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Subdermal Carbon Dioxide Laser Cutaneous Contraction
MAJ Paulino E. Goco, MC, USA;
Fred J. Stucker, MD
Arch Facial Plast Surg. 2002;4:37-40.
ABSTRACT
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Background Conventional carbon dioxide (CO2) skin laser resurfacing
reverses the effects of photoaging. A recent clinical series reported the
efficacy of performing subdermal CO2 resurfacing to obtain the same
skin contracture as epidermal skin resurfacing.
Objective To assess surface area contraction that occurs with subdermal CO2 laser resurfacing in the rat model.
Design A nonrandomized control study was performed using 32 rats. The 3 test
groups were divided by CO2 laser strength (5 vs 7 W) and the pattern
of resurfacing (cross-hatched vs parallel lines).
Materials and Methods The rats underwent subdermal continuous 2-mm defocused CO2beam
treatment of the right-sided experimental flap. The left subdermal flap acted
as a control. In the first group (n = 12), a subdermal cross-hatching of the
subdermal flap was performed with 7 W. The second group (n = 10) was resurfaced
in a parallel fashion with 7 W. The third group (n = 10) was resurfaced in
a parallel fashion with 5 W. Measurements of skin area were taken immediately
after laser resurfacing and 3 weeks after the treatment.
Results None of the treatment arms showed a change in skin surface area immediately
or 3 weeks after treatment. In the first treatment group, all of the treated
flaps showed an entire full-thickness slough. Of the controls, 75% showed
minimal sloughing. The second and third experimental groups showed a 100%
slough of the flaps. Of the 20 control flaps in the second and third groups,
only 1 had a partial slough.
Conclusions In this animal model, subdermal CO2 laser resurfacing showed
a 100% rate of skin sloughing. No change in skin surface area was evident
immediately or 3 weeks after treatment.
INTRODUCTION
FACIAL REJUVENATION by the removal of the epidermis and superficial
layers of the dermis has been performed for many years. The resulting reepithelialization,
collagen regeneration, and remodeling provide for the desired youthful appearance
of the treated skin. Various methods have been used in the past, including
mechanical dermabrasion and chemical peels, to achieve similar clinical results.
These techniques have inherent technical disadvantages and potential side
effects that have limited their widespread application. Mechanical dermabrasion
requires extensive experience and technical skill to obtain consistent results.
Medical personnel are placed at risk of blood-borne infectious agents during
the mechanical dermabrasion procedure. Chemical peels are variable in their
depth of penetration and have their own potential risks and side effects that
make them less than ideal for general use.1-3
In the past few years, technical developments of pulsed and scanning carbon
dioxide (CO2) lasers for skin resurfacing have revolutionized the
clinical applications for these lasers. These recent developments have made
facial rejuvenation easier to perform. The CO2 laser allows for
predictable depth of penetration and corresponding results. Clinical outcomes
are consistent and patient satisfaction is high.1-2,4
AGING SKIN ULTRASTRUCTURE
Aging skin results from both endogenous and exogenous factors. Endogenous
changes of aging include dermal atrophy, loss of elastic fibers, loss of inherent
elasticity, and a decrease in subdermal adipose tissue. The exogenous factors
responsible for skin aging occur be cause of long-term sun exposure and loss
of moisture, which are characterized by coarse skin folds with a leatherlike
appearance.5-6 Histologically,
photoaged skin is characterized by an atrophic epidermis with dysplasia, atypical
keratinocytes, and altered and increased melanocytes.4
The dermis shows elastosis and homogenization of the upper papillary dermal
ground substance, formation of amorphous masses, and breakage of fibers.6 The underlying dermis has a decreased amount of collagen
and has been replaced with an amorphous material. The highly organized collagen
fibers are lost with an infiltration of amorphous glycosaminoglycan and proteoglycan
complexes within the dermis. The amorphous complexes consist of elastotic
material with reticular fibers and are probably responsible for the fine rhytid
formation associated with sun-damaged skin.4-6
Healing after the removal of the upper 100 to 500 µm or more of
the skin results in a reversal of the photoaged skin characteristics. Reepithelialization
following laser resurfacing occurs from the adnexal structures (pilosebaceous
units). Collagen regeneration and remodeling in the dermis are responsible
for the rejuvenation of the skin integrity and elasticity.1-3,7-8
A regeneration of the epidermis is produced by CO2 laser resurfacing.
