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| IDET History | The Study | The Results | Complications | Discussion | The Blunder |

Davis TT, et al. “The IDET procedure for Chronic Discogenic Low Back Pain” Spine 2004; 29(7):752-756

Over recent years, the use of IDET for the treatment of chronic discogenic back pain has become quite controversial. Some investigations have demonstrated its effectiveness (efficacy) while others have not. This investigation by Davis et al. was one of the studies that found IDET not to be particularly useful for the treatment of discogenic back pain, which supports the growing number of opinions that contest the promotion of IDET for the treatment of chronic discogenic back pain (23-27).

Although this study didn’t use the always preferred ‘randomized double-blind placebo-controlled trial’ in its design, it did have one unique feature that I liked very much: it used a totally ‘independent’ group of people to gather the follow-up results.   By using these “trained independent interviewers”, we can be relatively certain that ‘experimental bias’ was left out of the results.

The bottom line of the study was this: at one year status-post IDET, only 1 patient out of 44 reported the procedure to be a complete success! About 60% of these patients reported that their pain was either the same or worse. Over a two-year period, 23% were lost to fusion surgery, one developed severe discitis with bone destruction, and one patient developed instability. Not a very pretty picture!


In the 1970's, Crock began the theory that both back and leg pain (3) could occur because of 'disruptions' or 'tears' within the substance of the intervertebral disc. This syndrome, termed Internal Disc Disruption (aka: IDD or discogenic pain) (4), has been experimentally calculated to be responsible for at least 40% of all chronic back and leg pain suffering (5). Personally, because of some study-design problems, I believe the rate of IDD to be even higher; see here for details: (Schwarzer Reviewed :)

In 1997, the Saal brothers introduced and patented a completely new form of treatment for IDD (6); they called this procedure "Intradiscal Electrothermal Treatment" or IDET for short. In the inventors own words, "IDET was developed as a potential alternative treatment for selected patients with chronic discogenic low back pain who had failed to improve with activity modification, aggressive nonoperative care, and the passage of time."

The procedure involves the threading a thin wire (catheter by SpineCATH) into the posterior inner anulus of the disc. This all important catheter-placement is accomplished under two-plane fluoroscope. Once in place the final 5 cm of the wire (the tip) is heated to 90 degrees C over a 13 minute period and left at that temperature for another 4 minutes. Finally, an antibiotic (cefazolin) is administered intradiscally as the catheter was removed from the disc.

It was hoped that this 'cooking' of the posterior disc would have the following pain-killing effects: 1) contract the collagen fibers in the anular-nuclear region which in turn would cause a shrinkage of the nucleus and seal-off any painful anular tears, and 2) destroy (ablate) the pain carrying nerve fibers in the outer anulus fibrosus and around the anular tear.

Although the IDET initially looked to be very promising (7 ,10-12), recent investigations and 'clinical rumors' have cast doubt on the efficacy and safety of its use of for the treatment of IDD. Furthermore, some recent research has failed to confirm Saals' 'shrinkage-theory of healing' which leaves us unsure of just how IDET produces its curing effect (8 ,9).  

We are eagerly awaiting the long-term results of the first randomized double-blind placebo-controlled investigation on IDET (13 ,14).   Hopefully this investigation will ‘settle the score’ when it comes to the efficacy of IDET for the treatment of chronic discogenic back pain.


Sixty consecutive patients, all of whom had endured an IDET procedure for their chronic low back pain, were contacted by telephone about 1 year after their procedure. They were asked a short series of “core” standardized questions (1) regarding their current pain level, work status, functional limitations, pain medication usage, and overall satisfaction with the IDET procedure.

This cleverly designed study, unlike all previous studies on the IDET, used a “trained, independent interviewer” to contact the patients, so there was no ‘experimenter bias’ involved with the result. (Sometimes patients are reluctant to tell their doctors the truth about the failure of their treatment, and sometimes the doctors can be ‘over zealous’ when interpreting patient response.) A more extensive questionnaire was mailed to the patient for completion. The interviewers had no idea what procedure these patients had been through nor had access to their medical records.


In order for a patient to be accepted into this trial, the patient must have the following:


An internally disrupted disc with an anular fissure (It wasn’t specified how this was identified – probably during discography)


A contained disc herniation (or a disc bulge or even normal disc contour, all of which are the typical presentation of IDD.)


Concordant discogenic pain as demonstrated on provocation discography with the presents of one non-painful control disc


The disc height must not be decreased by more than 50%.


Suffered chronic back pain (with or without leg pain) for a period greater than 6 months.


Failed aggressive conservative care which included NSAIDS, Physical Therapy, Bracing, and injections (I’m assuming epidural steroid injections).


Patients with Stenosis, disc extrusion (or worse), neural compression, past surgical history, instability, loss of disc height, and overlying psychological issues were excluded for this investigation.


Following the IDET procedure, almost all of the patients (95%) wore a stabilizing lumbar support for at least one month. For the majority of the patients (86%) there were no other forms of treatment rendered post-IDET. The minority did try other forums which mainly included epidural steroid injections.

