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Classification of the VFTF is based on the vascular
"hook-up.
The VFTF placed between two arteries in an A-V-A fashion functionally
reconstructs that artery. The VFTF placed between an artery and vein (A-V-V)
functionally creates an A-V fistula.
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| An A-V-A hook-up on the long finger as illustrated by the
red box allows coverage for exposed flexor tendon and/or bone. |
An A-V-A hook-up on the thumb (red box) can cover exposed
distal phalanx in thumb amputations. |
The A-V-A orientation is useful in difficult
replantations where there is a soft tissue deficit and vessel injury resulting
in devascularization of the distal tissue. The blood, which flows through the
flap not only nourishes the flap but also revascularizes the replanted tissues.
Ring avulsion amputations and devascularizations are good examples where VFTFs
are particularly indicated. The crush component necessitates soft tissue
replacement, and the avulsion component necessitates vessel replacement. A VFTF
can resurface the tissue defect while revascularizing the digit at the sametime.
The A-V-V orientation is particularly useful in
fingertip resurfacing. Digital arteries taper and dorsal vein are just emerging
at the fingertip making them poor targets for anastomoses. In situations such as
soft tissue loss at the fingertip, additional vein length proximal and distal to
the cutaneous portion of the flap can be harvested. This allows the arterial and
venous anastomoses to be performed proximally where vessel size match is better.
This strategy also allows the anastomoses to be performed out of the zone of
injury.
The VFTF placed between two veins (V-V-V) can be
employed to fill soft tissue defects and cover exposed tendon on the dorsum of
the finger. Since veins supply the flap's inflow less perfusion pressure and
less oxygen content are delivered to the flap. This further restricts its
maximum size to less than that of an arterialized VFTF.
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| A V-V-V
hook-up on the index finger as illustrated by the red box allows coverage
for exposed extensor tendon, joint and/or bone. |
A V-V-V
hook-up on the dorsum of the hand (red box) enables exposed extensor
tendon and/or bone coverage. |
The superficial venous system located distally on
the extremity is less likely to have valves, has more extensive networking, and
is more intimately associated with and supportive of its overlying skin. This
improves the success rate making the hand, foot, and distal volar forearm
preferred donor sites for VFTFs. When a larger flap is required the proximal
forearm is the next best option. Direct visualization of the venous plexus
through the thin skin of the distal extremities allows precise design of the
VFTFs. The flap can not only be centered over the most appropriate plexus, but
creative inflow and outflow circuits can also be designed in the branching
venous system. The donor sites of small and moderate sized flaps can usually be
closed primarily.
VFTFs harvested from the leg and upper arm are
nourished by the saphenous and basilic vein respectively. These flaps are useful
when long vascular conduits or a larger soft tissue paddle is required. These
flaps are associated with increased subcutaneous tissue between the nourishing
vein and overlying skin. The smaller venous systems cannot be visualized and
their extent cannot be determined at the time of flap design. These flaps are
usually designed over the main vein. Their maximum width is restricted to insure
optimal survival.
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