Skin biopsy specimens 3 months following laser resurfacing showed restoration
of the normal cell polarity, correction of atypia, and correction of the melanocytic
hypertrophy and hyperplasia within the epidermis.3
In the dermal tissue, a wide band of normal collagen was evident. This new
collagen was arranged in uniform compact parallel bundles oriented horizontally
to the surface. Fine elastic fibers were also present within the neocollagen
zone. The amorphous glycosaminoglycan material was greatly diminished following
laser resurfacing. These results are very similar to deep phenol peels except
that hypopigmentation does not occur as often with CO2 laser resurfacing.4, 7
CO2 LASER RESURFACING SKIN CONTRACTURE
One of the characteristics of the CO2 laser resurfacing is
the obvious skin contracture that occurs during the actual procedure and appears
to persist in the postoperative period. The resulting decrease in skin redundancy
obviates the need for performing more invasive surgical procedures in many
patients.9-10
The actual cause for skin shrinkage is not known. The immediate contracture
may represent the ablation of water molecules from the epidermis, or thermal
coagulation of proteins within the dermis.10-14
The long-term postoperative dermal thickening and contracture may be related
to thermal changes, release of growth factors,15
or the modification of the extracellular matrix. Heat-induced collagen contracture
was first reported in studies of corneal reshaping about 100 years ago.16 At temperatures of 55°C to 60°C, the type
I collagen fibrils shorten by as much as one third their original length.16 Tissue necrosis occurs at temperatures greater than
70°C so that collagen shrinkage can be induced at a predictable temperature
range without concern of thermal tissue necrosis damage. Hydrothermal shrinkage
of the collagen fibers of rat skin have been well studied.17
The thermal studies performed by Allain et al17
in 1980 showed an initial relaxation prior to "isometric shrinkage," theoretically
due to the breaking of the collagen cross-linking and then their re-formation.
Many recent studies have been performed to assess the resulting skin
contracture. It appears that there is a direct effect by the CO2
laser from the thermal energy on the collagen fibers. Some studies report
that the individual collagen fibers within the dermis actually shorten once
subjected to the CO2laser. This has been most convincingly shown
by electron microscopy studies that reveal the reduction in size of the collagen
fibers.14 Seckel et al14
studied the CO2 laser effects on the skin of guinea pigs. A reduction
of 27% in length and 40% in width was seen immediately and persisted 12 weeks
postoperatively. Electron microscopy showed a significant shortening of the
collagen fibers by 7.45% that persisted the length of the study (12 weeks).
Campbell et al9 found a similar decrease in
the periodicity of individual fibers in both CO2laser and mechanical
dermabrasion pig skin. An average decrease in periodicity of 9 nm and 12 nm
was found in the dermabrasion and the CO2 laser resurfaced skin,
respectively.9
In contrast, Collawn et al10 studied
the immediate effects of CO2 laser resurfacing on human preauricular
skin. Using electron microscopy, the immediate "contraction" seen with the
CO2 laser was due to a loss of extracellular gel matrix. The ablation
of this surrounding matrix caused a compaction of the collagen fibers together
resulting in the observed "shrinkage" of skin tissue. Collagen fibers were
unchanged except at the surface of specimens. No shrinkage of the collagen
fibers was observed.
