Anatomy and Surgical Exposure of the Vascular System

General Principles

Knowledge of vascular anatomy and surgical exposures are foundational components of vascular surgery. A detailed understanding of the location of blood vessels, surrounding structures, and the methods to obtain a safe and effective working space around a vessel are critical for any vascular operation. Careful preoperative planning of the approach to any vessel facilitates the performance of the actual operation. Proximal and distal control of vessels is as important as exposure of the actual operative field. On occasion, using a separate incision or exposure for control can be very helpful. As endovascular techniques mature and newer technology emerges, open exposure will remain an essential and basic skill. We will follow a systematic head-to-toe discussion of the anatomy and common exposures of the major blood vessels. Because the major veins usually run in close proximity to major arteries, we will focus on arterial exposures in this chapter for the most part.

Exposure of the Carotid Artery

The carotid artery is divided into three zones corresponding to the three zones of the neck described for penetrating neck trauma ( Fig. 4.1 ). The left common carotid artery originates directly off the aortic arch, and the right common carotid artery is a branch of the innominate artery. The exposure of the proximal common carotid arteries and other supra-aortic trunks within zone 1 is primarily through a thoracic incision and will be discussed in the exposure of the aortic arch.

The common carotid artery ascends through the neck without any branches within the carotid sheath, medial to the internal jugular vein and anterior to the vagus nerve, and bifurcates typically at the level of the fourth cervical vertebrae, 2.5 cm below the angle of the mandible, deep to the common facial vein as it enters the internal jugular vein. The bifurcation lies within the carotid triangle, which is bound by the anterior border of the sternocleidomastoid muscle (SCM) laterally, the posterior belly of the digastric muscle and stylohyoid muscle superiorly, and the superior belly of the omohyoid muscle inferiorly. The internal carotid artery is a direct continuation of the common carotid artery into the skull. Rising almost straight vertically from the bifurcation, it enters the skull through the carotid canal in the petrous portion of the temporal bone. The XII cranial nerve passes anteriorly from lateral to medial over the internal carotid artery within a few centimeters superior to the carotid bifurcation. As it passes over the artery, it gives off a small branch, the superior root of the ansa cervicalis.

An incision along the anterior border of the SCM allows access to almost the entire cervical carotid artery, with the cranial aspect of the incision angled behind the earlobe if access to the distal internal carotid artery is required. This incision is easily extended into a median sternotomy for access to the supra-aortic trunks in zone 1 of the neck. Alternatively, a transverse incision along a patient's skin crease can be made for better cosmetic outcomes. This incision typically is best for carotid bifurcation exposure and should be used with caution as more cephalic or caudal exposure through this incision is difficult. In transcervical, penetrating trauma, a transverse cervical collar incision extending to each side of the SCM may provide access to both sides of the neck, with posterior extension for more cephalad exposure.

Extending the neck slightly, using a shoulder roll and turning the head toward the contralateral side, facilitates exposure, but in trauma patients the cervical spine must be cleared before performing these maneuvers. The platysma is the first muscular layer, followed by the deep cervical fascia. The dissection is carried down along the anterior border of the SCM. The muscle is elevated away from the deep carotid sheath and retracted laterally. The common facial vein lies over the carotid bifurcation and should be ligated to expose the carotid arteries. The common carotid artery is isolated and controlled first. Avoiding excessive manipulation may prevent embolism. After the common carotid artery is encircled by a vessel loop, the internal carotid artery can be exposed lateral and deep to the external carotid artery. Retraction of the internal jugular vein facilitates exposure of the internal carotid artery as it lies anterior to the artery.

Cranial and somatic nerve injury is the most common neurologic complication of carotid endarterectomy with the potential of causing significant morbidity, with an incidence of injury ranging between 5% and 20%. Understanding the anatomy of the neck and relations to the carotid artery helps to understand the location and course of important cranial nerves, particularly cranial nerves IX, X, and XII, but also the mandibular branch of VII, and XI ( Table 4.1 ).

