Nucleoplasty for disc protrusion: A novel percutaneous decompression technique

Techniques in Regional Anesthesia and Pain Management (2009) 13, 93-101

Nucleoplasty for disc protrusion: A novel percutaneous decompression technique Karen Knight, MD, Don M. Woods, MD, Ali Mchaourab, MD From Case Western Reserve University, Pain Medicine and Spine Care, Cleveland Veterans Affairs Medical Center, Cleveland, Ohio. KEYWORDS: Decompression methods; Percutaneous methods; Low back therapy; Intervertebral disk surgery; Discectomy methods; Lumbar vertebrae

Nucleoplasty is an FDA-approved minimally invasive technique for percutaneous decompression of intervertebral disc protrusion. It is indicated for radicular pain, but there are emerging data related to management of discogenic pain. The evolution of minimally invasive spine techniques provides an impetus for pain specialists to ensure the safest and most effective use of these technologies. Due to its relatively recent release, pain management specialists are still exploring its best possible use. In this article, research regarding this technique is summarized and the technique is described. Recent research has been positive in carefully selected populations, and a current, multicenter, randomized, controlled trial should soon clarify its role in treatment of chronic low back pain from the degenerative disc. Published by Elsevier Inc.

Nucleoplasty is a minimally invasive technique introduced in 1999 as a percutaneous intradiscal treatment for intervertebral disc protrusion leading to radicular pain. It has been advocated for both disc bulges and protrusions leading to partial nerve compression or irritation as well as for axial back pain generated by the disc itself also known as discogenic pain. It uses sufficient electrical energy to break molecular bonds within tissue, leading to tissue vaporization. This causes a decrease in the volume of the nucleus pulposus, decreasing intradiscal pressures and thereby restoring normal disc metabolism and modifying the inflammatory response.1 The objective of the treatment is to reduce pain and increase function in individuals with contained disc protrusion. However, because this minimally invasive spine technique has both several indications and a paucity of prospective randomized studies, it challenges pain management specialists to better understand both its potential and its limitations.

Address reprint requests and correspondence: Karen Knight, MD, Pain Medicine and Spine Care, VA Medical Center, Wade Park, 10701 East Blvd, Cleveland, OH 44106. E-mail address: [email protected].

1084-208X/$ -see front matter Published by Elsevier Inc. doi:10.1053/j.trap.2009.05.005

Epidemiology Low back pain is one of the most common musculoskeletal complaints and is a leading cause for seeking medical assistance.2 Approximately 80% of the general population will experience one episode of low back pain in their lifetime.2 Evidence suggests that it is becoming more prevalent.3 Although it is thought that most low back pain episodes resolve, some studies suggest that chronic low back pain persists in many patients.4,5 Disability statistics in the United States suggest that disability from musculoskeletal disorders is rising.6 Not only is back pain disabling, it is costly. Medical expenditures among individuals with spine problems is almost double that of individuals without spine problems.7

Background In 1934, Harvard-trained neurosurgeon William Jason Mixter published with Joseph Barr the landmark New England Journal of Medicine article that fundamentally changed the medical understanding of the relationship between the intervertebral disc and radicular pain known then as sciatica.

