New Dynasty of the Disc
SAN FRANCISCO -- One of the major themes of the May '93 American Back Society (ABS) meeting in San Francisco was that the clinical importance of the intervertebral disc had been exaggerated ever since the seminal Mixter and Barr paper of 1934.1 At the '93 meeting, Dr. Simmons was only one of several presenters who announced the end of an era, that of the "Dynasty of the Disc,"2 and called for the need to rethink the conventional wisdom by which back pain + leg pain = ruptured disc.
Well, dynasties come and go. One need look no further than the case of the Dallas Cowboys, whose elimination from NFL playoff season (as this article goes to press) by a second year expansion team drew this headline from USA Today: "26-17 loss derails Dallas dynasty." Several presenters at the December 12-14, 1996 ABS meeting sounded the clarion for a new "Dynasty of the Disc," with renewed emphasis on those treatment techniques most likely to impact upon it. This symposium provided evidence from both basic science and clinical research to support this point. Part I of my symposium coverage reviews the various presentations related to the intervertebral disc.
Kuslich on Progressive Local Anesthesia
Dr. Stephen D. Kuslich uses a controversial surgical technique called progressive local anesthesia to identify pain generators in low back and sciatica cases. Identifying the pain generators should enable the design of rational and appropriate treatments. An operating microscope is used on an awake but "slightly sedated" patient to dissect down to the pathology, and note the location and degree of pain, especially its similarity to the preoperative pain. After examining 114 consecutive patients with degenerative disc disease in this way, all of whom had documented herniated discs, nerve root compression, and preoperative sciatica, Dr. Kuslich takes strong exception to the old saw by which up to 90% of low back pain is of idiopathic or nonspecific origin.
He has found that fat, ligamentum flavum, lumbar fascia, lamina and facet bones, spinous processes, facet cartilage, uncompressed nerve roots, uninflamed dura, and the nucleus of the disc are remarkably pain insensitive. The normal nerve root is also pain insensitive, at least to gentle mechanical stimulation. Injecting facets probably reproduces symptoms only because the capsule happens to reside close to true pain generators, such as the posterior disc or the inflamed nerve root. Scar tissue is not itself painful, but can bind nerve roots to the walls of the spinal canal, making them more susceptible to compression or traction and thus likely to generate pain. Although joint capsules were tender in 20% of the (usually older) patients, stimulation produced local back pain only and never sciatic pain.
The disc in one-third of cases provokes about as much pain as "cutting hair." In another third, it is mildly pain sensitive and requires no anesthetic during surgery. In the remaining third of cases, the disc is painful and does provoke the preoperative pain. Although the nucleus is not pain sensitive, stimulating the endplate reproduces that severe back pain that patients perceive as nauseating.
Dr. Kuslich is sure that the majority of severe low back pain comes from the disc, mediated by the vagus nerve. When asked to explain the existence of low back pain without discopathy, he said he could not in many cases, but this is not a large percentage of the total cases out there. Buttock pain comes from simultaneous compression of nerve roots and the annulus of the disc. True sciatica comes from compressed, stretched, or inflamed nerves, in which case even mild pressure will reproduce the symptoms. Indeed, If the nerve is blocked, the sciatica is immediately and totally prevented. More pressure maintained for sustained times will produce a more distal pain, probably due to segmental ischemia of the nerve root.
Derby and Provocative Discography
Dr. Richard Derby agreed that the disc and the sacroiliac joints are important pain generators, but only rarely the posterior joints. He described a procedure called provocative discography: the injection of a radiopaque dye into the nucleus pulposus of an intervertebral disc thought to be causing low back pain, especially as a pre-surgical procedure designed to give the surgeon a precise anatomical diagnosis. The dye demonstrates a variety of appearances, ranging from the "cotton ball" appearance of a normal nucleus, to the very diffuse pattern of internal disc disruption, and finally the escaping dye appearance that confirms the herniation.
Discography is not only morphological, but directly provocative in that the injection may increase discal pressures and register pain. Apart from the information provided by the radiological image, the injection of the dye may reproduce the patient's preoperative pain, and do so exactly. Low levels of pressure will only generate pain in damaged discs. Provocative discography can verify if a disc is a pain generator, by pumping it up with contrast material. Although a disc may be so injured that injecting dye cannot increase its internal pressure enough to cause pain, the ability of the disc to take in more than 1-2 cc of fluid already suggests severe disruption. Dr. Derby discussed the "white dot sign" on MRI (as identified by Dr. Charles Aprill): a high intensity zone amidst the annular fibers, indicating fissuring and strongly predicting pain on discographic injection.
Bischopp on the Cyriax Legacy
Here from Belgium for his presentation, "The Cyriax Legacy," Mr. Bischopp worked for seven years as a physical therapist with Dr. Cyriax, and is currently associated with Orthopaedic Medicine International, Belgium. Like Dr. Kuslich, Cyriax did not believe low back pain to be mostly idiopathic, stating that the disc is often involved, either directly or through its impact on other pain sensitive structures like the dura. By his dural concept, 90% of all problems in the low back would be due to a disc protrusion. The nociceptors of the dura mater can produce multisegmental referred pain, aggravated by coughing, sneezing and straining. Although his beliefs remain controversial to this day, many contemporary researchers and clinicians attribute increasing significance to disc pathology not necessarily disc protrusion, as Cyriax emphasized, but that and other types of disc problems as well, including internal disc disruption.