The most frequently injured cranial nerve is the hypoglossal nerve. The nerve courses between the internal carotid artery and internal jugular vein and travels anterior to the artery as it descends, about 2 cm above the carotid bifurcation. The descending branch of the hypoglossal nerve, also known as the ansa cervicalis, comes off the hypoglossal trunk and is typically anterior and parallel to the carotid arteries. It can be traced back to the hypoglossal trunk and can be helpful in identifying the hypoglossal nerve. The ansa cervicalis may be sacrificed, which will allow additional exposure of the distal internal carotid artery, with care taken to avoid excessive traction on the hypoglossal nerve. The hypoglossal nerve and its descending branch also travel along with the sternocleidomastoid artery and vein. This artery can be ligated to allow for additional hypoglossal nerve mobilization, but injury to the hypoglossal nerve must be avoided.

The recurrent laryngeal nerve is the second most commonly injured nerve. Originating within the mediastinum, the branch ascends into the neck and is typically away from the internal carotid artery; however, traction on the vagus nerve can result in injury. Rarely, the recurrent laryngeal nerve can arise off the vagus at the level of the carotid bifurcation as a nonrecurrent laryngeal nerve. This occurs more frequently on the right, with an incidence of 0.3% to 0.8%, and can be seen when dissecting medial or posterior to the carotid bulb.

The superior laryngeal nerve arises from the vagus near the distal internal carotid artery and courses posterior to the artery and descends obliquely with the superior thyroid artery, where it branches into an internal and external branch. It is subject to injury during carotid artery clamping.

The mandibular branch of the facial nerve descends from the parotid gland, deep to the platysma along the angle of the mandible. Its course may be variable, traveling more inferiorly, causing it to be prone to traction injury during exposure of the distal internal carotid artery.

The glossopharyngeal and spinal accessory nerves are structures in the cephalad portion of the neck that are prone to injury during retraction. The glossopharyngeal nerve courses in close proximity to the stylopharyngeus and stylohyoid muscles, and the spinal accessory nerve pierces the SCM and courses posteriorly to the trapezius muscle. The risk of injury to these nerves and the other cranial nerves increases as more maneuvers are performed to expose the distal internal carotid artery.

The greater auricular nerve, supplying the skin around the angle of the mandible and lower ear, courses high along the base of the skull, typically around the superior extent of a longitudinal incision, and the transverse cervical cutaneous nerves travel along the inferior aspect of the incision supplying the skin of the ipsilateral anterior neck.

Access to the internal jugular vein can be obtained with the same exposure of the carotid artery within the carotid sheath, except with gentle medial retraction of the carotid artery.

The external carotid artery courses medially and cephalad, behind the neck of the mandible, where it divides into multiple branches. For management of external carotid arterial injury, the external carotid artery may be ligated without consequence because of the rich collateral flow.

The exposure of the carotid artery becomes more complex as it rises to the skull base with many structures closely adjacent. Exposure of the distal internal carotid artery within zone III of the neck poses significant challenges for optimal visualization and for performing a safe distal anastomosis. Five steps can be performed to optimize exposure of the distal internal carotid artery ( Fig. 4.2 ).

The first step is to divide the arterial branches from the external carotid, often off the occipital branch of the artery, to the cephalad portion of the sternocleidomastoid. Any lymph nodes in this area can be carefully excised as well. Second, the ansa cervicalis can be divided and the hypoglossal nerve gently retracted medially and superiorly. Third, the posterior belly of the digastric muscle and the occipital branch of the external carotid artery can be divided. Fourth, the styloid process can be resected with a rongeur after division of the stylohyoid, styloglossus, and stylopharyngeus muscles, which insert onto the styloid process. This allows for an additional 0.5 cm of exposure. Extreme care must be taken during division and retraction as the hypoglossal and glossopharyngeal nerves both run deep to these muscles, the facial nerve crosses anterior to the styloid process, the spinal accessory nerve crosses posterior to the styloid process, and the spinal accessory nerve crosses posterior to the digastric muscle near its origin on the mastoid process. Mock and colleagues demonstrated in human cadavers that division of these structures can allow exposure of the internal carotid artery to the level of the first cervical vertebrae.

