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SPECIALISED FLAPS
1)
2)
3)
4)
5)
6)
Sensory neurovascular,
Osseo-cutaneous,
En bloc (composite) flaps
Venous flaps
Reverse flow flaps
Pre-fabricated flaps
1. SENSATE FLAPS
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Littler’s neurovascular island flap (1960) from the ulnar aspect of the MF to resurface the
distal pulp of the thumb was the first example. Sensation was often restored to the Th,
but thought to arise from theMF! (Localisation was poor).
Principles of neurovascular free flaps (Daniel, Terzis and Midgley, 1976)
1. Vascular distribution and sensory innervation must overlap
2. It must be possible to isolate the flap on an anastomosable vascular pedicle
3. The nerve supplying the flap must be identifiable and anastomosable
4. The quality of sensation must be appropriate for the defect
5. The donor site morbidity must be acceptable.
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The dorsalis pedis flap showed that re-innervation did occur and that localisation was
possible.
Wrap-around flap from the big toe to the thumb provides good 2 point discrimination,
durable coverage and the option of incorporating a nail.
Radial forearm flap can provide sensation via the lateral cutaneous n of the forearm.
Intercostal flaps (a single intercostal n/v bundle can support a flap 5 intercostal spaces
wide) can be used to provide sensate flaps for sacral sore coverage in plegics.
2. OSSEOCUTANEOUS FLAPS
Used first by Blair (1912) when he incorporated clavicle in a cervical flap.
Taylor (1982): free fibula flap, osseocutaneous groin flap (deep circumflex iliac).
Vascularised bone has the following advantages over non-vascularised bone graft:
1.
2.
3.
4.
higher rate of union,
hypertrophies earlier,
has greater mechanical strength,
has a lower rate of infection (and thus non-union.)
3. COMPOSITE FLAPS
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The old school: For a complex facial defect (eg, post GSW), multiple flaps and grafts would
be used: local flap for oral lining, rib graft for bone, delto-pectoral flap for skin. Infection
and necrosis were the common result.
The modern school (Daniel, 1978; Taylor, 1982; Swartz, 1986): Single en bloc composite
free tissue transfer. Advantages are better blood supply with resultant better healing and
better cosmetic results.
4. VENOUS FLAPS
 A flap based exclusively on a venous pedicle that is anastomosed to either a vein or an
artery (arterialised). There may be no outflow or an exiting vein may be anastomosed to
an artery or a vein.
Types (Nakayama, 1981)
Type
Inflow
Pedicle
Outflow
1.
VO
venous
venous
none
Single pedicle venous flap
2.
VV
venous
venous
venous
Flow through venous flap
3.
AV
arterial
venous
venous
Arterialised venous flap
4.
AA
arterial
venous
arterial
Arterialised venous flap
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Type 1 may be subdivided into proximally or distally based.
Type 2 may be divided up into free flaps, unipedicled flaps or bipedicled (sliding) flaps.
Types 1 and 2 rely on venous perfusion and are said to survive as a graft!
Types 3 and 4 are arterialised venous flaps. Inflow and outflow may be orthograde or
retrograde further subdividing the group (o/o, o/r, r/o, r/r). Higher pressures lead to
greater survival.
Classification (Thatte and Thatte)
Type 1 – supplied by a single venous pedicle
Type 2 – venous flow-thru flap (V-V-V)
Type 3 – arterialized venous flaps
A-V-A
A-V-V
Theories
1) Reverse Shunting
a. With denervation, AV Anastomoses allow retrograde flow from the veins to
the arterioles and then antegrade flow through the nutrient capillary beds and
out through the veins.
2) Reverse Flow
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a. retrograde flow from the veins through the nutrient capillary bed into the
arterioles and then antegrade flow back out the veins via A-V shunts or other
capillary beds.
3) Capillary Bypass
a. normal tissue can extract up to 50% of the oxygen content of blood prior to it
reaching the capillary beds
b. flaps like the VFTF survive on the lower oxygen content supplied by
antegrade flow through the venous plexus.
4) As a composite graft: plasmatic imbibition and neovascularisation.
a. Rapid arterialisation aided by the presence of draining vein
VFTFs designed with a central venous plexus with two or more efferent veins have a
survival pattern similar to that of conventional flaps which have an inflow artery and
outflow vein.
Potential VFTF donor sites:
1. Distal Volar Forearm
2. Proximal Volar Forearm
3. Dorsum Digit/Hand
4. Dorsal Foot
5. Medial Thigh/Leg
6. Upper Arm
Advantages
1. Revascularized and resurface
2. Single stage procedure
3. Thin/pliable tissue
4. Low donor morbidity
5. Spares donor artery
6. Constant long pedicle
7. Good cosmetic result
8. Can include composite tissue
Disadvantages
1. Germann showed poor O2 consumption, early thrombosis and no flap survival.
2. Small size, variable rate of tissue necrosis, formation of AVF (haemodynamic
effects).
Clinical Experience
 Most venous flaps are based on the prominent veins of the limbs: cephalic or saphenous.
