Thoracic Disc Disease

The surgical management of disorders of the thoracic spine began in 1814 when H. J. Cline attempted to treat a fracture of the thoracic spine by laminectomy.¹ In 1911, Middleton and Teacher undertook the first surgical procedure for a thoracic disc herniation, which was later described by Benjamin.² In this case, the patient was paraplegic and subsequently died.

Historically, the diagnosis of a thoracic disc herniation was a challenge. Given the lack of imaging, the diagnosis was required to be made solely on clinical history and physical findings. In addition, early surgical results were quite dismal. The evolution of diagnostic imaging and surgical techniques in the later half of the 20th century has resulted in a significant improvement in the diagnosis and outcome of patients with thoracic disc herniation.

Thoracic disc herniation is a relatively infrequent clinical diagnosis, accounting for 0.25% to 0.75% of all disc herniations and approximately 4% of surgical cases.^3,4 The symptoms of thoracic disc herniation are variable and often nonspecific, and many patients experience a protracted clinical course with a delay in diagnosis. Radiologic studies focused on computed tomography myelography and magnetic resonance imaging have demonstrated an 11% to 14.5% incidence of thoracic disc herniations.^5,6 Woods and colleagues⁷ found disc herniations in 37% of the 60 asymptomatic patients evaluated by magnetic resonance imaging.

There has been a significant evolution in the surgical management of thoracic disc herniation. Early surgical therapy consisted of laminectomy, which often resulted in paraplegia and carried a combined operative mortality as high as 10%.⁸ In 1969, Perot and Munro reviewed 91 laminectomies for thoracic disc herniations and found no neurologic improvement in 40 of the patients and progressive paraplegia in 16 of these patients.⁹ Others have also reported similarly poor outcomes with laminectomies for thoracic disc herniation.^10–12 Variations on the surgical technique were employed with laminectomies, including the use of decompression alone, decompression and transdural removal of disc material, and decompression with transdural rhizotomy and sectioning of the dentate ligaments, but all these successive approaches had similarly poor outcomes. The only exception to this pattern of poor surgical outcomes was the series reported by Horwitz and colleagues¹³ in 1955 in which five consecutive cases of thoracic disc herniation treated with laminectomy resulted in a good outcome. In 1998, Fessler and Sturgell¹⁴ reviewed and reported on 60 years of the literature in which they compared the mortality and morbidity rates with the various surgical approaches to the thoracic spine. They concluded that laminectomy does not provide adequate access to safely treat thoracic disc herniations.

In response to the uniformly poor outcomes after midline dorsal approaches to thoracic disc disease, surgical alternatives were developed using the anterior or extended posterolateral approaches with the costotransversectomy, transpedicular, and the lateral extracavitary approach.^9,15–17 Maiman and colleagues¹⁸ in their report on the lateral extracavitary approach for thoracic disc herniation reviewed 23 cases. None of the patients in the review experienced any new deficits postoperatively. This surgical technique, however, required significantly more soft-tissue dissection and manipulation, with the paraspinous muscles being mobilized medially, resulting in devascularization and denervation. This was found to contribute to poor wound healing and increase in perioperative kyphosis. In addition, the lateral parascapular extrapleural approach, as developed by Fessler and colleagues, provided exposure to the upper thoracic spine, which was comparable with the lateral extracavitary approach. However, it presents the risk of significant shoulder girdle dysfunction due to lateral scapular mobilization.¹⁹ These approaches, despite their complexity, yielded significantly improved surgical and neurologic outcomes when compared with laminectomy for thoracic disc herniations.

