You are in: eMedicine Specialties > Neurology > Headache and Pain Laser DiscectomyArticle Last Updated: Jun 7, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Jasvinder Chawla, MD, Assistant Professor of Neurology, Director of Neurology Residency Training Program, Assistant Director of Neurology Clerkship Program, Department of Neurology, Loyola University of Chicago Stritch School of Medicine Jasvinder Chawla is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, American Clinical Neurophysiology Society, and American Medical Association Editors: Jorge E Mendizabal, MD, Consulting Staff, Corpus Christi Neurology; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; James H Halsey, MD, Professor, Department of Neurology, University of Alabama Medical Center; Matthew J Baker, MD, Consulting Staff, Collier Neurologic Specialists, Naples Community Hospital; Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants Author and Editor Disclosure Synonyms and related keywords: degenerative disc disease, degenerative disk disease, herniated disc, herniated disk, laser diskectomy, lumbar disc disease, lumbar disk disease, sciatica, laser discectomy, low back pain INTRODUCTIONSection 2 of 10
  Chronic low back pain is one of the major chronic debilitating conditions involving tremendous loss of money, work, and quality time. Laser is used in different fields of medicine with unique advantages. In treatment of lumbar disc disease, it is useful and advantageous. Laser discectomy is an outpatient procedure with one-step insertion of a needle into the disc space. Disc material is not removed; instead, nucleus pulposus is burned by the laser. Laser discectomy is minimally invasive, cost-effective, free of postoperative pain syndromes, and is starting to get more utilized at various centers. THEORY AND LASER PHYSICSSection 3 of 10
The aim of percutaneous laser disc decompression (PLDD) is to vaporize a small portion of the nucleus pulposus of an intervertebral disc, thereby reducing the volume of a diseased disc and the pressure within it. A small amount of tissue is excised from the center or nuclear part of the disc, which is believed to exert an effect on a noncontiguous portion of nucleus that is protruding through the annulus fibrosus and abutting an exiting nerve root. First described by Hijikata in relation to the percutaneous discectomy method, the central cavity created by laser is believed to allow the nuclear protrusion to move back within the disc. A small change in disc nucleus volume can exert disproportionately large changes on the disc. Yunezawa and coworkers first demonstrated significant alterations in intradiscal pressure in response to vertical load after Nd:YAG laser treatment. Their study also reported the equivalency of laser to aggressive manual curettage. Choy and Altman (1995) reported greater than 50% reduction of intradiscal pressure in response to load following treatment with 1000 J of Nd:YAG laser energy. Prodoehi and associates reported similar results using 1200 J from the holmium (Ho):YAG laser. No specimen is available to weigh after laser discectomy; therefore the amount of disc removed can only be approximated. By calculating the geometry of the laser tract, Choy and Altman (1995) estimated that 1000 J of Nd:YAG laser energy vaporized 98.52 mg of disc. Lane and coworkers, who compared effectiveness of 1200 J each of carbon dioxide, argon, and Ho:YAG laser energy, reported that Ho:YAG was superior, ablating 2.4 g of disc tissue. By comparison, a clinical trial of automated percutaneous discectomy reported removal of 2-7 g of disc tissue with a suction cutting device. Quigley's group compared an automated device, Nd:YAG laser, and Ho:YAG laser and clearly demonstrated the superiority of the automated device in removing the greatest mass of tissue. LASERS IN DISC DISEASESection 4 of 10
Although numerous laser wave lengths have been used in both the experimental and clinical setting, no consensus exists regarding selection of laser, treatment duration, or energy requirements. The following are the various kinds of lasers currently used: Neodymium:yttrium-aluminum-garnet lasers Ascher and Choy and colleagues performed the first Nd:YAG laser discectomy in the mid-1980s. Their procedure consisted of fluoroscopically guided insertion of a needle into the disc space to be treated and threading of a thin laser fiber through the needle into the disc space. Activation of laser with delivery of approximately 1200 J of energy (in short bursts to avoid heating the adjacent tissues) into the disc cavitated the nucleus and ablated a small amount of tissue. The products of vaporization (steam and carbon particles) were allowed to escape through the spinal needle surrounding the laser fiber. At the end of the procedure, the needle site was covered with an adhesive bandage, and the patient was discharged. These investigators postulated that removal of even a small volume of tissue from the disc resulted in a large drop in intradiscal pressure. They believed this may be the mechanism responsible for prompt and marked pain relief in patients who were treated for radiculopathy secondary to degenerative disc protrusion