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)

Ventral Instrumentation with a Constraint Plate Implant

Because the screws and so-called clamping elements belonging to the implant were placed into position as a first step before the beginning of the partial corpectomy, now the plate just has to be fastened and the ventral screws of the four-point fixation inserted (Video 31-11).

The distance between the screws is defined with a special measuring instrument to select a plate of the correct length. This is introduced lengthwise into the thoracic cavity through the incision for the working portal, laid onto the clamping elements with a holding forceps, and there definitively fixed with nuts with a starting torque of 15 Nm. The plate can be brought into direct bone contact with the lateral vertebral body wall by tightening the bone screws. The ventral screws are inserted after temporary fixation of a targeting device and opening of the cortex. Because of the heart shape of the vertebral body, the ventral screws are usually 5 mm shorter than the dorsal screws. The fixation of the angle-stable implant ends with the insertion of a locking screw that locks the polyaxial mechanism of the dorsal screws (Fig. 31-8).

FIGURE 31-8 Thoracoscopic anterior instrumentation with a four-point stabilization constraint plate and screw system.

Removal of Posterior Wall Fragments: Endoscopic Anterior Decompression⁹

Depending on the level of stenosis, compression of the spinal canal can lead to a neurological deficit. The spectrum of injuries to the spinal canal, medullary cone, and cauda equina ranges from simple contusion to complete tearing of the neural structures. As long as the structures have not been severed, recovery of function and sensory deficits may be possible in principle. Thus, the indications for anterior decompression are present when significant narrowing and a neurological deficit remain after primary dorsal reduction and stabilization.

Operative Technique

Completion of the partial corpectomy and adjacent diskectomies is recommended before the canal decompression. The next step is to identify the pedicle of the fractured vertebral body. In traumatic burst fracture, the pedicles are nearly always preserved, and the retropulsed fragment usually is located medial to the pedicle. Thus, the retropulsed fragment is trapped between the two pedicles and is difficult to remove or reduce.

Therefore, resection of the ipsilateral pedicle with a punch is recommended before removal of the retropulsed fragment is attempted. For this reason, resection of the ipsilateral pedicle has a dual importance: it exposes the spinal canal, and it frees the retropulsed fragment from the pincer grip of the pedicles. A Cobb elevator is used to expose the ipsilateral pedicle subperiosteally and to push away the nerve root dorsally without having separated the root from the surrounding soft tissue. The inferior margin of the pedicle is identified with a nerve hook, and the pedicle is transected with a punch, which can be facilitated by thinning the pedicle with a high-speed bur beforehand. Removal of the dorsocranial section of the vertebral body together with the base of the pedicle exposes the posterior margin fragment and brings the dura into view. The compressing fragment can now be lifted off the dura under direct view, mobilized in the direction of the partial corpectomy, and resected. A nerve hook is used under image intensifier control to document the completeness of the posterior margin fragment resection in both planes. In cases with posterior wall resection, an expandable titanium cage is used as a vertebral body replacement because of its greater primary stability and the smaller risk for dislocation. The operation concludes with the ventral instrumentation and suturing of the diaphragm attachment.

Case Report

A 43-year-old man was referred to our hospital demonstrating severe back pain at the thoracolumbar junction, weakness of the lower extremities below T12, and moderate bowel and bladder dysfunction. After radiologic diagnostics and neurological examination, the patient was brought to the operating room for dorsal reduction and stabilization by internal fixator followed by thoracoscopic anterior decompression and reconstruction (Figs. 31-9 to 31-11).

FIGURE 31-9 L1 complete burst fracture type A 3.3 with severe compromise of the spinal canal causing neurological deficit Frankel C.

FIGURE 31-10 Immediate dorsal reduction and stabilization by internal fixator to achieve indirect decompression by ligamentotaxis.

FIGURE 31-11 Thoracoscopic reconstruction of the anterior column with anterior decompression (i.e., posterior wall resection, vertebral body replacement, and anterior instrumentation).

Removal of Protruded Herniated Disk: Endoscopic Treatment of Degenerative Disk Disease

Only 0.15% to 1% of all operative procedures due to degenerative disk disease are done to treat thoracic disk protrusion.^18–20 As a specialty of the thoracic region, there is a “calcified disk” and an “intradural disk herniation” (Fig. 31-12). These removal procedures are technically demanding. Because of a smaller diameter of the thoracic spinal canal in conjunction with a spinal cord of bigger volume at these levels, there is little space to accommodate disk herniation. In consequence, small disk protrusions might cause significant symptoms. Depending on the localization and expansion of herniation—medial, mediolateral, intraforaminal, or extraforaminal—typical symptoms of thoracic disk herniation can be described.

FIGURE 31-12 Calcified herniated disk at the level of T9-10 with severe narrowing of the spinal canal and cord in a 54-year-old woman, causing myelopathy and belt-like back pain.

