Anterior Approaches to the Cervicothoracic Junction

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Chapter 20 Anterior Approaches to the Cervicothoracic Junction

Ung-Kyu Chang, Se-Hoon Kim, Daniel H. Kim

INTRODUCTION

The cervicothoracic junction is the vertebral region from C7 to T4, an area in which many pieces of critical vascular and visceral structures are encountered. Decompression of anterior lesions in the cervicothoracic junction is difficult in several viewpoints. The sternum blocks the surgical corridor and the operative field is deep because of thoracic kyphosis. The spinal canal is narrow, and the presence of great vessels acts as physical constraints.

A standard low cervical approach often can expose to the T1 level in most patients. In patients with long necks, it is possible to expose down to T2 with a standard low cervical approach. However, for usual anterior exposure of T2–4, more extensile approaches, such as the transmanubrial or trans-sternal approaches, will be necessary.

TRANSCLAVICULAR–TRANSMANUBRIAL APPROACH

Radiological studies of the upper thoracic spine have indicated that at least the T3 vertebra can be visualized in the majority of patients in whom a suprasternal approach is undertaken after the splitting and mobilization of the manubrium.¹

The external landmarks for level identification are T2–3 at the suprasternal notch and T4–5 at the sternal angle (Fig. 20-1). Before adopting this approach, it is important preoperatively to confirm the extent of the lesion and the position of the upper margin of the sternum on lateral radiographs. It also is essential to assess the affected spinal cord level and its relation to the level of the upper margin of the sternal manubrium because this relationship varies among individuals.

Fig. 20-1 In this patient, the sternomanubrial junction corresponds to the T2–3 intervertebral disc level.

SKIN INCISION

Linear vertical incision starts from the anterior border of the ipsilateral sternocleidomastoid muscle and is continued down to below the sternal angle.

MUSCLE INCISION

The platysma muscle is divided in line with the skin incision. Deep cervical fascia is incised. The sternal and clavicular heads of the sternocleidomastoid muscle are divided and retracted laterally. The sternohyoid and sternothyroid muscles are detached below the level of the clavicle and retracted medially. A blunt dissection is performed between carotid sheath and tracheoesophageal complex.

BONE REMOVAL

The medial third of the clavicle and manubrium is dissected periosteally. The clavicle is divided at the junction of the medial and middle thirds (Fig. 20-2). All procedures are safe when the periosteum is separated from the bone by using a raspatory. While excising the sternum, the sternum lining is carefully separated using the raspatory to avoid possible damage to the internal mammary artery (Fig. 20-3).²

Fig. 20-2 Extent of bone removal in the transmanubrial approach. Most of the manubrium is removed with the medial one-third of the clavicle.

Fig. 20-3 The internal mammary arteries run along the sternum.

The separation procedure is extended caudally to expose the level of the lesion, such as the upper thoracic spine. It is important to approach the vertebral body of the lower cervical spine and then extend the operative field to the caudal side. In such a case, no direct surgical procedure for the aortic arch and the great vessels is necessary. At some levels of the operative field, these great vessels may have to be retracted to the right or left, but directly separating them is unnecessary.

The left side of the manubrium can be removed piecemeal along its posterior periosteum.

Alternatively, the manubrium and sternoclavicular joint can be left intact and reflected with the sternal head of the sternocleidomastoid muscle (Fig. 20-4).

Fig. 20-4 The manubrium and sternoclavicular joint are left intact and reflected with the sternal head of the sternocleidomastoid muscle.

VASCULAR DISSECTION

Dissection is carried deeper until the great vessels are identified. Inferior thyroid vessels can be ligated. If the cranial part, approximately 50% of the sternal manubrium, is removed, the surgeons do not need to retract the left innominate vein. A bilateral retraction of the brachiocephalic trunk can expose the T1 and T2 vertebral body (Fig. 20-5).

Fig. 20-5 Great vessels around the sternomanubrial junction.

