Laparoscopic Lumbar Discectomy: Description of Transperitoneal and Retroperitoneal Techniques

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PERCUTANEOUS SPINE TECHNIQUES

LAPAROSCOPIC LUMBAR DISCECTOMY Description of Transperitoneal and Retroperitoneal Techniques Theodore G. Obenchain, MD, and David Cloyd, MD

Minimally invasive methods of lumbar discectomy have been used increasingly over the past 10 years. Definite limitations exist w ith these techniques, however, particularly as they relate to targeting the herniated portion of the disc. Posterolateral discographic approaches are 60 degrees off target. Only with angulated endoscopes and articulated instruments is this problem overcome. Techniques aimed at "disc decompression," particularly those that u se the laser, do not stand the test of long-term follow up. For a technique to be effective long term, definitive removal of the disc herniation must be achievable consistently. The previous gold standard toward which less invasive methods aspired was open laminectomy with its attendant 5-day hospital stay. To be worthwhile, minimally invasive techniques now must equal the clinical effectiveness of microlumbar discectomy and its 24 to 48 hour hospitalization. 4• 5 It must be superior to the microlumbar method with regard to length of stay, attendant pain, and morbidity This work is supported by SPINETECH, Inc. The author owns stock in SPINETECH, Inc., and has a patent licensing agreement with the company.

as well as global cost of the surgical endeavor. Minimally invasive techniques also have the theoretical advantage of no resultant spinal scarring, the inevitable accompaniment of any open procedure. The senior author, frustrated with posterolateral techniques available in the 1980s, developed the anterior laparoscopic approach with the intent of targeting the disc herniation directly. Preliminary work included protocol approval by the Palomar Medical Center Investigational Review Board plus operative experience in a cadaver. Laparoscopic exposure of the anterior aspect at the lumbar spine in a human volunteer was gained prior to offering the procedure as a therapeutic option. The first case, a 29-year-old male w ith a large LS-Sl herniation, was performed successfully in February 1991. 2 To date, we have had experience with 29 cases, which form the basis for a portion of this report. Laparoscopic lumbar discectomy is a procedure in evolution. The latter part of this report details the current work in progress; a foraminal approach, combining the posterolateral discographic approach w ith laparoscopic retroperitoneal dissection.

From the Department of Neurological Surgery (TGO), and Surgery (DC), Palomar Medical Center, Escondido, California

NEUROSURGERY CLINICS OF NORTH AMERICA VOLUME 7 •NUMBER 1 •JANUARY 1996

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METHODS

OPERATIVE TECHNIQUES

Patient Selection

Transperitoneal Laparoscopy

Patients who are candidates for microlumbar discectomy also are candidates for laparoscopic lumbar discectomy. The most prominent symptom should be leg and back pain, with leg pain predominating. Patients should have failed 6 weeks of conservative treatment consisting of physical therapy and courses of analgesics and anti-inflammatory medications. Physical examination should reveal a positive straight leg raising test and evidence for nerve root irritation consisting of radicular pain or reflex and sensory changes. An imaging study, usually MR imaging scan, reveals a disc herniation on the side and level consistent with the patient's complaints. The laparoscopic approach can treat contained disc herniations as well as extruded and even mildly migrated disc fragments. Patients with sequestered discs migrated fully below the level of the disc space cannot be treated by this method.

The transperitoneal route was used for the first 26 cases, with experience being gained at the L3-4, L4-5, and LS-Sl disc spaces. The patient is placed supine and a urinary catheter inserted. Under general anesthesia, an initial umbilical port is placed and abdominal insufflation to 16 mm of mercury is carried out. Three or four other ports are placed through the abdominal wall to establish the main working port as well as other ports for dissecting instruments. The patient is placed in steep Trendelenburg position so that the small bowel gravitates to the upper abdomen, minimizing the amount of bowel retraction needed. At the LS-Sl space, the working port is placed midline just above the pubic symphysis to direct the working port and instruments in a line colinear with the inclination of the disc space. The amount of peritoneal dissection is minimal. A 1-cm opening through the parietal peritoneum is established in between the

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Figure 1. Dissecting trocars (A, B). An endoscope is placed in the lumen of the trocar. Tissue dissection occurs by a blade extending 1 mm with each pull of the trigger. The dissecting balloon (C) is placed within the retroperitoneal space and inflated while an endoscope, inserted into the balloon, allows visualization of the dissection.

