Efficacy of IDET for chronic discogenic low back pain debated

One study found that IDET is effective in a select group of patients; another found no significant clinical benefit.

Issue: Issue 4 2003

---Brian J.C. Freeman reported that intradiscal electrothermal therapy demonstrated no significant clinical benefit compared to placebo.

VANCOUVER, Canada – Two presentations at the International Society for the Study of the Lumbar Spine meeting had different perspectives on the efficacy of intradiscal electrothermal therapy for treating chronic discogenic low back pain.

Kevin Pauza, MD, a pain specialist at Texas Spine & Joint Hospital in Tyler, U.S.A. discussed the findings from his randomized, double blind placebo control trial. This study, which received the North American Spine Society’s Outstanding Paper Award for 2003, found that when compared to placebo, intradiscal electrothermal therapy (IDET) is a good option for a select group of patients with chronic lumbar disc pain.

The other paper, presented by Brian J. C. Freeman, FRCS, consultant spinal surgeon at The Centre for Spinal Studies and Surgery at the University Hospital, Queens Medical Centre in Nottingham, United Kingdom, determined that IDET demonstrated no significant clinical benefit for the treatment of chronic discogenic low back pain when compared to placebo.

Pauza and colleagues used manometric provocative discography and CT as their diagnostic tools. Inclusion criteria for the 64 patients were symptoms for greater than six months, no radicular pain and normal neurological exams. Patients were excluded from the study if they had other comorbidities of the spine or were receiving workers’ compensation or involved in litigation for their injuries. “My study eliminated all confounding variables and had to answer a simple question: Does IDET improve disc pain?” Pauza said.

In Pauza’s study, the randomization was 3:2. The introducer needle remained at the outer annulus for placebo patients, while IDET patients received full treatment. All patients heard radiofrequency generator sound, observed electrode catheter placement on the monitor and received similar conscious sedation. All IDET subjects received exact 100% coverage of the posterior annulus. Post-randomization, all patients had lumbar bracing for six weeks and exercise therapy. During this time subjects and outcome evaluators remained blinded. At the unblinding, placebo subjects were offered IDET. T-tests were utilized to determine statistically greater improvements in the IDET treated group.

Like Pauza, Freeman has also performed a number of IDET procedures (75). He was involved with the design and set-up of the randomized control trial and served as the independent observer. There were 57 patients in the study, all of whom had one- or two-level internal disc disruption with posterior or postero-lateral annular tears as determined by provocative CT/discography. Patients were excluded if there was greater than 50% loss of disc height or previous back surgery.

Patients in Freeman’s study were randomized 2:1. In all cases the IDET catheter was positioned under sedation to cover at least 70% of the annular tear defined by the CT/discogram. An independent technician connected the catheter to the generator and delivered electrothermal energy to the IDET group and nothing to the placebo group. Surgeon, patient and outcome assessor were all blinded to the treatment. Patients followed a standard post-procedural rehabilitation program.

Conflicting outcomes

Outcome measures for Freeman’s study included Low Back Outcome Score (LBOS), Oswestry Disability Index (ODI), SF-36 questionnaire, Zung Depression Index (ZDI), Visual Analogue Scale and Modified Somatic Perceptions Questionnaire (MSPQ), and were recorded at baseline and six months. A successful outcome was determined when no neurological deficit resulted from the procedure, LBOS improved more than seven points, SF-36 subsets (bodily pain and physical functioning) improved more than one standard deviation. Although no neurological deficits occurred as a result of the procedure, that was the only determinant of a successful outcome that was met. No subject in either the IDET or placebo group showed improvement of greater than seven points in LBOS or in the specified domains of the SF-36. Mean ODI was 41.4 at baseline and 39.7 at six months for the IDET group and 40.7 at baseline and 41.5 at six months for the placebo group. There was no significant change in ZDI or MSPQ scores for either group.

“This study seriously brings into question the effectiveness of IDET for the treatment of chronic discogenic low back pain,” Freeman said. “Unless further studies show clinically important improvement in standardized outcome measures (ie, 10 points on the Oswestry Disability Index, seven points on the Low Back Outcome Score, two points on the Visual Analog Score), the technique will fall out of favor very quickly.”

Pauza’s study, which used some of the same outcome measurements (but not the same criteria for success), showed significantly greater improvement in pain at six months in the IDET group compared to placebo.

“Although this study demonstrates benefit in the treatment group, I believe that it’s long-term significance is how it demonstrates the profound impact an appropriate placebo control group has on the interpretation of any study’s results.”

In-depth analysis

In discussing each other’s paper, Pauza and Freeman noted some specific areas of difference. Pauza felt that Freeman’s study could have been improved with stricter inclusion criteria for both groups. “My study eliminated all confounding variables, including issues of secondary gain, such as workers’ compensation and litigation, as well as other comorbidities of the spine,” he said. “This may suggest why his (Freeman) placebo group also showed no benefit, which goes against what one might typically expect.”

On the other hand, Freeman called into question whether Pauza’s study was actually double-blind. “He (Pauza) as the treating physician knew immediately whether the patient had IDET or simply the trochar introduced into a disc,” Freeman said. “Our study involved placement of the IDET catheter with radiographic verification of adequate position in all patients. An independent technician then opened an envelope and either delivered electrothermal energy through a coded junction box or did not. The patients were independently assessed by myself and the statistical analysis was carried out by a further independent team.” However, Pauza’s patients were assessed by an independent investigator not privy to the patient’s randomization.

Freeman and Pauza agree that further analysis of IDET’s effect on chronic discogenic lower back pain is needed. To this end, both are involved in other IDET studies.

For your information:

Pauza K, Howell S, Dreyfuss P, et al. A randomized, double-blind, placebo-controlled trial evaluating intradiscal electrothermal anuloplasty (IDET). Presented at the 30th Annual Meeting of the International Society for the Study of the Lumbar Spine. May 13-17, 2003. Vancouver, Canada.

Freeman BJC, Fraser RD, Cain CMJ, et al. A randomized, double-blind, controlled efficacy study: intradiscal electrothermal anuloplasty (IDET) versus placebo. Presented at the 30th Annual Meeting of the International Society for the Study of the Lumbar Spine. May 13-17, 2003. Vancouver, Canada.