Evidence
There are a number of clinical studies of IDET, but as yet only a single randomised, double-blind placebo-controlled trial, and this only encompasses a relatively small and highly selected population [18]. The study revealed a statistically significant physical and mental improvement in the intervention group of 32 patients at the six months follow-up relative to the placebo group of 23 patients who underwent the same procedure except for the electrocoagulation step.

The current combined documentation pertaining to IDET thus suffers from a lack of randomisation and the use of biased control groups [7]. Furthermore, no articles have been published with follow-ups exceeding two years and much of the documentation can be directly related to the inventors of the technology or to the manufacturer of SpineCATH® [19–22].

There is no convincing documentation as to the treatment’s presumed mechanism of action, i.e. coagulation of the collagen and destruction of the nerve endings [5;23]. Animal and cadaveric experiments suggest that this hypothesis is not valid, however, because the number of nerve fibres found after six weeks is the same both with and without IDET treatment and, with the exception of a very restricted area around the catheter, the temperature measured is not sufficiently high to cause coagulation of the collagen tissue [12;13]. More studies are needed concerning the mechanism of action [24].

Several studies have examined data on patients who have undergone IDET treatment, both clinical outcome studies and reviews [4;7;16;25]. There is no clear agreement about the real effect of IDET treatment, however.

The treatment seems to be relatively safe since no serious side effects have been reported from the clinical trials [5], and only a few case stories have been published reporting severe complications such as osteonecrosis [26] and compression of the distal part of the spinal nerves (cauda equina syndrome) [27;28].

If the treatment effect recorded in these studies is viewed in an overall perspective, the results indicate that the patients experience improvement following IDET in the form of pain alleviation and a greater tolerance for standing and sitting activities. There is uncertainty about the long-term effect of the treatment, though, as some studies indicate a continued effect at follow-up two years after the intervention [19;25], while others indicate a declining effect after two years and deterioration in up to 20% of the patients [29]. Thus no certain long-term results are available, just as the long-term effect of thermal treatment of discs is unknown.

Ongoing trials
A large number of clinical trials are currently underway in the USA. So far these have only been presented in the form of conference abstracts [14]. A common feature of several of these studies, however, is that they lack randomised control groups.

Costs
The cost of the equipment needed to perform one single IDET procedure is approx. DKK 6,000 (excluding VAT). Moreover, a special generator is needed that costs approx. DKK 90,000 [30]. In addition there is the cost of the preceding discography. The intervention has to be done under fluoroscopic control. The IDET procedure can be carried out on an out-patient basis.

Implementation
This treatment represents a new possibility for a patient group with severe symptoms for which no real alternative treatment is usually available at present. Hence, a great demand for this new treatment can be expected. It is important to define the indications for which it will actually be possible to achieve results with this treatment, however. The majority of these patients will not be candidates for other surgery, but compared with conventional back surgery, treatment with IDET is considerably less invasive and can be performed on an out-patient basis under local anaesthesia [7].

In the literature it is recommended that the procedure be preceded by discography, which is not currently a standard procedure in Denmark, but the question of the value of discography as a diagnostic tool in the identification of discogenic pain is controversial, however.

The distributor states that the equipment needed for IDET will be sold exclusively to doctors/hospitals that have undergone introductory and proficiency courses in the use of IDET [30], but it presumably only requires a one-day course to learn to perform the IDET procedure [31]. In view of the sparse literature on controlled clinical trials of IDET and the somewhat uncertain indications for offering the procedure, any introduction of IDET in Denmark should be on a trial basis via a national, randomised, controlled clinical trial.