Anterolateral and Anteromedial Thigh Flaps

Introduction

In 1984, Song and colleagues introduced the anterolateral thigh flap based on septocutaneous branches of the descending branch of the lateral circumflex femoral artery. Since that time, the anterolateral thigh flap has gained popularity for use as a soft tissue flap for reconstruction of regional as well as distant defects. This flap can provide muscle, fascia, skin, or any of these in combination. Early anatomic dissections on cadavers noted that the vascular anatomy was variable and that the majority of skin vessels were septocutaneous compared with musculocutaneous in nature. More recent studies and series indicate the skin vessels are predominantly musculocutaneous perforators and less commonly septocutaneous vessels. In 1991, Zhou et al. evaluated their results of utilizing this flap for the reconstruction of defects in various regions of the body. In 1993, Koshima and colleagues reported on 22 cases of head and neck reconstruction utilizing this flap. This flap has been extensively reported in the literature and has become a workhorse flap for reconstruction of small or large defects, both simple and complex, with excellent results and minimal morbidity at the donor site.

Anterolateral Thigh Flap

The anterolateral thigh flap is relatively easy to harvest once the technique of perforator flap dissection has been learned. The ALT has a reliable blood supply despite some anatomic variability, it can provide a long pedicle with large-diameter vessels, and it is pliable and can be thinned to a significant degree without compromising blood supply. It can also be used as a flow-through flap, and, because of its unique position, allows for a two-team approach to the reconstruction of most defects in the body. The flap can also provide different tissue components such as muscle, fascia, and skin in a variety of combinations. The anterolateral thigh flap does have disadvantages such as a color mismatch when reconstructing facial defects, and the presence of hair in some patients. When large defects are reconstructed, skin grafts are required at the donor site. In rare instances, there is a lack of vessels with a reasonable size. The anteromedial thigh (AMT) flap has similar advantages and disadvantages to the ALT flap. The harvest of the AMT flap is simple and many of the same properties of tissues that can be included are similar. This flap is usually used when the anterolateral thigh flap vessels are inadequate or cannot be found.

Flap Anatomy (see Figs 59.1 , Fig 13.1 , Fig 13.2 , Fig 13.4 , Fig 13.19 )

Arterial Supply of the Flap ( Figs 59.1 , 13.1 , 13.2 and 13.4 )

The anterolateral thigh flap is supplied by either septocutaneous vessels or musculocutaneous perforators that usually arise from the descending branch of the LCFA. The flap is primarily based on musculocutaneous perforators vs septocutaneous ones (87% vs 13%). Less commonly, the perforators may originate from other sources such as the transverse branch of the LCFA.

Dominant:

branches of the descending branch of the LCFA

Length: 12 cm (range 8–16 cm)
Diameter: 2.1 mm (range 2–2.5 mm)

The descending branch of the LCFA courses obliquely along the intermuscular septum between the rectus femoris and vastus lateralis muscles. It exits in the majority of cases within a circle of 3 cm radius located at the midpoint of a line drawn between the anterior superior iliac spine and the superior lateral border of the patella as either a septocutaneous vessel or a musculocutaneous perforator, or both. Septocutaneous vessels run between the rectus femoris and vastus lateralis and traverse the fascia to supply the skin of the anterolateral thigh. At the exit point, musculocutaneous perforators traverse through the vastus lateralis muscle, giving off numerous intramuscular branches before piercing through the fascia and supplying the skin. In 30% of cases, the descending branch will divide into a medial and lateral branch, with the latter giving rise to the skin vessels.

In 2% of cases there may be an absence of any skin vessels, either septocutaneous or musculocutaneous, or the perforator may be too small in diameter, necessitating exploration more proximally to determine if perforators are originating from the transverse branch of the LCFA or if use of an alternative free flap is required. The artery may also course without the venae comitantes along its side and turn back at a more proximal point to join the course of the vein.

