Review of Knee Joint Innervation: Implications for Diagnostic Blocks and Radiofrequency Ablation.

OBJECTIVE: To determine if commonly used knee radiofrequency ablation (RFA) techniques would be able to completely denervate the knee joint. METHODS: A comprehensive search of the literature on knee joint innervation was conducted using the databases Medline, Embase, and PubMed from inception through February 1, 2019. Google Scholar was also searched. Data on the origin, number of articular branches, course, distribution, and frequency of each nerve innervating the knee joint were extracted from the included studies and compared in order to identify variations. RESULTS: Twelve studies of anterior knee joint innervation and six studies of posterior knee joint innervation were included. The anterior knee joint was innervated by 10 nerves and further subdivided into two parts (anteromedial and anterolateral) or four quadrants (superomedial, inferomedial, superolateral, and inferolateral) based on innervation patterns; the posterior knee joint was innervated by two or three nerves, most commonly via the popliteal plexus. There is a lack of precise, validated anatomic targets identifiable with fluoroscopy and ultrasound for knee diagnostic blocks and RFA. Only three of the 12 or potentially 13 nerves innervating the knee joint are targeted by commonly used knee RFA techniques. CONCLUSIONS: Commonly used knee RFA techniques would not be able to completely denervate the knee joint. It may not be necessary to capture all of the nerves, but only the nerves mediating a patient's pain. Further clinical studies are required to validate specific diagnostic blocks and evaluate clinical outcomes using rigorous diagnostic blocks and anatomically specific knee RFA techniques.

Anatomical Comparison of Radiofrequency Ablation Techniques for Sacroiliac Joint Pain.

Objective: To compare the percentage of sacral lateral branches (LBs) that would be captured if lesions were created by seven current sacroiliac joint (SIJ) radiofrequency ablation (RFA) techniques: three monopolar and four bipolar. Design: Cadaveric fluoroscopy study. Setting: Anatomy and surgical skills laboratories. Subjects: Forty cadaveric SIJs. Methods: LBs were exposed, radiopaque wires were sutured to LBs, and anterior-posterior fluoroscopic images through the S1 superior endplate were obtained. Lesions that would be created by 17 versions of seven current SIJ RFA techniques were mapped on the fluoroscopic images. These 17 versions were compared: 1) percentage of LBs that would be captured; 2) percentage of SIJ specimens in which 100% of LBs would be captured; and 3) percentage of LBs that would not be captured at each level (S1-S4). Results: Both the mean LB and 100% capture rates were greater for the bipolar techniques (93.4-99.7% and 62.5-97.5%, respectively) than for the monopolar techniques (49.6-99.1% and 2.5-92.5%, respectively) evaluated. For the bipolar techniques, 1.5-29.2% of LBs would not be captured at S1 and 0% at S2-S4 vs 0-29.2% at S1-S4 for the cooled monopolar techniques vs 36.9-100% at S1-S4 for the conventional monopolar technique. Conclusions: The findings suggest that, if lesions were created, the RFA needle placement locations of the bipolar techniques evaluated may be capable of capturing all LBs, but those of the current monopolar techniques evaluated may not. Future in vivo imaging studies are required to compare the lesion morphology generated by different SIJ RFA techniques and correlate the findings with clinical outcomes.

Proposed Optimal Fluoroscopic Targets for Cooled Radiofrequency Neurotomy of the Sacral Lateral Branches to Improve Clinical Outcomes: An Anatomical Study.

Background: Current sacroiliac joint (SIJ) cooled radiofrequency (RF) is based on fluoroscopic anatomy of lateral branches (LBs) in three specimens. Recent studies confirm significant variation in LB positions. Objectives: To determine if common fluoroscopic needle placements for cooled SIJ RF are adequate to lesion all S1-3 LBs. If not, would different targets improve lesion accuracy? Methods: The LBs of 20 cadavers were dissected bilaterally (40 SIJs), and 26 G radiopaque wires were sutured to the LBs. With a 10-mm radius ruler centered at each foramen, standard targets were assessed, as judged by a clockface on the right, for S1 and S2 at 2:30, 4:00, and 5:30 positions and at S3 at 2:30 and 4:00. Mirror image targets were assessed on the left. Assuming an 8-mm lesion diameter, the percentage of LBs that would not be ablated for each level was determined. Imaging through the superior end plate of S1 was compared against segment specific (SS) imaging. Results: Nine point four percent of LBs would not be ablated at S1 vs 0.99% at S2 vs 35% at S3, and 60% of the 40 SIJs would be completely denervated using current targets. SS imaging did not improve results. Alternate target locations could improve the miss rate to 2.8% at S1 and 0% at S3 and would ablate all LBs in 95% of SIJs. Conclusions: Using a conservative 8-mm lesion measurement, contemporary cooled RF needle targets are inadequate to lesion all target LBs. Modifications to current targets are recommended to increase the effectiveness of the procedure.

