Laparoscopic Transperitoneal Surgery for the Lumbar Spine

The ventral endoscopic approach is limited primarily to the L4-5 and L5-S1 disc spaces because of the relation of the aorta and vena cava to the spine. The increased use of minimally invasive abdominal and retroperitoneal procedures with the laparoscope initially paved the way for its use as an approach to the spine.

Despite limited enthusiasm for laparoscopic ventral discectomy for the treatment of simple disc disease, interbody fusion techniques initially received a warm welcome, as evidenced by the number of meeting presentations and papers on the topic. The procedure has evolved from the placement of morselized bone graft in the interspace to the use of structural interbody distraction cages to correct lordosis and facilitate indirect decompression of the neural elements. Despite initial results indicating shorter hospital stays, improved postoperative pain, and less postoperative ileus, other complications became apparent. Longer-term analysis of the laparoscopic versus mini-open techniques have revealed that there was a higher complication rate associated with the laparoscopic technique, including bowel perforation, ureteral injury, vessel injury, and others. Bateman and colleagues performed a meta-analysis comparing laparoscopic, mini-open, and retroperitoneal approaches to the lumbar spine and found that common complications encountered during this procedure were venous injury (3.2%), retrograde ejaculation (2.7%), neurologic injury (2%), and ileus (1.4%). This study also found that laparoscopic approaches were associated with higher complication rates than the mini-open approaches. Even before the publication of this paper, the laparoscopic technique had fallen out of favor and was largely replaced by the mini-open technique in North America. The laparoscopic technique is now a largely historical procedure; however, it is still utilized rarely in other parts of the world when a posterior approach may be contraindicated (i.e., in cases of severe fibrosis or wound infection). Detailed descriptions of the techniques can be found in other chapters in this book; however, a brief description of each can be found here.

The ventral exposure of the lumbar spine from the peritoneal cavity is limited to L5-S1 and variably to L4-5. Laparoscopic exposure is performed in the routine manner, similar to an intra-abdominal procedure. This includes a bowel preparation, insertion of a Foley catheter and a nasogastric tube, and preincisional prophylactic antibiotics. The patient is supine in the Trendelenburg position, with the back extended using large rolls under the lumbosacral junction ( Fig. 168-1 ). Insufflation techniques are standard, but a gasless technique also has been described, which does not require specially designed instruments. Assistance from a general surgeon comfortable with laparoscopy is advised.

The transperitoneal approach to endoscopic lumbar interbody fusion. Insufflation is maintained through the caudal portal, whereas dissection and instrumentation are performed through the portal directly aligned with the interspace.

Exposure of the L5-S1 space requires incision of the parietal peritoneum over the disc in the midline. Fluoroscopy is used to identify the disc properly. The midline sacral artery and vein must be divided. The parietal peritoneum is mobilized using blunt dissection, with bleeding controlled by bipolar electrocautery (rather than unipolar cautery), for fear of injuring the closely related autonomic plexus. At the L4-5 space, the exposure can be more difficult, because the disc space often sits at the crotch of the bifurcation of the great vessels. Gentle retraction of the common iliac vein and artery is required, and it may be necessary to sacrifice segmental branches. Inserting Steinmann pins into the L4 vertebral body to provide static retraction of the vessels may facilitate exposure.

Discectomy is performed by sharp incision of the ventral annulus fibrosus and by radical removal of disc material with curets and pituitary forceps. Fusion proceeds by distraction of the disc space and insertion of bone graft under compression. Threaded titanium cages are also utilized for anterior fixation and interbody fusion. This device has been cleared by the U.S. Food and Drug Administration and is commercially available for open procedures. The technique can be combined with the use of recombinant human bone morphogenic protein (rhBMP-2/InFUSE, Medtronic, Inc.), but it has been suggested that this potentially leads to higher rates of retrograde ejaculation.

