Flaps Practical Reconstructive Surgery

278
II Reconstructive Flaps A-to-Z
a
b
Fig. 23.13 (a) Large fasciocutaneous defect centered over the angle of the mandible after marginal mandibulecto-
my, parotidectomy (inferior), and modi ed radical neck dissection of levels I–V. The bony defect is not structurally 
signi cant and therefore does not require functional reconstruction. Therefore, the defect requires only fasciocuta-
neous reconstruction unless the loss of the angle of the mandible is of aesthetic concern for the patient (not for this 
patient). (b) The stump of the marginal mandibular branch of the facial nerve is evident as a small round structure 
between the retractor and forceps. This requires reconstruction prior to fasciocutaneous closure. (continued)

23 Design, Principles, and Variations of Keystone Flaps
279
Fig. 23.13 (continued) (c) A greater auricular nerve graft has been performed to reconstruct the marginal man-
dibular branch of the facial nerve and is visible just above the mandible. (d) A modi ed keystone perforator island 
ap has been marked to run transversely, inferior to the defect, with the two straight lines of the  ap running from 
the upper convex curve of the primary defect to lie within the submental crease and near the anterior border of 
the trapezius muscle. The V-Y points are both low within the neck laterally and across the midline with the larger 
curvilinear incision of the  ap running within the lower neck skin creases. The upper part of the  aps (the two ends) 
has been elevated to permit the formation of an omega variant of the keystone  ap. (continued)
c
d

280
II Reconstructive Flaps A-to-Z
Fig. 23.13 (continued) (e) Upon transposition, the general layout of the  ap starts to become visible, as is the 
placement of the surgical scars within skin creases where possible. (f) Following formation of the omega variant 
ap and trimming of the dog ear it produces, deep dermal sutures are placed in strategic positions (strategic 
mattress sutures) to ensure even tension and the closure is ready for continuous subcuticular sutures or running 
horizontal everting mattress sutures.
e
f

23 Design, Principles, and Variations of Keystone Flaps
281
be draped over the sharp pretibial border. Ipsilateral aps from
the posterior margin are typically more e ective.
Suggested Further Reading
Behan FC. The Keystone design perforator island ap in reconstructive
surgery. ANZ J Surg 2003;73:112–120
Behan FC, Findlay MW, Lo CH. The Keystone Perforator Island Flap Con-
cept. Chatswood NSW: Elsevier Australia; 2012
Behan FC, Rozen WM, Lo CH, et al. The om ega - Omega - variant designs
(types A and B) of the keystone perforator island ap. ANZ J Surg
2011;81:650–652
Behan FC, Rozen WM, Tan S. Yin-Yang aps: the m athematics of two key-
stone island aps for reconstructing increasingly large defects. ANZ
J Surg 2011;81:574–575
Behan FC, Sizeland A. Reiteration of core principles of the Keystone island
ap. ANZ J Surg 2006;76:1127–1129
Behan FC, Wilson J. The principle of the angiotome, a system of linked
axial pattern aps. In: Sixth International Congress of Plastic and
Reconstructive Surgery. Paris; 1975
Garalevicius S. Mem ory prediction fram ework for pattern recogni-
tion: performance and suitability of the bayesian model of visual
cortex. Proceedings of the 20th International FLAIRS Conference.
Florida; 2007
Mesic H, Kirkeboen KA, Bains R. The importance of a skin bridge in periph-
eral tissue perfusion in perforator aps. Plast Reconstr Surg 2012;
129:428e–434e
Murray SO, Kersten D, Olshausen BA, et al. Shape perception reduces
activity in human prim ary visual cortex. Proc Natl Acad Sci U S A
2002;99:15164–15169
Rubino C, Coscia V, Cavazzuti AM, et al. Haemodynamic enhancement in
perforator aps: the inversion phenom enon and its clinical signif-
icance. A study of the relation of blood velocity and ow between
pedicle and perforator vessels in perforator aps. J Plast Reconstr
Aesthet Surg 2006;59:636–643
Taylor GI, Palm er JH. The vascular territories (angiosomes) of the body:
experimental study and clinical applications. Br J Plast Surg 1987;
40:113–141
Taylor GI. The blood supply of the skin. In: Thorne CH, Bartlett SP, Beasley
RW, et al. (eds.) Grabb & Smith’s Plastic Surgery. 6th ed. New York:
Lippincott, Williams & Wilkins; 2006
Wilson JL, Rozen WM, Ross R, et al. The superior thyroid artery perfora-
tor ap: anatomical study and clinical series. Plast Reconstr Surg
2012;129:641–646
Figure Credits
1. Behan FC. The Keystone design perforator island ap in reconstructive
surgery. ANZ J Surg 2003;73:112–120
2. Behan F, Findlay MW, Lo CH. The Keystone perforator island ap con-
cept. Chatswood NSW: Elsevier Australia; 2012
of all other locoregional aps. This approach is subtly yet funda-
mentally di erent from m icrosurgery-based free tissue transfer
and requires speci c, focused training for expertise.

Hints and Tips
Consider vascular imaging in the setting of marked peripheral
vascular disease, trauma, and/or previous extensive surgery. De-
spite the robust nature of keystone aps and the putative helpful
e ects of islanding on ap perfusion, these conditions can a ect
blood ow to regions of the skin. Extensive undermining during
previous surgery, as may be found in some forms of neck dis-
section, can divide normal perforators. Following wound healing,
neovascularization ensures su cient blood supply to the skin,
but aps needing to rely on a speci c perforator may fail if that
perforator has not adequately reconstituted.
Consider using trimmed excess ap edges (defect side) as
full-thickness skin grafts when tension is too high following clo-
sure. Typically, areas of skin grafting do not need to be very large,
and the avoidance of an additional donor site is preferable.
Adapt the shape and mobilization of the ap to match the local
area and available tissue. When reconstructing convex regions (e.g.,
over the check, knee, etc.), transposition and omega variant aps
inherently re-create convexity. Advancement aps do not re-create
such convexity, but the two approaches can be combined (advance-
ment of the whole ap followed by transposition of the end). Asym-
metrical aps are useful where there is a disproportional amount
of tissue at one end of the ap relative to the other. In the leg, it is
common to make the upper end of the keystone ap larger and the
lower end smaller based on the available tissue for reconstruction.
Avoid trying to raise keystone perforator island aps in re-
gions of direct vessel supply or no perforators. In the scalp, it is
essential to maintain the subcutaneous direct cutaneous vessels
within the ap; therefore, considerable care should be undertak-
en while islanding the ap. The corollary is that the undersurface
of these aps can be fully elevated without risk to the ap’s vas-
cularity. The subcutaneous border of the tibia has no perforators;
therefore, defects that adjoin this region should not be recon-
structed by aps from the contralateral side where the ap must

Keystone Flaps for Lower Limb
Reconstruction
Michael W. Findlay, Dom inik Duscher, and Gordon K. Lee
24
282

Special Considerations
for Keystone Flaps in the
Lower Limb
Reconstruction in the lower limb poses a number of challenges
relative to reconstruction elsewhere in the body. Legs are in a de-
pendent location relative to other parts of the body and, therefore,
have additional hemodynam ic and tissue pressure challenges,
such as lymphedema and varicose veins. The lower limb houses
the longest and most distant neurovascular structures in the body,
and therefore, these are at the greatest risk for diseases, such as
peripheral vascular disease and diabetes mellitus, which can pro-
vide additional challenges to surgical reconstruction. As our pri-
mary means for weight bearing and mobilization, limitations on
postoperative mobilization and any splinting can be signi cant
impositions on normal life and well-being, particularly in the
elderly where immobilization can result in deconditioning and
the need for either rehabilitation or the risk of prolonged immo-
bility with attendant e ects on quality of life and life expectancy.
Despite these challenges, reconstruction in the lower lim b,
particularly forms that provide early functional recovery, can be
highly rewarding. Historically, there has been an over-reliance on
skin grafting followed by prolonged strict bed rest; however, with
increased ambulatory surgery, the reconstructive paradigm has
shifted to locoregional ap reconstruction where possible. A myr-
iad of locoregional ap designs have been described. As a single
ap, the keystone ap provides a simple, reliable reconstruction
that is readily adaptable to meet the reconstructive needs of low-
er extrem ity defects. An understanding of the septocutaneous
blood supply to the lower limb skin is useful to permit safe key-
stone ap use. Once understood, the lower lim b is a very useful
region in which to gain expertise in the use of the keystone ap.

Vascular Pedicles and
Blood Supply in the
Lower Limb
Perforators supply the majority of blood to the skin of the lower
limb with common patterns in perforator number and posi-
tion being well recognized. However, the emphasis on micro-
surgery within reconstructive surgery training has led to an
underappreciation for the number and size of perforators in many
areas, especially around the knee. Vascular studies have demon-
strated numerous large septal perforators that are present with a
large number of smaller perforators in dominant-subordinate or
codominant relationships. The predictability and longitudinal ar-
rangement of the majority of lower limb perforators readily lends
itself to the use of keystone perforator island aps (KPIFs) oriented
parallel to the axis of the limb. As in many other areas, the use of
dermatomes is a useful aide-memoire. The blood supply and main
perforators of the lower limb are illustrated in Figs. 24.1 and 24.2.

Speci c Subregions
and Indications in the
Lower Limb
Thigh
Signi cant tissue elasticity and/or redundancy in this region
make it a very useful place to undertake locoregional reconstruc-
tion. The m ajor blood supply to the thigh skin passes through
muscular or septocutaneous perforators (Fig. 24.1), but there are
also well-known direct cutaneous vessels in the groin and pos-
teriorly in association with the posterior cutaneous nerve of the
thigh. Large aps can be raised using perforators in this region.
Keystone reconstruction in this region is typically well under-
stood by m icrosurgical trained surgeons due to the m any sim ilar-
ities in planning for ap elevation between free ap surgery and
locoregional reconstruction. Other locoregional aps used in this
region include those based on the deep inferior epigastric artery
(traverse rectus abdominis myocutaneous [TRAM], vertical rec-
tus abdominis myocutaneous [V-RAM], deep inferior epigastric
perforator [DIEP] aps), and these should be actively considered
as one of the treatment options.
Groin defects after dissection due to lymph node metasta-
sis are encountered in high numbers in reconstructive surgical
practice. Due to the need for adjuvant chemotherapy, reliable and
robust fasciocutaneous ap coverage is mandatory. Often these
defects can be addressed by the use of a quadriceps keystone ap
based on the perforators of the lateral circum ex femoral vessels,
along with neurovascular supply via the anterior and lateral cu-
taneous nerves of the thigh (Fig. 24.3).
Knee Region
Five vessels contribute to the geniculate anastom osis around
the knee and all but one provides vessels to supply the overlying
skin. For this reason, the cutaneous blood supply around
the knee is well suited to locoregional ap reconstruction.

