Thoracoscopic Approaches to the Spine

Published on 26/03/2015 by admin

Last modified 22/04/2025

Print this page

This article have been viewed 2471 times

CHAPTER 306 Thoracoscopic Approaches to the Spine

Francisco A. Ponce, Nicholas Theodore, Curtis A. Dickman

Minimally invasive surgery has become a major goal across surgical subspecialties. Issues as diverse as cost containment, wound aesthetics, and decreased pain have all served as an impetus to refine these techniques. Technologic advances have helped to make these procedures safe, viable options for a wide variety of pathologies.

Advances in endoscopic imaging devices have played an important role in the development of minimally invasive surgery. Endoscopic image resolution now far surpasses that previously obtained because of improved technology such as computer interfacing, optical chips, fiberoptic cables, video endoscopy, and three-dimensional (3-D) imaging. Endoscopes provide illumination, visualization, magnification, and a conduit to access areas of the human nervous system as diverse as the ventricular system and spine.

Endoscopic techniques in spinal surgery are now common for a variety of pathologies: posterolateral percutaneous approaches to the lumbar disk spaces and neural foramina, anterior laparoscopic and anterolateral retroperitoneal endoscopic approaches to the lumbar spine, and thoracoscopic approaches to the thoracic spine.¹^–¹⁴ Typically, rigid rod-lens endoscopes are used to visualize the anatomy and pathology; however, flexible fiberoptic endoscopes have also been used to inspect small spaces such as the neural foramina and syringomyelia cavities.⁷^–¹⁰ ^,13 ^,15 The resolution and image quality of flexible fiberoptic endoscopes are poorer than that of rigid endoscopes.

Endoscopes have found a valuable place in the treatment of thoracic spinal disorders. Thoracoscopy was first widely employed by cardiothoracic surgeons, and the techniques for thoracoscopic spinal surgery are adapted from their methodologies.¹⁶^–¹⁹ Today, thoracoscopic surgical techniques are used to perform sympathectomies, discectomies, and vertebrectomies; to correct deformities; to stabilize spine fractures after trauma; and to biopsy and resect tumors.

Historical Overview

Beginning in the early 1900s, thoracoscopy was used as a diagnostic tool to evaluate pleural disease.²⁰^–²³ During the late 1980s, techniques and instrumentation for endoscopic surgical procedures improved dramatically. In the early 1990s, thoracoscopic techniques were refined and applied to a broad spectrum of pathologies involving the thorax.¹⁶^–¹⁹

Today, many thoracic procedures previously performed via a thoracotomy are routinely performed thoracoscopically. These procedures include biopsy or resection of pleural or lung lesions, lymph node biopsy, biopsy and resection of mediastinal masses, lobectomy, pneumonectomy, pleural sclerotherapy, treatment of blebs, esophageal procedures, and sympathectomy.¹⁶^–¹⁹ ²⁴ In the resection of pulmonary lesions,²⁴^–²⁶ the small thoracoscopic incisions have minimized dissection and retraction of the chest wall, reduced postoperative pain, decreased blood loss, shortened intensive care unit and overall hospital stays, improved postoperative pulmonary and shoulder function, hastened recovery times, and decreased complications.^{16–19,24–26}

The techniques of thoracoscopic spine surgery were independently developed by Regan and coworkers ^3,⁶ in the United States and by Rosenthal and colleagues^5,²⁷ in Germany. The first report of thoracoscopy for spinal diseases was published by Mack and coworkers²⁸ who described 10 patients with diverse spinal pathology effectively treated thoracoscopically without major complications. Rosenthal and associates⁵ and Horowitz and coworkers⁴ published separate reports that described the techniques for performing thoracic microdiscectomy thoracoscopically. Since then, numerous reports have demonstrated the effectiveness of thoracoscopic spinal surgery for the treatment of a wide variety of spinal disorders.^16,²⁹^–³¹

Indications

Thoracoscopy can be used to access the sympathetic chain, disks, vertebral bodies, and the ipsilateral pedicle; however, it cannot be used to access the posterior elements of the spine. Thoracoscopic approaches have been used to treat herniated thoracic disks ²^–⁶ ²⁸; to drain vertebral epidural abscesses; to débride vertebral osteomyelitis and diskitis; to decompress fractures; to biopsy and resect neoplasms¹^–³ ²⁸; and to perform vertebrectomies and interbody fusions, vertebral body reconstructions and instrumentation,¹^–³ ^,28 ^,30 sympathectomies,³²^–³⁴ and anterior releases for the treatment of kyphosis and scoliosis (Table 306-1).^2,^3,^6,^28,³⁰

Table 306-1 Potential Indications for Thoracoscopic Spinal Surgery

Sympathectomy

Discectomy

Corpectomy with reconstruction

Biopsy of vertebral body or disk

Drainage of vertebral or perivertebral abscess

Resection of neurogenic tumor

Anterior release to correct a kyphotic deformity

Scoliosis to correct a deformity

Costotransversectomy, thoracotomy, and thoracoscopy are the three major techniques available to address thoracic vertebral and disk pathologies. Each technique has distinct advantages and disadvantages (Table 306-2). When the ventral aspect of the dura must be visualized well, an anterior transthoracic approach (thoracotomy or thoracoscopy) is necessary. This significantly improves visualization of the ventral surfaces of the spine and spinal cord to facilitate decompression, reconstruction, and internal fixation compared with posterolateral approaches.³⁵^–⁴⁴ For lateral pathologies, a costotransversectomy, transpedicular approach, or other such posterolateral approaches may be considered.