and contained herniations. They suggested that the procedure would not be useful for patients with uncontained herniations or sequestered disc fragments outside the disc space loose in the spinal canal. Ascher, Choy, and others have performed this procedure in more than 1000 patients. Long-term pain relief has been reported in 70-80% of patients. The procedure is appealing in that it is performed on an outpatient basis with conscious sedation. PLDD with a 1.06 Nd:YAG laser has been approved by the US Food and Drug Administration (FDA). Generally, laser discectomy is believed to be equivalent to other percutaneous discectomy procedures, such as chemonucleolysis and automated percutaneous lumbar discectomy (APLD) using a reciprocating suction cutter. Potassium-titanyl-phosphate lasers The crystal of potassium, titanyl, and phosphate (KTP) produces laser light that is lime green. This laser employs fiber optics and is directed easily into disc space through a spinal needle. Davis first used KTP laser for laser discectomy and reported results essentially the same as those described by Ascher, Choy, and others. In early experience, the procedure was found to be safe and effective, and the FDA subsequently approved KTP laser for use in this application. Manufacturers subsequently developed side-firing probes, which make it possible to point laser energy in almost any direction, minimizing the possibility of injury to structures anterior to the spinal column such as the aorta, vena cava, and iliac vessels. Holmium:yttrium-aluminum-garnet lasers The Ho:YAG laser has its wavelength in mid infrared, a range that is absorbed well by water. It is fiber optic. An effective dose of energy can be introduced into the disc via fibers introduced percutaneously through a needle or catheter. Ho:YAG laser is a pulsed laser, in contrast to the continuous-wave near-infrared lasers, and therefore has the theoretic advantage of producing minimal amounts of heat in adjacent tissues. With a pulse width of approximately 250 microseconds at 10 Hz and 1.6 J per pulse, virtually no temperature rise is noted in adjacent tissues. When 1200 J of Ho:YAG laser energy was introduced into the disc through a 400 µm fiber with the same parameters, it consistently produced a 2 cm x 1.5 cm x 1 cm defect in the nucleus pulposus. The defect can be localized precisely in the disc by fluoroscopic needle guidance. The defect should be in the posterior quadrant just anterior to the site of herniation. Early experience revealed the procedure to be safe and effective (as were Nd: YAG and KTP laser procedures), enough to justify FDA approval for marketing of this application. In testing various lasers (carbon dioxide lasers in continuous wave and pulse mode; erbium:YAG; Nd:YAG 1318 µm and 1064 µm; argon; Ho:YAG; excimer), Dr Choy found the greatest efficiency in the carbon dioxide laser in continuous wave and pulse mode and the lowest efficiency in the argon laser. Data on the Ho:YAG were unreliable because of the early generation of laser tested. The Nd:YAG was second only to the carbon dioxide laser, and because the latter has no waveguide, the authors deemed the Nd:YAG the laser of choice for PLDD. INDICATIONSSection 5 of 10
This minimally invasive technique can be performed in patients who need surgical intervention for disc herniation with leg pain from radiculopathy. Patient selection, and especially disk morphology, are the two most important factors determining the choice of the technique. Exclusion criteria include stenosis or facet hypertrophy and disc fragment, although recent review from Knight et al has described its use in foraminoplasty. Relative contraindications are progressive neurological deficit, involvement in workers' compensation cases, and previous surgery at the same disc level. In general, the herniation must have continuity with the parent disc; rupture of the annulus is not a contraindication. All patients must be considered on an individual basis. Criteria for inclusion are undergoing continuing change. Although the optimal candidate as previously described is an untreated single-level herniation with limited migration or sequestration of free fragments, a more recent study from Ahn et al has shown its effectiveness for recurrent disc herniations in some selected cases. What is unacceptable now may, with modifications, become acceptable in the future. During this early stage of PLDD, not adopting a fixed position is important. PROCEDURESection 6 of 10
Entry into disc All percutaneous methods rely on the posterolateral approach to the disc as described by Day. Use local anesthetic supplemented with light sedation to avoid inadvertent root injury. Site of procedure The injection procedure can be performed in an operating room or in a special procedure room of a radiology department, provided the necessary equipment, anesthesia, emergency cart, and trained personnel are available. Positioning The prone or lateral decubitus position is satisfactory if the patient can be positioned properly and stabilized to afford a lateral approach to the disc space. Radiation exposure of the patient in a typical procedure is equivalent to that encountered in a 5-view lumbosacral spine series. Needle placement