Lastly, anterior subluxation of the mandible with temporary intermaxillary fixation by intraoral wires and penetrating towel clamps on interdental Steinmann pin wiring would allow for an additional 1 to 2 cm of exposure to reach the base of the skull ( Figs. 4.3 and 4.4 ). These maneuvers require extensive interdisciplinary planning with an oromaxillofacial or plastic and reconstructive surgeon with nasotracheal intubation. It is important to differentiate mandibular subluxation with dislocation because, with dislocation, there is a higher risk for joint capsular or ligamentous injury.

The most aggressive but greatest exposure comes with the complete vertical mandibular ramus osteotomy with translocation or removal of the ramus segment with plated reimplantation.

Exposure of the Vertebral Artery

Exposure of the vertebral arteries is becoming less frequent with the increasing use of endovascular techniques in treating vertebral artery stenosis and hemorrhage. The vertebral arteries lie deep within the neck, coursing within the transverse processes of the cervical vertebra for much of their length. They arise from the first part of the subclavian artery bilaterally approximately at the level of the C6 or C7 vertebrae. The vertebral veins form a dense plexus adjacent to the artery as it enters the sixth transverse process and ascends the neck. On the left, the thoracic duct enters the subclavian vein between the internal jugular vein and vertebral vein and should be identified when exposing the proximal left vertebral artery.

The vertebral artery is divided into four segments ( Fig. 4.5 ). V1, the most proximal or ostial segment, extends from the origin of the artery off the subclavian artery to the C6 transverse foramen, anatomically marked by the convergence of the longitudinal longus colli muscle and anterior scalene muscle inserting on the C6 process tubercle. V2, the interosseous or transversary segment, travels through the anterior aspect of C6 transverse process foramen up to the axis (C2). V3 is the extracranial, suboccipital segment spanning from the artery's emergence from C2, through the atlas' transverse (C1) process to the base of the skull, where it penetrates the atlantooccipital membrane and dura. V4 is the intradural, intracranial segment of the artery to the convergence with the contralateral vertebral artery to form the basilar artery. It is noteworthy that in approximately 40% of patients the vertebral arteries are of different sizes. One artery may be dominant, while the other is minor or hypoplastic. In approximately 10% of cases the vertebral artery enters the cervical transverse foramen at a level higher than C6, in which the artery will course anterior to the longus colli muscle.

Careful preoperative planning based on computed tomographic or digitally subtracted angiographic imaging allows the surgeon to choose the exposure technique. Two approaches used to expose V1 are the transverse supraclavicular approach and the vertical anterior cervical approach.

In the supraclavicular approach, an 8-cm transverse incision is made 1 cm above the clavicle. The external jugular vein is ligated, and the clavicular head of the SCM is transected. The sternal head can usually be retracted medially but can be transected if necessary. The omohyoid muscle crosses the carotid sheath at this level and is divided to expose the carotid sheath. The sheath is opened vertically, the carotid artery is retracted medially, and the jugular vein, vagus nerve, and cervical sympathetic chain are retracted laterally with the sternal head of the SCM. Lateral to the carotid sheath lies the scalene fat pad containing the thoracic duct on the left side. It should be ligated as proximal to the subclavian vein as possible to void injuries that can cause a leak postoperatively. Deep to the fat pad on the anterior aspect of the anterior scalene muscle is the phrenic nerve running superior-laterally to inferior-medially. The inferior thyroid artery crosses diagonally over the vertebral artery at V1. On the medial side, the prevertebral aponeurosis over the longus colli muscle is incised, exposing the sympathetic chain that should be protected. At this point, an inverted V can be seen created by the longus colli muscle medially, the anterior scalene muscle and phrenic nerve laterally, and the apex pointing to the vertebral artery. Arising lateral to the vertebral artery is the second branch of the subclavian artery, the thyrocervical trunk, which can be differentiated from the vertebral artery by its multiple branches. The inferior thyroid artery and vertebral veins are then ligated, and the dissection can be carried cephalad to the C6 transverse process and caudal to the subclavian artery to fully expose the V1 segment. The longus colli muscle can be cut along the lateral aspect of the vertebral body to expose the foramen. The transverse approach allows for a faster but more limited exposure, whereas the cervical approach is useful for extended exposure of other segments at the expense of a more difficult and time-consuming dissection.

