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

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).

Figure 17–6 SPINECATH Intradiscal Catheter (Smith & Nephew, London). As the catheter is pushed into the inner layers of the anulus fibrosis, the flexible tip is guided so that the path of the tip follows the curve of the anulus, and the heating element can be properly positioned.

Figure 17–7 Anteroposterior (A), lateral (B), and axial (C) fluoroscopic views show the catheter around the inner surface of the posterior anulus.

Figure 17–8 Heating of the electrode of the catheter. The thermal catheter can be positioned at herniated nucleus pulposus (A) and at posterior anulus which is considered as an origin site of discogenic back pain. (B)

Figure 17–9 Relation between the temperature of the electrode of the catheter and percentile of shrinkage of the nucleus pulposus.

Figure 17–10 In vitro temperature mapping sensor location. If the temperature of catheter tip is 90° C, the temperature of the tissue adjacent the catheter is 75° C (A), that of the center of anular wall is 60° C (B), that of the outer anular wall is 42° C (C), and that of the epidural space is 28° C (D).

Postoperative Care and Follow-Up

The physician must realize and point out to the patient that recovery is gradual.

The “healing” process reaches its peak 4 months after the procedure.

A rehabilitation program is recommended after IDET (Table 17.3).

A gradual increase in daily activities is recommended.

Table 17.3 Sample Rehabilitation Program after Intradiscal Electrothermal Therapy

Week	Activity and Exercise
Week 1	1. Walking allowed 2. Wear lumbosacral corset during all activities 3. Sit for only 35-45 minutes at a time 4. No lifting, twisting, bending, or driving 5. No work 6. No physical therapy

Week 2-6

1. Wear lumbosacral corset during all activities

2. Increase sitting time as tolerated

3. Lift no more than 10 pounds

4. Driving allowed

5. No twisting or bending

6. May return to light or sedentary work

7. No physical therapy

Complications

Complications that may occur during or after IDET are as follows:

Nerve root injury

Discitis

Post-IDET disc herniation

Catheter breakage

Skin burn

Bladder dysfunction

Limitations

IDET has some limitations, which are as follows:

It is difficult to navigate and place the catheter at the exact portion of the anulus that contains the tear.

If the temperature of the catheter tip is 90° C, that of the outer anulus is only 42° C. It is difficult to ablate afferent type C sensory innervation at 42° C.

IDET has no significant benefit over placebo [1].

The procedure is limited to patients who complain of axial low back pain before undergoing spinal fusion.

There is a risk of accelerating disc degeneration through thermal injury.

Nucleoplasty

Nucleoplasty is a procedure in which the disc nucleus is decompressed using both energy and heat. We use the Perc-D (DLR in larger discs and DLG longer access) SpineWand (AthroCare Corporation, Stockholm), which is a 1-mm-diameter bipolar instrument designed for this procedure. The tip of the wand has a slight C curve to allow for channeling. The wand is connected to the standard ArthroCare power generator. Nucleoplasty utilizes the company’s patented Coblation (controlled ablation) technology, which has found applications in other areas of medical care [2]. This process generates a unique low-temperature plasma field (see later) for precise, controlled ablation with minimal risk of thermal injury (Fig. 17-11).

Figure 17–11 A, System 200, (ArthroCare Corporation, Stockholm). B, Patient cable. C, Foot control. D, Hand switch control.

Coblation removes tissue by using radiofrequency energy to excite the electrolytes in a conductive medium, such as saline solution, to create precisely focused plasma. The energized particles in the plasma have sufficient energy to break molecular bonds, excising or dissolving soft tissue at relatively low temperatures (typically 40° to 70° C), thereby preserving the integrity of surrounding healthy tissue (Fig. 17-12).

Figure 17–12 Illustrative comparison of coblation plasma surgery with conventional electrosurgery. Collagen fibers are modified and the nociceptors are destroyed by thermal energy in conventional thermal electrosurgery (A), so it can destruct the integrity of healty tissue (B). Coblation removes tissue by using radiofrequency energy to excite the electrolytes to create precisely focused plasma and the energized particles in the plasma break molecular bonds, excising or dissolving soft tissue at relatively low temperatures (typically 40° to 70° C) (C), thereby preserving the integrity of surrounding healthy tissue (D).

Ablation generates approximately 120 volts of energy at the tip of the wand with resultant tip temperatures of 50° to 70° C. A plasma field is generated at the tip, which is a millimicron-thick field of highly energized particles that result in molecular dissociation of the disc material directly in front of the tip. This creates a channel from the posterolateral anulus to the anteromedial anulus (Fig. 17-13A) [3]. On withdrawal of the SpineWand, the coagulation mode is used. This mode uses 60V of energy and a tip temperature of 70° C. On complete withdrawal of the instrument, the thermal effect causes denaturization of the type II collagen with resultant shrinkage of the surrounding collagen and widening of the channel (Fig. 17-13B) [3].

Figure 17–13 A, Ablation. Advancing the SpineWand (ArthroCare Corporation, Stockholm) creates a small, controlled channel in the nucleus. B, Bipolar radiofrequency coagulation during withdrawal of the SpineWand denatures the adjacent collagen and proteoglycan within the nucleus for additional volume and pressure reduction.

Indications and Contraindications

Indications

Nucleoplasty is indicated for patients with radicular/axial pain or axial pain. Radicular/axial pain is diagnosed from the following symptoms and findings:

Leg pain greater than back pain

Magnetic resonance imaging evidence of a contained herniated disc protrusion

Failure of 6 weeks of conservative therapy

Axial back pain is diagnosed as follows:

Magnetic resonance imaging evidence of a contained disc protrusion

Discographic demonstration of concordant pain

Failure of 6 weeks of conservative therapy

Contraindications

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

Severely degenerated disc with more than 33% loss of disc height

Herniation larger than on third of the sagittal diameter of the spinal canal

Disc extrusion or sequestration

Moderate to severe spinal stenosis

Tumor, infection, or fracture

Procedure

Nucleoplasty using the Perc-DLR or Perc-DLG SpineWand is performed as follows (Fig. 17-14A, B) [4]:

1. The patient’s written informed consent including possible complications, such as infection, bleeding, nerve damage, worsening of pain, failure of technique, paralysis, and anaphylactic reaction due to local anesthetics, is obtained.