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In this and subsequent articles, Mixter and Barr8 also confirmed the role of discectomy in relieving pain through the surgical repair of disc bulge or rupture. Although discectomy has become the most common surgical spine intervention and the standard treatment for radicular pain from disc herniation, the current trend in all spinal surgery has been toward less invasive techniques.9 Percutaneous techniques for disc decompression included chemonucleolysis, percutaneous lumbar discectomy, intradiscal laser discectomy, and the object of our discussion, percutaneous nucleoplasty. Smith and Garvin10,11 introduced chymopapain chemonucleolysis to treat herniated disc in the 1960s. Chemonucleolysis is a minimally invasive percutaneous procedure that involves the dissolving of the gelatinous nucleosus material in an intervertebral disc by the injection of an enzyme chymopapain. Chemonucleolysis was considered as a conservative alternative to disc surgery. By the 1970s it was controversial due to serious complications, such as anaphylactic shock and leakage of the chymopapain leading to nerve or cord damage. Chemonucleolysis is effective on protruded and extruded discs, but not on sequestered disc injuries. In a review article by long-time proponent E.J. Nordby12 and colleagues, they showed that from 1982 to 1991, a total of 121 adverse events in 135,000 patients were reported to the Food and Drug Administration and investigated. There were 7 cases of fatal anaphylaxis, 24 infections, thirty-two bleeding problems, thirty-two neurologic events, and 15 miscellaneous occurrences. Overall mortality rate was 0.019%. All categories of complications were deemed less frequent than complications with laminectomy. Garvín argued that his and other researchers’ long-term results show that improvement after chemonucleolysis was maintained, whereas the outcome after laminectomy was thought to deteriorate with time. Although chemonucleolysis outcomes may have been good, patients suffered severe anaphylactic reactions and intense muscle spasms that required hospitalization, decreasing the popularity of this procedure.13 Percutaneous lumbar discectomy was next described as a treatment for disc herniation. In 1983, Friedman14 described a technique that he stated was technically easy and had good results. In 1989, Hijikata15 claimed that he developed a percutaneous nucleotomy in 1975—a technique that could be performed in the radiology department under local anesthetic. Using this technique, intradiscal pressure was reduced, and relief of pain from the disc was obtained. Using this procedure, extraction of the herniated portion of the disc is not achieved. Percutaneous discectomy procedures have been shown only to equal placebo in effectiveness, and their use has declined.9 Although percutaneous discectomy procedures may have been developed independently in different parts of the world, it remains part of the trend in the treatment of disc diseases away from open surgical disc decompression and toward percutaneous or minimally invasive techniques. In 1986, Choy and Ascher developed percutaneous laser disc decompression (PLDD).16 The FDA approved PLDD in 1991. In this technique, Nd:YAG laser energy is intro-

duced into a herniated disc under fluoroscopy. The treatment principle of laser discectomy is based on the concept of the intervertebral disc being a closed hydraulic system. By reducing the intradiscal pressure, the herniated disc can recede toward the middle, thereby reducing the pressure on the nerve roots. The laser energy is used to evaporate water in the nucleus pulposus. It is repeatable, relatively noninvasive, and usually provides immediate relief. It is also felt to decrease supporting tissue disruption caused by a laminectomy and discectomy. Although percutaneous laser disc decompression has been in existence for nearly 20 years, the scientific evidence supporting it remains weak, due to a lack of randomized, controlled, prospective studies.17 Nucleoplasty uses radiofrequency energy to dissolve nuclear material through molecular dissociation. Nucleoplasty radiofrequency energy breaks apart proteoglycans, leading to a change in the internal environment of the affected nucleus pulposus with reduction of intradiscal pressure. Byproducts of this procedure are elementary molecules and inert gases, which escape from the disc via the needle. Minimal surrounding tissue change has been confirmed histologically,18 confirming the safety of the procedure compared with other minimally invasive techniques. Radiofrequency has been demonstrated in live animals to reduce disc pressure19 as well as in human cadavers.20 Excessive removal of tissue may not be beneficial, however. A correlation was noted between the amount of disc tissue removed and the amount of disc space collapse at 10 years in one longitudinal study on percutaneous nucleotomy.21 Nucleoplasty appears to remove precise amounts of tissue without clinically significant evidence of damage to surrounding tissues.22 Further, although there is reduction of pressure in the nucleus immediately after ablation,23 it is unclear what effect there is on the tension in the innervated outer annulus. Also, there is evidence that reduction of nucleus pressure may block chondrocyte metabolism that could lead to more disc dehydration.24,25 Some believe radiofrequency ablation does not effect change via pressure reduction but rather by chemical changes.26,27 Chemical changes as demonstrated by decreased inflammatory markers have been demonstrated in abnormal nuclear cells.28 O’Neill and colleagues demonstrated that nucleoplasty alters the expression of inflammatory cytokines in degenerated discs, leading to a decrease in IL-1 and an increase in IL-8.27 They hypothesize that because IL-1 is catabolic in injured tissue and IL-8 is anabolic, nucleoplasty may initiate a repair response in the disc. Discogenic pain is thought to be in part related to inflammatory chemicals, such as matrix metalloproteinases,29 prostaglandin PGE2,28 interleukins,30 and inflammatory cells influx due to chemical signals.31

