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of osteomyelitis. Quant Imaging Med Surg. 2016;6(2):184-198.
Med. 1969;134(1):19-24.
Effects of lidocaine and epinephrine on cutaneous blood flow. J
Plast Reconstr Aesthet Surg. 2008;61(10):1226-1231.
outcomes of sheet grafting with 1:1 mesh grafting in patients with
thermal burns: a randomized trial. Burns. 2015;41(2):257-264.
pressure closure in the integration of split thickness skin grafts: a
randomized, double-masked, controlled trial. Ann Surg.
2006;244(5):700-705.
blinded, randomized, controlled clinical trial of topical negative
pressure use in skin grafting. Plast Reconstr Surg. 2004;114(4):917-
922.
management of split-thickness skin graft donor sites: a systematic
review. Int J Nurs Pract. 2003;9(2):S9-S17.
thickness skin graft donor site dressings. Int Wound J.
2018;15(6):1000-1009.
indications and common practices. Burns. 2017;43(8):1775-1781.
history, indications, technique, physiology and experience: a
review article. J Wound Care. 2018;27(suppl 2):S12-S18.
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modified Meek technique with standard mesh method in patients
with third degree burns. World J Plast Surg. 2020;9(3):267-273.
coverage. Plast Reconstr Surg. 2007;120(1):166-172.
The dermis graft: another autologous option for acute burn wound
coverage. Burns. 2012;38(2):274-282.
split thickness skin graft donor site assists healing. Plast Reconstr
Surg Glob Open. 2017;5:e1339.
function of re-harvested skin from non-scalp donor sites. J Invest
Surg. 2023;36(1):1-7.
modifications to the traditional model. Plast Reconstr Surg.
2011;127(suppl 1):205S-212S.
thickness pediatric facial burns. J Burn Care Res. 2019;40(2):251-
254.
Dziewulski P. The use of dermal regeneration templates for
primary burns surgery in a UK regional burns centre. Ann Burn
Fire Disasters. 2020;33(3):245-252.
and effectiveness of the RECELL® system combined with splitthickness meshed autografts for the reduction of donor skin to
treat mixed-depth burn injuries. Burns. 2019;45(4):772-782.
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CHAPTER 7 Principles of Flap
Reconstruction: Muscle Flaps,
Myocutaneous Flaps, and
Fasciocutaneous Flaps
Catherine L. Ly and Henry C. Hsia
KEY POINTS
An understanding of the core principles of flap
reconstruction is an essential skill in reconstructive surgery.
A flap is a unit of tissue with a defined blood supply that is
transferred from one part of the body to another.
It is critical to balance the reconstructive needs with
potential donor site morbidity, the patient’s medical status,
and the patient’s desires when considering flap selection.
The size, shape, and components of a flap can be
manipulated nearly to an infinite level if vascular anatomy
and surgical dissection techniques are well understood.
INTRODUCTION
Flaps are a key component of reconstructive surgery. A flap is a unit of
tissue with a defined blood supply that is transferred from one part of
the body to another. Each flap has several distinct characteristics: (1)
its component parts (eg, skin, fascia, muscle, bone, visceral, or a
combination), (2) the nature of its blood supply (random or axial), and
(3) the type of the transfer (pedicled, in which the blood supply is not
detached, or free, in which the blood supply is disconnected and
anastomosed to the blood supply at the recipient site). In the case of
pedicled flaps, flaps can be further defined by their distance from the
defect (local, regional, or distant) and the movement required for the
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flap to reconstruct the defect (eg, advancement, pivot, transposition, or
interpolation). Flap surgery requires a keen understanding of not only
anatomy but also form and function.
The evolution of flap surgery is linked to increasing knowledge of the
blood supply of the body and advancements in vessel dissection
techniques to permit the transfer of viable tissue. In 1973, McGregor
and Morgan defined random pattern flaps as those based on unnamed
small vessels.1 These flaps are suitable for smaller defects and depend
on the ratio of flap length to width. In contrast, axial pattern flaps are
based on known, anatomically defined vasculature oriented
longitudinally within the flap. Because of their greater reliability, these
flaps are preferred for moderate to large defects. The concept of
angiosomes was developed by Taylor and Palmer in 1987.2 Using ink
injection studies, cadaveric dissection, and radiographic analysis, they
defined angiosomes as composite vascular units supplied by source
vessels and identified more than 350 major perforators. This provided a
reliable guide for flap design. An ideal flap can provide wound coverage
and optimize patient function with minimal donor site morbidity.