2. Access to the disc is made through a 17-gauge cannula with obturator stylet using a posterolateral approach.

3. While the patient is monitored for any radiating pain, the SpineWand is advanced into the disc (Fig. 17-15).

4. As the SpineWand is advanced, the coblation plasma mode is activated so that tissue along the path of the device is removed (via molecular dissociation). Tissue is turned into gas, which exits the disc via the introducer cannula.

5. After being stopped at a predetermined depth (prior to reaching the anterior anulus), the SpineWand is slowly withdrawn to the starting position. Sufficient thermal energy is generated to denature nerve fibers adjacent to the channel within the nucleus pulposus.

6. After the first channel is created, the SpineWand is rotated clockwise, and another channel is created. Approximately six channels are made in total, depending on the desired amount of tissue reduction (Fig. 17-16); also see Fig. 17-12) The result of the procedure is tissue removal (via plasma dissociation) sufficient to decompress the disc and denature chemically sensitive nerve fibers growing within the disc nucleus.

Figure 17–14 A, Perc-DLR SpineWand (top) (ArthroCare Corporation, Stockholm) and 17-gauge, 6-inch introducer needle with Crawford tip (bottom). B, Perc-DLG SpineWand (top) (ArthroCare) and 17-gauge, 8-inch introducer needle with Crawford tip (bottom). C, Perc-DC SpineWand (top) (ArthroCare) and 17-gauge, 6-inch introducer needle with Crawford tip (bottom).

Figure 17–15 Confirmation of position of the tip of the SpineWand (ArthroCare Corporation, Stockholm) with anteroposterior (A) and lateral (B) fluoroscopic views.

Figure 17–16 Six channels of the electrode decompress a cone-shaped area of the nucleus.

Nucleoplasty using the Perc-DC SpineWand is performed as follows (see Fig. 17-14C) [4]:

1. The patient’s written informed consent including possible complications, such as infection, bleeding, nerve damage, worsening of pain, failure of technique, paralysis, and anaphylactic reaction due to local anesthetics, is obtained.

2. Access to the disc is made through a 19-gauge needle to target the center of the disc while deployment is monitored. After a luer-lock is secured onto the needle hub, position of the Wand tip is confirmed with anteroposterior and lateral fluoroscopic views.

3. Placement for stimulation is test by activation of the wand for 0.5 second. If no stimulation is observed, the operator ablates the nuclear tissue by rotating the flange in a 180-degree rotating motion while depressing “Ablation” on the foot pedal.

4. If further decompression is desired, the Wand is repositioned, its placement is confirmed, and tissue removal (ablation) is repeated. The result of the procedure is tissue removal (via plasma dissociation).

Limitations

Nucleoplasty has the following limitations:

Narrow inclusion criteria such as protrusion

Risk of anterior disc height loss

Lack of long-term follow-up and studies comparing technique with the natural course of disc protrusion

Percutaneous discectomy

The Dekompressor 1.5-mm percutaneous discectomy probe (Stryker Instruments, Kalamazoo, MI) utilizes a highly efficient method for removal of intervertebral disc nucleus pulposus entirely under fluoroscopic control [5]. The probe consists of a battery-operated disposable handpiece connected to a helical probe (Fig. 17-17). It is intended for use in aspiration of disc material during percutaneous discectomies in the lumbar, thoracic, and cervical regions of the spine.

Figure 17–17 Top, The Dekompressor discectomy probe (ArthroCare Corporation, Stockholm) consists of a battery-operated disposable handpiece connected to a helical probe. Bottom, Cannula and probe tip detail: A 1.5-mm (17-gauge) or 1.0-mm (19-gauge) outer-diameter cannula provides access to the disc space and acts as a channel for tissue removal. When activated, the probe rotates, creating suction and removal of nucleus pulposus through the cannula using the principle of Archimedes’s pump.

Indications and Contraindications

Indications

Patients exhibiting a contained herniated disc with low back and leg (radicular) pain in whom conservative treatments have failed are candidates for percutaneous discectomy.

Contraindications

Percutaneous discectomy should not be performed in patients with the following conditions:

Traumatic spinal fracture, infection, tumor, pregnancy, or severe co-existing medical disease

Pain originating from structures other than herniated discs

Free fragments, severe bony stenosis, or severely degenerative discs

Severe and rapidly progressing neurologic deficits

Precaution

The procedure should be performed under local anesthesia or conscious sedation to allow patient monitoring for signs of segmental spinal nerve irritation. General anesthesia is contraindicated.

Potential Complications

Infection

Bleeding

Nerve damage

Worsening of pain

Failure of technique

Paralysis

Idiosyncratic reaction, anaphylaxis, and death.

Benefits

Percutaneous discectomy with a probe has the following advantages over open discectomy:

A decrease in the production of perineural scarring and postoperative fibrosis

A reduction in permanent structural alterations, including those produced by invasion of the spinal canal, dissection of the ligamentum flavum, removal of lamina, and disruption of the disc anulus

Decreases in anesthesic requirements procedure time, complication and morbidity rates, and postoperative spinal instability

Limitations

Limitations of percutaneous discectomy using the Dekompressor probe are as follows:

Risk of infection due to the lack of an irrigation system

Difficulty in achieving target-specific decompression