Sternotomy
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Figure 1.1 Standard median sternotomy.
Identification and division at the middle of the sternum is the A and O. The
skin incision could be reduced to ca. 10 cm and still divide the sternum
completely.
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Step 1.
Operative Steps
◆ The
most essential consideration in performing a sternotomy is that it is done
through the midline. The suprasternal notch and xyphoid process are used as
landmarks. The latter sometimes has an asymmetric configuration and therefore
it is helpful to control the edge of the ribs on both sides to find the middle.
A paramedian sternotomy may be harmful to the sternum and is a significant risk
factor for sternum instability, which could lead to disturbances in wound
healing.
◆ The
patient is placed supine on the operating table. A linear incision is made from
just above the sternal angle to the level of the xiphoid process. Subcutaneous
fat and presternal fascia are divided, and the linea alba is divided inferiorly
about 2 to 3 cm to obtain adequate exposure of the pericardium (Fig. 1.1). It
is essential to divide the interclavicular ligament at the top of the
suprasternal notch using electrocautery. Special attention should be taken to
identify the veins crossing this area—the jugular venous arch. Injury of the
veins in this area could injure other important structures, such as the trachea
or brachiocephalic artery, if the bleeding is not controlled, especially if the
view is limited due to small incisions. There are also veins crossing the upper
part of the xyphoid cartilage, which should be identified and cauterized. The
midline of the sternum is marked by electrocautery. Scissors could be used to
divide the xyphoid process separately. The sternum is divided with a saw in a
caudocranial fashion, with close attention paid to staying on the midline. The
sternum could be also be divided in a craniocaudal fashion, changing the
direction of the saw blade.
◆ It
is prudent to ask the anesthesiologist to stop the mechanical ventilation to
avoid unnecessary opening of the pleura with the saw. The saw should be lifted
slightly against the posterior plate of the sternum, and care should be taken
to avoid injury to the pericardium, thymus, and innominate vein. If the
peritoneum is opened accidentally, it is important to close the peritoneum
expeditiously to avoid fluid incorporation and subsequent adhesion in the
peritoneum. Extension of the incision cranially facilitates exposure of the
arch and supraaortic vessels. On the other hand, the gastroepiploic artery
could be harvested, extending the incision into the peritoneal space.
◆ In
patients with previous cardiac procedures, extra attention must be paid not to
injure the cardiac structures, which could lead to hemorrhagic shock or an air
embolism, with lethal consequences. Careful blunt dissection may be performed
below the xyphoid process to free the pericardial and pleural adhesions. Gentle
elevation of the sternum with sharp hooks or unloading and establishing a
cardiopulmonary bypass (CPB) over the femoral vessels may be advisable in
select cases as a safeguard. In case of redo, computed tomography (CT) and
magnetic resonance imaging (MRI) are helpful imaging modalities to evaluate the
risk of reentry.
◆After
sternum division, hemostasis is obtained by cauterizing the periosteal surface
of the sternum. Bone wax may be used to seal the bone marrow and control
bleeding, although some surgeons prefer to simply apply a towel.
◆ In
redo cases, it is crucial to dissect the attachment to the edge of the sternum
before retracting because the retraction could injure structures, such as the
lung or innominate vein through tension.
◆ An
upper or lower partial sternotomy may be used for certain procedures, such as
isolated aortic or mitral valve repair or replacement or bypass surgery with
certain target vessels. The sternum could be divided into different patterns
through the third or fourth intercostal space - J shape, L shape, or inverted T
shape (Fig. 1.2). The fourth intercostal space usually enables a good exposure
of the aorta and root to be obtained. Access to the right atrium could be
limited, which makes direct insertion of the venous cannula into the appendage
of the right atrium laborious. It is important to have the option to cannulate
the femoral vein if exposure of the right atrium is not sufficient, especially
in the case of a smaller incision through the third intercostal space. Venting
through the pulmonary artery may be useful in select cases with limited access
to the upper right pulmonary vein.
◆ A
small incision has the advantage of reducing the wound area and preventing
wound infections due to sternum instability, reducing the requirement for a
blood transfusion, and shortening the stay in the intensive care unit. Small
incisions are also preferred by the patients for cosmetic reasons.
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Figure 1.2 A partial
sternotomy gives good exposure of the aortic root and could be selected to
reduce the incidence of sternum instability and wound infection.
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◆ At
the end of the procedure, chest drains are placed through separate stab
incisions at the epigastrium. Care must be taken so that the drain passes
through the fascia of the rectus muscle, avoiding the epigastric pedicle. If
necessary, chest drains for the pleura should be placed through the fifth or
sixth intercostal space or through a subcostal tunnel from a stab incision
below the costal arch.
◆ After
thorough hemostasis and placement of chest drains, the sternum is closed using
six to eight stainless steel wires. Consideration for ensuring the stability of
the manubrium is essential. The risk of cutting by wires could be reduced
through placement of the wires through the intercostal space. Care should be
taken to stay close to the edge to minimize the risk of injury to the internal
thoracic artery. Bands or plates could be used as an alternative to the wires
to stabilize a fragile sternum with osteoporosis, or a paramedian sternotomy
could be carried out in select cases.
◆ The
insertion sites of the wires are controlled for bleeding. The wires are tied
individually or by putting two together in a figure-of-eight fashion.
Reinforcement of the sternum edge is advisable in case of asymmetric division
of the sternum by placing an extralongitudinal wire at both sides of the
sternum to avoid cutting through the wire, as proposed by Robicsek et al.3
(Fig. 1.3). Wire tips are then buried in the presternal fascia. The linea alba
is closed using running or interrupted fascia closure sutures, and the
subcutaneous tissue is closed using absorbable sutures. Skin closure is
performed using subcuticular sutures or skin staples.
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Figure 1.3 Closure of the
sternum with additional bilateral longitudinal wires for reinforcement
introduced from Robiscek.
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Keywords : Cardiac Surgical Techniques,
Surgical Incisions, Basic Techniques, sternotomy, partial sternotomy, lateral
anterolateral thoracotomy, posterolateral thoracotomy, Thoracotomy, Approaches
in Thoracotomy, Thoracotomy Closure, Further Considerations
