With the development of reconstruction technology, various tracheal defect reconstruction methods have emerged. The main goal of tracheal reconstruction is still to restore completeness and maintain good respiratory efficiency. End-to-end anastomosis is suitable for reconstruction of a simple defect within 4 cm; otherwise, fistula and stenosis are likely to occur[13]. For large or complex tracheal defects, clinicians need to use certain tissues for reconstruction, and the tissues also provide protection for peripheral vasculature and nerves. Depending on the type of tracheal defect, these tissues not only need to properly provide good biomechanical properties but also need a higher survival rate and resistance to infection[4]. Axial flaps have a reliable blood supply, a high survival rate and strong anti-infection ability, so they are favored by clinicians. Depending on whether axial flaps are completely separated from the donor area, they can be divided into pedicled and free flaps, and all of them have advantages and disadvantages.
Using a free flap to reconstruct the defect, the vascular pedicle of the flap is anastomosed with the vessels in the recipient area. Compared with that of parotid, temporal, and hypopharynx defects, the reconstruction of tracheal defects is usually completed in a narrow space, so there are higher requirements for the freedom of tissue placement. Therefore, when there are blood vessels in the recipient area, free flaps may be suitable for tracheal reconstruction, which is also related to the length of the pedicle. Free radial forearm flaps, anterolateral thigh (ALT) flaps and posterior tibial artery perforator flaps have been successfully used for the reconstruction of tracheal defects[12, 14, 15], but they also have some disadvantages. ALT flaps are also ideal for head and neck reconstruction, as they are easy to harvest and provide rich tissue volumes and types. However, these flaps are relatively thick, so the value for tracheal reconstruction is limited. Although relevant techniques can thin these flaps, they have high requirements for surgeons[16]. Free radial forearm flaps with thin tissue is suitable for tracheal reconstruction, and posterior tibial artery perforator flaps were a suitable for tracheal reconstruction in our previous studies because of the thin, tough and hidden donor site. However, harvesting the flaps described above is complicated, and skin grafts are always required in the donor area. On the other hand, the application of free flaps to reconstruct tracheal defects generally increases the operation time and requires skillful surgeons and microsurgical techniques.In our study, most patients are older than 60 years old and suffer some omorbidities. Therefore,long-term surgery is unfavorable for them. In addition, some patients underwent neck surgery or I131 treatment previously, which may be a threat to the recipient vessels for free flaps.
Pedicled flaps are also classic for repairing head and neck defects; owing to the vascular pedicle, the freedom of position in pedicled flaps is not as good as that in free flaps. However, pedicled flaps usually have a stable blood supply and simple harvest process, and surgeons do not require microsurgical techniques. Pectoralis major myocutaneous flaps have always been favored for reconstruction because of their simple harvesting process and stable blood supply. Nonetheless, for tracheal defects, this type of flap is too bloated, and its influence on the appearance and function of the donor area may be unacceptable[17].
Pedicled TAAP flaps are thinner than pectoralis major myocutaneous flaps, and the influence of the donor area is lower. Secondly,compared with the neck flap (such as platysma transverse myocutaneous flap), TAAP blood vessels is not susceptible to the influence of neck dissection.Furthermore, compared with the ALT flap and posterior tibial artery perforator flap, the pedicled TAAP flap provides a hairless inner lining, which helps the patient feel comfortable.In addition,a pedicled TAAP flap can be made into a double-island flap while reconstructing tracheoesophageal fistulas. Last but not least, it takes a short time to harvest the flap, as the average time in our study was 17 min. This is especially suitable for elderly patients or other patients with poor tolerance to long-term surgery.
Of course, no flap is perfect, and the pedicled TAAP flap also has some disadvantages. First, its placement is limited by the vascular pedicle. Secondly, scars on the chest and possible nipple asymmetry affect the cosmetic effect. Moreover, the caliber of the pedicled TAAP flap is too small to be detected quickly and protected easily. Furthermore, numbness in the donor area can cause discomfort. Finally, we are still inexperienced in patients with rich adipose tissue in the chest, and the TAAP flap with rich adipose tissue may not be suitable for tracheal reconstruction owing to the difficult harvesting process and thickness.
There are some shortcomings in this study. The tracheal reconstruction by two-stage surgery seems to increase the complexity,but the closure of tracheal opening may be still needed after the one-time reconstruction, although this step is relatively simple.The difference of reconstruction strategy is limited in the assessment of the flap,but we will also use TAAP flaps for a one-time reconstruction of tracheal defects in the future. In addition,this study was completed in a retrospective manner, and the number of patients was relatively small. We intend to carry out a large number of prospective studies to better summarize the significance of pedicled TAAP flaps in tracheal reconstruction.