Summary of Key Points
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Thoracoscopic access to the anterior spine should be considered as an alternative minimally invasive access approach to traditional open and mini-open access procedures.
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Thoracoscopy can be used along the entire thoracic spine (T1 to T12) and can be extended via transdiaphragmatic incision to the upper third of L2 in the retroperitoneal space. The chest cavity gets smaller at the cranial end, which can limit the access for extensive thoracoscopic procedures (e.g., discectomy, corpectomy).
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Single-lung ventilation with a double lumen endotracheal tube is crucial for thoracoscopy.
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Indications for surgery include the following:
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Anterior reconstruction of unstable fractures of the thoracic spine and thoracolumbar junction
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Posttraumatic and degenerative narrowing of the spinal canal
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Disc-ligament instability
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Posttraumatic deformity of healed fractures with or without instability
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Preparation and release of the anterior column in tumor and metastasis
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Sympathectomy for hyperhidrosis
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Protruded disc removal in degenerative disc disease of the thoracic spine
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Resection of metastatic spinal tumors
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Thoracoscopic spine surgery, also known as endoscopic-assisted or video-assisted thoracoscopic surgery (VATS), is a minimally invasive closed endoscopic approach to the anterior thoracolumbar spine for decompression and stabilization. It offers an alternative to open thoracotomy for thoracolumbar vertebral body resection from T5-L2, anterior spinal cord decompression, and spinal reconstruction with interbody and anterolateral plate instrumentation for restoration of biomechanical stability and alignment.
Spinal instability caused by trauma or destructive disease has historically been treated via a dorsal approach. Purely dorsal techniques, however, often fail to adequately address ventrally located pathology. Dorsal decompression with thoracic laminectomy for ventral epidural masses has been associated with increased risk of injury to the spinal cord. Anterior spinal canal decompression through dorsal and even dorsolateral approaches can be challenging and ineffective. Furthermore, instrumentation may not sufficiently stabilize a significantly disrupted ventral load-bearing spinal column.
To more effectively and directly decompress and stabilize the ventral spine, thoracotomy and thoracoabdominal techniques were developed. Although these approaches demonstrated improved outcomes and are an acceptable treatment modality for thoracolumbar disease, the high access morbidity of these open procedures often results in postthoracotomy pain syndromes, postoperative pneumothorax or pleural effusion, shoulder dysfunction, abdominal wall relaxation, and significant scarring of the chest wall.
Spine surgeons have more recently adapted the minimally invasive thoracoscopic techniques that have been applied by thoracic surgeons for many years. Thoracoscopic spine surgery was first used in spine surgery for the treatment of thoracic disc herniations and traumatic fractures. With the advancement of thoracoscopic video technology, instrumentation, and instrument systems, thoracoscopic spine surgery has improved significantly, and its use has been expanded to include the treatment of most thoracolumbar disorders, including trauma, primary and metastatic tumors, degenerative disease, and select deformity correction cases.
Specialized tools for endoscopic spine surgery are used to access the thoracic cavity through small chest incisions, and the surgery is performed under two-dimensional video guidance. Minimizing chest wall dissection and retraction through the use of small thoracoscopic incisions has significantly improved outcomes and reduced postoperative morbidity without compromising long-term successful fusion rates. The minimally invasive thoracoscopic approach can now be safely and effectively performed to treat disease that had previously required an open thoracotomy.
Advantages and Disadvantages
Several advantages are offered by the minimally invasive thoracoscopic approach over an open thoracotomy. Multiple vertebral levels and the ventral spinal canal can be visualized and treated without increasing surgical exposure when access ports are properly placed. The surgical field can be imaged with excellent resolution using modern high-definition endoscopic technology. The small intercostals incisions negate the need for rib resection and retraction unlike open thoracotomy approaches, which necessitate large incisions, extensive dissection of intercostal muscles, rib resection, and retraction of the chest wall. The thoracoscopic approach is associated with reduced blood loss, need for blood transfusion, days of mechanical ventilation, perioperative wound pain, incidence of pulmonary and shoulder dysfunction, length of hospital stay, and days to rehabilitation.
