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Page 6 of 11 Yu et al. Plast Aesthet Res 2022;9:37 https://dx.doi.org/10.20517/2347-9264.2021.124

The latissimus dorsi flap has several options as a flow-through flap. The largest caliber flow-through vessel
comes from the continuation of the circumflex scapular artery from the subscapular artery; the
thoracodorsal branch comes off this intervening segment. The subscapular is used as the proximal
anastomosis and the circumflex as the distal when transplanted to the leg. During pedicle dissection, the
serratus branch is kept intact as a backup flow-through option. If aberrant anatomy is encountered, the
serratus branch and proximal thoracodorsal can be used as the flow-through segment, with the distal
thoracodorsal preserved for flap perfusion. A flow-through latissimus dorsi flap for reconstruction in a
traumatized lower extremity with single-vessel runoff is demonstrated [Figures 3 and 4].

For the flow-through ALT flap, the descending branch of the lateral femoral circumflex artery can be taken
distal to the site of perforator takeoff and used as the distal flow-through segment. This creates a long length
to reconstruct a vessel with a large zone of injury. The length of the total flow-through segment is
dependent on the position of the most distal perforator being utilized. A shorter flow-through segment can
be created with the ALT flap by taking an additional length of the rectus branch, as this vessel is frequently
quite large in caliber and can serve as the distal anastomotic site.

For the radial forearm fasciocutaneous flap, the radial artery acts as the flow-through vessel, and the
proximal and distal ends are anastomosed to the recipient vessel. The perforators branching from the radial
artery provide blood supply to the fasciocutaneous flap.

There are several disadvantages to the use of flow-through flaps. There is a risk that potential thrombosis
could cause distal perfusion/limb viability issues when operating on the only vessel providing blood flow to
the distal extremity. There is a theoretical risk of steal syndrome. With two sites of vessel anastomoses, there
are two sites of potential thrombosis, which could lead to either flap or foot ischemia. Frequently, one site of
anastomosis has a vessel mismatch and requires precise suture placement for correction. Awareness of these
pitfalls prompts the surgeon to use a meticulous technique, and at our institution, we have found flow-
through flaps to be very reliable.

Vein grafts
If there are no viable recipient vessel sites within a reasonable distance of the defect, which can be the case
with a large zone of injury, vein grafts are required to bring inflow from healthy proximal vessels. This is
most often done using an arteriovenous (AV) loop, which can be performed as a single or two-stage
procedure [31,32] . The two-stage procedure has a higher graft occlusion rate and lower limb salvage rate, and
thus, the single-stage AV loop is recommended [31-33] . AV loops are reliable for providing inflow when none
[34]
is present distally - Momeni et al. showed no difference in reconstructive outcomes between traumatic
lower extremity wounds reconstructed with a single-stage AV loop and those without an AV loop in a pair-
matched study.

In creating an AV loop in the lower extremity, the greater saphenous vein is most commonly used. If
enough length is able to be obtained distally, the saphenous vein may be used in situ: the distal end is
mobilized and reflected proximally to anastomose with the femoral artery, necessitating only one
anastomosis. When a greater length is needed, or the more distal vein is in the zone of injury, the
contralateral saphenous may be harvested and used as a free vein graft to connect to the femoral artery and
femoral vein in the adductor hiatus. The anastomosis to the femoral artery may be achieved in an end-to-
side fashion or end-to-end with a branch of the femoral artery. A temporary fistula is created through the
graft with continuous circulation. After flap harvest, the AV loop is divided at its apex, and the arterial and
venous segments are anastomosed to the respective flap pedicle vessels. This minimizes the number of