With the laparoscopic placement of the graft, the procedure is outlined as follows: an estimate of graft size is made on the basis of the preoperative radiographs and specific templates provided by the manufacturer of the device. The sizes are checked in situ to confirm that adequate exposure is available. Next, a disc space distractor is placed on one side of the midline. On the other side, a circular hole is drilled (under fluoroscopic guidance to ensure a trajectory parallel to the vertebral end plates) to a depth of approximately two thirds of the diameter of the disc space. The hole is then tapped, and the titanium implant, filled with autologous bone chips or biologic +/− rhBMP-2, is screwed into the disc space. The distractor is then removed, and the tapping/implant procedure is repeated at the site previously occupied by the distractor. The implants should be sufficiently countersunk so that no aspect comes into contact with the overlying vascular structures. The exposure and anatomy may dictate that only one graft be placed. However, this is not as biomechanically sound as two cages, placed side by side, especially in lateral flexion. Currently, other materials such as threaded allograft dowels also are available for transperitoneal endoscopic fusion operations.

A retroperitoneal approach to the ventral aspect of the spine at levels L4-5 and L5-S1 with interbody fusion also is technically feasible, but difficult given the presence of the iliac crests. This reduces the chance of postoperative adynamic ileus and intra-abdominal adhesions. This approach also provides access to the lateral aspects of level L1-4, although the great vessels prevent midline access at these levels. Previous abdominal surgery is a relative contraindication for the laparoscopic transperitoneal exposure. This is not an issue with the retroperitoneal approach.

Complications associated with transperitoneal exposure are uncommon. However, they require immediate management by experienced abdominal surgeons. As the transperitoneal approach has gained popularity and familiarity since its inception, experience has grown rapidly. As previously stated, common complications encountered during this procedure can include venous injury, neurologic injury, ileus, and retrograde ejaculation (among others). Retrograde ejaculation has received much public attention due to its profound consequences and its association with the use of rhBMP-2 (InFUSE; Medtronic, Inc.). One study found the incidence of retrograde ejaculation to be as high as 7.3% with the use of rhBMP-2 versus 0.6% without its use; however, the controversy continues. It is recommended that, in men, reflection of the parietal peritoneum over the ventral disc space be performed with the aid of bipolar rather than monopolar electrocautery to prevent the spread of current and reduce the risk of damage to the autonomic plexus. If Steinmann pins are used, care must be taken during removal, as well as insertion, so that the sharp tip does not lacerate a vessel, particularly the iliac vein. The hazards of the approach, including drilling the disc space adjacent to the iliac vessels, are ameliorated with special instruments to protect the vessels during drilling. Familiarity with these instruments is imperative.

Dorsolateral Endoscopic Transpedicular Fixation

The dorsolateral approach is performed with the patient under general anesthesia and in the prone position. After a standard endoscopic discectomy, both end plates are decorticated. Using a pedicular jig, the guide pins are placed in the center of the pedicles under fluoroscopic control. A cannulated pedicle obturator is placed over the guidewire, and the soft tissues surrounding the pedicle are bluntly dissected. Pedicle screws are inserted under fluoroscopic control. The poly-axial screw heads are then connected using a curved rod.

The major advantages of this form of arthrodesis are the potential ability to use local anesthesia and the lack of blood loss when compared to open procedures. The major disadvantage is the limited exposure, which prevents the placement of oversized bone graft into the disc space under compression and prevents placement of ventral instrumentation. The result is limited ventral column support during healing. Furthermore, the percutaneous techniques are limited with regard to their ability to decompress the spinal canal and are contraindicated in the presence of a sequestered disc rupture.

Percutaneous Translaminar Facet Screw Fixation

Percutaneous translaminar facet screw fixation utilizing fluoroscopy has been successfully performed. The technique is often performed using computer-assisted image guidance. Shim and colleagues reported that this technique was a safe and useful minimally invasive dorsal augmentation method following transforaminal lumbar interbody fusion (TLIF), axial interbody fusion (ALIF), or AxiaLIF.