Safeguards to prevent neurologic complications after epidural steroid injections: consensus opinions from a multidisciplinary working group and national organizations.

BACKGROUND: Epidural corticosteroid injections are a common treatment for radicular pain caused by intervertebral disc herniations, spinal stenosis, and other disorders. Although rare, catastrophic neurologic injuries, including stroke and spinal cord injury, have occurred with these injections. METHODS: A collaboration was undertaken between the U.S. Food and Drug Administration Safe Use Initiative, an expert multidisciplinary working group, and 13 specialty stakeholder societies. The goal of this collaboration was to review the existing evidence regarding neurologic complications associated with epidural corticosteroid injections and produce consensus procedural clinical considerations aimed at enhancing the safety of these injections. U.S. Food and Drug Administration Safe Use Initiative representatives helped convene and facilitate meetings without actively participating in the deliberations or decision-making process. RESULTS: Seventeen clinical considerations aimed at improving safety were produced by the stakeholder societies. Specific clinical considerations for performing transforaminal and interlaminar injections, including the use of nonparticulate steroid, anatomic considerations, and use of radiographic guidance are given along with the existing scientific evidence for each clinical consideration. CONCLUSION: Adherence to specific recommended practices when performing epidural corticosteroid injections should lead to a reduction in the incidence of neurologic injuries.

Comparative effectiveness of lumbar transforaminal epidural steroid injections with particulate versus nonparticulate corticosteroids for lumbar radicular pain due to intervertebral disc herniation: a prospective, randomized, double-blind trial.

BACKGROUND: Lumbar transforaminal epidural injections are commonly utilized to treat radicular pain due to intervertebral disc herniation. OBJECTIVE: This study aims to determine if there was a major difference in effectiveness between particulate and nonparticulate corticosteroids for acute radicular pain due to lumbar disc herniation. DESIGN: A multicenter, double blind, prospective, randomized trial on 78 consecutive subjects with acute uni-level disc herniation resulting in unilateral radicular pain. All subjects received a single level transforaminal epidural steroid injection with either dexamethasone or triamcinolone. Repeat injections were allowed as determined by the blinded physician and subjects. Primary outcomes included: number of injections received, surgical rates, and categorical pain scores at 2 weeks, 3 months, and 6 months. Secondary outcomes included mean Oswestry Disability Index. RESULTS: Both triamcinolone and dexamethasone resulted in statically significant improvements in pain and function at 2 weeks, 3 months, and 6 months, without clear differences between groups. The surgical rates were comparable with 14.6% of the dexamethasone group and 18.9% of the triamcinolone group receiving surgery. There was a statistically significant difference in the number of injections received, with 17.1% of the dexamethasone group receiving three injections vs only 2.7% of the triamcinolone group. CONCLUSIONS: Transforaminal epidural corticosteroid injections are an effective treatment for acute radicular pain due to disc herniation, and frequently only require 1 or 2 injections for symptomatic relief. Dexamethasone appears to possess reasonably similar effectiveness when compared with triamcinolone. However, the dexamethasone group received slightly more injections than the triamcinolone group to achieve the same outcomes.

On the geometry of fluoroscopy views for cervical interlaminar epidural injections.

OBJECTIVES: To describe how the anatomy of the cervicothoracic vertebrae predicates the appropriate fluoroscopic views for confirming safe needle placement during the performance of interlaminar cervical epidural injections. METHODS AND RESULTS: Illustrations, cadaver models, and radiographic images were correlated and used to illustrate and derive a mathematical model to demonstrate the utility of a contralateral oblique fluoroscopic view during the performance of cervical interlaminar injections. CONCLUSIONS: When confirming needle placement during a cervical interlaminar epidural injection, in addition to the anterior-posterior fluoroscopic view, the oblique image, contralateral to the needle tip position, may provide superior information to that afforded by a lateral view.