Finally, at the two year ‘status-post IDET’ mark, another attempt was made to re-contact the group by the independent interviewer.


The biggest down fall of this investigation is the fact that only 44 (73%) of the consecutive IDET patients responded and completed the interview; however, this may be a blessing in disguise, for the “majority” of the patients who refused to answer the interviewers questions, would not do so because of their “pending Workers’ Compensation claims”. So these patients may have made the results of the investigation worse than they already were!

Note: the rest of these results were based upon the one-year outcome assessment and did NOT officially include the 6 patients that were lost to fusion (see the BLUNDER).   Since I strongly believe that they should have been included as failures and probably had increased pain, I’ve included a column to depict what the ‘real’ results would look like:


One year outcome results:

Study Results: % (patients)

Result including the 6 lost to surgery

Patients there were satisfied with the results of the IDET:

37% (14/38)

32% (14/44)

Patients who completely recovered (100%) from their pain - post IDET:
3% (1/38)
2% (1/44)

Patient that would choose to have the IDET again:

53% (20/38)

45% (20/44)

Patient who reported MORE pain after IDET, i.e., the Complication Rate:

29% (11/38)

39% (17/44)

Patient who reported the Same pain or MORE pain after IDET:
58% (22/38)
64% (28/44)

Patients reporting IDET was a complete success and they had NO PAIN:

2.6% (1/38)

2.3% (1/44)

Patients who were lost to surgery:

14% @ 1 year

23% @ 2 years


Of the 38 remaining patients, 20 of them (53%) were satisfied enough with the results of IDET to say that they would have it again and had no regrets. Now, I believe I can safely assume that none of those six failed-IDET patients would chose to have IDET again. That changes our 53% satisfaction rate to only 45%.

Here’s a strange twist: When asked if the patient was “satisfied” with the results of the IDET, only 14 of the 38 patients (37%) said yes. (again, we know those 6 patients lost to fusion were obviously not satisfied; that makes only 14 out of 44 patients (32%) who answered ‘yes’, they were satisfied with the result. (I’m a little confused why there was such a difference between the “satisfied patients” (32%) and the “patients who said they would do the IDET again if they had a ‘do-over’ (45%).

Here’s another scary figure: 29% of the patients reported MORE pain at one year then they had before the IDET was performed. If you add in the 6 patient that left the study for fusion that gives us a 39% worsening of pain post IDET!

Of the 38 patients, only 1 reported ‘no pain’! That means that only 3% became pain free. Again, we really need to count those 6 failed-IDET patients (for we know they were not out of pain!) in this number as well. One patient out of 44, gives us a 2% success rate for IDET.


Four doctors did all the IDETs in this investigation. All four doctors were not only very experienced at performing the IDET surgery, but they were also 'Teaching Doctors', meaning they were certified to teach IDET to other doctors in the field. So, we can safely conclude that doctor inexperience was not a factor in the development of complications:

At the one year mark (status-post) 6 patients (14%) were lost to decompressive surgery (5 fusions and 1 discectomy). At the 2 year mark, yet another 4 patients were lost to surgery (3 fusions and 1 discectomy).   Therefore, in 10 of the 44 patients (23%) the IDET completely failed to prevent surgery.

Interestingly, this same 23% was also found in a recent investigation. Webster et al. (30) prespectively assessed the outcome of 142 Workers' Compensation patients who underwent IDET for chronic discogenic pain. They confirmed the results of this study, in that 23% of the patients ended up having surgery despite having the IDET. (30)

Besides the fact that 29% of the patients reported a worsening of pain at one year (39% if we add the 6 fusion patient into this number) there was a 4.5% complication rate in this study. On patient developed a nasty looking discitis and was forced into fusion. The other patient somehow developed instability? (I can’t imagine this to be the fault of the IDET but they include this grade I anteriolisthesis as a complication).


“A nonsurgical treatment option that offers clear clinical benefit is still not available for discogenic low back pain…. Approximately one third of the patients were satisfied with their outcome, and nearly all continued to report pain approximately 1 year post-IDET….”

I couldn’t agree more. This study, which used an independent review company to gather patient outcome data as opposed to the research team, clearly demonstrated that IDET failed to improve the majority of chronic discogenic pain patients. More explicitly, only 14 of the 44 patients (32%) stated that they were “satisfied” with the outcome of the IDET procedure and only 1 patient out of 44 (2%) was pain free at one year.

I wonder how a placebo group (sham IDET) would have done against IDET. I would bet that IDET wouldn't’t have done much better… but of course this is pure speculation.

Is the IDET safe?

In this study, there was a 4.5% complication rate, although all of the four doctors who performed these IDETs were ‘super-experienced’, i.e., that were all ‘instructors’. Would the complication rate rise amongst the less experience doctor? Probably. Here’s what the authors had to say regarding IDET safety:

“…an even greater concern is the pathologic effect on the disc and endplate over time. In some IDET cases, clinicians are seeing progression of degeneration at the post-IDET levels with recurrence or worsening of pain. A recent case study reported a complication of endplate osteonecrosis (death of the bone of the end-plate) post-IDET procedure (2). Similarly, 1 patient was found to have endplate erosion post-IDET in this cohort (study). These complications raise serious concerns over the long-term sequelae (consequence) of thermal treatment on the intervertebral disc and stress the importance of further studies and continued follow-up.”


