Posterolateral Endoscopic Lumbar Discectomy

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CHAPTER 59 Posterolateral Endoscopic Lumbar Discectomy

Christopher A. Yeung, MD, Anthony T. Yeung, MD

Posterolateral endoscopic lumbar surgery is a less invasive surgical procedure to address lumbar pathology in the disc and boney foramen. Like any surgical procedure, it is based on visual identification and exposure of the target pathology and adequate surgical tools to address the offending pathology. Modern day endoscopic technology allows for visualized discectomy and decompression of the traversing and exiting nerve roots from a percutaneous posterolateral/transforaminal approach. This is safe and equally efficacious to microscopic discectomy in properly selected patients.1–4 Recent advances also allow for bony decompression of foraminal stenosis.5,6

Advances in the ability to perform endoscopic discectomy have paralleled other specialties, yet percutaneous spinal surgery has not met with the same peer recognition as the other fields. This is due in part to the high success rate and relative low morbidity of the current gold standard, posterior microscopic lumbar discectomy. However, this approach still requires a 1-inch midline incision, significant muscle and ligament stripping, prolonged muscle retraction, partial facet and lamina resection, and both nerve root and dura retraction. This can weaken the muscular lumbar stabilizers, create instability and facet arthrosis, cause traction neuropraxia, promote epidural scarring, and make revision surgery more difficult.

Another barrier for more widespread adoption was the relative paucity of peer-reviewed literature, and critics noted that only a few authors were contributing to this body of literature. Recently, there have been many more published results of posterolateral endoscopic discectomy from around the world and the preponderance of evidence supports its efficacy.

Numerous other nonvisualized percutaneous techniques often get categorized and confused with posterolateral endoscopic lumbar discectomy. These include automated percutaneous lumbar discectomy (APLD), percutaneous laser discectomy, and percutaneous discectomy with the Dekompressor or Arthrocare wand (Coblation). These are all fluoroscopically guided nonvisualized procedures that access the disc via the same posterolateral approach as endoscopic lumbar surgery. The underlying principle of these procedures is that through central nucleus removal or ablation, intradiscal pressure can be substantially lowered. This was based on the work of Hirsh and his postulated relationship between intradiscal pressure, disc herniation, and low back pain. He hypothesized that lowering this pressure in an injured disc could be efficacious in the relief of sciatica.7 Multiple studies described decreases in intradiscal pressures of 50% or greater.8–10

The results of these types of indirect decompressive procedures have been similar with initial favorable reports. However, subsequent studies have shown varying degrees of success. The inability to consistently see the decompressed nerve or the targeted patho-anatomy has limited the use of these nonvisualized decompressive procedures.11–14 It is unfortunate that these procedures, and their results, are mistaken for posterolateral endoscopic discectomy.

History

The basis for percutaneous lumbar disc procedures came from accepted posterolateral percutaneous biopsy techniques of the lumbar vertebrae. These procedures were initially performed with the use of a Craig needle to perform a posterolateral biopsy for neoplastic conditions.15,16

Minimal access surgery for lumbar disc herniation was first independently reported by Kambin and colleagues17 and Hijikata18 in 1975. The technique used a posterolateral approach to the foraminal zone of the disc bordered by the traversing nerve dorsally, the exiting nerve ventrally, and the endplate of the inferior vertebra caudally. The goal was to decompress nerve roots secondary to lumbar disc herniation by the “inside-out technique” of central and posterior nuclectomy and fragmentectomy. Advances in technique and instrumentation since Kambin, however, have allowed the surgeon to also enlarge the medial or lateral foramen by decompression of the lateral and ventral portion of the facet joint complex to reach the midline of the disc and the epidural space. Thus it is feasible to treat the full spectrum of disc herniations with advanced endoscopic instrumentation and techniques that can either target the extruded fragment directly or with a combination of the “inside-out technique.”19