Paraplegia following image-guided transforaminal lumbar spine epidural steroid injection: two case reports.

OBJECTIVE: To present two case reports of a rare but devastating injury after image-guided, lumbar transforaminal injection of steroids, and to explore features in common with previously reported cases. BACKGROUND: Image (fluoroscopic and computed tomography [CT])-guided, lumbar transforaminal injections of corticosteroids have been adopted as a treatment for radicular pain. Complications associated with these procedures are rare, but can be severe. CASE REPORTS: An 83-year-old woman underwent a fluoroscopically guided, left L3-L4, transforaminal injection of betamethasone (Celestone Soluspan). A 79-year-old man underwent a CT-guided, right L3-L4, transforaminal injection of methylprednisolone (DepoMedrol). Both patients developed bilateral lower extremity paralysis, with neurogenic bowel and bladder, immediately after the procedures. Magnetic resonance imaging scans were consistent with spinal cord infarction. There was no evidence of intraspinal mass or hematoma. CONCLUSION: These cases consolidate a pattern emerging in the literature. Distal cord and conus injury can occur following transforaminal injections at lumbar levels, whether injection is on the left or right. This conforms with the probability of radicular-medullary arteries forming an arteria radicularis magna at lumbar levels. All cases used particulate corticosteroids, which promotes embolization in a radicular artery as the likely mechanism of injury. The risk of this complication can be reduced, and potentially eliminated, by the utilization of particulate free steroids, testing for intra-arterial injection with digital subtraction angiography, and a preliminary injection of local anesthetic.

The significance of multifidus atrophy after successful radiofrequency neurotomy for low back pain.

OBJECTIVE: To determine the presence of lumbar multifidus atrophy and pain after successful lumbar medial branch radiofrequency neurotomy for zygapophysial joint mediated pain. DESIGN: A prospective observational analysis of 5 patients who had undergone successful unilateral radiofrequency neurotomy (RFN) of the lumbar medial branch divisions of the lumbar dorsal rami. At 17 to 26 months after RFN, 3 blinded radiologists evaluated the relative composition and size of the multifidus muscle at different segmental levels on lumbar magnetic resonance imaging (MRI). They were asked to determine the lesioned levels by evidence of multifidus atrophy. The accuracy of predicting the correct side and level lesioned was evaluated. SETTING: Private spine practice in Tyler, Texas. PATIENTS: Five patients who had unilateral lumbar medial branch RFN for proven lumbar zygapophysial joint-mediated pain were selected. INTERVENTIONS: MRI of the lumbar spine at a mean of 21 months (range, 17-26) after successful lumbar RFN. OUTCOME MEASURES: Multifidus atrophy on a lumbar MRI, pain assessment and use of cointerventions. RESULTS: Diffuse lumbar multifidus atrophy was detectable with MRI. However, radiologists could not reliably predict the side and segments lesioned. Despite denervation of the multifidus, at 12 months after RFN all subjects had ongoing pain relief and did not require or request additional treatment. CONCLUSIONS: This preliminary study provides evidence that successful medial branch RFN for lumbar zygapophysial-mediated pain does cause initial denervation but no discernable segmental atrophy of the multifidus at long-term follow-up. Previous denervation and diffuse atrophy in these subjects was not associated with pain.

A narrative review of lumbar medial branch neurotomy for the treatment of back pain.

BACKGROUND: Confusion persists concerning the nature and efficacy of procedures variously known as facet denervation, lumbar medial branch radiofrequency neurotomy, and radiofrequency neurotomy or denervation for the treatment of back pain. Systematic reviews have not recognized the importance of patient selection and correct surgical technique when appraising the literature. As a result, negative conclusions about procedures have been drawn because lack of efficacy of one procedure has been misattributed to other, cognate, but different procedures. OBJECTIVES: To demonstrate how the rationale and efficacy of lumbar medial branch neurotomy depends critically on correct selection of patients and use of surgically correct technique. METHODS: A narrative review and description of the available evidence, drawn from the personal libraries of the authors and from the bibliographies of systematic reviews. RESULTS: Three studies, commonly accepted as evidence of lack of effectiveness, were not valid tests of lumbar medial branch neurotomy because of errors in selection of patients or errors in surgical technique, or both. Two descriptive studies and three controlled studies that used valid or acceptable techniques consistently showed that lumbar medial branch neurotomy had positive effects on pain and disability. All valid, randomized controlled trials showed medial branch neurotomy to be more effective than sham treatment. DISCUSSION: Negative results have been reported only in studies that selected inappropriate patients or used surgically inaccurate techniques. All valid studies showed positive outcomes that cannot be attributed to placebo. Inappropriate conclusions have been drawn by systematic reviews that misrepresent invalid studies as providing evidence against the efficacy of lumbar medial branch neurotomy.