Indications Nuleoplasty is an emerging technology. Emerging procedures are ones that are used by pain practitioners to address

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a need, but which pain practitioners cannot yet establish how and when they should most efficiently be practiced.32 Nucleoplasty was FDA-approved in 1999. Few pain societies have outlined specific indications for nucleoplasty. For some proponents, percutaneous disc decompression using nucleoplasty is to be limited to individuals with radicular pain that has persisted for more than 6 months despite conservative measures, including epidural steroid injections and physical therapy. Other proponents advocate the procedure for degenerative discs leading to axial nonradicular discogenic pain as evidenced by discogram which demonstrates concordant pain at the suspected level.33 The American Society of Interventional Pain Physicians (ASIPP) indications for nucleoplasty (see Table 1) include magnetic resonance imaging studies should reveal a contained disc protrusion (less than 6 mm), at least 50% of the disc height maintenance, discogram with negative control disc, and failure of conservative treatment.34 Opinions vary on the use of a discogram. Some feel it is essential before proceeding with nucleoplasty, for it allows evaluation of the annulus and establishes concordant pain.33 Singh has studied nucleoplasty for radicular pain and primary discogenic pain. Selection criteria vary. Welch found best results with broad-based herniations with radicular symptoms.35 Mirzai excluded candidates with back pain worse than leg pain.36 In his 2004 study, Singh focused on patient with back pain worse than leg pain, attributable to the disc. Nucleoplasty is contraindicated in the presence of infection, coagulopathy, tumor, or fracture at the suspected level. It is also not recommended if there is moderate or severe canal stenosis or significant scoliosis. Additional contraindications include more than two symptomatic levels, magnetic resonance imaging evidence of disc sequestration, or disc height ⬍50%. Inadequate disc height will preclude wand entry into the space.35 Significant psychiatric comorbidities also exclude candidates.

Technique Nucleoplasty should be performed under monitored intravenous sedation. The patient must be awake and maintain Table 1

Indications for nucleoplasty

1. Axial back pain and/or or radiculopathy secondary to a contained disc herniation (⬍6 mm) that has persisted greater than 6 months despite appropriate conservative treatment (including physical therapy, epidural steroid injections) 2. Iinvolvement of a maximum of two suspected levels 3. Discogram confirming the integrity of the outer annulus 4. Spinal stenosis secondary to disc herniation that is less than one-third the spinal canal diameter 5. No history of neurological deficit nor spinal surgery at the suspected level(s)

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Figure 1 Oblique view, showing “Scotty Dog” image with the cannula entering the disc just anterior to the superior articular process.

protective reflexes during the procedure. The intervertebral discs are poorly vascularized and are susceptible to discitis. The most common causative organism of discitis is Staphylococcus aureus.37 Thus, an antibiotic with Gram-positive coverage should be given before the procedure. Cefazolin 1 g is commonly used in patients with no known penicillin allergy. Boscardin’s study evaluating intradiscal levels of cefazolin shows that optimal levels were present 15 minutes after the bolus and were maintained for an additional 65 minutes.38 The back should be prepped with an alcoholbased chlorhexidine antiseptic solution, for this has been shown to have the greatest bacteriocidal activity.39 The patient is placed prone for the procedure and is prepped and draped in the usual sterile fashion. In the anteroposterior (AP) view, the endplates of the lumbar vertebrate are squared. The sterilely draped fluoroscope is then obliqued until the classic “Scotty Dog” image is seen. The target entry site into the disc is just anterior to the superior articular process (Figure 1). This is performed on the side at which the patient has pain (the same side as the disc herniation).35 The skin and subcutaneous tissue overlying this target are anesthetized with local anesthetic. At the L5-S1, a significant craniocaudal angulation is required, as shown in Figure 2. A modified double-needle entry can be employed where the skin is nicked with a scalpel and the 14-gauge Crawford cannula is advanced through this incision. Continuing with this oblique approach, the cannula is advanced until the disc is contacted. A paresthesia may be elicited if the exiting nerve root is contacted. When this occurs, the cannula position is adjusted until the paresthesia resolves. The AP view should be checked, and then the cannula is advanced through the annulus fibrosus. Cannula advancement is stopped when there is a loss of resistance signaling entry