SUBDERMAL CO2 LASER RESURFACING
In an article by Cook,18 a technique
is described in which the platysma fascia and undersurface of the dermis of
the neck is laser resurfaced to induce contraction of these structures. Approximately
20% of the area of the platysma and subdermal skin is laser treated in a randomized
criss-crossing fashion with the UltraPulse 5000 CO2 laser using
a 7-W defocused setting. The 100 patients he described had a better clinical
outcome than traditional tumescent liposculpture of the submental neck.18 There was minimal scarring without instances of sloughed
overlying skin. No quantitative description of the amount of skin contracture
was noted from the subdermal laser resurfacing process. This technique has
never been reported in the literature. The objective of this study was to
assess the degree of skin contracture with this new method.
MATERIALS AND METHODS
Sprague-Dawley rats were anesthetized using ketamine hydrochloride (1000
mg/mL at a dose of 75 mg/kg intraperitoneally) and xylazine hydrochloride
(20 mg/mL at a dose of 5 mg/kg intraperitoneally) in compliance with the Louisiana
State University Medical Center Animal Resources protocol. The dorsal flanks
were shaved on each rat and a standardized grid was used to tattoo a 3 x
5-cm rectangle on each flank. Next, an incision was made approximately 1.5
cm cephalad to the previously marked grid. Under sterile conditions, a subdermal
flap was raised on each flank. The experimental side (right) subdermal flap
was laser resurfaced with a continuous 2-mm defocused CO2beam (MD30
carbon dioxide laser; Laser Engineering Inc, Milford, Mass); the left subdermal
flap acted as a control. Both flaps were closed with surgical staples.
The study consisted of 3 treatment groups. In the first group (n = 12),
a cross-hatching of the subdermal flap was performed with a CO2
laser power setting of 7 W (as described in the original article). The second
group (n = 10) was resurfaced subdermally in a parallel fashion (perpendicular
to the long axis) with a power setting of 7 W. The third group (n = 10) was
resurfaced subdermally in a parallel fashion (perpendicular to the long axis)
with 5 W. The amount of immediate dermal contraction was measured as a change
in the area of the 3 x 5-cm square. The animals were then observed for
immediate and delayed postoperative changes. The animals were killed 3 weeks
after the operation, the tattooed rectangle was then measured, and the area
was calculated for changes. Histological examination was performed to assess
any changes in the dermal collagen orientation. Clinical photographs were
also taken to document the outcomes of the study.
RESULTS
None of the treatment arms showed an immediate change in skin surface
area after subdermal laser resurfacing (immediately after laser resurfacing
or 3 weeks after treatment). During the course of the procedure, contracture
of the subdermal fascia appeared from the immediate lasering but this did
not affect the overlying dermal structures. In addition, and possibly more
important, there was almost universal sloughing of the dermis originating
from a subdermal eschar (Figure 1).
In the first treatment group (n = 12), all of the experimental laser-treated
flaps showed an entire full-thickness slough. Of the controls, 75% showed
minimal sloughing of the dermis. For the experimental side, the initial slough
average was 5 days with an average completion rate of 10 days and included
the entire flap. The control areas showed an initial slough average of 7 days
with an average completion rate of 14 days. In the controls, the area of slough
was usually a gravity-dependent portion with obvious accumulation of fluid
under the flap. Prior to scarring of the sloughed area, no change in skin
surface area was evident at 3 weeks after treatment. The second and third
experimental groups showed a 100% slough rate of the tested flaps. The average
flap showed approximately 70% loss of the area, which consisted primarily
of epidermalysis. Of the 20 control flaps in the second and third groups,
only 1 flap had a partial slough of approximately 60%.
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Figure 1. Sloughed dermis and subdermal
eschar after subdermal carbon dioxide laser resurfacing.
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Histological evaluation of the experimental and control sites was performed
at 3 weeks. Only areas of the experimental sites in which no eschar was clinically
evident underwent biopsy and were sent for histological evaluation. The tissues
were stained with hematoxylin-eosin. In review of the histological slides,
particular attention was made to collagen orientation within the dermis and
evidence of tissue damage from the surgical procedure and the CO2
laser. The experimental slides did not show any change in the orientation
of collagen fibers within the dermis. No evidence of histological tissue damage
from surgery or the laser therapy was evident at 3 weeks when control biopsy
specimens (Figure 2) were compared
with experimental specimens (Figure 3).
