HOW WE DO IT

The Keystone Fasciocutaneous Flap in the Reconstruction ofLower Extremity Wounds

JUAN-CARLOS MARTINEZ, MD,* JONATHAN L. COOK, MD,† AND CLARK OTLEY, MD‡

The authors have indicated no significant interest with commercial supporters.

Although primary linear closure is the most

common form of surgical wound closure, it is

not always feasible. Some wounds require local

flap closure, skin grafting, or even free flap cover-

age. Because there is a paucity of lax tissue avail-

able for adjacent tissue transfer on the leg, larger

defects in this area have historically been repaired

with full- or split-thickness skin grafts. Lower

extremity wounds tend to heal more slowly than

wounds in other locations. Given the relatively

higher metabolic demands of full-thickness skin

grafts, split-thickness grafts have often been used

as the reconstructive modality of choice for cutane-

ous defects on the distal lower extremities that can-

not be closed primarily. These grafts have their

own disadvantages, including donor site morbidity

and the common atrophic, depressed, and hypopig-

mented appearance of the graft at the recipient site

as it matures. There are also significant risks of

graft failure when they are applied to lower

extremity wounds.

The keystone fasciocutaneous flap circumvents the

challenges of wound closure in many areas of

decreased tissue laxity. In addition, keystone flaps

depend not on the anastomotic dermal plexus but

on underlying muscular perforators for perfusion.

These perforator vessels traverse the superficial

muscular fascia and feed directly into the overlying

subcutis and dermis, providing a surprisingly

robust vascular supply.1 Described and defined ini-

tially by Felix Behan in the late 1990s as a true fas-

ciocutaneous flap (as opposed to a random-pattern

island pedicle flap), the keystone flap has been rec-

ognized as an important innovation in the recon-

structive armamentarium. It has even been touted

as the “end of the skin graft” for reconstruction

of wounds after melanoma excisions on the lower

extremities.2 Well described in the plastic and

reconstructive surgical literature, the keystone

flap has useful applications in dermatologic

surgery.1,3–5 This brief manuscript is intended to

introduce the keystone fasciocutaneous flap to the

dermatologic surgical literature.

Execution

Execution of the keystone fasciocutaneous flap is

detailed in Figures 1 through 6.

Figure 1. A keystone flap has been designed for

closure of a wound measuring 2.5 cm in width

located on the left calf of an active young man.

Wound closure tension was such that primary clo-

sure was deemed likely to fail. The location of the

flap with respect to the defect depends on local tis-

sue laxity and angiotomal distribution.6,7 In this

case, the flap originated from the medial aspect of

*Department of Dermatology, Mayo Clinic, Jacksonville, Florida; †Department of Dermatology, Duke UniversityMedical Center, Durham, North Carolina; ‡Department of Dermatology, Mayo Clinic, Rochester, Minnesota

© 2011 by the American Society for Dermatologic Surgery, Inc. � Published by Wiley Periodicals, Inc. �ISSN: 1076-0512 � Dermatol Surg 2012;38:484–489 � DOI: 10.1111/j.1524-4725.2011.02239.x

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the leg. Lines equal in length to the width of the

proposed defect were designed perpendicularly

from each apex of the ellipse. A sweeping convex

arc connected these two lines, parallel to and equi-

distant from the originally drawn ellipse, creating

the flap’s keystone shape. The width of the flap

was constant and was equal to the maximal width

of the proposed defect, denoted here as X.

Figure 1.

Figure 2.

Figure 3.

Figure 4.

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38 :3 :MARCH 2012 485

Figure 2. This surgical defect extended to the depth

of the superficial muscular fascia after the excision

of a Breslow 0.7 mm melanoma. Note the slight

increase in apparent width of the defect and appar-

ent narrowing of the flap once the elliptical speci-

men had been excised. The entire ellipse was

prospectively removed, as this allowed the flap to

move into place much more freely, especially given

the high tension under which the first key sutures

were placed.

Figure 3. The entire flap was incised superficially

into the subcutaneous fat. Although dermal vessels

were necessarily transected with incision of the

flap, great care was taken not to disturb any

peripheral subcutaneous vascular bundles during

this initial step of flap creation.

Figure 4. Predominantly blunt and occasionally

sharp dissection were used to loosen all fibrous

septal attachments that may have existed between

the subcutis of the flap and the surrounding periph-

eral tissue. This careful dissection was performed

along the entire perimeter of the flap and allowed

for visualization and sparing of intact vascular

attachments to the peripheral subcutis. Note the

wider “gap” between the flap and the periphery

than in Figure 3. Original reports of the flap’s

design suggested that only minimal undermining

beneath the flap should be performed. The flap’s

original descriptor has since modified his stance

and reported flap success with up to two-thirds of

the width of the flap undermined.6 In the flap

shown here, no undermining of the flap or periph-

eral tissues was performed. At the stage shown

here, one should be able to gently divide the flap

from the periphery down to the underlying fascia,

with only intact peripheral vascular bundles bridg-

ing the gap between the flap and the surrounding

skin.

Figure 5. Key stitches A-C were then placed

sequentially, aligning the flap. Because no under-

mining was performed, wound closure tensions

were predictably high. Pulley stitches can be useful

in overcoming these relatively high wound closure

Figure 5.

