Objectives: To describe a new method of catheter insertion in Intradiscal Electrothermal Therapy (IDET), when and adequate catheter position cannot be achieved with standard technique. Intradiscal Electrothermal Therapy is a new technique developed in 1998 for treatment of chronic low back pain. Adequate catheter position is of vital importance to the outcome of this procedure. If adequate position is not achieved with the standard technique, the recommendation is to reinsert a new cannula into the contralateral side. This requires more local anaesthesia, further discomfort for the patient and additional X-ray exposure. The “Pig Tail” Technique described here, eliminates the need for reinsertion of the cannula and catheter from the contralateral side in those patients in whom optimal positioning is not achieved with the standard technique. This new technique has not been described before.

Methods: In those patients in whom adequate catheter position cannot be achieved with the standard technique, instead of withdrawing the cannula after the initial treatment, we recommend rotating the cannula 180° through its long axis. This will allow the catheter to hit the anterior annulus and deflect backwards towards the cannula. It can then be negotiated across the midline to adequately thermally treat the whole posterior annulus.

Results: We have performed our technique in thirty two consecutive patients in whom initial navigation was difficult. This new method proved to be simple and did not cause patients additional discomfort.

Conclusion: “Pig Tail” Technique is safe and effective in IDET of those patients with difficult navigation. It avoids the need for second needle insertion therefore avoiding the use of more local anaesthsia, further discomfort for the patient and additional X-ray exposure.

Objective: MRI changes to the symptomatic intervertebral disc following Intradiscal Electrothermal Therapy (IDET), in particular those relating to the “High Intensity Zone” (HIZ) in the posterior annulus, were determined in this prospective study.

Material and Methods: MRI images before the IDET procedure were compared to those taken at six months post procedure in 10 patients. The presence and absence of an HIZ, the disc height and hydration, and Modic changes, were determined from the images. Two of the patients also had discography performed post-IDET to supplement the MRI.

Results: In 6 out of the 10 patients, an HIZ was present on the MRI images of the disc before the IDET procedure. In all 6 patients, a HIZ was still present six months after the procedure. In all 10 patients, there were no changes to disc height and hydration signal on T₂ weighted images. Modic changes were not present in any of the patients on pre or post IDET images. Two patients had significant changes to the shape of the posterior annulus compared to the pre-treatment MRI scans. The two patients who had discography after IDET had persistent annular tears.

Conclusion: Our findings question the clinical relevance of the “High Intensity Zone”. They also suggest that the main mechanism of action of IDET, may be other than that of sealing the annular tear.