Augmentation of Venous Outflow for Salvage of a Combined Anterolateral Thigh, Tensor Fasciae Latae, and Rectus Femoris Free Flap Used for Abdominal Wall Reconstruction

We present a case of near-total abdominal wall reconstruction using a combined anterolateral thigh (ALT), tensor fasciae latae (TFL), and rectus femoris (RF) free flap that was complicated by acute venous congestion and was salvaged by adding a vascular tract in parallel to the flap's venous system.

A 46-year-old female presented with a perforated sigmoid colon and associated necrotizing fasciitis of the anterior abdominal wall. After multiple debridements ([Fig. 1A]), abdominal wall reconstruction was performed using a right sided ALT/TFL/RF combination free flap sewn into the left sided femoral vascular system. A large RF perforator, two septocutaneous ALT perforators from the descending branch of the lateral circumflex femoral (LCF) artery, and a TFL perforator from the transverse branch of the LCF artery were identified ([Fig. 1B]). A flap measuring 25 × 35 cm was then raised on all four perforators, and the vessels were skeletonized back to their common LCF origin. To create recipient vessels for the flap, the left greater saphenous vein (GSV) was cut distally and then reflected 180 degrees for end-to-side anastomosis into the femoral artery, creating an arteriovenous (AV) loop that was then tunneled under the inguinal ligament toward the abdominal wall defect ([Fig. 1C]). The AV loop was then divided. The segment grafted to the femoral artery was anastomosed to the flap's LCF artery ([Fig. 2A]). The remaining GSV segment was anastomosed to the flap's LCF vein (LCFV, [Fig. 2B]).

Fig. 1 Defect, flap harvest, AV loop, and integrated flap. (A) Near-total abdominal wall defect with obliteration of the deep and superficial epigastric vessels. (B) The flap was raised on pedicles from the lateral circumflex femoral system: the transverse branch to the tensor fasciae latae, the descending branch to the anterolateral thigh, and the rectus femoris perforator. (C) An arteriovenous loop using the great saphenous vein. (D) At 1 month after discharge.

Fig. 2 Flap vasculature and resistance calculation. (A) Arterial inflow from the femoral artery was provided by a great saphenous vein (GSV) graft tunneled under the inguinal ligament and connected to the lateral circumflex femoral artery. (B) Initial venous drainage was performed by the GSV anastomosed to the lateral circumflex femoral vein, with estimated resistance of 590 Pas/mL using Hagen-Poiseuille law. (C) Following recurrent venous congestion, flap salvage was performed by parallel augmentation of venous outflow. The descending branch vein draining the anterolateral thigh (ALT) was cut and connected to a new GSV graft anastomosed with the femoral vein. The new estimated resistance is 560 Pas/mL, representing a 10% decrease in resistance and 10% increase in flow. Sites of anastomosis are marked.

After 30 minutes of anastomosis the flap developed a dusky appearance, suggesting venous congestion. The LCFV/GSV anastomosis was opened, and a white clot was identified in the recipient GSV. Intravenous heparin was administered, and the venous system was reconnected. Despite continued venous drainage through the LCFV and GSV, the flap continued to produce brisk, dark bleeding following pinprick. Therefore, we decided to add a second venous outflow tract. A 15-cm segment of the right GSV was harvested, connected to the left common femoral vein in an end-to-side anastomosis, and tunneled under the inguinal ligament. The descending branch of the LCFV, distal to its union with the RF perforator, was then cut and coupled to the new GSV graft ([Fig. 2C]). Temporary clamping of the LCFV revealed steady flow through the descending branch and the new parallel outflow tract. On the first postoperative day, the flap displayed a healthy, pink color.

To determine the effect of parallel venous augmentation on venous drainage, we used the Hagen-Poiseuille law of fluid dynamics, which models steady, laminar blood flow in noncompliant tubes:

where, F is the flow rate, ΔP is the pressure drop, and R is the resistance. The resistance experienced by blood travelling in a vessel can be approximated by:

where, η, is the blood viscosity (0.0035 Pa*s), l is the vessel length, and r is the radius of the vessel.[1] Furthermore, resistance in a branching vascular system can be simplified according to the following equations:

for n resistors in series and

for n resistors in parallel. To calculate the resistance in the venous system draining the flap before and after parallel venous augmentation, we used the vessel radii and lengths as indicated in [Fig. 2B] and [Fig. 2C], respectively. According to the Hagen-Poiseuille law, the addition of a parallel venous outflow tract resulted in a 10% decrease in the venous resistance, which corresponds to a 10% increase in venous flow for any given pressure gradient.

This case represents the first report of a combined ALT/TFL/RF free flap for near- total abdominal wall reconstruction.[2] [3] The number of microvascular venous anastomoses should be considered when transplanting large free flaps susceptible to venous congestion. Venous outflow can be improved when the flap's anatomical venous system is augmented with an additional parallel venous outflow tract.

• References

• 1 Rubino C, Ramakrishnan V, Figus A, Bulla A, Coscia V, Cavazzuti MA. Flap size/flow rate relationship in perforator flaps and its importance in DIEAP flap drainage. J Plast Reconstr Aesthet Surg 2009; 62 (12) 1666-1670
• 2 Wong CH, Lin CH, Fu B, Fang JF. Reconstruction of complex abdominal wall defects with free flaps: indications and clinical outcome. Plast Reconstr Surg 2009; 124 (2) 500-509
• 3 Sasaki K, Nozaki M, Nakazawa H, Kikuchi Y, Huang T. Reconstruction of a large abdominal wall defect using combined free tensor fasciae latae musculocutaneous flap and anterolateral thigh flap. Plast Reconstr Surg 1998; 102 (6) 2244-2252