 Arterialised perfusion better than pure venous.
 Wolff examined 3 types of venous flaps with respect to perfusion and long term survival:
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i) arterialised venous flaps: 93%
ii) flow through venous flaps: 63%
iii) venous island flaps: 31%
5. REVERSE FLOW FLAPS
 By virtue of their design (eg distally based flaps), some flaps exhibit reversed vascular
flow, ie, retrograde flow.
 Since the arterial system does not contain valves, reversal of flow is not problematic.
 The venous system has valves - how does flow reverse?
 Two systems of venous arcades facilitate the reversal of flow:
1. Macro-venous connections
a)
Valveless oscillating veins
o
Inter-connecting veins, devoid of valves, 1-3 mm in
diameter which skip the valves of the venae comitantes (like
a ladder).
o
allow venous flow in any direction under pressure
o
connects between larger valved superficial veins
o
Crossover and bypass patterns (reverse radial artery flap –
Lin 1984)
i. Crossover branches between the two venae comitantes
ii. Bypass branches within each vein
b)
Incompetent valve (radial artery - Nakajima 1997)
o
Effect of pressure and denervation
o
Veins with relatively weak valve resistance became the
drainage pathway.
2.
Micro-venous connections
a)
Plexus of tiny veins, also free of valves, which surround the artery as
the venae arteriosa.
b)
Although these are sufficient, they are small and require a relatively
high pressure and time to dilate and allow blood flow.
c)
Venous congestion will therefore occur for the 1st 12-24 hours while
these veins dilate
6.
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PRE-FABRICATED FLAPS
Introduced by Orticochea and Washio (1971).
Termed prelamination by Pribaz and Fine.
Allows the creation of an unlimited array of composite flaps. Can create what is needed.
Can be combined with expansion and delay to increase versatility still further.
Facilitated by the reliability of free flap transfers: uniformly > 95%, usually 99%.
Methods
Based on 1 or more of the following principles:
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1.
2.
3.
4.
Delay or expansion
Grafting (skin, cartilage, etc)
Vascular induction (staged flap transfer)
Experimental: Tissue transformation from one type to another
1. Delay and Expansion
 A powerful tool to increase the safety of flaps. Extends the limits of perfusion.
 Expansion of a flap may allow primary closure to the donor site or a much larger flap to
be created to cover a large defect.
 Can allow expansion to be done in a safe area rather than an unsafe area, eg, a scapula flap
can be expanded prior to transfer to the lower leg where expansion would be hazardous.
2. Pre-transfer Grafting
 Necessary when
i) complete graft take is mandatory to the success of reconstruction
ii) when post-transfer grafting is not feasible or practical
 Can be done for pedicled and free flaps.
 Pedicled flaps: Para-median forehead flap can be grafted with skin and cartilage prior to
transfer for nasal reconstruction. Temporo-parietal flap can be pre-grafted with skin to
close palatal defect or nasal defect (can be used free too).
 Free flaps: Creation of a urethra in a RFF.
3. Vascular Induction (true prefabrication)
 Any selected block of tissue, regardless of its native vascular anatomy can become a
transferable flap by inducing a vascular carrier to perfuse it. Based on the well
established principle of staged flap transfer (eg, using the wrist as a carrier).
 The vascular carrier can be a small flap of muscle, fascia, intestine, omentum, or even an
arteriovenous bundle or fistula. This is implanted beneath the tissue that one wants to
transfer and by a process of neovascularisation the two become incorporated after a
relatively short period of time.
 Orticochea transferred STA into retroauricular concha and then transferred conchal skin
and cartilage to the nose for reconstruction.
 Shen implanted the descending branch of the lateral femoral circumflex artery
subcutaneously in the thigh (vascular induction stage) and then after 6 weeks transferred
it as a free flap to resurface a burn contracture of the neck.
 Omentum has been placed in the lower abdominal fat which has then been used for breast
reconstruction.
 The radial artery has been placed subcutaneous in the abd and then the abd skin
transferred to the head as a free flap based on the radial artery.
 Temporo-parietal free flap, hitched to dorsalis pedis artery and wrapped around the 2nd
toe PIPJ as a 1st stage. 2nd stage is harvest of the composite temporo-parietal flap and
toe PIPJ which can be transferred to the hand.
 Veins have also been placed beneath a future flap for transfer.
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 Revascularisation can be hastened by the application of angiogenic growth factors (TGF,
FGF, PDGF).
4. Flap Tissue Transformation
 Regulating gene expression and cell biology are now making this a reality.
 Involves the use of bone morphogenic proteins which can allow the conversion of a
simple muscle flap into an adequate piece of vascularised bone of the required shape and
size. Silicone moulds are used into which is placed the muscle flap and BMP.
Advantages
1. Allows more tissue to be transferred.
2. Allows any tissue to be transferred.
3. Allows specialised tissue to be transferred.
4. Can reduce donor site morbidity.
5. Allows elegant transfer of an already functional unit and can reduce the number of stages
required.
But requires a lot of investment into a flap.