Melvyn S. Yeoh and Stavan Patel

Department of Oral and Maxillofacial Surgery, Louisiana State University Health Science Center, Shreveport, Louisiana, USA

A method of reconstructing soft tissue defects to various regions of the body. The anterior lateral thigh (ALT) perforator free flap has the ability to provide either individual components or any combination of skin, fascia, and muscle to reconstruct soft tissue defects of the head and neck region. The ALT flap can be harvested as cutaneous, fasciocutaneous, fascial, adipofacial, or musculocutaneous based on the vastus lateralis muscle (VLM) perforators, and a chimeric flap based on the ascending, transverse, and descending branches of the lateral circumflex femoral artery (LCFA) combined with the VLM, rectus femoris muscle (RFM), tensor fascia lata (TFL), and anteromedial thigh (AMT) skin paddle.

Indications

1. Reconstruction of soft tissue defects created by pathologic resection or traumatic avulsions involving the tongue, oral, maxillofacial, skull base, head, and neck regions
2. Desire for a two-team approach as flap harvest does not require patient repositioning for most oral, maxillofacial, and head and neck defects
3. Need for a large skin paddle for extensive reconstructions
4. Desire for a sensate flap
5. Reconstruction of combined hard and soft tissue defects when used as a flow-through flap in combination with a fibula osteocutaneous free flap for reconstruction of larger defects requiring extensive osseous and soft tissue reconstruction

Contraindications

1. History of previous traumatic injury to the upper thigh
2. Patients who have limited blood supply to the lower extremity (e.g., a history of vascular surgery [femoral-femoral bypass or aorto-femoral bypass])
3. Hypercoagulable conditions
4. Intramuscular dissection of the perforators is technically challenging and has a steep learning curve. Surgeons not well versed in ALT free flaps may elect for other reconstructive procedures
5. Severe obesity: Due to the large amount of subcutaneous fat in severely obese patients, it may be difficult to dissect the flap and close the donor site primarily. Due to its bulkiness, it is challenging to inset the flap without secondary thinning
6. Relative contraindication: Patients with claudication due to peripheral vascular disease and no palpable popliteal pulse
7. Relative contraindication: ALT skin is usually lighter in color and thicker when compared to tissues of the head and neck region. ALT free flaps may provide poor color and skin-thickness matches in certain instances

Anatomy

The musculocutaneous and septocutaneous perforators of the ALT free flap region are supplied by the descending branch of the LCFA, which is the largest branch of the profunda femoris artery. The region is drained by two venae comitantes of the lateral circumflex femoral system, which eventually drain into the femoral vein. Less commonly, other variations exist and the perforators of the ALT free flap may arise from the transverse branch of the LCFA, directly from the profunda femoris artery or the femoral artery.

The vascular pedicle to the ALT free flap lies in the muscular groove between the VLM and RFM. The vascular pedicle consists of the descending branch of the LCFA, two venae comitantes, and the motor nerve to the VLM, which is a branch of the posterior division of the femoral nerve. The neurovascular pedicle length has a range of 8–16 cm, with arterial and venous vessel diameter greater than 2 mm.

The descending branch of the LCFA gives several perforators to the skin of the ALT as it travels within the intermuscular space between the VLM and RFM. These perforators most commonly have a musculocutaneous course or, less commonly, a septocutaneous course.

The dominant perforator is generally located within a 3 cm radius circle at the midpoint between a line drawn from the anterior superior iliac spine (ASIS) to the superiolateral aspect of the patella. Typically, the perforator to the skin is found in the inferiolateral quadrant of this circle.

The lateral femoral cutaneous nerve provides sensory innervation to the skin in the ALT region and allows for its use as a sensate flap.

Preoperative Management

1. A thorough history and physical examination, appropriate laboratory studies, and a radiographic workup should be completed prior to surgery. Evaluation should include an estimation of the size of defect and the type of tissue required for its reconstruction (skin, fascia, muscle, bone, and nerves), the length of the vascular pedicle required, and the possible recipient vessel locations for anastomosis of the free tissue flap.
2. Preoperative evaluation for ALT free flap typically does not require angiography of the lower extremities, but it should include a physical examination of the thighs for previous surgery scars.
3. ALT free flap harvest is contraindicated in patients who have had previous vascular bypass procedures in the lower extremities. It is relatively contraindicated in patients who have claudication due to peripheral vascular disease and no palpable popliteal pulse. In this subset of patients, lower extremity angiography must be performed prior to planning an ALT free flap.
4. Due to the variable nature of the ALT skin perforators, patients should be consented for modification of the flap design and for flap harvest from the contralateral thigh.