24 Keystone Flaps for Lower Limb Reconstruction
283
External pudendal
artery
Lateral femoral
cutaneous nerve
Anterior superior
iliac spine
Inguinal
ligament
Superficial
epigastric artery
Superficial
circumflex iliac
artery
Tensor
fasciae latae
Ilopsoas
Femoral nerve
Femoral artery
Femoral vein
Deep artery
of thigh
Sartorius
Iliotibial tract
Quadriceps
femoris
Fascia lata
Arterial network
of the knee
Spermatic
cord
Pectineus
Adductor
longus
Gracilis
Adductor
magnus
Descending
genicular artery
Fig. 24.1 Blood supply and sites of emerging perforators of the thigh, (a) anterior and (b) posterior.
The spheres mark the location of common sites of cutaneous perforators with the size of the spheres
indicating the relative perforator size. Note the longitudinal, septocutaneous arrangement of these perfora-
tors that facilitates longitudinally oriented aps that are mobilized transversely where possible.1 (continued)
a

284
II Reconstructive Flaps A-to-Z
Superior
clunial nerves
Gluteal fascia
(gluteus
medius)
Middle
clunial
nerves
Gluteus
maximus
Inferior
clunial
nerves
Adductor
magnus
Posterior
femoral
cutaneous
nerve
Fascia lata,
iliotobial tract
Gracilis
Semi-
tendinosus
Posterior
femoral
cutaneous
nerve
Semimembranosus
Popliteal
artery and vein
Biceps femoris,
long head
Tibial nerve
Common
fibular
nerve
Lateral sural
cutaneous
nerve
Medial sural
cutaneous nerve
Iliohypo-
gastric nerve,
lateral branch
Fig. 24.1 (continued)
b

24 Keystone Flaps for Lower Limb Reconstruction
285
Patella
Pes anserinus
( Insertion of satorius,
gracilis, and
semitendinosus)
Gastrocnemius
Tibialis
anterior
Muscular
branches
Deep fibular
nerve
Anterior tibial
antery and vein
Soleus
Superior extensor
retinaculum
Medial
malleolus
Dorsal pedal artery
Extensor
hallucis brevis
Tendon of
extensor
hallucis longus
Deep fibular
nerve
Head of fibula
Patellar ligament
Fibularis longus
Plane of
section in C
Extensor
hallucis longus
Extensor
digitorum longus
Superficial
fibular nerve
Fibularis brevis
Inferior extensor
retinaculum
Lateral dorsal
cutaneous nerve
Intermediate dorsal
cutaneous nerve
Medial dorsal
cutaneous nerve
Dorsal metatarsal
arteries
Fig. 24.2 Blood supply and common positions of perforators of the lower leg with
the spheres indicating their relative size: (a) anterior, (b) lateral, and (c) posterior.
These numerous perforators run in a longitudinal, septocutaneous direction that
readily supports longitudinally oriented aps that are mobilized transversely. As in
the thigh, these roughly follow the dermatomes in this region.1 (continued)
a

286
II Reconstructive Flaps A-to-Z
short
head
Long
head
Lateral sural
cutaneous nerve
Common
fibular nerve
Head of fibula
Lateral sural
cutaneous
nerve
Gastroc-
nemius
Medial sural
cutaneous
nerve (tibial
nerve)
Commu-
nicating
branch
Soleus
Sural nerve
Fascia of the leg
Lateral
malleolus
Lateral
calcaneal
branches
Biceps
femoris
Iliotibial
tract
Patella
Lateral tibial
condyle
Anterior crural
intermuscular
septum
Deep fibular
nerve
Superficial
fibular nerve
Fibularis
longus
Tibialis
anterior
Extensor
digitorum
longus
Superficial
fibular nerve
Medial dorsal
cutaneous
nerve
Intermediate
dorsal
cutaneous nerve
Lateral dorsal
cutaneous nerve
Deep
fibular
nerve,
cutaneous
branch
Fig. 24.2 (continued)
b

24 Keystone Flaps for Lower Limb Reconstruction
287
Semi-
tendinosus
Semi-
membranosus
Tibial nerve
Great
saphenous
vein
Fascia
of the leg
(cut edge)
Small
saphenous
vein
Saphenous nerve
Tibial nerve,
medial calcaneal
branch
Biceps
femoris
Plantaris
Common
fibular nerve
Medial sural
cutaneous nerve
Lateral sural
cutaneous nerve
Gastrocnemius,
lateral head
Communicating
medial head
Gastrocnemius,
branch
Sural nerve
Dorsal cutaneous
nerve of the foot
Fig. 24.2 (continued)
c

288
II Reconstructive Flaps A-to-Z
Fig. 24.3 The quadriceps keystone ap for groin defect reconstruction. (a) A 10 3 17 cm cutaneous defect is marked out for resection with exposure
of the femoral vessels as a result. Rapid, reliable fasciocutaneous closure is essential. (b) Following resection, tension sutures are placed across the de-
fect to promote creep. Attempted closure of this wound would result in high risk of wound dehiscence. (c) A quadriceps keystone ap is designed with
asymmetrical limbs, V-Y points laterally, and the design planned to run in the midlateral line laterally and relaxed skin tension lines superiorly and infe-
riorly. (d) The quadriceps keystone ap is formed but the skin is not fully islandized due to the reliable nature of the blood supply (multiple perforators
supplying this ap) and the elasticity of the tissues within this individual. (e) Full fascial islandizing is undertaken with this medial view demonstrating
division of the deep fascia that allows the visualization of a perforator emerging lateral to the underlying muscle belly. (f) Lateral view demonstrating
mobilization of the deep fascia from the fascia lata. (g) Continuation of the fascial islandizing with the use of scissors under the skin bridge. (h) The
primary defect is readily able to be closed following full fascial islandizing. (continued)
b
a
c
e
g
d
f
h

24 Keystone Flaps for Lower Limb Reconstruction
289
Fig. 24.3 (continued) (i) Redundant ap tissue (marked with dotted lines) can now be trimmed and V-Y advancement performed on the upper and low-
er lateral borders. (j) Closure is simple using strategic mattress sutures. The natural convexity of the region will minimize residual contour irregularities
medially and laterally in the rst few postoperative months and the incisions are largely con ned to skin creases or the midlateral and midmedial lines.
The avoidance of full skin islandizing in the center of the lateral ap margin breaks up this scar, decreasing its visibility.
i
j
Careful consideration m ust be given to the potential for ten-
sion across any surgical suture lines, especially with movement.
Therefore, the balance between m obilization and healing m ust
be considered, especially where prolonged immobility may result
in prolonged joint sti ness. Despite these challenges, keystone
reconstruction around the knee can be highly successful due to
the sim ilar tissue characteristics. Fasciocutaneous locoregional
reconstruction around the knee permits the avoidance of muscle
sacri ce (e.g., gastrocnemius aps) and the di culties in nding
recipient vessels for free ap reconstruction. The convex nature
of pre-patellar region readily lends itself to transposition variants
of keystone aps (Fig. 24.4).
Leg
The lower leg is the most com m on area requiring reconstruction
in the lower limb. This is due to the high incidence of trauma,
especially to the pretibial border of the leg in the elderly, com -
bined with the increased skin cancer rates in this region relative
to other areas of the lower limb secondary to sun exposure.
Fig. 24.4 Keystone reconstruction of the peripatellar region. (a) A 3 3 4 cm defect is present with exposed patella. Direct closure would have a very
high risk of wound dehiscence upon mobilization. (b) An asymmetrical keystone ap is designed lateral to the defect with the distal end planned for
transposition to re-create the convexity over the patella. (c) Distal elevation of the keystone ap and mobilization of the tissue inferior to the defect per-
mit closure of the secondary and primary defects simultaneously. (d) Transposition of the ap to demonstrate su cient tissue for closure. (continued)
b
d
a
c

290
II Reconstructive Flaps A-to-Z
Fig. 24.4 (continued) (e) Following closure of the secondary defect, the ap is too long and needs to be trimmed distally. (f) After trimming the distal
ap, the inset is complete with good re-creation of the natural convexity using local tissue.
f
e
For the purposes of reconstructive planning, the leg is often
divided up into regions. The pretibial border is usually consid-
ered separately and often managed by the use of skin grafting.
Keystone ap reconstruction can be very useful for pretibial
reconstruction because it permits early mobilization, shortens
postoperative care, and limits donor morbidity to the a ected
area (Fig. 22.3).
For more general reconstruction, the leg is often divided into
upper, middle, and lower thirds, particularly when seeking to
undertake coverage of fractures or orthopedic hardware in trau-
ma. In the upper third, the gastrocnem ius ap is often used; in
the middle third, the soleus m uscle; and free tissue transfer is
used in the distal third due to the minimal donor tissue in this
region. Where only fasciocutaneous reconstruction is required,
keystone and related perforator-based aps are a low-m orbidity
option for many lower limb defects, especially in our aging pop-
ulations. Reconstruction in the lower third of the lower limb is
challenging because the tissue has limited elastic stretch and a
very small circumference that is not overlying bone or tendons
directly. For many surgeons, this means that free tissue transfer
is the standard of care for m odest-sized fasciocutaneous defects
in this region. However, with careful patient selection and plan-
ning, perforator-based keystone aps can be used. Distal trans-
position (type II) keystones work well in this region w ith the use
of redundant ap tissue as a small full-thickness skin graft to the
secondary defect if necessary. This approach signi cantly lim -
its morbidity and reconstructs the defect with locally matching
tissue (Fig. 24.5).
Fig. 24.5 Reconstruction of a 5 3 2.5 cm defect over the lateral malleolus
with exposed tendon. (a) The loss of periosteum and paratenon in
this region has precluded the use of skin grafts for reconstruction.
(b) A perforator-based keystone ap is designed posterior to the defect
with a plan to transpose the distal end of the ap. (c) The conjoint blood
supply to the ap is demonstrated by maintaining the sural nerve and
short saphenous vein distally with dissection of these to free them distally
into the intact tissue of the foot to increase their mobility. (continued)
a
b
c

24 Keystone Flaps for Lower Limb Reconstruction
291
Skin grafting is not ideal because of the risk of graft loss
w ith early m obilization, the reduced tensile strength of skin
grafts relative to aps in areas that m ust be able to sustain the
daily use of footwear, and the contracture associated w ith graft
healing, w hich can a ect foot, ankle, and general m obility.
The plantar aspect has glabrous skin w ith a very strong fas-
cial system anchored to the plantar fascia w ith adipose tissue
in between to provide cushioning and m inim ize shear forces
during standing and walking. Num erous perforators em erge
in this region to supply the overlying plantar surface, but care
m ust be taken to perm it su cient m obilization of any ap in
this region by dividing the fascial structures, w ithout signi -
cantly injuring the blood supply or a ecting protective sensa-
tion. The m edial instep is a very useful donor site for aps for
plantar reconstruction. The foot is one of the earliest areas of
the body to be a ected by reduced blood supply and therefore
an assessm ent of the vasculature is essential before reconstruc-
tion in this region.