For most spine surgeons, the largest obstacle to using the thoracoscopic approach is unfamiliarity with the technique and high technical demand. The operation is performed distant from the surgical site in two dimensions based solely on thoracoscopic image guidance, which requires most spine surgeons to acquire a new set of skills. Before operating on a patient, the surgeon must gain familiarity with the new technique in practical and didactic training sessions. The surgeon and operating room staff must overcome a steep learning curve while gaining familiarity with the approach, and this can initially increase operative times by several hours. Anesthesia monitoring and double-lumen ventilation may also increase operative times. Conversion to an open thoracotomy may be required with difficult cases or when intraoperative complications cannot be resolved with the thoracoscopic technique. Finally, extensive intrathoracic disease, whether pulmonary or spinal, may be difficult to address with the thoracoscopic approach and may require open minithoracotomy.
Indications and Contraindications
The thoracoscopic approach is best suited in patients with thoracolumbar disease limited to one vertebral body or disc space between T3 and L3, although multiple levels may be treated. The most common indication for thoracoscopic spine surgery is in the setting of trauma. Among patients with traumatic spinal injury, ventral spinal reconstruction for biomechanical instability is the most common surgical indication. Traumatic spinal instability may be secondary to fracture, injury to the intervertebral discs, or significant ligamentous disruption. The mainstay of treatment for thoracolumbar fractures is rigid fixation with transpedicular screw and rod constructs. The decision to add anterior column reconstruction is based on the load-bearing capacity of the injured spinal segment. The load-sharing classification system developed by McCormack and colleagues established a correlation between failure of posterior short segment fixation and the characteristics of the most significantly injured vertebrae. Fractures with a high degree of vertebral body comminution, fragment apposition, and postoperative deformity correction were found to be at high risk for posterior instrumentation failure. Thoracoscopic surgery for reconstruction of the anterior load-bearing elements is indicated in these patients. Although patients with neurologic deficits from fracture intrusion into the spinal canal comprise a minor subgroup of patients with traumatic spine injury, they are also indicated for spinal canal decompression and stabilization.
In cases of spinal tumors, thoracolumbar surgery is indicated for treatment of spinal instability, radiation treatment failures, most cases of spinal stenosis secondary to epidural tumor causing neural compression, and pain intractable to conservative measures or to obtain a histologic diagnosis. The thoracoscopic approach is indicated for resection of vertebral body tumors with or without ventral spinal canal involvement and for anterior column reconstruction with interbody placement and ventrolateral instrumentation.
The thoracoscopic approach is contraindicated in patients unable to tolerate single-lung ventilation because of severe cardiopulmonary disease such as acute posttraumatic lung failure, significant pulmonary contusions, advanced chronic obstructive pulmonary disease or asthma, or hemodynamic instability. This approach is also contraindicated in patients with significant medical diseases, disturbances in hemostasis, or terminal illnesses precluding surgical treatment. The surgery may be technically challenging in patients with a history of trauma, prior surgery, or infection, because of the development of dense pleural adhesions. In cases with substantial posterior column disruption or involvement, stand-alone anterior surgery may be insufficient to achieve spinal stability, and supplemental posterior fixation should be considered.
Preoperative Assessment and Planning
Radiographic and Diagnostic Evaluation
As with other spine surgeries, careful preoperative review and understanding of the radiographic studies are essential to identify the most appropriate treatment method and to plan the surgery. The presence or extent of vertebral body disease and bony destruction, instability of the load-bearing spinal column, spinal cord compression and canal stenosis, and anatomic malalignment are noted for surgical planning. Plain radiography can be used as an initial evaluation to localize the levels of involvement; however, computed tomography (CT) must be obtained to further assess the anatomy and involvement of the osseous spine, which is important for precise surgical planning of the dimensions of the reconstruction. The spinal cord and neural elements, intervertebral discs, epidural contents, paraspinous anatomy, and soft tissues, including abnormalities such as tumors, are evaluated primarily with magnetic resonance imaging (MRI). The detail and orthogonal views displayed with CT and MRI allow the best assessment for local anatomy and disease morphology. When necessary, other imaging modalities, such as angiography for vascular spinal tumors, may be used to obtain further information of the disease process.