The vertical anterior cervical approach uses the same incision as a longitudinal incision for a carotid endarterectomy. The SCM is retracted laterally, the omohyoid muscle divided, and the carotid sheath with its contents retracted medially and the scalene fat pad retracted laterally with the phrenic nerve. Similarly, the inferior thyroid artery and vertebral veins are ligated, and dissection is carried in both directions for complete exposure. This approach is useful if the distal vertebral artery may need to be exposed, as in a common carotid-vertebral artery bypass or vertebral artery transposition.

Exposure of the V2 segment begins similarly to the anterior cervical exposure of V1 with extension of the incision cephalad to the mastoid process, angling posteriorly toward the ear. With the SCM retracted laterally, the carotid sheath and pharynx are retracted as medially as possible to expose the prevertebral fascia. This fascia is vertically incised medial to the sympathetic chain, and the fascia is retracted laterally to maintain the branches from the chain to the nerve roots posterolaterally. Again, the distal exposure of V1 exposes the longus colli and anterior scalene muscles converging to the C6 anterior tubercle of the transverse process. The anterior longitudinal ligament is incised vertically against the vertebral column and swept off with a periosteal elevator en bloc with the longus colli and longus capitus muscles. Bleeding may be encountered here with the extensive venous plexus that runs with the vertebral artery, and dissection lateral or posterior to the anterior transverse process tubercle risks injury to the cervical nerve roots as they emerge. Using a small rongeur, the anterior arch of the transverse process can be removed to open the bony canal, exposing the vertebral artery. At the level of C3, the vertebral artery begins to course laterally as the C2 transverse foramen is more lateral than the rest. At this level, dissection over the anterolateral aspect of the vertebral body is preferred to visualize and feel the angle of C2 safely.

The V3 segment has a more intricate course between C2 and the skull base. C1 and C2 are the most mobile vertebrae of the entire spine and have the most intervertebral space. At this level, the vertebral artery contains redundant length as it traverses from the atlas to the foramen magnum at the base of the skull. It takes a sharp posterior turn after emerging from the atlas foramen, travels in a posterior groove, and then turns anterior to penetrate through the atlantooccipital ligament and dura within the foramen magnum. During this course, multiple small branches are given off that create collaterals with the external carotid artery and supply the cervical vertebrae and meninges.

The most commonly described approach is the anterolateral approach, which begins again similar to the exposure of V1 and V2 with a longitudinal incisional along the medial border of the SCM, extending posteriorly toward the mastoid process behind the ear. The carotid sheath structures are retracted medially. The SCM can be completely transected, partially transected, or preserved, with care taken to preserve the spinal accessory nerve that enters the muscle within a few centimeters of its insertion point on the mastoid process. The splenius capitis and longissimus capitis muscles are also transected off the mastoid process with a 5- to 10-mm cuff for reattachment. This exposes the levator scapulae and splenius cervicis muscles that can be detached from the C1 transverse process to expose the vertebral artery between C1 and C2.

Exposure of the V3 segment to the base of the skull and V4 segment is best accomplished through the suboccipital approach described extensively by Berguer. The patient is positioned in the prone, “park bench” position in which the head is tilted and resting over an extended contralateral forearm. The incision is curvilinear, transverse from the posterior midline to the mastoid process and extending downward along the posterior border of the SCM. From superficial to deep, the following structures are sequentially identified and divided: the medial trapezius toward its insertion, the semispinalis capitis, the splenius capitis, the longissimus capitis, and SCMs. The spinal accessory nerve is exposed by the division and reflection of the sternocleidomastoid. The transverse process of C1 is palpated. Lastly, the obliquus capitis superior muscle and the lateral half of the rectus capitus posterior major muscle are cut to fully expose the base of the skull. The vertebral artery surrounded by its venous plexus is then visible. Berguer describes a technique to ligate these bridging veins by using an 8-0 Prolene suture passed on the needle backward. Bipolar cautery can also be used. Upon completion, the splenius capitis and semispinalis muscles are reapproximated and the SCM reinserted.