Laser application
RESULTSSection 7 of 10
The most extensive experience in the literature was published by Choy and Ascher, who used an Nd:YAG laser. They observed 333 patients for a mean duration of 26 months. The success rate was 78.4% (as measured by a good or fair response) according to MacNab. Siebert (1995) reported on his first 100 patients treated with Nd:YAG. The success rate was 78% at mean follow-up point of 17 months. Davis reported an 85% success rate with the KTP laser, with success rate defined as minimal discomfort and the ability to return to gainful employment (follow-up duration was not specified). Yeung (2000) reported preliminary assessment of more than 1000 patients whose herniated lumbar discs were treated with KTP laser. The reported success rate (good or excellent results) was 84%. No specifics were supplied. Sherk and colleagues used Ho:YAG laser in a comparison of laser discectomy and conservative treatment. No differences were noted between treated and control groups. They concluded that laser discectomy is a safe procedure that appears to be effective in relieving symptoms in some patients. The author uses Ho:YAG laser, and successful results are approximately 80% (comparable to those of other investigators). In another study from India, Ho:LADD (laser-assisted disc decompression) is a very cost-effective and minimally invasive procedure with patient mobilization immediately after the surgery. According to Kramer, the best clinical results were found in discographic stages 7 and 8. In cases of epidural leak of contrast medium and in cases of total degeneration, the clinical results were significantly poor (stages 6 and 9). The literature now includes 23 well-documented cases of erectile dysfunction caused by spinal cord disc herniation. PLDD is a minimally invasive procedure that that can be used to treat such herniation. From 1991-1993, 31 patients with herniated cervical discs were treated with PLDD. In 1990, a few of these patients were treated with the Nd:YAG laser with no complications. Since 1991, the authors have used the Ho:YAG laser; 28 of 31 patients experienced pain relief in a 6-week follow-up period. PLDD is a viable therapy for cervical discs. Singh et al reviewed 38 research reports published between 1986 and 2005 for intradiscal disease therapy classification, surgical intervention, and treatment outcomes (neurologic status, pain scores, and ambulation). Their results revealed that the surgical literature on the management of intradiscal disease continues to be limited, and arthrodesis continues to be the primary treatment modality in most patients. Newer treatment options including laser discectomy have shown promising results with regards to symptomatic relief and early return to function. Provocative discography is recommended prior to the percutaneous lumbar disc decompression. Besides discectomy, laser has recently been used by Knight et al for endoscopic foraminoplasty as well. COMPLICATIONSSection 8 of 10
Discitis is the only documented complication of laser discectomy. In 1993, Choy's group tabulated the world experience with laser discectomy. Choy reported 2 cases of discitis. Subchondral marrow abnormalities may occur in the vertebral endplates after Ho:YAG laser discectomy. Possible causative mechanisms include thermal injury and photoacoustic shock. However, these changes probably do not affect surgical outcomes and appear to resolve over time. CONCLUSIONSection 9 of 10
The rapid acceptance of minimally invasive surgery in the United States has occurred largely without statistical proof of its superiority over traditional methods. All members of the healthcare field now see the need for valid outcome studies supporting the efficacy of new treatment techniques. PLDD will gain wide acceptance only if it is demonstrated statistically to be a safe and effective alternative treatment to lumbar disc herniation. Various laser wavelengths have been used, but no consensus exists regarding which is most efficacious. Good candidates for this procedure have a classic clinical syndrome and neuroimaging evidence. In cases of ruptured posterior longitudinal ligament (ie, epidural leak of contrast medium in discography), PLDD is not indicated. Indications for the operation first of all depend on the clinical symptoms, but the success of the operation depends on the discographic findings. Percutaneous microdecompressive endoscopic cervical discectomy with laser thermodiscoplasty has proven to be a safe and efficacious minimally invasive procedure in one case series of patients with herniated cervical discs with unilateral radicular pain. PLDD performed with CT scan and fluoroscopic guidance appears to be a safe and cost-effective treatment for herniated intervertebral discs and is getting more utilized over the last 3-5 years. It is minimally invasive, is performed in an outpatient setting, requires no general anesthesia, results in no scarring or spinal instability, reduces rehabilitation time, is repeatable, and does not preclude open surgery should that become necessary. REFERENCESSection 10 of 10
Article Last Updated: Jun 7, 2006 |