The transpleural approach to the thoracic spine dates to 1958 when Craffoord and colleagues²⁰ reported the use of this technique for herniated thoracic discs. In 1969, Perot and Munro⁹ reported the use of this approach in two patients, and in the same year Ranasohoff and colleagues¹⁵ reported the results of a similar approach for three patients. Since that time, the benefits of the anterior transthoracic approach have been supported by other published series.^21–23

In 1988, Bohlmann and Zdeblick²¹ recommended the anterior transthoracic approach over the costotransversectomy to treat herniated thoracic discs. This anterior transthoracic approach required a thoracotomy with rib resection and often resulted in significant perioperative morbidity including pulmonary dysfunction, intercostal neuralgia, and shoulder girdle dysfunction.^24–26

Spinal Endoscopy

The beginnings of endoscopic surgery date to 1807 when Philip Bozzini developed an endoscopic device that he called the Lichtleiter.²⁷ This, like other earlier endoscopic devices, was primarily used to explore body orifices using reflected light. Later, optical lenses were incorporated, and in 1910, Jacobeus^28,29 reported the first use of an endoscope to explore the thoracic cavity. He used a cystoscope to examine the pleural cavity in the treatment of tuberculosis and eventually expanded its use to the diagnosis of malignant and benign pulmonary diseases.^30,31 Since that time, thoracoscopes have been adapted to treat a variety of pulmonary disorders including penetrating chest injuries.^32–34

Spinal endoscopy began in 1931 when Burman³⁵ published a report on a technique he called myeloscopy. He described the use of an arthroscope to examine cadaveric spines and explore the lumbar thecal sac. In 1938, Pool^36,37 expanded on Burman’s work and used a hot lamp system with improved visualization of the thecal space to examine more than 400 patients between 1938 and 1942. Despite the initial success of Barman and Pool, spinal endoscopy did not immediately gain widespread acceptance. Optical resolution and the light intensity were poor, and the instruments were far too large to easily explore and work in the confines of this small surgical space. Advances in fiber optics and the development of modern video technology have led to resurgence in interest in endoscopic approaches to the spine. Small cold light sources and video display monitors have replaced the older hot reflected light and lens tube systems.

In 1983, Hausmann and Forst³⁸ used a nucleoscope to inspect the disc space for loose fragments after an open discectomy, and in 1992, Schreiber and Leu³⁹ successfully performed a percutaneous discoscopy. The procedure was rapidly applied to surgery for thoracic disc herniations.^40,41

The anterior approaches provide an unsurpassed exposure of the ventral aspect of the spinal column. It not only provides a large working area in which the adjacent anatomic structures became clearly identified but also provides the optimal angle for removal of intervertebral discs and allows easy inspection of the spinal cord. If necessary, repair of the dura in cases of intradural disc herniations can be performed via this approach. The anterior approach has become the preferred approach for most thoracic spinal pathology other than far lateral lesions.^2,9,15

The risk associated with the anterior transpleural approach is that of injury to the adjacent vascular and visceral structures. There is additional associated morbidity with prolonged pulmonary dysfunction, incisional pain, and pain associated with thoracostomy tube drainage that contributes to the potential adverse consequences. Comparative studies have shown a lower rate of pulmonary morbidity with thoracoscopic procedures when compared with open thoracotomy. Thoracoscopy minimizes the incidence of intercostal neuralgia and avoids shoulder girdle dysfunction. In addition, there are reduced blood loss and a proven reduction in hospital length of stay.^42–44

The dramatically improved optics and lighting of rigid glass endoscopes as developed by physicist Harold Hopkins in 1970 nurtured the rapid growth of endoscopic surgical techniques.⁴⁵ Landreneau and colleagues⁴⁴ reported 106 such cases in 1993 in which they compared video-assisted thoracoscopic surgery (VATS) with thoracotomy. The patients who underwent VATS had less pain, improved pulmonary function, and superior shoulder girdle function when compared with thoracotomy patients. That year, Mack and colleagues published a report demonstrating the potential of VATS to provide reliable access to the ventral surface of the thoracic spine.⁴⁶ In 1995, Caputy and colleagues⁴⁷ demonstrated the successful use of VATS in performing thoracic discectomy on both cadaveric and porcine models. In that study, the clinical use of thoracoscopic dissection was also reported.

