Procedure 20 Endoscopic Thoracic Diskectomy
Indications
The indications for thoracoscopic diskectomy are similar to the indications for other procedures to treat central thoracic disk herniations.
Thoracoscopic spinal surgery may also be performed for nerve sheath tumor resection, anterior release for scoliosis, sympathectomy for hyperhidrosis, or vertebral corpectomy. Figure 20-1 shows a 55-year-old female patient with an incidental finding of a mediastinal mass on a chest radiograph. An axial computed tomography (CT) scan (see Figure 20-1, A), as well as axial (see Figure 20-1, B) and sagittal (see Figure 20-1, C) magnetic resonance imaging (MRI), showed a dumbbell-shaped tumor (peripheral nerve sheath tumor) of a nerve root with expansion of the neuroforamen. The tumor was successfully removed with simultaneous posterior and thoracoscopic excision.
Controversies
• The use of navigation systems has been shown to facilitate operation (Holly et al, 2001).
• Posterolateral approaches, such as a transpedicular or costotransversectomy approach, could address a ventral herniation; however, these approaches are ideal for paracentral lesions (Johnson et al, 2000).
• A multilevel procedure may be better undertaken with thoracotomy because of longer operative time with thoracoscopy.
• A preoperative angiogram has been recommended to determine location of the artery of Adamkiewicz (Di Chiro et al, 1970). However, for a thoracic diskectomy, ligation of a segmental artery is rarely necessary.
• Fusion may be necessary when excessive disk material is removed or the spine is otherwise destabilized.
Examination/Imaging
Symptoms of a thoracic herniated disk correlate with thoracic radiculopathy, thoracic back pain, myelopathy, or vague nondermatomal leg pain (Anand and Regan, 2002).
In very challenging patients with poor anatomic localization, midthoracic lesions with little anatomic cues, or obvious vertebral body deformation, percutaneous placement of a radiopaque marker (Guglielmi detachable coil) in the pedicle adjacent to the disk in question can be performed preoperatively using CT guidance from a dorsal approach (Binning and Schmidt, 2010).
CT scans define the bony detail and a calcified disk better than MRI.
Treatment Options
• Open thoracotomy and excision of central disk herniation through transthoracic approach (Figure 20-6, A)
• Posterolateral approach for lateral calcified disk herniation or central soft disk herniation: transpedicular or transfacet pedicle-sparing approaches (Figure 20-6, B)
• Other methods of treatment for ventral disk herniation include lateral extracavitary and costotransversectomy approaches (Bohlman and Zdeblick, 1988) (Figure 20-6, C).
Surgical Anatomy
The neurovascular bundle runs on the inferior border of the rib. The rib heads are more cephalad (i.e., closer to the disk space) in the cephalad levels. Above T10, a complete rib head resection may be needed to expose the disk space (Johnson et al, 2000; Moro et al, 2004).
For a T7-8 diskectomy, the T8 rib head should be resected.
The disk space is cephalad to the pedicle.
The artery of Adamkiewicz is usually on the left and between T9 and L3.
Anatomy Pearls
• Use a bed with a break to allow lateral bending of the patient, to open the rib interspaces in small patients.
• Position the patient parallel to the room architecture.
• Check fluoroscopy before making the incision to ensure adequate imaging of appropriate level.
• Many radiologists will localize a thoracic lesion using the cervical spine and counting caudad. This can lead to wrong-level surgery, because intraoperative confirmation of the level is usually performed using the lumbar spine and thoracolumbar junction and the ribs. Therefore the authors suggest obtaining high-quality radiographs and MR images of the lumbar spine, with visualization of the thoracolumbar junction, and relating the anatomic nuances (osteophyte, disk collapse, short rib, etc.) to the thoracic imaging.
• Prepare the ipsilateral iliac crest, in case a fusion procedure is necessary.
• Ensure that the table can easily tilt anteriorly, to aid in lung retraction.
• The Trendelenburg position can facilitate hemostasis.
• Poor positioning of monitors can hinder vision and flow of the operation.
• If there is a history of previous thoracic surgery, strongly consider entering the chest from the contralateral side to avoid adhesions and scar tissue.
• Vacuum sand bag, intraoperative monitoring wires, and bed attachments in line with the fluoroscope may hinder high-quality intraoperative images.
Positioning
Give prophylactic antibiotics for gram-positive organism coverage.
The proper surgical team, anesthesiologist, and monitoring setup are crucial.
Apply antithromboembolic stockings and sequential pneumatic compression.
A double-lumen endotracheal tube is placed for single-lung ventilation.
The patient is placed in the lateral decubitus position, with the ventilated lung down (Figure 20-7). The arm is held in an “airplane”-type holder to expose the chest wall.
