Spine and Spinal Cord Surgery

Spring 2001
Volume 12, Number 1

 Next Article  

Back pain has become an epidemic in the United States costing exorbitant amounts of health care dollars in medical and disability costs. The new millennium has ushered in new and advanced techniques to fight the causes of back pain on all fronts. The new procedures include intradiscal electrothermal annuloplasty, radiofrequency rhizotomy and endoscopic spinal procedures and may be a way to reduce the severity of back pain and its associated personal and financial burdens.

Introduction. John Bonica, MD, the father of pain medicine, felt that pain “is the most pressing issue of modern times.” Despite the greatest efforts of physicians, researchers, and the government, chronic pain has become a modern day epidemic.1 Chronic pain destroys the quality of life by leading to depression, suicide, decreased appetite, increased fatigue, disruption of sleep patterns, and impairs the body’s ability to cope with daily stresses including recovery from illness and injury.2 Chronic pain can be defined as pain which persists beyond the usual course of an acute disease or a reasonable time for the injury to heal, and is continuous or pain at intervals for months or years.3 The estimated costs of back pain alone in this country due to disability and litigation are more than $100 billion.4 The incidence of disability secondary to back pain in the US has risen faster than for any other medical condition, approximately 3000% from 1957 to 1977.5, 6 Specifically, back pain will affect 80% of the population at some time in their life with 35% to 79% of the back pain patients being disabled for over one year after the initial onset of symptoms.7-9

Back pain can be divided into 2 general categories, pain generated from any injury or insult to the spinal cord and/or peripheral nervous system, and pain which arises from the connective tissues commonly referred to as mechanical pain. Virtually every structure in the spine has been implicated as a potential pain generator including the vertebrae, spinal cord, peripheral nerves, intervertebral discs, facet joints, ligaments, muscles, dura, and blood vessels. Regarding the above potential pain generators, facet joints or zygapophysial joints have recently been determined to be the most common cause of chronic axial back pain and thought to be the cause in 50% of the cases.10-12 The second most common cause is thought to be pain derived from the intervertebral disc, thought to occur more as a result of degeneration disc disease than overt disc herniation.13-15 Therapies such as intradiscal electrothermal annuloplasty and nuclectomy (IDET) for the lumbar spine, medial branch rhizotomy (thermo destruction of the nerve innervating the facet joint), and spinal endoscopy have recently become popular in the interventional pain specialist armamentarium for the treatment of the leading causes of pain.

Intradiscal electrothermal annuloplasty and nuclectomy (IDET). IDET is a technology developed by physiatrists Jeffery Saal, MD, and Joel Saal, MD in conjunction with Gary Fanton, MD, a pioneer in the development of radiofrequency use in orthopedics. The primary indications for IDET are patients with back pain reproduced by provocative discography, normal neurological exam, MRI scans demonstrating no neural compression, and failure of standard conservative spine therapy. Absolute clinical results have not been fully elucidated, however, preliminary results are of interest. Conceptually, this technique was developed with goals of stabilizing the disc annulus by strengthening the annular ligaments and destroying the nerve supply to the disc eliminating the pain generated from the diseased disc. Anatomically, the normal disc is made up of an annulus (outside rim) composed primarily of collagen, and inside the annulus lies the nucleus. In healthy discs the outside one third of the annulus is well supplied with nerves. Fremont, et al, biopsied annulus of patients undergoing surgery for spine pathology and found that painful discs exhibited surprising pathological changes not seen in healthy nonpainful discs.16 Using histological examination and modern immunohistochemical techniques there appears to be an ingrowth of nerves deeper into diseased intervertebral discs. Damaged discs exhibit fissures (disruption of the collagen fibers), neovascularisation of the annulus and nucleus, fibrosis, and chondrocyte reduction not seen in nonpainful control discs. In association with the ingrowth of nerves there is an expression of substance P (a nociceceptive pain generator substance), probably a result of the neovascularisation. Kei Hayshi, DVM, PhD, and Mark Markel, DVM, PhD, studied the effects of radiofrequency energy delivered to type 1 collagen.17 It is well known that collagenous tissue shrinks when heated. The collagen undergoes a molecular structural transition when heated as a result of degradation, which is predictable, based upon the applied temperature and time of application. Following the immediate thermal tissue damage, the residual fibroblasts repair the denatured collagen with new collagen possibly improving the tissue mechanics over approximately 3 to 6 months. The marriage of radiofrequency for collagen shrinkage and restructuring with the potential of destroying the nerve supply to the disc, lead the researchers to develop a navigable catheter for placement into the damaged intervertebral disc for pain management. The technique involves placing a needle into the disc percutaneously, then threading the navigable radiofrequency catheter through the needle coiling the catheter into the disc. The catheter is then used in conjunction with a radiofrequency generator to heat the tissues to a specific temperature for a specified period of time. Patients are given instructions to avoid strenuous activity, and utilize a brace similar to that used after spinal fusion surgery. Activity levels are gradually increased. Three to 6 months may be required to determine ultimate outcome.