A technique that can be used to avoid bilateral muscle dissection and reduce operative blood loss and trauma during instrumentation following an MIS TLIF is depicted in Figure 168-2 . After interbody fusion, the technique is performed with minimal invasion using a dilating retractor tube system on the ipsilateral side of the exposure. Pedicle screws are then placed using direct vision, fluoroscopy, or image guidance on the ipsilateral side. Next, either AP and lateral fluoroscopy or three-dimensional image guidance equipment is used to place a 1.5-mm K-wire/guide through the contralateral lamina and the articular surface of the facet joint on the contralateral side. This wire is terminated at the base of the transverse process of the more caudal vertebra. This is done using a starting point at the junction of the spinous process and the lamina on the contralateral side. The intended trajectory is confirmed via fluoroscopy or image guidance, and a Jamshidi needle is secured in place with a mallet. The inner stylet is then removed and a K-wire is driven across the facet as described previously, again under direct visualization via fluoroscopy or image guidance. A cannulated 3.5- or 4.5-mm screw is then inserted over the guidewire. After placement of the screws, a rod is used to connect the pedicle screw construct.

Coronal ( A ), transverse ( B ), and sagittal ( C ) views of a contralateral translaminar facet screw and ipsilateral pedicle screw fixation construct, used to augment fixation after a two-level interbody fusion procedure. All instrumentation can be applied with minimal invasion via a unilateral paramedian incision and without contralateral muscle dissection.

An additional benefit of this technique is the ability to perform an MIS laminectomy from the side of the pedicle screw fixation if needed for patients with bilateral symptoms. In these cases, the facet screws should be inserted with a starting point that is slightly more superficial. This allows for adequate thinning of the contralateral lamina during the MIS laminectomy. This technique has been studied and validated both clinically and biomechanically and is a feasible posterior fixation technique to augment anterior interbody fusion techniques.

Axial Interbody Fusion

Axial interbody fusion (AxiaLIF; TranS1 Inc., Wilmington, NC) was developed in 2004 for L5-S1 interbody fusion, which was later expanded to L4-5 as well. The system uses a percutaneous paracoccygeal approach to access the presacral “safe zone” using a sequential dilating system, which allows for discectomy and placement of cancellous bone graft or a threaded rod through the disc space into the adjacent vertebral body. It was indicated for minor instabilities of the L5-S1 level, for L5-S1 discogenic pain, and for pseudarthrosis at L5-S1. It has been used alone or in combination with minimally invasive L5-S1 posterior fixation hardware. Early results using the system were encouraging. However, further long-term studies revealed problems with this device.

Although biomechanical studies initially indicated that the intact annulus contributes to AxiaLIF stability, the pitfalls of this technique are incomplete disc removal and insufficient end plate preparation. It is, therefore, difficult to add bone into the intervertebral disc space and hence to obtain bony fusion. Therefore, pseudarthrosis is a risk, and revision surgery for pseudarthrosis is reported in 8.8% by the 3-year follow-up period. Another study revealed that failure of fusion occurred in 23.5% of AxiaLIF cases. This product has since been removed from the market in North America.

Lumbar Interspinous Fixation and Fusion

A growing number of minimally invasive treatment strategies have been introduced for the treatment of degenerative spine disease since the early 2000s. Interspinous devices are also presented as a potential option for treating other lumbar pathologies ranging from discogenic low back pain to degenerative spinal stenosis and lumbar instability. Spine surgeons who employ these techniques must therefore understand the causes of each degenerative problem and determine the right treatment paradigm using all available experimental and clinical information. Some of the advantages of these procedures compared with standard surgical decompression techniques are the option to forego general anesthesia and use only local anesthesia, preservation of bone and soft tissue, reduced risk of epidural scarring and cerebrospinal fluid leakage, shorter hospital stay and rehabilitation period, and reversibility of the surgical procedure that does not limit future surgical treatment options. Currently there are no long-term clinical trials for these devices, and published clinical data consist of small, nonrandomized studies with short-term follow-up. Hence, the employment of these techniques should be carefully considered, using strict selection criteria.

Transforaminal Lumbar Interbody Fusion

In modern minimally invasive spine surgery, TLIF has become a mainstay of treatment for conditions that require fusion/fixation in the lumbar spine. The MIS TLIF was first introduced in 2002 by Foley and associates, and since then, numerous studies have shown equivalent or better clinical outcomes for MIS TLIF compared with traditional open TLIF. This minimally invasive approach has been shown to result in decreased tissue injury, less blood loss, decreased postoperative pain, shorter hospital stay, and faster recovery.

