Sternotomy and Thoracotomy for Mediastinal Disease
Joseph LoCicero III
Mediastinoscopy and mediastinotomy are excellent incisions for diagnostic evaluation of the mediastinum. For tumor removal, larger incisions must be used. The two most common incisions for exposure of the mediastinum are median sternotomy and thoracotomy (see also Chapter 25).
Sternal Incisions
Mediastinal exposure for removal of tumors has been used since its description by Milton1 in 1897. He split the entire sternum in a procedure termed an osteoplastic anterior mediastinotomy. Sixty years later, Julian and coworkers2 popularized this incision for cardiac procedures. Today, the most common anterior approaches to the mediastinum are the median sternotomy, the manubrium-splitting sternotomy, and the sternum-splitting sternotomy. The most common thoracotomy incision for mediastinal exposure is bilateral thoracotomy with sternal transsection (clamshell) incision.
Rationale
Median sternotomy affords the most complete exposure to the anterior compartment and most of the visceral compartment of the mediastinum with the exception of the esophagus. Tumors of the anterior mediastinum are most effectively removed through this incision.
Thymectomy can be performed through a limited sternotomy. The complete sternotomy also provides excellent exposure for various vascular repairs and tracheal reconstruction or resection. For thymectomy, a small upper sternotomy may be appropriate. It affords a good cosmetic result when the mediastinal disease is benign and localized.
Becoming more popular is the bilateral thoracotomy with division of the sternum transversely to gain access to the mediastinum. This operation has acquired the euphemism clamshell incision. Bains and associates3 in 1994 demonstrated its usefulness for a variety of malignant diseases. Although usually done for bulky mediastinal tumors, Ris and colleagues4 employed it for mediastinal infections. However, it has gained most of its popularity as access for bilateral lung transplantation. It affords reasonably good exposure to both the right and left hilar structures.
Technique for Full Sternotomy
Several variations of the sternotomy incision are currently in use. Although the sternum is divided in the same manner, the skin incisions vary for special approaches for certain tumors or for cosmesis.
Skin Incision
In dividing the sternum, two skin incisions are possible (Fig. 170-1). The most common is the midline incision. This extends from the sternal notch inferiorly to a point just below the xiphoid. Some surgeons make the incision shorter at either or both ends to make it more acceptable cosmetically. Dissection, usually performed with the electrocautery, is carried through the subcutaneous tissue to the anterior sternal fascia. There is a space between the attachments of the pectoralis major muscles from right and left, leaving a muscle-free approach directly to the outer sternal table. Superiorly, the subcutaneous tissue is swept bluntly away from the sternal notch, exposing the sternal ligament. There is usually a bridging anterior jugular vein, which may be swept bluntly superiorly or divided if necessary. The sternal ligament is a broad-based ligament beginning at the posterior border of the manubrial notch. This is sharply divided to allow a finger to enter the mediastinum posterior to the sternum. Inferiorly, the incision is carried down over the linea alba, which is divided 1 or 2 cm beyond the xiphoid.
An alternative skin incision is the inframammary incision. This approach is almost always reserved for cosmetic purposes but may be necessary for providing the best closure after extensive tumor resection. It may be useful as well if the upper mediastinum has previously been irradiated. The incision is carried in a semicircular fashion underneath both breasts and connected to a semicircular incision over the sternum. Exposure to the sternum requires extensive mobilization bilaterally underneath the breasts. This is performed by extending the subcutaneous incision down to the prepectoral fascia and creating large flaps bilaterally. This is continued until the sternal notch is reached.
Sternal Incision
To split the sternum in the midline, the sternal notch and xiphoid are identified. At the angle of Louis, two straight
hemostats are placed next to the sternum to identify its midpoint. This is done because the pectoralis muscles do not always delineate the center of the sternum. The anterior table of the sternum is then marked by incising the periosteum with the electrocautery, connecting these three points. The xiphoid is then divided sharply with scissors. An oscillating sternal saw can then be used to divide the sternum from either above or below. This is performed with the lungs deflated (Fig. 170-2).
hemostats are placed next to the sternum to identify its midpoint. This is done because the pectoralis muscles do not always delineate the center of the sternum. The anterior table of the sternum is then marked by incising the periosteum with the electrocautery, connecting these three points. The xiphoid is then divided sharply with scissors. An oscillating sternal saw can then be used to divide the sternum from either above or below. This is performed with the lungs deflated (Fig. 170-2).
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