Posterior Approach to the Thoracic Spine

POSTERIOR APPROACH TO THE THORACIC SPINE

USES

This approach is used for a diverse number of indications including scoliotic or kyphotic deformity, fractures, vertebral body tumors, vertebral or paravertebral infections, and osteomyelitis. When this approach is combined with a laminectomy, tumors and other lesions of the posterolateral spinal cord, canal, and nerve roots can also be treated. Additional visualization of far lateral bony or canal lesions is achieved through modifications of the midline posterior approach. These modifications include the costotransverse, transpedicular, and lateral extracavitary approaches. True ventral pathology of the spine, however, may require anterior or transthoracic approaches to minimize risks of neurological deterioration.

ADVANTAGES

The posterior midline approach is readily achieved with easily palpable landmarks. There are few neurovascular structures at risk during a routine approach to the bony lamina and posterior elements. An extensive extensile exposure can be achieved from the cervical to lumbar spine if necessary for complex scoliotic deformities.

DISADVANTAGES

Visualization of anterolateral pathology is often limited through a midline approach. Furthermore, treatment of some anterior lesions (e.g., herniated disks) through a simple posterior approach and laminectomy has been associated with an unacceptably high incidence of neurological sequelae or deterioration. Correction of severe deformities via a posterior approach is often precluded without a concurrent or antecedent anterior release procedure.

STRUCTURES AT RISK

Certain aspects of the thoracic spinal cord place it at increased risk during a routine midline posterior approach. The thoracic spinal canal is tighter around the cord than in either the cervical or lumbar regions. Thus, laminectomy of the thoracic canal must be achieved cautiously under direct visualization to prevent accidental cord compression and injury. Additionally, the upper and midthoracic regions of the spinal cord are crucial to the vascular supply. The artery of Adamkiewicz typically is found on the left side between T9 and T12 in 80% of patients. As it is often the major segmental arterial supply to the anterior spinal artery, injury to this structure should be avoided to prevent spinal cord ischemia. At the level of the neural foramen and further laterally, the surgeon must also identify the intercostal nerves and vessels. The parietal pleura is also immediately adjacent and anterior to the ribs. Unintentional pleural injury with pneumothorax can result. The deep layer of the paraspinous musculature (e.g., sacrospinalis, semispinalis, multifidi, and rotators) are supplied by posterior rami. Lateral dissection beyond the transverse processes may lead to their denervation.

TECHNIQUE

The patient is positioned prone on the operative table. A multitude of cushion arrangements and special frames are available for use. Allowances for intraoperative X-rays should also be anticipated. The abdomen should be allowed to hang loosely to decrease venous back pressure. All pressure points and the groin should be free of compression.

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