LAPAROSCOPIC LUMBAR DISCECTOMY

common iliac vessels that are, at this level, at the far lateral aspect of the disc space. Visualiz~tion ~s comparable with that of microscopic d1ssect10n. One usually can visualize and avoid the autonomic nerves traversing the annulus. The abdominal working port for L4-5 dissection is 4 to 5 cm below and to the left of the umbilicus. This gives colinearity of the port and trephine to a line through the disc space. At the L4-5 disc space the entry point is just lateral to the left common iliac vessels and medial to the psoas muscle, whether the herniation be on the right or left side. One centimeter access at this level consistently is achievable. Levels higher than L4-5 are approached in a manner similar to L4-5 (i.e., to the immediate left of the aorta and medial to the inner aspect of the psoas muscle).

Retroperitoneal Laparoscopy

The retroperitoneal technique is carried out with the patient's symptomatic side upward. It can be performed under general anesthesia or under local anesthesia with sedation. Entry into the retroperitoneal space is achieved by a direct 10-mm opening through the three layers of the abdominal musculature and through the transversalis fascia. Entry also can be achieved through these muscular layers using an endoscopic trocar as produced by US Surgical (Norwalk, CT) or Ethicon (Cinncinati, OH) (Fig. 1). An endoscope is placed in the lumen of the trocar after a skin incision is made. These devices make sequential 1-mm cuts, allowing the surgeon to observe tissue planes as he or she traverses them. Once entry into the retroperitoneal space has been achieved, a balloon (Origin, Menlo Park, CA) is inflated while the dissection is observed endoscopically. The receding line of peritoneum can be observed moving medially across the psoas muscle and into the adventitial tissue surrounding the great vessels (Fig. 2). The ureter is elevated with the peritoneal plane. The balloon now is deflated and removed, to be replaced by a trocar through which insufflation can be maintained at a pressure of approximately 5 mm of mercury. Two other 5-mm entry sites are made in the flank for dissecting tools. Under endoscopic and fluoroscopic guidance, dissection is carried out exposing the annulus imme-

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Figure 2. Retroperitoneal dissection as seen with endoscope in the dissecting balloon. The peritoneum resembles receding surf (arrow) as it sweeps medially over the psoas muscle. The ureter (U) is seen through the curtain of peritoneum .

diately medial to the psoas muscle (Fig. 3). The abdominal trocar now is placed in line with the disc space to be entered. At this point in the operation, whether the annulus exposure is achieved transperitoneally or retroperitoneally, ~he spinal trephine is placed through the workmg 10-mm abdominal trocar site. The point of the trephine is impaled into the exposed annulus (Fig. 4) under fluoroscopic and endoscopic guidance. The teeth engage the annulus in a twisting fashion. Once through the ~nnulus, a variety of curettes and rongeurs are mtroduced to remove some disc tissue. In the last 10 cases, a discoscope was used in the

Figure 3. Retroperitoneal dissection exposing the annulus (arrows) . Ureter (U), psoas muscle (P) and autonomic nerve (*) are easily visible.

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Figure 4. Spinal trephine (*) has passed through the abdominal trocar (T) with the teeth engaging the annulus medial to the psoas muscle (P).

disc space. Through a working port, automated shavers, disc space rongeurs, and curettes are placed under endoscopic vision. Shaving and removal of disc tissue (Fig. 5) is carried out until a defect in the posterior longitudinal ligament (PLL) is seen. Extruded disc tissue can be retrieved through the defect in the PLL (Fig. 6), thus decompressing the neural structures. With completion of the discectomy, the abdomen is desufflated. Endoscopy is used to make certain that there is no venous bleeding on release of abdominal pressure. Deep fascial sutures are placed in the working discectomy abdominal port. The patient then is awakened, transferred to the recovery room, and discharged to home approximately 3 hours later.

