Chapter 17 Intradiscal Therapies

Intradiscal decompression for chronic intractable discogenic pain can be achieved by means of various methods, such as intradiscal electrothermal therapy (IDET), nucleoplasty, and percutaneous discectomy. Tables 17.1 and 17.2 summarize these three techniques.

Table 17.2 The Evidence for Efficacy Intradiscal Electrothermal Therapy (IDET) and Nucleoplasty in Management of Chronic Discogenic Low Back Pain

Data from Boswell MV, Shah RV, Everett CR, et al. Interventional techniques in the management of chronic spinal pain: Evidence-based practice guidelines. Pain Physician 2005;8:1-47.

Intradiscal electrothermal therapy

In IDET, the collagen fibers of the disc are modified and the nociceptors causing axial back pain are destroyed by thermal energy delivered through the percutaneous threading of a flexible catheter, composed of a thermal resistive coil, into the disc from the side contralateral to the lesion under fluoroscopic guidance (Fig. 17-1).

Figure 17–1 Broad (A) and close up (B) view of the introduction of catheter from the side contralateral to the lesion, electrothermal modification of collagen fibers, and destruction of nociceptors.

Mechanisms of Action

The two mechanisms of action of IDET are thermal modification of collagen fibers and destruction of disc nociceptors. Denervation by thermal energy is used widely for peripheral and central nervous system lesioning.

Thermal modification of collagen fibers acts as follows:

Breaking the heat-sensitive hydrogen bonds of the collagen fibers causes collagen contraction.

With disc temperatures reaching 65° C, collagen may contract as much as 35% from its original size (Fig. 17-2).

The tightening of anular tissue may enhance the structural integrity of the degenerated disc and may repair the anular fissures.

Figure 17–2 Thermal modification of collagen. A, Collagen triple-helix molecule. B, Heat-sensitive bonds break at 60°C. The crystalline extended structure begins to uncoil. As the molecule contracts, its diameter increases.

Indications and Contraindications

Ideal candidates for IDET have the following features:

A single affected disc as determined on magnetic resonance imaging and discography

Preservation of more than 50% of disc height

Contained disc herniation

Predominantly axial pain

Age less than 55 years

Posterior anular deficit

Motivated and with no major psychological issues

No facet disease

Indications

The indications for IDET are as follows:

Patient is a candidate for IDET at one or two levels

Symptoms of degenerative lumbar disc disease of at least 3 months’ duration

Failure of a minimum of 6 weeks of conservative treatment (including pain medication and physical therapy) to improve the symptoms

Marked functional limitation at presentation

Sitting intolerance greater than standing intolerance

Predominantly low back pain with or without referred leg pain at presentation

Negative result of straight-leg raising test and normal neurologic findings

The presence of degenerative disc disease on magnetic resonance imaging with global disc degeneration or posterior or posterolateral anular tear evident

The presence of one- or two-level symptomatic disc degeneration as determined by provocative lumbar discography at L3-L4, L4-L5, L5-S1 and with an adjacent asymptomatic “control” disc

At the target level, the discogram and subsequent computed tomography scanning demonstrate spread of the contrast agent to the outer anulus or beyond the confines of the disc (Fig. 17-3)

Minimum age 18 years

Willingness to comply with follow-up as per the protocol

Figure 17–3 Innervation of an intervertebral disc.

Contraindications

IDET should not be performed in patients with the following conditions:

Evidence of a large contained or sequestered herniation (small contained herniation is allowed)

Loss of more than 50% of disc height at the target level

Severely disrupted disc (sufficient anular tissue is required for safe catheter placement)

Neurogenic claudication due to spinal stenosis

Three or more symptomatic lumbar disc levels

Previous back surgery at any level of the lumbar spine

Spondylolisthesis at a symptomatic disc level

Psychological disorders that may affect treatment outcome (e.g., severe depression, drug addiction)

Medical condition that could interfere with follow-up care or evaluation

Current injury litigation

Pregnancy (risk of exposure to radiation)

Failure to understand informed consent form

Participation in other studies of any kind

Related Anatomy and Pathophysiology

Figure 17-3 illustrates innervations of an intervertebral disc related to IDET.

Procedure

The technique for approaching the disc for IDET is similar to the technique used for discography, as follows:

1. The patient’s written informed consent including possible complications, such as nerve injury, discitis, post-IDET disc herniation, catheter breakage, skin burn, and bladder dysfunction, is obtained.

2. The skin is infiltrated with local anesthetic.

3. A 17-gauge introducer needle is inserted into the disc (Fig. 17-4).

4. Once the position of the needle in the nuclear cavity is established, the thermal catheter is inserted through the needle (Figs. 17-5 and 17-6).

5. The catheter is placed circumferentially around the inner surface of the posterior anulus (Fig. 17-7).

6. The catheter is heated from 37° C to 65° C.

7. The temperature is increased by 1° C every 30 seconds until it is between 80° and 90° C (Fig. 17-8). See also Figures 17-9 and 17-10 for details of the catheter heating parameters.

Figure 17–4 Fluoroscopic AP (A) and lateral (B) views showing the introducer needle in the disc.

Figure 17–5 Insertion of thermal catheter through the needle. The catheter is placed through the needle (A) and is able to pass through the needle tip (B) as shown intraoperatively (C).

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