The early efforts were limited to a nonvisualized central discectomy to achieve an indirect decompression of the nerve roots,17,18,20 but improvements in surgical equipment and technique evolved gradually over the next 30 years. In the past 10 years, the important major equipment improvements have included various-sized high-resolution rod lens operating endoscopes with variable-size working channels, beveled and slotted cannulas, flexible shavers and pituitary forceps, a bipolar flexible high-frequency/low-temperature radiofrequency (RF) electrode, multidirectional Holmium Yttrium-Aluminum-Garnet lasers, and high-speed diamond burrs and motorized shavers to decompress the foramen.19 An improved fluoroscopically guided approach method introduced by Yeung and reported by Tsou21–23 outlined a consistent and safe technique for entry into all lumbar posterior disc spaces including the L5-S1 level. This specific technique has been termed selective endoscopic discectomy (SED) but can be classified under the more general descriptive term of posterolateral endoscopic lumbar discectomy (PELD) that other authors describe.

These refinements have enhanced the capabilities of foraminal endoscopic discectomy to deliver surgical results similar to the results obtainable by traditional transcanal approaches for treating common lumbar disc herniations.1–4

Minimal access posterolateral endoscopic intradiscal visualization with the available operating tools has introduced new operative capabilities. That includes foraminal decompression for more central access of disc herniations and selective nuclectomy and annuloplasty performed intradiscally. The process of foraminal decompression also decompresses the lateral recess in lateral recess stenosis and mild central canal stenosis, a common late sequela of lumbar discectomy.

Anatomy

Posterolateral endoscopic lumbar surgery is performed through what has been named the triangular working zone, or Kambin’s triangle (Fig. 59–1). This triangular zone is defined as a safe zone in the posterolateral annulus between the exiting and traversing nerve roots. The exiting nerve root forms the anterior border of the triangular zone as it exits under the cephalad pedicle. The superior endplate of the caudal vertebral body forms the inferior border and the articular process and superior articulating facet of the caudal vertebra form the posterior border. The working zone is bordered medially by the traversing nerve root and dura. From cadaveric measurements it was determined that cannulas ranging from 4 mm to 10 mm could be safely used in the triangular working zone.24–27 A thorough understanding of the three-dimensional anatomy is necessary to understand and perform posterior percutaneous lumbar surgery.

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FIGURE 59–1 Triangular working zone at L4-5 (Kambin triangle). This is the access point for posterolateral disc access. The exiting nerve root is the hypotenuse of the triangle, the superior endplate of the caudal vertebral body/sacrum is the base (width), and the traversing nerve root/dura is the height of the triangle.

Endoscopic Lumbar Discectomy

Endoscopic surgery developed out of fluoroscopically guided percutaneous procedures that initially used a working cannula with modified instruments designed for disc removal. The first surgeon credited with percutaneous nucleotomy was Hijikata in 1975.18 The evolution of endoscopic techniques followed a series of transitions. Initially, an arthroscope was used to inspect the disc and annulus intermittently through the cannula while the mechanical nuclectomy was done under fluoroscopic guidance. The introduction of a biportal approach allowed for direct visualization of instruments introduced through a cannula inserted into the disc from the opposite posterolateral portal. The later development of an operating spine scope with a working channel allowed for surgical removal of disc material and visualization of foraminal anatomy under direct visualization via a uniportal approach.

Parviz Kambin performed the first true endoscopic lumbar procedures. The arthroscope was at first used intermittently through the working cannula. At certain stages of the procedure such as perforating the disc in the triangular working zone, the arthroscope would be placed in the cannula. The nonworking channel scope was used for identification of the annulus and periannular structures. The basis was to see that the nerve was not in the way before advancing the cannula. Once the cannula was safely within the disc, the nucleotome, an arthroscopic shaver, and pituitary rongeurs were passed through the cannula to perform mechanical disc removal. The majority of the procedure was only fluoroscopically visualized.17 Kambin reported an 88% success rate in his first 100 patients.28,29

The early endoscopic procedures were limited by the absence of a working channel arthroscope. This led Kambin to the development of a biportal technique in which the scope was inserted on one side and the working cannula on the opposite side. Kambin’s indications for a biportal approach included large subligamentous herniations, extraligamentous herniations, and arthroscopic interbody fusion.26 In later studies Kambin reports results from both uniportal and biportal procedures together. Overall results ranged from 85% to 92% satisfactory results at a minimum 2-year follow-up. There was no differentiation made between the results of uniportal versus biportal approaches.30–32