fully on an outpatient basis. Follow up varied from 12 to 52 months, with a mean of 35.8 months. Twenty-nine patients were operated on, but in one case entry could not be accomplished owing to a very large abdomen. That patient is included as a complication but is excluded from statements regarding discectomy because none was carried out. Other complications include a hernia at the trocar site that required decompression. Two cases of discitis were encountered, one "sterile" and one of Staphylococcus aureus . . Pain relief was judged by the following criteria. E~celle~t d~notes essentially total symptomatic rehef with full level of activity. A good result means near total symptomatic relief but back or leg pain may be provoked with much activity. Mild pain at rest, increasing to moderate with activity, signifies a fair result. A poor :esult means no improvement in pain or activity level at all or reoperation. Twenty patients experienced pain relief. Seventeen were considered to have had excellent results whereas three patients were judged as good. A fair result was experienced by two patients. In seven patients the result was considered to be poor. Six patients experienced early recurrence of leg pain and required reoperahon. The two patients with discitis, considered to be poor results, ultimately have experienced resolution of their pain. Two other patients experienced mild to moderate low back pain. Preoperatively, 22 patients were u sing oxycodone or hydrocodone for pain relief. The remaining seven patients required Darvocet

Results

Experience in 29 cases generally has been favorable. Mean age of the patients was 40.6 years with a range of 18 years to 58 years. Patients had experienced symptoms for a mean period of 9.6 months. MR imaging on all patients revealed changes consistent with disc herniations. Most patients had herniations contained within the PLL. Seven patients, however, had extruded discs. Sixteen patients h~d disc herniations at the L4-5 disc space, with one of that group also having a simultaneous L3-4 disc herniation. Eleven patients had the herniation at L5-Sl level. Three patients had L3-4 disc herniations, making in all 30 herniations in 29 patients. In seven cases the injury was industrial in origin and in 22 cases it was not. All patients were treated success-

Figure 5. Lateral fluoroscopic view of curette in the L5-S1 disc space. The distal tip of trephine (arrow) is just inside the disc space.

LAP AROSCOPIC LUMBAR DISCECTOMY

Figure 6. Discoscopic view inside the L4-5 disc space. The PLL (Y) is seen with a defect (X) with in it. Asterisk notes disc remaining with in the disc space.

or nonnarcotic prescription medications. Most patients used less than a total of 10 hydrocodone tablets during the first postoperative week. Follow up at 35.8 months revealed 22 patients requiring no medication and seven patients using acetaminophen or its equivalent. The six patients requiring reoperation were using hydrocodone prior to their second operation. Sixteen of the twenty-eight patients were unable to work before surgery. Postoperative, 19 patients were able to return to work in a mean time of 3.5 weeks. Three patients with industrial injuries returned to work at moderate to heavy labor in 2 weeks, 6 weeks, and 12 weeks. Those requiring reoperation were excluded from return to work data in that they were failures of the anterior route. DISCUSSION

Some form of laparoscopic lumbar discectomy will, in the authors' opinion, be the final embodiment of minimally invasive discectomy. That form has, however, not yet been attained. This procedure is not as yet recommended for general usage for several reasons. The complication rate, although encountered early in the series, is too high. The two cases of discitis are felt to be the result of awkward instrumentation requiring multiple entries and exits from the disc space. The reoperation rate also is too high. With better endoscopes and more aggressive shavers, more effective discectomy should be attainable even if the trans-