Technique in the
Lower Limb
Step 1: Choice of Anesthesia and
Tourniquet
A tourniquet can be useful in lower limb surgery as it minimizes
intraoperative blood loss, facilitates the identi cation of neuro-
vascular structures, and permits assessment of the site. However,
the m ajority of aps can be undertaken without the need for a
tourniquet and its additional anesthetic demands. Keystone aps
are generally well tolerated by patients, especially compared
with split-thickness skin grafting. For this reason, the use of local
anesthetic, either locally or as part of a regional block, is ideal. If
closure of the defect is anticipated to be di cult, the use of re-
gional blockade is preferable to direct in ltration as the injection
volume of the anesthetic agent can increase tissue turgor, thereby
limiting viscoelasticity.
Signi cant, reliable cutaneous perforators are present both
medial and lateral to the pretibial border. However, the leg is also
one of the areas of the body most a ected by arterial and venous
disease. Preoperative assessment and optimization of these con-
ditions is highly useful to maximize clinical outcomes. The per-
forators themselves are rarely a ected in macroangiopathy, but
the vessels that supply them may be actively a ected, precluding
locoregional reconstruction if vascular bypass is not possible. The
saphenous and sural nerves are often included within aps in this
region (without dividing them) to promote conjoint supply. Despite
the robust nature of keystone aps, the sharp subcutaneous border
of the tibia and the Achilles tendon can a ect aps raised from the
contralateral side of these structures where they are draped across
them. For this reason, ipsilateral reconstruction is advisable.
Also, planning for closure of both the prim ary and secondary
defects is important in order to avoid the use of skin grafts where
possible as these can be adversely a ected by early mobilization.
Low-m orbidity approaches such as keystone aps that maxim ize
early mobilization should always be considered the gold standard
in leg reconstruction.
Foot
In many ways, the hand and the foot share a lot of similarities.
The dorsal surface of each has thinner hair-bearing skin often
with minimal subcutaneous tissue present to cover the under-
lying extensor tendons and neurovascular structures. The blood
supply to the skin is often via perforators that emerge between
these tendons and the venous drainage is based on a super cial
system of veins that pass subcutaneously through this region
to the wrist and ankle, respectively. In general, these structures
are longitudinal; therefore, like other regions in the body, aps
are generally oriented longitudinally and movement is directed
transversely to facilitate closure. Fasciocutaneous defects with
tendon exposure on the dorsum require ap reconstruction and
the availability of pliable tissue in the region readily lends itself
to such reconstruction; however, the marked convexity of the
foot relative to the hand means that aps on the foot should be
overplanned, or larger than thought needed (Fig. 24.6).
Fig. 24.5 (continued) (d) After initial closure, there is redundant ap tissue that can be trimmed and retained as a full-thickness skin graft if required.
(e) The trimmed skin is used to help close the secondary defect (blue sutures), and the defect is easily closed under physiological tension.
d
e

292
II Reconstructive Flaps A-to-Z
Fig. 24.6 Keystone perforator island ap closure of the dorsal foot. (a) A 2.5 3 5 cm defect is marked out on the foot. (b) A keystone ap whose width
is greater than 1:1 with the defect width is planned to try to account for the marked convexity of the region to be reconstructed. (c) Following excision
of the primary defect tissue, the defect and ap width now look more similar. (d) As anticipated, attempted tension suture closure to induce creep is
insu cient to produce probable ap closure of the wound. (e) A second keystone ap is designed on the contralateral side to form a double opposing
keystone ap reconstruction (type IV ap). (f) Following islandization and mobilization of both aps, defect closure looks more promising. (g) Defect
closure is now achievable under physiological tension. (h) Strategic sutures are used to even out tension across the entire ap and thereby maximize
ap reliability and to limit any potential impact on ankle mobility postoperatively.
a
c
e
g
b
d
f
h

24 Keystone Flaps for Lower Limb Reconstruction
293
Step 5: Maintain Subcutaneous
Neurovascular Structures
Numerous longitudinal neurovascular structures pass through
the lower lim b, especially in the leg, including the great and
short saphenous veins, the saphenous nerve, and the sural
nerve, among others. It is useful to retain these in the aps as
they can contribute to arterial supply (conjoint supply) and ve-
nous drainage and where possible, leaving them unharm ed as-
sists postoperative function. Mobilization of these structures
into the surrounding tissues away from the ap provides greater
length to facilitate their mobilization w ith the ap. Where
transposition is to be used, where possible, avoid designing aps
that w ill have to result in the transection of important nerves
like the saphenous nerve. Preoperative discussion w ith the
patient about the potential for num bness in the area supplied
by the nerve in the region should be undertaken if there is any
potential of having to sacri ce the nerve to achieve a di cult or
important defect closure that is not readily achievable through
other means.
Step 6: Release Tourniquet if Used
and Assess Flap Vascularity
Upon release of the tourniquet (if used), it is common to visualize
progressive erythema within the ap starting at the predominant
vascular perforator and then extending progressively through-
out the ap. Typically, fully islanded keystone aps are more
erythem atous than the surrounding skin, a situation that leads
to the phenomenon of the red dot sign (cutaneous suture holes
bleed more often and profusely from the ap side than from the
surrounding skin).
Step 7: Strategic Mattress
Suture and Continuous
Closure to Produce Even
Physiological Tension
The placem ent of interrupted sutures to progressively even out
tension across the whole ap is ideal. This limits focal lines of
tension, maximizes the utilization of creep, and ensures that the
tension is likely to be more physiological at nal wound closure
with important implications for tension-related wound healing.
The phenom enon of pin-cushioning is rare with keystone island
aps, and this may relate to either the geometry of the aps or
the fact that they are inset under physiological tension.
Step 8: Determine Whether
Additional, Small Skin Graft
Is Necessary to Prevent
Supraphysiological Tension
Where excessive tension is present, the removal of a few key
sutures on the secondary defect side of the wound will reduce
Step 2: Defect, Pathology, and
Available Vascular Supply for
Flap and Limb
A thorough assessment of the defect and its available blood sup-
ply is essential prior to considering keystone ap closure. The
size, shape, and site of the defect will determine the most likely
ap size, type of mobilization, and modi cation, with areas of
convexity (e.g., anterior knee, posterior calf) being readily suited
to transposition, rotation, or omega variants that re-create this
convexity. It is important to check for signi cant undermining
around the defect as this may have damaged perforators that
would otherwise supply the adjacent ap. Where signi cant un-
dermining is present, the ap width should be increased to en-
sure the incorporation of suitable perforators to supply the ap.
In patients in whom the blood supply is already tenuous, islan-
dized keystone aps usually do better than nonislandized aps in
our clinical experience due to the gradient inversion e ect and
the ability to ensure even physiological tension upon wound clo-
sure. If the limb is devascularized, ow-through free tissue trans-
fer may be a more suitable option to achieve both defect closure
and revascularization.
Step 3: Mark Out Flap, Determine
Mobilization, and Utilize Creep
Having m arked out the ap usually with its long axis running
longitudinally or at a slight angle to this orientation, it is useful
to insert some pulley sutures or similar tension sutures early to
facilitate intraoperative creep. While this is occurring, the ap
can be raised and the best form of m obilization con rm ed. It is
important to emphasize that ipsilateral aps are best near the
sharp subcutaneous border of the pretibial region because drap-
ing aps from the contralateral side across this sharp edge can
compromise their vascularity.
Step 4: Determine Degree
of Islandization
It is usual to islandize the skin completely; however, in type 1
aps (advancement only), especially in younger patients in whom
scar burden can be a signi cant issue but blood supply to the ap
is usually not, the ap can be islandized only as much as is need-
ed to facilitate closure. The central part of the long curved side
is usually the region spared from full islandization if that is the
case. This still permits V-Y advancement from each of the verti-
ces, but relies upon the viscoelasticity of the skin to even out any
skin tension lines, so maintain blood supply to the entire ap. In
these cases, the fascia can still be divided under this region of
nonislandization through the use of scissors under the skin bridge.
It is best to develop expertise with fully islandized aps, include
with fascial islanding prior to reducing the degree of islanding to
match the needs of the clinical situation. Many proponents of the
keystone ap, including its inventor Felix Behan, routinely skin is-
land every keystone ap due to the potential for increased safety
in the blood supply to the ap with this approach.

294
II Reconstructive Flaps A-to-Z
Step 10: Document the Flap
Type, Outline, and Movement to
Facilitate Reoperation if Required
It can often be di cult to identify the suture lines of keystone is-
land aps following full healing and scar maturation, particularly
in the elderly. Re-operation for incomplete excision or recurrence
or to access underlying bone and orthopedic hardware may re-
quire a thorough understanding of the ap and how it was m o-
bilized. Documentation of the ap design, movement, and blood
supply is very helpful for this as the same ap can be raised and
mobilized further to assist in any reoperative closure. The aps
heal well, and subsequent division of their feeding perforators af-
ter 2 to 4 weeks does not usually lead to skin necrosis as long as
a su cient circumference of healed suture line remains intact.

Hints and Tips
Etiological factors relating to the defect must be resolved prior to
considering ap closure in the lower limb, but this is not always pos-
sible (Fig. 24.7). Tumor clearance, healing of crush-injured tissues,
wound tension and leave an often sm all secondary defect w ith a
clean, vascularized bed suitable for a small skin graft. Typically,
the size of this defect is small enough that the excess keystone
ap tissue at either end of the defect, following advancem ent,
can be trimmed for this purpose without the need to harvest
skin from an alternative site and thereby lim iting additional
morbidity.
Step 9: Assess Need for
Postoperative Splinting by Passive
Movement of Nearby Joints
Following closure, it is ideal to put the surrounding joints through
some passive range of motion while examining the suture lines
and the ap to determine whether full, partial, or restricted mo-
bility is most suitable in the postoperative period. If splinting
is applied, this should not be placed directly over the ap. A
Robert-Jones bandage (a total of six layers that alternate cotton
wrapping and 6-inch crepe bandages used under casts) should be
used. This approach is especially useful in the elderly because it is
very soft, yet limits range of motion of the ankle.
Fig. 24.7 Venous malformation on the left pretibial border of a 23-year-old man, demonstrating repeated episodes of ulceration, prompting his
request for surgical excision. Despite the relatively small cutaneous component, lesions typically involve other structures more widely than clinically
appreciated from the surface. Preoperative imaging showed no involvement of the underlying bone and a limited surrounding blush within the venous
phase. Therefore, excision was undertaken. (a,b) Appearance of the lesion prior to excision. (c,d) Excision is performed outside the lesion with ligation
of multiple large draining veins in the process. The subcutaneous component continued under the surface of the skin. A plane could be developed
between the lesion and the underlying tibia, but not the perimysium of the anterior compartment. (continued)
a
b
c
d

24 Keystone Flaps for Lower Limb Reconstruction
295
degree of concavity produced by the hardware. For example, when
plates and screws are used over the medial or lateral malleoli, this
produces excessive convexity at these points and the change in the
vector of tension within the skin promotes exposure of this hardware
through relatively thin tissues (Fig. 24.8). This is similarly the case if
a thin locoregional keystone ap is used for such coverage. For this
and grossly contaminated wounds should all be addressed before
consideration is given to keystone ap closure. In the setting of neg-
ative pressure wound dressings, including instillation therapy, it is
feasible to delay de nitive ap closure until wounds are suitably
clean. If coverage of orthopedic hardware is necessary, it is import-
ant to assess the thickness of the ap tissue to be transferred and the
Fig. 24.7 (continued) (e) Following excision (with extension to remove the
subcutaneous component), a 6 3 8 cm defect over the tibia was present
(not including the upper incision to gain access to the subcutaneous com-
ponent). There were still numerous ne abnormal vessels present within
the surrounding tissues, increasing the risk of recurrence as discussed with
the patient preoperatively, but complete excision would increase morbid-
ity signi cantly relative to the morbidity at presentation. Therefore, no
further excision was undertaken. The nongraftable bed required ap re-
construction and, despite the numerous ne abnormal vessels, the lowest
morbidity approach was to use a keystone ap. (f) A large, asymmetrical
keystone ap is designed to utilize the existing superior curved incision
with advancement of both upper and lower limbs to each other (omega
variant) to close the defect. The intraoperative course was uneventful, but
as could be anticipated by the residual venous abnormalities, some super-
cial wound ulceration developed in the immediate postoperative period.
This resolved promptly with dressings and suitable compression (g).
e
f
g
Fig. 24.8 Exposed orthopedic screw (and plate) at the medial malleolus of a 62-year-old woman 6 weeks after she was hit by a car and received a bimalle-
olar fracture. The patient had a history of chronic alcoholism, with marked coagulopathy and low albumin making free tissue transfer problematic. Despite
concern about removal of the plates and screws by her orthopedic surgeon, it was agreed that their removal would minimize the risk of ongoing infection
and facilitate defect closure by reducing the convexity of the area for reconstruction (given her very thin surrounding skin). (a) A screw is visible over the
medial malleolus with an incision extending superiorly for the rest of the plate and screws. Strict bed rest, elevation, and negative pressure wound therapy
were instituted prior to operative intervention. (b) At surgery, the existing scar was reopened to demonstrate the exposed plate and screws. (continued)
a
b

296
II Reconstructive Flaps A-to-Z
reason, keystone aps can provide temporary (usually a minimum
of 4 to 6 weeks) coverage of such prominent hardware to facilitate
healing prior to the removal of the hardware but are less ideal when
delayed bony union is expected. In such cases, free tissue transfers
with bulky aps are more advisable for such prolonged coverage.

