part I

1. CONTINUING MEDICAL EDUCATION
Surgical technique for optimal outcomes
Part I. Cutting tissue: Incising, excising, and undermining
Christopher J. Miller, MD,a
Marcelo B. Antunes, MD,b
and Joseph F. Sobanko, MDa
Philadelphia, Pennsylvania, and Austin, Texas
Sound surgical technique is necessary to achieve excellent surgical outcomes. Despite the fact that
dermatologists perform more office-based cutaneous surgery than any other specialty, few dermatologists
have opportunities for practical instruction to improve surgical technique after residency and
fellowship. This 2-part continuing medical education article will address key principles of surgical
technique at each step of cutaneous reconstruction. Part I reviews incising, excising, and undermining.
Objective quality control questions are proposed to provide a framework for self-assessment and continuous
quality improvement. ( J Am Acad Dermatol 2015;72:377-87.)
Key words: excise; excision; incise; skin; surgery; suture; technique; undermine.
INTRODUCTION
Surgeons influence the aesthetics of scars from
cutaneous surgery in 2 ways: (1) surgical design and
(2) surgical technique. The principles of aesthetic
surgical design are universally accepted, and include
preserving and restoring free margins (eg, eyelids,
nasal tip and ala, lips, and helical rim), preserving
and restoring contour, and placing scars in cosmetic
subunit junction lines.1
Placing scars along
relaxed skin tension lines is also desirable, but is
less important compared to the aforementioned
principles.2
For example, it is undesirable to conform
to the horizontal relaxed skin tension lines on the
forehead if elevation of the ipsilateral eyebrow
creates asymmetry.
While surgeons nearly universally adhere to the
core principles of aesthetic surgical design, surgical
technique varies markedly. These variations can
confuse surgical trainees, who are left to struggle
by trial and error through numerous potential
approaches to execute the same surgical tech-
nique.3,4
Only after months to years of independent
practice and observation of their own postoperative
outcomes do most surgeons refine their own surgical
technique and achieve reproducibly excellent
results.5
Many practitioners desire additional
surgical coaching after their formal training.6
This 2-part continuing medical education article
proposes quality control questions for each step
of cutaneous reconstruction and provides a
Learning objectives
After completing this learning activity, participants should be able to describe common errors during the removal of tissue that lead to unaesthetic scars and delineate the steps for
proficient fusiform excisions.
Disclosures
Editors
The editors involved with this CME activity and all content validation/peer reviewers of the journal-based CME activity have reported no relevant financial relationships with
commercial interest(s).
Authors
The authors involved with this journal-based CME activity have reported no relevant financial relationships with commercial interest(s).
Planners
The planners involved with this journal-based CME activity have reported no relevant financial relationships with commercial interest(s). The editorial and education staff involved
with this journal-based CME activity have reported no relevant financial relationships with commercial interest(s).
From the Department of Dermatology,a
University of Pennsylva-
nia, Philadelphia, and Private practice,b
Austin.
Video available at http://www.jaad.org.
Funding sources: None.
Conflicts of interest: None declared.
Accepted for publication June 17, 2014.
Correspondence to: Joseph F. Sobanko, MD, Edwin & Fannie Gray
Hall Center for Human Appearance, University of Pennsylvania,
3400 Civic Center Blvd, Rm 1-330S, Philadelphia, PA 19104.
E-mail: Joseph.Sobanko@uphs.upenn.edu.
0190-9622/$36.00
Ó 2014 by the American Academy of Dermatology, Inc.
http://dx.doi.org/10.1016/j.jaad.2014.06.048
Date of release: March 2015
Expiration date: March 2018
377

2. framework for self-assessment and continuous qual-
ity improvement.
STEPS OF SURGICAL RECONSTRUCTION
Surgical techniques fall into 2 broad categories:
cutting and suturing. Cutting techniques include
incising, excising, and undermining. Suturing
techniques include placing deep and top sutures.
Most reconstructive surgery involves the stepwise
execution of these cutting and suturing techniques.
