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VAX-D RESEARCH

A Prospective Randomized Controlled Study of VAX-D and TENS for the Treatment of Chronic Low Back Pain
E.Sherry, MD FRACS  Department of Orthopaedics, Sydney University.
Peter Kitchener M.B. B.S. FRANZCR
Russell Smart M.B.Ch.B.
Journal of Neurological Research, Volume 23, October 2001

Vertebral axial decompression therapy for pain associated with herniated or degenerated discs or facet syndrome: An outcome study

Earl E. Gose, William K. Naguszewski* and Robert K. Naguszewski*

Department of Bioengineering, University of Iliinois at Chicago, Chicago, IL. USA

*Coosa Medical Group, Rome, Georgia, USA

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].

Keywords: Low back pain; herniated disc

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.

Figure 1: Patient undergoing treatment on the VAX-D Therapy Table

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.

Figure 2: chart recording of tension versus time for five cycles of the typical 15-cycle VAX-D Therapy session

MATERIALS AND METHODS

Data was collected from twenty two medical centers in the USA for patients who received VAX-D therapy for low back pain. Only patients who received at least 10 treatments and had a diagnosis of herniated disc, degenerated disc, or facet syndrome, which was confirmed by imaging studies, were included in the study. The average number of treatments was 17 for facet syndrome, 19 for degenerative disc disease, and 20 for other diagnoses. The data contained the patients' assessment of their own pain, mobility, and ability to walk and sit. The pain scale ran from no pain (0) to severe pain (3). The mobility limitation scale was: No limitation (0), slightly limited (1), very limited (2), and completely immobile (3). The activity limitation scale was: walks frequently (0), walks occasionally (1), chairfast (2), and bedfast (3(). The treatment schedule, including the use of other modalities, the duration and frequency of VAX-D therapy, and medication was also recorded, as well as the patient's history. The symptoms were recorded at the beginning, mid-point, and end of the treatment schedule. The patients' satisfaction with the treatment was quantified as: not satisfied (0), slightly satisfied (1), very satisfied (2), and completely satisfied (3).

The data were divided into five groups:

1. The first group which contained 34 cases, included all patients with extruded herniated discs, whether or not additional lesser problems were present.
2. The second group contained 195 cases of multiple herniated discs, without extrusion, with or without degenerative disc disease.
3. The third group consisted of 382 patients with a single herniated disc, regardless of degenerative disease.
4. The fourth group contained 147 cases of degenerative disc disease, without herniation.
5. The fifth group contained 19 cases with facet syndrome. Five cases of facet syndrome which had a pain reduction to 0 or 1 before 10 treatments, and one that had a reduction to 2, received less than 10 total reatments, so they were not included in the data base.

RESULTS

If treatment success is defined as a reduction in pain to 0 or 1 on a 0 to 5 scale, the treatment was successful in 71% of the 778 cases. The success rate varied from 53% for the patients with extruded herniated discs, to 73% for patients with a single herniated disc. It was 72% for people with multiple herniated discs and 68% for facet syndrome. On a pain scale of 0 to 5, the people with extruded herniated discs had an average pain of 4.16 at the beginning of treatment and an average of 1.82 after treatment, a reduction of 56%. The cases of multiple herniated discs went from 4.13 to 1.18, a reduction of 71%. The patients with a single herniation had a reduction from 4.16 to 1.09, or 71%. The degenerative fisc cases reduced from 3.93 to 1.17, a 70% reduction. The patients with facet syndrome had a reduction of 4.00 to 1.13, a 72% reduction in pain. Overall, 71% of the patients experienced a reduction in pain to 0 or 1. The reduction in the average pain score was also 71%. One percent of the patients reported increased pain, 7% had no change, 92% improved by 1 unit or more, 87% improved by 2 units or more, and 70% improved by 3 units or more. A summary of these findings is shown in Table 1.

Table 2 shows how the average pain, mobility, and activity scores for the entire group of 778 patients improved during treatment. Although 51% of the pain reduction occurred during the first half of the course of treatment, 56% of the mobility improvement and 55% of the activity improvement occurred during the last half.

