Lateral Thigh and Anterolateral Thigh Free Tissue Transfer 

Updated: Sep 27, 2017
Author: Joseph L Leach, Jr, MD; Chief Editor: Arlen D Meyers, MD, MBA 

Overview

Background

Lateral thigh flap

The lateral thigh free flap is a fascial or fasciocutaneous flap based on the smaller vessels that extend from the profunda femoris system to the skin. These perforating vessels are typically numbered 1-4 in a superior to inferior direction. The flap is usually raised on the third perforator, although the second and the fourth are occasionally used. Since its first description, the flap has proven to be useful in many head and neck reconstructive situations.

  • The flap may be used for very large defects and requires no muscular sacrifice.

  • The lateral thigh flap is reliable, and it can be dissected easily while the head and neck ablative procedure is in progress. Use of the flap allows primary closure of the defect with minimal aesthetic deformity or functional impact.

  • The flap may potentially be split into 2 paddles based on separate perforators, or it can be de-epithelialized to create 2 separate skin islands on the same perforator.

  • A free fascial graft from the lateral thigh area is ideal for defects that require placement of bulk without lining. Performing a sensate flap is also possible.

Dissection of the vascular pedicle may be difficult because of anatomic variability. Proper positioning of the leg, use of suspended retractors, wide exposure, and sectioning of certain muscles from the femur are the keys to successful dissection. Although some variability in the vascularity is present, the vessels can be identified easily and preserved with proper surgical technique.

An image depicting a lateral thigh flap can be seen below.

Initial dissection involves suspension of a rake f Initial dissection involves suspension of a rake from a surgical stand to grasp the tough fascia overlying the vastus lateralis. As dissection proceeds medially, the short head of the biceps femoris falls inferiorly. The hemostat indicates the third perforating vessels.

Anterolateral thigh flap

The anterolateral thigh flap is a fasciocutaneous flap usually based on the musculocutaneous and septocutaneous perforators of the descending branch of the lateral circumflex femoral artery and its venae comitantes. This flap has gained acceptance in head and neck reconstruction because it has been proven to be a donor site with reliable vascularity, ease of harvest, and extreme versatility. The flap offers the advantages of being pliable with a large cutaneous territory, having a lengthy pedicle with good caliber vessels, possessing multiple components (adipofascial, muscle, fascia, and skin), being used as a sensate flap, and having the possibility of chimeric applications.

The descending branch of the lateral circumflex femoral artery is usually of sufficient caliber that a flap may even be based distally. As such, this flap has the ability to cover a variety of large cutaneous or mucosal defects. In special circumstances, it can be combined with other flaps (such as the fibula or iliac crest), using the "mosaic" principle to provide coverage of extremely large and challenging head and neck defects. In addition, the flap can easily be harvested using a 2-team approach without patient repositioning. The donor site can easily be closed primarily without functional deficit or significant conspicuous deformity. About 40% of the time, the donor site requires a skin graft. In elective situations, the graft may be avoided by pre-expanding the flap site for several months prior to flap elevation. Despite skin graft concerns, donor site morbidity is limited.

History of the Procedure

The lateral thigh flap was first described by Baek in 1983 as a fascial or fasciocutaneous flap based on the smaller vessels that extend from the profunda femoris system to the skin.[1] The anterolateral thigh flap, first described in 1984 by Song et al, is a fasciocutaneous flap usually based on the musculocutaneous and septocutaneous perforators of the descending branch of the lateral circumflex femoral artery and its venae comitantes.[2] Koshima et al and Kimata first described the use of this flap for reconstruction of head and neck defects.[3, 4]

Indications

Lateral thigh flap

The lateral thigh flap is indicated for large head and neck defects. This flap is quite versatile, especially for defects requiring large flap area or bulk. The flap can be used to reconstruct defects from the nasopharynx to the clavicle. For combined total laryngopharyngectomy, the flap is usually thin enough for total pharyngeal reconstruction, allowing reconstruction without laparotomy for jejunal transfer. For tongue reconstruction, folding the flap on itself and creating a planned tissue protrusion (ie, dog ear) can create bulk in the anterior oral cavity. This protruding skin and soft tissue mimics a neotongue tip. The extra bulk is particularly helpful at the base of the tongue area. The defects most commonly indicated for reconstruction with this type of flap are total glossectomy, total or partial pharyngeal defects, and base of tongue defects.