Kambin’s first prototype of the working channel scope was not fully developed and was not successfully marketed. The problems with the initial scope included fragility, limited degree of angulation for the working instruments, and the inability to establish sufficient inflow or outflow for adequate visualization.33 Anthony Yeung developed the first working channel endoscope to become widely available. The scope was developed in 1997 and was approved for use by the U.S. Food and Drug Administration in March 1998. The Yeung Endoscopic Spine Surgery (YESS) system (Richard Wolf Surgical Instruments, Vernon Hills, Ill.) modified the scope by adding multichannel integrated irrigation, specialized beveled cannulas, a two-hole obturator, and newly designed discectomy tools that allowed for constant real-time visualization with a uniportal technique.34 (Fig. 59–2)

image

FIGURE 59–2 The Yeung Endoscopic Spine Surgery system.

(Courtesy Richard Wolf Surgical Instruments, Vernon Hills, Ill.)

Another major change, which allowed for advancement in the field of endoscopic spinal surgery, was the emphasis on placement of the cannula closer to the epidural space and the base of the targeted disc herniation. This enabled surgeons to target extruded herniations in addition to contained herniations. Previous percutaneous modalities all focused on entry through Kambin’s triangle and working within the center of the disc with the cannula anchored inside the annulus. The cannula was advanced past the annulus and remained there under fluoroscopic control. Mathews’ transforaminal approach for microdiscectomy allowed for routine visualization of the epidural space and greater access to the traversing nerve root.35

The development of a working channel scope and use of the transforaminal approach using beveled and slotted cannulas enhanced endoscopic lumbar surgery. Using this approach, surgeons can operate under full visualization throughout most of the procedure and follow the neural structures into the epidural space. The specialized cannulas provide greater access to pathology and help protect and retract sensitive anatomy such as the exiting nerve and dorsal root ganglion. The working channel also allowed the passage of high-speed burrs for bone removal and direct foraminal enlargement and decompression of foraminal stenosis (foraminoplasty) (Fig. 59–3).

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FIGURE 59–3 Protocol for optimal needle placement. A, Posteroanterior (PA) fluoroscopic view enables topographic location of the midline and the transverse disc plane. The intersection of these lines is the PA anatomic disc center. B, Lateral fluoroscopic view enables topographic location of the disc inclination plane. C, The inclination plane of each target disc is drawn on the skin from the lateral disc center. D, The distance from the lateral disc center to the posterior skin plane is measured along the inclination plane. E and F, This same distance is measured from the midline along the transverse disc plane for each target disc. At the end of this measure a line parallel to the midline is drawn to intersect the disc inclination line. This is the skin entry point or “skin window” for the needle.

Indications/Contraindications

Current indications for the use of an endoscopic posterolateral approach to the lumbar spine include foraminal and far-lateral disc herniations, contained central and paracentral disc herniations, small nonsequestered extruded disc herniations, recurrent herniations, symptomatic annular tears, synovial cysts, biopsy and débridement of discitis, decompression of foraminal stenosis with or without spondylolisthesis, visualized total nuclectomy (before nucleus replacement), visualized discectomy, and endplate preparation before interbody fusion.

Perhaps the ideal lesions for posterolateral selective endoscopic discectomy are the foraminal and extraforaminal disc herniations. The cannula inserts directly at the herniation site, and the exiting nerve is routinely visualized and protected. This approach requires less manipulation of the exiting nerve root than the paramedian posterior approach.

Any herniation contiguous with the disc space not sequestered and migrated is amenable to endoscopic disc excision if the boney anatomy permits an unobstructed approach. This uses an “inside-out” technique where the herniation is grasped from its base within the disc space, pulled back into the working intradiscal cavity, and removed via the cannula. The size and types of herniations chosen by the surgeon for endoscopic excision will depend on the skill and experience of the surgeon. Certainly, all contained disc herniations are appropriate for endoscopic decompression. With experience, extruded herniations can be routinely addressed. This approach is especially attractive for recurrent herniations after a traditional posterior approach because the surgeon can avoid the scar tissue from the previous surgery.