On a rating scale of 0 to 3, increases in spine mobility of one grade or more was seen in 77% of the patients with mobility limitations. Functional increases of 1 or more grades in the activity score was recorded in 78% of the patients who, before treatment were either unable to walk or capable of only limited walking. The coefficient of linear correlation14 between mobility and pain scores was 0.72. Between pain and activity the correlation was 0.60, and between activity and mobility it was 0.59. On a scale of 0 to 3, the average satisfaction with treatment was 2.4, which lies between 'very satisfied' and 'completely satisfied'.

In this study, 31 patients had previous lumbar disc surgery. MRI scans showed scar tissue that could potentially entrap nerve roots. Despite this, 84% of this group's pain scores and 71% of their mobility scores and 61% of their activity scores improved by one unit or more with therapy, and 65% of their pain scores were reduced to 0 or 1. Vertebral axial decompression was well tolerated.

Vertebral axial decompression therapy outcomes: Earl E. Gose et al.

DISCUSSION

We consider VAX-D therapy to be a primary treatment modality for low back pain associated with lumbar disc herniation at single or multiple levels, degenerative disc disease, facet arthropathy, and decreased spine mobility. Physiology (pain and mobility) and pathology correlate imprecisely. We believe that post-surgical patients with persistent pain or "Failed Back Syndrome' should not be considered candidates for further surgery until a reasonable trial of vertebral axial decompression has been tried.

Low back mobility increased subsequent to therapy and correlated well with pain reduction. Both of these factors are important in areas such as Workers Compensation and personal injury. Estimates of permanent partial impairment rely heavily on mobility aspects, as seen in the AMA Guides to the Evaluation of Permanent Impairment, 4th edition. Although allowance for pain is made in the percentage of impairment, the determination of impairment is made by determination of spine mobility using the range of motion model. By definition no patient can be assigned any impairment rating until maximum medical improvement (MMI) is reached. We submit that patients can usually be brought to a higher level of MMI by this therapy because of the anticipated improvements in mobility.

In summary, the pain, activity, and mobility scores were all greatly improved after therapy. VAX-D by its unique design may more precisely address the physiology of persistent low back pain than other conventional therapies. We consider it to be a front line treatment for degenerative spondylosis, facet syndrome, disc disease and nonsurgical lumbar radiculopathy.

REFERENCES

1. Heldeman S. North America Spine Society: Failure of the pathology model to predict low back pain. Spine 1990; 15:718-724.
2. Wheeler A.D. Diagnosis and management of low back pain and sciatica. Am Family Physician 1995; 52:1333-1341.
3. Scientific approach to the assessment and management of activit-related spinal disorders. A monograph for clinicians. Report of the Quebec Task Force on spinal disorders. Spine 1987; 12(Suppl 7):1-59.
4. Videman T, Saina S, Crites Battle M, Koskinen S, Gill K, Paanaman H. The long term effects of physical loading and exercise lifestyles on back-related symptoms, disability, and spinal pathology among men. Spine 1995; 20:699-709.
5. Anderson GBJ, McNeill TW. Lumbar Spine Syndromes Evaluation and Treatment. New York: Springer-Veriag Wien, 1989: pp.1-215.
6. Olmarker K, Rydeuik B, Holm S, et al. Effects of experimental graded compression on blood-flow in spinal nerve roots. J Orthop Res 1989; 7:817-823.
7. Twomey LT. Sustained lumbar traction: An experimental study of long spine segments. Spine 1985; 10:146-149.
8. Gupta RC, Romarao SV. Epidurography in reduction of lumbar disc prolapse by traction. Arch Phys Med Rehabilitation 1978; 59:322-327.
9. Mathews JA. Dynamic discography: A study of lumbar traction. Ann Phys Med 1968; IV:275-279.
10. Judovich BC. Lumbar traction therapy-elimination of physical factors that prevent lumbar stretch. JAMA 1955; 159:549-550.
11. Ramos G, Martin W. Effects of vertebral axial decompression on intradiscal pressure. J Neurosurg 1994; 81:350-353.
12. Nachemson AL. The lumbar spine: An orthopaedic challenge. Spine 1975; 1:59-71.
13. Ballard WT, Weinstein JN. Biochemistry of the intervertebral disc. In: Kirkaldy-Willis WH, Burton CV, eds. Managing Low Back Pain, New York: Churchill Livingston, 1992: pp.39-48.
14. Gose EE, Johnsonbaugh R, Jost S. Pattern Recognition and Image Analysis, Upper Saddle River, NJ: Prentice-Hall PTR, 1996: pp.1-484.
15. This article is reprinted with the permission of the authors from The Canadian Journal Of Clinical Medicine, Volume 5, Number 1.