Table 306-2 Comparison of Operative Approaches to the Thoracic Spine

Contraindications

Contraindications to a thoracoscopic approach are similar to those for open approaches and include medical reasons that would prohibit surgery (uncontrollable coagulopathy, terminal illness, or severe cardiac or pulmonary disease). Requirements specific to thoracoscopic approaches include the ability to tolerate prolonged single-lung ventilation and the absence of significant pleural adhesions or advanced pulmonary disease. Patients with conditions such as chest trauma, a prior thoracotomy, emphysema, or hemothorax may have extensive adhesions that prohibit thoracoscopic access. Extensive scar tissue from an earlier operation at the site of spinal pathology also precludes thoracoscopy. Consequently, most patients should be evaluated before surgery by a pulmonologist or internist, as well as by a cardiothoracic surgeon when indicated. The preoperative assessment can include spirometry, blood gases, and pulmonary function studies as needed (Table 306-3).

Table 306-3 Contraindications for Thoracoscopic Procedures

Previous ipsilateral thoracotomy or thoracoscopy (relative)

History of previous pleural inflammatory disease (relative)

Cardiac or pulmonary disease precluding unilateral ventilation (absolute)

Dense pleural adhesions (absolute)

Medical reasons prohibiting surgery (absolute)

Educational Issues

Thoracoscopy represents a technique that is fundamentally unfamiliar to most spinal surgeons. Because of the restricted portals of entry, thoracoscopic techniques require new psychomotor skills for navigating and manipulating instruments from a distance while watching the procedure in real time on a video monitor. The clinical application of thoracoscopic techniques should only follow a comprehensive training program that includes didactic and practical components. Extensive practice in a surgical skills laboratory in either animal or human models is mandatory. Procedures also should be performed with the assistance of a cardiothoracic surgeon so that open exposure can be performed immediately if needed. Although there are no specific guidelines for the practice of thoracoscopic spinal surgery, the cardiothoracic surgery community has outlined the ethical and educational issues relating to the use of this technique by their practitioners.^15,⁴⁵

Thoracoscopic Technique

General Considerations

Thoracoscopic spinal surgery requires a thorough familiarity with the anatomy of the thoracic spine, spinal cord, thorax, and mediastinum. The decision to approach from the left or right side depends on the location, lateralization, and extent of the pathology. The position of the great vessels is also important to consider and may be evaluated on preoperative computed tomography or magnetic resonance imaging studies. Midline lesions are most often approached on the right side because more spinal surface area is usually available behind the azygos vein than behind the aorta. If a lesion is on the left side, a left-sided approach is more appropriate. A left-sided approach is also preferred for lesions below T9 because the diaphragm rides high on the right side at this level. In general, an exposure from T1 to the T11-12 interspace is possible via the thoracoscopic approach.

Thoracoscopic Imaging

In thoracoscopy the endoscope is used for illumination, visualization, and magnification. Unlike other endoscopic techniques, working channels within the scope are rarely used. Several separate portals are inserted in the chest wall for the endoscope and various instruments. A standard 5-mm or 1-cm diameter rigid rod-lens endoscope with a 0- to 30-degree angle of view is connected to a 2- or 3-D camera, which transmits the image to a video monitor. High-resolution 3-D endoscopes can vividly represent complex regional anatomy and enhance the surgeon’s ability to use instruments in this region. Xenon or halogen light sources are primarily used and delivered via fiberoptic cables. The endoscope is usually affixed to a table-mounted endoscopic holder with or without voice-activated robotic control to free the surgeon’s and assistant’s hands.

A clear endoscopic image is essential, and the lens must remain free of debris. The lens can be cleaned manually or by using the irrigating and automated wiper mechanisms on the tips of some endoscopes. Fogging is prevented by prewarming the endoscope, by using warmed irrigation solution, and by periodically wiping the lens with an antifogging agent. Frequent irrigation and suctioning eliminate blood from pooling in the thoracic cavity. Otherwise, blood absorbs a significant amount of light and darkens the operative field.

Instruments

The actual working distance in thoracoscopic surgery is much longer than in open procedures, with the distance ranging from 14 to 30 cm. Most of the long tools developed for thoracoscopic spine surgery require two hands for precise control during dissection and decompression of the nerves and spinal cord. These long tools also amplify motions differently than shorter tools. Techniques to master the use of long endoscopic spine tools and to avoid unnecessary movements should be practiced in the laboratory before clinical application.

During all thoracoscopic cases, a complete thoracotomy tray should be opened onto the sterile field in the operating room in the unlikely event that a major vessel is damaged or immediate conversion to an open thoracotomy is needed for another reason.