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Figure 2. Histological specimen of control
dermis (hematoxylin-eosin, original magnification x100).
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Figure 3. Histological specimen of experimental
dermis (hematoxylin-eosin, original magnification x100).
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COMMENT
The advantageous effect of dermal contraction with CO2 laser
resurfacing develops due to unknown causes. To obtain the dermal contraction,
patients must go through a recovery period. Reepithelialization can take approximately
2 weeks and loss of erythema can take up to 6 months for complete healing.
The technique of subdermal CO2 laser resurfacing attempts to accomplish
the goal of dermal contraction without the inherent recovery period.
Our animal study failed to support the clinical observations of dermal
contraction with subdermal laser resurfacing.18
None of the treatment arms showed a change in skin surface area after subdermal
laser resurfacing, immediately after laser resurfacing, or 3 weeks after treatment.
In this animal model, subdermal CO2 laser resurfacing showed a
100% rate of skin sloughing. The dermis receives its blood supply from the
subdermal vascular plexus. Interruption of this subdermal vascular plexus
would result in a devascularization of the overlying skin, subsequent sloughing,
and scarring. In the biopsy specimen of the nonsloughed rat skin areas, no
effect on the dermal collagen was evident at 3 weeks after treatment. Our
findings do not support an effect by the subdermal resurfacing to cause dermal
contraction.
Possible explanations for our contradictory findings are the inherent
differences in the rat model and the type of CO2 laser used. The
thinner dermal structures of the rat may have led to the universal sloughing
of the overlying skin. The continuous-wave CO2 laser, despite alteration
of the resurfacing pattern and limiting contact time, may still cause substantial
thermal damage as compared with the ultrapulse CO2 laser system.
The decreased power, the defocused beam, and the minimal contact with the
tissues should theoretically limit the amount of subdermal thermal exposure.
However, it still may not have been enough to achieve the same decreased thermal
effect seen with the ultrapulsed laser. In addition, we tried altering the
random cross-hatching pattern. Lasering in a parallel fashion to the shorter
dimension of the raised flap was performed to allow blood flow from the lateral
aspects of the flap; this did not provide any additional benefits.
Future studies will be performed using an ultrapulsed laser such as
the UltraPulse 5000 to investigate this mode of laser delivery to the subdermal
tissues in the rat model. As additional information is obtained as to the
cause of dermal contraction induced by CO2laser resurfacing, the
subdermal application may actually be a viable alternative.
CONCLUSIONS
In this animal model, subdermal CO2 laser resurfacing showed
a 100% rate of skin sloughing. No change in skin surface area was evident
immediately or 3 weeks after treatment. In this study, subdermal laser resurfacing
produced unfavorable results in all experimental groups without any beneficial
effect. Future studies are warranted to further assess the efficacy of subdermal
CO2laser resurfacing for dermal contraction.
AUTHOR INFORMATION
Accepted for publication January 11, 2001.
The views expressed in this article are those of the authors and do
not reflect the official policy or position of the US Army, the Department
of Defense, or the US government.
Corresponding author and reprints: MAJ Paulino E. Goco, MC, USA,
Otolaryngology–Head and Neck Surgery Service, ATTN: MCHJ-SET, Madigan
Army Medical Center, Tacoma, WA 98431 (e-mail: Paulino.Goco{at}NW.AMEDD.ARMY.MIL).
From the Otolaryngology–Head and Neck Surgery Service, Madigan
Army Medical Center, Tacoma, Wash (Dr Goco), and Otolaryngology–Head
and Neck Surgery Department, Louisiana State University Medical Center, Shreveport
(Dr Stucker).
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