preparatory text for 2-day cadaveric flap elevation course

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Course preparation
The Eastern Region: Flap Course
Monday 08 -Tuesday 09 October 2018
Ian Grant
MA (Oxon.), DM (Oxon.), FRCS (Plast.), European Diploma in Hand Surgery
Consultant Plastic Surgeon
Cambridge University: senior clinical tutor
Flap elevation is simple, it is one of the more straightforward challenges in surgery.
At the end of the course we want you to feel comfortable to raise an ALT, Fibula, Gracilis,
Gastrocnemius flap, and reverse sural flap. Some of you may also want to be taken through the
second toe, medial femoral condyle, and medial plantar flaps.
Please read through this text the weekend before you attend the course. To some of you it will
be revision, to some it will appear simplistic. We hope that some of you will find it helpful
preparation. We have not included any history, we have not included any rare anatomical
variations, or flap modifications. We have included only the most cursory clinical context.
During the course we will encourage to you to raise these flaps in a very prescriptive manner, to
allow multiple different flaps to be raised on the same specimen. Please consult one of the local
faculty should you feel the need to go “off-piste”.
Cambridge 01/10/2018

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The anterolateral thigh flap
The ALT is most commonly raised as a free flap: it’s location away from the head and neck area,
or on the ‘contralateral leg” in a patient with lower limb trauma allows the flap to be raised
simultaneously whilst another surgical team carries out the excisional surgery. The ALT can
provide skin, fascia, and muscle (vastus lateralis), and has a relatively long pedicle of about 7-9
cm in length.
The arterial supply is provided by the musculocutaneous (87%) or septocutaneous (13%)
perforators from the descending branch of the lateral femoral circumflex femoral artery (LCFA)
(image 1). Less commonly the perforators may originate from another source such as the
transverse branch of the LCFA.
Image 1
The venous drainage of the flap is supplied by the two venae comitantes that accompany the
arterial pedicle.
The flap can be made sensate by including the lateral femoral cutaneous nerve proximally. The
flap can be raised without need for a tourniquet.
Positioning
The patient is most commonly positioned supine.
Marking
A line is drawn from the Anterior Superior Iliac Spine (ASIS) to the lateral superior aspect of the
patella. At the midpoint of this line draw a 3cm diameter circle. Using a doppler probe identify
the perforators within this circle, which are most commonly found in the inferolateral quadrant.
(image 2). Use the doppler probe to identify additional perforators caudal or cephalad over or
immediately posterior to the intermuscular septum. When a large flap is to be harvested, it is
desirable to include more than one perforator.

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Image 2
The flap does not have to be centred over the perforators. A longitudinal ellipse will facilitate
skin closure. The junction of the proximal and middle third of the thigh is often the site of a
perforator that pierces the tensor fascia lata. This point can be incorporated in the flap to keep
the TFL perforator as a "lifeboat" in the rare circumstance when the distal perforators are of
poor quality or injured during dissection. The junction of the middle and distal third is marked
and is also incorporated into the flap.
Elevation
The ALT flap can be raised using a sub-fascial or supra-fascial dissection. The latter helps
produce a thinner flap. The sub-fascial dissection of the ALT flap allows easier identification of
the perforators to the skin, better exposure of the intermuscular septum, and descending
branch of the LSFA.
Sub-fascial dissection: the medial incision is made down to and through the fascia exposing the
rectus femoris muscle. The dissection then proceeds laterally to the septum separating the
rectus femoris and the vastus lateralis. The rectus femoris is retracted medially (image 3).
Image 3

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At the medial end of the septum the descending branch of the LSFA can be seen running over
the vastus lateralis. The surgeon can now see the vascular anatomy of the flap and can identify
the presence or absence of septocutaneous perforators, or musculocutaneous perforators.
The lateral border of the flap is elevated in a sub-fascial plane toward the septum, checking for
major perforating vessels emerging through the vastus lateralis. The lowest flap perforator
should be dissected toward the descending branch of the LCFA. When a flap perfuses from a
trans muscular perforator, then this perforator is traced through the muscle to the descending
branch. If a large septocutaneous vessel is present, it may be possible to proceed to a
retrograde dissection and avoid the need for intra-muscular dissection (this does not seem to
be a common occurrence). If the blood supply is entirely septal, the descending branch of the
lateral femoral circumflex artery is found at the base of the septum between the rectus femoris
and vastus lateralis and traced proximally.
The entire flap can then be isolated on the dominant perforator(s) and the descending branch
of the lateral circumflex femoral vessels.

