15018752330
发表时间:2015-12-08 浏览次数:547次
John et al.[1]
describe five cases in which a keystone flap was performed for
reconstruction of lower extremity defects. In an attempt to address the
difficulty of reconstruction of these defects, that is, limited skin
laxity, thick deep fascia, and limited availability of perforating
vessels, the authors propose identifying the perforating vessels to
facilitate flap movement. Vessel locations were detected preoperatively
with a Doppler probe. Subfascial dissection of the flap was performed in
order to identify the perforators. However, further skeletonization of
the vessels was not performed. Of the five cases in this series, two are
detailed in the article and describe elliptical defects of 20 cm × 9 cm
and 16 cm × 7 cm. Only limited defects that required a local flap
advancement of up to three centimeters were included, as the authors
contend that this is the maximal possible advancement of the flap
without skeletonization.
Behan was the first to describe the keystone flap concept in 2003. [2]
He described four subtypes of flaps: (1) type one - the classical flap
in which very little elevation from the flap bed is performed; (2) type
two - allows additional flap advancement by performing a dissection of
the lateral deep fascia margin; (3) type three - the use of two keystone
flaps in order to repair larger defects; and (4) type four - where
subfascial undermining of up to 50% of the flap is required to allow
flap movement. All four types of fasciocutaneous flaps do not require
identification of the perforators prior to elevation of the flap.
Emphasis is made on performing a blunt dissection in order to preserve
as many vessels as possible. In this paper, keystone flaps were used to
reconstruct trunk and limb defects.
Reconstruction of lower limb defects with the keystone design island flap was subsequently reported by several authors. Khouri et al.[3]
reported a case series of 28 large defects of the trunk and
extremities. Lack of local tissue laxity was significant enough to make
the patients candidates for microvascular reconstruction. Preoperative
identification of the perforators by a Doppler probe was performed in
the smaller reconstructions. According to the authors, this was deemed
unnecessary in larger defects because of the frequency of such vessels
throughout the body and the assumption that adequate perforators would
be present in a larger flap design. During the procedure, care was taken
to ensure the incision was carried down to muscular or deep fascia in
order to enhance mobility. A deeper incision was not necessary. Although
the series had high-complication rate when all minor wound healing
issues were considered, the success rate was reported to be 97%, with
only one patient requiring reconstruction by an alternate method. [3]
Additional reports of the use of the keystone flap for lower limb
reconstruction demonstrate that this flap can be closed under relative
tension, [4],[5]
since muscular perforator arteries, which exit the surface of the
muscle to enter the subcutaneous tissue from directly beneath the flap,
there is minimal risk of ischemic necrosis.
Moncrieff et al.[6]
published the largest series of flap reconstructions for melanoma of
the leg, describing the keystone flap as "the end of the skin graft."
The study included 176 patients with primary melanomas of the lower
limb. In some of the cases in this series, a modified technique was
used, in which dermis was incised full thickness, but not deeper, on the
lateral border, and the subcutis was released with gentle blunt
spreading dissection. The average diameter of the excised specimen was
2.6 cm. The reconstruction comprised 106 standard, 65 modified, and 5
double-opposing type keystone flaps performed from the proximal leg to
the dorsum of the foot. The modified technique of the keystone flap,
with decreased tissue dissection, was associated with a significant
decrease in major complication rate. [6]
Minimizing tissue dissection helps to minimize complications in this
type of procedure. For larger defects, more extensive dissection may be
warranted to facilitate tissue movement, as described by Behan as
keystone flaps type 3 or 4. Preoperative identification of the
perforating vessels may contribute to a more accurate flap design.
However it has not been demonstrated that it is essential in order to
perform a deeper dissection. The selection of limited defects in this
work does not allow the authors to conclude that identification of
perforator vessels allows better mobilization of the flap. However, we
feel that it does facilitate safe elevation of a flap with the knowledge
that a perforator is present within the flap design. Having said that,
by dissecting out one or two main perforators, many other smaller
vessels are transected. While it is likely that the majority of the flap
will survive, there is a potential for marginal necrosis from ischemic
or congestive insults, as a result, of this "over-dissection". As this
plagues other types of flaps (such as propeller flaps and free flaps), a
case by case assessment should be made, as always.
A minor point
to consider is the length of operative time required for the keystone
flap procedure. The OR time in keystone flaps, as described in the
literature, was less than two hours. [3],[7]
This length of time is significantly shorter than most microsurgical
procedures, and it is one of the advantages of the keystone-design flap
technique. Although not stated, it follows that the identification and
skeletonization of perforators would prolong OR time (as well as
increase the rate of complications).
In conclusion, the keystone
island flap is a useful technique to close both small and large defects
of the lower extremities. The advantage of preoperative identification
of perforators may allow further flexibility in the utilization of the
flap. We encourage the authors to continue to share their experience
with this technique, in order to substantiate its role in lower limb
defect reconstruction, and expand the variety of defects it can be
implemented for.
References
1.John JR, Balan JR, Tripathy S, Sharma RK, Jadhav C. The keystone-design perforator-based flap for leg defects: a synthesis of philosophies. Plast Aesthet Res 2014;2:70-2.
2.Behan FC. The keystone design perforator island flap in reconstructive surgery. ANZ J Surg 2003;73:112-20.
3.Khouri JS, Egeland BM, Daily SD, Harake MS, Kwon S, Neligan PC, Kuzon WM Jr. The keystone island flap: use in large defects of the trunk and extremities in soft-tissue reconstruction. Plast Reconstr Surg 2011;127:1212-21.
4.Martinez JC, Cook JL, Otley C. The keystone fasciocutaneous flap in the reconstruction of lower extremity wounds. Dermatol Surg 2012;38:484-9.
5.Hu M, Bordeaux JS. The keystone flap for lower extremity defects. Dermatol Surg 2012;38:490-3.
6.Moncrieff MD, Bowen F, Thompson JF, Saw RP, Shannon KF, Spillane AJ, Quinn MJ, Stretch JR. Keystone flap reconstruction of primary melanoma excision defects of the leg-the end of the skin graft? Ann Surg Oncol 2008;15:2867-73.
7.Chaput B, Herlin C, Espié A, Meresse T, Grolleau JL, Garrido I. The keystone flap alternative in posttraumatic lower-extremity reconstruction. J Plast Reconstr Aesthet Surg 2014;67:130-2.