Radiofrequency energy can be applied to the annular tears under direct visualization to contract the collagen and ablate ingrown granulation tissue, neoangiogenesis, and sensitized nociceptors.36 Frequently interpositional nuclear tissue is seen within the fibers of the annular tear, preventing the tear from healing. This tissue can then be removed to allow the tear to heal.

Endoscopic foraminoplasty can be readily achieved with bone trephines/rasps, the side-firing Holmium-YAG laser, and endoscopic high-speed drills.5,6 The roof of the foramen is formed by the undersurface of the superior articular facet. This is easily visualized and accessed via the endoscope, and the previously mentioned tools are used to remove bone and enlarge the foraminal opening. Synovial cysts can also be visualized and removed.

In cases of discitis the posterolateral endoscopic approach will provide a robust biopsy for culture diagnosis, and the infected/necrotic disc tissue can be thoroughly débrided to reduce the bacterial load and accelerate healing.37

Contraindications include any pathology not accessible from the posterolateral endoscopic approach. This may include some extruded sequestered disc herniations, extruded migrated disc herniations (migrated extent greater than the measured height of the posterior marginal disc space on T2 sagittal magnetic resonance imaging [MRI]), larger herniations occupying greater than 50% of the spinal canal,4 recurrent or virgin disc herniations with associated epidural scarring, moderate-severe central canal stenosis, and hard calcified herniations. These contraindications are considered relative contraindications dependent on the surgeons’ technical experience and comfort level. More experienced endoscopic surgeons can gain greater access to pathology using advanced techniques for bone removal of osteophytes, stenosis, and the posterolateral corner of the vertebral body before addressing the pathology. Other relative contraindications include inadequate support staff or equipment to successfully perform procedure and uncooperative patients.

Step-by-Step Operative Technique

Patient Positioning

The patient is prone on a hyperkyphotic frame with a radiolucent table. The endoscope is on one side, and the fluoroscopic unit is on the opposite side of the patient.

Anesthesia

Although some experienced international endoscopic surgeons prefer general anesthesia, the authors recommend mild sedation and local anesthesia so that the patient is awake and responsive throughout the procedure. The patient can then provide real-time feedback in case of nerve irritation from instrument pressure or retraction, adding a layer of safety and allowing the surgeon to adjust the instruments accordingly. We use midazolam (Versed) and fentanyl for sedation and recommend against using general anesthetics like propofol, which can produce temporary total analgesia, eliminating the patient’s responsiveness to any nerve stimuli. The skin, needle tract, and annulus are anesthetized with one-half percent lidocaine. This allows anesthesia without motor block of the nerve roots.

Needle Placement

Optimal needle placement is the most crucial step of the procedure and is based on the type of pathology being addressed. The specific protocol21 is demonstrated in the accompanying DVD. The skin window (needle insertion site) is determined using this protocol. This will typically be about 12 to 15 cm lateral to the midline aligned parallel to the disc inclination (Fig. 59–3).

Once the starting point is determined, the skin window and subcutaneous tissue are infiltrated with one-half percent lidocaine. A 6-inch, 18-gauge needle is then inserted from the skin window at the desired trajectory, typically at a 30-degree angle to the floor (coronal plane) and passed anteromedially toward the anatomic disc center. Infiltrating the needle tract with one-half percent lidocaine as you advance the needle will anesthetize the tissue tract, avoiding pain when the dilator is passed later in the procedure.

The C-arm lateral projection should confirm the needle tip’s correct annular location at the annular window (annular entry point). In the posteroanterior view, the needle tip should be at the disc between the pedicles. In the lateral view the correct needle tip position should be just touching the posterior annulus surface. The above two views of the C-arm confirm that the needle tip has engaged the safe zone, the center of the foraminal annular window.

