The interior nucleus pulposus of a disc can bulge out of its tough outer annulus fibrosis, creating what is commonly known as a herniation and
more properly called a disc protrusion. When this protrusion compresses a nerve root, it can cause serious problems. Two new minimally invasive techniques, intradiscal electrothermal annuloplasty (IDET) and nucleoplasty, were created to treat disc protrusions.
The theory behind IDET is that heat can modify the collagen and coagulate the pain nociceptors in the annulus of a disc. The exact mechanism of action remains unknown. IDET is a 40-minute outpatient procedure used to treat chronic, discogenic low back pain in patients who failed to respond to noninvasive treatment. In IDET, heat is delivered to the annulus via a specially designed electrode positioned in the outer circumference of a disc adjacent to the annulus fibrosis (see Fig. 10).
Initial case reports in the literature indicate that the outcome of IDET is good for the first 6 months; the long-term effect remains unknown. In the first report of the clinical use of IDET, Saal and Saal found good results in 20 of 25 patients (63). In a 12-month follow-up report on 36 IDET patients (with a convenience control sample of 17 patients whose insurers refused to cover IDET), Karasek and Bogduk noted that 32 IDET patients experienced "various degrees of relief" at the 3-month follow-up. After this, some deteriorated, and others continued to improve (64).
Heary reviewed presentations on experience with IDET at the 2000 North American Spine Society meeting (65). One such presentation noted that, of 170 of 259 patients treated with IDET by 28 physicians, 76% responded in a 6-month follow-up survey that their pain was reduced (66). Despite this and other positive reports, Heary urged caution in adopting the procedure because there was no information from well-controlled studies, and he considered the underlying scientific rationale questionable at best and perhaps incorrect.
The contraindications of IDET have not yet been firmly established, but the criteria used to exclude subjects from trials include herniations larger than 4 mm, sequestered disc herniations (when pulposus material separates from the disc nucleus and floats in the spinal column), previous lower back surgery, vertebral canal stenosis, spondylolisthesis at the site, scoliosis, compression radiculopathy, pregnancy, and certain allergies. Complication rates have been low, but at least one report detailed the major complication cauda equina (67).
Investigators developed the new technique of radiofrequency discal nucleoplasty or coblation nucleoplasty after considering their experience with coblation technology in other parts of the body in light of the well-established theory that the spine operates like a hydraulic system. Using a straightforward technique and a standard radiofrequency generator, nucleoplasty is performed on an outpatient basis with local anesthesia and fluoroscopic imaging (68). The procedure involves inserting a SpineWand into the disc (see Fig. 11) so radio frequency can vaporize disc tissue, creating a channel (see Fig. 12); alternatively, thermal energy coagulates the tissue and widens the channel. This process is repeated several times to create a cone-shaped hole in the herniated disc. The low temperatures (50 to 70(C) involved minimize damage to surrounding tissue. Nucleoplasty may also eventually be used to treat disc extrusion (when pulposus tissue breaks through the annulus, but remains attached to the nucleus) and thus may help more patients avoid surgery.
The exclusion criteria for nucleoplasty studies include sequestered hernia, contained hernia larger than one-third the sagittal diameter of the spinal cord, stenosis, progressive neurological deficits, tumor, infection, and spinal fracture (69). In the first report of clinical experience with
nucleoplasty in 49 patients, the success rate was 82% in the 40 with no previous spine surgery and 67% in the 9 with previous spine surgery.
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