VERTEBRAL BODY EXPOSURE

After the great vessels, esophagus, and trachea are retracted, the prevertebral fascia is exposed. The prevertebral fascia is identified and incised to expose the vertebral bodies. The angle of the vertebral body is deepened to the caudal side. The T1 vertebral body is a little shallow and the T3 vertebral body is deep. The disc plane is so inclined to the anterior side that the cephalad screw should be angled more than 45 degrees for suitable fixation. Reconstruction of the clavicle and manubrium is optional but can be accomplished with wire or plating systems.

TRANS-STERNAL–TRANSTHORACIC APPROACH

This approach provides the best exposure down to T4, especially in obese patients, and it can be combined with the low cervical approach. The trans-sternal approach offers the best exposure of T3 and T4; however, it carries the greatest morbidity of all the anterior approaches. Caudally the aortic arch and its branches will limit access to the T3 and T4 vertebrae.

SKIN INCISION AND CERVICAL DISSECTION

The supine position is set with the neck hyperextended. A linear vertical incision starts from the mid-cervical spine along the anterior border of the sternocleidomastoid muscle and continues through the middle of the sternum down to the tip of the xiphoid process (Fig. 20-6).

Fig. 20-6 Skin incision for sternotomy; midline incision for sternotomy is connected with cervical oblique incision.

The platysma muscle and deep cervical fascia are incised. At the cervical level, the usual anterior dissection approach is made to reach the prevertebral fascia. The sternohyoid and sternothyroid muscles are divided from the undersurface of the sternum.

The sternohyoid muscle originates from the ventrocaudal hyoid bone to the dorsal surface of the manubrium and attaches to the sternoclavicular joint capsule. The sternothyroid muscle attaches along the dorsal midline of the manubrium (Fig. 20-7). The sternocleidomastoid muscle arises on the mastoid process and superior nuchal line and attaches to the manubrioclavicular joint. The nervous supply of these three muscles is from the accessory nerve. Their arterial supply branches from the superior thyroid artery.

Fig. 20-7 Muscles attached to the sternum; sternohyoid muscle and sternothyroid muscle are attached to the dorsal side of the sternum. Sternocleidomastoid muscle attaches to the ventral surface of the manubrioclavicular joint.

STERNOTOMY

The soft tissue aponeurosis investing the superior border of the sternal notch is released next. A blunt finger dissection is used to clear the underlying retrosternal adipose tissue and thymus remnants from the undersurface of the manubrium. The muscular aponeurotic soft tissue attachments to the inferior xiphoid process are released sharply, and retrosternal fatty tissue, underlying mediastinum, and pleura are separated bluntly from its undersurface and from that of the sternum in preparation for their division with a sternotomy saw.

The sternum is exposed subperiosteally and divided in the middle with a sternal saw. After the sternotomy, visceral fascia is seen to circumscribe the trachea and esophagus (Fig. 20-8). The visceral fascia continues down to the bronchi, where the fascia fuses with the parietal and visceral pleurae.

Fig. 20-8 After sternotomy, visceral fascia is seen to circumscribe the trachea and esophagus.

VASCULAR DISSECTION

In the superior mediastinum, the vascular compartment is not circumscribed by its own well-defined fascial sheath but is defined secondarily by independent surrounding fasciae: ventrally by the prevertebral fascial extension (the transthoracic fascia), caudally by the visceral fascia, laterally by the parietal pleura, and inferiorly by the pericardium.³

Inferior thyroid vessels can be ligated. For the exposure of prevertebral fascia, the esophagus, trachea, and brachiocephalic trunk are retracted gently to the right side, while the thoracic duct, the cupola of the pleura, and left common carotid artery are retracted to the left side and the left innominate vein is retracted caudally (or ligated if necessary) (Fig. 20-9). If the vertebral body mass protrudes to the ventral side, the bilateral carotid artery is displaced laterally and the mass is found to be between the common carotid arteries (Fig. 20-10).

Fig. 20-9 The inferior thyroid vessels are ligated.

Fig. 20-10 The relation between the tumor mass and both brachiocephalic vessels.