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The distal based sural neuro-cutaneous flap
This is a distally based flap fascio-cutaneous flap which relies upon arterial vessels running
with the sural nerve. There are numerous anastomoses between this vascular axis (at times
referred to as the median superficial sural artery) and the peroneal artery. The most distal of
which is the lowest septo-cutaneous perforator from the peroneal artery: which is on average
5cm (4-7cm) above the lateral malleolus. This is the most distal arterial supply to the flap and is
the most distal pivot point. The “reverse flow” into the flap from this anastomosis accounts for
the occasional use of the term: “reverse” sural flap. Venous drainage of the flap is provided by
the short saphenous vein.
The flap is suitable for defects of the lower third of the lower leg, ankle and forefoot. It is
reliable and quick to elevate. Venous congestion or arterial insufficiency are usually the result
of technical errors.
The skin paddle donor site is over the posterior calf muscles: this usually produces a thin
pliable flap appropriate for the demands of the ankle and forefoot. The flap can be raised with
or without a tourniquet. It can be raised in the presence of most external fixators. Smaller flaps
can allow direct closure of the donor sites. The flap can be tunneled below a skin bridge (if a
tunnel of adequate size can be created with avoidance of any risk of compression of the
pedicle). If the donor site or the incision over the pedicle cannot be safely closed then a split
skin graft can be applied.
Use of this flap will result is a loss of sensibility over the fibular border of the foot. It is produces
a scar over the posterior calf and lower leg. Use of the flap is likely to be contra-indicated if
there is significant soft tissue damage at about 5cm above the lateral malleolus. The presence
of 2 or more co-morbidities (diabetes, venous disease, peripheral arterial disease) will increase
the risk of flap complications.
Positioning
It is arguably a lot easier to do this operation with the patient prone (but it can be carried out
with the patient in a supine of lateral position, if the surgeon is particularly mindful of the exact
midline of the posterior aspect of the lower limb.)
Position the leg prone: draw a line along the skin at the exact mid-point between the 2 heads
of the gastrocnemius muscles (image 1)

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Image 1
Marking
Mark the upper 50 % of an elliptical skin paddle with its long axis on the mid-point line. It
should at the apex be no higher than proximal point of the gastrocnemius muscles (image 2).
Image 2
Take a tape measure and check that apex of the flap will reach the end of the defect. Allow for
at least 1cm of variation in the position of the pivot point (identified with a doppler and marked
on the skin), allow for some folding of the pedicle and if the flap is to be passed onto the
anterior aspect of the limb, allow for curve of the lower leg.
Elevation
Cut through skin, expose the fascia. (If I am operating only my own I use a 2-pronged 7” Gelpi
retractor for symmetrical retraction). Cauterise any supra-fascial vessels. Cut through the
fascia making sure that the fascia is of equivalent size to the skin paddle. Do not disrupt the
loose adipose tissue between these 2 layers. Immediately the fascia in the mid-line you should
find: the short saphenous vein, and the sural nerve (image 3). Ligate these structures just distal
to the fascia.

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Image 3
Start to elevate the flap from proximal to distal keeping the sural nerve and short saphenous
vein on the undersurface of the flap fascia (which is gently lifted between the thumb and index
finger of your non-dominant hand). Be very careful not to disrupt the fine connections between
the sural nurse and the undersurface off the fascia.
I use a fine bipolar diathermy to lift all the vascular and fibro-retinacular tissue of the
gastrocnemius muscle.
One you have reached the flap equator, pause and check that the flap is aligned over the axis
of the sural nerve. The pedicle of the flap will extend toward the pivot point which is usually
5cm above the lateral malleolus and mid-way between the lateral border of the tendo-achilles
and the posterior border of the fibular. Draw the remaining skin paddle with the distal apex
angled toward the line of the pedicle (image 4). Cut through the skin to expose subcutaneous
fat.
Image 4
Draw a curvilinear incision over the likely path of the pedicle (a skin paddle tail over the pedicle
will improve the vascularity of the skin paddle but will make flap inset potentially more difficult.
Elevate subcutaneous flaps (keep a thin layer of “cobble stone” fat below the skin) adjacent to
the lower pole of the skin paddle and over the first part of the pedicle. Carefully incise fascia

