Keywords propeller flap - definition - classification - update
The term propeller flap was introduced for the first time by Hyakusoku to define island flaps, based on a
subcutaneous pedicle hub, that were rotated 90 degrees to correct scar contractures
due to burns.[1 ] With a better understanding of the angiosome concept[2 ]
[3 ]
[4 ] and the superior role of perforator vessels in skin flap perfusion,[5 ] new applications using pedicled or local perforator flaps were soon developed,[6 ] including the propeller movement.[7 ]
Based on this anatomical knowledge, Hallock applied the propeller movement of a skin
island vascularized only by an isolated perforator, over the adductor compartment
of the thigh, using the terms propeller and perforator flap together for the first time.[8 ]
The subsequent work of Teo was of great importance in popularizing the use of propeller
flaps for soft tissue reconstruction.[9 ]
The presentations in propeller flaps sessions during subsequent perforator flap courses
or instructional meetings contributed to an exponential increase in interest in this
concept. Concurrently, a few scattered publications started to appear in the English
literature describing the propeller flap experiences of different groups, in the lower
limb,[10 ]
[11 ]
[12 ]
[13 ] and in other parts of the body,[14 ]
[15 ] from the upper limb[16 ]
[17 ] to the face[18 ]
[19 ]
[20 ]
[21 ]
[22 ] and to the trunk.[23 ]
[24 ]
At the First Tokyo Meeting on Perforator and Propeller Flaps, in 2009, faculty and
colleagues gathered from all around the world to present their experiences. On that
occasion, they proposed both a definition and a classification schema for propeller
flaps, as this was absent until then.[25 ] This was known as the “Tokyo consensus” and stated that a propeller flap can be
defined as an “island flap that reaches the recipient site through an axial rotation.”
This classification included three kinds of propeller flaps that differed on the basis
of the nourishing pedicle: the subcutaneous pedicled propeller (SPP) flap, the perforator
pedicled propeller (PPP) flap, and the supercharged PPP (SCP) flap.
A recent paper proposed an alteration of this classification of propeller flaps to
include new flap variations that have evolved.[26 ] One new category was called the “axial pedicled propeller” (APP) flap and included
island flaps that rotate on their pedicle 90 to 180 degrees. Instead of being nourished
by a perforator or by a subcutaneous “random” pedicle, these are vascularized instead
by a recognized axial vessel ([Fig. 1) ]
.
Fig. 1 Tokyo classification updated. Four types of propeller flaps are classified on the
basis of their nourishing pedicle: (1) subcutaneous pedicle propeller flaps, (2) perforator
pedicled propeller flaps, (3) supercharged perforator pedicled propeller flaps, and
(4) axial pedicled propeller flaps.
A slightly different classification concept was proposed by Ayestaray et al in 2011.[27 ]
According to their schema, four subtypes are differentiated on the basis of their
unique vascular pedicle: PPP flaps, SPP flaps, muscular pedicled propeller (MPP) flaps,
and vascular axial-pedicled propeller (VPP) flaps perforator flaps.
An overview of these salient points has led to our updated classification of propeller
flaps ([Fig. 2 ], [Table 1 ]):
SPP flaps.
PPP flaps.
VPP flaps.
MPP flaps.
Chimeric propeller flaps.
Fig. 2 New comprehensive classification of propeller flaps. Five types of propeller flaps
are classified on the base of their nourishing pedicle: (1) subcutaneous pedicle propeller
flaps, (2) perforator pedicled propeller flaps and its subtype (2a) supercharged perforator
pedicled propeller flaps, (3) axial pedicled propeller flaps, (4) muscle propeller
flaps, and (5) chimeric propeller flap.