Figure 6.

KEYSTONE FASCIOCUTANEOUS FLAP

DERMATOLOGIC SURGERY486

tensions without tearing thin, friable tissue. Pro-

spective removal of anticipated Burow’s triangles,

as planned in Figure 1 and executed in Figure 2,

allowed the entire flap to move into place unob-

structed by standing cone deformities, despite high

tensions. Note the elongated secondary defect cre-

ated around the periphery of the flap. In contrast

to random pattern flaps based on the dermal

Figure 7.

Figure 8.

Figure 9.

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38 :3 :MARCH 2012 487

plexus vasculature, the keystone flap has significant

lateral tension upon its insertion, noted here by tis-

sue puckering, that does not impair the flow of the

muscle perforators that perfuse the flap from

underneath.

Figure 6. Once key sutures were placed, the cor-

ners from which the convex arc was released were

closed in a V-Y fashion using superficially placed

buried vertical mattress sutures. These V-Y

advancements push tissue laxity centrally, reducing

some of the tension on the key sutures. Once these

corners have been approximated, the tissue redun-

dancies from the concave arc of the flap can be

draped over the defect edge and appropriately

trimmed. Buried vertical mattress sutures, placed

superficially to avoid disrupting any of the remain-

ing vascular bridges, were placed around the

periphery of the flap. The epidermal edges were

then carefully approximated.

How Does the Keystone Flap Work?

The initial key sutures seem to break all the rules

regarding the avoidance of placing excessive ten-

sion on the flap. Tissue placed under such high ten-

sion might seem prone to developing ischemic

necrosis, but muscular perforator arteries, which

exit the surface of the muscle, pierce the overlying

fascia, and enter the subcutis from directly beneath

the flap, provide the keystone fasciocutaneous

flap’s vascular supply. Lateral tension placed on

the tissue is perpendicular to the vascular flow and,

as such, does not typically impair it to any signifi-

cant degree. With experience and flap successes,

the surgeon is able to appreciate the predictable

perfusion provided by these small but highly

effective muscular perforators.

The movement of the flap is described in depth in

the original manuscript and in a related commen-

tary.3,8 The flap can be considered to be a modified

bipedicled advancement flap with no peripheral

attachments. The flap’s primary movement is essen-

tially purely advancement, with the primary defect

closed under high tension as noted above and

followed by closure of a larger peripheral second-

ary defect. As in a bipedicled advancement flap,

the type of flap motion in the keystone flap allows

for the sharing of wound closure tensions between

two parallel linear closures and the intervening

bridge of tissue (the flap). In distinction from a bi-

pedicled flap, all edges surrounding the keystone

flap are freed, and the superior and inferior edges

must therefore also be closed. The additional clo-

sure of these edges decreases the tension along the

primary vector of advancement.

Alternatively, the keystone flap can be viewed as

two opposing but conjoined V-Y advancement

flaps. The flaps essentially advance into each other,

and the tissue laxity gained from the opposing V-Y

flaps is then available laterally.

Conclusion

The keystone fasciocutaneous flap is a reconstruc-

tive option that is useful to any surgeon who

repairs large surgical defects, particularly ones on

the distal lower extremities. It is a robustly per-

fused flap that can provide volume restoration and

consistently good cosmetic outcomes where skin

grafts simply cannot. Figures 7 to 9 illustrate

surgical defects, keystone flap inset, and long-term

successes in a variety of clinical scenarios. This

flap has a proven track record in other surgical

subspecialties and should perform similarly

well in the hands of suitable dermatologic

surgeons.

References

1. Pelissier P, Santoul M, Pinsolle V, Casoli V, Behan F. The

keystone design perforator island flap. Part I: anatomic study.

J Plast Reconstr Aesthet Surg 2007;60:883–7.

2. Moncrieff M, Bowen F, Thompson JF, Saw RP, et al. Keystone

flap reconstruction of primary melanoma excision defects of the

leg-the end of the skin graft? Ann Surg Oncol 2008;15:2867–73.

3. Behan F. The Keystone Design Perforator Island Flap in

reconstructive surgery. ANZ J Surg 2003;73:112–20.

KEYSTONE FASCIOCUTANEOUS FLAP

DERMATOLOGIC SURGERY488

4. Behan F, Sizeland A. Reiteration of core principles of the

Keystone island flap. ANZ J Surg 2006;76:1127–9.

5. Pelissier P, Gardet H, Pinsolle V, Santoul M, Behan FC. The

keystone design perforator island flap. Part II: clinical

applications. J Plast Reconstr Aesthet Surg 2007;60:888–91.

6. Behan F, Lo C. Principles and misconceptions regarding the

keystone island flap. Ann Surg Oncol 2009;16:1722–3.

7. Behan F, Lo C, Shavan R. Perforator territory of the keystone

flap—use of the dermatomal roadmap. J Plast Reconstr Aesthet

Surg 2009;62:551–3.

8. Jackson I. The keystone design perforator island flap in

reconstructive surgery. ANZ J Surg 2003;76:261.

Address correspondence and reprint requests to: Juan-Carlos Martinez, MD, Department of Dermatology,Mayo Clinic, 4500 San Pablo Pkwy, Jacksonville, FL,32224 or e-mail: martinez.juancarlos@mayo.edu

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