The majority of thoracic reconstructions can be accomplished with one or a combination of the latissimus dorsi, pectoralis major, and omental flaps. Flaps have an independent blood supply and can be transposed into the defect. They fill dead spaces and allow a three-dimensional vascularized surface to deliver antibiotics, heal tissue, and help prevent direct cutaneous exposure of implanted biomaterials in the event of wound separation.
Latissimus Dorsi Muscle Flap
The latissimus dorsi muscle is the largest muscle in the body. It originates from the thoracic spine and thoracolumbar fascia to the iliac crest and inserts into the humerus (Fig. 138-1). Its major blood supply comes off the thoracodorsal system. The muscle can be accessed through a vertical, horizontal, or oblique incision or endoscopically.8 The skin and subcutaneous tissues are dissected off the muscle, and the muscle is then dissected off the chest wall. Large perforators off the paraspinous area and thoracolumbar area can be divided with clips or ties. The thoracodorsal pedicle is identified and preserved. The nerve can be left intact, divided, or crushed depending on the desired function of the muscle. For additional pedicle flap reach, the insertion to the humerus can be divided. If the insertion is divided, care must be taken to avoid tension on the pedicle. Suturing the tendinous insertion to the chest wall at a location that provides protection from tension to the pedicle should suffice and also will avoid rotational kinking that can occur if the flap is dissected to the point that it is only attached to the neurovascular bundle. This large muscle reaches nicely into the chest cavity after removing a portion of the second rib and easily covers the hilum. It also can easily reach the anterior mediastinum to cover the heart. With a skin paddle included with the tissue, it can be a useful flap for breast reconstruction or chest wall reconstruction. The distal portion of the flap can sometimes be unreliable because of vascular insufficiency, and caution therefore needs to be taken when the flap is used for defects that are distal to the costal margin. Although loss of latissimus dorsi function results in negligible functional deficit, a split-latissimus dorsi flap can be used to preserve some of its form and function. For many patients who have undergone a standard posterolateral thoracotomy, this muscle is divided and only the superior portion can be used based on the thoracodorsal blood system. The inferior portion can be used for lower thoracic defects based on perforators near the spine. Closure of this defect is generally accomplished with deep dissolvable sutures. Quilting sutures are preferred by many surgeons to reduce the size of the cavity, thus minimizing the risk of postoperative seroma, which has been reported to occur in 20% to 80% of patients.
Anatomical considerations for the latissimus dorsi muscle.
Pectoralis Major Muscle Flap
The pectoralis major muscle is the largest anterior chest muscle and can be very versatile in treating a variety of chest defects (Fig. 138-2A). Its primary blood supply is from the thoracoacrominal trunk. Access to the muscle can be made through an incision concealed in the inframammary fold. The skin and subcutaneous tissues are dissected off the muscle and the muscle is taken off the chest wall with electrocautery. The perforating vessels off the internal mammary artery are coagulated or ligated and the thoracoacromial trunk is identified and preserved (Fig. 138-2B). For additional length, the medial and lateral pectoral nerves as well as the insertion into the humerus can be divided. To cover the hilum, the muscle can be brought through a second rib resection anteriorly (Fig. 138-2C). For cervical esophageal reconstruction, overlying skin can be taken with the flap and fashioned into a tube. For anterior mediastinal reconstructions, the muscle can be transposed over the ribs and easily fills the superior portion of the anterior mediastinum. For lower defects, the muscle is often more efficiently transposed on the perforators from the internal mammary artery system. In this case, the thoracoacromial vascular pedicle and humeral insertion is divided and the muscle is “turned over” medially to fill the defect. As there is usually a perforator between each costal cartilage, it is possible to divide the muscle along its fibers and have multiple small segments of the muscle for filling complex defects of the anterior mediastinum. The pectoralis major muscle can also be split based on perforator anatomy to more accurately fill specific defects.
Pectoralis major muscle with (A) lateral pectoral nerve, (B) ligated mammary perforator, (C) second rib removed and muscle transposed into the chest.
The omentum is a large vascularized fatty structure in the abdominal cavity that originates from the greater curvature of the stomach and is adherent to and drapes over the transverse colon (Fig. 138-3). It connects to the spleen on the left side. Access to the omentum is most easily performed through a small upper midline incision, although it is possible to reach from the anterior mediastinum, through the diaphragm or to dissect it endoscopically. The first step in harvest is to release any abdominal adhesions to the omentum. Making counter incisions over previous scars, such as appendectomy incisions, can facilitate release. The omentum and transverse colon are then brought into view and the omentum meticulously dissected off the transverse colon, preserving both the vasculature to the colon (the transverse colonic mesentery) and the vasculature arcades of the omentum. After some dissection, the lesser sac is entered. Generally, the omentum is less stuck to the transverse colonic mesentery on the left side than the right, in most cases making it easier to start the dissection on the left side. Extensions to the spleen are divided with clamps and ties or with an advanced coagulation method.
For anterior mediastinal defects, this amount of dissection may be sufficient. If additional length is needed, it can be acquired from either the right or left gastroepiploic system. Each system should be assessed for patency before dividing any vessels to assure adequate flow to the omental flap. Each of the gastric perforators is individually ligated while checking the pulse within the gastroepiploic system. Once completed, this dissection gives the omentum several inches more of length, permitting a large segment of vascularized material to be placed virtually anywhere within the chest cavity. The omentum can be brought through an anterior defect in the diaphragm to reach anterior mediastinum and sternal debridement defects. Anterior chest wall defects with intact sternum usually require the pedicle of the omental flap to pass through a midline subxiphoid laparotomy defect. Closure of the abdominal cavity needs to be performed with care to make sure that there is no compression on the pedicle and to minimize the risk of herniation.
Initial care of complex reconstructions of the chest most reliably occurs in an intensive care setting by staff familiar with treating thoracic surgical patients. Invasive hemodynamic monitoring, ventilatory support, pleural drainage catheters, monitoring of fluids and renal function are essential to avoid morbidity and mortality. Pain relief using narcotics, nonsteroidal anti-inflammatory agents and regional epidural blocks can greatly aid patient recovery. Deep venous thrombosis prophylaxis is essential. For free tissue transfer operations, a monitoring system that is well understood in the hospital is essential for flap success. Even in the best centers, up to 5% of patients with free tissue transfer will need to return to the operating room for potential vascular thrombosis and revision of the microanastomosis. If discovered early, there is a high likelihood of correcting this problem.
Thoracic reconstruction allows treatment of large and complex defects. The combination of new technology such as advanced biomaterials, free tissue transfer, advanced wound care modalities, and vascularized tissue transfer have allowed these defects to routinely be treated with low morbidity and mortality. The complexity of these operations requires a team approach including a cardiac or thoracic surgeon, a plastic surgeon, and intensive care specialists to provide advanced life support measures in the postoperative period. Advances in plastic surgery including better understanding of anatomy, improved biomaterials, and tissue-engineered solutions will undoubtedly improve the ability to reconstruct these challenging defects in the future.