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Figure 2 (A) Lateral views of wand entering the L5-S1 disc; note the significant angulation. (B) Anteroposterior view of wand entering the L5-S1 disc.

into the nucleus pulposus. AP and lateral views are then evaluated, as shown in Figure 3, to demonstrate needle position in alternate planes. The coblation wand is then introduced into the access cannula and advanced slightly into the nucleus pulposus. The cannula is then retracted a couple millimeters to ensure it is in the annulus fibrosus. Then, employing AP and lateral fluoroscopic guidance, the wand is advanced through the nucleus pulposus. Resistance increases when the annulus fibrosus is contacted and advancement should cease, as shown in Figure 4. A depth gauge is then advanced down the shaft to the cannula hub, marking the maximum treatment depth. The wand is then withdrawn to the posterior annular/nucleus border. The reference line on the wand is then oriented in

Figure 3

the 12 o’clock position. The ablation mode is activated and the wand is advanced until the anterior annular/nucleus border is reached. The coagulation mode is then activated and the wand is withdrawn to the cannula hub. For both ablation and coagulation, the wand should transit at 2 mm/second, generally 8 seconds per transit. The reference line is then positioned to the 2 o’clock position, and the ablation/coagulation treatment is repeated. This clockwise rotation is then repeated in the 4, 6, 8, and 10 o’clock positions, yielding a total of six channels. If resistance is encountered, wand movement should cease and its position should be fluoroscopically evaluated. If the resistance persists, advancement should be stopped and shorter channels should be accepted at this position. Upon completion, 1 mL of 0.25% Marcaine with 2 mg of cefazolin can be injected intradiscally for patient comfort and further antibiotic prophylaxis.

Anteroposterior and lateral views at L4-L5 level with the cannula in the annulus fibrosus.

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Figure 4 (A) Lateral views at L3-L4 level with the wand advanced through the nucleus pulposus and contacting the annulus fibrosus. (B) Anteroposterior views at L3-L4 level with the wand advanced through the nucleus pulposus and contacting the annulus fibrosus.

The patient may be discharged to home. The patient should refrain from ⬎25 lbs for 2 weeks and may benefit from an abdominal binder during this same period.

Discussion Disc nucleoplasty is a relatively new technique for disc decompression, and there is scant published literature and no randomized trials. However, there have been encouraging reports and studies about its use and outcome (Table 2). In 2002, Sharps and colleagues admitted 49 consecutive individuals with complaints of back pain with or without leg pain that was thought to be disc-related to an observational study. They all were confirmed to have a focal protrusion that was contained. One- 3-, 6-, and 12-month outcomes were assessed. The preprocedure and postprocedure visual analogue scale (VAS) differences were 4.28, 4.66, 4.75, and 3.3 at the 1-, 3-, 6-, and 12-month intervals, respectively.40 Of note was the decrease in VAS score in respondents from 41 at 3 months to 13 at 12 months. In 2005, Marin reported a retrospective comparison study.41 He compared nucleoplasty to coblation-assisted microdiscectomy. His population was young (average age 43) and predominantly male (65%). Study patients had discogenic low back pain and/or leg pain. His results were positive for both techniques with 80% reporting improvement in VAS scores at follow-up between 6 and 12 months. Singh and colleagues have reported on multiple trials. In their first study, clinical outcome data were analyzed for 67 patients with contained disc herniation with low back pain with or without leg pain who underwent percutaneous disc decompression with nucleoplasty after failing to respond to