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discal retroperitoneal route continues to be used. It is essential to have an experienced laparoscopist as a member of the surgical team with the capability to perform an immediate laparotomy if complications so dictate. The retroperitoneal technique, however, is sufficiently easy and safe enough that a spine surgeon with moderate laparoscopic skills and experience could perform it with a surgical assistant. Another disadvantage of anterior discectomy is the potential for segmental instability. Of the 16 patients in the series undergoing discectomy at L4-5, 10 had postoperative radiographs performed. Six of the ten had settling of the disc space. Four of the six patients were asymptomatic but two patients had low back pain, one disabling. This potential disadvantage could be overcome with miniaturization of instrumentation, traversing the disc space in its extreme lateral aspect as the retroperitoneal technique allows, or avoiding the transdiscal route entirely by accessing the neural foramen. The evolution of technique, however, has been from that of transperitoneal dissection to one of a retroperitoneal route. Transperitoneal dissection technically is more demanding and is labor and technologically intensive. Although we encountered no complications with visceral injury, the potential remains significant. The final role for the transperitoneal method will be as the sole route for the rapidly expanding technique of laparoscopic interbody fusion at the lumbosacral level. Because the retroperitoneal space ends at the pelvic brim, the possibility of carrying out a laparoscopic retroperitoneal fusion at the lumbosacral level remains remote. The retroperitoneal technique was first used by Gaur 1 for accessing the urinary system. It has a number of advantages, the most obvious being the ease of dissection. This space can be dissected by inflating a balloon with a minimum amount of assistance. There is no need for bowel retraction. It also can be carried out with the patient awake. The likelihood of injury to the great vessels, ureters, and bowel is much less with the retroperitoneal technique. Because the annulus can be exposed in the retroperitoneal technique without manipulating the great vessels, one can dissect through the space on the side ipsilateral to the disc herniation. This allows one to dissect through the extreme lateral portion of the disc space,

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Figure 7. A, Axial section of spine at level of midforamen. Note the fat (F) occupying the foraminal entry zone. The nerve root (arrow) is far lateral and out of the trajectory into foramen. Roof of foramen is formed by the pars interarticularis. These two levels are optimal for entry into the epidural space. (B, Axial section of spine just above the pedicle. Inferior aspect of superior articular facet forms the roof of the foramen . Shaded area represents that part of facet that may be rem oved endoscopically.

thereby not interrupting the major part of the intact nucleus to gain access to the herniated portion of the disc. With the transperitoneal route, the surgeon must enter the L4-5 space exclu sively from the left side because of the vascular anatomy. Foraminal Dissection

The next step in the evolution of technique, representing work in progress, is the ultimate refinement of the laparoscopic process. Even with the more lateral transdiscal approach that the retroperitoneal technique allows, the surgeon still must remove normal disc tissue to gain access to the abnormal disc tissue. He or she also must search for the defect in the PLL to ensure definitive treatment of the herniation. Visualizing and accessing the epidural space where the herniation lies is, therefore, always secondary. The surgeon cannot see the nerve root nor can he or she be certain about the

completeness of discectomy. Work on a technique for accessing the foraminal space has been underway for the past 18 months. If the foraminal space can be entered using a minimally invasive techniqu e, the ideal treatment for selective removal of the disc herniation would be realized. The surgeon could visualize the pathologic anatomy directly and see the relationship of the nerve root to the herniation. It also would allow visualization of the ligaments and other anatomy in the epidural space. Figure 7 represents the two levels for ideal entry into the foramen. Fat occupies the major part of the foraminal entry zone, with ligament being in the periphery. 3 Through extensive cadaveric work (Fig. 8) the authors have been able to visualize the foramen, the ligaments of the foramen, as well as the pars interarticularis and the inferior portion of the superior articular facet. The latter forming the posterosuperior boundary of the foramen may be removed with drill or rongeur (see Fig. 7B). With further development, this should allow

LAPAROSCOPIC LUMBAR DISCECTOMY

Figure 8. Foraminal entry in a cadaver. Interior aspect of conduit (C) leads into the ligament (L) and fat (F) in the foramen. The spinal dura (D) can be seen deep to the ligament and fat.

for the treatment of foraminal stenosis under local anesthesia on an outpatient basis. A lateral view of the lumbar spine makes a foraminal approach attractive because of its large dimensions. Measurements of foramina in adult cadaver spines reveal a rostral-caudal dimension of nearly 20 mm. The maximal anteroposterior dimension at the level of the pars is 10 mm and at the narrowest portion (i.e., the level of the superior articular facet) is 5 to 6 mm. Extensive dissections of cadaver spines, however, with the psoas muscle removed, re-