Each step influences the success of subsequent
steps; errors early in the process make the precise
execution of subsequent steps either more difficult
or impossible.
Scars heal with a shiny texture that reflects light
more brightly than the textured, normal surrounding
skin. Sound surgical technique must therefore aim to
diminish the contrast between scar and normal skin
by minimizing the breadth of the scar.7-9
Precise,
tension-free approximation of the skin edges allows
for prompt reepithelialization and a barely visible
scar.10,11
The appearance of scars often improves
with time, helping to disguise minor technical
deficiencies.12
The appearance of the wound 1
week after surgery gives an honest assessment
of the precision of the surgical technique.
Completely reepithelialized scars with minimal to
no inflammation signify meticulous surgical tech-
nique (Fig 1). Wounds with prominent inflammation
and focal inversion or separation of wound edges
usually result from suboptimal surgical technique
(Fig 2). In these continuing medical education
articles, we analyze each step of cutting and suturing
and propose quality control checkpoints for
objective self-evaluation. Part I reviews cutting
techniques, including incising, excising, and under-
mining. Part II reviews suturing techniques,
including placing deep and top sutures. Space
precludes a comprehensive coverage of surgical
techniques; we therefore focus on core techniques
that apply broadly to any surgeon performing
surgery of the skin.
CUTTING TECHNIQUE: INCISING
Key points
d The incision aims to achieve uniform release
of the entire skin edge to the desired
anatomic depth
d The ideal depth of the incision varies
according to the anatomic location and
intent of the procedure
d The incised wound edges should be smooth
and sharply perpendicular to the skin
surface
d Beveling of the dermis or fat toward the
center of the wound impedes the precise
approximation of wound edges
The goal of the incision is to achieve uniform
release of the entire skin edge to the desired
anatomic depth and to create smooth and
perpendicular wound edges without a bevel.13
Before beginning the procedure, the surgeon should
have a clear plan for the anatomic depth of the
incision. The desired anatomic depth will vary based
on the location and intent of the procedure. In most
cases, the depth of the incision will correspond to the
intended anatomic plane for the subsequent steps of
excision and undermining. The skin should be
released to a uniform depth along the entire incision
(Fig 3).
The incision should create wound edges that are
sharply perpendicular to the skin surface, because
any bevel of the dermis or fat will impede the direct
apposition of the epidermal edges during suturing
(Fig 4). Beveled wound edges will force the surgeon
to place excessive tension on the sutures, a practice
that increases the risk of leaving suture marks on
Fig 1. A, Ideal appearance of a wound on the forehead 1 week postsurgery, with sutures still in
place. There is minimal erythema. B, Appearance of the same wound on the forehead
immediately after removing the sutures. Precise approximation of the wound edges and
minimal inflammation reflect sound surgical technique and portend a minimally apparent scar.
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3. each side of the scar (Fig 5). The angle of the scalpel
relative to the skin influences whether or not the
incision creates beveled wound edges. The scalpel
handle tends to fall toward the surgeon’s dominant
hand, similar to the eraser end of a pencil, thereby
positioning the blade in an undesirable beveled
position (Fig 6, A). The surgeon must compensate
for this natural tendency by taking care to hold the
scalpel perpendicular to the surface of the skin
throughout the entire pass of the incision (Fig 6, B).
Cleanly incised wound edges facilitate precise
approximation of the epidermis and dermis during
suturing. Jagged wound edges complicate suturing.
A sharp scalpel should incise the skin smoothly with
minimal downward pressure. If the surgeon forces
the scalpel with downward pressure in an attempt to
reach the desired depth in 1 pass, or if the scalpel
edge is dull, the scalpel may succumb to chatter,
resulting in jagged wound edges. To avoid chatter,
especially in thick or fibrotic skin, [1 pass of the
scalpel may be necessary to reach the desired
depth. If multiple passes are necessary to incise
through thick skin (eg, on the back and proximal
extremities), applying pressure of the scalpel against
the outside wound edge can decrease the risk for a
bevel on subsequent passes. Using the nondominant
Fig 5. Typical long-term appearance of a scar repaired
with excessive tension on the superficial sutures. The scar
has spread, and prominent track marks are present.