Clinical Perspectives
Lower limb reconstruction is particularly challenging due to its
weight-bearing, dependent position, which generates additional de-
mands on reconstructive techniques used in this region. The keystone
island ap is able to meet all these challenges. Keystone perforator
island aps have all the advantages of local tissue, including good
skin color, texture, and thickness match. In well-selected cases they
provide a simpler alternative to the more sophisticated free aps by
o ering reliable vascularized soft tissue cover while permitting early
mobilization and good restoration of function and aesthetics.
Suggested Further Reading
Behan FC, Findlay MW, Lo CH. The keystone perforator island ap con-
cept. Chatswood NSW: Elsevier Australia; 2012
Fig. 24.8 (continued) (c) Following removal of the plate and screws, there
is a residual imprint of the plate on the bone and screw holes extending
into the medullary cavity requiring vascularized coverage. Primary closure
was not possible. (d) A posterior tibial artery perforator keystone ap was
designed posterior to the defect with the long curvilinear line designed to
cross the Achilles tendon obliquely to facilitate subsequent closure of the
secondary defect. (e) Following a small amount of V-Y advancement supe-
riorly, the defect closes easily without the need for a secondary skin graft.
The patient healed rapidly despite hypoalbuminemia and her wounds
were no longer a limiting factor in her postaccident management.
c
d
e
Behan FC, Lo CH, Findlay M. Anatomical basis for the keystone island ap
in the upper thigh. Plast Reconstr Surg 2010;125(1):421–423
Behan FC, Terrill PJ, Ashton MW. Fasciocutaneous island aps for
orthopaedic management in lower lim b reconstruction using der-
matom al precincts. Aust N Z J Surg 1994;64(3):155–166
Mesic H, Kirkeboen KA, Bains R. The importance of a skin bridge in pe-
ripheral tissue perfusion in perforator aps. Plast Reconstr Surg
2012;129(3):428e–434e
Pan WR, Taylor GI. The angiosomes of the thigh and buttock. Plast
Reconstr Surg 2009;123(1):236–249
Pelissier P, Gardet H, Pinsolle Y, Santoul M, Behan FC. The keystone design
perforator island ap. Part II: clinical applications. J Plast Reconstr
Aesthet Surg 2007;60(8):888–891
Rubino C, Coscia V, Cavazzuti AM, Canu V, et al. Haem odynamic enhance-
m ent in perforator aps: the inversion phenom enon and its clini-
cal signi cance. A study of the relation of blood velocity and ow
between pedicle and perforator vessels in perforator aps. J Plast
Reconstr Aesthet Surg 2006;59(6):636–643
Taylor GI, Pan WR. An giosomes of the leg: anatomic study and clinical
implications. Plast Reconstr Surg 1998;102(3):599–616
Wei JW, Ni JD, Dong ZG, Liu LH, Luo ZB, Zheng L. The importance of a
skin bridge in peripheral tissue perfusion in perforator aps. Plast
Reconstr Surg 2012;130(5):757e–758e
Figure Credits
1. THIEME Atlas of Anatomy, General Anatomy and Musculoskeletal
System, © Thieme 2005, Illustration by Karl Wesker.

297
Keystone Flaps for Reconstruction in
the Trunk
Michael W. Findlay, Peter C. Neligan, and W illiam M. Kuzon Jr.
25

Introduction
Keystone reconstruction of defects in the trunk is reliable due to
the predom inance of segm entally arranged m usculocutaneous
perforators in this region. The signi cant number of suitable per-
forators makes it possible to raise the largest keystone aps of
anywhere in the body and, in most cases, this makes reconstruc-
tion relatively straightforward. This is a good thing because the
need for defect reconstruction in the trunk is relatively common
in clinical practice. Despite the fact that clothing typically covers
the trunk region for the m ajority of daily activities, interm ittent
excessive sun exposure is not uncomm on, putting this large sur-
face area at risk of developing skin cancer. Nearly half of the trunk
(the back) is not directly visible to the individual and the pres-
ence of clothing m ay result in others not identifying lesions for
some time. Therefore, lesions of any etiology may be larger and
more advanced in the trunk at the tim e of diagnosis than sim ilar
lesions in other areas of the body. For these reasons, the recon-
struction of fasciocutaneous defects in the trunk is com m on and,
when aps are used, they may need to be large.
The trunk represents over one-third of the surface area of the
body and has a number of subregions including the back, lateral
chest, anterior chest, abdomen, buttock, and perineum. Each of
these areas is associated with a region of natural laxity (e.g., lateral
trunk, periscapular region, abdomen) and a ready supply of avail-
able perforators follow common patterns in each of the regions.
The trunk is a common area for the use of large musculocutaneous
aps (e.g., pectoralis major– and rectus abdominis–based aps),
but these myocutaneous aps have greater morbidity than fascio-
cutaneous aps due to the need to harvest them with muscle. Per-
forator aps have become a popular alternative since they allow
aps to be harvested without sacri ce of the underlying muscle
or, indeed, fascia. However, they demand a detailed knowledge
of vascular anatomy as well as a speci c technique for their dis-
section. More recently, the use of the keystone ap has been in-
creasing in the trunk for this reason, with many surgeons not only
using the trunk region to gain experience with this ap but also
going on to demonstrate the usefulness of the keystone ap for
advanced and/or large truncal defects.
The beauty of the keystone ap remains its simplicity. It is
a perforator-based ap that does not require speci c perforator
identi cation or dissection. While m ost reconstructions in this
region can be covered with clothing postoperatively, careful ap
planning can maximize postoperative outcomes including the
minim ization of visible scarring by placing these in speci c ar-
eas such as under the brassiere or within the underwear line.
An understanding of the common types of defects, the nature of
the local blood supply, and the most suitable axes for ap plan-
ning are all very useful for the application of keystone aps in
this region. We examine the common elements in keystone ap
use throughout the trunk and identify the speci c di erences in
approach required in each subregion for e ective use of the key-
stone and related perforator-based aps.

Vascular Pedicles and
Blood Supply in the Trunk
The vast m ajority of the blood supply to the skin of the trunk
arrives through musculocutaneous or septocutaneous perfora-
tors. There is a well-developed system of segmental perforators in
the trunk that makes perforator-based reconstruction relatively
straightforward, but despite this, there are still som e speci c
areas that have either nonsegmental perforators or direct arterial
supply (Fig. 25.1).
Starting posteriorly, the paravertebral region has segmental
supply via the posterior spinal and intercostal arteries with con-
tributions from the dorsal scapular arteries superiorly and the
gluteal vessels inferiorly. Their regular segmental arrangement
makes it easier to predict the position of perforators by looking
for them within the defect and expecting similar perforators in
the segments above and below (e.g., rib above). Moving anteriorly,
numerous perforators emerge either between or directly from
muscle bellies with many showing reliable patterns such as the
angular perforator associated with the latissim us dorsi at the in-
ferior angle of the scapula or the thoracodorsal artery perforators
in the lateral back (Fig. 25.2a). These numerous predictable perfo-
rators ensure the safety of keystone and related aps in the back.
The lateral trunk has both segmental supply through the regular
lateral intercostal perforators and direct vessels such as the lateral
thoracic artery. The ready availability of these vessels as the basis
for fasciocutaneous aps in this region signi cantly aids maximal
use of the elastic lateral chest wall skin for reconstruction of areas
such as the axilla, anterolateral chest, and lumbar region.
The anterior chest is supplied by perforators from the inter-
nal thoracic (internal mammary) arteries (Fig. 25.2b). As m en-
tioned above, previous harvest of the internal thoracic arteries
a ects antegrade ow within the perforators of this region. As a
general rule, keystone aps should be designed to capture adja-
cent intact perforator regions (e.g., anterior intercostal perfora-
tors) when speci c perforators are likely to be missing or ligated.
This is readily achievable in the m ajority of truncal defects due to
the highly predictable, segm ental supply in this region and sig-
ni cant surface area of tissue available in most cases.

298
II Reconstructive Flaps A-to-Z
Fig. 25.1 (a) Transverse section of the trunk demonstrating the segmental nature of the para-
vertebral blood supply via the medial and lateral cutaneous branches of the posterior intercos-
tal arteries. These readily supply paravertebral aps running longitudinally beside the spine.
(b) The anterior continuation of the posterior intercostal arteries provides segmental supply
around the circumference of the trunk via the lateral and anterior intercostal vessels with com-
munication anteriorly with the internal thoracic artery.1
Spinal
branch
Anterior
radicular
artery
Medial cutaneous
branch
Posterior inter-
costal arteries
Posterior
radicular artery
Dorsal
ramus
Thoracic
aorta
Lateral
cutaneous
branch
a
Posterior
intercostal
arteries
Internal
thoracic artery
Sternal
branches
Posterior intercostal
arteries
Collateral
branch
Lateral
mammary
branches
Anterior
intercostal
arteries
Medial
mammary
branches
Perforating branches
Dorsal ramus
Thoracic
aorta
Lateral
cutaneous
branch
b

25 Keystone Flaps for Reconstruction in the Trunk
299
Fig. 25.2 (a) Posterior trunk demonstrating the rich, predominantly segmental nature of the blood supply and cutaneous inner-
vation to the skin and their relationship to the back muscles. (continued)
Thoracolumbar
fascia
Deltoid
Trapezius
Accessory nerve
Transverse
cervival artery
Serratus posterior
inferior
Latissimus
dorsi
Fibrous lumbar
triangle (of Grynfeltt)
External oblique
Internal oblique
Iliac crest
Middle
cluneal nerves
Inferior
cluneal nerves
Superior
cluneal nerves
Iliolumbar triangle
(of Petit)
Intercostal nerves and
posteroir intercostal
vessels, lateral
cutaneous branches
Spinal nerves, dorsal rami
(medial cutaneous branches)
Rhomboid major
Splenius capitis
Third occipital
nerve
a

300
II Reconstructive Flaps A-to-Z
Fig. 25.2 (continued) (b) Anterior trunk demonstrating the rich, predominantly segmental nature of the blood supply and cutaneous inner-
vation to the skin and underlying tissues.1
Lateral thoracic
artery and vein
Internal thoracic
artery and vein
Intercostal artery,
vein, and nerve
Internal
oblique
Rectus
abdominis
External
oblique
Transversus
abdominis
Inferior epigastric
artery and vein
Superficial circumflex
iliac artery and vein
Fascia lata
Cephalic vein
Thoracoepigastric
vein
Superior epigastric
artery and vein
Umbilicus
Superior
epigastric vein
Inguinal ligament
Superficial epigastric
artery and vein
Long
saphenous vein
b