The technique has been described multiple times, sometimes with slight variation depending on surgeon preferences and whether image guidance or fluoroscopy is used. It is described in significant detail elsewhere in this book. A paramedian incision is made for the placement of a dilating tube retractor system to be docked on the facet capsule, which is followed by paravertebral transmuscular dissection, facet resection, discectomy, and cage placement. Percutaneous pedicle screws are placed unilaterally or bilaterally using fluoroscopy or image guidance. The placement of pedicle screws prior to performing the TLIF can allow the surgeon to apply some distraction to the interspace and facilitate the discectomy and cage placement.

After the initial introduction of the MIS TLIF, the upper and lower lumbar vertebrae were commonly instrumented only by ipsilateral pedicle screws. Initial studies demonstrated good outcomes with this unilateral fixation; however, subsequent studies suggested that these unilateral fixation constructs provided insufficient support in lateral bending and rotation, leading ultimately to instrument failure and nonunion. Other studies reported no difference in fusion rates, and a subsequent meta-analysis also failed to show a significant difference in fusion rates between unilateral and bilateral fixation. The current standard practice is to place bilateral pedicle screws to provide posterior fixation of the construct.

There are some potential complications from MIS TLIF operations, which are shared with those from traditional TLIF operations. They include, but are not necessarily limited to, allograft malposition, pedicle screw malposition, infection, cerebrospinal fluid leak, hematoma formation, and postoperative anemia.

Each approach also carries its own set of unique complications. Complications that are more likely to be found after a traditional open TLIF include higher rate of infection, muscular trauma, dural tears, postoperative ileus, and atelectasis. In contrast, open TLIF has been associated with a lower rate of neurologic injury compared to the minimally invasive technique, likely due to greater visualization of the surrounding structures.

MIS surgeons are familiar with the challenging learning curve associated with the MIS techniques, and early in one’s career, complications related to this learning curve are more common. These mistakes are often related to instrumentation, sometimes resulting in neurologic deficit. Visualization through the tubular dilator can be limited and result in inadequate decompression or neural injury during graft placement. In one meta-analysis, nearly one in five of the reported complications from MIS TLIF were neurologic complications.

Radiation exposure is another area that is of interest to MIS surgeons performing this technique. Significant amounts of radiation can be encountered during these operations when performed without the assistance of image guidance software. The amount of radiation has not been quantified, but it can be high. Contrary to popular belief that radiation exposure decreases as experience increases, one study observed no significant difference in radiation exposure as experience with the procedure increased.

Minimally Invasive Lateral Approach for Lumbar Interbody Fusion

The minimally invasive lateral approach for lumbar interbody fusion (XLIF, NuVasive, Inc.) or direct lateral interbody fusion approach (DLIF, Medtronic Sofamor Danek) was first presented in 2006 by Ozgur and colleagues. Currently, most spinal instrumentation vendors offer an MIS lateral system. This technique is a modification of a retroperitoneal approach to the lumbar spine, which was first presented in 2001 by Pimenta and his colleagues. It allows for access to the lateral aspect of the lumbar vertebrae to treat degenerative disc disease and to perform lumbar interbody fusions, without the need for an access surgeon. The approach was also used for far lateral disc herniations, placement of artificial discs, and was expanded to place interbody grafts at multiple levels—thus allowing for significant correction of coronal plane deformities.

Several large series have alluded to the advantages of this approach. These include less tissue dissection, smaller incisions, decreased operative time, blood loss, shorter hospital stay, reduced postoperative pain, enhanced fusion rates, and the ability to place instrumentation through the same incision. Indications for this approach have increased and now include degenerative disease, tumor, deformity, and infection.

The technique will be discussed in greater detail elsewhere in this book, but the basic description of the procedure is as follows: The patient is placed in the lateral decubitus position (usually left side up, but can be either side). Neuromonitoring, including electromyography (EMG), is mandatory, because it employs a muscle-splitting technique that exposes the lumbar plexus to potential injury. Injury to the lumbar plexus is one of the main risks of this technique and has been reported in multiple studies to date, with an incidence as high as 33% in one series.