Table 1
New comprehensive classification of propeller flaps
Flap type
Pedicle
Rotation
Vessel of origin
Dissection technique
Details
Example
1
Subcutaneous pedicled propeller flap
Random (perforator not visualized)
Up to 90 degrees
Not known
Macroscopic
The first defined as propeller
Elbow in burns (first described)
Lotus flap[1 ]
2
Perforator pedicled propeller flap
Dissected perforator
Up to 180 degrees
Plausible or visualized
Magnification needed
The one mostly used
Propellers of the leg[11 ]
2a
Supercharged perforator pedicled propeller flap
Dissected perforator + extra vein or artery
Up to 180 degrees
Plausible or visualized
Magnification needed + Microsurgical anastomosis
In case of congestion (venous anastomosis) or for larger flaps (artery/vein)
Trunk, limbs[28 ]
3
Axial pedicled propeller flaps
Known axial vessel
Up to 180 degrees
Known (constant)/visualized
Magnification needed
Evolution of axial flaps
Lingual artery propeller[38 ]
4
Muscle propeller flaps
Main vessel or branch to the muscle
Up to 180 degrees
Known (constant)/visualized
Magnification advisable
Evolution of Muscular flaps
Trapezius muscle propeller[31 ]
5
Chimeric propeller flaps
Vessel to the first tissue + dissected perforator
180 degrees + 180 degrees
Known + visualized
Magnification needed
Bone or muscle flap + perforator pedicled propeller
Razor flap[40 ]
Classification of Propeller Flaps Based on Their Vascular Pedicle
The source of the nourishing pedicle to the given propeller flap is probably the most
important variable for the classification of propeller flaps.
Subcutaneous Pedicle Propeller Flaps
This type of propeller flap has limited usefulness depending on specific conditions
and anatomical sites. For example, burn contractures of mild or sometimes even moderate
severity, especially if involving the axilla or elbow, can be released and covered
with these flaps using the remaining unburned skin, as was originally described by
Hyakusoku.[1 ] Several variations of this technique may be applied to better optimize the result.[28 ]
[29 ]
[30 ]
The perineum is another region where this subtype of propeller flap is most useful
as exemplified by the “lotus flaps.”[31 ] In some instances, propeller flaps of the facial artery are also better raised with
this technique, especially when the arterial perforator and the venous perforator
lie at some distance from one another, as is characteristic.
Perforator Pedicled Propeller Flaps
The majority of flaps in the literature that are called “propeller flaps” belong to
this category. Their range of rotation can reach 180 degrees, as long as the perforator
pedicle is followed and isolated enough toward the main source vessel. The most popular
PPP flaps arise in either the trunk, such as those based on internal mammary artery
perforators,[32 ] lateral intercostal artery perforators, or lumbar perforators, or on the lower extremity,[33 ]
[34 ] such as those based on posterior tibial and peroneal perforators.[10 ]
[11 ]
[12 ]
As recognized in the Gent consensus and subsequent updates,[35 ] perforators can reach the skin either directly through a septum or indirectly through
muscle or some other tissue medium. Thus, PPP flaps can be further subcategorized
into the following:
Axial or direct cutaneous type (e.g., superficial circumflex iliac artery perforator).
Septocutaneous type (e.g., radial forearm).
Musculocutaneous type (e.g., thoracoacromial).
Supercharged Perforator Pedicled Propeller Flaps
This subtype is rarely used, and that too mostly for the prevention of complications.
A microanastomosis is required, and therefore this makes the overall procedure much
more complicated. The size of the flap can be extended to include the next perforasome
by arterial supercharging.[36 ] Venous superdrainage may be required for perceived flap congestion, but it is also
used routinely for some flaps or surgical settings as a preventive measure to lessen
the risk and thereby also to avoid the need for a hospital admission.[37 ]
Axial Pedicled Propeller Flaps
This is a newer category that includes only island flaps that are based on an axial
vessel that enters the flap perpendicular to its surface, without ever being a deep
fascia perforator. Reach to the recipient site is with a propeller or rotation movement.
To reiterate, the pedicle is neither a perforator nor subcutaneous tissues but a clearly
isolated vessel.
Prior propeller flaps that have been described in the literature and are considered
to fall into this category are the STAAP (supratrochlear artery axial propeller) and
the DLAAP (deep lingual artery axial propeller) flaps.[26 ]
[38 ] This inclusion is not without criticism. For example, the propeller flap based on
the supratrochlear artery is considered by some to be no different than any other
perforator-based propeller flaps, as the nourishing vessel pierces the corrugator
and frontalis muscles before entering the subcutaneous layer and therefore in fact
is a musculocutaneous perforator.
