Idiopathic Scoliosis: Discectomy
Surgical Technique for Anterior Thoracoscopic Correction of Idiopathic Scoliosis: Chapter 3
Exposure and Discectomy
The patient positioning is checked to confirm he/she has remained in the direct lateral decubitus position. This orientation provides the surgeon with a reference to gauge the A/P and lateral direction of the guide wires and the screws. The position will again be checked just prior to placement of the guide wires. The patient is prepped and draped, with the prep extending into the axilla and including the scapula.
Once the lung has been deflated, the initial portal is made in the 6th or 7th interspace using the alignment marks made previously. This ensures the portal is in line with the spine and positioned according to the amount of spinal rotation. Inserting the first portal at this level will avoid injury to the diaphragm, which normally is more caudal. Once the portal is made, digital inspection of the portal is performed to assure the lung is deflated and there are no adhesions. The camera is then inserted into the chest and additional portals are placed under direct visualization. Incisions are made at the predetermined positions as described above. The portals are 10.5 to 12.0mm in size. The ribs are counted to insure the correct levels are identified based on pre-operative plans.
The pleura is incised longitudinally along the entire length of the spine to be instrumented. The hook bovie is placed on the pleura over a disc and an opening is made. The hook is then inserted under the pleura and the pleura is elevated and incised. With this technique the pleura can be incised along the entire length without injury to the segmental vessels (Fig. 4). Suction is used to evacuate the smoke from the chest cavity. The pleura is then dissected off the vertebral bodies and discs, anteriorly off of the anterior longitudinal ligament and posteriorly off the rib heads using a peanut or endoscopic grasper (Fig. 5).
|Figure 4||Figure 5|
A K-wire is placed into the disc space and C-Arm images are used to confirm the level. The electrocautery is then used to incise the disc annulus (Fig. 6). The disc is removed in standard fashion, using various endoscopic curettes, pituitarys, cobbs, and kerrison rongeurs (Fig. 7, 8 a &b, and 9). Endoscopic shavers and rasps can also be used to assist in the discectomy.
|Figure 6||Figure 7|
|Figure 8A||Figure 8B|
Once the disc is completely removed, the anterior longitudinal ligament is thinned from within the disc space with a pituitary. The ligament is thinned to a flexible remnant that is no longer structural, but will contain the bone graft. Posteriorly the disc and annulus are removed back to at least the rib head. An angled pituitary can be used to remove annulus posterior to the rib heads in patients with stiff curves. The rib head should be left intact, at this point, since it will be used to guide screw placement. Once the disc has been evacuated, the endplate is then completely removed and the disc space can be inspected directly with the scope (Photo 7). The disc space is then packed with surgicell to control endplate bleeding.