Hemostatic Agents

The techniques used to obtain hemostasis are identical to the methods used in open surgery. A number of tools and methods can be used for hemostasis in thoracoscopic spinal surgery, including vascular clips and monopolar and bipolar cauterization devices. As in open procedures, monopolar cauterization should be used with caution in the region of the spinal cord and nerve roots. Cotton-tipped peanut dissectors can be used to apply bone wax. Gelatin sponges, microfibrillar collagen, and oxidized regenerated cellulose absorbable hemostatic agents can also be used to tamponade epidural venous bleeding gently. In the event of massive hemorrhage resulting from injury to the great vessels, a tightly rolled 4 × 4 sponge on a long clamp (sponge stick) can be used to provide gentle tamponade until the chest is opened.

Operating Room Setup and Patient Positioning

A radiolucent operating table is used so that fluoroscopic images can be obtained intraoperatively. Initially, the patient is placed supine on the operating room table while a double-lumen endotracheal tube is placed. Fiberoptic bronchoscopic equipment should be kept in the room should the endotracheal tube need to be repositioned or the patient suctioned during the procedure. Typically, the anesthesiologist is positioned at the head of the operating table (Fig. 306-1). An arterial line, central venous and urinary catheters, and pneumatic compression stockings are placed. Somatosensory and/or motor evoked potential leads are connected and baseline recordings are obtained before the patient is positioned.

FIGURE 306-1 Positions of the patient, surgeon, assistant, scrub nurse, video monitors, and anesthesiologist during a thoracoscopic procedure.

(Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

The patient is then turned and placed in a lateral decubitus position with the operative side up. During a thoracoscopic procedure, the deflated lung is allowed to reexpand several minutes each hour to decrease the chance of the patient developing symptomatic atelectasis after surgery.

A foam axillary roll is used to pad the dependent axilla. The legs are flexed at the knees, and the hips and shoulder are firmly secured to the operating table so that the patient can be tilted safely during surgery. The patient’s dependent arm is placed on a padded arm board, and the upper arm is elevated on a pillow or secured via a sling or ether screen. Abduction of the upper arm moves the scapula dorsally and increases exposure of the chest wall.

Intraoperative image intensification (C arm) is positioned to obtain a clear anteroposterior view of the thoracic spine to verify the appropriate level before the skin is marked with indelible ink. Preoperative markings on the skin include the position of the portals, scapula, and potential thoracotomy incision. The patient’s entire chest, axillary region, proximal arm, back, and abdomen are then sterilely scrubbed, prepared, and draped. During the procedure the surgeon and assistant stand anterior to the patient facing the anterior thorax. Ideally, two video monitors are used, one across the operating table for viewing by the surgeons, and the other positioned for the scrub nurse.

Portal Insertion

Depending on the procedure, two to four portals are inserted to gain access to the thoracic cavity (Fig. 306-2). The portals should be spread far enough apart so that the surgeon’s hands are neither too close together nor too close to the endoscope. The working portals (for instruments) are best positioned anterolaterally between the anterior and middle axillary lines. The endoscope portal is best positioned posterolaterally between the middle and posterior axillary line. This technique allows the surgeon’s hands to rest comfortably during the procedure. The axilla and first and second interspaces are never entered to avoid injury to the brachial plexus and great vessels, respectively. Exposure from T9 to T12 requires caudal retraction of the diaphragm to expose the costophrenic recess. This exposure can be enhanced by a reverse Trendelenburg position and a fan retractor.

FIGURE 306-2 A, Patient in the right lateral decubitus position. The endoscopic port is placed posteriorly between the middle and posterior axillary lines situated over the level of interest. Working portals for instruments and retractors are placed anterolaterally between the anterior and middle axillary lines effectively triangulating the level of pathology. An optional superior (lung retraction) or inferior (diaphragm and/or lung retraction) portal can be placed as needed. B, Close-up view of the principle of triangulating the endoscope and instruments around the level of pathology. The portals should be placed far enough apart to avoid fencing.

(A, Used with permission from Barrow Neurological Institute, Phoenix, AZ; B, from Dickman CA, Rosenthal DJ. Thoracoscopic access strategies: portal placement techniques and portal selection. In: Dickman CA, Rosenthal DJ, Perin NI, eds. Thoracoscopic Spine Surgery. New York: Thieme; 1999.)

When a 0-degree angled endoscope is used, the portal is placed directly over the spinal segment of interest. When a 30-degree angled endoscope is used, the portal position must be offset above or below the level of pathology and the scope angled obliquely.

The position of the portals are triangulated over the region of the pathology and ideally evenly spaced rostral and caudal to the surgical target. If needed, a fan retractor can be placed between the anterior and middle axillary lines, rostral or caudal to the working portals.

Flexible portals are used in thoracoscopic spinal procedures to prevent injury to the intercostal nerves. Portals serve to keep blood and debris off the endoscope and instruments. An 11- or 15-mm portal is adequate for most purposes. A smaller portal can be used for a suction-irrigation tool (7 mm). A larger portal is needed when bone grafts or instrumentation are to be placed.