Minor:

perforator of transverse branch of LCFA

Length: 11 cm (range 9–13 cm)
Diameter: 2.1 mm (range 1.5–2.5 mm)

Less commonly, the septocutaneous vessel or musculocutaneous perforator arises from the transverse branch of the LCFA and runs parallel with the vastus lateralis muscle.

Venous Drainage of the Flap

Primary:

venae comitantes of the lateral circumflex femoral vessel and its branches

Length: 12 cm (range 8–16 cm)
Diameter: 2.3 mm (range 1.8–3.3 mm)

Two venae comitantes accompany the arterial pedicle of the anterolateral thigh flap. In rare instances, there may be no existing veins with the perforator pedicle.

Flap Innervation ( Figs 13.2 and 13.19 )

Sensory:

The anterolateral thigh flap may be harvested as a sensate flap by including the lateral femoral cutaneous nerve proximally with the flap and anastomosing it to a sensory nerve at the recipient site. The sensory nerve branches pierce the muscle fascia 10 cm below the inguinal ligament medial to the tensor fascia lata muscle. The nerve in that area splits into anterior and posterior branches to innervate the anterolateral aspect of the thigh (see Fig. 13.19 ).

Motor:

The vastus lateral is innervated by a branch of the posterior division of the femoral nerve. This branch accompanies the descending branch of the lateral femoral circumflex artery. This nerve can be included with flap harvest and anastomosed to a motor nerve at the recipient site for a functional reconstruction (see Fig. 13.2 ).

Flap Components

The anterolateral thigh flap can be harvested as a cutaneous flap consisting of skin and subcutaneous tissue based on either a septocutaneous vessel or musculocutaneous perforator. It may also be elevated as a composite flap, consisting of a fascial (fasciocutaneous anterolateral thigh flap) or muscular (vastus lateralis myocutaneous anterolateral thigh flap) component. Furthermore, the flap can be harvested as a combined flap to include various other tissues (including rectus femoris muscle, tensor fascia lata, anteromedial thigh skin or vastus lateralis on a separate perforator) based on blood supply from the descending branch or any other branches of the lateral femoral circumflex system. These chimeric flaps consist of multiple tissue combinations, each with an independent vascular supply. For example, a fasciocutaneous anterolateral thigh flap based on a musculocutaneous perforator may be harvested with the rectus femoris muscle that is based on an independent pedicle from the lateral circumflex femoral system and would be termed a chimeric fasciocutaneous anterolateral thigh myocutaneous perforator and rectus femoris muscle flap.

Advantages

Ease of harvest with relatively constant anatomy
Long length and large pedicle
Versatility in design with variable thickness and incorporation of various tissue components
Ability to provide sensory innervation
Lack of significant donor site morbidity
Decreased operative time with two-team approach.

Disadvantages

Color mismatch in some patients for facial reconstruction
Presence of hair in some male patients
Skin graft requirement at donor site if >8 cm or 9 cm width of harvested tissue.
Lack of vessels with reasonable size in rare cases.

Preoperative Preparation

Preoperative preparation includes functional evaluation of knee extension as the vastus lateralis muscle is a large component of quadriceps function. Patients with impairment in knee extension or with knee instability may have increased functional deficit after anterolateral thigh flap harvest and intramuscular dissection of the vastus lateralis. It is also important to note any previous scars that may affect flap design. Prior skin graft donor sites can be incorporated as part of the flap and would be visible as such at the recipient site.

The thickness of the thigh tissue should be assessed preoperatively. In obese patients, the flap may be very thick and may require primary thinning as well as subsequent debulking procedures in order to achieve a reasonable outcome. Male patients with thick hair may require laser hair removal or may need to shave the hair for certain types of reconstruction. Another option is to select a different donor site which is non-hair bearing. Flaps with hair are not ideal for reconstructions such as intraoral lining defects.

Patients with significant atherosclerotic disease affecting the arterial vasculature require preoperative evaluation using angiography. Previous injury or operations to the upper thigh require a work-up that will carefully assess the condition of the leg soft tissues and vasculature supplying the region of the proposed flap.