Exposure of the Aortic Arch

Exposure of the aortic arch can be achieved through two primary approaches: a median sternotomy for the ascending aorta, the brachiocephalic artery, the proximal right subclavian artery, and the right and left common carotid arteries ( Fig. 4.6 ). The most accepted approach to the proximal left subclavian artery is with a left anterolateral thoracotomy. Both of these exposures may require supraclavicular extension or counterincisions, which will be described in this section. The ultimate goal is to allow for proximal and distal control with maximal visualization and working space and minimal morbidity ( Fig. 4.7 ).

Exposure of the Brachiocephalic Artery

Exposure of the first two trunks of the aortic arch begins with a median sternotomy. There must be coordination with the anesthesia team to deflate the lungs to avoid injury to the pleural space or lung parenchyma during the division of the sternum. A well-placed sternal retractor provides wide access to the anterior mediastinum. The first structure encountered is the thymus gland, which should be divided vertically in the midline, ligating its blood supply coming from the internal thoracic arteries and draining into the brachiocephalic and internal thoracic veins. The internal jugular veins course anteriorly to the subclavian arteries and are joined by the subclavian veins to form the brachiocephalic veins. The left brachiocephalic vein courses obliquely across the midline anterior to the aortic arch to unite with the right brachiocephalic vein around the level of the first sternocostal joint. The internal thyroid and thymic veins drain into the left brachiocephalic vein and should be ligated to provide wide mobilization of the venous trunk to retract it superiorly. The left brachiocephalic trunk can be ligated in instances necessitating urgent proximal control of the innominate artery. Once the left brachiocephalic vein has been retracted superiorly or ligated and divided, the aortic arch can now be visualized ( Fig. 4.8 ). If access to the ascending aortic arch is required, the pericardial sac is opened.

The apex of the aortic arch runs obliquely from the right anterior aspect of the mediastinum to the left posterior aspect. As a result, the brachiocephalic artery is the anterior-most aortic branch, followed by the left common carotid, with the left subclavian artery posterior. Therefore the proximal left subclavian artery has very limited exposure through a median sternotomy.

The trachea and apical lung parenchyma and pleura lie just deep to the brachiocephalic or innominate artery, with the right vagus nerve passing inferiorly just distal and anterior to origin of the right subclavian artery. The right recurrent laryngeal nerve passes under and medial to the proximal right subclavian artery as it ascends back up the neck. The confluence of the right subclavian and internal jugular veins creating the right brachiocephalic vein lies anterior to the subclavian artery. The veins must be retracted laterally to expose the innominate and proximal right subclavian arteries.

The full median sternotomy is considered the standard approach for aortic arch exposure; however, a minimally invasive approach with a partial upper sternotomy to the level of the third rib has been described in a series of patients with promising results. It requires transection of the sternum at the third rib, forming an inverted “T” on the sternum. During the transection, the internal thoracic arteries run close to the sternal edge and can be injured, risking vascular compromise to the sternum. Another technique, by Tominaga and colleagues, approached exposure of the entire aortic arch with an L-incision, described as a left anterolateral thoracotomy and upper partial median sternotomy.

Exposure of the Right Subclavian Artery

The subclavian arteries are divided into three segments, proximal, middle, and distal, based on the relation to the anterior scalene muscle. The proximal segment spans from the origin of the artery to the medial border of the anterior scalene muscle. The middle segment is the portion directly posterior to the anterior scalene muscle. Lastly, the distal segment is the portion from the lateral margin of the anterior scalene muscle to the outer border of the first rib, where it becomes the axillary artery.

The proximal right subclavian artery is exposed through a median sternotomy. The incision can be extended superiorly along the anterior border of the respective SCM or along a supraclavicular, transverse line to expose the middle segment of the subclavian artery as it crosses into the thoracic outlet ( Fig. 4.9 ). The dissection will require division of the sternothyroid and sternothyroid muscles attaching to the manubrium, and the sternal and clavicular heads of the SCM.