Before the portals are placed, the skin is infiltrated and an intercostal nerve block is administered with a local anesthetic (1% bupivicaine [Marcaine] with epinephrine). The skin is incised parallel to the superior surface of the rib to prevent injury to the neurovascular bundle. A hemostat is passed through the intercostal muscles and parietal pleura directly adjacent to the superior surface of the rib. A finger can be inserted to check for lung adhesions that would preclude the introduction of a portal at that site. Portals are placed over a rigid trocar, which is immediately removed after the portals have been placed (Fig. 306-3). The proximal end of the portal is stapled or sutured to the skin to anchor it to the chest wall during surgery.

FIGURE 306-3 A, Technique of portal insertion. After a small incision is made parallel to the superior surface of the rib and access to the thoracic cavity with a hemostat has been obtained, a flexible portal is inserted with a trocar. B, The trocar is removed leaving the portal in place. Portals can be secured with suture or surgical staples. Subsequent portals are placed under direct endoscopic vision.

(Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

The endoscope is placed after the first portal is inserted. Additional portals are placed under direct endoscopic visualization. Small adhesions can be addressed with sharp or blunt dissection techniques; however, dense, diffuse adhesions usually preclude thoracoscopic access and require conversion to a thoracotomy.

Initial Spinal Exposure

As the lung is deflated, the thoracoscope is inserted to visualize the thoracic cavity. If necessary, the operating room table is rotated 30 to 40 degrees anteriorly to allow the lung to fall away from the spine to minimize the need for retraction. When present, pleural adhesions can be detached with cauterization and scissors to mobilize the lung.

Wound Closure and Postoperative Management

At the conclusion of the procedure, after hemostasis has been obtained, the contents of the thoracic cavity are inspected carefully with the thoracoscope. All tissue debris and blood are thoroughly irrigated from the thoracic cavity. The fan retractors are removed, and the surface of the lung is inspected for air leaks or contusions as it is inflated. One or two chest tubes are placed through separate, preexisting portal incisions under direct thoracoscopic visualization to ensure proper positioning. The chest tube is secured with a heavy-gauge silk or nylon suture. The apical chest tube is used to reinflate the lung, and the posteroinferior tube is used to drain fluid and blood from the thorax after surgery.

The wounds are closed with a subcuticular skin closure. The chest tubes are placed with 20 cm H₂O of suction. The skin entry sites for the chest tubes are sealed with an occlusive dressing and nylon suture material. Postoperative chest and spine radiographs are obtained.

Thoracic Endoscopic Sympathectomy

Several clinical syndromes that result from a pathologically elevated sympathetic tone can be treated surgically by thoracic sympathectomy. These entities include palmar or axillary hyperhidrosis, pain syndromes involving the upper extremities such as reflex sympathetic dystrophy (RSD), ischemic syndromes of the hand such as Raynaud’s disease, and malignant tachyarrhythmias refractory to medical management. The second, third, and sometimes fourth sympathetic ganglia are thought to be the primary mediators of these disease processes. Traditionally, the second thoracic ganglion is considered to be the key ganglion for sympathetic denervation of the upper extremity.² Thoracic endoscopic sympathectomy, a technique first described about 50 years ago,³ provides an appealing alternative for patients with conditions that are treatable by sympathetic denervation.

Surgical Indications

Several major groups of disorders can be treated by thoracoscopic sympathectomy (Table 306-4) and contraindications for the procedure are few. Idiopathic (essential) palmar hyperhidrosis is the most common indication for thoracoscopic sympathectomy. Most patients who receive a neurosurgical referral for this condition have been evaluated for metabolic (hyperthyroidism) or neoplastic causes and have failed efforts at medical management with topical and anticholinergic agents.

Table 306-4 Indications for Sympathectomy

From Dickman CA, Baskin JJ, Theodore N. Thoracic endoscopic sympathectomy. In: Fessler RG, Sekhar LN, eds. Atlas of Neurosurgical Techniques. New York: Thieme; 2006.

In clinical series, the success rate of sympathectomy for permanent relief of palmar hyperhidrosis ranges from 90% to 100%.^33,^34,^{45–47,51,54–58}^,62 ^,64 Axillary hyperhidrosis and bromhidrosis (axillary malodor) can also be addressed through a sympathectomy that targets the T3 and T4 ganglia.⁵ Associated plantar hyperhidrosis often (50%) resolves when hyperhidrosis of the upper extremities is relieved and is referred to as a dividend benefit of the procedure because it is not an expected effect of transecting the upper thoracic sympathetic chain.

RSD (also known as complex regional pain syndrome type I)⁵⁶ is one of a number of pain syndromes that typically follow trauma. Current evidence suggests that an upregulated sensitivity of α adrenoreceptors for catecholamines in the injured limb reduces RSD. Medical therapy tends to be ineffective in terms of both the degree and duration of relief. Patients who experience symptomatic relief after percutaneous blocks of the stellate ganglion with local anesthetic agents are considered candidates for surgical sympathectomy.^33,^49,⁵⁴^–⁵⁶ Long-term clinical benefits have been reported for this indication in more than 50% of patients.²

Patients with severe upper extremity ischemia due to Raynaud’s disease or related disorders may also benefit from sympathectomy.^33,^49,⁵⁴^–⁵⁶ Although the ischemic process is typically progressive, sympathectomy can be used to avoid limb amputation and to improve the associated complaints of pains.