Cyriax believed low back pain to be disco-dural or disco-radicular, and thought the posterior facetal joint to be pain insensitive, as confirmed by Dr. Kuslich. A disco-dural patient may experience referred pain down to the foot, not to be confused with the radicular (sciatic) pain experienced by a disco-radicular patient. According to Mr. Bischopp, Cyriax felt his most important contribution to be a standardized examination of the body's moving parts by a process of selective tension.
McKenzie and the Significance of Extension
Mr. Robin McKenzie has long found his name synonymous with intervertebral disc rehabilitation and the therapeutic value of extension maneuvers. He finds that ABS meetings have permitted him to mingle with PTs, DCs, and other allied health professionals in a supportive manner, minus the usual feelings of mutual suspicion and even hostility. By his own admission, he was very interested to find that chiropractors actually have two "heads" (a slip of the tongue, hastily corrected to "legs"), care about their patients, and are interested to learn about other ways of treating them.
Commenting on the usual low quality of the randomized controlled clinical trials on low back pain, he proposed a "certificate of competency and license to conduct clinical low back trials," which requires a "rudimentary understanding of where the low back is," and "a better than average chance of coming up with something inconclusively equal to a random chance event."
Asked how his many years of experience have led him to make changes in his low back diagnostic and treatment protocols, he answered: "If it ain't broke, don't fix it." His central procedure remains a mechanical evaluation that identifies which body positions "centralize" or "peripheralize" leg pain that accompanies low back pain. It consists of repeated end-range test movements in various directions, which may aggravate, ameliorate, or leave unchanged both low back midline and leg pain. "Peripheralizers" experience increased distal symptoms, whereas centralizers experience decreased distal symptoms. The examination findings immediately dictate the required treatment, which may involve flexion, but more typically extension, lateral flexion, or combinations thereof.3
Mr. McKenzie believes that disruption of discal tissue results from prolonged flexion, which rationalizes why the hyperlordotic position may be beneficial: it produces anterior discal movement. Although until recently the therapist did the patient positioning, repetitive patient generated end-range loading is a newer technique coming in. Recently, chiropractic manipulation and McKenzie treatment were found to be equally beneficial in a randomized prospective study.4
Donelson on Whether a McKenzie Evaluation Can Predict a Discogram
Dr. Donelson has been investigating for some time now whether patient responses to lumbar bending in multiple directions, according to the McKenzie protocol, could predict the discogram. Dr. Donelson's current findings in a prospective study validate his remarks of two years ago, reported then as preliminary findings in this column: "The McKenzie spinal assessment appears to be a dynamic, noninvasive functional evaluation of symptomatic disc pathology."5
In a prospective study, 63 chronic low back patients, in all of whom nonoperative care had already failed, were referred for discograms. They underwent examination by an experienced McKenzie practitioner (blinded as to the patients' history and MRI results), and immediately thereafter received the discogram. The mechanical assessment found 50% to be centralizers, 25% peripheralizers, and 25% to show no change. In addition, 74% of the centralizers had positive discograms, of which 91% were contained (no leakage of dye). Of the peripheralizers, 69% had positive discograms, with only 54% contained. Of those showing no symptomatic change, only 12.5% had positive discograms. It appears that both peripheralizers and centralizers have discogenic pain, but that the centralizers have a competent annulus, whereas the peripheralizers do not. This makes the peripheralizers a more likely candidate for surgery. Dr. Donelson believes that the patients who were unresponsive during the mechanical examination did not have discogenic pain.
From the Bizarre Surgery Department
Dr. James Zucherman is an orthopedic surgeon and director of Saint Mary's Spine Center of San Francisco, one of the first multidisciplinary back centers in the United States. St. Mary's has been a pioneering institution in the development of back school and stabilization exercises, as well as surgical procedures. The latest and perhaps most novel procedure under development is WARP abdominoplasty: wide abdominal rectus plication, further described as "back surgery without surgery." (Plication refers to shortening a structure by surgically taking in its tucks.)
In this technique, the plastic surgeon decreases the mass of the abdominal wall, through a reduction of the expanse between the umbilicus and pubic area. Up to 14 cm of abdominal wall fascia can be plicated and then closed. The indications include a multilevel problem, internal disc disruption or herniation, the finding that abdominal compression with bracing gives relief, and prolonged refractory pain. There is radiographic evidence of increases in intervertebral space, as well as MRI evidence of possible disc reconstitution. Muscle strength evaluation demonstrates a significant increase in transverse abdominis-internal oblique complex strength with surgery alone, prior to the institution of any rehabilitative therapy.
Coming Attractions for Part II
My next column continues coverage of the 1996 meeting of the American Back Society. It discusses each of the following presentations:
References
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