Anterior and Lateral Approaches to the Thoracic Spine

Overview

The transpedicular approach provides a working channel adjacent to the cord through a posterior midline incision, allowing posterior instrumentation and ventral access without the need for a second incision, repositioning, or retraction of visceral structures. Additional posterior maneuvers, such as osteotomies for deformity correction, may also be performed without repositioning. The necessary working corridor dictates the type of approach and is ultimately determined by the patient’s pathology. Decompression, stabilization, and realignment procedures are all possible through a posterolateral approach. Surgical goals dictate the necessary bony removal, exposure, and overall plan for each procedure.

Operative Planning

For elective cases, consideration must be given to preoperative optimization, including bone quality, nutrition, narcotic use, and smoking status. Preoperative embolization may reduce blood loss, particularly in tumor cases. Surgical adjuncts such as intraoperative advanced imaging, navigation, or vertebroplasty may be useful and should be planned preoperatively. Localization in the thoracic spine can be particularly vexing, and radiographic markers placed preoperatively may save operative time and reduce errors.

Transpedicular decompression destabilizes the spine, mandating instrumentation in nearly all cases. Two levels of bilateral pedicle fixation above and below the vertebrae of interest is typically adequate. Longer fusions may be indicated for cases of poor fixation (such as extensive bony metastases, dysplastic pedicles, or osteoporosis) or biomechanical concerns (i.e., obesity, transitional segments, or deformity/kyphosis).

Surgical Technique

Once intubated, the patient is positioned prone on an open frame table, such as a Jackson, and the head is secured with Gardner–Wells tongs. Somatosensory-evoked potentials and motor-evoked potentials are monitored by the neurophysiology team. Arms may be positioned at the sides or abducted and flexed, as determined by surgeon preference, taking into account the patient’s body habitus and the procedure’s upper instrumented vertebra. Attention must be dedicated to localization, taking advantage of all available landmarks, including skull, sacrum, ribs, and preoperative markers. Radiographically evident pathology, such as a fracture or local deformity, should also be taken into consideration.

Antibiotics are administered, and steroids are administered in cases with preoperative cord compression. Prothrombotic agents, such as tranexamic acid, can help to minimize blood loss. We typically employ a moderate bolus and maintenance dose of 30 mg/kg and 3 mg/kg/h, respectively, unless clinically contraindicated.

Exposure proceeds from a midline incision in a standard subperiosteal fashion, exposing the posterior elements to the tip of transverse processes bilaterally. Care is taken to preserve the integrity of midline structures and facet joints at the proximal and distal junctions. Unless there is an acute need for decompression, our practice is to perform the instrumentation before decompression to afford protection of the cord during screw placement, as well as accommodate any need for temporary rod placement. Pedicle screw placement can be guided by anatomic landmarks or navigated, depending on preference and operating room capability. Typically, the level at which the transpedicular decompression will be performed is not instrumented. Screw placement is confirmed by intraoperative computed tomography (CT), fluoroscopy, or x-rays.

Following confirmation of instrumentation, attention is turned to bony removal. For strictly decompressive procedures, laminectomies are performed at the level of interest and adjacent levels using Leksell rongeurs or a high-speed drill. Inferior facets at the level of interest and the level above are removed using an osteotome or high-speed burr. Superior facets at the level of interest and the level below are removed in similar fashion. A combination of Kerrisons and curettes are then used to complete the removal of the soft tissue elements. Early localization of exiting nerve roots above and below the level of interest facilitates safe bony removal. In the case of epidural tumors and abscess, pathological tissue may be encountered at this stage and may be sampled. The remaining pedicle and transverse process may then be removed using a high-speed burr or Leksell rongeurs until they are flush with the posterior aspect of the vertebral body ( Fig. 117.2A ). Disc spaces above and below should be identified. Soft ventral pathology may be removed at this point with the use of curettes or sharp dissection. If necessary, partial corpectomy may be performed with an osteotome or high-speed burr (see Fig. 117.2B , C ). Anterior decompression should be confirmed with careful palpation ventral to the spinal dura, as well as visual inspection (see Fig. 117.2D ).

The transpedicular approach for stabilization, or placement of anterior column support, typically demands a larger working corridor than that for decompression alone. This mandates a wider bony exposure in anticipation of rib head and lateral vertebral body removal. Up to 5 cm of rib at the level of interest and the level below may be exposed. Bony decompression is performed as in a decompressive procedure, with additional preparation of the anterior column for support placement. Immediately before or after pedicle removal, the lateral aspect of the vertebral body should be exposed subperiosteally. Exposure should be from disc to disc, with soft tissues held out of the way with retractors or soft gauze. Proximal ribs are cut with rib cutters or rongeurs, and the rib head is disarticulated from the vertebral body using a periosteal elevator or osteotome. Discectomy and corpectomy can then be performed using osteotome, high-speed burr, and curette. End plate exposure and corpectomy size are determined by cage dimensions.

Posterior approaches to the ventral thoracic spine for realignment are typically performed to confer flexibility across an otherwise stiff deformity. This frequently mandates complete or near-complete corpectomy, or resection of fusion mass. For this surgical goal, bilateral transpedicular approaches are required, as is removal of the vertebral body or fusion mass to its anterior border. This may be performed safely by first dissecting the lateral vertebral body as anteriorly as feasible, then continuing to dissect anteriorly as the corpectomy is performed bilaterally. The anterior cortex of the body may then be removed with rongeurs, and thin cortical segments fractured in a controlled fashion.

For ventral intradural pathology, linear dural opening midline or paramedian can be used. A trapdoor approach can also be used to gain further lateral access at this point. Following tumor removal, cortical surfaces are decorticated, and allograft can be placed over the decorticated surfaces. Autograft is avoided in the case of infections and malignancies. Antibiotic powder is placed in the wound, along with subfascial drains. The wound is then closed in a standard fashion.

Postoperative Care and Follow-Up

Patients are typically admitted for floor-level care. If there is concern for transient neurological deficits or fluid shifts, admission to an intensive care unit (ICU) may be warranted for maintaining mean arterial pressure and other hemodynamic parameters. Otherwise, early mobilization is encouraged, as well as monitoring for acceptable subfascial drain outputs. Standing long cassette x-rays are obtained for baseline alignment ( Fig. 117.3 ). Chest x-rays may be obtained if there is concern for pneumocephalus during the case. If present, conservative management with serial imaging until it resolves often suffices. Chest tubes may be required for clinically significant or large, persistent pockets of air.