Sympathectomy has also been shown to effectively relieve pain related to pancreatic carcinoma via left T5 through T11 lesioning,⁵⁹ as well as treating patients with increased QT intervals via T1 through T4 lesioning.^60,⁶¹

Surgical Goals

Sympathetic denervation can be achieved through several actions. The autonomic tissue can be resected or the connections between the ganglia and the autonomic chain can be disrupted using sharp transection or thermal methods. Our practice has shifted from en bloc excision of these neural structures (ganglia with the interval sympathetic chain) to sharp transection of the ganglia and sympathetic chain with cauterization and scissors.

While this procedure is performed, the accessory innervations to the sympathetic chain must be addressed. The accessory nerve of Kuntz, if present, arises from the sympathetic trunk at the level of T1, T2, or T3. It must be transected to optimize the chances of the sympathectomy being effective.⁹ Preserving the rostral half of the stellate ganglion in its position overlying the first rib head avoids incurring Horner’s syndrome during the sympathectomy.

Patient Positioning

With the patient in the lateral decubitus position, the bed is rotated approximately 40 degrees toward the surgeon, which allows gravity to retract the lung and brings the thoracic vertebral column within view. A mild reverse Trendelenburg position allows the lung to fall away from the apex of the pleural cavity.

Two incisions are used. The first 5-mm diameter portal is placed in the middle or posterior axillary line within the fourth or fifth intercostal space (Fig. 306-4). The 5-mm-diameter rigid rod-lens thoracoscope is passed through this portal. A second 5-mm portal incision is placed in the anterior axillary line within the third intercostal space. The 5-mm-diameter endoscopic monopolar scissors are passed into the thoracic cavity. Gently patting the deflated lung with an endoscopic dissection tool produces further atelectasis and improves the visualization of the spinal column.

FIGURE 306-4 Patient positioning and portal insertion sites for a left-sided thoracoscopic sympathectomy. For a right-sided approach, the patient is similarly positioned on the opposite side.

(Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

Anatomic Orientation

Typically, the stellate ganglion, sympathetic chain, and accessory sympathetic innervation can be visualized beneath the parietal pleura. The sympathetic chain is recognized as it crosses over the rib heads (Fig. 306-5). The first rib can be palpated, and the second through fourth ribs can be visualized directly. The stellate ganglion is located directly over the head of the first rib and typically is surrounded by a fat pad within the thoracic outlet, adjacent to the subclavian vasculature.

FIGURE 306-5 A, Regional anatomy for a right-sided thoracoscopic sympathectomy. The sympathetic chain lies over the rib head and is easily identified. B, Similar anatomic overview of the left thoracic cavity. The first rib and overlying stellate ganglion can be palpated; they are rarely visualized.

(Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

Care must be taken to prevent injuring the several large regional vessels. On the right side, tributaries of the second, third, and fourth intercostal veins merge to form the superior intercostal vein, which then empties into the azygos vein. The first intercostal vein drains directly into the brachiocephalic vein. On the left side, the subclavian artery and intercostal vessels are adjacent to the region of dissection. Because the sympathetic chain is positioned superficial to the segmental and intercostal vessels, it can be transected without sacrificing any of these vessels.

Sympathectomy

At the levels of interest, the sympathetic chain is transected using the monopolar cauterization scissors (Fig. 306-6). We routinely isolate the T2 ganglia for palmar hyperhidrosis by transecting the sympathetic chain over the second and third rib heads, and include the T3 and T4 ganglia for axillary hyperhidrosis. In our experience, outcomes with this technique are comparable to those obtained following an en bloc resection of the sympathetic chain. Because the sympathetic chain does not have to be dissected away from the vertebral column, this modified procedure is safer and faster to perform. The scissors are used to hook and elevate the sympathetic ganglia away from the rib head. Centering the dissection directly over the rib head protects the intercostal nerve.

FIGURE 306-6 Transection of the right T2 and T3 ganglia using monopolar cauterization scissors during a right-sided thoracoscopic sympathectomy.

(Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

The effectiveness of the sympathectomy is judged intraoperatively by monitoring palmar skin temperature. A unilateral increase of 1° to 3° C occurs when an adequate sympathectomy has been performed.⁵ This increase in temperature typically occurs over 10 to 20 minutes. If palmar skin temperature fails to increase, the presence of an aberrant accessory sympathetic supply that is still functional must be sought. Another possibility is that the inferior third of the stellate ganglion is contributing sympathetic input that needs to be addressed.

