You are in: eMedicine Specialties > Neurology > Headache and Pain Intradiscal Electrothermal TherapyArticle Last Updated: Feb 27, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Steven A Barna, MD, Medical Director of MGH Pain Clinic, Instructor of Anaesthesia, Department of Anesthesia and Critical Care, Harvard Medical School, Massachusetts General Hospital Steven A Barna is a member of the following medical societies: American Society of Interventional Pain Physicians Coauthor(s): Aathi R Thiyagarajah, MD, Consulting Staff, Department of Rehabilitation Medicine and Pain Management, Oaktree Medical Center; Juan Santiago-Palma, MD, Consulting Staff, Department of Physical Medicine and Rehabilitation, Private Practice; Eugenia-Daniela Hord, MD, Instructor, Departments of Anesthesia and Neurology, Massachusetts General Hospital Pain Center, Harvard Medical School; Ricardo Vallejo, MD, PhD, Adjunct Professor of Biology, Illinois State University; Director of Research, Staff Pain Medicine, Millennium Pain Center 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; Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital; Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants Author and Editor Disclosure Synonyms and related keywords: chronic low back pain, discogenic low back pain, disc disease, disk disease, intradiscal electrothermal annuloplasty, IDEA, intradiscal electrothermal therapy, IDET INTRODUCTIONSection 2 of 11
  Intradiscal electrothermal annuloplasty (IDEA) or intradiscal electrothermal therapy (IDET), as it is known commercially, is a new and minimally invasive technique for the treatment of discogenic low back pain. IDET involves the percutaneous threading of a flexible catheter into the disk under fluoroscopic guidance. The catheter, composed of thermal resistive coil, heats the posterior annulus of the disk, causing contraction of collagen fibers and destruction of afferent nociceptors. Although initial clinical studies suggest that IDET might be effective in approximately 70% of patients with chronic unremitting low back pain, its efficacy has not been assessed in randomized controlled clinical trials. The objectives of this article are to review published reports and present a general overview of IDET. PATIENT SELECTIONSection 3 of 11
As with other interventional procedures, proper patient selection increases the chances of a favorable outcome. IDET should be considered in patients who have had discogenic low back pain for more than 6 months and who have not responded to conservative treatment. Ideal candidates are patients with a single affected disk as determined by MRI and discography. Patients with predominant complaint of axial pain with or without some non-radiating limp pain are selected. Patients with severe radicular symptoms due to a herniated disk or patients with severe spinal stenosis are not good candidates. A severely collapsed disk (>50% of disk height lost) might not respond well to IDET treatment because of technical difficulties in catheter placement and the procedure's questionable effect on high-grade disk injury. Similarly, severely disrupted disk morphology as revealed by discography may not respond well. Patients older than 55 years may have lower success rates because of poorer healing. Cigarette smoking may affect annular collagen tissue and hinder adequate recovery following the procedure.
MECHANISM OF ACTIONSection 4 of 11
IDET is thought to decrease discogenic pain by two different mechanisms: thermal modification of collagen fibers and destruction of disk nociceptors. Breakage of heat-sensitive hydrogen bonds of the collagen fibers causes collagen contraction. With disk temperatures reaching 650°C, collagen may contract as much as 35% from its original size. The tightening of annular tissue may enhance the structural integrity of degenerated disk and repair the annular fissures. The process of disk restructuring (as shown by time courses of patients' pain relief) may take several months to reach its full extent. IDET might also cause destruction of sensitized nociceptors in the annular wall. Denervation by thermal energy is used widely for peripheral and central nervous system lesioning and might contribute to partial initial pain relief following the IDET procedure. TECHNICAL ASPECTSSection 5 of 11
The technique for approaching the disk for IDET is similar to the technique used for discography. After the skin is infiltrated with local anesthetic, a 17G introducer needle is inserted into the disk, guided by oblique fluoroscopic imaging. Once the position of the needle in the nuclear cavity is established by anteroposterior and lateral fluoroscopic views (see Images 1-2), the thermal catheter is inserted through the needle. The SpineCATH System thermal catheter is used (Oratec Interventions, Inc., Menlo Park, Calif). The catheter should be placed circumferentially around the inner surface of the posterior annulus (see Images 3-5). Once the catheter is in satisfactory position, it is heated from 37°C to 65 °C. After the temperature has remained at 65° for 1 minute and the patient has not complained of excessive pain, the temperature is increased by 1°C every 30 seconds until it is between 80° and 90°C. The actual temperature of the annular tissue is as much as 15°C lower than the temperature of the catheter tip. Comprehensive patient and cadaver temperature mapping studies have shown the safety of placing heating catheters within the disk tissue. In these studies, the temperature of the epidural space reached a maximum of 39.30°C when the catheter tip was heated to 90°C. In the same studies, the disk tissue reached a maximum temperature of 72°C and the outer annulus 46°C with catheter tip temperatures of 90°C. POSTPROCEDURE CARESection 6 of 11
The physician must realize, and point out to the patient, that recovery is gradual. During the first 7 days after the procedure, patients might experience a significant increase in pain. Significant pain relief may take 8-12 weeks. The "healing" process reaches its peak 4 months after the procedure. During that period, the patient must limit physical activity and follow a carefully structured rehabilitation program. In general, patients should not return to any kind of heavy physical work during the first 4 months. A gradual increase in daily activities is recommended. The patient should do only minimal sitting or standing during the first few days after treatment, and a corset should be worn during the first 6 weeks. Athletic activities can be resumed gradually starting 6 months after the IDET procedure.