Although the benefit of VATS is usually compared only with the alternative thoracotomy, data also suggest that it is a less morbid procedure than a costotransversectomy. Rosenthal and Dickman⁴⁸ reported a series of 55 patients who underwent thoracoscopic discectomy and compared the rate of complications of the thoracoscopic procedures with both the patients undergoing open thoracotomy and the patients undergoing costotransversectomy for thoracic disc herniations. There were no instances of postoperative neurologic deterioration in either the thoracoscopic or thoracotomy group, but of those patients undergoing costotransversectomies, 7% experienced new neurologic deficits after surgery. Intercostal neuralgia, both temporary and permanent, has been a significant problem associated with thoracotomy. The use of VATS has significantly reduced the incidence of this painful disorder. In that series, there was a 16% rate of intercostal neuralgia in the VATS group compared with 50% in patients who had a thoracotomy. In all patients in the thoracoscopic group with intercostal neuralgia, the condition was temporary and resolved completely within 1 to 2 weeks. In patients undergoing costotransversectomy, there was a 20% rate of intercostal neuralgia.⁴⁸

Thoracic Cavity Anatomy

The surgical anatomy includes the external anatomy of the chest, the intrathoracic visceral and vascular anatomy, the contents of the posterior mediastinum, the ribs, the vertebrae, and neural elements.

A thorough knowledge of the anatomy of the thoracic cavity is critical for a successful procedure as well as for avoiding complications. The muscles of the chest wall, primarily the serratus anterior, pectoralis major, and latissimus dorsi, form important landmarks for thoracoscopic port placement. The serratus anterior forms the medial wall of the axilla. The pectoralis major demarcates the anterior axillary line and serves as the anterior border for trocar insertion, whereas the latissimus dorsi denotes the posterior axillary line and the posterior border for trocar placement. Attention should also be paid to the mammary gland overlying the anterior and lateral thoracic wall. Its origin just anterior to the midaxillary line, from the second to the sixth rib, is at risk during trocar introduction.⁴⁹

Inside the thoracic cavity, transparent parietal pleura covers the anterior, posterior, and superior aspects of the chest cavity. It reflects over the great vessels, trachea, esophagus, and spinal column and is easily separated from these structures. Commonly, the parietal pleura is studded with anthracotic pigment, indicating exposure to smoke or other inhaled pollution over the patient’s lifetime. Chronic inflammation of the pleura can render it opaque and prevent visualization of the underlying structures.

The normal lung is pink, soft, and covered by visceral pleura. The right lung is composed of three lobes, whereas the left has two lobes. Each is divided by one or two fissures. Deflation and retraction of the lung permit visualization of the majority of the intrathoracic structures.

In the center of the chest cavity lies the mediastinum, containing the heart and great vessels. The heart is enclosed within the glistening pericardial sac, with the phrenic nerve overlying the lateral surface. Accessing the right side of the thoracic cavity permits visualization of the right subclavian and brachiocephalic vessels. The right pulmonary artery, right main stem bronchus, and distal trachea can also be seen with retraction of the lung. Inspection of the left side of the chest cavity displays the left subclavian artery, descending aorta, and internal mammary vessels. The left carotid artery is difficult to visualize in its position deep to the brachiocephalic venous trunk.

An inferior view of the chest cavity is defined by the diaphragm. Divided into two halves, the diaphragm originates from the xiphoid process, upper lumbar vertebrae, and lower six ribs. During full expiration, the right hemidiaphragm ascends to the level of the fourth intercostal space and the left to the level of the fifth rib. This fact must be considered at the time of trocar placement to avoid perforation of the diaphragm and violation of the peritoneal cavity.