The second and third portions of both the right and left subclavian arteries are exposed through a supraclavicular approach. An 8- to 10-cm transverse incision approximately 1 to 2 cm above the clavicle is deepened through the platysma muscle. Subplatysmal flaps are developed superiorly and inferiorly. The external jugular vein is typically ligated, and the clavicular head of the SCM is resected. The sternal head can be retracted medially or divided as needed. The omohyoid muscle is divided. The scalene fat pad is then encountered. The internal jugular vein composes the medial border of the fat pad and the subclavian vein its inferior border. The fat pad is mobilized along these veins at its medial and inferior borders and reflected. The phrenic nerve lies just below the fat pad on the anterior surface of the anterior scalene muscle, and the nerve should be identified and preserved as the fat pad is mobilized. The phrenic nerve can be carefully mobilized off the anterior scalene muscle. The subclavian artery lies just posterior to the anterior scalene, and careful sharp division of the muscle will expose the middle and distal portions of the artery. The brachial plexus lies just posterior to the artery. Sharp dissection will prevent thermal injury to the brachial plexus, thoracic duct, and vagus and phrenic nerves, all of which travel in the vicinity. Resection of the middle of the clavicle can also provide exposure for the middle and distal segments of the subclavian artery, particularly in cases of trauma. As the subclavian artery is dissected, the vertebral, internal thoracic, and thyrocervical arteries are encountered on the proximal segment of the subclavian artery, medial to the anterior scalene muscle. Of these vessels, the thyrocervical trunk can be ligated, whereas the vertebral and internal thoracic arteries should be preserved.

Exposure of the Proximal Common Carotid Arteries

The right common carotid artery is exposed in the same manner as the brachiocephalic artery, with a median sternotomy with extension of the incision along the right anterior SCM. The cervical incision can be made in continuity with the sternotomy incision or separately if a more distal common carotid artery dissection is needed. A similar maneuver is performed for the left common carotid artery, except its course begins slightly posterior on the aortic arch. The vagus nerve can be identified running between the left common carotid and left subclavian arteries as it crosses the aortic arch and gives off the left recurrent laryngeal nerve that moves behind the ligamentum arteriosum and back into the neck.

Through the cervical extension of the sternotomy, the platysma is divided, and the investing fascia, also known as the deep cervical fascia, is incised to lateralize the SCM. The sternothyroid and sternothyroid muscles are divided, exposing the internal jugular vein that is retracted laterally to fully expose the proximal common carotid artery.

Exposure of the Left Subclavian Artery

As the aorta curves to the left and posteriorly to the left side of the trachea, the left subclavian artery is the third and most posterior branch. It is relatively inaccessible through a median sternotomy. The most common means for exposure is through a left anterolateral thoracotomy in the fourth intercostal space. For access to the middle segment of the subclavian artery or the proximal common carotid artery, a separate left supraclavicular incision can be made. A third approach combines both the anterolateral thoracotomy and supraclavicular incision with a connecting sternotomy, sometimes called the “trap-door,” or “book-flap” thoracotomies. Because separate incisions for adequate proximal exposure are accomplished with reduced morbidity, the trap-door incision is not usually recommended and typically performed only in cases of penetrating trauma for emergent control.

To perform the anterolateral thoracotomy, the patient's shoulder should be elevated behind the scapula and the arm adducted to 90 degrees, with single lung ventilation. A curvilinear incision is made in the fourth intercostal space from the medial border of the sternum to the anterior axillary line. Dissection through the pectoralis fascia and muscle to the intercostal space is followed by entry into the pleural space to reduce the lung to allow the incision to be opened completely without parenchymal injury. The internal thoracic vascular bundle may require ligation to avoid traction avulsion after the rib spreader is placed. The lung is retracted inferiorly, exposing the lateral aspect of the aortic arch, and the mediastinal pleura is incised. The surgeon must be cognizant to identify the left vagus, recurrent laryngeal and phrenic nerves, and the thoracic duct, which comes up posterolateral to the left subclavian artery to drain into the junction of the left subclavian and internal jugular veins. The thoracic duct should be ligated unless it can be confidently protected during the entire operation to prevent a chyle leak or chylothorax. At this point, vascular control can be obtained at the origin of the left subclavian artery, and the proximal segment of the subclavian artery can be fully exposed ( Fig. 4.10 ).