Although size limits for the flap have not been established, skin paddles as large as 16 x 30 cm have been described. Because of its large surface area, the flap provides excellent coverage of large cutaneous defects in the temple and scalp area; however, the tissue match is generally poor because of the pale color of the flap. The flap harvests no muscle, and primary closure of the donor site is usually possible. Split-thickness skin grafts are needed for donor site closure if the width is greater than 8-10 cm. The vessels are usually of good caliber and length.

Disadvantages to the free lateral thigh flap include variability of the thigh vasculature and the unfamiliarity of most head and neck surgeons with the thigh area.

The free fascial lateral thigh flap takes advantage of the abundant subcutaneous fatty tissue in the lateral thigh. Because of positioning considerations, this flap is easier to harvest than a scapular or parascapular flap. The fatty tissue in the lateral thigh provides a stable, vascularized, volume filler that will not atrophy or resorb over time. This type of flap is most useful in the parotid or temporal area.

The free radial forearm flap is an alternative for soft tissue reconstruction; however, it is probably better suited to smaller defects that require a thinner, more pliable flap. The forearm flap is also a good alternative for tubed pharyngeal reconstruction. Both flaps offer advantages to jejunal interposition grafts because neither flap requires laparotomy.

Anterolateral thigh flap

The anterolateral thigh flap is usually used for external defects of the head and neck and for oropharyngeal lining. Advantages of the anterolateral thigh flap include easy and safe elevation, minimal long-term donor site morbidity, a long pedicle with a wide arterial diameter, and a large amount of skin that can be used. The flap has good pliability and is of moderate thickness. The flap has been noted to be somewhat thicker in Caucasians than in Asian populations.

Results from a retrospective study by Xu et al supported the utility of free anterolateral thigh flaps in head and neck reconstruction. The study, which involved 872 patients with head and neck tumor-associated defects who underwent immediate reconstruction with these flaps, reported an overall reconstruction success rate of 97.4%.[5]

The flap is especially useful when forearm flaps are too thin or when the morbidity of harvesting a free forearm flap is too great. Flaps as small as 5 X 8 cm and as large as 22 X 32 cm have been used successfully. No major artery of the limb is sacrificed. It can be raised as either a single skin paddle for a 1-layer defect reconstruction or a double paddle for a 2-layer reconstruction. The flap may be designed to be fasciocutaneous, fascial, or musculocutaneous. Adipofascial flaps from the anterolateral thigh have been used successfully to treat hemifacial atrophy (Parry-Romberg syndrome).

The vastus lateralis muscle may be included in the flap when a muscular component is needed to cover exposed bone, skull base, artificial dura, osteosynthesis material, or open sinuses. A flap that includes ilium to form an osteomyocutaneous flap has also been reported. The vascular pedicle is approximately 10 cm long, and the artery is approximately 2 mm in diameter.

A study by Sarkar et al indicated that free thin anterolateral thigh flaps can be successfully used to repair burn contractures of the neck, with good functional and aesthetic results. In the study, 11 patients who underwent the procedure were followed up for an average of 5 years, with no significant early or delayed complications found (although two patients required reoperation for partial flap loss).[6]

Since the vessels in an anterolateral thigh flap are long and of good caliber, the flap may be used as a flow through flap. With this mosaic or "chimeric" principle, flaps can be combined with bone containing free flaps such as the fibula or iliac crest to replace skin, muscle, and bone in very large defects. The potential exists for making the flap sensate if the lateral femoral cutaneous nerve is included.[7] Performing the flap procedure under epidural anesthesia is possible in those patients not suitable for general anesthesia. Since the donor area is far from the head and neck region, the flap may be elevated simultaneously with tumor extirpation. The patient does not have to be repositioned. Donor defects smaller than 12 cm in width may generally be closed primarily.

When closing the donor site, a more important consideration than the absolute width of the flap may be the ratio of the flap width to thigh circumference.[8] If the flap width is less than 16% of the thigh circumference, the donor site may be closed primarily.

 

Relevant Anatomy

Lateral thigh flaps

Inferior to the inguinal ligament, the femoral artery branches into superficial and deep (profunda) branches. The adductor longus muscle acts as a partition between these 2 vessels. The superficial femoral artery courses anterior to the adductor longus, and the profunda courses lateral to that muscle. The profunda femoris artery (PFA) gives off several branches that nourish the posterior and lateral thigh musculature, after which they become cutaneous perforators, as shown below. The lateral thigh flap is based on 1 or more of these perforators.