While monitoring the posteroanterior view, advance the needle tip through the annulus to the midline (anatomic disc center). Then check the lateral view. If the needle tip is in the center of the disc on the lateral view, you have a central needle placement, which is good for a central nucleotomy. Ideally the needle tip will be in the posterior one third of the disc, indicating posterior needle placement if you are attempting to access paracentral herniations.

Evocative Chromo-discography

Perform confirmatory contrast discography at this time. The following contrast mixture is used: 9 mL of Isovue 300 with 1 mL of indigo carmine dye. This combination of contrast ratio gives readily visible radiopacity on the discography images and intraoperative light blue chromatization of pathologic nucleus and annular fissures, which help guide the targeted fragmentectomy.

Instrument Placement

Insert a guidewire through the 18-gauge needle channel. Advance the guidewire tip, 1 to 2 cm deep into the annulus, and then remove the needle. Slide the bluntly tapered tissue dilating obturator over the guidewire until the tip of the obturator is firmly engaged in the annular window. An eccentric parallel channel in the obturator allows for four quadrant annular infiltration using small incremental volumes of one-half percent lidocaine in each quadrant, enough to anesthetize the annulus, but not the nerves. Hold the obturator firmly against the annular window surface and remove the guidewire.

The next step is the through-and-through fenestration of the annular window by advancing the bluntly tapered obturator with a mallet. Annular fenestration is the most painful step of the entire procedure. Advise the anesthesiologist to heighten the sedation level just before annular fenestration. Advance the obturator tip deep into the annulus and confirm on the C-arm views. Now slide the beveled access cannula over the obturator toward the disc. Advance the cannula until the beveled tip is deep in the annular window with the beveled opening facing dorsally. Remove the obturator and insert the endoscope to get a view of the disc nucleus and annulus (Fig. 59–4). The subsequent steps depend on the goal of the procedure and pathology being addressed. The basic endoscopic method to excise a noncontained paramedian extruded lumbar herniated disc via a uniportal technique is described here. Different steps are used for other pathology and are beyond the scope of this chapter.

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FIGURE 59–4 Uniportal endoscopic technique. The cannula is positioned near the base of the herniation. The epidural fat can be seen at the top of the image. The extruded herniation is stained blue with the indigo carmine dye and is seen here extruding through the thinned out annular fibers seen coursing horizontally in this image. At this point the annular fibers are cut to enlarge the annulotomy with the cutting forceps and the side firing laser to allow the apex of the herniation to be pulled back into the disc and out the cannula with the pituitary rongeurs.

Performing the Discectomy

First enlarge the annulotomy medially to the base of the herniation with a cutting forcep. The side-firing Holmium-YAG laser can also be used to enlarge and widen the annulotomy. This is performed to release the annular fibers at the herniation site that may pinch off or prevent the extruded portion of the herniation from being extracted. Directly under the herniation apex a large amount of blue stained nucleus is usually present, likened to the submerged portion of an iceberg. The nucleus here represents a migrated and unstable nucleus. The endoscopic rongeurs are used to extract the blue-stained nucleus pulposus under direct visualization. The larger straight and hinged rongeurs are used directly through the cannula after the endoscope is removed. Fluoroscopy and surgeon feel guide this step. By grabbing the base of the herniated fragment, one can usually extract the extruded portion of the herniation. Initial medialization and widening of the annulotomy reduce the prospect of breaking off the herniated nucleus and retaining the apex of the herniation in the spinal canal. The traversing nerve root is readily visualized after removal of the extruded herniation (Fig. 59–5).

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FIGURE 59–5 Inspection of the freed traversing nerve root. After successful removal of an extruded paracentral herniation, the traversing nerve root is visualized confirming complete decompression of the nerve. This is routine in extruded herniations. If the herniation is a contained herniation, the surgeon would visualize the undersurface of the thinned-out posterior annular fibers rather than the traversing nerve root because the herniation did not extrude past the posterior annulus.

Next perform a minimal bulk decompression by using a straight and flexible suction-irrigation shaver. This step requires shaver head C-arm localization before power is activated to avoid nerve/dura injury and anterior annular penetration. The cavity thus created is called the working cavity. The debulking process serves two functions. First, it decompresses the disc, reducing the risk for further acute herniation. Second, it removes the unstable nucleus material to prevent future reherniation.