Closure

A chest tube is connected to suction to evacuate intrapleural air. If a contralateral sympathectomy is to be performed, the chest tube is left in place with an occlusive dressing. This strategy protects against difficulties with oxygenation or ventilation related to the deflation of both lungs. After the contralateral sympathectomy has been completed, the lung is reinflated and the chest tubes are removed bilaterally. A chest radiograph (upright anteroposterior view at end expiration) is obtained in the recovery room to confirm the absence of persistent pneumothoraces. Patients are typically discharged within 24 hours of the procedure.

Surgical Outcomes

The success rate of endoscopic sympathectomy is highest for treating palmar hyperhidrosis. Several series have reported success rates between 95% and 100%.* Lesioning the sympathetic chain with a subsequent increase in the intraoperative palmar temperature of at least 3° C has provided the best immediate and long-term clinical outcomes. Axillary hyperhidrosis and bromhidrosis will improve in 80% of patients who undergo lesioning of the T3 and T4 ganglia.⁵

Complications

In a significant number of patients, sympathectomy for hyperhidrosis can cause a postoperative compensatory hyperhidrosis syndrome (CHS), which involves increased sweating of the chest, abdomen, legs, and/or back (nondenervated areas).^67,^68,⁷² CHS symptoms typically improve or resolve within 6 months of surgery.⁵³ The incidence of CHS after sympathectomy ranges between 40% and 75%.⁷¹ Many studies have shown that preservation of the T2 ganglion may reduce the incidence of CHS.^66,^68,^69,⁷² Compared with T2-4 sympathectomy in one randomized study of 232 patients, bilateral T3 sympathectomy was associated with a lower incidence of severe CHS and with superior patient satisfaction. In both groups symptoms resolved completely in all patients.⁶⁵ Other studies have proposed that T4 sympathectomy may decrease the incidence of CHS even further, although the recurrence rate of symptoms also increased.^70,⁷¹ Most patients who develop CHS have mild or moderate sweating and are satisfied with the relief of their palmar sweating. Only 5% to 10% of patients who develop CHS have severe sweating that creates a disabling problem.

Horner’s syndrome is avoided by sparing the rostral stellate ganglia and usually resolves spontaneously even if it does occur. Electrical or mechanical stimulation of this structure causes pupillary dilation that can be observed by the anesthesiologist. Gustatory sweating has been reported in 1% to 2% of patients.

Thoracic Endoscopic Diskectomy, Vertebrectomy, And Reconstruction

Indications

The indications for thoracoscopic microdiskectomies and vertebrectomies are the same as for open posterolateral and anterior approaches. The indications include symptomatic calcified or noncalcified central or centrolateral disk herniations, and all types of infectious, traumatic, degenerative, or neoplastic processes of the ventral thoracic spine.

The thoracoscopic approach provides access to the anterior and anterolateral vertebrae (the vertebral bodies, ipsilateral pedicles, and ipsilateral transverse processes), disk spaces, and ventral aspect of the dura. This exposure cannot access posterior spinal elements (laminae, spinous processes, facets), the contralateral pedicle, or the contralateral transverse process. The extent of exposure and visualization ventrally is identical to the exposure achieved with thoracotomy. Unequivocally, this anterior approach provides full visualization of the anterior spine and spinal cord, a view that cannot be achieved with posterolateral approaches.

Thoracic Spinal Anatomy

The middle of the thoracic vertebral body has a slightly concave surface (Fig. 306-7). The segmental arteries and veins course over the middle of the vertebral bodies. The disk spaces and end plates form a convex surface. Intraoperatively, the surface contours are important clues for determining anatomic relationships.

FIGURE 306-7 A, Overview of thoracoscopic anatomy and key landmarks for a right-sided approach. Lower thoracic pathology may require the placement of a retractor to keep the diaphragm out of the surgical field. B, Thoracoscopic anatomy and landmarks for a left-sided approach. C, Close-up illustration of thoracic vertebral anatomy. The ribs are attached to the vertebrae via the costotransverse and costovertebral ligaments. The head of the rib articulates with the base of the pedicle and the vertebral body just below or at the disk space. The segmental vessels cross the middle of the concave surface of the vertebral bodies.

(Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

The pedicles are dense oval cylinders of bone with a cancellous center. The pedicles are adjacent to the upper third of the vertebral body. The relationship of the pedicle to the disk space, vertebral body, and spinal canal is critical for intraoperative anatomic orientation. The neural foramen is formed by the boundaries of the pedicles of two adjacent vertebrae. Within the neural foramen, the nerve roots are surrounded by a large amount of epidural fat, a rich epidural venous plexus, and radicular arteries. The dura is therefore best exposed by removing the thoracic pedicles rather than by entering the neural foramen. The upper surface of the pedicle is contiguous with the superior surface of the vertebral end plates. Tracing the upper surface of the pedicle anteriorly leads to the disk space.

The rib heads provide essential landmarks for localization. The sympathetic ganglia and sympathetic chain are located just lateral to the rib heads beneath the parietal pleura. The ribs articulate with the transverse processes and the pedicles by strong ligamentous attachments. The rib head, which articulates with the base of the pedicle and the vertebral body just caudal to or at the level of the disk space, serves to orient the surgeon to the relative position of the disk space and pedicles. The T9 rib, for example, leads to the T8-9 disk space. The costovertebral joint is a shallow ball-and-socket type joint with a glistening surface that is a helpful anatomic feature for verifying that the rib head has been resected completely.