Fig 2. Suboptimal appearance of a wound 1 week
postsurgery and immediately after removing the
cutaneous sutures. Prominent inflammation and inversion
of the wound edges have resulted from imprecise surgical
technique and signal an opportunity to improve technical
skills.
Fig 3. The incision should achieve uniform release to the
desired anatomic depth. Note this fusiform incision where
the tips have not been incised to the same depth as the
sides of the specimen. The tips (black arrowheads) require
additional release.
Fig 4. Intraoperative appearance of a wound repaired
with suboptimal technique. The black arrow indicates a
prominent beveled edge of the dermis. The beveled
dermis will prevent direct approximation of the wound
edges, regardless of the quality of the buried sutures. In an
attempt to close the gap between the epidermal edges, the
superficial sutures have been placed with excessive
tension. The prominent gap at the puncture site of the
superficial sutures (black arrowhead) risks track marks.
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4. hand to stabilize the skin with gentle downward
pressure (as opposed to lateral traction) also mini-
mizes a beveled dermis with each pass of the scalpel.
The epidermis and dermis have greater surface
tension compared to subcutaneous fat. After incising
through the dermis, the epidermis and dermis
immediately retract away from the incision, and the
subcutaneous fat tends to lag toward the center of
the wound (Fig 7, A). If the lagging fat obscures the
dermis or extrudes between the wound edges during
the placement of deep sutures, trimming it flush with
the dermis allows for greater visibility of the reticular
dermis for accurate placement of the buried dermal
sutures (Fig 7, B). In many cases, this is best
accomplished after undermining. Using forceps to
gently stabilize the lagging fat, the surgeon can use
tissue scissors to trim the fat flush with the dermis
and create a sharply perpendicular wound edge
along the full thickness of the skin flap. Excessive
traction should be avoided, because it frequently
causes a reverse bevel (ie, a bevel away from the
center of the wound), which makes it more difficult
to place the deep sutures without a prominent
dimple.
Goal of incision
The goal of incision is to achieve a uniform release
along the entire skin edge to the desired anatomic
depth and to create smooth and perpendicular
wound edges with no bevel.
Quality control checkpoints for incision
1. Has the incision achieved uniform release to the
desired anatomic plane?
a. Troubleshooting #1—If the incision has
not reached the desired anatomic depth,
complete the incision to get uniform release.
b. Troubleshooting #2—If the incision extends
more deeply than the intended depth of
Fig 6. A, Suboptimal surgical technique, with the scalpel handle falling toward the dominant
hand. This position predictably incises the skin with a beveled edge. B, Sound surgical
technique, with the scalpel handle and blade held perpendicular to surface of the skin. This
position will help to incise the skin with a vertical wound edge and no bevel.
Fig 7. A, Intraoperative appearance of a wound after incision, excision, and undermining. The
epidermis and dermis have retracted away from the center of the wound more than the
subcutaneous fat. The lagging fat (black arrowhead) creates a beveled edge that obscures
visualization of the reticular dermis and will obstruct direct approximation of the dermis. B,
Intraoperative appearance of the same wound showing the technique of using tissue scissors to
trim to the lagging fat bevel flush with the dermis. The fat bevel on the superior wound edge
has already been trimmed and now has an incised wound edge with a precisely vertical face.
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5. the excision and undermining, be careful that
the subsequent steps of excision and under-
mining occur in the correct anatomic plane.