Inspect the working cavity. If a noncontained extruded disc fragment is still present by finding blue-stained nucleus material posteriorly, then these fragments are teased into the working cavity with the endoscopic rongeurs and the flexible radiofrequency trigger-flex bipolar probe (Elliquence LLC, Oceanside, N.Y.) and removed. Creation of the working cavity allows the herniated disc tissue to follow the path of least resistance into the cavity. The flexible radiofrequency bipolar probe is used to contract and thicken the annular collagen at the herniation site. It is also used for hemostasis throughout the case.

The vast majority of herniations can be treated via the uniportal technique. Sometimes for large central herniations and herniations at L5-S1, the disc needs to be approached from both sides, a biportal technique. This allows the use of larger articulating instruments that fit through the contralateral 7-mm access cannula and can reach more posterior to extract the herniated fragment under direct endoscopic vision.

Clinical Outcomes

Yeung has reported his initial results using the YESS system in his first 307 patients with disc herniations who were candidates for open microdiscectomy. The study included intracanal and extracanal herniations. Recurrent herniations and patients with previous surgery at the same level were not excluded. Results were reported with 1-year follow-up. Overall patient satisfaction was found to be 91%. The same percentage of patients said they would undergo the procedure again if faced with the same diagnosis. The overall complication rate was 3.5%.22 Tsou and Yeung separated out a subgroup of 219 patients with noncontained herniations and reported results at 1 year. Patient satisfaction was 91%.23 These initial results demonstrated that endoscopic surgery could provide equivalent results to reported results of open microdiscectomy, even with noncontained herniations.

There are three prospective randomized studies comparing traditional microdiscectomy and percutaneous endoscopic discectomy. Hermantin performed a prospective randomized study with 30 patients in each group. The mean duration of follow-up was 31 months. Patient satisfaction was 93% in the open surgical group and 97% in the endoscopic group. The endoscopic group had shorter duration of narcotic use and shorter time out of work compared with open discectomy.1 Mayer performed a randomized prospective study in 1993 with 20 patients in each group. He chose return to previous occupation as his measurement of success. This study showed a significant difference in this outcome measure. In the percutaneous group 95% of patients returned to their previous profession, whereas only 72% of the microdiscectomy group returned to a previous profession.2 In 2008 Ruetten compared traditional microdiscectomy with full endoscopic discectomy via either the transforaminal or interlaminar route. There were 178 patients (87 microdiscectomy and 91 endoscopic) with 2-year follow-up. The microdiscectomy group had a 79% success rate and the full endoscopic group had an 85% success rate with no leg pain at all.3 It is noteworthy that all three of these prospective randomized studies showed a trend toward better outcomes with the endoscopic procedure, but statistically they were comparable.

Kambin reported an 82% success rate for the treatment of lateral recess stenosis and foraminal herniations using an oval cannula with two portals and the transforaminal approach. Even though they were working next to the exiting nerve root, they reported no neurovascular complications in their series.38 Successful posterolateral endoscopic treatment of foraminal and extraforaminal herniations has been described by many authors. Lew reported an 85% success rate in 47 patients,39 Choi reported a 92% success rate in 41 patients,40 Jang reported an 85% success rate in 35 patients,41 and Sassani reported an 89% success rate in 66 patients.42

Knight and Goswami6 have reported on the use of the endoscope in foraminal decompressions for isthmic spondylolisthesis. In 79% of patients a good or excellent outcome was obtained with an average follow-up of 34 months. Of the initial group only two went on to have spinal fusion.6

Ahn and colleagues43 reported an 81% success rate with PELD on 43 patients with recurrent disc herniations after a posterior microdiscectomy. Hoogland also had good success (85%) using endoscopic transforaminal discectomy for recurrent herniations in 262 consecutive cases from 1994 to 2002. Of the 262 patients, 194 had a previous posterior microdiscectomy and 68 had a prior endoscopic discectomy.44 Both studies pointed out the advantage of avoiding the posterior scar tissue.