Venous structures lie on the arterial structures. The right brachiocephalic vein is formed just posterior to the medial end of the right clavicle and descends vertically into the superior mediastinum. 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. In the superior mediastinum, the left brachiocephalic vein runs obliquely from left inferior to right superior (see Fig. 20-5). Internal thoracic, thymic, and inferior thyroid veins in the superior mediastinum drain into the brachiocephalic vein. On the left, the superior intercostal vein, which drains the second and third intercostal spaces, also drains into the left brachiocephalic vein. 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. A second concave turn occurs as the arch curves around the anterolateral visceral compartment to reach the vertebral column.

The brachiocephalic artery is the first branch off the aortic arch and ascends vertically and slightly rightward to branch into the right common carotid and subclavian arteries posterior to the right sternoclavicular joint. The left common carotid artery arises next off the arch and ascends essentially vertically into the carotid sheath without branching in the superior mediastinum (Fig. 20-11).

Fig. 20-11 The left common carotid artery arises off the aortic arch with separate origin of the left subclavian artery.

The left subclavian artery is the third branch and ascends superiorly and leftward to curve around the thoracic inlet and into the axillary sheath without branches in the superior mediastinum (see Fig. 20-11). From the right brachiocephalic innominate artery, the right subclavian artery originates just from the medial side of the right claviculo-manubrial joint and runs under the clavicle (Fig. 20-12).

Fig. 20-12 Sagittal section showing the right brachiocephalic innominate artery and right subclavian artery.

The prevertebral fascia is identified and incised to expose the vertebral bodies (Fig. 20-13). Autonomic branches to the cardiopulmonary plexuses may be seen in this region and can be sacrificed if necessary. The left recurrent laryngeal nerve loops around the ligamentum arteriosum and ascends within the visceral fascia between the esophagus and trachea. Closure should be performed with standard wiring. A chest tube is not necessary unless there is pleural violation.

Fig. 20-13 Exposure of the vertebral body; the retractors are applied to four directions (left, cephalad; right, caudal).

CASE ILLUSTRATION

A 31-year-old woman presents with dysarthria and a cough that progressed to shortness of breath. She was neurologically intact.

Preoperative evaluation included simple radiography, magnetic resonance imaging (MRI), and computed tomography (CT) angiography. On x-ray, the vertebral body destruction was found at the C7–T1 levels. On MRI, the destructive lesion from the C7–T1 body grew into the superior mediastinal space and showed downward extension along the anterior surface of the upper thoracic spine (Fig. 20-14). On axial view, the mass displaced all the visceral and vascular structures (Fig. 20-15). Angiography was necessary because the vascular encasement should be excluded. The right side brachiocephalic innominate artery was displaced to the anterior side (Fig. 20-16). The left side brachiocephalic trunk was displaced to the left side (Fig. 20-17). The patency of the vessels was maintained and tumor-vessel interface seemed to be intact.

Fig. 20-14 Sagittal MRI. C7, T1 masses grow downward with ventral protrusion.

Fig. 20-15 Axial MRI. Ventral protruding mass displaces great vessels.

Fig. 20-16 Right carotid artery is displaced to the anterior side.

Fig. 20-17 The left carotid artery is displaced to the left side.

After the sternotomy opening, vascular structures were seen. The right brachiocephalic innominate artery was running underneath the left brachiocephalic vein (Fig. 20-18). With the caudal retraction of the left brachiocephalic vein, the T4 vertebral body could be reached. The right brachiocephalic artery and left common carotid artery were retracted bilaterally. A superior mediastinal mass was removed with forceps and a monopolar dissector. The superior mediastinal mass was removed piecemeal. The ventral body surface was exposed from the C6 to T4 vertebral body. Corpectomy was performed for the C7 and T1 vertebral body, and a vertebral body replacement (VBR) cage was inserted (Fig. 20-19). An anterior cervical plate was applied from C6 to T2. After the screw angle was adjusted with the consideration of the disc plane inclination, then posterior stabilization was performed with cervical lateral mass screws and thoracic pedicle screws (Fig. 20-20). Postoperative chest x-ray should be taken to ensure that pneumothorax does not develop (Fig. 20-21).