25 Keystone Flaps for Reconstruction in the Trunk
301
thoracodorsal artery), in the abdom inal m idline (epigastric ar-
tery system), near the pelvic girdle (cutaneous branch of the deep
circum ex iliac artery [DCIA], the super cial inferior epigastric
artery and vein [SIEA/V]), and within the buttocks (gluteal ves-
sels) and perineum (internal pudendal artery).
In the buttocks the ready supply of perforators from the
superior gluteal and inferior gluteal arteries makes it relatively
easy to design m usculocutaneous and fasciocutaneous aps in
this region. Any reasonably sized ap in this vicinity will usually
incorporate a number of perforators. While basic keystone aps
can be useful in the management of natal cleft problems, such as
postexcision reconstruction of pilonidal sinuses, most other aps
in this region are only loosely based on the keystone ap design,
but readily follow keystone ap principles.
The neurovascular supply to the perineum is dom inated by
the internal pudendal artery and pudendal nerve to the posterior
two-thirds and the external pudendal artery anterolaterally.
Perforators from either of these vessels make it relatively easy to
use adjacent thigh skin for perineal reconstruction. The internal
pudendal artery passes through the lesser sciatic notch before
turning anteriorly again (through the greater notch) to run for-
ward within the perineum. It can give o branches into the prox-
imal thigh and, for this reason, transposition aps based on these
vessels can be highly useful for vulval reconstruction due to their
combination of reliability and local tissue match (Fig. 25.3).
The internal thoracic arteries continue on after branching
to give rise to the super cial epigastric arteries within the ab-
domen. These ram ify with the deep inferior epigastric vessels
(DIEA) at the midpoint between the xiphoid process and the
umbilicus and the epigastric system as a whole gives rise to nu-
merous perforators that are one of the most intensely studied
group of perforators anywhere in the body as a result of their
use in breast reconstruction and a myriad of other reconstructive
applications as either locoregional aps or free aps. Despite this,
the super cial inferior epigastric artery (SIEA) may be the pre-
dominant supply to the lower abdom inal skin, or the super cial
inferior epigastric vein (SIEV) m ay be the predominant venous
drainage for the tissue with the arterial supply being derived
from the deep inferior epigastric artery (DIEA) via the deep in-
ferior epigastric perforator (DIEP). Laterally, segmental supply
via the continuation of the intercostals and lumbar vessels with-
in the neurovascular plane with regular perforators assists the
elevation and planning of laterally placed aps also. Any keystone
ap in this region uses either no dissection or blunt dissection of
arteries and veins, while focusing on m obilizing all other struc-
tures ( brous septae and fascia, etc.). In this way, the maximum
blood supply possible is delivered to the aps, and all possible
venous drainage is preserved.
Nonsegmental vessels are prominent in the axilla and upper
lateral chest (e.g., lateral thoracic artery, pectoral branch of the
Fig. 25.3 Illustrations of the (a) female and (b) male perineum demonstrating the predominance of the internal pudendal artery and
pudendal nerve supply to the perineum.1 (continued)
Dorsal clitoral
artery and nerve
Anterior
labial branches
Deep
clitoral artery
Artery of
vestibular bulb
Posterior
labial
branches
Ischial
tuberosity
Inferior
rectal vessels
Pudendal
nerve
Internal
pudendal
vessels
Levator ani
Inferior
rectal nerves
Vestibular bulb
Perineal nerves
Bulbo-
spongiosus
Deep
transverse perineal
Ischio-
cavernosus
a

302
II Reconstructive Flaps A-to-Z

Subregions and Keystone
Flap Planning
The trunk includes a num ber of di erent subregions that, in
general, share a perforator-based blood supply and a com -
mon circum ferential derm atom al pattern as m entioned above
(Fig. 25.4). While the dermatomes are a useful aide-memoire for
planning of keystone aps in the majority of the body, reliance
on their use in the trunk can provide mixed results. For example,
in the lateral trunk, they are very useful because they accurately
identify the axial nature of the blood vessels and plexuses but
their use in the back, especially in the m idline, can be fraught due
to the dense fascial attachments of the skin in the midline that
severely limit ap mobilization in a superoinferior direction. In
this region, the paraspinal m uscles run longitudinally with seg-
mental perforators to supply the overlying skin. For this reason,
aps near the midline of the back are typically oriented parallel
to the underlying muscles (perpendicular to the dermatomes) to
maxim ize m ovem ent and facilitate the incorporation of perfora-
tors. This orientation still permits single or bilateral keystones or
reconstruction of midline or paramedian defects with advance-
ment with or without transposition as required. As in other re-
gions of the body, knowledge of the passage of cutaneous nerves
is useful so these may be incorporated within the keystone aps
to provide additional blood supply (conjoint supply) and good
sensation (Fig. 25.5).
The Back
The back is also unique in the trunk with regard to the thick-
ness of the dermis of the back skin. Even in the elderly with
very thin skin, the back has dependable tensile strength to fa-
cilitate ap elevation, mobilization, and closure of both prima-
ry and secondary defects. There are also natural areas of excess
skin around the scapula, laterally over the latissimus dorsi mus-
cle (Fig. 25.6), and on either side of the spine (Fig. 25.7). Many
surgeons use the back to gain the necessary experience in locore-
gional reconstruction due to the combination of these character-
istics. As mentioned, however, it is important to take into account
the variability of the axis of aps within the back—especially in
the periscapular region where the axis often curves around the
medial border of the scapula. When designing aps around the
shoulder and scapular regions, it is important to be cognizant of
the potential impact of the scar on m ovement of the shoulder
girdle. The axis of keystone and related perforator aps is more
consistent in the lim bs, and therefore, the lim bs can be consid-
ered a useful alternative area to develop such expertise.
Fig. 25.3 (continued)
Arcuate pubic
ligament
Corpus
spongiosum
Spermatic
cord
Bulbo-
spongiosus
Posterior
scrotal nerves
Perineal nerves
Anus
Inferior
rectal nerves
External anal
sphincter
Gluteus
maximus
Corpora
cavernosa
Deep dorsal
penile vein
Transverse
perineal ligament
Dorsal penile
artery
Dorsal
penile nerve
Muscular branches
Bulbourethral
gland
Ischial
tuberosity
Internal
pudendal vessels
Pudendal nerve
Inferior rectal
vessels
b

25 Keystone Flaps for Reconstruction in the Trunk
303
Fig. 25.4 Pattern of the dermatomes in the (a) anterior and (b) posterior trunk region. These are a useful aide-memoire in keystone ap planning
except in speci c regions of the back (e.g., paraspinal region) where there is little capacity for superoinferior mobilization of the ap due to dense
brous attachments.2
C4

T2
T3
T4
T10
T12
L1
S2
L4
C3
C5
C6
T1
C8
C7
L2
L3
a
S4
S5
S2
S1
S3
T12
T1
C5
C6
C7
C8
C4
C8
C7
C6
C5
C3
C2
T1
T2
T3
L1
L2
L3
L4
L5
b
The Lateral Trunk and Abdomen
The lateral trunk and the abdom en share sim ilar characteristics
in term s of outstanding elasticity and/or laxity to facilitate lat-
eral expansion of the rib cage during breathing and diaphrag-
matic breathing into the lower abdomen, respectively. This
makes locoregional reconstruction in these regions very easy as
long as chest or abdominal wall defects (if present) have been
reconstructed. Closure under m odest tension in this region is
usually safe because of the excellent viscoelasticity of the skin.
The abdom inal skin has sim ilar elasticity as the lateral trunk, but it
is m ore likely to be adversely a ected by previous surgery and/or
marked adiposity that can complicate the reliable incorporation
of perforators within aps, particularly in the “ battle-scarred”
abdomen. Current or previous stoma sites can also limit available
forms of movement for aps in this region. The gold standard of
reconstruction of the anterior abdomen necessitates m anage-
m ent of the abdominal wall (e.g., component separation, mesh
repair) with fasciocutaneous reconstruction over this layer. It
is important to emphasize that keystone and related perforator
aps do not adequately reconstruct the abdom inal wall itself,
but can provide excellent soft tissue coverage including as a vi-
able alternative to split-thickness skin grafts in problem atic and
advanced cases requiring fasciocutaneous reconstruction alone.

304
II Reconstructive Flaps A-to-Z
a
Intercostal nerves,
lateral cutaneous
branches
Supraclavicular
nerves
Intercostal nerves,
anterior cutaneous
branches
Iliohypogastric nerve,
anterior cutaneous
branch
Genitofemoral nerve,
femoral branch
Ilioinguinal nerve
Iliohypogastric nerve,
lateral cutaneous
branch
Lateral femoral
cutaneous nerve
Femoral nerve, anterior
cutaneous branches
Fig. 25.5 (a–c) These illustrations demonstrate the passage and supply of the cutaneous nerves as the basis for their incorporation as neurovas-
cular keystone island aps (conjoint supply) for the (a) anterior trunk, (b) posterior trunk, and (c) perineum (including the dermatomal supply,
respectively).2 (continued)

25 Keystone Flaps for Reconstruction in the Trunk
305
Greater
occipital nerve
Lesser occipital nerve
Great auricular
nerve
Supraclavicular
nerves
Intercostal nerves,
lateral cutaneous
branch
Iliohypogastric
nerve, lateral
cutaneous branch
Lateral femoral
cutaneous nerve
Spinal nerves,
dorsal rami
(medial cutaneous
branches)
Spinal nerves,
dorsal rami
(lateral cutaneous
branches)
Superior cluneal
nerves
Middle cluneal nerves
Inferior cluneal
nerves
Posterior femoral
cutaneous nerve
b
Fig. 25.5 (continued)

306
II Reconstructive Flaps A-to-Z
Pudendal nerve
L2
S3
S4
S5
Co1
S2
Anococcygeal
nerves
Middle
cluneal nerves
Superior
cluneal nerves
Inferior
cluneal
nerves
Posterior
femoral
cutaneous
nerve
Ilioinguinal nerve and
genitofemoral nerve,
genital branch
c
Fig. 25.5 (continued)
a
b
Fig. 25.6 (a) A 6 3 7 cm fasciocutaneous defect present over the left scapula requires coverage but cannot be closed directly. (b) Maximal skin
redundancy is present extending to the posterior axillary fold over the latissimus dorsi muscle; therefore, a keystone ap is designed to permit trans-
position of this end of the ap into the defect. (continued)

25 Keystone Flaps for Reconstruction in the Trunk
307
Fig. 25.6 (continued) (c) Following cutaneous islanding, the dissection is continued by blunt dissection, except the lateral end that must be mobilized
su ciently for transposition into the primary defect. (d) Elevation of the lateral half of the ap permits its transposition into the defect and the other
end of the keystone ap can be advanced (by V-Y advancement) to further narrow the defect size. (e) Closure of the secondary defects demonstrates
easy draping of the ap for closure with signi cantly more ap tissue than required following V-Y advancement medially. (f) Following trimming of
the ap excess, the transposition has re-created the natural convexity of the area, the wound edges are under normal physiological tension, and the
wound is ready for ne closure.
c
d
e
f
a
b
Fig. 25.7 (a) Midline defect in the back, 6 3 7 cm in size with exposed spinous processes. (b) The paraspinal musculature runs longitudinally and
permits medial and lateral movement, but limited movement superiorly and inferiorly. Therefore, the axis of the aps must be at right angles to the
dermatomes, unlike most other regions of the body. (continued)

308
II Reconstructive Flaps A-to-Z
Fig. 25.7 (continued) (c) Following islanding with subsequent blunt dissection in the subcutaneous plane, the two aps are ready for de nitive mobili-
zation to close the primary defect. The surface area required to reconstruct this is deceptively large due to the natural concavity in this region. Transpo-
sition or rotational approaches are ideal for curved defect reconstructions. (d) Opposing ends are elevated ready for a yin-yang bilateral transposition
variant of the keystone. (e) Defect closure is readily achieved and the curvilinear midline scar facilitates movement in the early postoperative period.
(f) Completed yin-yang closure showing the V-Y advancement and transposition closure. The contour closely matches the region and, despite the scar,
the local tissue and color match are very acceptable. (g) An intraoperative referral: an example of incorrect orientation of the long-axis of the aps in
the paraspinal region. These were oriented transversely to match the dermatomes, but did not mobilize adequately. The keystone aps were changed
from a direct advancement to a yin-yang variant but required extensive mobilization across the midline, based on the ipsilateral paraspinal perforators
for supply. The closure healed, but patient mobilization was di cult in the immediate postoperative period. In contrast, the example demonstrated
in (f) shows how any vertical suture lines are either curved or show a zig-zag pattern similar to a Bruner incision. This facilitates exion and extension
movements of the spine required for normal daily function (e.g., putting shoes on).
c
d
e
f
g