To gain access to the middle and distal segment of left subclavian artery as it courses over the first rib, a supraclavicular incision similar to the one described for the right subclavian artery is used. When mobilizing the scalene fat pad on the left, the thoracic duct should be identified and preserved or ligated as it enters the subclavian vein posteriorly near the junction with the jugular vein ( Fig. 4.11 ).

Exposure of the Descending Thoracic Aorta

Distal to the takeoff of the left subclavian artery at the ligamentum arteriosum, the aorta courses to the abdomen anterior and to the left of the vertebral bodies and posterolateral to the esophagus. As it descends, the aorta migrates toward the midline, where it pierces the diaphragm around T12 through the aortic hiatus to become the abdominal aorta. The hemiazygos vein runs posterior to the aorta, and the thoracic duct runs to the right over the vertebrae. The descending thoracic aorta gives off many paired branches that must be attended to during dissection of the thoracic aorta, and these include the bronchial, mediastinal, esophageal, intercostal, and superior phrenic arteries.

Exposure of the descending thoracic aorta is best achieved by a left posterolateral thoracotomy. If extension into the abdominal aorta is warranted, then a left thoracoabdominal incision will provide the additional exposure. In the posterolateral approach the patient is positioned in the right lateral decubitus position with all four extremities padded to avoid iatrogenic neuropathy. Double-lumen endotracheal intubation is performed to provide single-lung ventilation. An incision is made in any space between the fourth and seventh intercostal space, dependent on the level of the thoracic aorta to be exposed, with or without the resection of the rib. The incision is oriented along the rib space, starting anterior to the midaxillary line and extended cephalad toward the tip of the scapula. Once the subcutaneous tissue is dissected, the latissimus dorsi muscle is divided, and the serratus anterior can be either divided or retracted posteriorly with a self-retraining retractor. Upward retraction of the scapula allows access to the chest wall to count the ribs to ensure the correct rib space is entered.

With the lung deflated, the intercostal muscles are divided just above the lower rib to avoid injury to the intercostal neurovascular bundle. With the lung retracted anteriorly, the aorta is seen invested in the mediastinal pleura that is then incised to obtain vascular control at any level. Incision of the pleura should be against the aorta as the hemiazygos vein runs posterolaterally to the aorta within 1 cm. The esophagus must be dissected off the aorta, which can be done bluntly. Dissection should also occur at the level of a rib at the costovertebral junction to avoid injury to an intercostal artery branch. For dissection proximally near the aortic arch, the vagus and phrenic nerves must be protected. The ligamentum arteriosum can be divided to provide access to the inner aspect of the aortic arch, but the left recurrent laryngeal nerve should be preserved. The pulmonary artery abuts the proximal thoracic aorta and should be retracted with care. For visualization of the distal thoracic aorta, the inferior pulmonary ligament is divided.

If the planned operation requires intraabdominal aorta to be exposed, it is best performed with a thoracoabdominal incision. The patient should be positioned in a modified, “lazy” right lateral decubitus position with the hips rotated approximately 45 degrees to the right or the shoulder elevated approximately 60 degrees with the support of a bean bag. This allows widening of the left thorax, as well as exposure of the groin. The superior aspect of the incision is the same as a posterolateral thoracotomy with the rib space chosen preoperatively based on the extent of the thoracic aorta to be exposed. For exposure of the visceral segment of the aorta, the thoracic incision is continued inferomedially, across the costal margin to a point along the ipsilateral rectus muscle or a point off the midline ( Fig. 4.12 ). For further abdominal aortic exposure, the incision is extended in a paramedian incision or along the midline on the linea alba as in a laparotomy ( Fig. 4.13 ).

Entry in to the chest is the same as with any thoracotomy and with clear communication with the anesthesia team. A rib retractor is placed, and the costal margin is divided to connect the thoracic wound with the abdominal incision. The diaphragm can be divided in multiple ways. With a partial division of the diaphragm to the level of the central tendon, there tends to be minimal pulmonary compromise but at the expense of requiring additional dissection to open the aortic hiatus. Other approaches are to circumferentially incise the diaphragm muscle approximately 2 to 3 cm from the costal margin and chest wall, or to completely incise the diaphragm radially. The latter two techniques provide the best exposure; however, reconstruction is more difficult with similar pulmonary outcomes. The circumferential incision may reduce the risk of a phrenic nerve injury.