Relationship of the perforating vessels of the lat Relationship of the perforating vessels of the lateral thigh to the femur is shown. Adductor longus separates the profunda femoris artery (PFA) from the superficial femoral artery.

The PFA passes distally between the adductor longus and adductor magnus. Typically, 4 perforating arteries are present, with the number of perforating arteries ranging from 2-6. After arising from the PFA, the perforators pierce the adductor magnus and enter the posterior compartment of the thigh. Each perforator has anastomotic branches that lead to other perforators, muscular branches, and cutaneous branches.

The first perforator provides the principle blood supply to the adductor magnus. The perforator pierces this muscle before it supplies other muscles or the skin overlying the iliotibial tract. After the PFA passes deep to the adductor longus, it gives off the second (usually the largest) perforator. The second perforator also contributes supply to most of the musculature of the posterolateral thigh.

The third perforator is the artery associated with the lateral thigh flap. It arises distal to the adductor brevis insertion on the linea aspera, supplying blood to the musculature in the area. After piercing the adductor magnus at the linea aspera, the third perforator travels as a septocutaneous artery between the vastus lateralis anteriorly and the long head of the biceps femoris posteriorly. This perforator may pass superior to or through the short head of the biceps femoris muscle. This vessel always passes anterior to the long head of the biceps femoris.

A wide variation in the position of the third perforator may exist, ranging from 8-32 cm superior to the lateral femoral condyle; however, the vessel is usually located within 2.5 cm of the midpoint of the thigh. If divided at the PFA, the pedicle of the flap is 6-8 cm long and 1.5-3 mm in diameter. The vein is slightly larger. If the 2 venae comitantes of the third perforator converge prior to entering the profunda femoris vein (PFV), a vein 3-5 mm in diameter is formed. Often, a Doppler ultrasonic device is used preoperatively to identify the third perforating vessel. This identification helps to prepare the surgeon for any anatomic variability.

The fourth perforator is the terminal branch of the PFA. This vessel arises approximately 7 cm above the knee, where it pierces the adductor magnus and the short head of the biceps femoris. Occasionally, the fourth perforator may be the dominant pedicle to the lateral thigh flap.

At the time of surgery, designating the vessel as a particular numbered perforator is difficult to do with accuracy because of the variations in location and size of vessels coupled with the inability to dissect the entire PFA. Despite these uncertainties, an adequate blood supply is present in 99% of thighs. Although the third perforator is usually designated as the vessel that arises distal to the adductor brevis, this muscle is difficult to visualize in a limited lateral surgical view. In clinical cases, regarding the second perforator as that vessel located near the insertion of the gluteus maximus and the iliotibial tract is generally safe. Any vessel distal to the second perforator has been called the third perforator. The terminal vessel that branches from the PFA is named the fourth perforator. Using this method, no more than a single third perforator can exist.

Regardless of what a vessel is called, the most important issue is finding a usable vessel somewhere along the long axis of the thigh. The surgeon must be prepared for the variations. The primary function of the intermuscular septal artery is to supply blood to neighboring muscles; thus, the blood flow to the muscles exceeds the supply going to the skin. The caliber of the branching vessels reflects this fact.

The lateral femoral cutaneous nerve innervates the flap. This nerve lies just above the fascia lata, after passing deep to the inguinal ligament near the anterior superior iliac spine. The nerve may arborize extensively before entering the flap; therefore, harvesting a wide cuff of subcutaneous tissue around the nerve is best.

Anterolateral thigh flaps

Anterior lateral thigh flaps are usually based on septocutaneous and musculocutaneous perforators of the descending branch of the lateral circumflex femoral system, although they may occasionally be based on the transverse branch of the lateral femoral circumflex artery in those occasional cases in which the descending branch is absent or small. The lateral circumflex femoral artery (LCFA) is a large branch off either the common femoral artery (25%) or profunda femoris artery (75%). Deep to the rectus femoris muscle, the LCFA divides into ascending, transverse, and descending branches. The descending branch, which is also known as the quadriceps artery, supplies the rectus femoris, the vastus lateralis, and the vastus intermedius muscles. See the image below.