AN OVERVIEW OF

VERTEBRAL AXIAL DECOMPRESSION

By Dr. Frank Tilaro

Introduction

Low back pain is a growing epidemic among industrialized societies. In the United States it is the most common work related disorder. The cost to industry is staggering, with estimates running 20 billion dollars or more annually. (4,42) Total payments for a single Workman's Compensation claim may be as high as $100,000.

Abenhain and Suissa studied the 1-yearincidence of work related low back pain in the province of Quebec for the year 1981. (1) Work absence due to back pain has an incidence of 1.4%. Seventy-four percent of work related injuries return to work within 1 month. 7.4% were out of work for more than 6 months. 75% of the direct total cost was borne by 10% of the absentees. Recurrence rates were 20% at 1 year and 36% after 3 years. Men had higher recurrence rates than women; drivers and nurses had higher recurrence rates than other occupations.

The recovery rate of the Quebec workers is similar to other countries. After 1 year 4.3% remained absent from work. Incidence rates of compensated back injuries by industrial sector showed that foresters and miners are at the top with 4.9% and 3.3% respectively.

Back Pain - A Diagnostic and Therapeutic Dilemma

Effective diagnosis and therapy requires thorough knowledge of spinal biomechanics. Our approach to back pain has been centered on a patho-anatomical model but unfortunately the model frequently fails to comply with the clinical picture. The Quebec Task Force Report stated: "There is so much variability in making a diagnosis that this initial step (i.e. clinical assessment) routinely introduces inaccuracies which are then further confounded with each succeeding step in care."(43) Adding to the confusion is the belief by too many physicians, patients and insurers that high tech imaging is the standard for establishing a diagnosis. However, the high rates of false positive and false negative findings point to the inadequacies of these studies in identifying the pain generating lesions (8,19,20,48,49). Nachemson states: "A confirmatory imaging study is indicated only if surgery is contemplated. Clinical symptoms and findings remain the most important basis for diagnosis."(28)

The natural history of low back pain with and without radiculopathy has been described.(10,37,47) Spontaneous regression takes place in 80% to 90% of patients with low back pain by 6 weeks and a significant percentage of patients with sciatica report a satisfactory response to conservative medical management.

Studies on disc surgery emphasize inappropriate patient selection as the cause for surgical failure. (11,16,30,44) In Kramer's address to the International Spine Society he emphasized that the surgical failed back syndrome is the worst possible scenario a spine surgeon faces. (22) In North America the incidence for this iatrogenic disease is about 15%, compared to 5% with most European countries.(28) Comparisons between the United States and Europe indicate that the frequency of surgery in the U.S. is four times greater.(11) Statistics from the Back Pain Outcome Assessment Team compiled from 1979 to 1987 indicate a rapidly growing number of disc excision and fusion operations performed each year, further escalating the cost. (11,44)

Studies of the various surgical procedures largely lack validity and controlled prospective studies are rare .(7) A randomized study by Revel demonstrated percutaneous discectomy has little value (32) and the same is true for laser discectomy.

Chemonucleolysis is superior to saline injection but inferior to surgical discectomy. While chemonucleolysis had its followers for a period of time, it has fallen into disrepute because of the serious side effects including anaphylaxis and myelitis and should no longer be considered an option. There are not any studies demonstrating the superiority of one particular surgical intervention and there is no support for adding a fusion to a routine discectomy. (11,27,28)

The VAX-D Therapeutic Table

The VAX-D therapeutic table (Vertebral Axial Decompression) addresses the functional and mechanical aspects of discogenic pain and disease. The table was invented by Dr. Allan Dyer, former Deputy Minister of Health from Ontario and a pioneer in the development of the external cardiac defibrillator.

The table is designed to apply distraction tension to the patients lumbar spine without eliciting reflex paravertebral muscle contractions. The patient lies in a prone position, the upper body is over the stationary portion of the table, and the body is restrained by the patient holding on to adjustable handgrips which can be released at anytime for safety.

The table is a split table design, whereby distraction tensions are applied to the patient through a pelvic harness attached to a tensionometer and by separation of the movable part of the table. The distraction-relaxation cycles are automated or variably timed.