The costovertebral triangle is the key to unlocking the spinal canal and visualizing the nerve roots, dura, and spinal cord. It is defined by the space between where the rib joins the transverse process and the vertebral body. The surface of the pedicle is exposed by removing the proximal 2 to 3 cm of rib en bloc. The pedicle is then removed to unlock the lateral aspect of the thecal sac. Removing the pedicle early in the dissection allows the dura to be visualized clearly so the surgeon can remain oriented to the position of the spinal cord during dissection.

A predictable anatomic relationship exists among the intercostal vein, artery, and nerve. The segmental artery and vein course over the middle of the concave surface of the vertebral body. At the neural foramen, the segmental nerve joins the segmental vessels. As the neurovascular bundle extends laterally, from cephalad to caudal, the vein, artery, and nerve run in the groove on the undersurface of each rib (see Fig. 306-7C).

Thoracic Microdiskectomy

After the pathologic disk space is exposed and confirmed by intraoperative radiography, the pleura over the medial surface of each rib is incised. Cobb periosteal elevators are used to expose a 2- to 3-cm segment of the proximal rib and rib head. The neurovascular bundle and muscular attachments are detached from the rib margins using subperiosteal dissection with periosteal elevators and large curved curets. The neurovascular bundle is detached from the undersurface of the rib with careful dissection using curved curets. Bleeding from the intercostal artery or vein encountered during rib dissection is controlled with bipolar cauterization. The intercostal nerve is identified and preserved.

A Cobb periosteal elevator and curved curets are used to divide the costotransverse and costovertebral ligaments sharply. The rib head is detached from its articulation with the vertebral body and all soft tissues are removed (Fig. 306-8A). A rib-cutting tool or the Midas Rex drill with an R-8 bit or footplate attachment (R-1) is used to create an osteotomy to transect the rib. The rib head and the proximal rib are removed en bloc. Enough of the proximal rib should be removed to ensure that the disk space, pedicle, and foramen are exposed satisfactorily.

FIGURE 306-8 A, Demonstration of the disk space of interest after disarticulation and resection of the rib and upper half of the caudal pedicle to visualize the dura adjacent to the disk space. The nerve root in the foramen is surrounded by epidural fat, a venous plexus, and arterial branches. B, A 1- to 2-cm cavity is made in the dorsal vertebral bodies adjacent to the disk space to create a working space. The spinal cord can then be decompressed by dissecting the herniated disk away from the dura.

(Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

The amount of the pedicle that needs to be resected depends on the extent and location of herniated disk material. If the herniation is confined to the level of the disk space, only the superior half of the pedicle of the caudal vertebrae is removed. If the disk is broad-based or situated caudally, the entire pedicle must be resected. By removing the pedicle, the lateral aspect of the thecal sac is exposed. This visualization is critical because it enables the surgeon to protect the dura and spinal cord. Typically, the pedicle of the caudal vertebrae adjacent to the disk space must be removed. If the T9-10 disk is being removed, the T10 pedicle is resected. The pedicle is removed with a combination of drills and Kerrison rongeurs.

After the dura has been identified, the diskectomy is performed. The annulus fibrosus of the involved disk space is incised first. The thoracic disk spaces are very narrow, and the annulus is best incised with a Cobb periosteal elevator. A drill with a cutting bur is used to create a cavity 1 to 2 cm wide in the dorsal vertebral bodies adjacent to the disk space (Fig. 306-8B). Herniated disk material can then be curetted into the cavity and away from the spinal cord. Creating the cavity within the disk space and along the dorsal vertebrae minimizes the entry of tools into the compromised epidural space. Microsurgical tools and small curets are used to move the herniated disk material away from the spinal canal into the cavity. Calcified disk material or osteophytes can be removed with a fine-tipped drill. The depth of the decompression is assessed by direct visualization and can be verified with intraoperative radiographs or fluoroscopic images. The decompression can be extended completely across the ventral aspect of the dura to the contralateral pedicle. Although interbody fusion is usually unnecessary after a routine thoracoscopic diskectomy, the proximal rib harvested during the spinal exposure can be used for this purpose if needed.

Thoracic Corpectomy

The exposure for thoracic corpectomy is similar to that for thoracic microdiscectomy. First, the pleura is dissected widely from the surface of the involved vertebrae and the adjacent ribs. The segmental vessels are mobilized, occluded with hemoclips, and cut between the clips. A circumferential subperiosteal dissection of the proximal 2 to 3 cm of the adjacent ribs is performed. The neurovascular bundle is dissected from the undersurface of the proximal ribs. The ligamentous attachments of the ribs are sectioned, osteotomies are performed, and the ribs are removed (Fig. 306-9A). The pedicles of the involved vertebrae are removed with a Kerrison rongeur carefully exposing the lateral aspect of the dura and nerve roots. Diskectomies are performed to define the cephalad and caudal boundaries of the bone dissection (Fig. 306-9B). A large cavity is created within the center of the involved vertebral body with a high-speed drill, osteotomes, curets, and rongeurs. The posterior longitudinal ligament and any elements compressing the spinal cord can be clearly visualized and safely removed by curetting the material away from the spinal cord into the cavity created within the vertebrae (Fig. 306-9C). This sequence of dissection enables the dura to be visualized throughout the procedure and maximizes its safety. A strut graft can be placed within the corpectomy defect as detailed below.