It is certainly more difficult to classify the propeller flap DLAAP. First, the flap
consists only of muscle and mucosa, and, second, the deep lingual vessel enters the
flap in a perpendicular fashion without ever perforating any other tissue such as
fascia. Thus, we must accept this flap variation to be part of a different class of
propeller flaps, that is, the APP flaps, as proposed.
Muscle Propeller Flaps
Although in the beginning of propeller flap history, all propeller flaps were skin
flaps, over the years, propeller flaps that are comprised of other tissues have been
described. Because the Tokyo consensus defined a propeller flap as an “island flap
that reaches the recipient site through an axial rotation,” not only skin island flaps
but also island flaps of fascia, subcutaneous tissue, mucosa, and even muscle can
be called propeller flaps if rotated on their axis, as exemplified by the already
mentioned DLAAP flap.[38 ] An example of the muscle pedicled propeller flap would be the trapezius muscle propeller
flap,[39 ] where a portion of the trapezius muscle was rotated 160 degrees on the axis of the
dorsal scapular artery pedicle of the muscle.
Chimeric Propeller Flap
This is an evolution of the chimeric flap concept, which itself is defined as being
composed of multiple independent tissues and connected only through branches of the
same main vessel. When one or more of the components of the flap have a movement of
rotation on the axis of their specific pedicle, but without a complete dissection
back to the source vessel, then that part can be considered a propeller flap, and
the entire complex can be named a chimeric propeller flap. Probably, the first description
of this variation was by Cavadas and Teran-Saavedra, who called this a “razor flap.”[40 ]
The advantage of the chimeric propeller flap is even greater freedom of movement of
the different components to allow simultaneous coverage of different defects or parts
of the same defect, with tissues having different attributes (i.e., more malleable
muscle to fill a deeper defect and then skin to facilitate superficial wound closure).[41 ]
Classification of Propeller Flaps Based on Nonvascular Variables
Sometimes, other characteristics of a propeller flap need to be described to allow
a more complete understanding of how the flap was designed and transposed to ensure
that the methodology is sound, reliable, and safe ([Fig. 3 ]).
Fig. 3 Classification of propeller flaps based on all the variables: type of nourishing
pedicle, degrees of skin island rotation, position of the nourishing pedicle, artery
of origin of the pedicle, and flap shape.
Degrees of Skin Island Rotation
The degree of rotation of a propeller flap may vary up to 180 degrees, and the actual
amount will depend on the position of the perforator in relation to the defect. This
rotation will also depend on how the skin island is designed, which usually will be
according to the expected distribution of the perforator branching pattern in the
involved subcutaneous and subdermal tissues.[42 ]
Position of the Nourishing Pedicle
The nourishing vessel usually enters perpendicular to the undersurface of the flap
either in the center (typically as would be a subcutaneous pedicled propeller flap
for scar contractures) or, more frequently, in an eccentric position. The latter would
be the more advantageous for local soft tissue reconstruction, as the larger portion
of the skin island can be used to cover the defect while the minor paddle is either
discarded (as in a 90-degree rotation) or used to resurface a portion of the major
paddle donor site.
Artery of Origin of the Pedicle
In most cases, according to the body region and our knowledge of the normal vascular
anatomy, the artery of origin of the perforators of that area could be reasonably
hypothesized for each propeller flap. This is generally true for the perforator based
propeller flaps but less precisely so for SPP flaps. In other anatomical areas, the
contiguity of multiple source vessels, that give origin to several perforators, makes
it difficult to precisely specify the vessel of origin of a given observed perforator.
An example of this difficulty is the thoracic region in proximity to the axillary
lines, where perforators of the intercostal vessels, thoracodorsal vessels, serratus
branch, circumscapular, or lateral thoracic may easily be confused one with the other
(although not always having negative clinical consequences when harvesting a propeller
flap).
Flap Shape
As a consequence of the usually reliable perfusion of propeller flaps, the shape of
the skin island may often freely mimic the shape of the defect. Thus, the flap configuration
may vary from an ellipsoid island, bemultilobed, or completely custom-made to each
defect.
Conclusion
This brief introduction has been intended to reiterate the historical development
of the propeller flap, as we have witnessed. An updated definition of this concept
and a classification schema that distinguishes between new and old variations of propeller
flaps will surely open multiple points for discussion that hopefully will lead to
even better improvements that can only enhance its versatility.
