Second-look discography after Intradiscal Electrothermal Therapy (IDET): an analysis of 32 patients treated at 61 levels

Abstract

Joel S. Saal, MD, Jeffrey A. Saal, MD, Menlo Park, CA, USAIntroduction: Intradiscal Electrothermal Therapy (IDET) has been described as a treatment for discogenic low back pain. Questions have been raised regarding IDET's mechanism of action. The first published reports suggested collagen modification and/or denervation as potential mechanisms. However, no data were presented to substantiate either argument. It is unclear whether IDET is capable of “sealing” annular fissures or has any impact on annular integrity. Before IDET, patients are evaluated with discography to determine internal disc architecture and pain reproduction. The purpose of this study was to determine if discogenic pain perception or disc internal architecture changed after IDET as determined by second look, that is, posttreatment repeat discography.Material and methods: Thirty-two patients who underwent IDET at one or multiple lumbar intervertebral levels underwent repeat discography. Repeat testing was performed to evaluate persistent or new symptoms. All 32 patients had undergone discography before IDET. Provoked pain intensity, pain reproduction concordancy and the presence of annular fissures were recorded. Pain was scored on sliding scale: painless, slight pain, moderate pain, moderately severe pain and severe pain. Permanent hard copy images in the anteroposterior and lateral planes were obtained. Post-IDET discograms were performed at a minimum of 6 months after IDET. The same operator performed pre- and posttreatment discograms using an identical technique. Pre- and posttreatment discograms were compared for provoked pain intensity, concordancy of the pain response and the presence of annular fissures. The data were tabulated and statistically analyzed.Results: Thirty-two patients with a total of 61 IDET-treated disc levels were evaluated. The time interval between pre- and post-IDET second-look discography was a minimum of 6 months, with a range of 6 to 16 months.Before IDET, 61 disc levels provoked moderately severe to severe concordant pain. After IDET, 29 IDET-treated disc levels (47%) provoked these same pain responses, and 32 of 61 (53%) were painless. (10%) Six of 61 (10%) new (untreated) disc levels were reported as painful. Six of 32 (19%) patients were asymptomatic for 1 year or more before repeat discography. Four of 6 (67%) of these patients reported symptoms at the same level on repeat discography, and 2 of 6 (33%) reported pain at previously untreated levels. Ten of 32 patients (31%) had painless repeat discograms. Eight of 32 (25%) of these patients remained equally symptomatic at all the IDET-treated levels on the repeat discogram.Seven of 61 (11.5%) discs failed to demonstrate annular fissures that were noted on pretreatment discography. These were all discs with contained radial fissures.Discussion: Second-look discography permits a unique evaluation of IDET-treated discs that can not be attained by any other method. In this study, posttreatment repeat discography performed on a group of IDET-treated patients (32) who were unimproved or only partially improved revealed that discogenic pain perception improved after IDET in 32 of 61 treated discs (53%). Ten of 32 patients (31%) had painless repeat discograms. These patients were then treated for their nondiscogenic source of pain and resolved their pain problem. Only 8 of 32 (25%) of these patients remained equally symptomatic at all the IDET-treated levels on the repeat discogram. Six of these patients underwent a second IDET, and two patients underwent interbody fusion. Persisting pain at one disc level in a previously treated multilevel case typically accounted for the partial improvers. Only cases of simple radial fissures failed to be identified on the posttreatment discograms.Conclusion: Second-look discography reveals that even in a group of partially improved patients, IDET-treated discs display a significant reduction in pain perception. Annular morphology was objectively improved in discs with pretreatment radial fissures. The discographic pattern was not changed in cases of more severe disruption, even when the disc was reported as painless after treatment. Further study to evaluate the neurogenic mechanisms responsible for this phenomenon is required. In addition, biomechanical analysis of the annulus to determine if the local stress–strain relationships were impacted by treatment would also be valuable.