Anterior Approaches to the Cervicothoracic Junction

Overview

The anterior approach to the cervicothoracic spine can be technically challenging and requires precise knowledge of cervicothoracic regional anatomy and careful preoperative planning. A standard low-cervical approach can often expose to the T1 level in most patients, and in those with long necks, it is possible to expose down to T2 with a standard low-cervical approach. However, for usual anterior exposure of T2–T4, more extensive approaches, such as the transmanubrial or transsternal approaches, will be necessary. The transsternal approach offers the best exposure of T3 and T4, but it carries the greatest morbidity of all the anterior approaches. Caudally the aortic arch and its branches limit access to the T3 and T4 vertebrae.

Anatomy

Thoracic Inlet

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Superior mediastinum, defined anteriorly by the manubrium ( Fig. 26-1 )

Figure 26-1

Surgical approach depends on the desired level of exposure. The suprasternal notch approximates the T2–T3 level, and the sternal angle approximates the T4–T5 level.
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T2–T3 level at the suprasternal notch
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T4–T5 level at the sternal angle
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Sternohyoid muscle
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From the ventrocaudal hyoid bone to the dorsal surface of the manubrium
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Attaches to the sternoclavicular joint capsule
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Sternothyroid muscle
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Attaches along the dorsal midline of the manubrium
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Sternocleidomastoid muscle (SCM)
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Arises on the mastoid process and superior nuchal line and attaches to the manubrioclavicular joint
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Nervous supply is from the accessory nerve.
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Arterial supply branches from the superior thyroid artery.
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Removal of the manubrium and medial third of the clavicle reveals the pleural apices, which are covered by an extension of the transthoracic fascia, called Sibson’s fascia .

Vascular and Visceral Compartments of the Superior Mediastinum

Fascial Layers

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The visceral fascia circumscribes the trachea, esophagus, and thyroid gland, thus defining a visceral compartment.
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The carotid sheath circumscribes the carotid arterial system, internal jugular vein, and vagus nerve, thus defining a neurovascular compartment.
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These adjacent compartments create a potential space, the viscerocarotid space, which extends from the base of the skull to C7–T4, depending on the location of the fusion between the visceral and alar fascia.
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Blunt dissection of the viscerocarotid space exposes the alar fascia and the retropharyngeal space ( Fig. 26-2 ).

Figure 26-2

Dissection plane through the viscerocarotid space needed to reach the upper thoracic prevertebral space.
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The visceral compartment continues down to the bronchi, where the fascia fuses with the parietal and visceral pleura.
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The carotid sheath extends down to the subclavian vessels, where it fuses into the axillary sheath.
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In the superior mediastinum, the vascular compartment is not circumscribed by its own well-defined fascial sheath but is defined secondarily by independent surrounding fascia.
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The prevertebral fascial extension, the transthoracic fascia, lies ventral.
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The visceral fascia lies caudal.
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Lateral are the parietal pleura.
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The pericardium lies inferiorly.

Venous Structures

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Brachiocephalic veins with their branches descend from the neck into the superior mediastinum just posterior to the thymus gland.
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The right brachiocephalic vein is formed just posterior to the medial end of the right clavicle and descends vertically into the superior mediastinum.
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The left brachiocephalic vein is formed just posterior to the medial end of the left clavicle and descends diagonally to join the right brachiocephalic vein just posterior to the right first costal cartilage to form the superior vena cava.
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In the superior mediastinum, the left brachiocephalic vein runs obliquely from left inferior to right superior.
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Tributaries drain into the brachiocephalic veins.
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The vertebral and first, posterior, and intercostal veins in the neck are included.
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The internal thoracic, thymic, and inferior thyroid veins lie in the superior mediastinum.
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On the left, the superior intercostal vein, which drains the second and third intercostal spaces, also drains into the left brachiocephalic vein.

Arterial Structures

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The aortic arch initially ascends posteriorly to the superior vena cava but also turns diagonally posterior then inferior just anterior and to the left of the vertebral column.
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A second concave turn occurs as the arch curves around the anterolateral visceral compartment to reach the vertebral column.
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The brachiocephalic artery is the first branch off the aortic arch; it ascends vertically and slightly rightward to branch into the right common carotid and subclavian arteries posterior to the right sternoclavicular joint.
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The left common carotid artery arises next off the arch and ascends essentially vertically into the carotid sheath without branching in the superior mediastinum.
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The left subclavian artery is the third branch; it ascends superiorly and leftward to curve around the thoracic inlet and into the axillary sheath without branches in the superior mediastinum.

Retropharyngeal and Retromediastinal Spaces

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By incising the alar and mediastinal fascia, the median compartment of the retromediastinal space is entered.
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The prevertebral fascia covers the vertebral bodies and envelops the longus colli muscles.
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Autonomic branches to the cardiopulmonary plexi may be seen in this region and can be sacrificed if necessary.
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Structures that may cross the retropharyngeal and retromediastinal spaces:
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  The right recurrent laryngeal nerve can cross the retropharyngeal or retromediastinal space anywhere from C7 to T3.
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  The left recurrent laryngeal nerve loops around the ligamentum arteriosum and ascends within the visceral fascia between the esophagus and trachea.
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Lymphatics that terminate in the thoracic duct (on the left side):
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Run dorsal and to the left of the esophagus between the visceral and alar fascia in the superior mediastinum and ascend to the C7 level.
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  Lie laterally in a plane dorsal to the carotid sheath, then course caudally and ventrally to the branches of the thyrocervical trunk and phrenic nerve.
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  Terminate at the junction of the left internal jugular and subclavian veins.
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  A lymphatic trunk located on the right side follows a similar course to the thoracic duct.