Trocars

Reusable, flexible, threaded trocars that are black with a diameter of 11 mm are used to reduce light reflections and the pressure on the intercostal nerves and vascular bundle. Air insufflation is not required, and thus valves within the trocars are not necessary.

Image Transmission

The key to any endoscopic technique is image recording and transmission. “You will do what you can see,” and therefore true high-definition video technique has also revolutionized the endoscopic technique, which now provides an endoscopic view comparable to images that the microscope is able to provide. A high-intensity xenon light source is required to illuminate the thoracic cavity. A rigid, long, 30-degree scope enables positioning of the camera far away from the working portal, thus facilitating undisturbed working and variable adjustment of the angle of vision. The intraoperative view is transmitted onto two or three flat screens (Fig. 31-1).

FIGURE 31-1 Thoracoscopic surgery at the spine: all portals, the 30-degree scope, and the instruments are inserted. The surgical team is looking at three high-definition flat screen monitors.

Instruments

Complete sets of instruments for soft tissue and bone preparation are manufactured by contemporary instrument manufacturers (Fig. 31-2). Instruments should have a nonreflective surface and a depth scale on both sides and be ergonomically designed with big handles for safe control and handling. The technique by which they are used is called the three-point anchoring technique, which means that every sharp and potentially dangerous instrument is guided by both hands; one hand is based on the chest wall, always controlling and sometimes neutralizing unexpected forces and movements of the instrument (see Video 31-9).

FIGURE 31-2 A whole set of long instruments for endoscopic soft tissue preparation and bone resection and devices for thoracoscopic implantation of a stabilizing implant are prepared to be used for the thoracoscopic procedure.

Implants

Several implants for anterior instrumentation that can be used for endoscopic, mini-open, or open spine surgery are now available. Most of them are based on the principle of a cannulated screw and plate system, first allowing the implantation of K wires under fluoroscopic control to be used as landmarks, followed by the insertion of screws. Biomechanically tested four-point fixation implants provide adequate angular stability, which is necessary for single anterior instrumentation (Fig. 31-3).¹³

FIGURE 31-3 Screw and constraint plate implant for endoscopic and open instrumentation at the anterior column of the thoracic and lumbar spine (MACS TL, Aesculap, Tuttlingen, Germany).

For vertebral body replacement, bone graft (autograft or allograft) or mechanical devices can be used and filled or surrounded with the autologous bone harvested from the corpectomy site. A wide variety of expandable titanium cages is currently available.¹⁴

Education of the Patient

The patient should be informed about the following approach-specific risks and hazards:

Anesthesia

A pulmonary function test and breathing therapy are commonly performed preoperatively to assess the patient’s vital parameters. Routine bowel preparation is commonly used to decrease intra-abdominal pressure and tension on the diaphragm. The thoracoscopic operation is performed under general anesthesia. Double-lumen tube intubation and single-lung ventilation are applied as routine. Proper placement of the endotracheal tube is confirmed by bronchoscopy. A Foley catheter, central venous line, and arterial line for continuous blood pressure assessment are placed. For postoperative pain relief, a peridural analgesic is inserted in the thoracic region.

Positioning of the Patient

All endoscopic operations at the anterior column of the thoracic spine and the thoracolumbar junction are performed with the patient lying on his or her side (Video 31-1). The approach side is determined by the preoperative computed tomographic (CT) scans and depends on the position of the major vessels shown in the scans and the surgery that is planned. Because of the great variability of the vascular anatomy, firm rules are no longer set for selection of the approach side by the height of the lesion.

The patient is stabilized in the side-lying position with four supports and a special U-shaped cushion for the legs. It is possible to use a vacuum mattress, but its construction height can make the manipulation of instruments under C-arm control and conversion to the open procedure more difficult.