REVIEW OF PUBLISHED STUDIESSection 7 of 11
The first published report of IDET was by Saal and Saal. In that study, a cohort of 25 patients was shown to have improved clinical outcomes 6 months after they underwent IDET. Karasek and Bogduk, in a case-controlled study, compared the outcomes of 35 patients treated with IDET with those of 17 patients who were unable to undergo IDET because of lack of insurance coverage.
Saal and Saal completed a prospective case series of patients with 1 year of follow-up. Sixty-two patients were selected for IDET from a pool of 1116 patients with low back pain who did not respond to at least 6 months of aggressive conservative care. Follow-up was at 1 year, and outcomes were analyzed by using preprocedural and postprocedural VAS, SF-36, and return-to-work status. Of the 62 patients treated, 44 improved their VAS by a mean of 3 points (P < .001). Physical function scores improved in 71% of the patients and showed a mean change of 20 (P < .001). Bodily pain scores improved in 74% of the patients, with a mean change of 17.4. Ninety-two percent of the patients returned to work. Shadid et al studied 145 consecutive patients referred for IDET after having positive discography findings for discogenic back pain. Of these, 120 were available for follow-up, with a mean duration of 18 months. The average duration of preprocedural symptoms was 39.8 months. Scores on a numerical rating scale and activity levels were monitored. Overall, approximately one third of patients improved, one third remained unchanged, and one third became worse. Fifty-five percent of the patients stated they would not repeat the procedure. Pauza et al performed a randomized, placebo-controlled trial of IDET in which patients in the IDET group displayed greater mean improvements in pain, disability, and depression. Animal studies have been reported. Posterolateral anular lesions were experimentally induced and allowed to mature for 12 weeks in the intervertebral disks of sheep. IDET was performed in an attempt to denervate and repair the annular lesion. The histologic and immunohistochemical effects of IDET were studied. Vascular granulation tissue and posterior anular neoinnervation were observed in the experimentally induced posterolateral anular lesions. IDET delivered at 90°C in the sheep consistently heated the posterior annulus and the nucleus to a temperature normally associated with coagulation of nociceptors and collagen contraction. IDET did not denervate the posterior annular lesion. Thermal necrosis was observed within the inner anulus and adjacent nucleus from 6 weeks after IDET. The reported benefits from IDET appear to be related to factors other than denervation and repair. IDET-induced stress concentrations in disks obtained from cadavers have been analyzed. IDET has a significant but inconsistent effect on compressive stresses within intervertebral disks. These results may partly explain the variable clinical success of IDET. Past literature review has revealed that most patients have reported improvement in symptoms following both spinal fusion and the IDET procedure. The IDET procedure appears to offer sufficiently similar symptom amelioration to spinal fusion without the attendant complications in early studies. However, some authors consider IDET an antecedent rather than alternative to spinal fusion based on final outcome studies. COMPLICATIONSSection 8 of 11
Complications due to IDET are infrequent. In a retrospective study, the complications of 1675 IDETs performed at 5 different spine centers were reviewed. In the same study, data related to 35,000 SpineCATH intradiscal catheters from the medical device reports (MDRs) of the United States Food and Drug Administration (FDA) were analyzed. A total of 6 nerve root injuries were reported. All but one of the nerve root injuries were reported as occurring at the time of disk puncture. Five of the six completely resolved and one case was resolving. No cases of discitis were reported. Six cases of post-IDET disk herniation were reported at the treated level 2-12 months after treatment. Four resolved with nonoperative care, and two required disk excision. Nineteen cases of catheter breakage were reported. All were associated with repeated catheter manipulation that resulted in kinking. In 16 of these, the catheters were left in the discs; none of these cases have been associated with any patient morbidity. Eight cases of superficial skin burn at the needle puncture site were reported. A case of post-IDET bladder dysfunction was reported. A fatal case of an unintentional dose of intrathecal cefazolin, which had been diluted in the nonionic contrast agent that was used to confirm needle placement, has been reported. It is recommended that cefazolin not be mixed with the contrast agent used to document initial needle placement during discography. CONCLUSIONSection 9 of 11
IDET is an innovative tool for the treatment of discogenic back pain. Initial reports suggest that IDET is effective in 60-70% of patients with chronic discogenic low back pain who have not improved with a comprehensive nonoperative program. IDET is minimally invasive and has a low complication rate and therefore might offer advantages over surgery. However, the outcomes and cost of IDET have not been compared with those of fusion and chronic pain management. Validation of the initial reports of IDET in placebo-controlled randomized trials is needed. In practice, back and some leg pain of discogenic origin is a common presentation. The IDET procedure afforded improvements in leg pain that correlated well with improvements in back pain. MULTIMEDIASection 10 of 11
REFERENCESSection 11 of 11
Intradiscal Electrothermal Therapy excerpt Article Last Updated: Feb 27, 2007 | ||||||||||||||||||||||||||||||||||||||||
