Biomedical Engineering Reference
In-Depth Information
“plateau” characteristic of CO
2
laser resurfacing is not reached
(10). Its minimal optical penetration depth and limited zone
of residual thermal damage endow the Er:YAG laser with supe-
rior capacity for effi cient, precise, and controlled tissue abla-
tion. This has translated clinically into faster recovery times
and a signifi cantly more favorable side effect profi le than seen
after CO
2
laser skin resurfacing (2,6,11-13). Additionally, the
Er:YAG laser's capacity to confi ne ablation superfi cially has
signifi cantly reduced anesthesia requirements and anesthesia-
related complications associated with laser skin resurfacing.
Because of its greater safety margin, the Er:YAG laser has
proven advantageous for resurfacing of nonfacial skin (i.e.,
neck, forearms, and hands) that, given its relative lack of
adnexae and its tendency toward slower healing, is considered
by most experts to be “off-limits” to CO
2
laser treatment
(14,15). Additionally, patients with darker Fitzpatrick skin
phototypes (III and above), who experience a high rate of pig-
mentary alteration following CO
2
laser resurfacing (5,16-18),
have been effectively treated with the Er:YAG laser with a
considerably lower incidence of postoperative pigmentary
alterations (2).
Given its advantages, it was initially postulated that the
short-pulsed Er:YAG would completely replace the CO
2
laser
as a resurfacing tool. However, this initial enthusiasm was tem-
pered by the realization that resurfacing with the Er:YAG laser
was hindered by poor intraoperative hemostasis, which lim-
ited ablation depth, and by the Er:YAG's limited ability to
induce signifi cant tissue shrinkage, both of which translated
into clinical results that were considerably less impressive than
those previously achieved with the CO
2
laser (11,19-24).
Many experts believed that the comparatively superior results
achieved with the CO
2
laser were due to thermally induced tis-
sue changes. A number of studies showed that treatment with
the CO
2
laser led to heating of dermal collagen, collagen con-
traction, and reactive dermal neocollagen synthesis. Immediate
tissue contraction of 25-40% was reported during CO
2
laser
resurfacing (25). In contrast, early studies failed to show signifi -
cant tissue contraction with short-pulsed Er:YAG laser skin
resurfacing.
With the thought that thermally induced tissue contrac-
tion was important for long-term laser resurfacing results,
“modulated” Er:YAG lasers combining the precise ablation
capability of the short-pulsed Er:YAG laser with a “CO
2
-like”
coagulative effect were introduced (21). Modulated Er:YAG
lasers have demonstrated clinical effi cacy comparable with
that of the short-pulsed CO
2
laser in a number of studies
(21,26,27). Moreover, studies have demonstrated faster reepi-
thelialization and recovery times and signifi cantly lower inci-
dence of postoperative complications after modulated Er:YAG
laser skin resurfacing as compared with CO
2
laser skin resur-
facing. Modulated Er:YAG lasers have achieved good-to-
excellent improvement of class III and above rhytides with a
side effect profi le and convalescence time that is somewhere
between that of the CO
2
and short-pulsed Er:YAG lasers
(28-30). The modulated Er:YAG lasers have given cosmetic
surgeons a true alternative to CO
2
laser resurfacing.
Modifi cations of technical protocols have continued to
improve clinical outcomes. Combination therapy with the
CO
2
and Er:YAG lasers allows cosmetic surgeons to capitalize
on the unique benefi ts of each laser system and to minimize
their disadvantages. Er:YAG laser treatment can be used to
bypass the ablation “plateau” characteristic of CO
2
resurfacing.
Improved postoperative healing can be attained when the
short-pulsed Er:YAG laser is used to remove the residual zone
of thermal necrosis that is left behind after CO
2
resurfacing
(31,32). A similar benefi t on healing can be derived with the
modulated Er:YAG lasers if resurfacing with their “CO
2
-like”
long pulse is followed by treatment with their short-pulsed
Er:YAG mode.
Additionally, the ablative lasers have turned out to be
extremely versatile therapeutic tools. Cosmetic surgeons
now regularly combine ablative laser resurfacing with other
problem-specifi c nonablative technologies to address multiple
cosmetic concerns for the patient in a single-treatment ses-
sion. The effi cacy of Q-switched lasers in the treatment of pig-
mented lesions is enhanced when these lasers are utilized after
ablative resurfacing. Treatment of vascular lesions with the
pulsed dye laser or other vascular lasers has been shown to be
extremely successful when performed before skin resurfacing
with an ablative laser (33). Despite early reports advising
against it (34-36), full-face laser resurfacing is now safely
being combined with rhytidectomy to achieve a more compre-
hensive approach to facial rejuvenation. Large series of patients
treated with the combination of rhytidectomy and laser skin
resurfacing have reported complication rates that are no
greater than those typically seen with either treatment modal-
ity alone (37-39).
Given its capability to produce precise depths of ablation
with minimal residual thermal damage, the Er:YAG laser has
proven particularly advantageous in cutaneous resurfacing of
face-lift fl aps with potentially compromised vascular supply.
Combination therapy is helping cosmetic surgeons achieve
results that are superior to those attainable with either treat-
ment modality alone. Additionally, by reducing cost and con-
valescence time, combination therapy is making cosmetic
surgery more appealing to a number of patients.
Pretreatment (40,41) and posttreatment protocols have
improved as well. Although some controversy remains sur-
rounding the topic of antibiotic prophylaxis, a number of
studies have provided relevant information on common
pathogens, effective antibiotic prophylaxis regimens, and clin-
ical situations at increased risk for infection after cutaneous
laser resurfacing (42-47). Improved laser wound care regi-
mens have reduced recovery time and decrease morbidity
after laser skin resurfacing. The benefi ts of occlusive dressings
in accelerating laser wound healing have been well established
in a number of studies (42,44,48-52). Timely institution of
medications in the postoperative period is now allowing sur-
geons to effectively address a number of expected postopera-
tive symptoms and complications including postoperative
erythema and edema, pruritus, and postinfl ammatory hyper-
pigmentation (53,54). Considerable progress has also been
made in the treatment of the adverse sequelae of laser skin
resurfacing. Topical photochemotherapy and excimer laser
therapy are the available options for the treatment of delayed-
onset hypopigmentation (55,56). Moreover, patient satisfac-
tion with laser skin resurfacing remains high. A prospective
study surveyed patients 30 months after laser skin resurfacing