Marking the Portals

As a routine, four portals are used: scope portal, working portal, suction-irrigation portal, and retractor portal (Video 31-2). Their location and, in particular, the position of the working portal are crucial for the endoscopic operation to proceed in the optimal fashion. For this reason, the lesion is first displayed in the lateral projection (with reference to the patient’s body) under precise adjustment of the image intensifier, and a marker is used to draw the injured spinal section onto the lateral thoracic wall (Fig. 31-4). The working portal is drawn in directly above the lesion. The trocar for the endoscope is marked either caudal or cranial to the working portal, depending on the height of the lesion, and following the axis of the spine. The distance from the working portal is approximately two intercostal spaces. The entry points for suction and irrigation and for the retractor are then located ventral from these portals.

FIGURE 31-4 With the patient placed in a true lateral position, the affected section of the spine is accurately projected to the lateral thoracic and abdominal wall and marked with use of a C-arm amplifier.

After skin disinfection and sterile draping, single-lung ventilation is begun in consultation with the anesthetist. As the first approach, the portal in the farthest cranial position is always selected because the risk of injury to the liver, spleen, and diaphragm is comparatively minor in this position. The approach is made by the mini-thoracotomy technique, providing the possibility of examining the immediate surroundings of the insertion site with the fingers before the trocar is introduced (Video 31-3). The rigid 30-degree endoscope is then carefully inserted, and the thoracic cavity is first inspected to rule out the existence of adhesions or parenchymal lesions. The other three trocars and then the instruments are subsequently introduced under endoscopic control.

Approach to the Thoracolumbar Junction

This operation is also performed using single-lung ventilation (Video 31-4).^8,11,15,16 Here, too, the approach side is decided by the location of the major vessels, which can be identified from the preoperative computed tomographic scan. In most cases, the best approach to the thoracolumbar junction is from the left. Placement of the trocars and instruments is illustrated in Figure 31-5.

FIGURE 31-5 Placement of the trocars and instruments for an endoscopic intervention at the thoracolumbar spine.

As a first step, the affected section of the spine is drawn onto the skin of the lateral abdominal and thoracic wall under image intensifier control. Careful attention is paid to correct projection of the vertebrae, whose end plates and anterior and posterior margins should be displayed in the central beam, in sharp focus with no double contour. This marking is taken as the sole reference for subsequent placement of the portals.

The working portal is situated directly above the lesion; the portal for the endoscope is located over the spine two or three intercostal spaces away from the working portal in a cranial direction. The portals for the retractor and the suction-irrigation instrument are situated ventrally from this point.

The dome-like diaphragm is firmly connected at its margins with the sternum, ribs, and spine and arches up into the thoracic cavity. Topographically speaking, the attachment sites of the diaphragm to the spine are at the level of the first lumbar vertebra, whereas the lowest point of the thoracic cavity projects with the phrenicocostal sinus at the level of the baseplate of the second lumbar vertebra (Fig. 31-6). This makes it possible to place a trocar intrathoracically in the phrenicocostal sinus, which, after incision of the diaphragm attachment to the spine, provides access to the retroperitoneal section of the thoracolumbar junction down to the baseplate of the second lumbar vertebra. This requires a 4- to 5-cm–long incision following the attachment of the diaphragm; access to the L1-2 intervertebral disk can be obtained with a shorter incision of 2 to 3 cm (Fig. 31-7).^15–17

FIGURE 31-6 Typical operation site at the thoracolumbar section of the spine. The interrupted line runs parallel to the attachment of the diaphragm and indicates the line of incision for access to the subdiaphragmatic section of the thoracolumbar junction, L1, and L2.

FIGURE 31-7 Partial detachment of the diaphragm reveals the retroperitoneal fat, the anterior border of the psoas muscle, and the spine. A fan-shaped retractor is inserted into the diaphragm gap.

To prevent a postoperative diaphragmatic hernia, an incision that runs parallel to the diaphragmatic attachment is preferred. Because of the dome-like architecture of the diaphragm, an increase in intra-abdominal pressure from a semicircular incision parallel to the attachment causes the resected margins to come together and to adhere spontaneously, whereas a radial incision in direct proximity to the orifices of the aorta and the esophagus weakens the diaphragm fixation and causes the resected margins to gape. In addition, it is recommended that every incision in the attachment longer than 2 cm be sutured endoscopically to prevent hernia formation.

Endoscopic Treatment of Spinal Trauma (Anterior Reconstruction)