The complex vascular anatomy of the paravertebral area as demarcated from the intrathoracic perspective requires a detailed understanding before embarking on thoracoscopic procedures. The posterior intercostal arteries of the first two vertebral segments arise from the superior intercostal artery branch of the costocervical trunk of the subclavian artery. The lower posterior intercostal arteries arise segmentally directly from the aorta. The segmental branches on the right are longer and traverse a greater distance than segmental branches on the left. These arteries leave the aorta and travel on the side of the vertebral body between the intravertebral discs. These arteries are crossed, immediately anterior to the rib head articulation, by the sympathetic chain. The arteries then course superiorly under the tip of the transverse process, merging with the vein and nerve in the costal groove. At this point, the artery gives off a branch that continues in a posterior course over the transverse process to supply the muscles of the back. Before passing over the transverse process, however, it sends a spinal branch through the intravertebral foramen, which supplies the spinal cord (Fig. 160-1).

FIGURE 160-1 Anatomic dissection displaying the relevant surgical anatomy of the retropleural space with the vertebral column oriented in the horizontal plane. Highlighted are the rib (open star), intervertebral disc (black star), segmental vessels (black arrow), intercostal neurovascular bundle (gray arrow), splanchnic nerve (thin arrow), and sympathetic chain (open arrow). Note the relationship of the intervertebral disc to the segmental vessels and sympathetic chain.

The primary blood supply to the lower thoracic spinal cord is via the great radicular anastomotic artery of Adamkiewicz. This vessel most often enters from the left side between T8 and L3. Disruption of this radicular artery can lead to spinal cord infarction and paraplegia. Spinal angiography should be considered for locating this vessel before exposure of the lower thoracic spine.⁵⁰ However, angiography is generally unnecessary when a thoracoscopic technique is used.

The posterior intercostal vein courses in the intercostal space adjacent to and in a rostral position with the posterior intercostal artery. Blood from the spinal cord, spine, and posterior muscles converges at the level of the rib head. The segmental vein courses over the lateral aspect of the vertebral body, merging, depending on the location, with the azygos, hemiazygos, or superior intercostal vein.

The first intercostal vein ascends over the first rib and arches above the pleura to terminate in the corresponding brachycephalic or vertebral vein. The second and third intercostal veins unite to form a superior intercostal vein. On the right, this vein drains into the terminal part of the azygos vein, and on the left, it branches into the brachycephalic vein. At all levels below the third intercostal region, the veins empty into the azygos vein on the right and into the accessory hemiazygos vein on the left. The hemiazygos and accessory hemiazygos veins cross to the right side of the thoracic cavity, emptying into the azygos vein. The azygos vein then ascends and empties into the superior vena cava just before passing through the pericardium.

To avoid injury to the phrenic nerve and subsequent diaphragm paralysis, a more thorough understanding of its course is warranted. Upon leaving the cervical plexus, the phrenic nerve accesses the thoracic cavity via the thoracic inlet and runs along the lateral border of the brachiocephalic trunk. On the right, the nerve continues along the superior vena cava, over the right side of the heart, and into the diaphragm. On the left, the nerve runs between the left common carotid and subclavian vessels until it meets the diaphragm.

The sympathetic chain and ganglia lie in the retropleural space over the rib heads in the upper chest cavity, cross the segmental vessels, and move medially to lie over the vertebral bodies in the caudal portion. The sympathetic chain is made up of ganglia linked by interganglionic cords. This chain is located anterior to the rib head of the thoracic vertebrae and crosses the segmental vessels. The medial branches of the upper five ganglia supply the thoracic aorta via the thoracic aortic plexus. The medial branches of the lower ganglia coalesce to form the splanchnic nerves. The anterior rami of the thoracic nerves form an intercostal nerve. Each nerve is connected to the ganglion of the adjacent sympathetic trunk by a gray and a white communicating ramus. They pass forward in the intercostal space below the intercostal vessels. The sympathetic preganglionic nerve fibers are conveyed through white rami to the sympathetic trunk. They in turn synapse with the cells of the sympathetic ganglia. These ganglion cells of the sympathetic chain send out postganglionic fibers through the gray rami, which return to join the spinal nerves.