Derby, et al, performed a one-year pilot study of 32 patients undergoing IDET for chronic discogenic back pain.18 This study suggests there were no significant outcome differences between results at 6-month and 12-month follow-ups. At 12-month follow-up there was a mean decrease in a 10-point visual analog pain scale of 1.84 (sd=2.38). Of the 32 patients, 78% stated the procedure met their expectations or they would undergo the procedure for the same outcome, and 53% of the patients stated that their overall activity level was better compared to before the procedure. Overall, 62.5% had a favorable outcome, 12.5% non-favorable, and 25% experienced no change. There were no significant complications. Insurance companies at this point frequently view this technology as experimental and non-reimbursable. Hopefully, as more clinical trials become available this technique will clarify itself regarding true indication and outcomes.

Radiofrequency. Radiofrequency (RF) lesioning is fast becoming a technique used not only for the destruction of the nerves in the annulus, but also the nerves which innervate the facet joints of the spine. Theoretically, if cervical or lumbar pain can be determined to be emanating from the facet joint pathology, then destruction of the medial branch nerves to the facet joints may eliminate the pain at least temporarily. Specifically, this technique coagulates the medial branch nerves to the facet rendering the joint temporarily anesthetized rather than correcting the underlying pathological disorder. It is a commonly held clinical belief that spinal extension induced pain indicates facetogenic pain. This type of pain is hypothesized to be caused by flexion-extension trauma, progressive arthritis, disc degeneration with a change in spinal weight disruption, or perhaps deterioration of areas above or below fused spinal segments secondary to increased stress in the area of movement. There have been 2 excellent studies performed, one regarding the treatment of cervical and the other lumbar facet derived pain. Lord, et al, studied 24 patients with pain in one or more cervical facet joints secondary to motor vehicle accidents. The source of the pain was determined by 3 double-blinded placebo-control blocks of the medial branches of the 2 dorsal rami supplying the painful joint. Subjects needed to have complete relief of the pain for the appropriate duration of the local anesthetic and no response to the placebo to be included in the study. The 24 subjects were divided into 2 groups of 12 patients. Each group underwent an identical procedure except for the sham group, which had needle placement without current application. The surgeon and patient were blinded to the treatment. Patients were followed until 50% of their pre-treatment pain level returned. The time required for 50% of the pain return in the treated group was 263 days compared to 8 days for the control group. At 27 weeks, 7 of the treated patients versus only one of the control patients were pain free.19 Dreyfuss, et al, studied 460 lumbar pain patients and pared these down to 15 patients with pure facet pain syndromes based upon telephone interview, physical examination, and facet medial branch blocks with 2 local anesthetics. All 15 patients received RF to the lumbar medial branch nerves of the corresponding painful facet. Dreyfuss found that 87% of patients experienced at least 60% reduction in their pain at one-year follow-up.20 In summary, when utilizing strict inclusion criteria, good results can be expected. Many pain physicians are performing RF without the use of the recommended multiple screening diagnostic injections due to payer authorization and/or reimbursement concerns. Consequently, the results are not as predictable either in quality or duration of pain relief.

Spinal endoscopy. Spinal endoscopy or the ability to visualize the spine through a minimally invasive technique is not a new technique. In the 1930’s, Dr J. Lawrence Pool examined the spine using an arthroscope and described the pathological conditions in cauda equina syndrome.21 Saberski, et al, have demonstrated the technique to safely visualize the spinal canal contents.22 With the advent of more sophisticated endoscopic technology this technique is becoming a modality more investigators are utilizing to diagnose and attempting to treat intraspinal pathology. The indications for spinal endoscopy are the evaluation of patients not responding to conservative treatment, those patients with filling defects on epidurogram corresponding with the physical symptoms, and failed back surgery syndrome with a strong radicular component. The technique involves placing an 8 french introducer into the caudal canal, a 2.7 mm video guided catheter containing the .9 mm spinal endoscope is passed throughout the introducer into the epidural space to the area of pathology with x-ray assistance. Saline is infused under pressure to dilate the epidural space and provide a cavity in the spine for visualization. The guide catheter has small injection ports for injection of saline or medication to mobilize adhesions with hydrostatic distension of the space or apply medications to areas which may not be accessible using standard spine injection techniques. If hydrostatic pressure is not helpful at alleviating the filling defect some investigators are using pulsed laser treatments to free up the adhesive scar tissue and theoretically decrease the pain generator.23 Currently, few investigators have the experience or expertise to utilize this technique effectively. Technically, current optics technology often provides limited visualization. Hence, many insurance companies consider spinal endoscopy experimental and authorize and reimburse on a case-by-case basis.

Conclusion. A tremendous effort is being exerted in finding the etiologies and appropriate focused treatment of spine pain, not only because of the toll it takes on the individual, but also the economic impact of society in terms of lost time at work and disability. With strict adherence to patient selection and controlled clinical trials, techniques such as those described above may be included in the treatment paradigm of chronic spinal pain.

Address comments and questions to:

Scott Hompland, DO
125 E. Hampden Avenue
Englewood, CO 80113

 Next Article