The preoperative evaluation for thoracoscopic surgery also includes assessing the patient’s ability to tolerate surgery under general anesthesia with single-lung ventilation. The patient’s overall medical condition, including cardiovascular and hemodynamic stability, is assessed, and laboratory studies, including a complete blood count and coagulation panel, are reviewed. The patient’s pulmonary status is also thoroughly assessed preoperatively, which may require an evaluation by a pulmonologist, anesthesiologist, or qualified internist. An evaluation by or discussion with a cardiothoracic surgeon may also be warranted in cases of pulmonary disease, previous lung injury, or infection, to decide whether the patient is suited for thoracoscopic surgery or open thoracotomy. A cardiothoracic surgeon should be available at the time of surgery, with advance knowledge of the case when possible, in the event that immediate conversion to an open exposure is needed.
Planning of Approach
The patient’s imaging studies are examined in detail to develop a thorough understanding of the individual patient anatomy, particularly the relative locations of the chest wall and thorax, thoracolumbar spine and spinal cord, and mediastinal structures. The side of surgery is chosen based on disease lateralization and location with respect to the surrounding anatomy. The locations of the aorta and vena cava are noted in relation to plate placement and the lesion being treated. A left-sided approach is generally preferred at the thoracolumbar junction (T11-L2) and for disease lateralization to the left. For lesions of the upper- to midthoracic spine (T3-T10), a right-sided approach is typically chosen.
Planning of Resection and Reconstruction
Detailed preoperative examination of the patient’s bony anatomy is important for planning the reconstruction. The appropriate lengths of the vertebral body screws are determined by measuring the widths of the vertebrae on the preoperative images. The height of the interbody is approximated by measuring the distance between the inferior end plate of the cranial level and the superior end plate of the caudal level. The plate dimensions can also be approximated preoperatively by measuring the distance between the lower third of the cranial vertebral body and the upper third of the caudal vertebral body. The extent of pathologic canal intrusion is also measured to determine the amount of bony resection needed for sufficient anterior spinal canal decompression.
Operative Technique
Thoracoscopic Instruments and Instrumentation Systems
Minimally invasive thoracoscopic instruments have been specifically developed for this application and are highly specialized. They are designed with adequate length for safe and effective intrathoracic maneuvering, have large handles for improved grip and ease of use, and are made with nonreflective surfaces to decrease glare on the endoscopic view. For illumination and optimal visualization, a high-quality endoscopic camera is essential. A high-definition 0- to 30-degree angled rigid endoscope with a high-output xenon light source provides the best digital resolution.
The room is set up with the surgeon standing directly behind the patient and operative site. A video monitor with the projected endoscopic image is placed in front of the patient, directly across from the main surgeon, and a monitor displaying the fluoroscopic image is placed beside the endoscopic video monitor. The assistant operating the endoscope stands to the right of the surgeon. The third assistant, when available, stands across from the main surgeon in front of the patient and operates the retractor and suction/irrigation devices.
In addition to specialized instruments, the MACS-TL ventrolateral thoracolumbar spinal implant (Aesculap, Tuttlingen, Germany) was specifically designed for thoracoscopic use ( Fig. 75-1 ). It consists of a rigid plate that is secured to the ventrolateral vertebral body with two pairs of triangulated fixation screws for increased strength: two posterior polyaxial screws and two anterior stabilizing screws. The screws are implanted into the normal vertebrae adjacent to the diseased vertebra(e). The fixation plate is then rigidly secured to the screws. The biomechanical properties of the MACS-TL plating system have been characterized in mono- and bisegmental partial and full corpectomy models both with and without posterior ligamentous injury. Case series have also demonstrated its clinical efficacy.
Anesthesia
The patient is placed under general anesthesia for thoracoscopic spine surgery. For maximum surgical exposure, a double lumen endotracheal tube is used for single-lung ventilation. The position of the endotracheal tube is confirmed before and after final positioning with a bronchoscope. A Foley catheter, arterial line, and, if necessary, central venous access are placed prior to patient positioning.