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over the lower lateral border of the flap preserving a 2cm wide strip of fascia at the base of the
flap over the sural nerve.
Close to the mid-point of the lower limb the short saphenous vein and the sural nerve become
supra-fascial. This is usually close to the proximal end of the flap. By keeping all the fat over a
2cm wide strip of fascia, and by careful elevation of skin flaps over the pedicle, are preserved.
Continue this dissection until immediately above the pivot point, divide and ligate tributaries of
the short saphenous vein. Cauterize septo-cutanous perforating arterial vessels above the pivot
point. The most medial incision through the fascia, on the most proximal and medial border of
the pedicle, can extend beyond the level of the pivot point to ease transposition of the flap.
The tourniquet, if used, should be deflated before flap inset. Any twisting or potential
compression of the pedicle should be avoided.

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The Gracilis muscle flap
The gracilis muscle flap is commonly raised as a free flap, with or without a skin paddle. It can
be used to cover wounds roughly 6 cm wide and 20 cm long. It can be thinned and trimmed to
match the defect, it can be used for functional muscle reconstruction after paralysis, muscle
absence, or muscle loss. The flap can be pedicled for the reconstruction of groin wounds. The
arterial supply to the flap is from the gracilis artery branch from the medial femoral circumflex
artery. The venous drainage is provided by associated venae comitantes. The muscle is
innervated by a branch of the obturator nerve. The pedicle is between 4 and 6 cm in length.
The flap is quick and easy to raise. It can be raised as part of a two-team approach. The donor
site is generally considered acceptable, with no significant functional impairment on the donor
limb.
The Transverse Gracilis Musculocutaneous Flap
Anatomical studies have confirmed that there is strong transverse component to the
musculocutaneous vessels emerging from the gracilis. As a consequence it is possible to design
a transverse skin paddle extending > 5cm beyond the boundaries of the muscle, and with the
musculocutaneous vessels contained within a relatively small portion of muscle.
Positioning
Abduct the leg with patient supine and the knee bent. Feel for the adductor longus and two
finger breaths below this the gracilis (which should feel more superficial to the adjacent
muscles).
Drawing
Draw a line from the adductor longus tendon at the pubic tubercle and the tendon of semi-
tendinosis at the medial condyle of the knee. The Gracilis sits posterior to this line (image 1).
The maximal muscle belly width and the point at which the dominant pedicle enters the
muscle, sits about 10cm (+/- 2 cm) below ischium. To harvest a muscle flap make an incision of
about 15 cm in length centred on this point. If either a longitudinal or transvers skin paddle is to
be included: then include this area in the design of the pedicle (image 2).
Image 1

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Image 2:
Raising
Dissection proceeds in fascio-areolar plane between the adductor longus and the gracilis. The 2
distal and minor pedicles are divided. The adductor longus is retracted anteriorly, the dominant
pedicle of the gracilis is seen running between the adductor longus and brevis, entering the
gracilis muscle about 10cm (+/- 2cm) below the ischium.
If the muscle is to be harvested as a free flap, gentle traction on the muscle distal to the pedicle
will confirm the location of the distal tendon of insertion on the medial border of the knee:
allowing this tendon to be divided with a small stab incision.

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The medial gastrocnemius muscle flap
The medial grastrocnemius muscle flap is most commonly used to cover defects om the
anterior aspect of the knee. The arterial supply of the muscle is the medial sural artery (the
arterial supply of the lateral gastrocnemius muscle is the lateral sural artery). It can is raised
most commonly as a pedicled muscle flap or as a myocutaneous flap employing a skin paddle
over the muscle. (Skin perforators from the medial sural artery can also dissected in a
retrograde manner to allow elevation of a sural artery perforator flap).
Positioning
The patient is positioned prone with the hip abducted and the knee flexed. The flap can be
raised with or without a tourniquet.
Drawing
The incision is drawn roughly midpoint between the defect and the midline (image 1).
Image 1
Raising
Expose the muscle fascia over the medial gastrocnemius muscle belly and identify the mid-line.
The junction between the 2 muscle bellies is incised (preserving the short saphenous vein and
sural artery. Gentle finger dissection should define the plane between the gastrocnemius
muscle and the deeper soleus muscle. The muscle is then divided distally with a cuff of tendon
(image 2).

