and new scanning algorithms that keep the longest possible interval between two adjacent spots, in order to minimize the heat accumulation around the treated areas. These factors significantly reduce the pain experienced by patients during procedures.
Today, many of the minimally ablative lasers on the market are fractional. Fractional lasers use different wavelengths to ablate or coagulate tissue in columns. The skin then heals from intact cells involving both the edge of the wound and underlying tissue.
The wound-healing response and stimulation in tissue is not the same for all fractional wavelengths or devices. Many factors including spot size, wavelength, pulse duration and energy delivery can impact the efficacy of fractional devices. In theory, fractional devices maximize healing from the edges of the treatment area in annular regions around each injury. Fractional treatments result in an up-regulation (increase) of genes that result in collagen stimulation. Regions of epidermis that are coagulated during treatments are replaced by new cells eliminating sun damage in each treatment location. Collagen stimulation from each individual treatment is moderate when compared to full-coverage ablative devices. However, over the course of 4-6 treatment sessions, sequential stimulation results in fuller, plumper skin. Simultaneously, over the course of a series of treatments, sun damage in the epidermis is sequentially improved by the percentage of total coverage.
The Theory of Fractional Photothermolysis
Unlike with selective photothermolysis, where the whole of the selected target area is damaged; devices employing “fractional photothermolysis” seek to only damage certain zones within the selected target area, (producing tiny dot, or pixel-like treated areas on the skin), leaving the other zones within it perfectly intact; hence only causing fractional damage through the heat of the light source. This allows the skin to heal much faster than if the whole area was treated, as the ‘healthy’ untreated tissue surrounding the treated zones helps to fill in the damaged area with new cells.
Fractional photothermolysis or fractional laser skin resurfacing can therefore be compared to the precise alteration of digital photographs that we are able to do nowadays; pixel by pixel. The concept of this fractional laser technology can be applied with either ablative laser resurfacing or non-ablative laser skin rejuvenation, using the various different wavelengths of lasers available. The efficacy and safety of the different types of laser technologies is illustrated in the adjacent chart; (Source: Aesthetic Buyers Guide, March/April 2007). In theory, fractional devices maximize healing from the edges of the treatment area in annular regions around each injury. Fractional treatments result in an up-regulation (increase) of genes that result in collagen stimulation. Regions of epidermis that are coagulated during treatments are replaced by new cells eliminating sun damage in each treatment location. Collagen stimulation from each individual treatment is moderate when compared to full-coverage ablative devices. However, over the course of 4-6 treatment sessions, sequential stimulation results in fuller, plumper skin. Simultaneously, over the course of a series of treatments, sun damage in the epidermis is sequentially improved by the percentage of total coverage.
The fractional approach (ablative and non-ablative) claims to achieve comparable skin improvements as obtained with conventional ablative laser resurfacing with an Er:YAG or CO2 laser, (depending on depth and severity of wrinkles), but without the associated side effects or downtime; i.e. you get the results of an ablative laser but with the downtime of a non-ablative laser. Optimal improvement after fractional treatment is usually visible in about 2 – 3 months as collagen remodeling and skin tightening continues. The longevity of results is comparable to ablative laser resurfacing and as always is dependent on future ageing, the effects of gravity and sun exposure.
Several “fractional” resurfacing lasers claimed to bridge the gap between “ablative” and “non-ablative” procedures. These fractional lasers utilize a pattern of tiny but high-powered beams to produce thousands of microscopic thermal wounds in the skin. By fractionating these powerful beams it was possible to avoid the excessive tissue damage that would otherwise result. It was also claimed that the treatments improve the texture of the skin (provided the patient is willing to return for multiple visits) even though only from 5 to 10% of the skin surface is generally treated each procedure. The remaining 90% of the tissue serves as a “reservoir” of normal skin to promote quicker healing and minimize adverse tissue effects as shown below:
As a middle approach to laser skin resurfacing that falls between ablative and non-ablative laser resurfacing, fractional laser resurfacing evolved in the late 2000’s with the emergence of many variations and competitors. Ablative laser resurfacing which pioneered about 30 years ago with CO2 lasers and subsequently the Er:YAG lasers, provided excellent treatment efficacy for rhytides and photoaging. However, 3+ week recovery periods and small but significant risks of side effects and complications also had to be taken into account. This spurred the development of non-ablative technologies over the next decade, including infrared lasers, intense pulsed light, and radiofrequency devices, which provided the highly desirable alternative of extremely rapid treatment and recovery coupled with minimal risk, but with only modest improvement. In an effort to augment efficacy while maintaining an excellent safety profile, initially fractional laser resurfacing and then fractional radiofrequency emerged whereby regular lattices of microscopic columns of the skin are thermally ablated and coagulated with intervening normal skin, allowing for faster recovery than ablative resurfacing and better results than non-ablative techniques.