25 Keystone Flaps for Reconstruction in the Trunk
309
b
d
Fig. 25.8 (a) A 6 3 8 cm periumbilical defect that cannot be closed primarily. The anterior abdominal wall is intact and there is no previous history of
abdominal surgery. (b) A contralateral keystone ap is designed to incorporate the deep inferior epigastric perforators with transposition of the inferior
limb to maintain natural convexity of the region. (c) The keystone ap is islandized and ready for transposition of the inferior limb. (d) The inferior limb is
elevated (only with the anterior rectus sheath if required for abdominal wall closure at the primary defect site) to permit transposition into the primary
defect. The perforators are not speci cally visualized so as to minimize the risk of trauma to them. (e) The inferior limb of the keystone ap readily
transposes into the primary defect. (f) Simple closure under even physiological tension.
a
c
e
f
on speed of progression to potentially life-saving adjunctive
therapies including chem o- and/or radiotherapy. The prim ary
use of the latissim us dorsi m uscle w ith a skin paddle in these
patients rem oves a potential reconstructive lifeboat in the set-
ting of recurrence or a potential option for future breast recon-
struction and m ay result in the need for extensive skin grafting
to provide full skin coverage to the chest wall. This can lead
to slow healing relative to closure w ith a keystone perforator
island ap in a patient population that requires prompt pro-
gression to potentially life-saving adjuvant therapies. Defects
of the anterior chest usually have num erous available perfo-
rators nearby unless previous internal thoracic artery harvest
In speci c cases, parts of the abdom inal wall (e.g., anterior rectus
sheath) can be transferred as part of the ap to assist abdom inal
wall closure at the primary defect (Fig. 25.8).
Anterior Chest and the Breast
Reconstruction of the breast follow ing lumpectomy or m astec-
tomy requires tissue volum e w ith or w ithout skin. Volum e is
not readily provided by keystone or related perforator aps;
however, keystone aps can be highly useful in the setting
of salvage surgery of the breast secondary to advanced m a-
lignancies. In these situations, the emphasis for the patient is

310
II Reconstructive Flaps A-to-Z
Fig. 25.9 (a) A defect following breast salvage surgery with removal of the pectoralis major muscle and a defect; not able to be closed primarily. The ar-
tery forceps indicate the position of a lateral intercostal perforator. (b) An asymmetrical keystone ap is designed inferior to the defect with small black
dots indicating the likely site of the lateral intercostal perforators, based on the site of those above that are visible within the defect. (c) Following islan-
dization of the ap, the anterior part of the ap is elevated in the subfascial plane superior to the costal margin. The lateral intercostal perforators are
the predominant supply to the ap (in front of the blue material). The anterior ap is ready to be transposed in conjunction with rotation-advancement
of the posterior aspect to facilitate defect closure. Note: the perforators have been dissected in this case to demonstrate their consistent segmental
supply. In a clinical case, such dissection is to be avoided so as not to injure the perforators and a ect their function. (d) The primary and secondary de-
fects close easily following transposition of the anterior limb and rotation advancement of the posterior limb, both supported by the lateral intercostal
arteries to facilitate rapid healing and the institution of adjuvant therapies.
a
b
c
d
has lim ited the antegrade ow in these vessels. Where a reli-
able perforator can be found, keystone aps are a viable option
in this region, but the loss of such perforators can preclude
their use for defects such as sm all to m edium sternal wound
dehiscence cases. Keystone aps in this region are highly
useful, but caution should be exercised w hen fully islanding
keystone aps in the region of the sternum , especially in skin
types prone to hypertrophic scar or keloid form ation. The ster-
nal area is a com m on site for keloid form ation, along w ith the
deltoid and periauricular region (Fig. 25.9).
The Buttocks and Perineum
Defects in the buttock region are often the result of chronic
conditions including pressure (ulcers), in am m ation (pilonidal
sinuses), or tumors (e.g., rectal cancer). Reconstruction in this
region is dom inated by the arrangement of the gluteal arter-
ies relative to the buttock musculature, and for this reason the
use of musculocutaneous aps is common here. Keystone aps
are a reasonable alternative and can be combined with muscle
advancement if additional bulk is required. Their geometry and

25 Keystone Flaps for Reconstruction in the Trunk
311
a
b
Fig. 25.10 (a) A 6 3 7 cm defect over the sacrum requires reconstruction.
There is no signi cant undermining evident, but exposed bone is present
as expected. The upper end of the natal cleft is just visible at 4 o’clock
in the drape window. (b) Upon islandization, it is obvious that there are
very few super cial veins in this region, with most of the drainage passing
deep. (c) An omega variant is produced by transposing both ends of the
ap to produce excellent padding over the sacral area and permitting V-Y
closure of the secondary defects without a ecting the natal cleft position.
c
islanding can be readily adapted to the needs of the defect and
the available tissues. Experience with keystone principles facili-
tates the development of expertise that permits such adaptation
to suit the speci c needs in each case.
The perineum is a specialized region with marked di erenc-
es in anatomy, pathology, and clinical presentations between the
sexes. Locoregional reconstruction of this area incorporates not
only the perineum but also the upper, inner thigh with keystone
ap reconstruction being very useful in this region. The pigmen-
tation of this area is similar to the perineum and therefore can be
used to good e ect for locoregional fasciocutaneous reconstruc-
tion. The use of locoregional tissue can, in som e cases, avoid the
use of more m orbid reconstructive options such as the use of ver-
tical rectus m usculocutaneous aps. Furtherm ore, these options
are not mutually exclusive. The use of musculocutaneous aps
for deeper reconstruction in conjunction with locoregional fas-
ciocutaneous aps such as the keystone ap for resurfacing can
maxim ize appearance, a trend becoming increasingly evident
throughout the body (Figs. 25.10 and 25.11).

Hints and Tips
The reliable nature of the perforators within the trunk region,
along with their venae comitantes, makes their elevation very
straightforward. In many cases, sharp dissection can be continued
down to the plane of ap elevation (e.g., down to the fascia) with-
out fear of a ecting the blood supply. Areas such as the lower ab-
domen are well known to have variable venous drainage (either
to the veins accompanying the deep inferior epigastric artery or
through the super cial inferior epigastric vein). For this reason,
it is still prudent to be respectful and protective of subcutaneous
neurovascular structures as these are lifelines in the setting of such
anatomical variation (Figs. 25.12, 25.13, 25.14, 25.15, and 25.16).

312
II Reconstructive Flaps A-to-Z
e
Fig. 25.11 (a) A 4 3 3 cm perineal defect that would result in signi -
cant distortion of the perineum if closed directly. (b) A keystone ap is
designed from the adjacent thigh crease to take advantage of the similar
skin color and quality and perforator supply from the external pudendal
artery. (c) The distal part of the ap is islandized to close the defect while
the proximal portion captures the perforators supplying the ap. (d) Ele-
vation of the inferior limb to demonstrate the plane of dissection and the
remaining ap attachment for perforator entry from the external puden-
dal artery. (e) The defect is closed by transposition of the inferior limb
with a concavity being produced that sits into the groin crease. The color
match is acceptable and the perineal structures are not signi cantly dis-
torted and should settle well over time.
a
b
c
d

25 Keystone Flaps for Reconstruction in the Trunk
313
a
b
c
Fig. 25.12 (a) Paramedian defect of the upper back too large for
primary closure. (b) The mark out for the keystone ap is oriented
vertically to run longitudinally with the paravertebral muscles and
their associated perforators. (c) Postoperative view showing early
healing and good contour.

314
II Reconstructive Flaps A-to-Z
Fig. 25.13 (a) A neurosurgical case requiring management and re-
construction in the lower left paramedian region with an obvious con-
tour deformity and poor skin quality over the lesion. (b) A signi cant
cavity is present following incision, with the deep structures clearly on
view. (c) In keeping with the principles of trunk closure, a large key-
stone ap is raised parallel to the paraspinal musculature, ipsilateral
to the defect. The ap has been mobilized extensively—particularly
near the primary defect to permit closure. Two triangles of excess ap
tissue at the margin of the primary defect will be excised prior to de-
fect closure. (d) Postoperative appearance showing early healing with
good contour. The mild concavity produced from direct advancement
matches the required contour of the lumbar region well. The two V-Y
advancement areas indicate signi cant recruitment from the adjacent
tissue and any contour irregularity produced in these areas will settle
well with time. (e) Longer postoperative view demonstrating reliable
healing and good contour, despite the initial size of the lesion.
e
d
a
b
c

25 Keystone Flaps for Reconstruction in the Trunk
315
d
c
e
a
b
Fig. 25.14 (a) A large pleomorphic sarcoma (malignant brous histio-
cytoma) is marked with a minimum of 1-cm margin along with minor
elliptical excisions. (b) To avoid mobilization involving the natal cleft,
bilateral keystone aps are designed, relying on segmental lumbar and
gluteal perforators. (c) Following excision of the lesion, a large defect over
the lumbosacral region is obvious. (d) This large defect is easily closed
by bilateral advancement of keystone aps with V-Y closures. This avoids
any signi cant changes to the natal cleft, recruits tissue from the abdom-
inal circumference, and minimizes scar extension into the upper back.
(e) Appearance at approximately 1 month following surgery, demon-
strating some widening of the scar in areas of tension centrally and at the
upper left V-Y point. The natal cleft is relatively normal and small areas of
dog ears at each V-Y point will settle with time. This is a much more robust
result than placement of a skin graft, has not involved any of the back
musculature, and is much simpler than free tissue reconstruction.

316
II Reconstructive Flaps A-to-Z
c
b
a
Fig. 25.15 (a) A large right-sided defect following resection of a sarcoma
over the right hip. (b) Gluteal artery perforators are captured by designing
a keystone posterior to the defect in a region of signi cant tissue availabil-
ity placing the ap over the buttock. This helps to hide the eventual scars
under clothing. (c) Final appearance following uncomplicated healing. The
slight attening in the region of the defect matches the natural atten-
ing posterior to the greater trochanter. A transposition or omega variant
would produce too much convexity here.
a
b
Fig. 25.16 Greater trochanteric pressure ulcer in a 24-year-old man with severe cerebral palsy who initially presented with a much larger defect. It was
managed by surgical debridement and negative pressure wound therapy until the cavity complexity and dead space decreased. The underlying bone
was exposed but no evidence of osteomyelitis was present. The wound geometry at subsequent excision and keystone reconstruction was simple and
easy to reconstruct. (a) Relatively small cutaneous defect with approximately 1–2 cm of undermining circumferentially with visible greater trochanter
in the depths. (b) Coating of the ulcer lumen with methylene blue minimizes the risk of incomplete excision of the sinus and therefore the risk of local
wound complications. (continued)