2. Are the incised wound edges perpendicular
without a bevel of the dermis or fat?
a. Troubleshooting #1—If the dermis is cut with
a beveled edge, ensure that the angle of the
scalpel is perpendicular to the plane of the
skin throughout the entire pass of the incision
(Fig 6, B).
b. Troubleshooting #2—If the dermis is cut
with a beveled edge, assess the method
of stabilizing the skin. The application of
downward pressure perpendicular to the
surface of the skin is less likely to produce a
beveled edge compared to stretching each
side of the skin away from the path of the
incision.
c. Troubleshooting #3—To avoid a beveled
dermal edge, consider using a no. 10 scalpel
for anatomic locations with a thick dermis.
d. Troubleshooting #4—If the dermis is cut with
a beveled edge, grip the redundant tissue
with a forceps and apply gentle traction into
the wound. Incise through the beveled
dermis to create a clean and perpendicular
edge.
e. Troubleshooting #5—If the subcutaneous fat
is lagging in the center of the wound, consider
using tissue scissors to trim the lagging fat
flush with the vertical face of the incised
dermis (Fig 7, B).
3. Are the wound edges cut cleanly without jagged
edges?
a. Troubleshooting #1—Jagged edges may occur
from excessive downward pressure or the use
of a dull scalpel. Ensure that the scalpel
is sharp and pass the scalpel lightly, allowing
[1 pass to achieve the desired depth, if
necessary.
b. Troubleshooting #2—Jagged edges may occur
if loose skin is not stabilized while incising.
Improve stabilization of the skin while
incising.
Common errors to avoid during incision
1. Failure to incise to the desired anatomic depth
(ie, either too superficial, leading to no release,
or too deep, leading to bleeding through the
gulley from the incision)
2. Holding the scalpel at an angle that creates a
beveled edge
3. Jagged wound edges resulting from chatter
caused by excessive downward pressure on the
scalpel, from a dull blade, or from a failure to
stabilize the skin while incising
CUTTING TECHNIQUE: EXCISING
Key points
d Excision should remove the lesion or excess
skin during the reconstruction with minimal
collateral damage to important anatomic
structures
d The anatomic plane of the excision ideally
corresponds to the depth of initial skin
incision; otherwise, hemostasis may be
more challenging or bulky soft tissue in the
central wound may impede apposition of
wound edges
d The ideal anatomic plane of excision varies
by location on the body
d Ideal planes of excision are characterized by
the effortless release of tissue and minimal
bleeding
Excision has 2 purposes: either to (1) ensure
complete removal of a lesion or to (2) restore
contour by removing the standing cone or excess
tissue during the reconstruction. Based on the
clinical examination and pathology of the preoper-
ative biopsy specimen, the surgeon must determine
the anatomic depth of the excision. The excision
should remove the lesion or excess skin with
minimal collateral damage to important anatomic
structures. Deeply infiltrating tumors may require
excision to a depth that causes predictable
morbidity. For example, a tumor that invades
the deep fat on the temple may require excision of
the temporoparietal fascia and may sacrifice the
temporal branch of the facial nerve. By contrast,
the surgeon can almost always dictate the anatomic
plane when excising standing cones or excess tissue
during the reconstruction. The ideal anatomic planes
for different anatomic locations can be found in
Table I.
Ideally, the preceding incision has released the
skin to the desired anatomic depth and the excision
continues a clean lift of tissue in the same surgical
plane. In areas with thick subcutaneous fat, a
disparity between the depths of the incision and
excision may create unnecessary challenges during
the closure. For example, if the incision extends to
the fascia, but the tissue is excised at the level of the
superficial subcutaneous fat, then the island of
subcutaneous fat at the base of the wound can
impede advancement of the wound edges during
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6. the closure and complicate hemostasis by obscuring
blood vessels (Fig 8).