The vagus nerves and their recurrent branches also lie within the thoracic cavity. The left vagus nerve runs between the left common carotid artery and subclavian artery, then passes between the left pulmonary artery and the aortic arch. It continues in close proximity to the esophagus, where it forms the anterior vagal trunk. The left recurrent laryngeal nerve arises below the aortic arch and ascends into the neck in the tracheoesophageal groove. The right vagus nerve runs anterior to the right subclavian artery and deep to the brachiocephalic vein. It then gives off its recurrent branch and continues along the trachea and ends as the posterior vagal trunk along the esophagus.⁵¹

Thoracic Spinal Anatomy

The thoracic vertebrae are distinguished from their lumbar and cervical counterparts by their articulation with the ribs. There are two points of connection of the ribs with the thoracic vertebral column. One is at the vertebrae, and the second is at the transverse process. On the second through ninth thoracic vertebrae, these articulations are shared by adjacent vertebrae by a demifacet. The rib head articulation thereby covers the intervening intravertebral disc. The 1st, 10th, 11th, and 12th rib heads articulate with a single vertebra. The articular capsule surrounds the joint and becomes continuous with the intervertebral fibrocartilage of the annulus. A radiate ligament connects the rib head with the side of the vertebral bodies spanning the adjacent vertebrae and the annulus. Anterior to this ligament are the ganglia of the thoracic sympathetic trunk and the pleura. Contained by the radiate ligaments are the synovial membranes of the demifacets and the intra-articular ligament connecting the rib head to the annular fibers belonging to the demifacets. The second point of attachment of the rib to the vertebrae is by the costotransverse articulation. This is a synovial articulation connecting the tubercle of the rib with the transverse process of that vertebral segment.

The thoracic vertebrae increase in size as one moves caudal in the spine, and they form a nearly circular vertebral canal whose anteroposterior dimensions are equal to the transverse dimensions. The demifacets articulate with the vertebral bodies. At the vertebrae above the articulation, this articulation is lateral and at the root of the pedicle. The articulation with the vertebrae below is near the inferior vertebral notch covering the pedicle and is in close proximity to the transverse process and the superior facet. The facet joints of the vertebrae are oriented in a coronal plane, with the inferior facet of the superior vertebrae overlapping the superior facet of the inferior vertebrae as do shingles on a roof. The 1st cervical as well as the 9th, 10th, 11th, and 12th vertebrae have no demifacets. The synovial joints with the rib are contained over the vertebrae and lateral pedicle of that single vertebra. The ribs of the 11th and 12th vertebrae have no articulations with transverse processes.

Positioning

The lateral decubitus position is used for most VATS procedures. In most cases, the lesion is approached from the right unless the pathology is distinctly lateralized to the left. The approach from the right is preferred because there is more working space between the azygos vein and the rib head and there is less risk of injury to the aorta and heart. An axillary roll is placed between the axilla and the operating table on the patient’s down side, and the upward, nondependent upper extremity is supported at right angles to the body. The dependent lower extremity is slightly flexed, and all bony prominences are padded. The patient is secured to the operating table with 3-inch tape, and the stability of this position is tested by rolling the table from side to side before the patient is prepped and draped.

Operating Room Setup

After positioning, the anesthesiologist is placed at the patient’s head to control the endotracheal tube and facilitate lung collapse and single-lung ventilation. The surgeon and first assistant stand on the abdominal side of the patient, and a second assistant is positioned on the patient’s dorsal side. Two video monitors are positioned one on each side of the patient’s head. The nurse is positioned at the foot of the table opposite the principal surgeon. A thoracotomy set is to be immediately available for use should proper exposure not be attained via the VATS exposure or should excessive bleeding occur. A thoracic surgeon should also be available.

Endoscopic Instruments

Open radiolucent ports are used because they do not obstruct the fluoroscopy or radiographic localization during surgery. The ports most commonly used are 10 mm in diameter but can range from 3 to 18 mm. Smaller ports cause less pressure on the neurovascular bundle. Rigid ports are used for the initial thoracoscopy but may be substituted for flexible models during the actual surgical decompression to minimize the tissue pressure in the intercostal area.