25 Keystone Flaps for Reconstruction in the Trunk
317
Khouri JS, Egeland BM, Daily SD, et al. The keystone island ap: use in
large defects of the trunk and extremities in soft-tissue reconstruc-
tion. Plast Reconstr Surg 2011;127:1212–1221
Taylor GI, Palmer JH. The vascular territories (angiosomes) of the body: experi-
mental study and clinical applications. Br J Plast Surg 1987;40:113–141
Figure Credits
1. THIEME Atlas of Anatomy, General Anatomy and Musculoskeletal
System, © Thieme 2005, Illustration by Karl Wesker.
2. THIEME Atlas of Anatomy, General Anatomy and Musculoskeletal
System, © Thieme 2005, Illustration by Markus Voll.
Suggested Further Reading
Behan FC, Findlay MW, Lo CH. The keystone perforator island ap con-
cept. Chatswood NSW: Elsevier Australia; 2012
Behan FC, Rozen WM, Azer S, et al. Perineal keystone design perfora-
tor island ap for perineal and vulval reconstruction. ANZ J Surg
2012;82:381–382
Behan FC, Sizeland A. Reiteration of core principles of the Keystone island
ap. ANZ J Surg 2006;76:1127–1129
Boucher F, Mojallal A. [Atlas of skin perforator arteries of trunk and lim bs
- guide in realization of perforator aps]. Ann Chir Plast Esthet
2013;58(6):644–649
Fig. 25.16 (continued) (c) Following excision, a 3 3 2 cm defect is present. Direct closure over the bony prominence would produce a signi cant risk of
wound dehiscence; therefore, ap closure was planned. (d) While it is tempting to design a small ap to reconstruct this small defect, the natural history
of pressure ulcers is that they are likely to recur if the etiological agents cannot be removed. In this case, the patient’s severe cerebral palsy was incurable
and therefore he was at signi cant risk of recurrence into the future. On this basis, a large ap was planned so that the same ap could be readvanced
in the setting of future recurrence. In this case a large keystone ap was designed and since the defect was over a convex surface, the straight limbs of
the incision were suitably curved and commenced close to each other near the opposite side of the defect. This omega variant will reconstitute some of
the convexity of the area of the defect, thereby improving aesthetics and providing a good thickness of tissue to pad the underlying bony prominence.
(e) Following islandization and mobilization, the perforator-based nature of the ap becomes evident with very few subcutaneous vessels in this region
to augment blood ow. The di erence between the thickness of the tissue at the excision site and surrounding tissues is evident and a conscious e ort is
made to maintain some thickness of the limbs that will close the defect. (f) Closure is simple over a suction drain and the transposed ends are trimmed
to ensure adequate thickness of tissue over the site of excision. Healing was uneventful and no recurrence occurred after 2 years of follow-up.
c
d
e
f

Keystone Flaps for Reconstruction
in the Upper Limb
Michael W. Findlay, Zeshaan N. Maan, and Gordon K. Lee
26
318

Introduction
Functional reconstruction is a major priority in upper limb recon-
struction. Function in the upper limb extends from the simplest ca-
pacity to position the hand in space through to the most delicate of
distal ne motor movements. All these movements rely upon sup-
ple tissues and the ability for unrestricted glide of the mechanical
components of the system (e.g., tendon glide and joint mobility).
Skin grafting, a relatively simple approach that sits lower
on the reconstructive ladder, can produce long-term sequelae in
highly m obile regions such as the upper limb and neck. Skin graft-
ing directly over tendons (even if covered by paratenon or follow-
ing imbrication) risks graft failure and tendon exposure, thereby
delaying healing and increasing the risk of reoperation and long-
term functional limitation. Progressive scar contracture can com -
plicate the use of skin grafts in the upper limb, especially where
split-thickness grafts are used in regions of frequent movem ent or
mechanical abrasion. The unstable scar produces progressive scar
contraction that can impair joint movement and adversely a ect
activities of daily living. By contrast, locoregional reconstruction
is typically well tolerated, produces little risk of contracture, and
replaces tissue like-for-like. Furthermore, the predisposition for
the upper limb to be involved in trauma (e.g., industrial accidents)
and therefore require vascularized reconstruction has prompted
the development of well-characterized aps with speci c pedi-
cles in this region. More than most areas of the body, in the upper
limb, the keystone technique provides a means to maximize the
potential to close defects without the need for practical knowl-
edge of these types of aps. However, careful planning is required
to ensure adequate soft tissue coverage, reliable healing, and min-
imal impact on the mobility of the surrounding joints. Even mild
limitations in joint movement can adversely a ect functional
capacity to perform activities of daily living, a relatively unique
characteristic of this region. The ability of keystone aps to pro-
vide reliable soft tissue for coverage of upper limb defects has
seen an increase in its use over the last decade for this purpose,
but surprisingly little has been published on its use in this region.
A number of parallels can be drawn between keystone re-
construction in the upper and lower lim bs. Both have a septocu-
taneous blood supply arranged in longitudinal fascial septae that
em erge between (or occasionally through) the longitudinally
oriented muscles of the limb. The result is that keystone recon-
struction in the upper limb is usually oriented with the long axis
of the ap running axially/longitudinally (the dermatomes can be
useful as an aide-memoire). Where defects lie in areas of natural
curvature, the typical keystone ap is modi ed by transposing
one or both ends to re-create this curvature. This is especially
useful over extensor surfaces of the joints (prepatellar region or
olecranon of the elbow), but these aps need to be planned care-
fully as mentioned above. As in the lower limb, perforator-based
reconstruction should remain ipsilateral to the subcutaneous
bony border of the forearm (e.g., the subcutaneous border of the
ulna). There are no perforators directly over the ulna (or tibia)
and the convexity of the lim b, combined with the sharp bony
edge, can limit blood ow to the tip of aps that are draped from
one side of the bone to the other.
Flap surgery under tourniquet control can facilitate “blood-
less” surgery, minimizing the risk to important neurovascular
structures. While the use of a tourniquet requires good intraop-
erative hemostasis to limit the risk of hematoma postoperatively,
it can be of additional use in noninvasively identifying the site of
the predominant perforator for the ap upon tourniquet release.
Finally, it is important to consider the functional consequences
of any potential postoperative immobility required to facilitate
uncomplicated wound healing and recovery (e.g., splintage and
elevation). Limiting surgery to one upper limb at a time is good
practice from this perspective, in contrast to the lower limb, where
bilateral surgery can limit the periods of immobility that postop-
erative restriction of limb dependency and movement may entail.
Adaptations for the upper limb include the ability to utilize
aps on an oblique angle relative to the longitudinal axis and
avoidance of aps that cross joint creases. Oblique aps are useful
in the upper limb because they utilize an oblique circum ference
of the limb (longer than a transverse circum ference) and can be
placed parallel to the relaxed skin tension lines to facilitate clo-
sure and aesthetics. The avoidance of placing aps entirely across
joints where possible can lim it the impact of ap reconstruc-
tion on joint mobility and the risk of joint contractures in the
long term (unless the aps are used for resurfacing previously
strictured joints). The perforator-based system for these aps
has been well described within the literature and aps can be
exceptionally reliable using standard keystone principles for ap
elevation. As with the lower limb, the upper limb is a common
site for surgeons to develop expertise in keystone and related ap
reconstruction. A working knowledge of the vascular anatomy is
highly useful in this process.

Vascular Pedicles and Blood
Supply in the Upper Limb
As found in the lower limb, there is a single predom inant vessel
supplying the arm with a profunda branch, signi cant collateral
and recurrent circulation around the elbow (consistent with

26 Keystone Flaps for Reconstruction in the Upper Limb
319
anterior and posterior borders. Figs. 26.1, 26.2, and 26.3 demon-
strate the relevant vascular anatomy of the deep vessels and the
most common overlying perforators.
Arm
As with other areas of the body, the blood supply to the skin of
the arm runs through numerous perforators dotted through-
out the region. The pattern of these perforators is nonrandom
with the major perforators aligned longitudinally within the lat-
eral and medial intermuscular septae. This arrangement naturally
suits a longitudinal orientation of keystone aps in this region so
that movement of the ap is predominantly at right angles to this
the geniculate anastomosis around the knee), and three vessels
w ithin the forearm (radial, ulnar, and interosseous) with only
two of these (radial and ulnar) providing the bulk of the blood
supply to the hand (sim ilar to the anterior and posterior tibial
vessels, although the peroneal provides additional supply to the
foot). All of these vessels reside deep to the deep fascia; therefore,
their branches and/or perforators from these must pierce the
deep fascia (or run in intermuscular septae) to reach the skin. In
the arm, there are two main fasciocutaneous septae—the lateral
and medial interm uscular septae—with the m ajority of perfora-
tors in the lower arm passing through these septae. However, the
pattern is less distinct than in the forearm or leg because muscles
like the deltoid are centralized over the lateral border of the arm
and therefore there are perforators through the muscle and at its
Thoraco-
acromial artery
Pectoral branches
Lateral thoracic
artery
Circumflex
scapular artery
Teres major
Thoracodorsal
artery
Superior ulnar
collateral artery
Inferior ulnar
collateral artery
Medial epicondyle
of humerus
Ulnar recurrent
artery
Common inter-
osseous artery
Ulnar artery
Anterior inter-
osseous artery
Posterior inter-
osseous artery
Radial artery
Radial recurrent
artery
Middle collateral
artery
Radial collateral
artery
Brachial artery
Deep artery of arm
Subscapular artery
Anterior circumflex
humeral artery
Posterior circumflex
humeral artery
Axillary artery
Deltoid branch
Acromial branch
Fig. 26.1 Main vessels of the arm including the relevant anastomoses around the shoulder and elbow.1

320
II Reconstructive Flaps A-to-Z
region consists almost entirely of a curved surface (e.g., convex over
the extensor surface and concave in the cubital fossa), increasing the
utility of keystone aps that incorporate transposition or rotation
within their mobilization. There are good and predictable perfora-
tors both medially (over Osborne’s ligament) and laterally (from the
middle collateral or recurrent collateral vessels) that are well suited
to the elevation and transposition of keystone and related aps.
Forearm
The perforating vessels supplying the skin of the forearm are some
of the earliest perforating vessels identi ed and purposefully
used as the basis for fasciocutaneous aps. The Chinese ap (ra-
dial forearm ap) is based on perforating vessels passing between
the exor carpi radialis and brachioradialis tendons within the
radial side of the forearm. The extensive use of this ap (antero-
grade and retrograde on the radial artery with associated veins)
and other perforator-based aps within the forearm including the
ulnar forearm ap and the posterior-interosseous aps, among
others, has resulted in intensive study of the cutaneous perforators
axis (transversely). However, there are also numerous muscular
perforators in the arm, permitting signi cant variation in the
orientation of the aps, depending upon the degree of movement
required. There is greater laxity of skin in the medial arm and this
is an obvious site for the positioning of the donor defect. Tissue can
be borrowed from the medial arm to assist closure of more lateral
defects and the close association between the medial arm skin and
the underlying neurovascular supply (deep to the deep fascia) en-
sures the reliability of using this tissue for perforator-based aps.
The medially placed scar also hides more successfully.
Elbow Region
The elbow region is well perfused by an anastomosis of collateral
vessels superiorly and recurrent vessels inferiorly, producing a rich
blood supply to the skin and subcutaneous tissues in this region. The
presence of the vascular anastomoses permits anterograde or ret-
rograde designs for aps. However, in general, the ap donor sites
should avoid traversing the midcubital line on the volar or dorsal sur-
faces so as to limit the impact on elbow joint movement. The elbow
Common inter-
osseous artery
Anterior inter-
osseous artery
Interosseous
membrane
Radial artery
Dorsal
carpal
artery
Dorsal carpal
network
Posterior
branch,
anterior
interosseous
artery
Posterior
interosseous
artery
b
Ulnar
artery
Perforating
branches
Radial
artery
Brachial artery
a
Fig. 26.2 (a) Volar aspect of the forearm illustrating the main vessels along with the common pattern of perforators demonstrating the
ease with which perforators can be captured during perforator-based reconstruction in this region. (b) The perforators from the interos-
seous system provide the remainder of blood supply to the forearm and are a reliable source of perfusion for keystone and related aps.1

26 Keystone Flaps for Reconstruction in the Upper Limb
321
Fig. 26.3 (a) Dorsal and (b) volar aspects of the hand demonstrating the extensive blood supply in the region along
with numerous super cial perforators.2 (continued)
Dorsal carpal
network
Extensor carpi
radialis brevis and
longus tendons
Radial artery
Abductor
pollicis longus
Extensor pollicis
brevis tendon
Extensor
indicis
Extensor pollicis
longus tendon
Dorsal
interossei
Dorsal
digital
arteries
Dorsal
metacarpal
arteries
Extensor
digitorum tendon
Radial artery, dorsal
carpal branch
Extensor digiti
minimi tendon
Ulnar artery, dorsal
carpal branch
Extensor
retinaculum
Extensor carpi
Ulnaris tendon
a
Palmar digital
arteries
Palmar
digital nerves
of thumb
Adductor pollicis
Flexor pollicis brevis,
superficial head
Abductor
pollicis brevis
Radial artery, superficial
palmar branch
Radial artery
Ulnar tunnel
Antebrachial
fascia
Palmaris longus
Ulnar artery and nerve
Flexor retinaculum
(transverse carpal ligament)
Palmaris brevis
Palmar aponeurosis
Abductor
digiti minimi
Flexor digiti
minimi brevis
Common palmar
digital arteries
Palmar
digital
nerves
b

322
II Reconstructive Flaps A-to-Z
signi cant skill and experience and are not an advisable area for
training in keystone aps as a novice to the technique.
As discussed in Chapter 23, the best way to design keystone
aps in the limbs is with the long axis parallel to the long axis of
the lim b. This approxim ates the derm atomes as seen in Fig. 25.4,
and these form a useful aide-memoire for keystone ap planning
in this region. This is further supported by the fact that the cu-
taneous vessels and the cutaneous nerves run axially within the
limb, often together due to their codevelopment.