Identifying the approximate course of the LCFA Identifying the approximate course of the LCFA

The course of the descending branch varies somewhat. It lies totally buried within the vastus lateralis muscle in 22% of individuals. It lies on top of the vastus lateralis in 12% and enters into the muscle more inferiorly in the remainder. In 6% of the population, the descending branch is absent. Routinely, 2 venae comitantes exist with the descending branch. Arterial diameter ranges from 0.2-3.5 mm, while the accompanying venae comitantes measure between 1.8 and 4.0 mm in diameter. Additional pedicle length may be obtained by ligating the transverse and rectus femoris branches.

Critical to the success of the flap is the dissection and preservation of at least 1 healthy perforator from the LCFA to the skin. Perforators pass in a septocutaneous (between rectus femoris and vastus lateralis) or musculocutaneous (through the vastus lateralis muscle) pattern. In 60% of individuals, musculocutaneous perforators exist, and in 40%, septocutaneous perforators exist. These perforators usually arise from the descending branch but may instead arise from the transverse branch. About 2% of the time, the surgeon may be not find a useful perforating artery and vein. In these cases, the other leg may be used as the donor site, or the flap may be converted to an anteromedial thigh flap.

Contraindications

Lateral thigh flaps

Local trauma and previous surgery to the thigh may be contraindications to use of this flap. The lateral thigh free flap is least useful in small defects or in cases in which lack of space may compress the flap. This flap is also contraindicated in patients who would not be candidates for any free flap. Patients who lack recipient vessels, who are poor risks for prolonged anesthesia, and who have impaired vascularity to the leg are not candidates for this type of surgery. Nevertheless, free tissue transfer has been performed successfully in patients who are elderly, in people who smoke heavily, in individuals with diabetes mellitus, and in patients who have had previous radiation to the neck.

In men, the flap may be hairy. Generally, a poor color match with the head and neck recipient site is common. If the patient is obese, a fasciocutaneous flap may not be possible. Lateral thigh flaps with large amounts of subcutaneous fat cannot be tubed adequately for laryngopharyngeal defects. The flap also cannot carry bone, but it can carry fascia.

Anterolateral thigh flaps

Contraindications to harvesting the anterolateral thigh flap include previous surgery or injury to the upper thigh compromising the pedicle. Morbid obesity may make the flap too thick and compromise the vascularity. As would be expected, the flap is usually hair bearing in males.

 

Workup

Laboratory Studies

See the list below:

  • Question the patient about any issues that may disqualify him or her from surgery.

  • Evaluate previous injury or surgery to the thigh.

  • Prepare the patient for a 1-2 week hospital stay with a suction drain in the thigh.

  • No specific lab studies or imaging studies, apart from those indicated for a prolonged procedure under a general anesthetic, are necessary for either thigh free flap.

  • Pinch testing determines the amount of fat in the donor and recipient and also in areas of the flap.

  • Because of an abundance of adipose tissue in the area, the lateral thigh flap is often twice as thick in females. The anterolateral thigh flap is generally less thick.

  • Using a Doppler device to locate the main perforating vessel in the lateral thigh is useful, although not critical. Doppler or color Doppler studies have also been used to identify perforators to the anterolateral thigh flap.

 

Treatment

Preoperative Details

Monitor and anesthetize the patient as indicated for a long procedure. For the lateral thigh flap, when the patient is positioned, secure the foot and leg in a padded stirrup, shown below. The knee is flexed and the leg rotated externally to expose the posterolateral aspect of the thigh. No tourniquet is used. The entire thigh is prepped and draped.

The leg is placed in a padded support. The knee is The leg is placed in a padded support. The knee is rotated inwardly to expose the posterolateral aspect of the thigh, including the intermuscular septum.

Anterolateral thigh flap

No special positioning is necessary for the anterolateral thigh flap. Angiographic and Doppler identification of perforating vessels may be helpful but is not critical to the success of the flap.[9] Multidetector row computed tomography has been found to indicate a sizable perforator with the shortest intramuscular course, which would lead to a shorter and safer operation.[10]

Intraoperative Details

Lateral thigh free flap

Palpate the vastus lateralis and biceps femoris muscles. The intermuscular septum between these muscles is where the perforating vessels are found. The fasciocutaneous flap is designed in an off-centered fusiform shape around the midpoint of the thigh. The vessel used for anastomosis is most commonly found within 2.5 cm of the midpoint of the thigh; thus, the midpoint is a useful landmark. Measuring the distance between the greater trochanter and the lateral femoral condyle and dividing this distance by 2 determines the midpoint.