On the scalp, central face and temples, hands and
feet, and male genitalia, the subcutaneous fat is
either thin or indistinct (eg, on the mid-chin, the
mentalis muscle inserts directly into the dermis and
there is not a distinct layer of fat), so the surgeon
encounters the underlying muscle or fascia
immediately after release of the dermis. In the medial
aspect of the cheek, neck, trunk, proximal
extremities, and female genitalia, there is frequently
a thicker layer of subcutaneous fat. In these loca-
tions, a layer of columnar, compact, and tightly
organized fat lobules adheres to the underside of
the dermis. A surgical plane separates these tightly
organized columnar lobules from a deeper layer of
larger, more loosely organized fat lobules that invest
the fascia (Fig 9). Vigorous scrubbing with gauze can
often dislodge these deeper, loosely organized,
larger fat lobules from the fascia. The junction of
Table I. Ideal surgical planes for incising, excising, and undermining
Anatomic location Preferred anatomic plane Comments/critical structures to consider
Trunk and extremities Junction of subcutaneous fat
and deep fascia
In areas on the trunk and proximal extremities, with a thicker
layer of subcutaneous fat, the ideal surgical plane is the
junction between the tightly organized, compact, columnar
fat lobules adherent the underside of the dermis and the
underlying, looser, larger, and more disorganized fat lobules
that invest and obscure the fascia
Lateral aspect of the
face and neck
Junction of the subcutaneous
fat and SMAS
The motor branches from the facial nerve always lie deep to
the most superficial layer of SMAS (in areas where the
muscles of facial expression are layered [eg, lip depressors
and elevators], the motor nerves innervate the deepest
muscles from their superficial surface); excision at the
junction of the subcutaneous fat and SMAS will always
protect the motor nerves
Central third of face
and scalp
At the junction of subcutaneous
fat and SMAS or deep to the
muscles of the SMAS or galea
(on scalp)
Because the branches of the facial nerve have arborized before
reaching the central third of the face, excision deep to the
SMAS is less likely to cause motor deficits (eg, excision of
midline and paramedian frontalis muscle does not leave
motor deficit on the forehead); on the midline nose,
forehead, and scalp, undermining deep to the SMAS is
frequently desirable
SMAS, Superficial musculoaponeurotic system.
Fig 8. This intraoperative photograph shows a
discrepancy between the anatomic depths of the incision
and excision. The incision has released to the fascia. The
central island of tissue is being excised in the superficial
subcutaneous fat. A gully (arrowhead) left by the deeper
incision often creates challenges for hemostasis, and the
central island of fat can impede advancement of the
wound edges. Excising the specimen with tissue scissors
reduces the likelihood of this error by providing improved
tactile feedback from the release of the anatomic planes.
Fig 9. On the trunk and extremities, the ideal surgical
plane is at the junction of the tightly organized, columnar
fat adherent to the dermis and the larger, loosely organized
fat lobules that invest the deep muscular fascia.
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7. these 2 layers of fat provides a natural and efficient
surgical plane that releases effortlessly. Optimal
planes for excision vary by location (Table I).
Excising at the junctions of tissue planes minimizes
bleeding and allows for effortless dissection. On the
trunk and extremities, the junction of the subcutane-
ous fat and deep muscular fascia provides an ideal
surgical plane (Fig 9). In order to preserve the
underlying branches of the facial nerve on the lateral
aspect of the face and the spinal accessory nerve in
the posterior triangle of the neck, the surgeon
excises at the junction of the subcutaneous fat and
fascia of the superficial musculoaponeurotic system
(SMAS; Fig 10). On the central face, excising deep to
the muscles of facial expression/SMAS poses a
minimal risk for motor deficits (Fig 11). Whereas
the most common surgical plane on the nose and
central forehead is deep to the SMAS, it is more
common to work superficial to the orbicularis oris
muscle around the mouth. For smaller procedures in
the central face, the surgeon may choose a
surgical plane superficial to the SMAS. In the midline
forehead, for example, the surgeon may choose to
stay above the frontalis for a small horizontal
excision in order to minimize postoperative sensory
deficits, but may excise deep to the frontalis to
remove bulk and facilitate tissue advancement for a
large excision. On the scalp, the anatomic plane of
the excision is usually deep to the galea apo-
neurotica (Fig 12).
The surgeon can use either scissors or a scalpel for
excision. Scissors have some advantages over
scalpels, especially when the surgeon does not
have intimate knowledge of the surgical planes.