The ability of multi-site, multi-depth sacral lateral branch blocks to anesthetize the sacroiliac joint complex.

OBJECTIVE: To determine the physiologic effectiveness of multi-site, multi-depth sacral lateral branch injections. DESIGN: Double-blind, randomized, placebo-controlled study. SETTING: Outpatient pain management center. PATIENTS: Twenty asymptomatic volunteers. BACKGROUND: The dorsal innervation to the sacroiliac joint (SIJ) is from the L5 dorsal ramus and the S1-3 lateral branches. Multi-site, multi-depth lateral branch blocks were developed to compensate for the complex regional anatomy that limited the effectiveness of single-site, single-depth lateral branch injections. INTERVENTIONS: Bilateral multi-site, multi-depth lateral branch green dye injections and subsequent dissection on two cadavers revealed a 91% accuracy with this technique. Session 1: 20 asymptomatic subjects had a 25-g spinal needle probe their interosseous (IO) and dorsal sacroiliac (DSI) ligaments. The inferior dorsal SIJ was entered and capsular distension with contrast medium was performed. Discomfort had to occur with each provocation maneuver and a contained arthrogram was necessary to continue in the study. Session 2: 1 week later; computer randomized, double-blind multi-site, multi-depth lateral branch blocks injections were performed. Ten subjects received active (bupivicaine 0.75%) and 10 subjects received sham (normal saline) multi-site, multi-depth lateral branch injections. Thirty minutes later, provocation testing was repeated with identical methodology used in session 1. OUTCOME MEASURES: Presence or absence of pain for ligamentous probing and SIJ capsular distension. RESULTS: Seventy percent of the active group had an insensate IO and DSI ligaments, and inferior dorsal SIJ vs 0-10% of the sham group. Twenty percent of the active vs 10% of the sham group did not feel repeat capsular distension. Six of seven subjects (86%) retained the ability to feel repeat capsular distension despite an insensate dorsal SIJ complex. CONCLUSION: Multi-site, multi-depth lateral branch blocks are physiologically effective at a rate of 70%. Multi-site, multi-depth lateral branch blocks do not effectively block the intra-articular portion of the SIJ. There is physiological evidence that the intra-articular portion of the SIJ is innervated from both ventral and dorsal sources. Comparative multi-site, multi-depth lateral branch blocks should be considered a potentially valuable tool to diagnose extra-articular SIJ pain and determine if lateral branch radiofrequency neurotomy may assist one with SIJ pain.

Is immediate pain relief after a spinal injection procedure enhanced by intravenous sedation?

OBJECTIVE: To determine the effect of intravenous sedation on postprocedural pain relief for patients undergoing a spinal injection procedure in which there is no expectation of immediate relief. DESIGN: A prospective audit to compare Visual Analog Scale (VAS) responses before and after interlaminar epidural corticosteroid injections without epidural anesthetic in those who did and did not receive intravenous sedation. SETTING: This audit was undertaken in 2 interventional spine practices. PATIENTS: A total of 102 patients were allotted to receive or not receive intravenous sedation depending on preference. INTERVENTIONS: Interlaminar epidural injections of corticosteroid without epidural anesthetic. MAIN OUTCOME MEASUREMENTS: Outcomes were measured by mean (VAS) scores after the procedure and mean VAS differences before and after the procedure. RESULTS: There were no significant differences between mean VAS scores or mean differences in VAS scores between those who did or did not receive intravenous sedation. A relatively high percentage of patients in both groups obtained greater than 50% immediate pain relief. CONCLUSION: Intravenous mild or moderate conscious sedation did not have an effect on postprocedural VAS pain scores in those receiving a therapeutic spinal injection procedure. Immediate pain relief was most likely the result of nonspecific effects.

Cervical intradiscal radiofrequency lesioning: a feasiblity study.