Operating Room Setup

Positioning the Patient

The side for the approach has to be chosen primarily by the localization of the disk herniation and the adjacent great vessels. In cases of centromedial and right lateral herniation, the approach from the right side is preferred (Fig. 31-13).

FIGURE 31-13 The affected segment is marked onto the right chest wall before the endoscopic procedure is started. The working portal will be placed directly above the pathologic process; the 30-degree scope will be inserted from below.

Confirmation of the Operative Site

Verification of the level of disease can be demanding before the main procedure is started. Several methods are recommended to ensure that the right intervertebral disk space is addressed. Dickman and Rosenthal¹² recommend a preoperative radiograph of the chest to localize the level. Large osteophytes seen on computed tomographic scans or plain radiographs can be used as surgical or radiographic landmarks. After the endoscopic procedure has started, it is recommended that the ribs be counted with use of the C-arm, beginning caudally at the 12th rib. Rib identification should be repeated several times to ensure accuracy. The pleura over the identified rib head is then cauterized. Attention must be paid to the patient with an abnormal number of ribs, because the spinal level could be misidentified.

Marking the level of interest by percutaneous placement of a tiny metallic marker that is CT guided simultaneously with to the preoperative CT scan might be the most accurate way to identify easily and reproducibly the correct level during the operative procedure (Meic H. Schmidt, University of Utah, personal communication).

Operative Technique

The general principle of the procedure is to resect the rib head of the adjacent rib and expose the pedicle and the affected intervertebral disk (Fig. 31-14). A block-shaped defect will then be created in the adjacent vertebral bodies for removal of soft and calcified disk material away from the dura into the defect. Afterward, the rib head, which usually fits into the defect, is used for a monosegmental fusion procedure to be accomplished by ventral instrumentation.

FIGURE 31-14 Mobilization of the rib head for access to the disk T9-10 and the pedicle T10.

Technical and Operative Details

A lateral fluoroscopic picture is obtained to determine the level of disease and the position of the four portals. The working portal is outlined directly over the affected intervertebral space. After the approach has been made and all portals are put in the right position, the spine is exposed by retraction of the lung with the fan-shaped retractor. The pleura over the identified and confirmed rib head is cauterized.

At this point, K wires are inserted (C-arm guided) according to the implant system that is used for stabilization and fusion afterward as landmarks into the vertebral bodies above and below the level selected for diskectomy. However, the procedure includes partial removal of the disk combined with a more or less extended bony defect at the adjacent vertebral bodies; distinct instability can be expected. Therefore, a monosegmental fusion with anterior instrumentation is advised.

After trap-door incision of the pleura over the identified disk space and the adjacent one, the segmental vessels of at least the lower adjacent vertebra are prepared, ligated with clips, and transected. If mobilization of the aorta is needed, the segmental vessels are ligated and dissected at multiple levels. The capsular and ligamentous structures of the rib head are cut with a Cobb elevator, and the rib head is mobilized. Following the course of the proximal rib, the pleura is opened over the rib, and the proximal 2 cm of the rib is resected. The rib head is preserved and used as bone graft for later fusion. The pedicle can now be exposed, identifying the neuroforamen above and below.

Partial corpectomy is performed with a high-speed diamond bur or an osteotome, creating a well-defined, block-shaped central defect involving the upper and lower thirds of the adjacent vertebral bodies. Initially, the posterior vertebral body wall is preserved (Fig. 31-15).

FIGURE 31-15 Partial corpectomy T9 and T10 with a high-speed bur to create a defect in the vertebral bodies in front.

Once the base of the pedicle caudal to the intervertebral disk space is identified, the thickness can be reduced with a diamond bur to weaken the pedicle and to facilitate the transection with Kerrison rongeurs. Dickman¹² recommends starting at the upper rim of the pedicle because of less bleeding from the epidural venous plexus. Under direct endoscopic view of the dura, the posterior wall is then dissected off the dura and carefully pushed into the corpectomy site or thinned out with a high-speed diamond bur. The sequestered part of the disk is then removed with dissectors and rongeurs. If there is an intradural calcified herniated disk, the intradural part of the sequestrated disk has to be carefully separated from the arachnoid mater with microdissection (Fig. 31-16). Even if this is not possible without tearing the dura, the base of the calcified disk can be thinned with the diamond bur, leaving only a shell of calcification attached to the dura free to move without bone or soft tissue impingement. Complete decompression of the dural sac across the vertebral body to the level of the contralateral pedicle is confirmed by direct endoscopic view and radiologically by fluoroscopy with use of a nerve hook in an anteroposterior projection. After decompression, the dura is covered with Gelfoam. The corpectomy defect is reconstructed with the rib head harvested at the first step. The size of the graft is determined with an endoscopic measurement of the defect.

FIGURE 31-16 After the pedicle T10 has been dissected, the posterior vertebral wall including the calcified herniated disk is carefully dissected from the dura and pushed into the vertebral defect in front.

I routinely perform a monosegmental endoscopic anterior fixation with a constrained screw-plate system to achieve a solid bony fusion of the segment.