Indications
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The decision to approach the thoracic spine with a transpedicular corpectomy depends largely on the view and angle of exposure needed. This approach provides access to the lateral spinal canal, to the neural foramina, and to a portion of the posterolateral vertebral body. A bilateral transpedicular approach can provide 270 degrees of decompression if needed. Common pathologies treated by thoracic transpedicular corpectomy include lateral disk herniations, epidural tumor, osteomyelitis or diskitis with or without abscess, and lateral canal decompression from trauma.
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Posterior segmental fixation can be performed after resection of anterior and posterior elements, for unstable lesions associated with trauma, or for deformity. An anterior graft or cage should be placed unless a minimal amount of vertebral body is removed, as in a transpedicular biopsy.
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Many approaches are available for thoracic lesions, including thoracotomy, retropleural, extensive lateral extracavitary, and costotransversectomy approaches. The appropriate procedure depends on the following factors: (1) the location of the lesion (bone, epidural, paraspinal); (2) the angle of view needed; (3) the nature of the specific lesion (hard or soft, invasive or encapsulated); (4) the goal of treatment (en bloc resection or palliative decompression); (5) the patient’s comorbidities and their ability to tolerate a thoracotomy; and (6) the surgeon’s familiarity with technical aspects of the procedure. Transpedicular corpectomy is often used for patients with acute neurologic decline from epidural metastasis in whom palliative decompression rather than en bloc resection is the goal.
Contraindications
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Contraindications to a transpedicular corpectomy are primarily anatomic. Access to the midline anterior dura, epidural space, and vertebral body is limited. In some cases, soft or suctionable lesions near the midline may be resected without direct visualization. It is seldom possible, however, to achieve adequate or safe decompression of midline or paracentral disk herniations via this approach, especially if they are calcified. These lesions often adhere to the dura anteriorly and require sharp dissection under direct visualization to prevent spinal cord traction and injury.
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Other contraindications relate primarily to the nature of the lesion and the goals of surgery. This approach is well suited for palliative decompression from metastatic epidural compression, tumor debulking, and biopsy. When spondylectomy or en bloc resection is required, significant modifications or an alternative surgical approach are necessary.
Planning and positioning
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Begin with a thorough review of the patient’s neurologic symptoms, medical comorbidities, and imaging characteristics. Myelography is sometimes helpful, particularly in defining osteophytes and bony anatomy. Bony tumor infiltration is best seen on magnetic resonance imaging (MRI), particularly with T1-weighted sequences with and without contrast agent and with T2-weighted sequences with fat-suppressed short-tau inversion recovery (STIR). Computed tomography (CT) can differentiate sclerotic from lytic lesions. Plain x-rays best show sagittal and coronal alignment of the spine.
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Pay particular attention to the axial views on MRI or CT to help determine the angle of view needed and the appropriate surgical approach for the case. The key issue for selection of an approach is the ability to visualize the lesion of interest without spinal cord retraction. Neurologic deterioration or paraplegia can occur from additional traction on an already compromised spinal cord. Look at the relationship between the pathologic lesion and the spinal cord, midline, dura, disk space, pedicle, and nerve root.
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The patient is positioned prone and secured tightly to the frame to allow bed rotation. We prefer a rotating Jackson table with the arms extended upward to facilitate fluoroscopy or navigation-based instrumentation, unless the lesion is in the upper thoracic spine, in which case the arms are secured downward. We use prepositioning, postpositioning, and intraoperative somatosensory evoked potential and motor evoked potential monitoring in almost all cases.
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A common pitfall for thoracic surgery is accurate localization, which requires careful attention to anatomy and fluoroscopic technique. To prevent localization errors, preoperative x-rays of the entire spine should be reviewed to identify the last visualized rib or number of lumbar vertebrae. Intraoperative counting and confirmation of the correct operative level should be done by multiple techniques in anteroposterior and lateral planes. Anatomically numbered ribs articulate with the disk space above the same numbered vertebral body. Preoperative localization with a coil or cement by interventional radiology can limit the chance of operating on the wrong level.
Figure 67-1:
Axial views of the typical thoracic vertebral body. Shaded areas correspond to approach-specific zones of bony decompression and surgical access for unilateral ( A ) or bilateral ( B ) transpedicular corpectomy. Correlation with preoperative axial MRI and CT is necessary for preoperative planning. Bony removal of the facet and pedicle to the level of the posterior vertebral body cortex facilitates access to the lateral disk, spinal canal, and vertebral body pathology. If the pathology is a soft tumor, midline anterior decompression can often be achieved.
Figure 67-2:
The length of the incision is determined largely by instrumentation (if needed), degree of intended exposure, and surgeon preference. If possible, anterior and posterior hardware should always be placed unless only a minimal amount of the vertebral body is removed (i.e., biopsy). If anterior hardware is needed, at least two levels above and below the corpectomy site should be exposed. We use a midline incision because of anatomic familiarity, adequacy of exposure, potential for bilateral access, and ease of instrumentation.Related posts:
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