Surgical Technique

1. The patient is positioned supine on the operating table with both legs in a neutral position.
2. Both legs are prepared circumferentially and in entirety from the hips to the lower legs and draped in a sterile fashion. This will allow for manipulation of the legs if the original flap design requires modification or if harvest from the contralateral thigh is necessary.

3. The anterior superior iliac spine (ASIS) and the superiolateral aspect of the patella are identified, and a straight line is drawn connecting these two points (Figure 61.3). The straight line denotes the intermuscular septum between the VLM and RFM.

4. The midpoint of this line is identified, and a 3 cm radius circle is drawn around this midpoint. The encircled area is where the most dominant skin perforator is usually encountered, commonly in the inferior-lateral quadrant of the circle.
5. Using a handheld Doppler probe, the skin perforators within the circled area are mapped and marked. Typically, 1–3 perforators are identified along the line, and the flap is centered over these vessels.
6. Depending on the size of the defect, flap dimensions are determined and marked on the thigh. Care is taken to center the flap on the identified skin perforators. Depending on the body habitus of the patient, a flap size of up to 35 cm × 25 cm can be harvested for the ALT region. Large flap harvests will require closure with a split-thickness skin graft (STSG) as primary closure will be unobtainable.
7. Most commonly, the ALT free flap is harvested as a fasciocutaneous flap. Dissection is initiated by making the skin incision on the medial border of the flap design, which is commonly located over the RFM. This allows for identification and preservation of the skin perforators.
8. The incision is carried through the subcutaneous fat and the deep fascia overlying the RFM. The incision is extended laterally within a subfascial plane until the intermuscular septum between the VLM and RFM is reached. During the lateral subfascial dissection, perforators to the skin are identified and preserved (Figure 61.4).
9. Upon lateral retraction of the flap, the perforators can be identified as either septocutaneous or musculocutaneous and are traced back to the descending branch of the LCFA, which lies within the intermuscular septum and can be visualized by gentle medial retraction of the RFM.
10. In cases where a septocutaneous perforator is identified, the perforator is used as a guide to trace and dissect back to the vascular pedicle deeper in the intermuscular septum.

11. In cases where a musculocutaneous perforator through the VLM is identified (Figure 61.5), it is necessary to map out its course through the muscle by gently unroofing the overlying muscle and tracing it back to the main vascular pedicle. The VLM over the perforator is dissected, lifted away, and incised. The posterior and lateral branches from the perforator to the muscle are ligated. Muscle dissection over the musculocutaneous perforator is achieved in a distal-to-proximal direction until the perforator is traced back to the descending branch of the LCFA (Figure 61.6). A small cuff (5–10 mm) of VLM can be left around the vessel to protect the perforating vessel. Muscle dissection should be executed under loupe magnification, using tenotomy scissors for dissection and hemoclips, bipolar electrocautery, or ultrasonic shears for hemostasis.

12. If a thinner, more pliable cutaneous perforator flap is required for the defect, the initial skin incision on the medial border of the flap design is carried through the subcutaneous fat until the deep fascia is reached. Further dissection of the skin paddle is extended laterally within a suprafascial plane until the marked skin perforator is identified. To avoid kinking of the cutaneous perforator, a small 2 cm radius cuff of deep fascia is maintained around the perforator and resected with the flap. To prevent necrosis of the cutaneous flap margins, a minimum tissue thickness of 5 mm should be maintained.
13. If no viable cutaneous perforators are identified by the medial skin incision, the ALT dissection can be converted to a TFL flap, an AMT flap, or a VLM only flap, or the medial thigh incision can be closed primarily and a contralateral thigh ALT free flap can be harvested.
14. Once the appropriate perforators are identified via the medial incision, another skin incision is made on the lateral border of the flap design. Lateral-to-medial dissection can be performed in a subfascial plane for f/>
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