Keywords anterolateral thigh flap - technique of alt harvest - free flap reconstruction - donor
site morbidity in alt - chimeric alt flap - multiple paddle alt - bipaddle alt harvest
Introduction
The versatility of the anterolateral thigh (ALT) flap for reconstruction of complex
defects following cancer ablation is well documented.[1 ]
[2 ] It allows harvest of multiple flap components and skin paddles based on separate
perforators. It has minimal long-term complications and donor-site morbidity as compared
with other thin fasciocutaneous flaps.[3 ]
[4 ] Donor site morbidity is also minimal if it is closed primarily. Harvest without
vastus lateralis (VL) and leaving its nerve supply intact decreases morbidity, with
minimal postoperative muscle weakness or restriction in knee movements or impairment
of activities of daily life seen.[5 ]
The branches of the femoral nerve innervating the VL are intimately related to the
vascular pedicle and perforators of the flap. Variations in anatomy and branching
pattern of the nerves occur. The nerve may be travelling along or under or over or
may be intertwined with the pedicle or perforators of the flap. Single perforator
harvest is usually done preserving the entire nerve arborization. During harvest of
chimeric or multi-paddle flaps, the preservation of two or more perforators in the
presence of complex anatomy invariably leads to sacrifice of the nerve or its branches.
We propose a ‘Divide’ and ‘Deliver’ technique of harvesting multi-paddle or chimeric
ALT flaps, which enables saving all nerve branches.
Case Series
We employed this in-situ ‘Divide’ and ‘Deliver’ technique in 27 cases over 5 years
to preserve the integrity of the nerve, its branches and the perforators. (19 chimeric
ALT and 8 ALT + TFL flaps).
These cases were multi-paddle flaps planned for reconstruction requiring mucosal lining
and skin defects and in whom the nerve to VL or its branches were entangled and interlaced
with the perforators of the flap.
The harvest was done in a standard manner with a noncommittal anterior straight incision
(Doppler-guided), sub-facial perforator to pedicle dissection, without harvesting
VL and preserving all nerve branches ([Fig. 1 ]).
Fig. 1 Free ALT flap dissected with two perforators and a branch of the nerve to vastus
lateralis muscle going in between the two perforators.
An estimate of the flap size required was done after assessment of the defect. Skin
paddles of the flap were planned and after reconfirming the defect size, the skin
paddles were ‘divided’ in situ, keeping the pedicle intact. Once divided, the skin
paddles were maneuvered so as to ‘deliver’ them from between the branches of the nerve
([Fig. 2 ]). The dissection was then completed to separate the nerve and its branches throughout
its entire course from the perforators without any damage ([Fig. 3 ]).
Fig. 2 One of the two skin paddles is being maneuvered and delivered from between the branches
of the nerve.
Fig. 3 The divided skin paddles are delivered from between the nerve branches to preserve
both the perforators and also the nerve branches.
The average width of the flap was ∼7 cm and the donor area was closed primarily.
All flaps were planned so as to be divided based on separate perforators. Postoperative
course of the patients in the ward was uneventful. There was no incidence of flap
loss or marginal necrosis. All flaps survived without any major complications. The
reported donor site morbidity was minimal, with no complaints by the patients. There
was no reported loss of sensation over lateral thigh and no change in gait or weakness/difficulty
in extension of the knee, was encountered or reported.
Discussion
Nerve preservation is a deliberate purposeful act in ALT harvest, for which extreme
care in dissection and awareness of anatomy is needed. It is as important as muscle
preservation to reduce the functional donor site morbidity. Hence, perforator dissection
needs to be done with a simultaneous aim of preserving nerves and muscles. Magnification,
immaculate hemostasis, bipolar cautery for dissection, microvascular instruments for
perforator and pedicle handling, all reduce chances of injury.
The descending branch of the lateral circumflex femoral artery gives multiple perforators
that supply the skin paddle, which are closely related to branches of the nerve to
the VL. There are many spatial variations in the course of the pedicle, the nerve
to VL, its branches and the perforators.[5 ] Anatomical variations include the nerve passing through the pedicle of the ALT flap,
or passing between perforators, seen in 28% of a 36-human cadaveric thigh dissection
study.[3 ] In good hands, during harvest based on a single perforator/pedicle and no muscle,
all nerves and branches can usually be preserved. However, harvest of multi-paddle
chimeric ALT flaps require multiple perforators that are identified, dissected, and
preserved. When unfavorable variations of nerve anatomy are encountered, wherein the
motor nerve passes through the vascular pedicle itself or passes between perforators
supplying the flap, the nerve or its branches are invariably cut to preserve the perforators.
Donor-site dysfunction is found to positively correlate with the degree of damage
to the nerve to VL and/or harvest of VL and rectus femoris muscle or its innervation/blood
supply during tissue harvest.[5 ] Muscular weakness, fatigue, pain, knee instability, and rarely gait abnormalities
have been found to occur as a consequence of such nerve damage.[6 ]
[7 ]
[8 ] To reduce donor site morbidity, it has become imperative to device newer methods
of harvest, which preserve the integrity of the nerve throughout its course.
‘Divide and Deliver’ technique entails in-situ planning of the skin paddle by assessing
the defect. ‘Dividing’ of the skin paddle of appropriate size, based on separate perforators,
keeping the pedicle intact. The paddles are then ‘delivered’ from the interlaced nerve
branches/ loops of nerves, safeguarding the nerve branches as well as the perforators.
([Figs. 4 ]–[7 ]).
Fig. 4 ALT flap with 2 perforators with one perforator running below the nerve.
Fig. 5 Skin paddle is ‘divided’ and one of the paddles is ‘maneuvered’ (delivered) around
the nerve.
Fig. 6 Skin paddle is ‘divided’ and one of the paddles is ‘maneuvered’ (delivered) around
the nerve.
Fig. 7 Skin paddle is divided and delivered to preserve the nerve and perforators.
By application of this simple technique, we can safeguard the nerve supply of VL and
its function, reduce postoperative donor site morbidity and enhance the functional
recovery of the patients ([Table 1 ]).
Table 1
Advantages and limitations of the technique
Advantages
Limitations
Nerve supply of vastus lateralis is always completely preserved thus, preserving function
and decreasing donor morbidity
Can be applied to specific defects only
Better results can be achieved by using various components of the chimeric flap for
adequate reconstruction of the defect in all 3 dimensions (length, width, and depth)
Needs dissection of multiple perforators
Defects need to be assessed and measured perfectly as once components are divided,
then modifications are not possible
This technique can also be employed for other chimeric flaps or when large ALT needing
a STSG for closure is required.[9 ] Here a longer flap with primarily closable donor area can be harvested preserving
the nerves. The flap can be divided into separate components or paddles based on separate
perforators, which are subsequently rearranged to cover a larger defects.
Conclusion
In-situ ‘divide’ and ‘deliver’ technique of ALT harvest is an effective tool to reconstruct
complex head and neck defects with minimal donor site morbidity. This concept can
be extended to reconstruction of other complex defects of the chest/extremities by
multi-paddle ALT flaps with an eye to achieve both aesthetic and functional goals
without any donor-site impairment by avoiding sacrifice of the nerve during harvest.