OBJECTIVE: The objective of this benchtop study was to establish if single site, long duration intradiscal radiofrequency (RF) at two different positions could generate adequate heating throughout the intervertebral disc to potentially ablate intradiscal nociceptors. DESIGN: The disarticulated cervical spines from four fresh frozen cadavers were studied. Temperature recording was completed from two different positions of the RF needle. The needle was either placed in the middle of the disc in four discs, or it was inserted in the posterior quarter of the disc, in eight discs. Thermocouple measurements were made every 2 minutes from three positions: middle of the disc, posterolateral aspect of the disc, and in the anterior third of the disc. SETTING: Fluoroscopy suite. MATERIALS: Disarticulated cervical spine specimens. INTERVENTIONS: Intradiscal RF lesioning in the middle and posterior portion of the cervical disc at 85 degrees C for 10 minutes. OUTCOME MEASURES: Local temperature within the disc. RESULTS: Lesioning in either the middle or posterior portion of the disc failed to provide sufficient temperature increases throughout the cervical disc to achieve adequate denervation. CONCLUSIONS: As in the lumbar spine, intradiscal cervical RF provides too focal a thermal profile to effectively denervate the disc even in an ex vivo experiment. Thus, single site, long duration cervical intradiscal RF lesioning in vivo cannot be recommended.

The ability of single site, single depth sacral lateral branch blocks to anesthetize the sacroiliac joint complex.

OBJECTIVE: To determine the physiologic effectiveness of single site, single depth sacral lateral branch injections. DESIGN: Randomized, controlled, and double-blinded study. SETTING: Outpatient pain management center. PATIENTS: Fifteen asymptomatic volunteers. INTERVENTIONS: The dorsal sacroiliac ligament was probed and the sacroiliac joint was injected with contrast medium until capsular distension occurred. The presence or absence of pain with each maneuver was noted. Under double-blind conditions, subjects returned 1 week later for L5 dorsal ramus and S1-4 lateral branch injections; 10 subjects received 4% lidocaine (active) injections while five subjects received saline (control) injections. After 30 minutes, subjects had repeat ligamentous probing and capsular distension of the same sacroiliac joint that was previously tested. The presence or absence of pain with each maneuver was noted. In a parallel anatomic study, S1 and S2 lateral branch injections with green dye were performed on two nonembalmed cadavers. Dissection was undertaken to quantify the degree of staining of these target lateral branch nerves. OUTCOME MEASURES: Presence or absence of pain for ligamentous probing and sacroiliac joint capsular distension. RESULTS: Forty percent had no discomfort upon repeat ligamentous probing after active lateral branch injections while 100% retained pain upon repeat ligamentous probing with control lateral branch injections. Forty percent of the active group and 20% of the control group did not feel repeat capsular distension of the sacroiliac joint after the lateral branch injections. In the anatomic study, 11 lateral branch nerves were isolated while staining occurred in only four cases or 36%. CONCLUSIONS: Anatomic limitations exist with single site, single depth sacral lateral branch injections rendering them physiologically ineffective on a consistent basis.

Hip joint pain referral patterns: a descriptive study.

OBJECTIVE: To determine hip joint pain referral patterns. DESIGN: Retrospective analysis. Setting. Multicenter. Patients. Fifty-one consecutive patients meeting clinical criteria of a symptomatic hip joint. Interventions. Fluoroscopically guided intra-articular hip joint injection. Outcome Measures. Anatomic pain map before hip injection and visual analog scale both before and after hip injection. RESULTS: The hip joint was shown to cause pain in traditionally accepted referral areas to the groin and thigh in 55% and 57% of patients, respectfully. However, pain referral was also seen in the buttock and lower extremity distal to the knee in 71% and 22%, respectively. Foot and knee pain were seen in only 6% and 2% of patients, respectively, while lower lumbar spine referral did not occur. Fourteen pain referral patterns were observed. CONCLUSIONS: Buttock pain is the most common pain referral area from a symptomatic hip joint. Traditionally accepted groin and thigh referral areas were less common. Hip joint pain can occasionally refer distally to the foot. Lower lumbar spine referral did not occur.

Comparative effectiveness of cervical transforaminal injections with particulate and nonparticulate corticosteroid preparations for cervical radicular pain.