  • Fasciocutaneous flap

    • Although the size of the flap is dictated by the needs of the head and neck defect, certain principles apply. Extend the superior margin of the flap to the border of the gluteus maximus to include the second perforator. Typically, a donor defect 8-10 cm wide is the maximum that can be closed without significant tension. Larger donor defects probably require a skin graft for closure.

    • Since the flap is thinner anteriorly, and the septocutaneous perforators predominately pass anteriorly over the iliotibial tract, most of the flap should lie over the iliotibial tract. This position accounts for the off-centered design of the flap. Two thirds of the flap width is designed to lie anterior to the intermuscular septum, with the remaining third lying posteriorly. A skin incision is made anteriorly, and the subcutaneous tissue is dissected from the iliotibial fascia itself as the skin and fat are retracted posteriorly. Bleeding is minimal in this plane.

    • The perforating vessels are identified and preserved in the flap fascia as the dissection is carried down to the intermuscular septum, as shown below. Care is taken to adhere to the iliotibial tract as the dissection proceeds in order to avoid damage to the vessels. The intermuscular septum is easy to enter inferiorly, but a bridge of fascia lata forms a roof over the septum superiorly. This bridge must be transected. At this point, the septum opens up widely. The long head of the biceps femoris falls posteriorly as the vastus is retracted anteriorly. Retraction of the vastus lateralis is best accomplished with 1 or 2 multiprong rakes that are suspended from a covered surgical stand, obviating the need for an additional assistant to retract. The rake or rakes are repositioned medially as the dissection proceeds proximally. See the image below.

      Initial dissection involves suspension of a rake f Initial dissection involves suspension of a rake from a surgical stand to grasp the tough fascia overlying the vastus lateralis. As dissection proceeds medially, the short head of the biceps femoris falls inferiorly. The hemostat indicates the third perforating vessels.
    • To visualize the second perforator, separating the gluteus maximus from the iliotibial tract may be necessary. The third perforator is traced as it passes superiorly through, or posterior to, the short head of the biceps femoris. The fourth perforator is usually continuous with the third perforator via the PFA or a communicating branch. The adductor magnus and the short head of the biceps femoris must be detached extensively from the femur at the linea aspera so that the PFA and branching vasculature may be revealed, as shown below. See the image below.

      Schematic view of the completed dissection shows t Schematic view of the completed dissection shows that the posterior skin incision has yet to be made. Harvest of the vessels usually is made where the PFA joins with the second perforator (not shown).
    • At the point where the third perforator pierces the adductor magnus, some difficulty may be encountered. At this point, a number of vessels branching from the main pedicle are often encountered passing anteriorly into the iliotibial tract and posteriorly into the adductor magnus and short head of the biceps femoris. These branches may be confused with the main pedicle; therefore, ligate and transect them so that the more proximal portion of the pedicle can be observed. In the distal pedicle, 2 venae comitantes usually surround the artery, but they often combine proximally into 1 vein just prior to entering the PFV. Since the artery and veins have a convoluted relationship at this point, a wiser approach is to complete the vessel separation with the microscope after pedicle division. This difficult separation is unnecessary if the PFA and PFV can be dissected sufficiently proximal to this confluence of vessels.

    • When the profunda vessels are dissected proximally and circumferentially, the vessels are transected just distal to the second perforator. Since the PFA is used in continuity with the third and fourth perforators, pedicle length and vessel diameter are improved. Occasionally, the flap must be based on the fourth or second perforators instead of the third. Usually, the fourth perforator is too small to use alone. After finishing the dissection, the vessels may be left intact, and the flap may be stapled back into place until it is needed.

    • After the vessels have been isolated, the posterior skin incision is made. Preserving the posterior skin attachment supports the flap, prevents excess traction on the vessels, and also preserves a secondary blood supply to the skin if the vessels are inadvertently transected too early. When the recipient bed is prepared, the vessels are clamped, transected, and suture ligated. The flap is then prepared for anastomosis and inset.