PREOPERATIVE ASSESSMENT
As with any surgical patient, patients undergoing reconstructive surgery
must be optimized. This includes managing any comorbidities, ensuring
proper nutrition, and preparing the wound bed, potentially through
multiple debridement procedures. However, the timing of reconstruction
is dependent on not only patient condition and wound readiness but
also the need for expeditious coverage of exposed vital structures. In
cases where timing may be flexible, adjunctive procedures such as
negative-pressure wound therapy, tissue expansion, and flap
prefabrication may be performed to facilitate the reconstruction.
It is necessary to consider the reconstructive ladder when deciding
the appropriate reconstructive method. A flap may result in
unnecessary morbidity if healing by secondary intention, primary
closure, skin grafting, or other techniques is possible. When presented
with a defect that would benefit from flap reconstruction, it is necessary
to evaluate for several key aspects to help guide flap selection. The
first step is to define the size and nature of the defect, with a clear
understanding of what is missing, as the ideal goal is to “replace like
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with like.” Subsequently, one must assess the damage to regional
tissues (such as that from radiation or prior surgery) and the presence
of exposed large vessels, joints, or other vital structures. If there is
significant dead space, a flap with adequate bulk is necessary. If skin
and soft tissue are missing, one must compare the risks and benefits of
a skin graft over a vascularized flap with that of a flap that includes skin
and soft tissue. If a free flap is being considered, the recipient blood
vessels must be evaluated for size, orientation, flow, and terminal blood
supply. This may be performed using Doppler ultrasonography or with
other imaging techniques such as computed tomography or magnetic
resonance angiography.
Donor site morbidity is an important consideration. The risks and
benefits of “robbing Peter to pay Paul” must consider the reconstructive
needs, the consequences of the secondary defect, and the patient’s
medical status and desires. An athlete who would like to continue
running, for example, may want to avoid a muscle flap from the lower
extremity. Meanwhile, it is generally accepted that flaps that
compromise upper extremity and trunk strength should be avoided in
paraplegic patients, as they require these muscles for mobilization. In
addition, it is critical to remember that harvesting of a flap as a donor,
particularly from a distant site, requires performing surgery on a site
that did not require it and that doing so may result in unnecessary
scarring and change in sensation, among other potential adverse
effects.
DELAY PHENOMENON
The delay phenomenon is an important concept to understand in flap
reconstruction. Also known as vascular delay or ischemic
preconditioning, it is based on findings that interruption of a portion of
the normal blood supply of the flap without transfer causes a sublethal
ischemia that results in the opening of “choke” vessels, longitudinal
reorientation and dilatation of vessels within the flap, and the growth of
new vessels through angiogenesis.
3,4
The consequent improvement in
vascular supply can be used to improve flap survival, extend the size of
random pattern cutaneous flaps, or transfer greater volumes of axial
pattern flaps. It can be particularly useful in patients with impaired
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microcirculation, such as those with a history of active smoking,
diabetes mellitus, obesity, or radiation.
Flap delay is most often accomplished by incising along the
perimeter of the planned flap, partial undermining of the flap, or
definitive ligation of source vessels with maintenance of the flap in its
native location in one procedure, followed by ultimate flap harvest in a
second procedure. The second procedure is often performed around
2 weeks after the first, after maximal augmentation of the blood supply.
Other nonsurgical techniques such as embolization or chemical delay
with administration of human vascular endothelial growth factor have
been described but are much less common.
MUSCLE FLAPS
Muscle flaps are workhorse flaps with reliable vascular supply from
named vessels that are effective in filling dead space, particularly in
areas that are at high risk for infection. Any muscle can potentially be
used as a flap, either in part or whole. The key to muscle flap use is the
understanding of its vascular anatomy in the context of the muscle
origin and insertion. There are few absolute contraindications to the
use of muscle flaps, but the use of donor muscles that would result in
significant disability or have a high risk of failure because of prior
damage from radiation or a compromised vascular supply should be
avoided.
Classification System
Using anatomical studies, Mathes and Nahai developed the most
widely used classification system of muscle flaps based on five
patterns of circulation (Table 7.1).5 Type I muscles, which include the
gastrocnemius, rectus femoris, and tensor fascia lata, have a single
dominant vascular pedicle. Type II muscles are the most common and
have one or more dominant vascular pedicles close to the muscle
origin or insertion, as well as smaller vascular pedicles that enter the
muscle belly. Type III muscles, such as the gluteus maximus and rectus
abdominis, have two dominant vascular pedicles from separate
regional vessels that equally contribute to the blood supply. In contrast,
type IV muscles have a segmental blood supply through multiple
similarly sized pedicles that enter throughout the length of the muscle.
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Lastly, type V muscles have one dominant vascular pedicle that enters
close to the muscle insertion, as well as secondary segmental pedicles
that enter closer to the origin. Understanding of the vascular pedicles is
critical for skin paddle design, flap rotation, application of vascular
delay if necessary, and the use of the muscles as free flaps.
