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

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

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