  • Fascial flap: The free lateral thigh fascial flap is elevated in much the same way as the fasciocutaneous flap. Since a skin paddle does not need to be designed, the flap is raised through a 16- to 24-cm incision lying over the intermuscular septum and centered over the midportion of the thigh. Anteriorly and posteriorly, fat is peeled from the undersurface of the skin, taking care to leave a 5-mm layer of adipose adherent to the dermis. Exposing bare dermis may cause necrosis of the overlying skin. The fat is then dissected from the vastus lateralis fascia, and the muscle is retracted as described above. The vessels are identified and traced in the usual fashion. The flap is harvested, and the incision is closed over a large suction drain.

  • Sensate flap: The nerve supply to the flap is derived from the lateral femoral cutaneous nerve. This nerve divides into anterior and posterior branches. The posterior branch enters the flap from its superior and anterior aspects in the subdermal fat. Since locating the nerve is difficult, the recommendation is to make a separate longitudinal incision over the sartorius muscle in the anteromedial thigh. All the intervening subcutaneous fat is harvested along with the nerve to the flap.

Anterolateral thigh free flap

See the list below:

  • Fasciocutaneous flap

    • A line is drawn from the anterior superior iliac spine to the superolateral border of the patella to approximate the anatomic position of the intermuscular septum between the rectus femoris and the vastus lateralis muscles. The perforating vessels of the flap can be identified with aid of Doppler probe within a 3-cm radius circle located at the midpoint of this line. The flap may be designed in such a way so as to be centered over the LCFA using a Doppler device.

    • The first incision is made medially, about 10 cm long and in a vertical direction over the rectus femoris muscle. The incision is deepened down through the subcutaneous fat and fascia. The fascia is dissected off the rectus femoris, and the thigh skin is raised and retracted laterally by subfascial dissection. At this point in the operation, one may visualize the LCFA in the intermuscular septum by retracting the rectus femoris muscle medially.

    • As discussed above, depending on the anatomy, either the transverse or descending branch of the lateral circumflex femoral is harvested. The surgeon should make two determinations at this point—whether to harvest the descending or transverse branch of the LCFA and whether septocutaneous or musculocutaneous perforators are present. If a large septocutaneous perforator is seen, the vastus lateralis muscle may be left alone. This perforator traverses the intermuscular septum between the rectus femoris and vastus lateralis muscles proximally. If more than one perforator is present, the most proximal one is the preferable choice for harvest because it has a relatively larger diameter.

    • More commonly, one will encounter musculocutaneous rather than septocutaneous perforators. The easiest way to preserve these vessels in the dissection is to include a cuff of vastus lateralis muscle with the main pedicle. This maneuver obviates the need to skeletonize specific perforators.

    • In roughly 2% of cases, no perforator is present.[11] One must then decide to either explore anteromedial thigh territory to look for perforators through the rectus femoris or sartorius muscles or to use the other leg.

    • After the main pedicle has been visualized through the medial incision, an incision is made laterally through the skin and fascia lata. The location of the lateral incision, of course, will depend on how wide the skin paddle needs to be for reconstructive purposes. Undermining is carried deep to the fascia lata laterally onto the vastus lateralis muscle. The musculocutaneous perforators are then elevated along with a 0.5- to 2.0-cm cuff of vastus lateralis muscle attached to the pedicle. Careful division and ligation of several muscular branches are important at this point. These vessels will frequently go into spasm, and the muscle may bleed excessively after revascularization.

    • After carefully dividing and ligating the remaining muscular branches to the rectus femoris and vastus lateralis muscles, the descending branch or transverse branch of the lateral circumflex femoral artery is then isolated. The motor branches of the femoral nerve that innervate the vastus lateralis muscle generally accompany the descending branch of the LCFA. It is no longer clear that these branches must be carefully preserved. In a large series of anterolateral free flaps, the nerve was transected in 22% of cases, and no postoperative sequelae were noted.[12] Depending on how large the flap is, the defect may be either closed primarily or skin grafted. Flap elevation generally takes about 60-90 minutes.

  • Fascial flap

    • In those situations requiring only soft tissue bulk and no epithelial lining, an anterolateral free fascial flap may be raised. This includes the vasculature, the subcutaneous fat, the fascia lata, and a portion of the aponeuroses of the rectus femoris and vastus lateralis muscles. This flap is raised via the medial skin incision only.