conservative management. Provocative discography was completed. Follow-up data were collected for up to 12 months. Patient gender distribution was 70% female, 30% male, with a mean age of 44 years. The onset of the pain was predominantly nontraumatic in origin with an average duration of pain of 5.4 years ranging from 4 months to 29 years with history of previous surgical intervention in 13% of the patients. At 1 year, 80% of the patients demonstrated statistically significant improvement in numeric pain scores. Average preprocedure pain level for all patients was reported as 6.8, whereas average pain level was 4.1 at the 12-month follow-up period. Statistically significant improvement was observed in approximately two-thirds of patients in sitting, standing, and walking ability at 12 months.42 In 2003, the group was extended to 80 and the analysis was repeated with essentially the same results. Further, 15% of previously disabled patients were able to return to work.43 In 2004, his group published a prospective, nonrandomized, observational study of 49 individuals with a predominant back pain attributed to the disc pathology and confirmed by discography using International Association for the Study of Pain criteria. Outcomes included pain scale 1 to 10, patient report of percent improvement, and self report of sitting, standing, and walking tolerance. At 1 month, 80% of patients reported greater than 50% pain relief. At 12 months, greater than half reported greater than 50% relief. Functional improvements were reported by 46% of patients for sitting ability, 41% for standing ability, and 49% for walking ability at 12 months. Singh’s group’s emphasis appears to be on discogenic pain due to abnormalities of the inflammatory milieu. Discography is considered essential to evaluate both annular integrity and concor-

98 Table 2

Techniques in Regional Anesthesia and Pain Management, Vol 13, No 2, April 2009 Lumbar nucleoplasty studies with measures and outcomes

Study/Year

Population

Study design

Measures

Outcomes

Sharps 200240 Singh 200242

49 consecutive Back and/or leg pain 67 Back and/or leg Positive discography

Prospective Observational Prospective Observational

VAS 1, 3, 6, 12 months VAS Self report sitting, standing, ambulation tolerance At least 12 months

Singh 200343

80 Back and/or leg Positive discography

Prospective Observational

VAS Self report sitting, standing, ambulation tolerance Percent pain relief Return to work At least 12 months

Singh 200433

49 Predominant back pain Positive discography

Prospective Observational

VAS Percent pain relief Self report sitting, standing ambulation At least 12 months

Marin 200541

Back and/or leg pain

Pain scale

Gerszten 200656

67 Leg pain

Retrospective Comparison Nucleoplasty [Coblation vs CAM (coblation-assisted microdiscectomy)] Prospective Observational

Significant improvement at all intervals Significant improvement in VAS at 12 months in 80% of patients Significant improvement in self report function in 60% at 12 months Significant improvement in VAS at 12 months in 75% of patients Significant improvement in self report function in 50% at 12 months 54% report greater than 50% pain relief at 12 months 15% return to work Significant improvement in VAS at 12 months; 53% report greater than 50% pain relief at 12 months Significant improvement in self report function in sitting and standing 80% Reported improvement

Mirzai 200736

52 Leg pain

Prospective Observational

VAS Oswestry disability questionnaires Analgesic intake Patient satisfaction

dant discogenic pain. If there is an annular tear, this is considered a relative counter indication to the procedure.33 In 2007, a prospective study of 52 patients was completed by Mirzai and colleagues in which they demonstrated

VAS SF36 EQ5D

VAS were only available for 23 patients at 6 months SF36 were significantly improved but only available for 20 patients at 6 months EQ5D were significantly improved but only available for 20 patients at 6 months VAS improved 7.5–3.1 at 6 months and to 2.1 at 12 months Mean Oswestry index decreased from 42.2 to 24.8 at 6 months and to 20.5 at 1 year Analgesic consumption was stopped or reduced in 42 patients (85%) at 6 months and in 46 patients (94%) at 1 year Patient satisfaction was 88% at 1 year

a mean decrease in the VAS from 7.5 to 3.1 at 6 months.36 Selection criteria included only patients with contained disc herniations of ⬍6 mm, annular integrity, and relative disc height preservation. Discography was completed immedi-

