Anterolateral Thigh Perforator Flap Harvest

Case description

The anterolateral thigh flap involves the skin paddle, the descending branch pedicle of the lateral circumflex femoral artery, and the perforators to the skin paddle.
The descending branch pedicle is situated between the rectus femoris and vastus lateralis muscle.
The major perforators to the skin paddle are normally located within a 2 to 3 cm radius from the midpoint between the anterior superior iliac spine and lateral border of the patella.
In this unique case, both myocutaneous and septocutaneous perforators are present. More commonly, only a myocutaneous perforator is found, which traverses the medial edge of the vastus lateralis muscle.
The vastus lateralis muscle is dissected to free the myocutaneous perforator. A small muscle cuff is left beneath the perforator to identify the orientation and prevent twisting and injury to the perforator.
The pedicle is divided distal to the perforators. On the proximal end, the pedicle is divided distal to the branch to the rectus femoris muscle, preserving the blood supply to this muscle.
The subfascial harvesting technique dissecting the plane below the fascia lata, taking the fascia with the flap. The fascia is carefully transected to maintain a safe distance of 2 to 3 cm to the perforators.
Care is taken to spare the motor branch of the femoral nerve to the vastus lateralis muscle during dissection.

Pearls

Exposure

The “ABC method” is another method used to identify perforators without the use of intraoperative Doppler. The main “B” perforator is identified according to the method described in the video. The “A” and “C” perforators are found 5cm proximal and distal to the “B” perforator¹.
In patients with muscle atrophy note that the rectus femoris muscle may be more medial than expected. Care should be taken during the initial incision to avoid inadvertently making the incision too lateral. It is often possible to palpate the rectus muscle.
Placement of medial incision is crucial; too medial will create a wide flap, too lateral will risk injuring perforators.

Perforator Dissection

The origin of the descending branch can vary. Depending on the study 75-100% of descending branches arises from the lateral circumflex femoral artery (LCFA). However, it can also arise at the origin of the LCFA, the profunda femoris, or from the common femoral artery^2-4.
The origin of perforators can vary as well. Perforators will usually arise from the descending branch but can arise from the ascending branch, the transverse branch, an oblique branch paralleling the descending branch, or rarely from the profunda femoris artery. In 1.8% of cases no perforator is identified^2,4.
13-21% of perforators are septocutaneous and pass between vastus lateralis and rectus femoris, 79-87% are musculocutaneous and travel through vastus lateralis^5,6.
Compared to Type B and C perforators, a higher proportion of Type A perforators are septocutaneous^1,2.
Perforators can also be identified using a suprafascial dissection above the tensor fascia lata. In these dissections the perforators can be sheared with traction on the skin. We generally prefer to do a subfascial elevation to identify the perforators. In certain reconstructions such as pharynx reconstruction harvesting the fascia with the flap is beneficial. In reconstructions where fascia is not required most of the fascia is able to be preserved with a small cuff of fascia taken around the perforator to prevent twisting. When the fascia is preserved it can be reapproximated in the area that it was preserved but left open in the area where the fascia was resected with the flap.
Musculocutaneous perforators will give branches to the vastus lateralis. These branches typically arise from posterior and lateral aspect of the perforator, and are rarely anterior⁵.

Descending Branch Dissection

Vastus lateralis branch of the posterior division of femoral nerve travels with the descending branch of lateral circumflex femoral artery and can be preserved.
The profunda femoris (or deep femoral) is the major deep arterial branch of the femoral artery that becomes the popliteal artery. The lateral circumflex femoral arises from the profunda femoris artery, although occasionally it may arise directly from the femoral artery. The profunda femoris or femoral artery are the limits of pedicle dissection.
The LCFA gives off three branches including the descending branch, which serves as the main pedicle.
Paired venae comitantes reliably travel alongside the arterial pedicle.

Closure

The maximum diameter that allows for primary closure is roughly 9cm, although the width that can be harvested ultimately depends on the leg skin laxity⁵. Pulley stitches can be used to create mechanical creep and help would closure.

Modifications

Sensate flap can be harvested by incorporating lateral femoral cutaneous nerve.
Chimeric flap can be designed by using multiple perforators. Two or more perforators are identified in 74% of patients².
Tubed flaps for pharyngeal reconstruction. A minimum width of 9cm to achieve a 3cm diameter tube. An extension of this is the “papillon” flap that includes a portion for external skin defects⁷.
Innervated vastus lateralis has been described for dynamic midface reanimation for radical parotidectomy defects⁸.
It may be possible to pivot to anteromedial thigh skin paddle if no lateral perforators are identified.

References