Lateral Extracavitary Approach to the Thoracocolumbar Spine

Patient Selection

28.1.1 Indications

The lateral extracavitary approach provides the greatest extent of circumferential spinal cord exposure possible using a posterior approach. This is accomplished by way of a midline incision; subperiosteal dissection of the paraspinal musculature from the posterior elements; and bony removal of the ipsilateral proximal rib, facet, transverse process, and pedicle. The lateral extracavitary approach is an ideal option for surgical exposure and decompression of the thoracic spinal cord where anterolateral dural compression is observed on radiographic imaging. This approach is often performed bilaterally in the case of broad ventral compressive causes seen in trauma, diskitis with epidural abscess, degenerative disk disease, metastatic epidural spinal cord compression, nerve sheath tumors, meningiomas, and, less commonly, primary bone tumors.

28.1.2 Contraindications

This procedure is done with the patient in the prone position, as with virtually all midline posterior approaches. Therefore, patients with significant traumatic injury resulting in thoracic trauma with cardiopulmonary limitations may not be ideal for surgical intervention in the acute stage, especially with a relatively more involved spinal approach such as this. Severe scoliosis and other deformations of the spine, including congenital deformations causing severe abnormalities of the ribcage or spine, may dissuade the surgeon from performing a lateral extracavitary approach. The causes of thoracic deformities are numerous and should be factored into the preoperative decision-making process before surgery.

28.2 Preoperative Preparation

A preoperative evaluation is necessary to determine the ability of the patient to tolerate prone positioning for relatively prolonged durations and often with considerable operative blood loss. This evaluation is done primarily by a preoperative screening by a cardiologist, who will evaluate the patient and estimate the relative risk of a perioperative cardiac event. Patients with mediastinal injuries from trauma should be evaluated by a pulmonologist as well or by a trauma surgeon to determine whether the patient can tolerate operative positioning and of course to screen trauma patients for occult hemorrhage. In the setting of thoracic trauma or neoplasm, preoperative transfusion with packed red blood cells may also be required as the expected blood loss will be elevated. Preoperative embolization of hypervascular neoplasms is an option that can be helpful in limiting operative blood loss. Moreover, preoperative administration of targeted biologic therapies in certain primary bony tumors has been shown to help with decreasing intraoperative blood loss.

28.3 Operative Procedure

28.3.1 Description

Because of the sensitivity of the thoracic contents and the inability to approach the spine from a true anterior approach, the lateral extracavitary approach was developed to approach the posterolateral and anterolateral aspects of the spine and dura without the need of an anterior thoracic or abdominal exposure. The spinal cord cannot tolerate retraction, and this approach provides the maximum corridor for safe introduction of instruments to resect tissues ventral to the spinal cord. Furthermore, the corridor afforded by this approach is wide enough to allow for en bloc spondylectomy, which is desirable in primary neoplasms ( ▶ Fig. 28.1). Lastly, a corridor of this size allows for large strut grafts and expandable cage implants to fill large ventral defects, providing anterior column support.

Fig. 28.1 Computed tomography (CT) of the thoracic spine, sagittal (a) and axial (b) reconstructions demonstrating a primary neoplasm of the T4 and T5 vertebral body with expansion into the right mediastinum and infiltration into the right rib head seen on the axial image. A CT-guided biopsy was performed, resulting in a diagnosis of giant cell tumor. The 35-year-old patient was neurologically intact and opted to initially undergo adjunctive chemotherapy with denosumab, a monoclonal antibody to the RANK ligand, a protein key in osteoclast function. Surgical resection was used with a lateral extracavitary approach at the affected T4 and T5 levels. The tumor was markedly necrotic and avascular, likely a feature of good initial response to the targeted molecular agent. The lateral extracavitary approach in this case provided a safe corridor for a gross total resection and spinal cord decompression, as a proximal rib resection was required as well as a resection of the extrapleural mediastinal mass and hemivertebra involvement.

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