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ately before nucleoplasty to assure annular integrity. Of note, discography was completed only to assure annular integrity, not concordant pain. Improved pain results were long-lasting with follow-up into 1 year. Further patient satisfaction was 88% at final follow-up. No complications were noted with the procedure. In 2008, Li and colleagues reported an observational trial of 126 patients with contained cervical herniations treated with percutaneous cervical nucleoplasty.44 Levels of involvement were 21 cases at C3-4, 30 cases at C4-5, 40 cases at C5-6, and 35 cases at C6-7. Follow-up ranged from 14 to 36 months with average being 24 months. Pre-procedure report of VAS was 7.35 (⫾0.44). After procedure, VAS was consistently 2.42–2.44 (⫾0.71 or 0.72) at 2 weeks 1 month 3 months 6 months, and 12 months. In 2009, another study was published by Birnbaum regarding cervical nucleoplasty.45 After failed conservative treatment over an average time period of 3 months, the group treated 26 patients with a contained herniated prolapse or protrusion with radicular arm pain with percutaneous nucleoplasty. A randomized control group of 30 patients was treated alone conservatively with medical and physical therapy in the same period. Remarkable results were noted with 2-year follow-up. The average preoperative VAS was 8.8. In selected individuals who had a further check-up at 2 years, they found an average pain reduction with the visual pain score (VAS) to 2.3. The VAS was checked 24 hours 1 week, and 3, 6, 12, and 24 months postoperatively. No complications with this method were seen. The conservative treatment control patients had an average VAS of 8.4. Using conservative treatment with physical therapy, physiotherapy, analgesics, and perineural injections, they reported a diminution of the VAS to 5.1 after 2 years. One randomized, controlled, multicenter study is being done, and initial results have recently been presented comparing nucleoplasty to fluoroscopically guided transforaminal epidural steroid injection for radicular pain from contained disc herniations. Preliminary results showed nucleoplasty was associated with significantly greater pain reduction and improved quality of life scores.46

99 colleagues prospectively assessed side effects and complications. The most common side effects at 24 hours were soreness at the needle site, new numbness and tingling, increased low back pain, and new low back pain. At 2 weeks, these side effects were gone, but there was rarely some numbness and tingling. No other complications were reported.48 Infection, bleeding, and nerve damage are well-known potential complications of interventional spine procedures. The intervertebral discs are poorly vascularized and are susceptible to discitis. The most common causative organism of discitis is Staphylococcus aureus.49 Discitis has not been reported after nucleoplasty, although Li describes a suspected case.44 In this patient, who had undergone a cervical nucleoplasty at an outside hospital, the MRI had findings consistent with discitis, but clinical symptoms did not support the diagnosis. Regardless, it is a known complication of discography, a similar procedure in which the poorly vascularized disc is entered percutaneously. Discitis can have an insidious onset and is a challenge to diagnose. It should be suspected when there is a worsening or change in pain postprocedure. Infectious laboratory studies and MRI evaluation may suggest discitis, but are not always positive. Definitive confirmation is obtained with a disc biopsy. In discography, the incidence of discitis is reported to be less than 1 in every 400 patients.50 When intradiscal antibiotics are used, the incidence has been reported to be 0%. Nerve root trauma can occur at the time of cannula placement. It is also theorized that nerve damage could occur if the wand is retracted too far and makes contact with the cannula while activated. The thermal energy would then be conducted through the cannula, potentially damaging any tissue that it contacts.51 Vascular injury could occur if the device punctures an artery or a vein. Although it has not been reported, if the wand was advanced too far, it could extend through the annular fibrosis and damage blood vessels. The epidural space also contains blood vessels that could be damaged. Vertebral endplates could be damaged if the cannula was misdirected. The long-term effects of nucleoplasty on the discs, adjacent levels, and spinal stability are unknown. Boswell has reported a case during an attempted discography when the prophylactic antibiotic was accidently injected intrathecally and the patient seized.52

Complications Complications from nucleoplasty are thought to be rare. There are multiple prospective studies reported above that report no significant complications. In the literature, two complications have been reported. Epidural fibrosis was reported by Smuck and colleagues, which led to temporary radicular pain that spontaneously resolved.47 The patient had initial relief from the procedure but several months postprocedure presented with a radiculopathy. Repeat magnetic resonance imaging revealed the epidural fibrosis. Li and colleagues reported one episode of wand breakage.44 The wand fragment ultimately could not be retrieved, yet the patient still had a good clinical outcome. Bhagia and

