INDICATIONS/CONTRAINDICATIONS

Resection and reconstruction of the sternum comprises a wide spectrum of surgical techniques applied to a range of clinical conditions. As methods have evolved for skeletal and soft tissue reconstruction, the ability to manage sternal pathology has greatly improved. The main conditions requiring sternal resection and reconstruction are infectious or neoplastic although radiation-induced necrosis of the anterior chest wall, as well as trauma, may also require surgical intervention.

Infection represents the most common indication for resection/reconstruction of the sternum. Sternal infections are typically a postoperative occurrence following median sternotomy for cardiac surgery although sternal osteomyelitis from IV drug use can also occur. Several patient- and surgically related factors predispose to postoperative sternal wound infections, including obesity, diabetes, recent tobacco use, urgent surgery, use of internal mammary arterial grafts (especially bilateral), and postoperative bleeding. Superficial sternal wound infections generally do not require surgical intervention and can be managed with IV antibiotics and local wound care. Deep sternal wound infections, however, require urgent surgical intervention to widely resect all infected and/or nonviable tissue. The extent of infection obviously dictates the degree of bony and soft tissue debridement, which in turn dictates the reconstructive technique. Partial sternectomy is preferred so long as the surgeon is able to debride to healthy, solid bone and soft tissue with bleeding margins. In the case of extensive sternal osteomyelitis with widely necrotic bone that is soft and/or oozing pus, a total sternectomy must be performed. The implantation of prosthetic material for skeletal reconstruction in the setting of active infection is contraindicated. Reconstructive techniques for sternal wound infections, therefore, rely on soft tissue coverage with muscle or myocutaneous flaps or omentum, typically done in collaboration with a plastic/reconstructive surgeon.

Sternal neoplasms are rare but represent another major indication for sternal resection/reconstruction. Primary sternal tumors, which are most commonly sarcomas (especially chondrosarcoma), are a clear indication for sternectomy and reconstruction because radical resection may permanently eradicate the tumor and improve long-term survival. The extent of resection follows oncologic principles. A 3- to 5-cm macroscopic margin is the goal. Depending on the extent of tumor invasion, the following sternal resections are indicated.

Total Sternectomy (sternal body, manubrium, medial 1/3 of clavicles): Large tumors involving the manubrium + sternal body, primary neuroendocrine tumors

Subtotal Sternectomy (sternal body with sparing of manubrium/clavicles): Tumors confined to the sternal body

Partial Sternectomy: Tumors limited to the manubrium or lower 1/3 of the sternal body

In cases where tumor invades deeper to involve underlying mediastinal structures, such as the pericardium or major vessels, the involved structures must be resected en block with the sternum, and appropriate reconstruction (e.g., caval reconstruction) performed.

The indication for resection of secondary sternal tumors (e.g., locally recurrent breast cancer, metastatic lung cancer, renal cell carcinoma) is more controversial given the poorer oncologic outcomes. In this setting, resection/reconstruction is often indicated for palliative purposes to relieve pain, inflammation, or bleeding related to the tumor.

Sternal reconstruction following oncologic resection takes a variety of forms, and there is some debate as to the proper approach. Because of the sternum’s important role in chest wall stability and respiratory mechanics, large bony defects that put a patient at risk for paradoxical chest wall motion (e.g., following total sternectomy) typically undergo rigid fixation with a prosthesis followed by soft tissue coverage using muscle or myocutaneous flaps. Small bony defects (i.e., <5 cm in greatest diameter), however, do not require skeletal reconstruction.

PREOPERATIVE PLANNING

Preoperative evaluation and management depend upon the surgical indication. Regardless of indication, the surgeon must be aware of any prior thoracic and/or cardiac procedures that will impact the surgical approach. This includes knowledge of prior internal mammary artery harvest for coronary artery bypass procedures, which will affect the choice of muscle flaps for reconstruction. In addition, it is critical to know the patient’s underlying cardiopulmonary status. Given that sternal resection can leave people with altered respiratory mechanics, it can be particularly morbid for those with pre-existing pulmonary disease.

For deep sternal wound infections, physical examination, standard blood work, wound cultures, blood cultures, and imaging are necessary. Clinical findings suggestive of sternal osteomyelitis include fevers/chills, wound drainage, and sternal instability upon palpation. Computed tomography (CT) is the most useful modality for assessing the extent of sternal infection. CT findings consistent with deep sternal wound infection include changes to bone configuration, fat stranding, and substernal fluid collection(s)/abscess(es). Importantly, after cardiac surgery the mediastinum will have standard postoperative changes that can make the radiographic assessment for infection more challenging. Plain films of the chest are of limited value but will show late bony findings consistent with osteomyelitis. Preoperative management should include prompt initiation of broad-spectrum IV antibiotics, as well as resuscitation in the setting of sepsis.

In patients with a sternal neoplasm, preoperative evaluation includes standard blood work and imaging. While CT is the most informative for assessing the tumor size and location, MRI can provide additional information about tumor invasion and involvement of underlying mediastinal structures. Bone scan or PET-CT is performed to rule out extrathoracic metastasis. Tissue biopsy should be obtained prior to definitive surgery to determine tumor type and grade. This is important given that sarcoma grade dictates management: Patients with high-grade tumors may require neoadjuvant therapy prior to operative resection.

SURGERY

Prior to surgery, the patient should receive standard prophylactic IV antibiotics within 1 hour of incision. For patients with deep sternal wound infections who are already receiving antibiotics, the surgeon must ensure with anesthesia that antibiotics are continued and dosed appropriately.

Positioning

The patient is placed in the supine position and is prepped and draped with sterile towels/sheets. If a single-stage procedure is planned with immediate sternal reconstruction the sterile field must be wide enough to accommodate flap preparation, including the abdomen if a rectus flap or omentum will be used.

Technique

Sternal Debridement for Infection

For deep sternal wound infections, the prior midline sternotomy incision is reopened and dissection is performed down to the sternum. Deep sternal wound cultures are obtained. A combination of cold dissection and electrocautery is used to completely debride the presternal soft tissue, until healthy, viable bleeding tissue surfaces are reached. The surgeon may have to extend the initial incision laterally on either side at the superior and/or inferior aspects of the midline incision in order to gain adequate exposure.

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