Arthroscopic microdiscectomy

The Spine Journal 3 (2003) 60S–64S

Arthroscopic microdiscectomy Parviz Kambin, MD Department of Orthopaedic Surgery, MCP Hahnemann School of Medicine, Philadelphia, PA

Introduction Often back and leg pains are results of a herniated lumbar disc. If such pains do not respond to conservative therapy, they may be treated surgically. In certain cases, surgical goals may be met by operating through an endoscope. This position paper discusses endoscopic surgical treatment of lumbar disc disorders, with particular focus on the technique known as arthroscopic microdiscectomy. Historical review Surgery for herniated lumbar discs through the open exposure of the disc and the nerve root posteriorly (laminectomy or laminotomy) was introduced and popularized by Dandy [1] and Mixter and Barr [2] early in the twentieth century. In 1950, Hult [3] advocated the anterior retroperitoneal approach, because he thought it would prevent the scarring within and around the nerve roots that may occur from open manipulation of the nerves. In addition, he thought it would not cause instability from removal of bone. The concept that reduction of the mass (debulking) of the center of the disc might achieve desirable results was introduced in 1963 by Lyman Smith [4], who lysed the nucleus pulposus of the disc with an enzyme (chemonucleolysis). Kambin et al. in 1973 [5,6] and Hijikata et al. in 1975 [7,8] removed nucleus from the disc through mechanical tools inserted through puncture wounds in the skin and passed through tissues outside the spinal canal. Later deThis Contemporary Concepts review article has been reviewed by the Board of the North American Spine Society (NASS). As such, it represents the current position on the state of knowledge of the above subject in spine care. This series is edited by Alexander Vaccaro, MD. Prior to entering the review process for The Spine Journal, the authors were assisted by members of the NASS Committee on Contemporary Concepts, Alexander Vaccaro, MD,* Chair. FDA device/drug status: not applicable. Author does not have a financial relationship that creates, or may be perceived as creating, a conflict related to this article. * Corresponding author. Alexander Vaccaro, MD. The Rothman Institute, 925 Chestnut Street, 5th Floor, Philadelphia, PA 19107, USA. Tel.: (215) 955-5367; fax: (215) 503-0580. E-mail address: [email protected] 1529-9430/03/$ – see front matter © 2003 Elsevier Inc. All rights reserved. PII: S1529-9430(02)005 5 8 - 2

bulking of the nucleus with an automated suction device [9,10] and use of a laser as an adjunct to that purpose [11] have been tried. Schreiber et al [12] used an arthroscope to illuminate the disc during procedures to remove the nucleus. In the early 1980s, Kambin et al. [5,13,14] applied negative atmospheric pressure and used deflecting instruments to see and manipulate fragments of nucleus that had been displaced beyond the disc space. In the 1980s and the 1990s, the radiographic landmarks of a safe zone on the dorsolateral corner of the intervertebral disc for the insertion of the instruments were described [6]. The availability of small-caliber arthroscopes and endoscopes permitted visualization of the periannular and neural structures and removal of herniated disc fragments [15–17]. A distinction must be made between the recently introduced microendoscopic discectomy and arthroscopic microdiscectomy, which is presented in this article. The cannula that is used during microendoscopic discectomy is much larger and similar to open procedures; it requires laminotomy, entrance to the spinal canal, manipulation of neural and vascular structures, fenestration of annulus and removal of herniated disc tissue. In addition, laparoscopic lumbar discectomy [18] has been attempted. However, at this time sufficient data for the feasibility and efficacy of this approach for a simple discectomy are not available. Rationale The intervertebral disc is composed of a relatively soft and amorphous nucleus pulposus in the center, surrounded by a multilayered ligament, the annulus fibrosus. As a result of herniation or “rupture” of the disc, a portion of the nucleus and/or torn or attenuated annulus may come to lie external to the disc space and cause pressure, tension or mechanical irritation of the overlying nerves. The outer layers of the annulus fibrosis and the nerves are sensitive and may be sources of pain from the herniated disc. The purpose of surgical intervention is to remove sources of pressure, tension and irritation from the nerves and annulus. The idea is to accomplish this with minimal bleeding,

