Vertebral axial decompression therapy for pain associated with herniated or degenerated discs or fac

The outcomes of vertebral axial decompression (VAX-D) therapy for patients with low back pain from various causes are reported. Data was collected from twenty-two medical centers for patients who received VAX-D therapy for low back pain, which was sometimes accompanied by referred leg pain. Only patients who received at least ten sessions and had a diagnosis of herniated disc, degenerative disc, or facet syndrome, which were confirmed by diagnostic imaging, were included in this study; a total of 778 cases. The average time between the initial onset of symptoms and the beginning of this therapy was 40 months, and it was four months or more in 83% of the cases. The data contained the patients' quantitative assessments of their own pain, mobility, and ability to carry out the usual 'activities of daily living'. The treatment was successful in 71% of the 778 cases, when success was defined as a reduction in pain to 0 or 1, on a 0 to 5 scale. Improvements in mobility and activities of daily living correlated strongly with pain reduction. The causes of back pain and their relationship to this therapy are also discussed. [Neurol Res 1998; 20: 186-190].

INTRODUCTION

For most patients, the cause or causes of persistent low back pain remains poorly understood. Although imaging procedures, including CT and MRI, are able to accurately define structural pathology, the correlation of these anatomic findings with physiology, back pain, and other clinical complaints is imprecise1. Although surgical decompression, epidural blocks, and spinal instrumentation can sometimes help patients suffering from back pain, these treatments do not completely take the biomechanical function of the disc into account, and may leave patients unrelieved of their suffering. In addressing the dysfunction of the disc with discectomy or surgical instrumentation, the biomechanical and physiological function of the disc is permanently disrupted.

Mechanical low back pain is usually aggravated by activities that increase axial loading on the spine, such as sitting, standing, and lifting. Patients may describe some relief with walking, but more particularly, by lying down, which unloads the spine and reduces intradiscal pressure (2,3). The causes of mechanical low back pain may include degenerative disc disease, degenerative spondylosis with limitation of range of motion, facet arthropathy, relative lateral recess stenosis from a combination of the above, microenvironment presure changes affecting the thecal and epidural space from disc bulging, subligamentous and/or extruded herniation, and segmental instability.

Pain generation from degenerative disc disease is probably multifactorial. A number of potential mechanisms are specifically addressed by the lumbar vertebral body separation achieved during therapy. With aging, disc desicction occurs, disc height is lost, and this process is accelerated with activities which produce high physical loading of the lumbar spine (4). Osteophytes develop along the anterolateral and posterior border of the vertebral bodies, and facet arthropathy increases as degenerative disc change advances (5). Normal vertebral body separation is lost as the disc degenerates. Redundancy of the posterior longitudinal ligament and ligamentum flavum combine with osteophyte encroachment upon the neuroforamen or central canal, resulting in stenosis at these sites, which is increased by axial loading of the spine.

The blood supply to the nerve roots of the cauda equina is sensitive to compression. Even at pressures of only 5-10 mmHg, the flow in over 20% of the venules was completely stopped (6). Flow in all the capillaries stopped at pressures between 20 and 50 mmHg. A pressure of 30 mmHg is slightly less than one pound per square inch, so solute transport is easily reduced. Even vertebral distractions (increased separation) of 1 or 2 mm per disc would reduce ligamental redundancy and help to restore canal/foraminal patency, reduce venous congestion and increase axoplasmic flow. Furthermore, the effects of lumbar spine lengthening may be sustained for a period of time after lumbar distraction has been stopped.

Twomey (7) placed lumbar vertebral columns removed from 23 male cadavers under 9 Kg of sustained traction for 30 min and measured an average increase in length of 9 mm. Thirty minutes after traction was removed, 13 of the 23 specimens had returned to baseline length, but the remaining 10 spines showed residual elongations ranging from 0.3 mm to 4 mm. Additionally, the data suggested that sustained traction had had a longer lasting effect on elderly spines. The mechanism of this residual deformation was not elaborated upon by the author, but disc rehydration may have been a factor since each column was soaked in normal saline and remained saturated by periodic additions of saline to a close fitting bag surrounding each column during the study.