Distraction tensions and rates are continuously monitored and measured by the tensionometer and the output is shown on a digital gauge and captured on a pen-write printout. The table exerts its effects through decompression of the intervertebral discs.

Dr.'s G. Ramos and W. Martin of the Departments of Neurosurgery and Radiology at the HCA Rio Grande Regional Hospital, McAllen, Texas studied intradiscal pressure during VAX-D therapy.(30)

The patient population was comprised of individuals with unresolved low back pain who were referred for neurosurgical consultation. Previous management programs included conventional bedrest, medications, physical therapy, and or chiropractic treatments.

Depending on the diagnosis and findings of the examinations, patients were assigned to one of the following study groups: Intradiscal Pressure Study and Clinical Outcome Assessment Study. Patients with a subligamentous herniation at L4-5 who were candidates for percutaneous discectomy were included in a study of intradiscal pressure manometry. The pressure measurements were recorded by two different methods; an Ohmeda pressure transducer connected to a Hewlett Packer pressure monitor via a saline bridge and a Camino fiberoptic intracranial transducer adapted for intradiscal measurements. Both transducers were recalibrated after each procedure utilizing a Pneumatic Calibration Analyzer.

The transducers were placed in the L4-5 disc under A-P and lateral fluoroscopy. With the catheter in place the patient was placed prone on the VAX-D table. Various decompression tensions from 50 to 100 pounds were applied. The distraction tensions and the resulting changes in intradiscal pressure were observed on digital readout and recorded on a graph tracing produced by the chart recorder.

Intradiscal pressures were significantly reduced to minus 150-160 mm Hg. It was observed that a threshold distraction tension was necessary to develop negative pressures in the disc. The extent of decompression measured in mmHg follows an inverse relationship to the tensions applied.

The significance of this study cannot be overemphasized. The reduction of intradiscal pressure to negative levels has far reaching therapeutic implications. Prior to the introduction of VAX-D, a non surgical method for disc decompression was unavailable. In numerous studies, conventional traction has never demonstrated a reduction of intradiscal pressure to negative ranges, on the contrary many traction devices actually increased intradiscal pressure most likely secondary to reflex muscle spasm .(5)

Indications and General use of the VAX-D Therapy Table

VAX-D is indicated for patients with low back pain that has been unresponsive to conventional therapy for 6-8 weeks. Patients with radiculopathies are also candidates. The presence of a neurological deficit does not affect patient eligibility since studies have revealed the outcome in patients with neurological deficits was not affected by surgical or medical management.(15) The presence of a rapidly progressive neurological deficit is an indication for surgery. Patients presenting with a fusion and the post surgical failed back syndrome may also be candidates.

Contraindications for VAX-D therapy include infection, neoplasm, osteoporosis, bilateral pars defect or Grade 2 spondylolysthesis if unstable, fractures, the presence of surgical hardware in the spine, and the cauda equina syndrome. Patients with lateral stenosis and central stenosis may respond if severe secondary changes are not present in the vertebra. The patient should be evaluated by a therapist or physician prior to initiating therapy and routine spine films are necessary to rule out any contraindications. A CT scan or MRI is not necessarily a prerequisite before therapy.

The daily therapy sessions are administered by a trained VAX-D technician. All VAX-D technicians are encouraged to complete a certification exam. Treatments are administered on a daily basis for approximately twenty sessions and are routinely given Monday through Friday. An occasional patient may require a short maintenance period where 2 to 3 treatments a week are given for 2 to 4 weeks post therapy. The average patient has required 20-25 sessions. Each session is comprised of 15 cycles, each cycle being 1 minute in distraction and 1 minute in relaxation.

The table is designed to be operator friendly. With the patient standing, a specially made pelvic harness is fitted and tightened on the patient. The patient: lies prone on the table with the lower portion of the belt placed at the level of the table separation point. The adjustable handgrips are positioned such that the elbows remain straight. Repositioning and tightening of the pelvic harness is completed at this point. The harness is attached to a movable pretension housing that maintains a baseline tension of 20 lbs. throughout the rest phase. Once the pretension is set the treatment cycles may begin. The Ramos study indicated that 50 lbs. of tension was the threshold tension necessary to develop negative intradiscal pressures. The p.s.i. is slowly increased until tensions of 60-80 lbs. are developed, this may take 3 to 4 days of therapy. Some patients have required 90-100 lbs. of tension for a full therapeutic effect.