After initial port placement, the pleural cavity is inspected. The lung is further deflated by suctioning through the endotracheal tube to the isolated lung. The table is tilted in the patient’s ventral direction, 30 degrees toward the principal surgeon. This allows displacement of the lung and the mediastinal contents in a more anterior direction away from the spinal column, improving the exposure of the operative area. The Trendelenburg or reverse Trendelenburg position will improve the exposure of the lower and upper spine, respectively.

Three or four ports are needed to provide a surgical working area for a VATS discectomy. These ports are arranged in a reverse L pattern (Fig. 160-4). The first port is placed in the anterior axillary line at the sixth or seventh intercostal space to avoid injury to the diaphragm. After the initial lung inspection, two or three more ports are inserted under direct inspection. These ports are centered on the area of interest. Two additional ports are placed, one rostral and the other caudal to this initial port. A fourth port may be placed at the caudal corner of the reverse L pattern if further lung or diaphragm retraction is required in the case of lower thoracic lesions. One of the ports is used for the endoscope. It is usually the more posterior port, along the posterior axillary line. The remaining ports along the anterior axillary line serve as the working channels. Proper placement of the ports is critical to ensure that the surgical instruments inserted through any given port are not inhibiting the use of a second instrument inserted through a second port. Ports that are placed too close together can cause fencing when the instruments crowd the operative area and make contact with the shaft of the other instruments, thereby inhibiting the free movement of the primary surgical instrument.

FIGURE 160-4 Standard operating room setup for thoracoscopic discectomy. The patient has been placed in the left lateral position, and thoracoscopic ports have been inserted in the reverse L pattern. Monitors are displayed on either side of the patient to permit viewing of the operative field by both the primary surgeon and the assistant(s).

The imaging equipment consists of the endoscope, light source, camera, video monitors, and video recorders. The endoscopes may be either rigid or flexible, but the most commonly used scope is a rigid rod-lens system in which the image is transmitted through a series of quartz rods to a camera mounted at the end. The field of view through the lens can vary from 0 to 70 degrees, but the 30-degree lens is preferred because it affords the greatest visualization of the operative field. In addition, better angles of inspection of the surgical area and the thoracic cavity are afforded by a 30-degree scope.

The illumination is provided by a remote halogen or xenon light source transmitted through fiber-optic cables. The video camera sensor is attached directly to the end of the endoscope, and the camera sends its output directly to the monitor where the image is displayed. The cameras are now of high resolution, which produces intense, accurate color images.

Instruments that are used by the thoracic surgeons for VATS procedures have become the mainstay for VATS discectomy. These instruments are longer and have been adapted with pistol grips. They include scissors and dissectors with articulating heads that allow the tip to be repositioned for greater visualization during the surgical dissection (Fig. 160-5). Other instruments have been developed to aid in the specific needs unique to the thoracic cavity, such as fan retractors and suction irrigation devices.

FIGURE 160-5 Close-up view of the various thoracoscopic instruments, including fan retractors for displacing the lung and graspers/scissors for performing soft-tissue dissection and disc removal.

The existing instruments common to spinal surgery have been modified by lengthening and by providing a greater variety of tip angles. These include a variety of periosteal elevators, curets, rongeurs, and dissectors. Modified long drill bits with coarse diamond bits are available (Midas Rex, Fort Worth, TX) (Fig. 160-6).

FIGURE 160-6 Extended diamond drill bits for removing vertebral elements and calcified disc herniations. Long protective collars accompany these bits to shield the intrathoracic viscera, nerves, and vascular structures.