FIGURE 306-9 Technique of thoracoscopic corpectomy. A, Resection of the rib at the inferior level overlying the vertebral body of interest. B, Completion of the superior diskectomy. C, Decompression of the spinal canal by removing the vertebral body away from the ventral dura.

(Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

Vertebral Reconstruction

After thoracic corpectomy, a variety of options exists for stabilization. Osseous defects from a corpectomy can be reconstructed using autologous iliac crest struts, allograft bone shafts (Fig. 306-10A), or methylmethacrylate. Autologous rib or a whole-diameter (allograft) humerus shaft usually fits well within the thoracic vertebrectomy site. The length, width, and depth of the bone graft and the vertebrectomy defect are measured precisely. Before the defect is measured and the graft is inserted, the spinous processes are pushed forward externally at the apex of the patient’s kyphosis to optimize spinal alignment. The bone graft is sized to the exact length of the vertebrectomy defect. One end of the graft is cut with a slightly beveled surface to allow the graft to be wedged into position. The bone graft is inserted end-on through a 20-mm flexible portal into the thoracic cavity. The bone graft is grasped with an endoscopic clamp and positioned into the vertebrectomy defect. Bone graft impactors and mallets are used to compress the bone grafts precisely into the vertebrectomy bed. The relationship of the graft to the dura must be observed throughout the insertion of the graft. This relationship can be confirmed with intraoperative radiography.

FIGURE 306-10 Technique of vertebral body reconstruction. A, Placement of humeral allograft into corpectomy defect. B, Placement of Silastic tubing into corpectomy defect with subsequent injection of methylmethacrylate to anchor it to surrounding bone (C).

(Used with permission from Barrow Neurological Institute, Phoenix, AZ.)

Another method of spinal stabilization that can be used for neoplastic disease is methylmethacrylate reconstruction (Fig. 306-10B, C). After the dimensions of the resection defect have been measured, a sterile Silastic tube is cut 5 to 6 mm longer than the end plates at the margin of the vertebrectomy defect. Holes are made in the adjacent vertebral end plates with drills and curets to fit the tube diameter. The Silastic tube, which serves as a template for the methylmethacrylate until it sets, is telescoped into the bodies of the adjacent vertebrae. A hole is cut in the middle of the tube to allow injection of methylmethacrylate. A long, wide-bore needle with a pressure syringe is used to inject the methylmethacrylate. Slow-setting cranioplasty methylmethacrylate is preferred to rapid-setting methacrylate because it allows the polymer to be injected and produces much less heat as it sets, minimizing the risk of injury to the spinal cord. The methylmethacrylate is injected until it completely fills the Silastic tubing and seeps through the ends into the adjacent vertebrae. The Silastic tube acts like a mold while the methylmethacrylate hardens. Extrusion of the methacrylate into the adjacent bone is mandatory to provide an anchor that will prevent the polymer from loosening or becoming displaced. Additional methacrylate can be added ventral and lateral to the tube; however, care should be taken to ensure that the dura and spinal cord are not compressed by the polymer.

These reconstructive techniques can be augmented with screw-plate devices applied thoracoscopically or with posterior instrumentation constructs.

Thoracic Endoscopic Resection of Thoracic Tumors

Indications

Thoracoscopy may be used in place of thoracotomy for the resection of certain intrathoracic neoplasms such as paraspinal neurogenic tumors.⁶⁶ Such tumors are benign in more than 95% of cases.^65,⁷² Although uncommon, they compose 75% of posterior mediastinal masses and 10% to 34% of mediastinal tumors.^68,⁶⁹ These tumors arise from two cell types, nerve sheaths and autonomic ganglia. The former includes schwannomas and neurofibromas, whereas the latter includes ganglioneuromas, neuroblastomas, ganglioneuroblastomas, and paragangliomas. Although most tumors are discovered incidentally, patients may become symptomatic with dyspnea, shortness of breath, pain, Horner’s syndrome, pneumonia, and hoarseness. The purpose of resection includes obtaining a tissue diagnosis, preventing tumor growth within the spinal canal, relieving mass effect within the chest, and preventing malignant transformation.

Endoscopic resection of neoplasms entails piecemeal removal of the tumor through the ports. Given the need to minimize seeding of malignant cells via en bloc resection, malignancy is a contraindication. Furthermore, malignant tumors can be poorly demarcated and can invade or encase blood vessels, mediastinal structures, and bone. An open thoracotomy should be used. Intradural tumors are unamenable to thoracoscopic resection. Dumbbell tumors, however, may be resected via a staged procedure combining a posterior laminectomy followed by thoracoscopy.