Pain distribution frequently changes during or immediately after therapy. A phenomenon called centralization first observed by McKenzie (24) has been noticed during a course of VAX-D therapy. Centralization is the process by which the pain pattern migrates from a peripheral distribution to a more central or proximal location and is an indication of a favorable clinical outcome. Centralization of pain patterns may be associated with increased central back pain, but this should be interpreted as a positive sign and is likely secondary to stretching of the posterior longitudinal ligament as the lateral distortion of the disc retracts to a more concentric position. Centralization is a predictable prognostic indicator for symptomatic discs and anular competence (12) The observed occurrence of centralization during VAX-D therapy in a patient who initially could not centralize their pain pattern implies healing of the anulus as a result of VAX-D therapy.

As higher distraction tensions are reached few patients may report an increase in pain of a different quality. Overstretching of the soft tissues in the back likely represents the cause of this pain and the patient should be treated by decreased distraction tensions, so as not to traumatize the soft tissues.

The development of a sharp, burning, radiating pain during therapy could represent the stretching of an entrapped nerve. Since the breakdown of scar tissue is an objective, the patient should continue but distraction tensions should be reduced such that any pain elicited does not last more than 15-20 minutes post therapy. Distraction forces are then slowly increased over the ensuing days.

No serious side effects have been reported with VAX-D therapy. A limiting factor affecting the patient's tolerance to therapy is stress to the shoulder girdle and rotator cuff. This may be mitigated by placing a roll under the axilla of the affected side. Should a patient have discomfort from any cause, they may release the handgrips at any time. This adds an important safety factor to the treatment.

Mechanism of Action

An understanding of spinal biomechanics is necessary to appreciate VAX-D's mechanism of action, to effectively treat and diagnose spinal disorders, and to objectively review old and new therapies.

The literature is replete with biomechanical data. Vogel and Stahl have carried out in vitro experiments on intradiscal movements with symmetrical and asymmetrical loading. (21) With symmetrical loading the nucleus expands and is retained by the anulus. By contrast, if the disc is subjected to an asymmetrical load, the nucleus migrates to the area of least load or resistance.(38) With removal of the load the nucleus moves from an eccentric to a more concentric position within the disc. Relocation can be accelerated by compression in the opposite direction or by distraction. (21) The anulus of a normal disc can restrain the nuclear movement, but when the elastic properties of the anulus are compromised the structures become susceptible to injury. Fissures and ruptures develop which allow the nucleus to migrate.

Fissures are normally present by 30-35 years of age and increase with advancing age. Fragment sequestra appear as a result of age and trauma. These fragments can move independently and result in protrusions and disc prolapses. Migration of nuclear material and sequestra is influenced by compressive forces, shearing, and increased intradiscal pressure. (24)

Epidemiological data and scientific data have demonstrated that prolonged or repetitive flexion loads stress the posterior anulus resulting in discogenic pain and in some patients disc herniation.(3,25) Adams and Hutton carried out experiments with gradual loading of the disc and concluded that disc prolapses can occur with a sustained flexion load.(2) Hickey and Hukins performed experiments with bending and torsion and demonstrated that the anulus failed posteriorly. (17) Shirtzi-Adl demonstrated that disc fiber layers are most loaded in flexion and least in extension. (40) Nachemson's research on intradiscal pressures showed pressures were highest with flexion. (26) The outer third of the anulus is innervated by the sinuvertebral nerve. Any asymmetrical load associated with elevated intradiscal pressure can result in overstretching and fatigue of the anulus, thereby stimulating the mechanoreceptors in the outer third of the annular wall. Eventually fissure's will develop in the anulus which can lead to herniation of the central mass of the nucleus. By reducing intradiscal pressure with VAX-D therapy, a therapeutic and prophylactic effect can be realized.

Numerous studies utilizing discography have helped us to understand the role of the disc as a pain generator. Provocational discography is the standard test for discogenic pain.(41) Its reliability has been questioned and opponents generally refer to the work of Holt, but his study has been refuted on methodological grounds.(9,18,41)

Recently a pathological marker of symptomatic disc disruption called the high intensity zone (HIZ) was demonstrated on MRI using spin echo gradient heavy T2 imaging. (6,38) An HIZ is evident in the posterolateral view on the sagittal section, which on provocation discography corresponded to a Grade 3 radial tear. The high signal intensity represents fluid within the fissure that may be causing pain either by chemical irritation or mechanical traction of the sinuvertebral nerve. By its cyclic action and ability to reduce intranegative pressure, VAX-D therapy could displace the fluid to the internal portion of the nucleus thereby ameliorating pain and enhancing healing of the anulus.