Compared to the scalpel, scissors provide more
tactile feedback, which helps the surgeon feel the
release of tissue and maintain a uniform anatomic
plane. Scissors should split the anatomic plane with
ease, especially in healthy skin without fibrosis from
a previous scar. Undue resistance during excision
should prompt the surgeon to reevaluate the
accuracy of the anatomic plane. In contrast to
scissors, the blind, sharp edge of the scalpel more
easily breaches tissue planes. Especially in areas with
thick subcutaneous fat, such as the abdomen or
Fig 10. Excising and undermining superficial to the
superficial musculoaponeurotic system of the face and
investing cervical fascia of the neck preserves the
underlying branches of the facial nerve on the lateral
face and the spinal accessory nerve in the posterior
triangle of the neck.
Fig 11. On the central face, where there is minimal risk
for motor deficits from working in a deep surgical plane,
the anatomic plane of excision is usually deep to the
muscles of facial expression/superficial musculoaponeur-
otic system. For smaller procedures, the surgeon may
choose a surgical plane superficial to the superficial
musculoaponeurotic system.
Fig 12. On the scalp, the anatomic plane of the excision is
usually deep to the galea aponeurotica.
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8. proximal thigh, there is a tendency for the scalpel to
cut progressively deeper during the excision and for
the underside of the specimen to have scalloped
incisions. The surgeon should aim for a clean
separation of anatomic planes and an excision
specimen with a uniform thickness in profile that
reflects the accuracy of the plane of excision (Fig 13).
Goal of excision
The goal of excision is to remove the skin in a
uniform and efficient anatomic plane with minimal
morbidity to the underlying structures.
Quality control checkpoints for excision
1. Is the excision effortless and does it cause
minimal bleeding?
a. Troubleshooting—Undue resistance or exces-
sive and diffuse bleeding from small vessels
frequently signifies an inefficient plane of
excision. Reevaluate the plane of excision
and aim for the junction of tissue planes,
where excision usually occurs effortlessly and
with less bleeding (Figs 9-12).
2. Does the excision specimen have a uniform
thickness (Fig 13)?
a. Troubleshooting—If the profile view of the
excised specimen has varying thicknesses,
then consider using scissors, rather than a
scalpel, to gain the tactile feedback that helps
maintain a uniform anatomic plane during
excision.
3. Does the base of the wound have a uniform
depth at the desired anatomic plane (Fig 14)?
a. Troubleshooting—If the base of the wound
does not have a uniform anatomic depth
because of a partially shallow excision, then
complete the excision of the remaining
superficial tissue to the desired anatomic
plane. If portions of the wound have been
excised more deeply than the preferred
anatomic depth, be careful that undermining
occurs more superficially at the preferred
anatomic plane.
Common errors to avoid during excision
1. Failure to excise the specimen in a uniform
anatomic plane
2. Mismatch between the anatomic depths of the
incision and excision
3. Failure to excise the tissue at the junction of
tissue planes
CUTTING TECHNIQUE: UNDERMINING
Key points
d Undermining may facilitate advancement of
the wound edges and eversion when
suturing
d Wounds at anatomic sites where the fascia is
adherent to the overlying dermis benefit
most from undermining
d Excessive undermining can threaten the
blood supply of the flap and rarely provides
a mechanical advantage
d The plane of undermining frequently
corresponds to the plane of excision
Fig 14. Examining the base of the wound for a uniform
surgical plane serves as a quality control checkpoint. The
plane of excision on the anterior surface of the neck seen
in this photograph is immediately superficial to the
platysma muscle, providing a relatively bloodless and
efficient surgical plane.
Fig 13. Assessing the excision specimen for uniform
thickness serves as a quality control checkpoint. The
fusiform excision specimen in the photograph has a
uniform thickness in profile. In this case, the small excision
specimen was removed in plane of the superficial
subcutaneous fat. Excising the specimen at the junction
of the subcutaneous fat and fascia is usually a more
efficient surgical plane that allows for easier isolation of
vessels for hemostasis.