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Image 2
The muscle is then transposed to the anterior defect. The muscle can be expanded by multiple
scoring incision and the reach of the muscle can be improved by division of the muscles origin
from the femur.

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The fibula osseocutaneous free flap
Animesh Patel
The fibula flap is most commonly raised as a free flap to reconstruct bony defects.
The fibula flap can be raised as a bone-only flap, but more commonly is raised with a fasci-
ocutaneous paddle. The arterial supply to the bone is provided by the peroneal artery, while
septo- and musculo-cutaneous perforators from the peroneal artery supply the skin paddle.
Image 1
The venous drainage of the flap is supplied by the two venae comitantes that accompany the
peroneal artery.
The flap can be raised without a tourniquet.
Positioning
The patient is positioned supine. A padded wedge should be placed underneath the ipsilateral
hip, to help internally rotate the leg. The knee should be flexed: a padded support can be
placed underneath the foot to help maintain this position.
Marking
The fibula outline is marked on the lateral aspect of the leg. The line marking the posterior
border of the bone often corresponds to the posterior lateral intermuscular septum.

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Perforators to the skin paddle either pass through this septum or just posterior to it
(musculocutaneous perforators pass through the soleus and/or flexor hallucis longus muscle
bellies).
It is prudent to preserve about 7cm of fibula bone at both the proximal (to help protect the
common peroneal nerve) and distal (to maintain the distal tibio-fibular joint) ends.
Use a hand-held Doppler to auscultate for the cutaneous perforator(s). A skin paddle of the
appropriate dimensions to reconstruct the defect is drawn, incorporating the chosen
perforators (image 2). The skin paddle can be designed with the perforator in the centre of the
skin paddle or it can be designed eccentrically.
Image 2
Elevation
The anterior skin incision is made down through the fascia to the muscle (peroneal muscles of
the lateral compartment of the leg). The fascio-cutaneous skin paddle is elevated off the
muscle.
Sub-fascial dissection leads to the posterior lateral intermuscular septum (that divides the
lateral and posterior compartments). Follow down the septum to the fibula bone. Septo-
cutaneous perforators may be seen within the septum.

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Dissect the peroneal muscles off the fibula bone, leaving a thin cuff of muscle on the bone (to
help preserve the periosteal supply to the bone). This should be done along the length of the
bone to be harvested. As the dissection proceeds anteriorly, stop when the next fascial septum
is reached (the anterior lateral intermuscular septum-which separates the lateral and anterior
compartments).
Divide the anterior lateral intermuscular septum and enter the anterior compartment. Dissect
the anterior compartment muscles off the fibula bone, again leaving a thin cuff of muscle on
the bone (be careful not to injure the anterior tibial neurovascular bundle).
Stop when the next fascial septum is reached (the interosseous membrane-which separates the
anterior and posterior compartments).
To facilitate subsequent dissection, which is deeper, the proximal and distal bone osteotomies
can be made, preserving bone at both ends as described. As the desired length of bone flap is
freed by doing this, the bone can be toggled using bone-holding forceps and rotated allowing
better visualisation of the posterior compartment for the pedicle dissection.
Divide the interosseous membrane and enter the posterior compartment. The peroneal vessels
will be found in this compartment, and it is safest to identify them in the distal part of the leg,
and then proceed with pedicle dissection proximally.
The pedicle is dissected until the origin (i.e. the division of the tibio-peroneal trunk) being
careful not to injure the posterior tibial neurovascular bundle. The origin of the skin
perforator(s) will be encountered and should be preserved. If these are musculocutaneous,
further perforator dissection will be needed.
Image 3

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Once the pedicle (and perforator) dissection has been performed, the posterior skin incision
can be completed to isolate the entire skin paddle on its perforator(s).