Donelson demonstrated it is possible to predict anular competence with the McKenzie mechanical assessment protocol.(12) In his study patients were separated into centralizer's and non centralizer's. Discography was performed in both groups. Centralizer's tended to have an intact anulus or Grade 1-2 tears. Non centralizer's had a disrupted anulus , that is fissures to the outer third of the anular wall or Grade 3 tear. This is very exciting news for those who appreciate the centralization phenomenon because it allows us to clinically assess the competency of the anulus. Patients who centralize on initial evaluation may be treated with specific exercise. Patients who do not centralize on initial examination are excellent candidates for VAX-D therapy. With such an approach, the patients disposition regarding effective therapy is known immediately, which arguably translates to reduced disability and reduced cost.

VAX-D therapy has been shown to convert non centralizer's to centralizer's during or after successful VAX-D therapy. This implies VAX-D is condusive to anular healing.

Asymmetrical loading of the disc and increased intradiscal pressure is partly responsible for internal derangement, discdegeneration and herniation. Changes in intradiscal pressure also play a prominent role in affecting nourishment of the disc since the disc is an avascular structure and receives its nourishment primarily by diffusion.

Intradiscal pressure that is greater than capillary pressure in the vertebral body impedes oxygen diffusion to the disc which in turn impedes healing.(13) Reducing intradiscal pressure with VAX-D creates a diffusion gradient into the disc allowing nourishment to proceed. Solutes such as oxygen have a steep concentration gradient across the disc, with the peripheral concentration 20-30 times more than the concentration at the center of the nucleus. The availability of oxygen may be inadequate to meet the metabolic requirements required to heal a damaged anulus, and higher concentrations of lactate have been measured within the central portion of the disc, By reducing intradiscal pressure, VAX-D therapy creates a diffusion gradient thereby enhancing solute transfer. High levels of lactate could facilitate chondrocyte cell death as well as increase the activity of degradative enzymes further promoting the loss of the proteoglycan cell matrix. A vicious cycle is produced, accelerating disc degeneration.

The mechanical effects of fluid loss during a compressive load are followed by a slow rate of disc deformation termed creep. The rate of creep is faster in a damaged or degenerated disc than a normal disc. Both vibration (overstress) and inactivity (understress) affect the rate of creep and disc degeneration. Pigs who were subjected to vibratory creep had lower levels of oxygen and sulfate transport, and higher levels of lactate within the disc. (13)

Somewhere between the overstress of vibration and the understress resulting from inactivity is an optimum mechanical environment. Through its action, VAX-D may be capable of restoring that environment, enhancing healing of the disc and retarding degeneration.

The pathophysiology of nerve root compression has been described by Rydevik. (33,34,35) The nerve root ganglion has an extensive venous plexus, which if obstructed, results in venous hypertension and endoneural edema, leading to hypoxia, ischemia and pain. External decompression with VAX-D therapy can be expected to relieve venous hypertension and reverse the pathognomonic process.

By significantly reducing intradiscal pressure, VAX-D promotes retraction of the herniation into the disc. VAX-D therapy could possibly shear a herniation from its connection to the central nucleus, creating a severed fragment within the spinal canal. This sequestered disc is susceptible to small vessel invasion and digestion as a result of contact with the epidural space. Reinforcing this theme is the study by Modic et al who studied the natural history of disc herniation by MRI in patients with acute radiculopathy and discovered that large (6 mm ) sequestered hernias were the first undergo spontaneous resolution.(23)

I have studied sensory nerve dysfunction measured before and after VAX-D therapy, in order to determine the effect of VAX-D on nerve root compression. The results from this study are very significant and the data will be published in the future.

