FIGURE 30.1 A line is drawn from the anterior superior iliac spine to the lateral aspect of the superior border of the patella. This line is bisected, and at this central point, a circle is drawn with 6-cm circumference. The skin paddle is designed to incorporate this circle, with the posterior–inferior quadrant most reliably harboring the cutaneous perforators. The skin paddle is then drawn to include sufficient skin for reconstruction of the defect while tapering the ends to facilitate closure of the donor site.

Determination of the appropriate size skin paddle is based on standard factors consistent with every pharyngoesophageal defect, as well as factors specific to the individual defect as assessed by the preoperative surgical plan. One of the main advantages of the ALT flap is that it provides the reconstructive surgeon with the ability to reconstruct total pharyngeal defects in tubed fashion as well as on-lay patch reconstruction of partial pharyngeal defects. Even if the preoperative assessment suggests that a significant (>2 cm) strip of posterior pharyngeal mucosa can be preserved, it is prudent to harvest a skin paddle of at least 9 cm in diameter. This is done in the event that assessment of the margins dictates sacrifice of the remaining posterior pharyngeal strip thought initially to be clear of tumor or if the remaining posterior pharyngeal strip appears to have insufficient vascularity to maintain a dual vertical suture line. Mucosal strips narrower than 2 cm will ultimately have two mucocutaneous suture lines running parallel to each other 1 cm or less apart, and the benefit of preserving this narrow strip in comparison to a single suture line in an appropriately vascularized cutaneous skin paddle is controversial. The mucosal strip is more frequently discarded in the previously irradiated patient as compared with nonirradiated mucosa. Even a narrow strip of mucosa is not discarded until the flap is determined to be well vascularized in the unlikely necessity of using an alternative reconstructive technique at the same operative setting.

If a pectoralis major myocutaneous (PMM) flap is chosen, then depending upon its thickness the preservation of this mucosal strip may have greater benefit. The 9-cm width is selected to ensure a neopharyngeal tube diameter of nearly 3 cm. A 9.4-cm wide skin paddle will create a 3-cm diameter tube when folded on itself, and this approximate width is also standardized between all patients. If a posterior strip of pharyngeal mucosa is successfully preserved, then the flap can be narrowed after harvest to avoid redundancy. The length of the skin paddle harvested is dependent on the location of perforators identified outside of the central circle and the need for additional skin for cervical skin reconstruction. A longer flap will allow for creation of an external skin paddle based either on a localizable skin perforator or by virtue of deepithelializing a portion of the skin paddle to enable the distal skin paddle to be folded and oriented externally. This may require horizontal rather than vertical flap inset (see Flap Inset). A horizontally inset flap will likely require a greater width to accommodate the vertical length of the defect and may not be suitable for defects including significant amounts of cervical esophagus.

Once the skin paddle is marked, the leg is circumferentially prepped and draped. The flap is harvested with loupe magnification (3.5×) in the subfascial plane. Incision is first made the length of the medial aspect of the skin paddle, subsequently incising the rectus femoris fascia on a line paralleling the skin incision (Fig. 30.2). A subfascial plane is elevated laterally to expose the intermuscular septum between rectus femoris and vastus lateralis. Regardless of the preincision localization of cutaneous perforators by Doppler probe, the elevation of the skin paddle off of the rectus femoris muscle is performed carefully to localize the cutaneous perforator(s) either within the intermuscular septum or traversing the vastus lateralis muscle. In either case, the rectus femoris muscle is widely exposed and then retracted medially to expose the primary vascular pedicle of the flap, the descending branch of the lateral circumflex femoral artery (LCFA). In this fashion, the cutaneous perforators will be localized along with the LCFA. The lateral aspect of the skin paddle is incised and elevated in a subfascial plane off of the vastus lateralis muscle and then dissection of the cutaneous perforators is performed. If these traverse the muscle, the muscle fibers anterior or medial to these perforators are elevated with a fine clamp and divided. An irrigating bipolar cautery allows for control of hemostasis with limited heat transfer to the delicate perforators. Larger muscular perforators are divided between small Ligaclips. This technique allows for elevation of the skin paddle with minimal additional bulk, a circumstance generally preferable for hypopharyngeal defect reconstruction, particularly if a tubed skin paddle is anticipated. Alternatively, a segment of vastus lateralis muscle may be harvested that incorporates a significant component of the muscle between the perforators or beyond if greater bulk is required or if vascular muscle for cervical vessel coverage is desired. This vascularized muscle may also be skin grafted for external coverage in carefully selected cases.

Microvascular Anastomoses

Donor vessels are selected in the neck based on availability. The ALT flap vascular pedicle is of sufficient length to support anastomoses either low or high in the neck and from the contralateral side for partial pharyngeal defects if necessary. The facial artery is used in the majority of cases mobilized to its takeoff from the external carotid artery. Transverse cervical vessels are usually available in the previously dissected neck when branches of the external carotid artery may be unavailable and represent an excellent alternative to the facial vessels. Most common venous anastomoses are to the facial vein, external jugular vein, internal jugular vein, and transverse cervical vein. Two venous anastomoses are often performed with both venae comitantes of the LCFA, although these two venae comitantes often join if dissected thoroughly, allowing for a single venous anastamosis in such cases.

Flap Inset

Flap inset is relatively straightforward where a significant posterior pharyngeal strip of mucosa has been preserved. If the vascular anastomoses have been performed with the facial vessels, the proximal aspect of the skin paddle is inset in the base of the tongue and tonsil region while the distal skin is inset at the esophageal inlet. The size and shape of the skin paddle is tailored to the specific defect size after flap revascularization both to avoid redundancy of the skin paddle and to ensure that all areas of the skin paddle utilized in the mucosal reconstruction bleed appropriately. Redundancy of the skin paddle is avoided to prevent a patulous neopharynx with outpouchings of nonmucous secreting surface area that in turn will contribute to decrease bolus transit time with swallowing or possibly trap and retain portions of the bolus. The unused cutaneous portions of the skin paddle are discarded or can alternatively be harvested for split-thickness skin graft if necessary for reconstruction of the external defect. Rather than discard the full thickness of any unused portion of the skin paddle, however, the excess skin paddle is deepithelialized to preserve the well-vascularized subcutaneous adipose tissue. This can then be used as a second layer to cover the adjacent suture lines. An alternative technique described by Yu et al. is to harvest an extra width of fascia with the skin paddle such that this can be used to bolster the suture line.

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