A 3- to 4-cm incision is made on the flank overlying the intended disc space. Through a smaller, posterior incision, the surgeon’s finger directs the first dilator to the surface of the psoas muscle, taking care to stay out of peritoneum and away from the viscera. This initial dilator then splits the psoas muscle and docks on the lateral annulus of the disc. The neuromonitoring is crucial at this step, as it will detect the proximity of the lumbar plexus and tell the surgeon if the dilator is in an adequate position.

Progressively larger dilators are then inserted over the first until the desired access is obtained. The retractor is then affixed to the operating table and neuromonitoring is again checked. Once complete, the discectomy can be performed, followed by placement of the interbody graft and instrumentation, if needed, as was previously described by Ozgur and colleagues.

Because of the proximity of the lumbar plexus to the working area of this operation, knowledge of the anatomy is critical. Numerous cadaveric, electrical, and radiographic studies have been performed to define a safe “working zone” for the retractor system depending on the desired level. These studies have indicated that when approaching the lumbar vertebral bodies and interspaces of L1-3, the psoas muscle should be split in the ventral three quarters of the body to avoid nerve injury. The lumbosacral plexus is most dorsally located at L1-2 and progressively migrates ventrally from L2 to L4-5. Therefore, if the dilator or retractor is placed posteriorly on the disc space, especially at L4-5, there is a high risk of nerve injury.

Other potential complications from this procedure can include visceral/large vessel injury (if the peritoneum is inadvertently entered), ureteral damage, dural tear, and hardware-related complications that are common in other fusion operations.

Most XLIF/DLIF procedures are performed in the lumbar spine. The L5-S1 disc space is usually inaccessible due to the presence of the iliac crest. The L4-5 interspace is obscured 50% of the time as well. The remainder of the lumbar spine is usually accessible. Advances have suggested that this procedure is applicable to lesions in the thoracic spine and thoracolumbar junction as well. This technique is similar to that performed in the lumbar spine, with a few significant differences. Although neuromonitoring is still used routinely, the distance from the lumbar plexus makes the likelihood of injury during placement of the retractor highly unlikely. The neuromonitoring is used to identify injury and prevent further injury to the thoracic spinal cord. Second, in order to access the thoracic spine, the thoracic cavity must be entered. This can be done either by spreading between the ribs (one level access) or by removing a 5- to 6-cm section of rib (for two-level access or for corpectomy). After entering the chest cavity, the surgeon uses a finger to sweep the lung ventrally to allow the retractor system access to the disc space. At T12-L1 and L1-2, it is often necessary to cross the diaphragm. In these cases it is important to open the diaphragm at its junction with the chest wall to allow for repair at the end of the case.

The discectomy and interbody strut placement is again performed as previously described. The wound is then closed in a layered fashion, over a closed-suction chest tube. In most cases the chest tube is removed within the first 1 to 2 postoperative days.

The potential complications from this expanded application of the XLIF/DLIF technique into the thoracic spine include those that are common after thoracotomy or thoracoscopic procedures. They include delayed pneumothorax, diaphragmatic hernia, major vascular injury, and rib pain. This is in addition to the common complications from any other spine surgery (i.e., durotomy, infection, cardiopulmonary problems, or hardware problems). One important point is that studies from the adolescent idiopathic scoliosis population have shown less effect on pulmonary function when minimally invasive techniques are used rather than open thoracotomy to access the adolescent spine. Although this makes sense from a clinical standpoint, the significant difference between XLIF/DLIF and thoracoscopic approaches is that XLIF/DLIF allows the surgeon to avoid prolonged periods of having one lung deflated, which is often required during a thoracoscopic approach or a thoracotomy. This leads to less atelectasis and may be particularly beneficial to the scoliosis population, where restrictive lung disease can be a significant risk to long-term health after spine surgery.

The anatomic features of different regions of the spine dictate a variety of endoscopic approaches for fusion and stabilization. A thoracic spine endoscopic approach necessitates VATS, whereas lumbar spine instability requires a ventral approach, a lateral approach, a dorsolateral approach, or a combined approach. The choice of endoscopic technique in the lumbar spine is guided largely by a patient’s specific condition and by surgeon preference.