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veals a complete blanket of nerves superimposed over the foramen in a lateral projection (Fig. 9). This blanket is composed of the nerve that exits at that respective foramen plus the nerve that has exited at the foramen immediately rostral. A pure lateral approach will, therefore, be hazardous for two reasons. First, one likely will traverse a portion of the abdominal cavity with high risk of visceral penetration. Secondly, the blanket of nerves covering the foramen does not allow safe entry into the epidural space without significant risk of neural injury. The foraminal approach, however, is achieved consistently in the cadaver by combining the posterolateral discographic approach with the laparoscopic retroperitoneal dissection, thereby making a lateral trajectory into the foramen safe. A discographic needle contains a conduit within it that is oriented 35 degrees to the longitudinal axis (Fig. 10). This needle contains a bevel near its pointed distal end, which serves as a "heel" to deflect the nerve root complex anteriorly when the needle is in its final position. When fluoroscopically placed into the disc space in a standard discographic fashion and rotated 90 degrees (arrows in Fig. 9) the bevel deflects the nerve roots anteriorly, giving an opening into the foramen. The surgeon next insufflates the retroperitoneal space via a 10-mm trocar site in the flank, thereby deflecting abdominal contents out of the line of entry for the second trocar. Next, the triangulated arm is placed

Figure 9. A, The lumbar spine with psoas muscle removed. Nerves cover the entire lateral aspect of the foramen. The discogram needle tip is placed in the area between the spinal dura and the nerve that has exited from that foramen. B, As the needle tip penetrates the disc space, it is rotated 90° in its longitudinal axis to deflect the nerve roots and orient the conduit transversely, connecting retroperitoneal space with the foramen.

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1

3

5 4 Figure 10. A, Disassembled triangulation device. 1 = discogram needle with conduit. 2 = Triangulation arm. Obturator 3 fits inside of 4 to access the conduit, starting from the triangulation arm. 5 = rigid endoscope, 6.4 mm. OD with 4.0 mm . working port. B, Assembled device with endoscope now in the conduit. Medial aspect of conduit lies at the entrance to the foramen .

onto the discographic needle and the second trocar enters through the shaft of this stereotaxic arm (Fig. 10). This trocar passes through the insufflated retroperitoneal space to the lateral opening of the conduit leading from retroperitoneal space into the foramen. A parallel eyepiece rod-lens endoscope with 4-mm working port now is introduced into the conduit via the trocar. Figure 11 depicts the triangulated device in place with the endoscope traversing the full length of the con-

duit to the epidural space. A variety of automated shavers, rongeurs, suction, and suction punches (Fig. 12) are introduced to define the anatomy better and to traverse the fat and ligamentous structures in the lateral aspect of the foramen. The bone comprising the perimeter of the foramen may be visualized and removed with a rongeur or a high speed drill. The inferior portion of the superior articular facet is visualized most readily and may be removed as one does in an open

Figure 11. Axial rendering of lumbar spine with triangulation device in place. Note tip of discogram-conduit needle in the disc space and the nerve deflected under the heel of the needle (arrow) . lnsufflation of left retroperitoneal space (R) allows safe transit of trocar and endoscope into the conduit and lateral aspect of the foramen.

LAPAROSCOPIC LUMBAR DISCECTOMY

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Figure 12. Instruments compatible with the 4.0 mm working port for dissection through the foramen. Array includes automated shavers, high speed drills, suction punch , 90° Kerrison rongeur and interspace rongeurs.

extraforaminal decompression of nerve root (see Fig. 7B). This removal can extend down to the most rostral aspect of the pedicle, gaining access to the epidural space of the lower vertebral body. Once entry into the canal is achieved, contained disc herniations, extrusions, or even sequestra should be removed readily by this method. With the cadaveric phase of the study completed, a clinical trial now is being initiated.

References l. Gaur DD: Laparoscopic operative retroperitoneoscopy:

Use of a new device. J Urol 148:1137-1139, 1992 2. Obenchain TG: Laparoscopic lumbar discectomy. J Laparoendosc Surg 1:145-149, 1991 3. Rothman SL, Glenn WG: Multiplanar CT of the Spine. Baltimore, University Park Press, 1985, pp 72-73 4. Williams RW: Microlumbar discectomy: A twelve year statistical review. Spine 11:851-852, 1986 5. Zahrawi F: Microlumbar discectomy. Spine 19:10701074, 1994

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