Flap Design

Anatomic Landmarks ( Fig. 59.2 )

Markings for the anterolateral thigh flap are based on the location of the skin vessels that supply the skin territory of the flap. Important landmarks for the flap include the anterior superior iliac spine (ASIS) and the superior lateral border of the patella. Taking into account that the perforators are located either at this line connection, the ASIS to the lateral patella (septocutaneous perforators), or posterior to this line (musculocutaneous perforators), the skin paddle is designed either centered over this line or the design can be shifted slightly posterior. A circle of 3 cm radius defines the area at which the skin vessels, either septocutaneous vessels or musculocutaneous perforators, exit. The skin vessels are often found in the inferior lateral quadrant of the circle. The most accurate method to design the flap is to mark the landmarks mentioned, Doppler the skin vessels, and design the flap based on the Dopplered skin vessels. The medial incision is made first, the perforators are found, and the flap is remarked.

Figure 59.2, Anatomic landmarks and flap marking.

General Thoughts About Flap Design

Although a large skin paddle up to 35 cm long and 25 cm wide can be harvested on a single dominant perforator, when possible, incorporation of two or more perforators will ensure greater success.

Limiting the width of the flap to 7–9 cm allows for primary closure of the donor site without the need for a skin graft.

It is not necessary to design the flap with the skin vessel at the center. An eccentric flap with the skin vessel entering at the proximal portion of the flap will allow for greater pedicle length. If the flap is to be pedicled in a reverse fashion for knee reconstruction, the skin island can be designed so that the skin perpetrator is at the distal end of the skin paddle. This will allow for further distal reach.

Aside from the variability in flap dimensions, the versatility of the anterolateral thigh flap in terms of tissue construct allows it to be tailored to the needs of the recipient site. In areas requiring a relatively thin flap, such as the foot and ankle, the anterolateral thigh flap can be elevated as a cutaneous flap as thin as 5 mm in thickness.

When extensive soft tissue coverage is needed, and muscle is believed to be necessary, the anterolateral thigh flap can be harvested with vastus lateralis muscle as a myocutaneous flap or rectus femoris muscle as a chimeric flap. Moreover, in recipient sites with a composite 3-dimensional defect, the anterolateral thigh flap can be designed with other tissue components based on separate perforators to more adequately cover the defect.

Sensate flaps can be constructed by including the lateral femoral cutaneous nerve in the proximal portion of the flap.

Special Considerations

Head and Neck Reconstruction

The anterolateral thigh flap can be harvested as a thin cutaneous perforator flap for defects that need minimal tissue bulk for coverage, as in tongue reconstruction. This can be done either by performing a suprafascial dissection or by thinning the flap after elevation. The flap may also be harvested with multiple skin islands, as needed in simultaneous reconstruction of oral lining and cheek skin, by potentially dividing the flap into two skin paddles based on separate perforators or de-epithelializing the flap to create two separate skin islands based on a single perforator.

Application of the anterolateral thigh flap for cervical or thoracic esophageal reconstruction has also been performed by tubing the flap at the donor site, then transferring to the defect for reconstruction. This can be performed in two operations to assure suture line healing after tubing the flap and prior to transfer. However, this is only indicated if the defect has not been created. In most cases, surgeons will tube the flap at the donor site and transfer in the same setting.

For pharyngoesophageal reconstruction, a flap is designed with a width of approximately 9 cm, to achieve a 3 cm diameter tube. A separate skin paddle based on a separate perforator can be used for monitoring of the flap. This is no longer commonly performed, as the flap can now be monitored using an implantable Doppler.

Abdominal Wall Reconstruction

Flap design for abdominal wall reconstruction is based on the size and location of the defect and the need for a fascial component at the recipient site. For lower abdominal wall and perineal defects, a pedicled fasciocutaneous anterolateral thigh flap with or without incorporation of the iliotibial tract or vastus lateralis muscle can be harvested with the pedicle pivot point approximately 7–10 cm below the ASIS, correlating with the origin of the lateral circumflex femoral artery. For large defects encompassing both the upper and lower abdomen, a free myocutaneous anterolateral thigh flap with a cuff of vastus lateralis along with the iliotibial tract or tensor fascia lata flap provides an effective reconstruction.