Conclusions Chronic back pain generated from disc disease is a serious disease affecting nearly 10 million individuals annually in the United States leading to both pain and disability. The optimal management of patients with low back pain remains a challenge with social, economic, and clinical implications. It is a costly disease with total costs estimated at between 100 and 200 million dollars annually.53 The prevalence of chronic lower back pain has more than doubled in 15 years.54 Medications are frequently not helpful. Spine surgery is invasive and expen-

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sive. Nucleoplasty is a relatively new technology that allows disc decompression with minimal tissue derangement of contained disc herniations. There is some evidence that it not only reduces disc pressure but may also change the inflammatory milieu within the disc to discourage further degeneration. Indications for the best use of nucleoplasty are being evaluated, but it seems to be limited to contained herniations. There is prospective observational evidence supporting both the use of nucleoplasty in disc herniation leading to leg pain from nerve compression as well as primary discogenic pain without leg pain. Currently, there is one randomized trial comparing nucleoplasty with conservative epidural steroid injection care. Due to its lack of tissue derangement and encouraging prospective data, further research is suggested to support this minimally invasive technique.55

References 1. Singh V: Scientific basis for nucleoplasty. Tech Reg Anesth Pain Med. 9:13-24, 2005 2. Deyo RA, Mirza SK, Martin BI: Back pain prevalence and visit rates: Estimates from US national surveys, 2002. Spine 31:2724-2727, 2006 3. Freburger JK, Holmes GM, Agans RP, et al: The rising prevalence of chronic low back pain. Arch Intern Med 169:251-258, 2009 4. Elliott AM, Smith BH, Hannaford PC, et al: The course of chronic pain in the community: Results of a 4-year follow-up study. Pain 99:299307, 2002 5. Enthoven P, Skargern E, Oberg B: Clinical course in patients seeking primary care for back or neck pain: A prospective 5-year follow-up of outcome and health care consumption with subgroup analysis. Spine 29:2458-2465, 2004 6. Social Security Administration Office of Policy: Annual Statistical Report on the Social Security Disability Insurance Program, 2005. SSA publication no. 13–11826. Washington, DC, Social Security Administration, 2006 7. Martin BI, Deyo RA, Mirza SK, et al: Expenditures and health status among adults with back and neck problems. J Am Med Assoc 299: 656-664, 2008 8. Mixter WJ, Barr JS: Rupture of the intervertebral disc with involvement of the spinal canal. N Engl J Med 211:210-215, 1934 9. Gibson JN, Waddell G: Surgical interventions for lumbar disc prolapse: Updated Cochrane review. Spine 32:1735-1747, 2007 10. Smith L: Enzyme dissolution of the nucleus pulposus in humans. J Am Med Assoc 187:137-140, 1964 11. Smith L, Garvin PJ, Jennings RB, et al: Enzyme dissolution of the nucleus pulposus. Nature 198:131-132, 1963 12. Nordby EJ, Fraser RD, Javid MJ: Chemonucleolysis. Spine 21:11021105, 1996 13. Wittenberg RH, Oppel S, Rubenthaler FA, et al: Five-year results from chemonucleolysis with chymopapain or collagenase: A prospective randomized study. Spine 26:1835-1841, 2001 14. Friedman WA: Percutaneous discectomy: An alternative to chemonucleolysis? Neurosurgery 13:542-547, 1983 15. Hijikata S: Percutaneous nucleotomy. A new concept technique and 12 years experience. Clin Orthop Relat Res 238:9-23, 1989 16. Ascher PW: Application of the laser in neurosurgery. Lasers Surg Med 2:91-97, 1986 17. Schenk B, Brouwer PA, Peul WC, van Buchem MA: Percutaneous laser disk decompression: A review of the literature. AJNR Am J Neuroradiol 27:232-235, 2006