The ability to effectively remove pathology using endoscopic surgery has been validated by postprocedure imaging studies. Casey and colleagues45 looked at a group of patients who had immediate postoperative computed tomography scans. The imaging studies demonstrated 88.9% of patients undergoing biportal endoscopy had significant reduction in the amount of neural compromise. The results of uniportal, extraforaminal, and foraminal herniations showed only mild to moderate change in canal diameter. They concluded that arthroscopic discectomy had a high rate of canal clearance and removal of disc fragments.45

Lee and colleagues4 reported on a matched cohort comparing radiographic changes 3 years postsurgery in PELD versus posterior microdiscectomy. They revealed less degenerative progression in the PELD group with loss of disc height and foraminal height being statistically significant. Clinical success rates were 96% in the PELD group and 93% in the microdiscectomy group. The authors conclude that PELD is a less invasive procedure that causes less approach related damage and less damage to the targeted disc.4

Complications and Avoidance

The risks of serious complications or injury are low—approximately 3%. The usual risks of infection, nerve injury, dural tears, bleeding, and scar tissue formation are present, as with any surgery. Because the transforaminal endoscopic approach passes adjacent to the exiting spinal nerve root and dorsal root ganglion, there is potential for nerve irritation (dysesthesia) or overt nerve damage. Dysesthesia occurrence is 5% to 15% and is almost always transient.22,23 This rate of occurrence is similar to dysesthesia rates in posterior open discectomy, but in the latter situation, because the dysesthesia affects the retracted traversing nerve root that was already the source of radiculopathy, the transient persistent or increased postoperative dysesthesia is generally not considered a complication after posterior discectomy. Both situations, however, are transient the vast majority of the time. Routine injection of steroid medication at the conclusion of the endoscopic discectomy has reduced the rates of dysesthesia significantly.

Avoidance of complications is enhanced by the ability to clearly visualize normal and pathoanatomy, the use of local anesthesia and conscious sedation rather than general or spinal anesthesia, and the use of a standardized needle placement protocol. The entire procedure is usually accomplished with the patient remaining comfortable during the entire procedure and should be done without the patient feeling severe pain except when expected such as during evocative discography, annular fenestration, or when instruments are manipulated past the exiting nerve. Local anesthesia using one-half percent lidocaine (Xylocaine) allows generous use of this dilute anesthetic for pain control and still allows the patient to feel pain when the nerve root is manipulated. Thus the awake and aware patient serves as the best indicator to avoid any nerve irritation/damage. Dural tears can be treated with a visualized blood patch and observation because there is no “dead space” for cerebrospinal fluid collection/drainage.

Future Considerations

Perhaps the best new indication for the use of this technique and approach is in the realm of motion preservation (nucleus replacement). A complete endoscopic nuclectomy can be performed followed by insertion of an expandable hydrogel or polymer to completely fill the nuclear cavity, redistribute the load across the disc space, and protect the annulus. The DASCOR nucleus replacement device (Disc Dynamics, Eden Prairie, MN) is a prime example of this technology.

Radical endoscopic discectomy with burring of the endplates and subsequent delivery of an interbody prosthesis with bone graft/bone morphogenetic protein can yield a truly minimally invasive interbody fusion. Transforaminal anatomy will limit the size of implant that can be delivered; however, this problem can be overcome by using expandable interbody or graft containment devices that are being developed.

Future advances in the use of biomaterials and gene therapy may allow endoscopic annular reinforcement, tissue repair, tissue regeneration, anterior column stabilization by disc arthroplasty, and other alternatives to fusion for pain reduction. The future of spine surgery will most likely involve a mix of endoscopic and traditional open procedures. Studies comparing open and endoscopic procedures will have to be performed to find which conditions will be best treated by minimally invasive procedures.