TABLE 7.1. MATHES AND NAHAI MUSCLE FLAP
CLASSIFICATION
Type
Vascular
Pedicle
Examples Considerations
I One
dominant
Gastrocnemius,
rectus femoris,
tensor fascia lata
Does not require
division of
vascular pedicle
for transposition
of myocutaneous
flaps
II One
dominant
with minor
supplemental
Abductor digiti
minimi, abductor
hallucis, biceps
femoris, flexor
digitorum brevis,
gracilis, peroneus
longus/brevis,
platysma,
semitendinosus,
soleus,
sternocleidomastoid,
temporalis,
trapezius, vastus
lateralis
Most common;
variable survival
of skin over distal
muscle
III Two
dominant
Gluteus maximus,
rectus abdominis,
serratus anterior,
semimembranosus
Two possible
arcs of rotation
based on the
paired pedicles;
may be able to
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preserve muscle
function by only
transferring one
portion on its
respective
pedicle; variable
survival of skin
over distal
muscle
IV Segmental Extensor digitorum
longus, extensor
hallucis longus,
flexor digitorum
longus, flexor
hallucis longus,
sartorius, tibialis
anterior
Multiple pedicles
must be
preserved to
ensure viability,
so potential arc
of rotation is
limited
V One
dominant
and
secondary
segmental
Pectoralis major,
latissimus dorsi
Two arcs of
rotation, as well
as safe reverse
arc of rotation
based on
secondary blood
supply; skin
circulation not
adversely
affected by
division of
secondary
pedicles
MYOCUTANEOUS FLAPS
Myocutaneous flaps are useful in instances in which both bulk and skin
are missing. The inclusion of the skin and subcutaneous tissue
overlying the muscle in the flap requires further understanding of the
musculocutaneous perforators arising from the main pedicle. In their
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landmark study, Mathes and Nahai noted that skin islands most distal
from vascular source are the least reliable.5 Type II and type IV flaps in
particular are known to have the least reliable skin paddles.
FASCIOCUTANEOUS AND PERFORATOR FLAPS
Fasciocutaneous flaps refer to flaps comprised of skin, subcutaneous
tissue, and deep fascia, including the prefascial and subfascial vascular
plexuses. These flaps became more widespread in the 1980s with
increasing knowledge of the blood supply to the skin.6 Anatomic
studies demonstrated that the skin is supplied by the direct cutaneous
vascular system in the subcutaneous fat, as well as musculocutaneous
perforators that pass perpendicularly from the muscular blood supply
and fasciocutaneous perforators that pass between the fascial septa of
adjacent muscles to reach the skin. Cormack and Lamberty described
a classification system for fasciocutaneous flaps in 1984 (Table 7.2).
7
This system is not currently used frequently, as the possibilities for flap
design have grown beyond these generalizations, but an understanding
of their classifications provides a useful foundation.
TABLE 7.2. CORMACK AND LAMBERTY FASCIOCUTANEOUS
FLAP CLASSIFICATION
Type
Vascular
Anatomy
Examples Considerations
A Multiple,
codominant
fasciocutaneous
perforators
Sartorius, upper arm Pedicled
B Single,
dominant
fasciocutaneous
perforator
Supraclavicular,
medial arm,
antecubital forearm,
parascapular
Pedicled or
free; may be
modified so
that flap
depends on a
single vessel
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feeding the
fascial plexus
C Single or
multiple
septocutaneous
perforators
Radial forearm Ladder-type
free flap that
includes the
skin, fascia,
and supplying
artery
D Inclusion of
other structures
like bone and
muscle along
the source
vessel
Osteomyocutaneous
radial forearm
Extension of
type C with the
fascial septum
taken in
continuity with
adjacent
muscle and
bone
The understanding of fasciocutaneous flaps led the way to perforator
flaps, formally defined by Wei et al. as cutaneous flaps based on
perforator vessels that penetrate a muscle and pierce (or “perforate”)
the fascia to reach the skin.8 Perforator flaps were first described in
1989 by Koshima and Soeda, who demonstrated that the vascularity of
a flap could be maintained without the inclusion of muscle or the
underlying fascia.9 The ability to harvest a flap without sacrificing or
damaging major vessels or muscles is beneficial, as it results in
decreased donor site morbidity and a potential improvement in esthetic
outcome.
Local Tissue Rearrangement
The understanding of perforator anatomy has not only led to more
diverse free flaps but also resulted in more versatile local tissue
rearrangement options, such as the propeller and keystone flaps.
Initially described in 1991, the propeller flap was first developed as an
island skin flap that was rotated 90° around a random subcutaneous
pedicle to release neighboring burn contractures.
10,11
Subsequent
modifications, such as the addition of multiple lobes, allowed for the
use of this type of flap with less of a need for skin grafting at the donor
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