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LATERAL EXTRACAVITARY/LATERAL PARASCAPULAR APPROACH TO THE THORACIC SPINE
USES
The lateral extracavitary approach allows for simultaneous exposure of the posterior bony elements and the anterior vertebral column. In the upper thoracic spine, this approach is modified to include mobilization of the scapula to provide adequate visualization of the anterior column of the spine (lateral parascapular approach). Both approaches can be used for a variety of indications including metastatic vertebral body tumors, thoracic disk disease (especially centrally located ones), vertebral osteomyelitis with instability or canal compression, anterior neural tumors, pathological or anterior compression fractures, and primary tumors of bone. It is particularly attractive for cases where both an anterior decompression or release must be combined with a posterior fusion and arthrodesis. This approach allows for both of these goals to be accomplished during one operation and precludes the need for staged procedures and prolonged hospital stays. Like a standard midline posterior approach, the lateral extracavitary and parascapular techniques allow for long-level posterior instrumentation. These approaches can be used from C7 down to the thoracolumbar junction. Below L1, the lumbar roots, lumbar plexus, and the iliopsoas musculature tend to limit the degree of anterior exposure.
ADVANTAGES
The lateral extrapleural and extrascapular approaches are advantageous in that they allow for simultaneous anterior decompression and posterior instrumentation at one sitting. They provide far more anterior access and visualization than the transpedicular or costotransverse approaches. Whereas these traditional approaches do not allow for anterior column restoration, the lateral approaches typically afford more than enough exposure for decompression, grafting, and restoration of normal anterior column height and alignment. Although a standard thoracotomy does provide superior anterior visualization for cases requiring complex reconstruction, the morbidity of the diaphragmatic dissection, pleural dissection, chest tube drainage, and severe associated pain can be preclusive for older or more unstable patients. The single lung ventilation typically required for a thoracotomy is also not tolerated by many patients. Additionally, the need for a second surgical procedure for posterior stabilization adds even further surgical risks. For such cases, the single-stage lateral extracavitary/parascapular procedure may be the procedure of choice.
DISADVANTAGES
This approach is associated with higher immediate blood loss than is a standard thoracotomy. Additionally, the surgical time for anterior exposure during a lateral extracavitary approach is longer. Thus, in cases where only anterior reconstruction is needed, the thoracotomy may be a better choice. Although one- or two-level anterior exposures can be readily achieved via this approach, extensive or diffuse vertebral body disease is often best treated through a more direct anterior corridor. This is especially true for lesions of the high thoracic spine where even a well-mobilized scapula can limit the surgical access to the anterior column. Other relative contraindications to the procedure include severe cardiac or pulmonary disease, a life expectancy of less than 3 to 6 months, and the inability to tolerate or accept a blood transfusion.
STRUCTURES AT RISK
As in the standard posterior approach to the thoracic spine, the paraspinous musculature is at risk during the dissection and exposure. Partial denervation of the erector spinae at the level of the exposure is unavoidable, but long-level injury should be avoided to prevent delayed neurogenic deformity of the spine. The lateral parascapular approach also places the trapezius, latissimus dorsi, and subscapular musculature at risk if the loose areolar plane separating these muscles from the erector spinae is violated. This dissection when carried too far anterior or lateral also places the long thoracic nerve, brachial plexus, and subclavian vessels at risk. The risk of skin flap necrosis is also increased as more intercostal vessels are sacrificed. As the anterolateral aspect of the vertebral body is dissected, the intercostal neurovascular bundle can easily be injured, which often occurs during removal of the rib head and transverse process. Pleural injury with associated pneumo- or hemothorax is not uncommon and a chest tube should always be available. Horner’s syndrome, nerve root injury, sympathectomy, and intercostal neuralgia may occur.
TECHNIQUE
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