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9. d An efficient plane of undermining is charac-
terized by effortless release of the tissue and
minimal bleeding
d Efficient undermining requires effective
countertraction, most frequently applied
with a skin hook, directly over the point of
release
The goals of undermining are to (1) facilitate
tissue advancement by releasing either the skin
edges or flap from underlying adhesions and to
(2) facilitate eversion of the wound edges during
suturing. The surgeon must make 2 key decisions
when undermining: (1) the ideal anatomic plane for
undermining and (2) the extent of undermining
(ie, how widely to undermine). In most cases, the
anatomic plane for undermining coincides with the
depth of the incision and the plane of the excision.
If the surgeon is working in an efficient surgical
plane, undermining should occur with ease. Undue
resistance while undermining usually signifies an
inefficient anatomic plane (eg, most commonly
splitting the subcutaneous fat rather than working
at the junction of the fat and fascia). The ideal surgical
plane varies based on the location (Table I and Figs 9-
12). In some instances, undermining at a more
superficial anatomic depth than the excision can
minimize morbidity. For example, if excision of the
temporoparietal fascia is necessary to clear a tumor
on the temple, the surgeon may decrease morbidity
to the underlying temporal branches of the facial
nerve by undermining the edges of the reconstruc-
tion superficial to the temporoparietal fascia.
The extent of undermining varies according to the
procedure. For primary closures, wide undermining
rarely increases mobility of the skin edges. Minimal
undermining (ie, 0.5-1.0 cm) will usually suffice.
For deep wounds or very loose skin (eg, on the
forearm or lateral aspect of the neck), undermining
may not be necessary. Fascial plication sutures
can advance tissue and decrease undermining re-
quirements.14
To decide whether undermining is
necessary, the surgeon can use a skin hook to pull
the incised wound edge to its desired position.
If underlying adhesions restrict mobility or fix
the skin in an inverted position, undermining will
help. Undermining is most beneficial in areas
where the fascia and the underlying dermis have
dense connections (eg, the muscles of facial expres-
sion inserting in the dermis at the apical triangle of
the lip).
Undermining influences the vascular supply and
mobility of the flap. The vascular supply to the flap
varies according to anatomic plane and the extent
of undermining. Flaps elevated too superficially
(eg, immediately subdermal) may not have adequate
blood supply.15
To optimize blood supply, local
flaps should contain at least the epidermis, dermis,
and the tight columnar cells of subcutaneous
fat immediately adherent to the dermis (Fig 9).
Undermining deep to muscle or fascia improves
flap blood supply but may increase morbidity,
depending on the anatomic location of the surgery
(Table I). For example, in the central face (eg, the
nose and central forehead) and scalp, undermining
deep to the muscles of facial expression or galea,
respectively, is desirable in most cases (Figs 11 and
12). By contrast, on the lateral aspect of the face,
temple, and posterior triangle of the neck,
undermining superficial to the SMAS and investing
fascia of the neck, respectively, preserves function of
the underlying motor nerves (Fig 10).
Undermining too widely can threaten a flap’s
blood supply or increase the possibility of
postoperative bleeding and hematoma forma-
tion.16-18
In general, the surgeon should aim to
undermine just enough to move the flap into place.
Frequent assessment of skin edge mobility while
undermining helps to avoid unnecessarily wide
undermining. When the skin edges comfortably
stretch to their desired target, additional undermin-
ing is rarely helpful or necessary.
Sharp undermining improves efficiency. With a
thorough knowledge of anatomy, the surgeon can
undermine sharply and with confidence. Compared
to the scalpel, scissors allow sharp undermining with
better tactile feedback. The scissors precisely release
the skin at the desired surgical plane. After the initial
releasing cut, the surgeon can efficiently undermine
the remaining skin by sliding 1 blade of the scissors
in the newly released space and by using the second
blade to complete the cut (Fig 15). Using this slide
Fig 15. Sharp undermining improves operative efficiency.
When working in efficient surgical planes, sharp under-
mining occurs with ease. This photograph shows the
practice of sliding 1 blade of the tissue scissors in the
desired surgical plane, then using the second blade to
complete the release. Using this slide and divide technique
of undermining, the surgeon does not have to rediscover
the preferred undermining plane with each new cut.