Here’s my beef:   at the first year outcome assessment we learned that six patients were lost to surgery.   You would have thought that these ‘severely’ failed IDET patients would have been included in the outcome results, right?    Wrong! For some reason, the authors decided that these six failures should be removed from the study completely! I kid you not…. Only the 38 remaining patients were used for the determination of IDETs efficacy for chronic discogenic pain.

Other blunders included the following: the non-use of standardized and proven disability assessment tools (Oswestry, and/or Roland-Morris); the non-description of percentage of these patient that were in litigation (workers' compensation or personal injury patients) and the failure to detail the entry criteria more explicitly (already mentioned).


Usually I inject quite a few of my own comments and beliefs at the end of my reviews, but this time I will let the authors own words close my page:

“Although the initial research appeared promising, IDET should be scrutinized more closely using controlled studies. As we collect more long-term follow-up of this patient population, we find that this procedure may be less effective than previously reported.”

In all fairness to the IDET procedure, I have just received the 6-month result from the Pauza & Bogduk investigation. This investigation was the first to use a randomized, placebo-controlled methodology and compared IDET against a placebo. Although I don't report on investigations that have not followed its participants for at least one year, I will say that this OPA award winning study is off to a good start, in that at 6 months IDET is showing evidence of being more effective than a placebo. I'll post this 'decisive' investigation when it hits the one year mark.


1) Long DM, et al. “Persistent back pain and sciatica and sciatica in the United States: patient characteristics.” J Spinal Discord 1996; 9:40-58

2) Djurasovic M, et al. “Vertebral osteonecrosis associated with the use of intradiscal Electrothermal therapy.” Spine 2002 ;27:E325-E328

3) Crock HV. “Observations on management of failed spinal operations.” J bone Joint Surg Br. 1976; 58:193-199

4) Crock HV. “Internal disc disruption. A challenge to disc prolapse fifty years on.” Spine 1986; 11:650-653

5) Schwarzer AC, Aprill CN, Derby R, Bogduk N, et al. “The prevalence and clinical features of Internal Disc Disruption in patients with chronic lower back pain.” Spine 1995; 20(17):1878-1883

6) Saal JA, Saal JS, Ashley J. "Targeted intradiscal thermal therapy: preliminary feasibility results. Presented at the Annual Meeting of the International society for the Study of the Lumbar Spine, Singapore, June 2-6, 1997

7) Saal JA, Saal JS. "Intradiscal Electrothermal Treatment for Chronic Discogenic Low Back Pain: Prospective Outcome Study With a Minimum 2-Year Follow-Up" Spine 2002 ;27:966–974

8) Kleinstueck FS, et al. "Acute Biomechanical and histological effects of intradiscal Electrothermal therapy on human lumbar discs." Spine 2001; 26:2198-2207

9) Shah RV, et al. "Intradiskal electrothermal therapy: a preliminary histologic study." Arch Phys Med Rehabil 2001; 82:1230-1237

10) Derby R, et al. "Intradiscal electrothermal annuloplasty" (IDET): a novel approach for treating chronic discogenic back pain." Neuromodulation 2000; 3:69-75

11) Karasek M, Bogduk N. "Twelve-month follow-up of a controlled trial of intradiscal thermal annuloplasty for back pain due to internal disc disruption." Spine 2000; 25:2601-7.

12) Thompson K. "IDET nationwide registry preliminary results: twelve month follow-up data on 205 patients." 15th Annual Meeting of the North American Spine Society. New Orleans, Louisiana, 2000.

13) Pauza KJ, Bogduk N, et al. "A randomized, double-blinded, placebo controlled trial evaluating the efficacy of IDET for chronic discogenic low back pain: 6-month outcomes." Presented at the Annual Meeting of the International Spinal Injection Society, Austin, TX, September 7, 2002.

14) Pauza KJ, Bogduk N, et al. "A randomized, placebo-controlled, trial of intradiscal electrothermal therapy for the treatment of discogenic low back pain." Spine J. 2004; 4(1):27-35

23) Anonymous. "Intradiscal electrothermal therapy: conflicting results, lively debate." The Back Letter 2001;16:133:140-2

24) Harden N. "Department editor's note. Bulletin of the American Pain Society" 2001;11(4):1

25) Carey TS. "Point of View." Spine 2002;27:973-4

26) Karasek M, Carragee EJ, Schofferman J. "Intradiscal electrothermal therapy." SpineLine 2002;March/April:12-118

27) Heary RF. "Intradiscal electrothermal annuloplasty: The IDET Procedure." J Spinal Dis 2001; 14:353-60.

30) Webster BS, et al. "Outcomes of workers' compensation claimants with low back pain undergoing intradiscal electrothermal therapy." Spine 2004; 29(4):435-41

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