Inflammation very likely plays a role in disc pathology and herniation but the response to anti-inflammatories is rather disappointing. Saal found high levels of Phospholipase A2 in human disc samples removed at surgery in patients with radiculopathy.(36) As the enzyme responsible for liberation of arachidonic acid from cell membranes, Phospholipase A2 is the rate limiting step in the production of prostaglandin's and leukotrienes. Controlled studies have shown that anti-inflammatories are not useful for acute sciatica,(46) but since solute transfer to the disc may be enhanced by VAX-D therapy, the administration of anti-inflammatories during VAX-D therapy may result in higher concentrations of the drug within the disc, neutralizing inflammatory mediators responsible for nerve root inflammation and some forms of discogenic pain. As previously mentioned the fluid within the HIZ is thought to be an inflammatory fluid and VAX-D may be able to effectively pump this fluid into the central nucleus where it is not possible for it to exert an inflammatory effect. The fissure may be able to approximate its borders and heal once the fluid is pumped out.

VAX-D vs. Traction

The VAX-D table is an external decompression device and this separates it from conventional traction. Studies verifying decompression of the disc and nerve root are now available for VAX-D. I reviewed the literature and I could not find any available data that conventional traction reduced intradiscal pressure to the negative range nor are there any studies on conventional traction showing beneficial effects in nerve root compression and conditions associated with discogenic dysfunction.

Many patients who receive VAX-D therapy have had chronic back pain and failed numerous modalities including traction. Their positive response to VAX-D therapy, after having failed conventional therapy and traction confirms VAX-D's assertion that it is not conventional traction.

Clinical Studies

The Acute Low Back Distress Study was conducted by the John P. Robarts Research Institute, London Ontario. The efficacy of VAX-D therapy was established with this study. The parameters measured were severity and duration of pain and disability, including analgesic requirements, and the presence and degree of neurological involvement. One hundred and ten patients were entered into the study.

The treatment was considered a success if the baseline aggregate score for pain and disability was reduced by 50% after 10 treatments of VAX-D therapy. Sixty-six percent of the patients achieved success according to the study protocol. Prior to therapy the aggregate score for pain and disability was 5.1 and after 10 treatment sessions in the successful group it was 1.2.

The Clinical Outcome Assessment Study was conducted at McAllen HCA Hospital by Dr. G Ramos.(31) Fifty-two patients completed VAX-D therapy as the primary modality. Thirty-eight patients (73%) achieved a positive outcome with remission of their low back pain symptoms and a return to functional levels of activity. Ninety percent of the recovered group were suffering from disc herniations, the majority (89%) being subligamentous while 11% had extruded herniations. Neurological deficits did not compromise the response to therapy.

Review of the patients clinical findings for those who achieved remission showed that 33% exhibited neurological deficits and 73% had sciatic pain prior to therapy with VAX-D.

Dr. E. Gose, Dr. W Naguszewski, and Dr. R Naguszewski have completed an outcome study of VAX-D therapy from over twenty medical centers that included over 700 patients. Patients with back pain, with or without leg pain were included in the study as well as the failed surgical back patient. All patients had a diagnosis of a herniated disc, degenerative disc or facet syndrome. The authors are very enthusiastic about the outcome and have prepared a detailed report of their findings which been accepted for publication in another respected medical journal.

An outcome study at Columbia hospital, Tulsa OK. is currently being conducted that shows a level of success consistent with the above study.

Summary

VAX-D therapy addresses the biomechanical aspects of discogenic disease and achieves its objective through decompression. It should be utilized in patients with low back pain, with or without radiculopathy who have failed conventional therapy (physiotherapy and chiropractic), and should be utilized prior to addressing surgery. By addressing the altered biomechanics responsible for disc disease, the VAX-D therapeutic table not only alleviates pain but has been shown to exert a beneficial effect on a major determinant in the equation responsible for discogenic disease, that is elevated intradiscal pressure.

Further analysis of future and unpublished research should be considered to further validate the therapeutic benefit of VAX-D therapy, however, these clinical studies have shown it to be effective in back pain syndromes with or without radiculopathy including herniated discs and internal disc disruption.

The chronic back pain patients and surgical patients are very costly to society. Since many of these patients are responsive to VAX-D therapy, this unique non-obtrusive means of managing the common forms of debilitating low back pain associated with discogenic disease could represent a considerable savings.