That lumbar traction, if adequately applied, can effect physical change in patients suffering from back pain is well described by Gupta and Ramarao (8). They used water soluble contrast medium and epidurography to study 14 patients with prolapsed intervertebral disc syndrome before and after 10 to 15 days of continuous traction. Ten patients showed definite clinical improvement, with reduction in back pain and sciatica. Nine of these patients showed complete resolution of the defect on epidurogram and one of them showed partial reduction. The authors concluded that disc protrusion may be safely treated by traction. Mathews also demonstrated the effectiveness of lumbar traction in two patients by epidurography. Disc protrusions were decreased and an average vertebral distraction of 2 mm per disc space was shown in radiography (9). Judovich found that a traction force of approximately 26% of the body weight was needed just to overcome the resistance between the lower half of the patient and a (nonsplit) table (10).

Intuitively, lumbar traction should be successful in alleviating many of the conditions which cause low back pain and associated radiculopathy. Unfortunately, studies of clinical efficacy have yielded equivocal results. Previously, the successful application of lumbar traction has been limited by patient tolerance and the design of mechanical devices. Patients had difficulty tolerating the forces needed to relieve pain if delivered continuously. Furthermore, the thoracic corsets worn by patients to prevent movement on the table were uncomfortable, restrictred respiration, and can compromise venous return to the heart. Technological advances have now led to the development of equipment that has been found to achieve decompression of lumbar discs without stimulating the reactive reflexes of the lumbar musculature that can otherwise overcome efforts to effectively distract vertebral bodies.

The VAX-D therapy table is shown in Figure 1. The split table design eliminates frictional resistance between the patient and the table and allows controllable effective axial distraction tensions to be applied to the lumbar vertebral column. The equipment applies distractive forces in a gradual, progressive fashion, designed to achieve distraction of the vertebral bodies without eliciting reactive reflex muscular resistance. A portion of a typical chart recording of the tensile force applied to a patient's spine as a function of time is shown in Figure 2. Each decompression phase, during which the tension is increased, normally lasts for one minute. The force is increased more slowly in the latter part of the decompression phase. The tension is then gradually decreased, over a period of 30 sec, to about 20 pounds, which is maintained during the rest phase. Another cycle then starts. The avoidance of paravertebral muscle contraction, stimulated by homeostatic proprioceptor and axon reflex mechanisms allows the distraction of the vertebral bodies necessary to achieve decompression of the intervertebral disc. The therapy is administered via an automated logic control mechanism which systematically applies distractive tensions and rest periods in a cyclic fashion. The typical therapy session consists of 15 cycles of tension and relaxation. This periodic process allows patients to withstand stronger forces than can be tolerated when static techniques are used and it promotes accommodation and relaxation during the therapy session. The upper body is fixed by means of the patient grasping adjustable hand grips, designed to eliminate the use of a thoracic corset. Consequently, there is no risk of circulatory or respiratory compromise. The pelvis is secured with a specially designed harness that adjusts snugly and applies forces primarily to the lateral pelvic alae, thus minimizing anterior-posterior pressures and reactive muscle spasm during the distractive period of each cycle.

VAX-D treatment has been shown (11) to decompress the nucleus pulposus to pressures below - 100 mmHg. This creates a tremendous potential diffusion gradient across the disc space, which is otherwise an avascular structure. Glucose and oxygen enter the disc at the end plate region while sulphate ions needed for the production of new glycosaminoglycans enter from the annulus fibrosis (12). Thus therapy may augment nutrient flow into the disc, facilitating structural restoration of the disc and promoting disc rehydration, since proteoglycans bind water (13). These effects may be cumulative with repetitive therapy sessions.