Anatomy of perforator vessels in ALT flap
8.1.2 Artery
The deep femoral artery is a branch of the femoral artery that travels down the thigh closed to the femur, running between the pectineus and the adductor longus. From the lateral site, soon after its origins, arises the lateral circumflex femoral artery (LCFA) that passes horizontally between femoral nerve branches and, more rarely, posterior to them. LCFA usually courses anterior to the femoral neck and behind the sartorius and rectus femoris muscles where it divides into ascending, transverse, and descending branches. The descending branch of LCFA runs downward on the vastus intermedius, behind the rectus femoris, and medial to vastus lateralis.
Along its course, it gives rise to intramuscular branches, the vastus lateralis and septocutaneous branches, and the intermuscular septum between rectus femoris and vastus lateralis. Perforating arteries from the intramuscular branches and septocutaneous arteries supply the overlying fascia and skin.
All these 3–5 ramifications, with an average diameter of 0.3 mm, form a rich network of vascularization in subcutaneous layers of the anterolateral thigh. The terminal long branch descending in the vastus lateralis ends in the superior lateral genicular artery which anastomoses with the femoropopliteal system.
8.1.3 Venous System
The anterolateral thigh has two systems of venous drainage: a superficial system composed of anterior femoro-cutaneous vein called anterior accessory saphenous vein and a deep system composed of two venae comitantes accompanying the perforator artery.
The anterior accessory saphenous vein commences at the distal portion of the lateral thigh and moves up in a constant location deep to the subcutaneous fat plane. It runs up to gain access to the great saphenous vein (GSV) or alternatively to the femoral vein just before that vein enters the saphenous opening.
Venae comitantes draining a series of smallest veins from a sort of subcutaneous net and from the vastus lateralis muscle give rise to the deep femoral vein that, together with femoral vein, are tributaries of the common femoral vein.
Deep systems are able to drain the blood from the skin of the thigh much more than the superficial system. Because of the poor connections between the venae comitantes and the superficial veins, only the deep system is used to drain the flap.
8.1.4 Nerves
The cutaneous innervation of the lateral thigh is derived from the lateral femoral cutaneous nerves. It is a nerve that originates from the lumbar plexus, specifically from the dorsal divisions of L2–L3; it emerges from the lateral border of the psoas major and crosses the iliacus muscle obliquely, toward the anterosuperior iliac spine. It reaches the lacuna musculorum passing under the inguinal ligament, into the thigh. It runs over the sartorius muscle where it divides into an anterior and a posterior branch. The anterior branch becomes superficial about 10 cm below the inguinal ligament and distributes branches to the anterior and lateral skin of the thigh. The posterior branch pierces the fascia lata and subdivides into filaments supplying the skin of the lateral and posterior surfaces of the thigh.
The cutaneous innervation of the anterior thigh is derived from the femoral nerve that provides also the innervation to the muscles that extend the knee. The femoral nerve splits into an anterior and a posterior branch under the inguinal ligament, into the thigh.
The anterior division of the femoral nerve gives off anterior cutaneous and muscular branches. The anterior cutaneous branches comprise the intermediate and medial femoral cutaneous nerve supplying the anterior and medial skin of the thigh. Muscular branches serve the pectineus and the sartorius muscles.
The posterior division of the femoral nerve provides innervation to the quadriceps femoris and the knee.
Muscular branches include the branch to the rectus femoris entering the upper part of the inner surface of the muscle; the branch to the vastus medialis descending lateral to the femoral vessels; the branches to the vastus intermedius, two or three in number, entering the anterior surface of the muscle about the middle of the thigh; and a large branch to the vastus lateralis accompanying the descending branch of LCFA and venae comitantes to the lower part of the muscle. It gives off a long slender articular filament to the knee that penetrates the capsule of the joint on its anterior aspect.
8.2 Analytical Factors and Technical Considerations
- 1.
The Location of the cutaneous perforators.
- (a)
Type A: Most proximal (perforator located 18.9 ± 3.5 cm from ASIS).
- (b)
Type B: Middle (perforator located 24.3 ± 5.4 cm from ASIS).
- (c)
Type C: Most distal (perforator located 28.7 ± 3.5 cm from ASIS).
- (a)
- 2.
The Origin of the Cutaneous Perforators.
- (a)
Type I (90% of the patients): It arises from the descending branch of the LCFA. In 90% of cases, there are musculocutaneous perforators through the medial portion of vastus lateralis muscle; in 10%, there are septocutaneous perforators. The musculocutaneous ones have a 2–3 cm course through the vastus lateralis muscle medial to the lateral course. For this reason, it is relatively easy to dissect.
- (b)
Type II (5–10%): In most of the cases, the perforators are musculocutaneous perforators that take a long intramuscular course through the vastus lateralis muscle. The superior-to-inferior-oriented intramuscular course can be up to 10 cm long, before they reach the thigh skin. Because of their long intramuscular course, type II musculocutaneous perforators are the most difficult to dissect.
- (c)
Type III (1–5%): Cutaneous perforators arise directly from the profunda femoris artery. In this type, the perforators are all intramuscular and have very small caliber unsuitable for microvascular anastomosis. The perforators located in the distal thigh provide a longer vascular pedicle than those that arise in the proximal thigh.
- (a)
Vascular variations
8.3 Flap Harvesting
8.3.1 Preoperative Management
The occurrence of acute vascular insufficiency when harvesting an anterolateral thigh free flap is exceedingly rare. There are no substantial differences in flaps harvested from the left or right side, although previous surgery, scars, injury, fractures, and burns may contraindicate the use of a specific thigh. When possible, it is preferable to have the operating thigh on the contralateral side to the resection in order to create more space for two surgical teams to work simultaneously. At least the patient’s preference is taken into account. At the admission, hospital personnel must be instructed to shave the chosen thigh.
The patient must be counseled about the evidence of the flap loss and about the donor site sequelae and, in particular, the visibility of the thigh scar with a possible poor cosmetic result, the possible use of a skin graft for the donor site closure, and the possibility of temporary or permanent variable sensory loss of the posterolateral portion of the thigh.
8.3.2 Patient Positioning
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