Description of Procedure

Once the ports have been placed and the exposure of the spinal column is complete, the level must be determined. The ribs are counted from the apex of the thoracic cavity. The first rib is usually not visualized because it is covered by the subclavian fat pad. It can, however, be palpated, and the ribs can be counted to determine the level of operative interest. This is confirmed by the use of an image intensifier or intraoperative radiograph. Once the level has been confirmed, the rib head is palpated and the pleura over the proximal rib and disc space is incised. The segmental vessels are dissected, mobilized, and isolated. For single-level disc pathology, ligation is usually not required. However, if necessary, the vessels are then ligated with endoscopic hemoclips and cut with the endoscopic cautery scissors. The pleura is then further mobilized by the use of a Cobb elevator to expose a 3-cm segment of the rib head. The rib head is removed by using a high-speed pneumatic drill with a rough-cut diamond bur (Midas Rex). The diamond bur provides tactile feedback and significantly aids in controlling bone bleeding and thereby increases the visibility at the operative site. An alternative method of removing the rib involves sectioning a 2- to 3-cm segment of rib head en bloc to be used for an arthrodesis.

Once the rib head has been removed and the lateral disc space is clearly identified, the spinal canal must be defined. To accomplish this, the pedicle immediately posterior to the costovertebral articulation is exposed. The upper one third of the pedicle is typically removed using the diamond bur and a Kerrison rongeur. An extended rostral removal of the pedicle may be necessary if the disc herniation is large or calcified. Removing this portion of the pedicle exposes the anterior portion of the vertebral canal and the posterior longitudinal ligament. The normal dura and the epidural space are identified. Epidural venous bleeding may be encountered, and it is generally controlled with the use of the bipolar cautery or Avitene (CR Bard, Murray Hill, NJ). The decompression of the spinal canal and the removal of the disc material may now take place under direct visualization. A portion of the vertebral body on either side of the disc is removed to create a working channel (Fig. 160-7). This is accomplished using a shielded diamond bur to fashion a pyramid-shaped space. The disc material is pulled away from the thecal sac into this cavity (Fig. 160-8).

FIGURE 160-7 Postoperative three-dimensional computed tomography reconstruction of the thoracic spine shows the area of disc and vertebra removal needed to perform the discectomy. The cephalad portion of the lower pedicle has been removed to expose the lateral thecal sac and define the anterior margin of the vertebral canal. The cavity created provides a working space into which disc material can be pulled to decompress the spinal cord.

FIGURE 160-8 Intraoperative thoracoscopic view of herniated disc material being removed with a thoracoscopic pituitary rongeur. The dural margin is visible (arrow), allowing direct visualization of the thecal sac during completion of the decompression.

The amount of bone removed to create this space is determined by the size of the disc herniation and the amount of associated canal compromise. The working channel must be large enough to afford visualization of the normal dura rostral and caudal to the disc herniation. For large calcified discs or when an intradural fragment is identified, an extended vertebral body resection may be necessary. After the spinal canal has been exposed through this working channel, the disc material may be pulled away from the spinal cord into this created working space. If the disc material is soft, then it may be removed with a pituitary forceps or a curet. In the case of a calcified disc, however, care must be taken to sequentially dissect it away from the dura. The decompressed spinal canal is inspected and palpated to the level of the contralateral pedicle. If an intradural fragment is encountered, then it should be carefully dissected from the adjacent pia-arachnoid. A dural repair is accomplished with a tissue patch and fibrin glue. A lumbar drain is placed postoperatively.

Although a generous vertebral body resection may be required to adequately decompress the spinal cord in some cases of disc herniation, it is usually not necessary to perform an arthrodesis, and alone, it does not produce instability of the thoracic spine. If the patient has had a previous laminectomy or posterolateral procedure, then an arthrodesis may be indicated.

The surgical bed and thoracic cavity is irrigated copiously to remove blood and bone debris. The chest cavity and lungs are inspected, and a chest tube is inserted under direct visualization using one of the existing port sites. The chest tube is set to water seal rather than to suction. The remaining ports are removed, and the wounds are closed in sequential layers. The chest tube is removed when there is no air leak, drainage is less than 15 ml per 24 hours, and lung reexpansion is documented on a chest radiograph.