Upper Extremity Reconstruction

Most upper extremity defects require a relatively thin flap for coverage. A cutaneous anterolateral thigh flap can be harvested and trimmed to as little as 5 mm thickness to facilitate tendon coverage and filling of soft tissue defects. Alternatively, the anterolateral thigh flap can be elevated as an adipofascial flap for areas with adequate skin but lack of soft tissue.

Lower Extremity Reconstruction

Application for lower extremity reconstruction is based on the general flap design with variation in tissue construct tailored to the recipient site requirement. Certain areas such as the foot and ankle will require thin cutaneous flaps, while other areas will require more tissue bulk. In cases of trauma with vascular compromise, an anterolateral thigh flap can be designed as a flow-through flap to preserve the arterial vasculature at the recipient site. For defects closer in proximity such as the groin or knee, a pedicled flap can be elevated with the pedicle based proximally or distally, respectively. A distal pedicled flap is based on retrograde blood flow of the descending branch of the LCFA with the pivot point 3–10 cm above the knee. Longer pedicle length can be achieved by designing the flap more proximally on the upper thigh.

Breast Reconstruction

The anterolateral thigh flap may be used as an alternative tissue flap for breast reconstruction by creation of a fasciocutaneous flap with a small skin island and large underlying fat pad. Subdermal undermining posterior to the medial flap incision allows for the incorporation of a fat pad ranging in size from 10 × 12 cm to 14 × 22 cm. The donor site for this type of reconstruction is unfavorable.

Differences in Design, if Any, When Performing the Flap as Pedicled or Free

Although more commonly used as a free flap, the anterolateral thigh flap can be harvested and transferred as a pedicled flap to cover tissue defects in the groin, lower abdomen, perineum, and knee. The pedicled anterolateral thigh flap is elevated in the same manner as its free counterpart and with the same septocutaneous or musculocutaneous pedicle based on the descending branch of the LCFA. Flap boundaries are based on recipient defect requirements and can be designed eccentrically about a chosen skin vessel to obtain more length. The most proximal pivot point for a proximal pedicled flap is 7–10 cm below the ASIS and the pivot point for a distally-based pedicled flap ranges from 3 cm to 10 cm above the knee. For local thigh defects requiring minor rotation, a proximal pedicled flap need not be designed as an island flap and can instead, preserve a proximal skin pedicle to insure better venous outflow.

Flap Dimensions

Skin Island Dimensions

Length: 21 cm (range 4–35 cm)
Maximum to close primarily: 22 cm
Width: 8 cm (range 4–25 cm)
Maximum to close primarily: 8–9 cm (at the center of the thigh)
Thickness: 5 mm (range 3–20 mm)

These dimensions are highly dependent on the patient's body habitus and the skin tone and quality. The thickness of the flap is variable and primary and/or secondary thinning can be performed to achieve a thinness of 5 mm. Primary closure is more difficult in the proximal and distal aspect of the thigh.

Muscle Dimensions

Length: from 2 cm (cuff) to 20 cm (entire muscle)

The descending branch of the LCFA passes through the vastus lateralis muscle and a segment of muscle can be harvested based on one or more branches. Therefore, the size and location of the segment of muscle are variable and an extremely small segment or the entire muscle may be harvested with the flap. The tensor fascia lata muscle can be included if the ascending branch of the LCFA is included with the flap. The rectus femoris muscle or a portion of it can be harvested based on the branch from the descending branch of the LCFA.

Flap Markings

A line is marked connecting the ASIS with the lateral patella. The flap is marked over the Dopplered perforators. When a large flap is harvested, the medial incision is made, the flap is elevated in the subfascial or suprafascial plane until sizable perforators are located. The search for perforators is performed in a free style manner, which allows the surgeon to have the freedom to change the plan if anatomic variations are met ( Figs 59.2 , 59.3 ).

Figure 59.3, Marking of the anterolateral thigh flap.

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