OBJECTIVES: Cervical transforaminal epidural injections of corticosteroids have been used in the treatment of radicular pain. Particulate agents have been associated with rare adverse neurological outcomes. It is unknown whether nonparticulate preparations are any less effective than particulate preparations. Therefore, a study was designed to determine whether there is a basis for promoting a theoretically safer nonparticulate corticosteroid preparation. DESIGN: Volunteer patients were randomized to receive a single cervical transforaminal epidural injection with one of two corticosteroid preparations. SETTING: This study was undertaken in a private practice setting. PATIENTS: Those with single-level, unilateral radicular pain with advanced imaging demonstrating single-level neural compression. INTERVENTIONS: Patients received a single cervical transforaminal epidural injection with either dexamethasone or triamcinolone. OUTCOME MEASURES: Ratings were obtained by an independent unbiased assessor at 4 weeks via a telephone interview. A visual analog pain scale was used preprocedurally and a verbal integer scale was used at 4 weeks to assess the severity of the patient's radicular pain. As a secondary outcome measure, a patient-specified functional outcome measure was obtained. RESULTS: Both groups exhibited statistically and clinically significant improvements in pain at 4 weeks. Although the triamcinolone group exhibited a somewhat greater improvement, the difference between groups was not significantly different. CONCLUSION: The study found that the effectiveness of dexamethasone was slightly less than that of triamcinolone, but the difference was neither statistically nor clinically significant. A theoretically safer nonparticulant agent appears to be a valid alternative to particulate agents that have been used to date, and which have been associated with hazard.

Sacroiliac joint pain.

The sacroiliac joint is a source of pain in the lower back and buttocks in approximately 15% of the population. Diagnosing sacroiliac joint-mediated pain is difficult because the presenting complaints are similar to those of other causes of back pain. Patients with sacroiliac joint-mediated pain rarely report pain above L5; most localize their pain to the area around the posterior superior iliac spine. Radiographic and laboratory tests primarily help exclude other sources of low back pain. Magnetic resonance imaging, computed tomography, and bone scans of the sacroiliac joint cannot reliably determine whether the joint is the source of the pain. Controlled analgesic injections of the sacroiliac joint are the most important tool in the diagnosis. Treatment modalities include medications, physical therapy, bracing, manual therapy, injections, radiofrequency denervation, and arthrodesis; however, no published prospective data compare the efficacy of these modalities.

A randomized, placebo-controlled trial of intradiscal electrothermal therapy for the treatment of discogenic low back pain.

BACKGROUND: Intradiscal electrothermal therapy (IDET) is a treatment for discogenic low back pain the efficacy of which has not been rigorously tested. PURPOSE: To compare the efficacy of IDET with that of a placebo treatment. STUDY DESIGN/SETTING: Randomized, placebo-controlled, prospective trial. PATIENT SAMPLE: Patients were recruited by referral and the media. No inducements were provided to any patient in order to have them participate. Of 1,360 individuals who were prepared to submit to randomization, 260 were found potentially eligible after clinical examination and 64 became eligible after discography. All had discogenic low back pain lasting longer than 6 months, with no comorbidity. Thirty-seven were allocated to IDET and 27 to sham treatment. Both groups were satisfactorily matched for demographic and clinical features. METHODS: IDET was performed using a standard protocol, in which the posterior annulus of the painful disc was heated to 90 C. Sham therapy consisted of introducing a needle onto the disc and exposing the patient to the same visual and auditory environment as for a real procedure. Thirty-two (85%) of the patients randomized to the IDET group and 24 (89%) of those assigned to the sham group complied fully with the protocol of the study, and complete follow-up data are available for all of these patients. OUTCOME MEASURES: The principal outcome measures were pain and disability, assessed using a visual analog scale for pain, the Short Form (SF)-36, and the Oswestry disability scale. RESULTS: Patients in both groups exhibited improvements, but mean improvements in pain, disability and depression were significantly greater in the group treated with IDET. More patients deteriorated when subjected to sham treatment, whereas a greater proportion showed improvements in pain when treated with IDET. The number needed to treat, to achieve 75% relief of pain, was five. Whereas approximately 40% of the patients achieved greater than 50% relief of their pain, approximately 50% of the patients experienced no appreciable benefit. CONCLUSIONS: Nonspecific factors associated with the procedure account for a proportion of the apparent efficacy of IDET, but its efficacy cannot be attributed wholly to a placebo effect. The results of this trial cannot be generalized to patients who do not fit the strict inclusion criteria of this study, but IDET appears to provide worthwhile relief in a small proportion of strictly defined patients undergoing this treatment for intractable low back pain.