Anterior Thoracic Diskectomy
William R. Hotchkiss
Jacob M. Buchowski
INTRODUCTION/INDICATIONS
Thoracic disk herniations present a unique problem to the spine surgeon. Most thoracic disk herniations are in fact asymptomatic and can be found in up to 37% of the population.1 Herniations that cause symptoms are much more uncommon likely due to the stability that is intrinsic to the thoracic spine via the rib cage. The vast majority of thoracic disk herniations requiring surgery occur in the lower thoracic spine. The choice of surgical approach is often difficult for the spine surgeon, with many concerns to consider. The goals of surgery for any thoracic disk should include safety and access to the entire compressive lesion.
Anterior thoracic diskectomy is frequently done via a standard thoracotomy approach. Access via thoracotomy can be done for all levels from T3-L1 with full exposure of the anterior portion of the intervertebral disk and vertebral body.2 Disk herniations most preferable to this approach are centrally based herniations that may or may not be calcified with compression of the ventral spinal cord. Calcification of the disk fragment is an important consideration as manipulation of the spinal cord at this level can have devastating neurologic consequences and inspection of the dura following removal of the fragment is critical. Diskectomy with or without corpectomy provides excellent visualization of the central disk fragment along with the ventral spinal cord. The surgeon must critically evaluate each patient for myelopathic signs and symptoms as indications of thoracotomy and diskectomy. Disk herniations that occur more laterally without a central focus on the ventral cord can be candidates for other procedures, as discussed in later chapters in this textbook. Figure 16.1 represent a calcified central disk herniation that would be accessed with an anterior approach.
ANTERIOR THORACOTOMY
Preoperative Planning/Positioning
Intraoperative neuromonitoring is recommended to monitor the spinal cord during the entire case and should be part of the preoperative plan. Angiography is also a consideration to determine the specific location of the spinal arteries and the artery of Adamkiewicz. Avoiding dissection into the foramen can prevent catastrophic damage, but knowledge of the anatomy is good information for the surgical team. With the need for collapse of the lung on the side
of the exposure, discussion with the anesthesia team and planned use of a double lumen endotracheal tube is also necessary. The thoracic surgeon will also need to place a chest tube at the completion of the case. After approach has been completed, verification of the correct level should be done meticulously, either counting down from the occiput or up from the sacrum. In some circumstances, preoperative markers may be placed by an interventional radiologist to increase the precision of intraoperative identification of the level of interest (Fig. 16.2).
of the exposure, discussion with the anesthesia team and planned use of a double lumen endotracheal tube is also necessary. The thoracic surgeon will also need to place a chest tube at the completion of the case. After approach has been completed, verification of the correct level should be done meticulously, either counting down from the occiput or up from the sacrum. In some circumstances, preoperative markers may be placed by an interventional radiologist to increase the precision of intraoperative identification of the level of interest (Fig. 16.2).
 Figure 16.1 Large central calcified T10-T11 herniated disk (A) Sagittal T2-MRI, and (B) Axial T2-MRI causing cord compression and myelopathy. |
 Figure 16.2 Fiducial marker placed into the vertebral body by interventional radiology. |
 Figure 16.3 Left-sided thoracotomy. |
Patient positioning on the operating table depends greatly on the level of disk herniation. The thoracotomy approach is most often done by the thoracic surgeon with knowledge and experience with the exposure (Fig. 16.3). For the upper thoracic exposure most surgeons prefer the exposure to be on the right side to avoid the cardiac structures and vessels, whereas in the lower thoracic exposure a left-sided approach is utilized to avoid the friable inferior vena cava as well as the liver. The patient should be positioned in the lateral decubitus position and stabilized with a standard beanbag as well as axilla roll and then stabilized with tape. An operating table with the ability to place a break at the level of herniation should be used.
Procedure
The incision is then mapped using lateral fluoroscopy, in a curvilinear fashion centered on the disk space of herniation. Meticulous positioning using the assistance of fluoroscopy is necessary to ensure that the spine is level in the vertical and horizontal planes to prevent misadventure when preforming diskectomy and entering the canal or foramen by mistake (Fig. 16.4). Operating microscope or loupes should be used during this procedure to allow careful evaluation of many important structures that will be encountered.
The incision is made with a scalpel blade and superficial tissue dissected using electrocautery. The muscle is elevated off the most superior aspect of the rib to avoid injuring the neurovascular bundle that runs along the inferior edge of the rib in the intercostal space. Subperiosteal dissection is then completed around the rib carefully, avoiding entering the pleura. Prior to visualizing the pleura, the ipsilateral lung should be deflated by the anesthesia team with interval reinflation to prevent excessive postoperative atelectasis. The parietal pleura is then divided to the level of the rib head. Rib head removal is usually employed to allow greater access to the disk space and allows for bone graft. Verification of the correct level should be done meticulously, either counting down from the occiput or up from the sacrum. In some circumstances, preoperative markers may be placed by an interventional radiologist to minimize the amount of counting that needs to be done in the operating room. Segmental vessel ligation
is not needed for a single level diskectomy; however, it may be necessary if corpectomy is planned. Identifying the transverse process, foramen, and pedicle is critical to gain safe access to the posterior disk. Partial removal of the caudal pedicle is necessary to better visualize the disk herniation for decompression. The endplates of both the cranial and caudal vertebrae of the disk space are then burred to a thin posterior cortex with some increased working room to be able to access the entire herniation as needed (Fig. 16.5). Meticulous inspection of the ventral dura is a critical portion of the case to evaluate the need for dural repair as calcified disk herniations usually contain adhesions to the ventral dura. Fusion may be employed if desired by using the rib head autograft bone with a plate and screws or rods as desired or
indicated based on stability and the amount of adjacent endplates resected for adequate access and exposure to the disk space and herniation.
is not needed for a single level diskectomy; however, it may be necessary if corpectomy is planned. Identifying the transverse process, foramen, and pedicle is critical to gain safe access to the posterior disk. Partial removal of the caudal pedicle is necessary to better visualize the disk herniation for decompression. The endplates of both the cranial and caudal vertebrae of the disk space are then burred to a thin posterior cortex with some increased working room to be able to access the entire herniation as needed (Fig. 16.5). Meticulous inspection of the ventral dura is a critical portion of the case to evaluate the need for dural repair as calcified disk herniations usually contain adhesions to the ventral dura. Fusion may be employed if desired by using the rib head autograft bone with a plate and screws or rods as desired or
indicated based on stability and the amount of adjacent endplates resected for adequate access and exposure to the disk space and herniation.
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