Pearls

1 Initial proper placement of a needle/guide pin is critical to the entire procedure. Take the time to have best possible needle placement in both anteroposterior and lateral projections.
2 Use the “inside-out” technique: Start the endoscopy by first entering the disc and then address the pathology accordingly. This is a safe starting point to avoid getting disoriented to your cannula position. Once you are within the disc, the herniation is between you and the affected nerve; this is advantageous because it protects the nerve from iatrogenic injury. When possible remove the herniation by pulling the herniation into the disc space and then out the cannula.
3 Fluoroscopy should be used to confirm location if there is any uncertainty about anatomy or location during endoscopy.
4 It is helpful to use the specially designed cannulas with a penfield-like extension to retract and protect the exiting nerve when working in the foramen.
5 The patient is awake, so use this to your advantage! If significant leg pain is experienced, stop and re-evaluate the patient; ask him or her about the distribution of the pain and reassess the position using fluoroscopy to prevent complications.
6 When bleeding is encountered advance the scope back into the disc and slowly pull back the scope cauterizing the bleeders from inside to out.

Pitfalls

1 Make sure the MRI and plain roentgenograms are numbered the same (i.e., look out for patients with transitional or six lumbar vertebrae).
2 It is recommended that the patient be awake and alert until the endoscope is within the disc space to avoid nerve injury. Avoiding excessive sedation before this point in the procedure is crucial, especially during needle insertion and dilator and cannula passage. We recommend against the use of a general anesthetic such as propofol.

Key Points

1 Posterolateral endoscopic lumbar discectomy (PELD) is a visualized surgical procedure and is not to be confused with the many nonvisualized percutaneous discectomy procedures for indirect disc decompression.
2 The surgeon can visually confirm that the traversing nerve root is adequately decompressed when removing an extruded paracentral herniation.
3 The literature shows PELD is at least as safe and effective as traditional posterior discectomy.

Key References

1 Hermantin FU, Peters T, Quartararo L, et al. A prospective randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy. J Bone Joint Surg. 1999;81-A:958-965.

The authors showed comparable success rates between open discectomy and arthroscopic microdiscectomy (posterolateral endoscopic discectomy), but the later group had less narcotic use and shorter time off work.

2 Ahn Y, Lee SH, Park WM, et al. Percutaneous endoscopic lumbar discectomy for recurrent disc herniation: surgical technique, outcome, and prognostic factors of 43 consecutive cases. Spine. 2004;29:326-332.

The authors were able to avoid the posterior scar tissue in patients with recurrent herniations after a posterior discectomy and achieve an 81% success rate by using the posterolateral endoscopic approach.

3 Yeung AT, Tsou PM. Posterolateral endoscopic excision for lumbar disc herniation: surgical technique, outcome and complications in 307 consecutive cases. Spine. 2002;27:722-731.

Results of more than 300 patients with 2-year follow-up using the endoscopic technique and working channel scope. Excellent description of author’s technique and outcomes rated using patient satisfaction.

4 Ruetten S, Komp M, Merk H, et al. Full-endoscopic interlaminar and transforaminal Lumbar discectomy versus conventional microsurgical technique: a prospective, randomized, controlled study. Spine. 2008;33:930-939.

This large prospective randomized study directly compares standard microdiscectomy to both posterolateral and posterior interlaminar endoscopic techniques.

5 Lee SH, Kang B, Ahn Y, et al. Operative failure of percutaneous endoscopic lumbar discectomy: a radiologic analysis of 55 cases. Spine. 2006;31:E285-E290.

The authors identify high-grade canal compromise (>50%) and high-grade migration as herniation characteristics that predispose for a higher failure rate with posterolateral endoscopic lumbar discectomy.

References

1 Hermantin FU, Peters T, Quartararo L, et al. A prospective randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy. J Bone Joint Surg. 1999;81-A:958-965.

2 Mayer HM, Brock M. Percutaneous endoscopic discectomy: surgical technique and preliminary results compared to microsurgical discectomy. J Neurosurg. 1993;78:216-225.

3 Ruetten S, Komp M, Merk H, et al. Full-endoscopic interlaminar and transforaminal lumbar discectomy versus conventional microsurgical technique: a prospective, randomized, controlled study. Spine. 2008;33:930-939.

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