18. Lee MS, Cooper G, Lutz GE, et al: Histologic characterization of coblation nucleoplasty performed on sheep intervertebral discs. Pain Physician 6:439-442, 2003 19. Podhajsky RJ, Belous A, Finch PM, et al: Effects of monopolar radiofrequency heating on intradiscal pressure in sheep. Spine J 7:229234, 2007 20. Chen YC, Lee SH, Chen D: Intradiscal pressure study of percutaneous disc decompression with nucleoplasty in human cadavers. Spine 28: 661-665, 2003 21. Mochida J, Toh E, Nomura T, et al: The risks and benefits of percutaneous nucleotomy for lumbar disc herniation. A 10 year longitudinal study. J Bone Joint Surg Br 83:501-505, 2001 22. Chen YC, Lee SH, Saenz Y, et al: Histologic findings of disc, end plate and neural elements after coblation of nucleus pulposus: An experimental nucleoplasty study. Spine J 3:466-470, 2003 23. Hellinger J, Linke R, Heller H: A biophysical explanation for Nd:YAG percutaneous intradiscal laser nucleotomy. J Clin Laser Med Surg 19:235-238, 2001 24. Hutton WC, Elmer WA, Boden SD, et al: The effect of hydrostatic pressure on intervertebral disc metabolism. Spine 24:1507-1515, 1999 25. Hutton WC, Elmer WA, Bryce LM, et al: Do the intervertebral disc cells respond to different levels of hydrostatic pressure? Clin Biomech 16:728-734, 2001 26. Keshari KR, Lotz JC, Link TM, et al: Lactic acid and proteoglycans as metabolic markers for discogenic back pain. Spine 33:312-317, 2008 27. O’Neill CW, Liu JJ, Leibenberg E, et al: Percutaneous plasma decompression alters cytokine expression in injured porcine intervertebral discs. Spine J 4:88-98, 2004 28. Rhyu KW, Walsh AJ, O’Neill CW, et al: The short-term effects of electrosurgical ablation on proinflammatory mediator production by intervertebral disc cells in tissue culture. Spine J 7:451-458, 2007 29. Groupile P, Jayson MI, Valat JP, et al: Matrix metalloproteinases: The clue to intervertebral disc degeneration? Spine 23:1612-1626, 1998 30. Podichetty VK: The aging spine: The role of inflammatory mediators in intervertebral disc degeneration. Cell Mol Biol 53:4-18, 2007 31. Ulrich JA, Liebenberg EC, Thuillier DU, Lotz JC: ISSLS prize winner: Repeated disc injury causes persistent inflammation. Spine, 32:28122819, 2007 32. Bogduk N (ed): Practice Guidelines-Spinal Diagnostics and Treatment Procedures. San Francisco, CA, ISIS, 2004, pxvii 33. Singh V, Piryani C, Liao K: Role of percutaneous disc decompression using coblation in managing chronic discogenic low back pain: A prospective, observational study. Pain Physician 7:419-425, 2004 34. Manchikanti L, Singh V, Kloth D: Interventional Pain Management Practice Policies, American Society of Interventional Pain Physicians, 2009 35. Welch WC, Gertzen PC: Alternative strategies for lumbar discectomy: intradiscal electrothermy and nucleoplasty. Neurosurg Focus 13:1-8, 2002 36. Mirzai H, Tekin I, Yaman O, et al: The results of nucleoplasty in patient with lumbar herniated disc: A prospective clinical study of 52 consecutive patients. Spine J 7:88-93, 2007 37. Cohen SP, Larkin TM, Barna SA, et al: Lumbar discography: A comprehensive review of outcome studies, diagnostic accuracy, and principles. Reg Anesth Pain Med 30:163-183, 2005 38. Boscardin JB, Ringus JC, Feingold DJ: Human intradiscal levels with cefazolin. Spine 17:S145-S148, 1992 (suppl) 39. Hebl JR: The importance and implications of aseptic techniques during regional anesthesia. Reg Anesth Pain Med 31:311-323, 2006 40. Sharps LS, Isaac Z: Percutaneous disc decompression using nucleoplasty. Pain Physician 5:121-126, 2002 41. Marín FZ: CAM versus nucleoplasty. Acta Neurochir Suppl 92:111114, 2005 42. Singh V, Piryani C, Liao K, Nieschulz S: Percutaneous disc decompression using coblation (nucleoplasty) in the treatment of chronic discogenic pain. Pain Physician 5:250-259, 2002

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Decompression Technique for Disk Protrusion

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