    • After the vessels are visualized and dissected out, the subcutaneous fat is peeled off the undersurface of the lateral thigh skin. As the skin is retracted laterally, a lateral incision is made through the fascia lata, and the dissection proceeds in the usual fashion. Both fascial and fasciocutaneous flaps have been used to restore soft tissue deficits in patients undergoing radical parotidectomy.[13]

    • Through the same donor incision, fascia lata has been harvested for simultaneous temporalis tendon transfer. Attached fascia lata has also been useful in recreating the mylohyoid sling in oral floor reconstruction[14] and nasal lining in complex nasal defects.[15]

  • Musculocutaneous flap: If greater amounts of bulk are needed, a larger cuff of vastus lateralis muscle may be incorporated with the anterolateral thigh flap.

  • Osteofasciocutaneous flap: The lateral femoral circumflex system may be used to incorporate not only the soft tissue of the anterolateral thigh but also the lateral iliac crest bone.[16] The bone is supplied by an ascending branch off the lateral femoral circumflex system. The mean length of bone harvested has been 7 cm.

  • Sensate flap: The anterolateral thigh flap may be made sensate by incorporating branches that derive from the lateral femoral cutaneous nerve. These branches enter the skin paddle from a superior lateral direction and must be dissected out in the subcutaneous tissue prior to incising the fascia lata.

  • Thinning the flap: Primary thinning may not be advisable in Western patients.[17] In these situations, thinning may interrupt the connection between subdermal and suprafascial vessels and cause necrosis of the skin, particularly peripherally.

Postoperative Details

Lateral thigh free flap

As with any free tissue transfer, take measures in the immediate postoperative period to monitor flap viability and maximize chances of flap success. Two closed suction drains are typically placed in the neck but distant to the anastomosis. Different practitioners use various special antithrombotic agents and different forms of postoperative monitoring. The free lateral thigh flap requires no specific modifications of these practices. The flap is monitored closely for signs of venous congestion or arterial insufficiency; the flap should be pale pink.

Infection, hematoma, and fistula are possibilities with procedures involving the upper aerodigestive tract. Take appropriate measures to monitor and treat the patient for these entities. Encourage the patient to walk within a few days of surgery. The drains are left in place until output falls to less than 30 mL per drain per day. Occasionally, a patient is sent home with the drains still in place. In other cases, a seroma may develop after the drains are removed, and the patient must return for serial aspirations of the seroma. Although the patient is initially sore at the donor site, no long-term limitations of function should exist. Normal leg motion is encouraged as soon as the patient is able to walk postoperatively.

When the flap is used to replace skin on the face, neck, or scalp, the paler skin of the thigh usually stands out in sharp contrast to the redder skin of the head, as seen below. The shape of the flap could change postoperatively, particularly when a planned tissue protrusion is performed to fashion a neotongue. Regardless of how well designed the flap is, these folds of skin always flatten significantly.

Appearance of a healthy flap is shown after anasto Appearance of a healthy flap is shown after anastomosis and inset. Note the pale color in comparison to the surrounding skin.

Anterolateral thigh free flap

Generally, no dressing is used over the donor site, although a drain is placed. The drain is removed after output falls below 30 mL per day and has turned a serosanguineous color. Antibiotic ointment is applied twice daily to the suture line. The patient is encouraged to walk by the third postoperative day.

When using the anterolateral thigh flap for restoration of tissue bulk, volume loss on the order of 8% has been noted after radiation therapy.[18] This would imply that some overcorrection at the reconstructive site is indicated if adjuvant radiotherapy is planned.

Complications

Lateral thigh free flap

Flap death is always a possibility with free tissue transfer. Nevertheless, success with the lateral thigh flap approaches 90-95%. At times, the PFA is unusable because of arteriosclerotic plaque. In these cases, the perforating artery may be used. Regardless, use of the PFA is generally preferable because of its large caliber and length. Greater vessel length is particularly important in positioning the flap for anastomosis in cases with large bulky flaps. If the vessels are accidentally transected during dissection but are long enough to be used for the flap, the posterior skin attachment may be left intact until the time of anastomosis. During this interval, the posterior subdermal and dermal vessels provide adequate blood flow to the skin flap.

Although the donor site is grafted with skin only on occasion, skin grafts may be lost because seromas have a tendency to develop in this area. To avoid this possibility, an anterior relaxing incision can be made, the thigh skin can be shifted posteriorly, and the skin of the secondary area can be grafted.