Exposure of the Superior Vena Cava

The superior vena cava is best approached through a median sternotomy. Once the right brachiocephalic vein is exposed as in the exposure of the right subclavian artery, the junction of the two brachiocephalic veins can be seen lateral to the ascending aorta. The pericardial sac may need to be incised carefully, paying attention to the phrenic nerve passing more posteriorly, to expose the portions of the superior vena cava closest to the heart.

Exposure of the Axillary Artery

The axillary artery is divided into three parts defined by their relative location to the pectoralis minor muscle. The first part begins as the subclavian artery exits the thoracic outlet at the first rib and is medial to the pectoralis minor. The second part is posterior to the muscle, and the third part is lateral to the pectoralis minor. The axillary artery gives off multiple branches throughout its course, and these can be ligated. The axillary vein courses anteromedial to the artery and thus is exposed and retracted first before encountering the artery. The brachial plexus closely invests and intertwines with the artery and must be meticulously protected.

The approach is dependent on which portion and how much artery is to be exposed. Access to the first part of the axillary artery is achieved through a lateral infraclavicular incision, whereas exposure of the second and third part requires lateral extension into the upper arm or an axillary incision ( Fig. 4.14 ).

For the infraclavicular approach, the arm is abducted to 90 degrees, and an incision is made approximately 2 to 3 cm parallel and below the lateral half of the clavicle. The pectoralis major muscle is separated along the course of its fibers or divided to expose the posterior fascia and clavipectoral fascia, which are then opened. A fat pad is seen and contains the axillary neurovascular structures, with the pectoralis minor muscle defining the lateral extent of the dissection. The first vessel encountered is the axillary vein anteromedial to the artery, and the brachial plexus is invested closely posterior to the vessels at this portion of the artery. The lateral pectoral nerve typically crosses over the axillary vessels near pectoralis minor to innervate the pectoralis major. The lateral pectoral nerve arises off the lateral cord of the brachial plexus, and the medial pectoral nerve arises off the medial chord. They are named for their parental chord, not their relative position to each other, because the lateral pectoral nerve is actually medial to the medial pectoral nerve. The axillary vein can be retracted caudally, and any tributaries can be ligated as needed. The axillary artery is then isolated. For better mobilization and exposure, branches coming off the artery, including the supreme thoracic or thoracoacrominal arteries, can be ligated.

For distal exposure of the axillary artery, the infraclavicular incision is extended on to the proximal arm over the deltoid muscle in the deltopectoral groove, across the pectoralis major muscle, and toward the medial aspect of the arm. This approach will allow for exposure of the entire course of the axillary artery with minimal mobility or range of motion restrictions. After dissection through the subcutaneous tissue, the superior border of pectoralis major muscle can be identified and retracted inferomedially, exposing the clavipectoral fascia with the pectoralis minor muscle deep to it. Once the fascia is incised, the third part of the axillary artery can be isolated. It is at this portion that the brachial plexus can wrap around the artery. Particularly, the formation of the median nerve is usually anterior to the artery. Division of the pectoralis minor muscle at its insertion on the coracoid process exposes the second part of the artery, and care must be taken to avoid injury to the pectoral nerves innervating both pectoralis muscles.

In the case of more proximal arterial exposure including the distal subclavian artery, a separate supraclavicular incision can be made for proximal arterial control. In a penetrating trauma scenario the clavicle can be resected with extension of the incision toward the axilla to expose both the distal subclavian artery and entire axillary artery. The second and third portions of the axillary artery can also be exposed through an incision in the axilla. Care should be taken to preserve the long thoracic nerve and thoracodorsal nerve as they course along the chest wall. The pectoralis major is retracted medial, and the pectoralis minor can be divided to expose the neurovascular bundle. The median nerve runs anteriorly to the distal axillary artery and the ulnar nerve and axillary vein run medially to the artery.