Flap Design: Specif c
Regions in the Upper Limb
The Arm
It can be challenging to deliver both functional and aesthetic recon-
struction in fasciocutaneous reconstruction of the arm. While the
medial aspect usually has good skin quality, signi cant laxity, and
is very forgiving from the perspective of scarring, the same cannot
be said for the lateral border. The region over the deltoid muscle is
very prone to hypertrophic or keloid scarring, making the avoid-
ance of islandization in this region very useful. The whole lateral
border of the arm is convex and contour irregularities and scars
can be obvious with certain types of clothing, especially in wom-
en. In general, the priority is contour over scar length. From this
perspective, keystone aps that incorporate transposition or omega
variants help to re-create the convexity of fasciocutaneous defects.
Where possible, medialization of the scar is preferable (i.e., if clo-
sure is too tight to provide suitable convexity, a releasing incision
on the inner aspect of the arm with inset of a full-thickness skin
graft can often avoid additional scar and contour deformity on the
lateral border). As in other areas of the body, small dog ears readily
settle with time and any residual tissue can easily be excised under
local anesthetic. The same correction cannot be made for concave
defects that arise following defect reconstruction. Where the plan-
ning of aps must extend near, or across, the joint line of the elbow,
placement of the tip of the ap laterally or medially is ideal so that
the scar lines do not have a net exor or extensor e ect. Fig. 26.4
demonstrates this approach, where we have placed a defect close
to the joint purposefully to show the di culties in getting good
in this region. Each of these aps demonstrates the reliability of
perforator-based ap elevation and reconstruction within the
forearm. Keystone perforator aps have an additional bene t over
these aps in that they do not sacri ce the parent vessel for the
reconstruction (e.g., radial artery and venae comitantes), ensuring
the viability of the hand in the setting of incomplete palmar arches
and the availability of these vessels for bypass grafting (e.g., coro-
nary artery bypass grafting). The perforators are typically arranged
in longitudinal rows, allowing them to pass between (or through)
the muscle bellies proximally or between the tendons distally. The
perforators in these rows are typically from the same parent vessel.
This arrangement simpli es ap planning as a ap (or aps) can
be designed lateral (and/or medial) to the defect. If the ap width
(between the curvilinear lines) is equal to or greater than the defect
diameter, there will not only be su cient tissue to ensure defect
closure in most cases, but the keystone ap will overlie cutaneous
perforators from the next adjacent vascular territory, thereby cap-
turing perforators from an uninjured/uninvolved parent vessel.
Hand
The hand is readily divided into dorsal and volar surfaces. The
dorsal surface is well-suited to longitudinally oriented keystone
aps due to the profuse nature of the underlying cutaneous per-
forators (interosseous vessels) em erging typically from the radial/
deep palmar arch or directly from the radial artery itself near the
anatomical snu box. The thin and mobile nature of the dorsal
skin perm its signi cant m ovement of aps raised in this region
and despite the often small size of the cutaneous vessels present,
aps are typically robust and reliable, especially when inset under
even physiological tension. On the volar aspect, the predominant
cutaneous supply to the palm is via vessels from the super cial
palm ar arch or as part of the intercomm unications between the
two palmar arches. As in the head and neck, the palm ar creases
may require the keystone shape to be varied, but the same longi-
tudinal orientation, sharp cutaneous incision, followed by blunt
subcutaneous dissection is helpful to preserve the cutaneous
vessels. In addition, there are often strong palmar septae anchor-
ing the tissue of the palm that m ay need to be divided sharply
in a manner analogous to the selective ligam entous release (SLR)
technique used in the facial region. As such, palm ar aps require
Fig. 26.4 (a) A lesion just above the elbow has been created to examine the principles of reconstruction in this region without adversely impacting
elbow joint mobility. (b) An asymmetrical keystone ap is designed to run with its long axis parallel to the underlying musculature and their associated
intermuscular septae. Here the lateral intermuscular septum runs underneath this ap. Note that the keystone ap design has its inferior V-Y point
lateral to the joint and stops before it crosses the joint line. This minimizes the impact on elbow movement. (continued)
a
b

26 Keystone Flaps for Reconstruction in the Upper Limb
323
Fig. 26.4 (continued) (c) Following the creation of the primary defect, it is
evident that there is signi cant convexity in this area as evidenced by the
layer of subcutaneous adipose tissue. This convexity requires restoration
by ap reconstruction; therefore, direct advancement is to be avoided in
preference for keystone variants that involve transposition. (d) The lateral
intermuscular septum is identi ed and preserved within the ap. (e) Both
ends of the keystone ap are elevated in preparation for an omega variant
closure of the defect. (f) The ap is approximated to itself to form the
new shape of the area. (g) Following closure, there is an obvious convexity
above the elbow and a tightness at the elbow level. Despite this, these will
settle and stretch respectively over time with elbow movement and under
the e ects of gravity and skin elasticity. (h,i) These demonstrate the nor-
mal range of motion achieved with this periarticular reconstruction by the
use of the above principles.
c
d
e
f
g
h
i
convexity with minimal impact on joint mobility without some ir-
regularities. Luckily, most regions of overconvexity settle well with
time and good preoperative counseling of the patient is essential.
Elbow and Forearm
There are a number of well-described pedicled fasciocutaneous
aps within the forearm and therefore, they ought to be the standard
against which any other ap is compared. The classic example is
the radial forearm ap: a thin, pliable ap with a long, reliable ped-
icle that can cover defects from above the olecranon (antegrade)
to the thumb tip (retrograde). There are two major drawbacks to
this ap. First, it removes an important vessel to the hand (radial
artery), and second, it produces a very poor donor site defect when
the donor defect cannot be closed directly. As a perforator-based
ap, the keystone ap does not sacri ce a major vessel to the hand

324
II Reconstructive Flaps A-to-Z
to reconstruct the donor defect caused by raising the radial fore-
arm ap, minimizing the impact on the aesthetics of the forearm
(Fig. 26.6). The keystone ap provides good contour in this region
and heals well, and the curved nature of the ap and the forearm
minimize the visibility of the ap.
and its use of tissue adjacent to the defect improves the aesthetic
outcome of defect reconstruction. The keystone ap is very easy to
perform in the forearm as long as the axis of the ap is kept parallel
to the long axis of the limb, with oblique placement maximizing
use of the relaxed skin tension lines (Fig. 26.5). It can even be used
Fig. 26.5 (a) A simple elliptical excision is planned on the dorsal surface
of the forearm. (b) Following excision, the defect cannot be closed di-
rectly. Therefore, a keystone ap is designed along the same axis as the
ellipse to facilitate closure. (c) Following cutaneous islandization, blunt
dissection is undertaken to maintain the subcutaneous neurovascular
structures (particularly the veins and super cial nerves). (d) Appearance
of the ap following circumferential mobilization with maintenance of soft
tissue glide planes if possible to facilitate normal aesthetics with forearm
movement following wound healing. (e) Early three-point suturing starts
to encourage creep, thereby facilitating wound closure. (f) The areas of
redundant ap can now easily be marked and resected. (g) Final closure is
easily achieved, with an acceptable contour.
a
c
e
g
b
d
f

26 Keystone Flaps for Reconstruction in the Upper Limb
325
Fig. 26.6 Keystone perforator island ap reconstruction of radial fore-
arm ap defects. (a,b) A radial forearm free ap (RFFF) is designed over
the radiovolar aspect of the forearm with a keystone ap based on the
interosseous system of perforators beside it. (c) Following RFFF harvest,
the keystone ap is islandized and tension sutures are placed across the
primary defect to encourage creep. (d) The secondary defect is now
open over a broad front to permit such closure. Fascial release was neces-
sary near the ulnar border to facilitate suitable tension across the repair.
(e,f) Upon nal closure, the contour of the forearm is very acceptable and
V-Y advancement has been achieved both proximally over the extensor
wad and distally over the ulnar head. (g) Final appearance showing good
contour and mild depigmentation associated with stretching of this elderly
patient’s skin. Healing was prompt with no postoperative complications.
The patient had mild wrist sti ness at 2 weeks in keeping with the normal
progress following RFFF harvest, but had full and normal upper limb func-
tion by 6 weeks.
a
c
e
g
b
d
f

326
II Reconstructive Flaps A-to-Z
and subcutaneous tissues may be thin and under some tension
follow ing defect closure, especially with certain hand positions
(Fig. 26.7).
Splinting the hand and wrist for this period assists in wound
healing until wound tensile strength and stretch of the surround-
ing tissues has occurred su ciently to minimize the risk of wound
dehiscence. In areas of thin skin (e.g., the dorsum of the hand), it
may not be possible to insert any deep sutures due to insu cient
dermis and subcutaneous tissue. Therefore, a simple skin suture
using a slightly larger suture diam eter than would otherw ise be
used (e.g., 3-0 or 4-0) is advisable. Where it is uncertain how long
healing will take to occur (e.g., immunosuppressed individuals
Hand
The technique of keystone elevation in the upper lim b is very
similar to that described in Chapter 23. A few points warrant em -
phasis to describe important distinctions with upper limb ap
surgery. The range of functions performed by the upper limb is
signi cantly greater than that in the lower limb and therefore it
is essential to ensure that joint mobility is m inim ally a ected. By
the sam e token, the application of a postoperative splint for short-
term immobilization (up to 1 week) is usually well-tolerated by
the patient without signi cant long-term adverse outcomes. This
is especially useful for aps used around the hand, where the skin
Fig. 26.7 (a) A lesion is marked for excision via a longitudinally oriented ellipse on the dorsum of the hand. Such a presentation is common in the elderly with
signi cant sun exposure to the dorsum of the hands. (b) Prior to excision, a longitudinally oriented keystone ap is designed in case the ellipse cannot be
closed directly. The longitudinal orientation ensures capture of the longitudinally oriented cutaneous perforators in this region. (c) Following excision, the long
extensor tendons of the upper limb are clearly visible covered in paratenon. Skin grafting is possible, but any failure of graft take can result in tendon exposure.
(d) The defect cannot be closed directly. (e) Strategic mattress sutures are placed to promote creep and facilitate even tension across the whole ap. The
redundant ap tissue is marked prior to excision. (f) Final inset demonstrating the ease of closure in this region. The remaining skin will stretch signi cantly
over the next 1 to 2 weeks with a return to near normal hand function by 3 to 4 weeks in the vast majority of cases.
a
c
e
b
d
f