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10. and divide technique,19,20
the surgeon does not have
to rediscover the preferred undermining plane with
each new cut. Blunt undermining may be preferred
where fascial planes are being separated, such as on
the dorsal surface of the hand or under the galea of
the scalp. These avascular planes may be split simply
by inserting the closed tips of the scissors in the
desired plane of undermining then spreading the
instrument.
Countertraction with skin hooks greatly facilitates
undermining. Compared to forceps, skin hooks
allow forceful countertraction of the skin without
epidermal trauma. The skin hook should be placed
firmly at the desired depth of undermining (usually
firmly under the dermis) immediately over the point
of undermining. If the skin hook is placed too
superficially (eg, in the mid-dermis), the instrument
tends to slip from the skin. If the skin hook is placed
remotely from the point of undermining with the
scissors, the forces of countertraction diminish and
undermining is more difficult. Therefore, as the
scissors progress to a new spot, the retracting skin
hook should follow. When undermining is
complete, there is often a bevel of subcutaneous fat
along the incised face of the skin edge. Tissue
scissors can be used to trim this fat bevel flush with
the dermis (Fig 7, B).
Goal of undermining
The goal of undermining is to facilitate
advancement of skin edges by releasing the skin
edges from underlying adhesions and to facilitate
eversion of the wound edges during suturing.
Quality control checkpoints for undermining
1. Is undermining effortless, and does it cause
minimal bleeding?
a. Troubleshooting #1—If undermining is
difficult, reassess the surgical plane (Table I).
Resistance during undermining frequently
occurs from working in a suboptimal surgical
plane.
b. Troubleshooting #2—If undermining is
difficult, evaluate whether countertraction
was performed effectively. Efficient under-
mining requires forceful countertraction
directly over the point release. Undermining
will feel difficult if countertraction is either
absent or remote from the exact point of
undermining.
2. Can the incised skin edge be retracted in an
everted position?
a. Troubleshooting—If a skin hook cannot
retract the skin edge in an everted position,
then connective tissue adhesions will likely
force the wound edge in an inverted position.
The wound edge may need additional
undermining before suturing. Wide under-
mining rarely facilitates eversion.
3. Are the wound edges sharply perpendicular from
the epidermis to the plane of undermining?
b. Troubleshooting—After undermining, there is
often a bevel of subcutaneous fat along the
incised face of the skin edge. Tissue scissors
can be used to trim this fat bevel flush with
the dermis (Fig 7, B).
Common errors in undermining
1. Undermining in a suboptimal surgical plane
2. Undermining without effective countertraction
3. Insufficient undermining that restricts eversion of
the incised wound edge
4. Failure to trim the fat bevel to create sharply
perpendicular wound edges after undermining
Fig 16. The wound edges have been undermined in the
same surgical plane as the base of the excision. In this case
on the temple, the surgical plane is at the junction of the
subcutaneous fat and the superficial musculoaponeurotic
system.
Fig 17. Upon final inspection from the cutting steps, the
surgeon should observe a wound with cleanly incised,
vertical wound edges, a wound base uniformly located at
the preferred anatomic plane, and skin flaps undermined
enough to allow advancement and eversion of the wound
edges.
J AM ACAD DERMATOL
MARCH 2015
386 Miller, Antunes, and Sobanko

11. CONCLUSION
The initial steps to cutaneous surgery require
cutting, including incising, excising, and under-
mining. After the cutting steps, the ideal wound has
cleanly incised, vertical wound edges, a base at a
uniform anatomic plane, and precisely undermined
skin edges (Figs 16 and 17). Part I of this continuing
medical education article provided quality
control checkpoints and troubleshooting solutions
to address common challenges during incision,
excision, and undermining to help surgeons create
wounds ideally suited for repair with precise and
efficient buried and superficial sutures.
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Answers to CME examination
Identification No. JA0315
March 2015 issue of the Journal of the American Academy of Dermatology.
Miller CJ, Antunes MB, Sobanko JF. J Am Acad Dermatol 2015;72:388.
1. c
2. b
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