Anterolateral thigh free flap

As with other free flaps used in the head and neck, complications of fistula and complete or partial necrosis of the flap has been reported. Nevertheless, the flap viability rate has been reported as 97-100%. Complications at the donor site may include partial wound dehiscence, incomplete skin graft take and wound infection. Some patients may report postoperative numbness over the anterolateral thigh. Pain and weakness in the thigh may result if the deep fascia of the thigh is harvested along with the flap.

Partial necrosis of the foot and calf caused by the interruption of the descending branch of the lateral circumflex femoral artery has been reported.[19] In this patient, the flap vessel acted as a critical collateral for an obstructed superficial femoral artery. The authors recommend preoperative angiography of the donor leg in patients in whom a popliteal pulse is not palpable. If lower leg circulation is noted to be decreased after clamping the flap's pedicle, immediate intraoperative arterial reconstruction with a venous graft is recommended.

Outcome and Prognosis

Lateral thigh free flap

Bulk, large surface area, and pliability make the lateral thigh flap an attractive option in head and neck reconstruction. Donor site morbidity is minimal and usually consists of a linear scar and mild-to-moderate depression in the posterolateral aspect of the leg. Very large amounts of tissue may be replaced with this flap. Nevertheless, the lateral thigh free flap is not recommended for large lateral mandibular defects or for defects of the anterior mandibular arch.

Anterolateral thigh free flap

The anterolateral thigh free flap has been associated with minimal long-term donor site complications. Typically, patients are allowed to walk after 3 days. They may experience slightly more weakness climbing stairs, but this should not be bothersome or affect daily functioning. Even when the bulk of the vastus lateralis muscle is harvested, no significant decrease in strength or range of motion (when compared to the nonoperated leg) has been found.

Future and Controversies

Lateral thigh free flap

Some controversy exists as to whether the PFA itself or the third perforator is preferable to use for anastomosis. As discussed above, pedicle length is found to be too short when the third perforator is used instead of the PFA. Another debate involves the harvesting of the PFA proximal to the second perforator. Although the idea that dividing the PFA proximal to the second perforator may cause muscular weakness has been suggested, this result does not occur universally.

One report discusses a patient who had a large skin paddle (30 X 16 cm). The surgical approach involved harvesting the entire PFA proximal to the second perforator and using the second and third perforators; this was thought to give the flap the best chance for survival. The flap survived without incident, and the patient had no muscular sequelae.

Anterolateral thigh free flap

One controversy that involves the anterolateral thigh flap involves the preoperative identification of vessels. Part of the reason for the slow acceptance of the flap in the West has been the perception that the anatomy is unpredictable and dissection is difficult. Identification of a perforating vessel is problematic with a Doppler device because signals from the descending branch may be confused for a signal from a perforator. Some surgeons have advocated preoperative arteriography because of the variability of the vessel anatomy, while others feel this is unnecessary.

The acoustic Doppler has been demonstrated to not be as good as color Doppler in identifying perforators. The former has only a 40% concordance rate with anatomic dissection.[20]  A study by Lethaus et al reported that when anterolateral thigh flaps are being created, the precision and reliability of color Doppler ultrasonography surpasses those of a handheld Doppler device in identifying the anatomical position of the perforating arteries. With regard to locating the perforators, color Doppler ultrasonography was found to have a sensitivity and positive predictive value of 97.9% and 100%, respectively, compared with 90.5% and 80.4%, respectively, for the handheld Doppler device.[21]

Magnetic resonance arteriography (MRA) and conventional arteriography have their advantages and drawbacks. Unfortunately, MRA cannot reliably detect vessels less than 2 mm in diameter, and most thigh perforators fall into that category.

Intraoperative identification of perforators using an endoscope has been reported.[22] This has the potential of avoiding a long scar in those approximately 2% of patients that have no viable perforators.

As mentioned above, anterolateral thigh flaps may be combined with other free flaps using the chimeric or mosaic principle. This concept involves anastomosing the vessels of a second flap to a branch of the lateral circumflex femoral system. The technique is useful for large, complex wounds. The anterolateral thigh flap has been combined with fibula, radial forearm, iliac crest, groin, anteromedial thigh, and latissimus dorsi flaps. Because of its size, ease of harvest, vessel quality, and low donor site morbidity, the anterolateral thigh flap is aptly suited and has emerged the "workhorse" flap for soft tissue head and neck reconstruction.