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scarring and potential injury to the sensitive neural tissues; minimal loss of strength of the structures that support the spine and minimal risk of other complications. Surgery on the disc can be performed through one or two ports by means of endoscope(s) inserted through 1-cm skin incisions. Manipulation of muscle is blunt and minimally traumatic. The protective bone and ligaments over the posterior surface of the vertebral canal are not broached. Highresolution glass arthroscopes enable the surgeon to see the nerve roots (traversing and exiting), adjacent structures and external surface of the annulus before entering the disc space. One or two hollow tubes (cannulas) approximately .25 inch in diameter are passed through the skin and muscle layers and positioned on the outer layer of the annulus adjacent to the spinal canal. Two tubes can be inserted from the right and left side of the patient, or both can be positioned from the same side. By using fluoroscopy and an endoscope, the surgeon is able to position the cannulas under the outer layer of the annulus and a wide ligament (posterior longitudinal ligament), which separates the disc from the content of the spinal canal. When proper equipment is used, the surgeon can see and remove fragments that have herniated beyond the posterior annulus or posterior longitudinal ligamentum. Some fragments of nucleus pulposus that have moved beyond confinement of the annulus may be seen and retrieved if they have not migrated too far up or down the spinal canal, and if sufficient continuity remains between the bulk of the fragment and what the surgeon may access. When the herniation is outside the spinal canal (foraminal and extraforaminal), the cannula may be positioned directly over the herniation site and evacuated. When the bleeding and the abundant fatty tissue of the spinal canal are not interfering with optimal endoscopic visualization, the cannula may be directed toward the spinal canal for removal of a disc fragment that has been dislodged. Because the spinal canal is not entered at all, or only by probing through the already present rent in the annulus, sur-

Fig. 1. Intradiscal view of the ventral surface of the dural sac following subligamentous retrieval of a large sequestered disc herniation.

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gical contact between the nerve root and meninges is much less than with conventional posterior, open surgery. Because intact fibers of annulus are not incised or damaged by repeated passage of instruments, the integrity of the annulus should be better preserved than after standard open procedures, an advantage that should help reduce the incidence of recurrent herniation of the disc. Local anesthesia suffices and, in most cases, is preferable for disc surgery through the arthroscope, a fact that should favor reduced rates of general complications, shorter hospital stays and reduced costs. Results Kambin et al. [16,17,19–22] published prospective studies that documented the effectiveness trial of arthroscopic disc surgery. These works drew on data from patients and physicians who followed carefully drawn evaluation schemes before and after arthroscopic discectomy. They considered the outcome to be satisfactory if, after surgery, nerve (radicular or sciatic) pain had ceased, tension of nerve irritation was absent and the patient had become functional and was taking less or no medication. Using those criteria, their combined series report an 87% satisfactory outcome. There have been no reported neurovascular complications after arthroscopic microdiscectomy of the lumbar spine. Schaffer and Kambin [23] reported two cases of broken instruments that were retrieved during surgery under arthroscopic visualization. Incidence of postoperative infection has been less than 1%. Other investigators who have used arthroscopic techniques or large cannulae for evacuation of lumbar discs have reported similar levels of satisfactory results [23–33]. In a prospective, randomized study to evaluate the efficacy of open “microscopic” discectomy as compared with removal of the disc though an endoscope, Mayer and Brock

Fig. 2. Transforaminal access to the spinal canal. The traversing root is seen on the top of the photo; epidural adipose tissue is noted on the right and bottom of the photograph. The endoscope allows visualization of the nerve root, not only dorsally as seen during conventional exposure, but also permits examination of ventral, lateral and medial boundaries of the nerve root.

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[26] reported more favorable outcomes with fewer complications for those treated by arthroscopic disc surgery. In another randomized prospective study, Hermantin et al [15] compared the result of traditional laminotomy, discectomy by means of a 4-cm skin incision with arthroscopic microdiscectomy and concluded that the patients who underwent arthroscopic microdiscectomy did not require overnight hospitalization, returned to work and resumed their activities sooner and required less postoperative pain medications and long-term narcotic use. Overall, the arthroscopic microdiscectomy group was more satisfied with the results of their surgery. In a multicenter study of percutaneous endoscopic discectomy of the lumbar, thoracic and cervical spine, Chiu et al. [34] evaluated the outcome and incidence of complications in 26,860 patients who underwent posterolateral arthroscopic and endoscopic disc fragment resection. Forty spine surgeons participated in this study. A high rate of patient satisfaction and less than 1% overall incidence of complications were found. There was no reported incidence of mortality. The efficacy of arthroscopic microdiscectomy in retrieving the herniated disc fragments has been shown objectively in preoperative and postoperative computed tomography and magnetic resonance imaging studies of 40 patients who were studied prospectively [35].

Theoretically, the reduction of the volume of the nucleus may relieve symptoms by decreasing tension on the fibers of the annulus and the posterior longitudinal ligament and by favorably altering the chemical milieu of the annulus and nerve roots. Successful outcomes have been reported, ranging from 70% [9] to 52% [40] of patients. Arthroscopic microdiscectomy focuses on treatment of that group of patients who have demonstrated the displacement of nucleus pulposus beyond the disc space, many of whom would be considered to be beyond the indications for the limited nucleotomy procedures. It is that group of patients who are most likely to need surgical, as opposed to nonoperative, management of pain, and it is that group to which most meaningful comparisons can be made to the standard discectomy. Of all the minimally invasive techniques, arthroscopic discectomy is the only procedure that provides access to the fragments that have migrated within the spinal canal. The technical ability to remove, through an arthroscope, the displaced fragments that had once required open discectomy is a recent achievement. However, arthroscopic microdiscectomy has a learning curve that requires patience and experience. The procedure may be performed under local anesthesia on an outpatient basis.

