Two placebo controlled IDET studies have been published, Pauza et al (Spine 2004) and Freeman et al (Spine 2005).

• Pauza et al, 2004
• Freeman et al, 2005

Pauza reported a reduction in back pain in both the IDET patients, as well as the placebo controlled patients. The study showed a statistically larger back pain reduction in the IDET arm, concluding IDET a “worthwhile intervention for some highly select patients”.

The Freeman study however reported no improvement in the IDET treatment arm and in the placebo arm of the study. To have no placebo effect is inconsistent with published studies in a variety of clinical fields where a 10-30% effect would be expected.

Several points of debate have been raised about the Freeman study:

• 85% of patients had abnormal reflexes, for which the most likely cause is radiculopathy. IDET may have been used to treat the wrong diagnosis in this study, i.e. radiculopathy, not discogenic back pain.
• Discography inclusion was stated to be “symptomatic” not “concordant”. Manometry was not used, nor was there a severity of concordancy requirement. Simply by pushing harder and faster on the syringe, not using a severity or concordancy requirement, and not requiring a negative control disc, it is quite easy to call this diagnostic test positive. When a study treats a large percentage of patients who have been diagnosed using a false positive diagnostic test, questionable outcomes can be expected.
• Patients were administered a super dose (100 mg cefazolin) of antibiotics intradiscally. Published studies have reported that high doses of antibiotics, including cefazolin, have deleterious effects on disc cell survival, proliferation and metabolic rates. This would suggest that healing of the disc post-IDET might be hampered substantially, lessening or eliminating the treatment effect. High doses of antibiotics may also be directly toxic to developed nociceptors along the annular tears, providing a chemical irritation translating into persistent pain

Pauza et al, 2004 Pauza KJ, Howell S, Dreyfuss P, Peloza JH, Dawson K, Bogduk N. A randomized, placebo-controlled trial of intradiscal electrothermal therapy for the treatment of discogenic low back pain. Spine J. 2004;4:27-35.

Pauza et al were the first to publish a placebo-controlled study of any percutaneous or surgical procedure for chronic discogenic low back pain. The results were encouraging:

• The screening process was rigorous in spite of the difficulty of recruiting patients with chronic low back pain for a placebo-controlled study of a procedure that is readily available elsewhere. Fewer patients (N=64) were recruited than the 67 originally planned. This reduced the power of the study to detect a difference from 80% to 60%, but statistical significance was still achieved.
• The primary objective was to compare improvement in pain and physical function at 6 months between groups. Outcomes were assessed with a 10-point visual analog scale (VAS) for pain, the Short Form (SF)-36, and the Oswestry disability scale.
• Improvements in pain, disability, and depression were significantly greater in the IDET* procedure group. IDET procedure patients had significantly greater reductions in VAS pain score (mean: 2.4 vs 1.1, P=0.045) and Oswestry disability scale (mean:11 vs 4, P=0.050).
• The proportions of patients who achieved >2 points of improvement in pain and who achieved >75% relief of pain were greater in the IDET procedure group. The proportion of patients whose condition deteriorated was greater in the placebo group.
• No patient had an adverse event attributable to treatment.

Effects of placebo in Pauza 2004

The placebo effect in this study was substantial: 38% of placebo patients reported pain improvement. Other than discogenic pain and associated slight-to-moderate functional disability, patients in both groups were reasonably healthy and had relatively high baseline scores on the SF-36, limiting the possibilities for significant improvement. For that reason, post hoc analyses were performed stratifying patients according to baseline measures.

• Post hoc stratified analyses demonstrated that the IDET procedure was significantly more effective than placebo in patients with poor physical function (mean baseline SF-36 score <55/100, P=0.002) and higher levels of disability (mean Oswestry baseline ≥ 40/100, P=0.017).

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Freeman et al, 2005 Freeman BJC, Fraser RD, Cain CMJ, Hall DJ, Chapple DCL. A randomized, double-blind, controlled trial: intradiscal electrothermal therapy versus placebo for the treatment of chronic discogenic low back pain. Spine. 2005;30:2369-2377.

Freeman et al conducted a double-blind, placebo-controlled assessment of the safety and effectiveness of the IDET* procedure. The study was designed with a sample size of 75 patients—allocated 2:1, IDET procedure to placebo—for 80% power to detect a statistically significant difference.

• Despite its 75-patient sample goal, only 57 patients were enrolled (IDET procedure 38, placebo 19) before the study was prematurely halted on the recommendation of the institutional ethics committee. This suggests the study as conducted was not adequately powered to detect a significant difference between treatments.
• Patients were assessed at baseline, at 6 weeks, and at 6 months. Outcomes were measured using the Low Back Pain Outcome Score, the Short Form (SF)-36, the Oswestry disability scale, the Zung depression index, the Modified Somatic Perception Questionnaire, sitting tolerance, work tolerance, medication use, and the presence of neurological deficit.
• No statistically significant or clinically important differences between the two treatment groups were detected at 6 months.
• No serious adverse events were reported. Transient radiculopathy was reported in 5 patients (4 IDET procedure, 1 placebo).

Patient selection factors in Freeman 2005

• The Freeman study accepted patients with loss of up to 50% of disc height. There was no analysis stratified by disc space height to assess the impact of preservation of disc height on success of treatment. This has previously been shown to be a useful factor for predicting success of the IDET procedure.
• The study also predominantly included patients receiving workers’ compensation (IDET procedure 55.3%, placebo 57.9%)—11% of patients in the IDET procedure group were receiving disability payment. The absence of secondary financial gain issues, such as money from pending litigation or workers’ compensation, has been identified as predictive of a successful outcome for IDET treatment.

This underpowered trial notwithstanding, the safety and efficacy of the IDET procedure have been assessed in more than 400 patients in 10 non-randomized prospective studies.