A New Treatment For Painful Disc Degeneration. The use of heat to treat various ailments is not new. Hippocratic use of a flaming brand to the shoulder would cure recurrent dislocations. More recently we have been applying modern “Flaming brands” via an arthroscope to the anterior capsule of the shoulder using radio–frequency probes.
The intervertebral disc presents a particular problem as it has high impedance and fails to allow sufficient energy to be delivered to raise the temperature of the discs to a therapeutic level. This problem has been overcome by a novel method of delivery of the thermal energy from a radio–frequency generator via a special intradiscal catheter–the Spine CATHTM.
A Big Problem
Over 60% of the adult population will suffer from significant back pain in their lives and 34% of these will have periods of absence from work because of back pain. The cost of back pain to the patient, in lost income, to society, in lost production, benefit payments and medical care and to the medical and allied professions who treat these patients is immense.
- 61% of all adults have back pain at some time in their lives.
- 34% will loose time of work because of back pain.
Provocative discography, spinal probes, diagnostic injections and MRI findings may suggest the site of the painful locus but have to be taken in context with the whole patient and are not a substitute for good history taking and examination.
Intradiscal Electrothermal Therapy
Intradiscal Electrothermal Therapy is a method of selectively heating the posterior annulus to 90 degrees centigrade to allow thermal destruction of nociceptors within the degenerate annulus, and to denature the protein of the posterior annulus in such a way that it undergoes a repair process.
The effect of heating the annulus–(Collagen and pain fibers) The lamella structure of the lumbar disc annulus undergoes a process of delamination and fissuring which begins after the nuclear hydrostatic pressure becomes reduced early in the degenerative process. The posterior annulus is principally affected due to high stress concentrations. A partial healing response occurs which leads to the ingrowths of granulation tissue and nerve fibers. The annular nociceptors, through either a direct mechanical stimulus or activation by inflammatory mediators, are becoming widely regarded as the prime contributor to discogenic pain. Collagen contraction occurs at a molecular level, with temperatures between 60 and 80 degrees centigrade breaking the hydrogen bonds supporting the triple helix structure of the collagen molecule. Although it reduces the tissue strength initially, this collagen modification stimulates a remodeling process that has demonstrated an increased collagen density and restored strength in longer–term histological and biomechanical research studies.
Research and clinical experience has long demonstrated that tissue temperatures above 42 degrees can thermo coagulate (permanently desensitize) unmyelinated nociceptive fibers. Previous experience with neuroablative procedures has shown that nerve regeneration can often occur, causing a return of symptoms. The objective of the Intradiscal Electrothermal Therapy procedure is to safely elevate the temperature over a broad area of the posterior annulus to the levels that thermo coagulate the annular nociceptors, and contract annular collagen thereby improving the structural integrity of the disc as a longer–term solution than neuroablation alone.
The problem of utilizing the effect of thermal injury to the disc was how to deliver sufficient energy safely to the disc. Laser probes generate high temperatures that result in vaporization of the disc material. Pure radio frequency probes within the disc also fail to heat the disc as it has high resistance and any heating effect is rapidly lost. The Spine CATHTM however allows precise intradiscal navigation via a 17–gauge needle, of a resistive heating coil. Using the navigation capabilities of the catheter the coil can be placed within the posterior part of the annulus, the likely site of the painful inflammatory tissue associated with the painful spinal segment. The procedure is performed under intravenous sedation using fluoroscopic control. Needle insertion and the heating protocol take between half to one hour. Throughout the procedure any risk of misplaced catheters heating normal neural structures is reduced, as the patient is awake and can report radicular pain.
The pilot study performed at Stanford University by Saab and Saal, (NASS, 1998 and Spine, in press) included a group of thirty–six patients who were to undergo fusion surgery but instead elected Intradiscal Electrothermal Therapy. Results revealed 72% of patients achieved statistically significant improvement in function, as measured by the SF36 outcome assessment, and 80% of patients achieved statistically significant reductions in pain as measured utilizing VAS scores.
Spine CATHTM has been used in a clinical setting for three years and the early results are promising. As with any new device correct patient selection, surgeon training and careful follow–up are required. Joel and Jeff Saal from Stamford University, are the pioneers of this technique and their experience has been used to forward the use of this catheter. Although it requires a degree of technical skill, it remains a safe technique in trained hands, and one that will surely take it’s place as a standard method of treating painful degenerative disc disease affecting the lumbar spine.
From A Surgeons View!
For a spinal surgeon who is performing the Intradiscal Electrothermal Therapy procedure, it is technically only a little more difficult than discography. The procedure is tolerated well by patients, and the reduced bed occupancy, reduced implant costs and ease of nursing are making it a popular procedure. This is clearly an intervention that has to be reserved for patients who have a likely discogenic cause of their pain.