Discussion

Future studies

The place of arthroscopic microdiscectomy in the spectrum of minimally invasive techniques for management of pain from lumbar discs has been defined. By using high-performance optics and angulated instruments, the surgeon may explore and manipulate beyond the confines of the disc space. Although such capability extends the potential benefit of arthroscopic techniques, it also increases the demands on the surgeon’s skills and the performance of the instrumentation. Simply by familiarity, because of long-time and established use, open laminotomy and discectomy from a posterior approach has been regarded as a standard surgical treatment for disc herniation. Satisfactory outcomes from posterior open discectomy have been reported, ranging from highs of 85% [13] or 91% [36] to a low of 48% [37]. The center of the nucleus may be retrieved without attention to the displaced and herniated disc fragments (nucleotomy). This may be accomplished manually [7,8] or by means of power-driven instruments, such as automated nucleotome [9,10]. Nucleotomy also has been performed under arthroscopic magnification and illumination [12]. Various laser lights also have been used for vaporization of nuclear tissue [11]. Chemical dissolution of the nucleus by means of intradiscal injection of chemopapain is one of the original methods of nuclear debulking surgical techniques employed for the treatment of a herniated lumbar disc [4,38,39].

At the present time, there is no universally accepted method for evaluating the preoperative and postoperative conditions of patients for the purpose of scientific analysis and reporting. Such diagnostic terms as herniation, protrusion and extrusion may represent different entities to various practitioners. For these reasons, comparison of statistics from one technique, such as nucleotomy, to treat a specific group of patients with an entirely different technique, such as open surgery or arthroscopic technique used for treatment of a somewhat variant group of patients, is not valid. In a recent randomized prospective study [15], care was exercised to define more precisely the groups of patients in terms of volume, location, containment and continuity of displaced disc, size of vertebral canal and assessment of stenosis or other factors that contribute to symptoms. Before and after surgery, pain, motion, stability and various social and psychological factors were assessed with a relatively equal short-term outcome after open laminotomy and arthroscopic microdiscectomy. Future multicenter, randomized, prospective, comparative studies for both nonoperative and operative treatments of herniated lumbar discs will further define the indications for a specific treatment modulation in the management of a given disc herniation. However, it should be acknowledged that legal and humanitarian concerns also may compromise the ability to conduct thorough studies because of patients’ rights to know and to choose.

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Microinvasive techniques have been used to fuse the spine [41–45]. Refinement of those techniques and extension of arthroscopic abilities to sculpt the spinal passageways for treatment of stenosis are progressions in the future of arthroscopic spinal surgery. Current experimental work on nuclear replacement and insertion of artificial discs by means of a posterolateral arthroscopic technique may prove to be a great contribution in the field of spinal surgery. Continuation of the phenomenal technical progress with optics and instrumentation is a necessary adjunct to surgical progress. Current recommendations For patients who choose surgery for the treatment of their pain and radiculopathy resulting from a displaced lumbar disc, arthroscopic microdiscectomy offers an alternative method of treatment. Arthroscopic microdiscectomy is not indicated for patients who have severe concomitant spinal stenosis or those with mechanical instability. Arthroscopic microdiscectomy is contraindicated for treatment of patients presenting with cauda equina syndrome. For patients who have fragments of nucleus that have migrated substantially from the level of the disc space and are not continuous with nucleus within the disc, open surgery is usually preferable. Finally, the retrieval of a central disc herniation between the fifth lumbar and first sacral segment by means of arthroscopic technique in individuals with a high iliac crest might be difficult. With those exceptions, arthroscopic discectomy may be considered appropriate treatment for the same group of patients who might otherwise be treated appropriately by open posterior discectomy, which includes those with unremitting or recurrent radicular pain, failure to respond to noninvasive measures, objective physical findings of nerve dysfunction and irritability and corroborating images (magnetic resonance imaging, computed tomography or myelogram). Further, arthroscopic discectomy should be considered only when a properly trained surgeon and support team would perform the procedure with radiographic, optical and surgical instruments necessary to meet all reasonably expected contingencies. The latter should include the ability to perform open surgery to manage complications. References [1] Dandy WE. Loose cartilage from intervertebral disc simulating tumor of the spinal cord. Arch Surg 1929;19:660–72. [2] Mixter WJ, Barr JS. Rupture of the intervertebral disc with involvement of the spinal canal. N Engl J Med 1934;211:205–10. [3] Hult L. Retroperitoneal disc fenestration in low back pain and sciatica. Acta Orthop Scand 1950;20:342–8. [4] Smith L. Enzyme dissolution of the intervertebral disc. Nature 1963; 198:1311–2. [5] Kambin P, Gellman H. Percutaneous lateral diskectomy of the lumbar spine. A preliminary report. Clin Orthop 1983;174:127–32. [6] Kambin P, Zhou L. History and current status of percutaneous arthroscopic disc surgery. Spine 1996;21(24 suppl);57S–61S. [7] Hijikata S, Yamagishi M, Nakayama T, et al. Percutaneous diskec-

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