Biomedical Engineering Reference
In-Depth Information
Waibel and Beer published case reports in 2008 (86) and
2009 (87) on the use of fractional lasers (AFR and NAFR) for
the treatment of burn scars, which showed improvement in
hyperpigmentation, erythema, and texture.
Waibel and colleagues treated 10 patients with burn scars
with fi ve monthly sessions of Fraxel Re:Store (88,89). Pulse
energies of 40-70 mJ and densities of 232-552 MTZ/cm
2
(level
7-13; densities of 20-38%) were used. At 3 months after fi nal
treatment, improvement in texture was seen in all patients and
improvements in dyschromia, atrophy, or hypertrophy were
seen in 96% of patients.
ablative fractional resurfacing for scars
Fractional delivery systems for both CO
2
and Er:YAG lasers
emerged in an attempt to achieve the clinical results obtained
with traditional ablative lasers. Unlike nonablative fractional
lasers, which were previously discussed, these devices ablate epi-
dermis and variable depths of the dermis, requiring downtime
for healing, but often only a single treatment session. The com-
bination of epidermal and dermal ablation seems to produce a
more signifi cant wound healing response and dermal neocolla-
genesis, which helps explain the more predictable and faster
response in the treatment of wrinkle lines, skin tightening, scar-
ring, and dyschromias compared with nonablative devices.
Compared with conventional ablative lasers, ablative fractional
resurfacing (AFR) has greater safety and diminished healing
time, as normal skin is preserved in adjacent areas, as well as the
ability to treat off-face in an effective and safe manner.
Several ablative fractional lasers are available on the market.
The Fraxel Re:Pair system (Reliant Technologies, Mountain
View, California, USA) is similar to the nonablative Fraxel
lasers in operation with a continuous scanning mode with an
optical tracking system in which each individual spot is pre-
cisely delivered in an even distribution. Other devices have a
stamping handpiece from which all spots are delivered in a
single pulse passing through a lens array; and a scanning stamp
pattern delivered by a computer pattern generator such as the
Lumenis Active FX and Deep FX, the Er:YSGG laser (Pearl®,
Cutera, Brisbane, California, USA), and Er:YAG lasers includ-
ing Alma Pixel®, Palomar Er:YAG, and Sciton Profractional®.
Varying depths of ablation and coagulation with varying spot
sizes and shapes are possible with these devices. Unlike con-
ventional CO
2
or Er:YAG lasers, deeper coagulation of up to
1600
Figure 9.5
A series of surgical scars were divided into two sections: one
untreated and one treated with Fraxel Re:Store starting on the day of suture
removal and at 2-week intervals for a total of fi ve treatments. The treated
half was invariably less visible 3 months after the fi fth session.
Source
: Photo
courtesy of Cameron Rhoksar, MD.
Effi cacy and safety using the 1540-nm Er:Glass fractional
nonablative laser (Lux1540, Palomar Medical Technologies, Inc.)
to treat 33 surgical and posttraumatic scars were demonstrated
by Vasily and colleagues (84). Three to seven treatments with
energies up to 60 mJ and 5 passes were performed at 3- to
6-week intervals. At 1 month of follow-up, 73% of treated
scars improved 50% or more and 43% improved 75% or more.
Investigators also found a modest inverse correlation between
scar age and percent improvement with a mean improvement
score of 69% ± 20% (s.d.) for scars up to 10 years old versus
41% ± 18% (s.d.) for scars older than 10 years (
p
<0.001).
However, even older scars showed marked improvement.
The observations made in these two studies (85,86) showing
that older scars do respond to NAFR are an important and
signifi cant observation that the senior author can confi rm
from his personal experience.
Burn scars often pose a therapeutic challenge with limited
available treatments. New modalities of treatment are clearly
needed as patients affected by these thermal scars frequently
suffer from morbidities and psychological impairments.
Haedersdal and colleagues conducted a randomized con-
trolled trial of 17 adult patients with burn scars of 1 year or
older with side-by-side test areas of three monthly 1540-nm
fractional laser (Lux1540, Palomar Medical Technologies) ver-
sus no treatment (85). Energy ranged from 70 to 100 mJ/mb
and 15-ms pulse duration in 3-4 passes. At 12 weeks after the
last treatment, laser-treated skin was signifi cantly more even
and smooth compared with adjacent untreated sides. Eight
out of 17 patients evaluated the burn scars to be moderately or
signifi cantly improved, eight patients reported mild improve-
ment, and one patient reported no benefi t from the treat-
ments. Superfi cial burn scars appeared to respond better than
deeper possibly due to limited penetration depth of laser into
the dermis. Moreover, skin grafted, meshed sites also responded
better than non-meshed sites in this study suggesting that
nonthermally damaged zones of transplant tissue might
respond better than thermally damaged, fi brotic tissue.
m can be safely used because of the fractional delivery
of laser irradiation (63).
Histological evaluation of wound healing with an ablative
fractional CO
2
device from Reliant Technologies using increas-
ing pulse energies
in vivo
showed a parallel column of epider-
mal and dermal ablation as deep as 1700
μ
m with a 70-mJ pulse.
By 48 hours, adjacent epidermal cell migrate into the ablated
areas and there is formation of MENDs as well as expression of
heat shock protein 72, which diminishes by 3 months (90).
Heat shock protein 47 is detected at 7 days and persists for
3 months, indicating persistent collagen remodeling. By 1 week
after treatment, the re-epithelialization is complete with extru-
sion of the MENDs. At 3 months after treatment, newly formed
compact collagen is observed throughout the dermis (64).
Hale and colleagues reported the use of the prototype Fraxel
Re:Pair laser for the treatment of facial traumatic and surgical
scars in 13 patients (91). One to three treatments were performed
μ