Patient Positioning
The patient is placed on a radiolucent operating table in the lateral decubitus position with the spine parallel to the operating table. Stabilizing supports positioned between the scapulae and against the sternum, sacrum, and coccyx are secured to the operating table for four-point stabilization. An axillary roll is placed, and a Krause armrest is used to support the top-lying arm, which is angled cranially to prevent obstruction of the instrumentation during the operation. The legs are placed in a slightly flexed position. A lateral spine view obtained with the C-arm fluoroscope confirms appropriate alignment of the spine in relation to the operating bed by aligning the anterior and posterior vertebral body lines and facet joints.
Localization
The relation of the spine and identified sites of the access portals is determined with intraoperative fluoroscopy. After optimal patient positioning, a lateral image centered over the pathologic area is obtained and projected orthograde onto the chest wall. The level of interest is often evident because of changes in spinal alignment and bony architecture. The skin is marked with a diagram outlining the vertebral bodies of the pathologic and adjacent levels by drawing the anterior and posterior spinal lines and intervertebral discs. The four portal access sites are then marked ( Fig. 75-2 ). The positioning of these portals determines working distances and is essential for proper retraction and intraoperative thoracoscopic image guidance.
The operating portal site is centered directly over the pathologic level. Instrumentation and resection can be difficult if this portal site is improperly positioned. Moreover, misdirected instruments may slide along angled surfaces and increase the risk of injury to the spinal cord and vasculature. This access site extends 3 to 4 cm in length and is large enough to insert the fusion instrumentation during the case. The other access sites are approximately half the length of the working portal. The portal site for the thoracoscopic camera is situated along the axis of the spine approximately two to three intercostal spaces from the operating portal. For lesions at the thoracolumbar junction, the access site is marked in the cranial direction. Conversely, the site is marked in the caudal direction for mid- to upper-thoracic spine lesions. The suction/irrigation portal is located ventral and cranial to the operating portal, close enough to allow for ease in irrigation and suction of the surgical bed. The retractor for the lung and diaphragm is inserted through an access portal slightly caudal to the operating portal and further ventral to the suction/irrigation portal. Maintaining sufficient distance between the retractor and operating portals prevents intraoperative interference of the thoracoscopic instruments.
Access
The entire lateral chest wall is sterilized and draped in case conversion to open thoracotomy is necessary. After the anesthesiologist initiates single-lung ventilation, the surgeon opens the most cranially located portal, which minimizes the risk of injury to the underlying organs and diaphragm. The skin is incised, and a minithoracotomy technique is used to carry the dissection down to the rib. The rib is freed from the subcutaneous tissues and intercostal muscle layers with blunt dissection, without removal of the rib, and the pleural space is entered. The first trocar is inserted through the minithoracotomy between the ribs, and the thoracic cavity is inspected with the 30-degree endoscope to confirm successful single-lung ventilation and the absence of significant pleural adhesions. The retraction and suction/irrigation access ports are placed next using a similar technique under direct thoracoscopic visualization. The operating portal is placed last because of its proximity to the intra-abdominal organs, and after the diaphragm has been safely retracted away from the access site.
Dissection and Exposure
The spine is oriented horizontally on the video monitor by rotating the endoscope. The aorta is situated ventral to the spine, and its dorsal margin demarcates the anterior border of the vertebral bodies. The dome of the diaphragm is then retracted to expose the diaphragmatic insertion, which is typically located between T12 and L1. The spine is exposed by incising the diaphragm when operating at or below the insertion ( Fig. 75-3 ). The diaphragm is incised with a harmonic scalpel where it is naturally thin, which is parallel to and 1 to 2 cm away from the insertion site. Closure of the diaphragm at the end of the case is also facilitated by this margin of tissue. The layers of the diaphragm are incised in a semicircular line along the spine and ribs. A 2- to 3-cm incision is generally sufficient for lesions at L1. For exposure of L2, the length is increased caudally to approximately 5 cm. For lesions at L3, which may be difficult to approach with the thoracoscopic technique, a more extensive incision is made in the diaphragm, and a thoracoscopic-assisted, mini-open retroperitoneal exposure is used. Once the diaphragm is incised, the retractor is inserted through the opening. The spine is exposed by mobilizing the peritoneal sac and retroperitoneal fat from the psoas muscle fascia with blunt dissection and retracting the tissue ventrally and caudally.
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