IDET Explanation: Basic Information from a Pain Management Specialist

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Intervertebral DiscIf you have discogenic low back pain (that's pain specifically related to your intervertebral discs), IDET—or intradiscal electrothermic (or electrothermal) therapy—may be a good treatment option for you. Because it's relatively new, there are lots of questions about it, including the most basic: how does it work?

Dr. Lawrence Kamhi, an interventional pain management specialist, answers some of the most important questions you may have about IDET.

To learn more about why some doctors consider IDET an experimental procedure, you can read IDET Controversy: Answers from a Pain Management Specialist.

Q: What conditions is IDET used for? Who does it help most? Who will it not help?
A: IDET is used in the patient with documented discogenic low back pain where the disc itself is known to be the patient's principle pain generator.

The intervertebral disc—whether healthy or diseased—contains small nerves sensitive to pain. When the intervertebral disc is diseased, these nerves amplify in number, and they become very sensitized to pain. The synapses, which are tiny gaps between nerves where nerve impulses are transmitted, also increase in strength and number with discogenic low back pain. Essentially, the synapses transmit more message of more pain, and this is one mechanism felt to be responsible for chronic low back pain.

Diseased intervertebral discs are abnormal in three main ways:

  • reduced disc height
  • loss of normal water content
  • rents and tears in the outer, tougher annulus fibrosus through which portions of the inner, softer nucleus pulposus may herniate

IDET is used for patients with diagnosed discogenic low back pain. Not all spine pain is discogenic; IDET would be inappropriate, for example, for a patient whose low back pain is due to a serious spondylolisthesis, or due to severe arthritic disease of the lumbosacral facet joints.

Q: How does IDET work?
A: During IDET, the doctor inserts a small needle through the skin, just to the side of the spine, at the level of the diseased disc. The doctor advances the needle until the tip is within the center of the diseased disc (the nucleus pulposus).

Then, a special catheter is passed through the needle and advanced through the disc "between" the nucleus pulposus and the outer layer, the annulus fibrosis. Specialized opaque markers enable the doctor to place the IDET catheter in precisely the desired location. Then, wires inside the IDET catheter heat the disc to a point that denatures (or "melts") the disc tissue immediately adjacent to the catheter tip. This accomplishes two therapeutic aims:

  • It deactivates the nerve tissue within the disc.
  • It seals the rents and tears in the outer annulus fibrosus adjacent to the heating portion of the IDET catheter.

Q: What results do you get with IDET?
A: One hoped-for result is a denervated diseased intervertebral disc, where the nerve fibers have been essentially killed—and thus are no longer painful. Another possible result is that a disc that has been repaired mechanically, much like a "patched tire," may not be as likely to re-herniate. No doubt, there will be further improvements in this technology in the future that may allow us to do even a bit more in the treatment of discogenic disc pain.

Q: What are the benefits of IDET (over more traditional treatments such as surgery)?
A: There are two main advantages to IDET. First, it is considered minimally invasive, so it's not a "big" surgery. The second advantage is that the recuperation period is very short, especially when compared to traditional open spine surgery.

Q: What are the risks involved in IDET?
A: All spine procedures, whether performed "open" (through a large incision) or minimally invasively (through small incisions), are surgical in nature. It doesn't matter if the procedure is performed with a needle and a catheter under x-ray guidance (as in IDET), or if it is involves making an incision with a scalpel and drilling into the bony spine (as in traditional surgery). Although IDET is minimally invasive, it still carries the possibility of introducing infection into the intervertebral disc if there is a breach of proper sterile technique.

Unfortunately, IDET has resulted in at least one reported case of intra-operative injury to the spinal nerves.

There are ways to safeguard against the risks of infection and nerve injury. While it is considered a fairly safe surgical procedure, IDET still requires considerable training and experience on the part of the doctor performing it. Also, the entire operating team must pay the utmost attention to sterile technique so infection isn't introduced into the disc.

For IDET, it's also important for the physician to use special imaging equipment (called C-arm fluoroscopes) because that helps the team guide the catheter.

Finally, and most important of all, the operating doctor must carefully select the patient and make sure that he or she is a good candidate for IDET. As one of my professors in medical school would say to us, time and time again: "There is never any point in doing the wrong operation for the patient very well."

Q: What would you say to a patient considering IDET?
A: I would first ask the patient whether he or she has had one or more visits to a spine specialist. I'd want to know if the spine specialist conducted a detailed history and physical examination to diagnose the patient's problem.

Then, I would ask the patient if his or her doctor performed confirmatory tests. At minimum, I would expect that the doctor had done high-quality plain x-rays and a high-quality MRI scan.

I would also ask the patient whether he or she had undergone a reasonable course of conservative therapy for their spine pain, including appropriate oral medications, physical therapy, and less invasive injection procedures including, but not limited to, epidural steroids.

I would need to find out if the patient had discussed with their doctor why he or she is suggesting IDET. They should also have discussed whether a different surgical spine procedure might produce an equivalent—or perhaps even better—result for them. Before trying any treatment option, patients need to be fully informed about what is going to happen and why it's being suggested. Then they'll be better able to help make the decision about how best to treat their pain.

Updated on: 03/22/16
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Interventional Chronic Pain Management
Leonardo Kapural, MD, PhD

Discogenic pain is a persistent, low back and occasionally groin and leg pain that is typically worse with sitting or straining (axial loading). It also typically improves with lying down. Non-specific features of discogenic pain make clinical diagnosis of such pain difficult. Many practitioners use provocative discography and magnetic resonance imaging (MRI) studies to substantiate diagnosis of discogenic pain.

If you have a persistent, discogenic low back pain that lasts for more than six months and if you haven't improved with a comprehensive conservative program which includes intensive exercises, physical therapy, and at least one fluoroscopically guided epidural corticosteroid injection, you may be a candidate for disc heating.

Heating of the disc using various energy sources may decrease or eliminate discogenic pain. Until now, those techniques failed to demonstrate obvious tissue changes in the disc that could explain their therapeutic action. Still, suspected mechanisms are denervation (elimination of the pain receptors) of the tissue and alteration of the collagen fibers in the disc. Major advantages of such minimally invasive therapies are relative simplicity, low cost, and fewer side effects when compared to surgical procedures such as lumbar fusion or disc replacement. Disc heating modalities are also generally more acceptable by the patients. Minimally invasive approaches using heat to treat discogenic pain include IDET (Smith and Nephews, London, England), discTRODE? (Radionics Inc., Burlington, MA), and intradiscal biacuplasty (Baylis Medical Inc., Montreal, Canada).

When those methods of heating a specific part of the disc were compared, there were modest improvements in pain scores and functional capacity of the patients with discogenic pain after treatment with novel annular probe termed discTRODE? (Kapural et al., 2006). Compared to IDET, it is less effective in both improvement in functional capacity and the pain scores when strict patient selection criteria are used.

The latest minimally invasive method to heat the disc using bipolar radiofrequency electrodes is named intradiscal biacuplasty. It may be the most promising of all minimally invasive disc heating methods based on the improvement in pain scores and functional capacity (Kapural et al., 2008). Radiofrequency current is concentrated between the electrodes positioned on the ends of two straight probes. The electrodes are internally cooled, allowing deep, even heating over the larger area of the disc. Currently, the Cleveland Clinic (Cleveland, OH) is conducting a prospective sham study [where some patients think they are getting the full treatment but are actually getting a placebo] on intradiscal biacuplasty.

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