About the author
Dr. Frank Tilaro is a board certified internist who has been practicing orthopaedic medicine for the last 12 years. Dr. Tilaro has restricted his practice to orthopaedic medicine. He is a member of the American Back Society, the McKenzie Institute, the American Association of Orthopaedic Medicine and the British Institute of Musculoskeletal Medicine. Dr. Tilaro is medical director for The Advanced Spinal Institute in Ogden Utah and director of education and clinical research for VAX-D Medical Technologies, Palm Harbor, Florida. Dr. Tilaro resides in Ogden, Utah and can be reached at 1-801-698-0270 or 1-800-558-8293.

References

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2. Adams A, Hutton WC. Gradual disc prolapse. Spine 1985; 10:524-31.
3. Adams M, Green T, Dolan P. The strength in anterior bending of lumbar intervertebral discs. Spine 1994; 19:2197-2203
4. Akeson WH, Murphy RW. Low back pain. Clin Ortho 1977; 129:2-3.
5. Andersson GB, Schults AS, Nachemson AL. Intervertebral disc pressures during traction. Scand J Rehabil Med 1983; 9:88-91.
6. Aprille C, Bogduk N. High intensity zone: a diagnostic sign of painful lumbar discs on magnetic resonance imaging. The British Journal of Radiology 1992; 65:361-369.
7. Bloch R, 7. Bloch R, Davis DO, Dina TS. Methodology in clinical back pain trials. Spine 1987; 12(5): 430-08.
8. Boden SD, Patronas NJ, Weisel SW. Abnormal magnetic resonance scans of the lumbar spine in asymptomatic subjects: a prospective investigation. J Bone Joint Surg {Am} 1990. 72:403-08.
9. Bogduk N, Modic MT. Controversy: lumbar discography. Spine 1996.21:402-04.
10. Bush K, Cown N, Katz DE, Gishen P. The natural history of sciatica associated with disc pathology. A prospective study with clinical and independent radiologic follow-up. Spine 1992; 17(10):1205-12.
11. Deyo RA, Cherkin DC, Loeser JD, Bigos SJ, Ciol MA. Morbidity and mortality in association with operations on the lumbar spine, The influence of age, diagnosis, and procedure. J Bone Joint Surg {AM} 1992; 74 (4):536-43.
12. Donelson R, Aprille C, Medcalf R, Grant W. A prospective study of centralization of lumbar and referred pain. A predictor of symptomatic discs and annular competence. Spine 1997; 22(10):1115-1122.
13. Frymoyer JW. The adult spine. Principles and practice. Raven Press, New York 1991.
14. Gray ICM, Main CJ, Waddell G. Psychological assessment in general orthopaedic practice. Clin Orthop 1985; 194:258-63.
15. Hakelius A. Prognosis in sciatica. Acta Orthop Scand (suppl) 1970. 129:1-76.
16. Herron LD, Turner T. Patient selection for lumbar laminectomy and discectomy with a revised objective rating. Clin Orthop 185; 199:145-52.
17. Hickey D, Hukins D. Relation between the structure of the annulus fibrosis and the function and failure of the intervertebral disc. Spine 1985; 5:106-114.
18. Holt EP. The question of lumbar discography. J Bone Joint Surg 1968; 50A:720-5.
19. Jensen MC, Brant-Zawadski, Obuchowski N, Modic MT, Malksalan D, Ross JS. Magnetic resonance imaging of the lumbar spine in people without back pain. N Engl JMed 1994.331:69-73.
20. Komberg M. Discography and magnetic resonance imaging in the diagnosis of lumbar disc disruption. Spine 1988; 14:908-18.
21. Kramer J. Intervertebral disk diseases. Causes, diagnosis, treatment and prophylaxis. George Theime Verlag Stuttgart, New York, 1990.
22. Kramer J. Presidential address: natural course and prognosis of intervertebral disc diseases. Spine 1995; 20(6):635-39.
23. Modic M, Ross J, Obuchowski N, Browing K, Cianflocco AJ, Mazanac D. Contrast enhanced magnetic resonance imaging in acute lumbar radiculopathy: a pilot study of the natural history. Radiology 1995. 195(2):429-35.
24. McKenzie RA. The lumbar spine: Mechanical diagnosis and therapy. Waikane, New Zealand: Spinal Publications, 1981.
25. McNally DS, Adams MA, Goodship AE. Can intervertebral disc prolapse be predicted by disc mechanics. Spine 1993. 18:1525-1530.
26. Nachemson AL. The influence of spinal movements on the lumbar intradiscal pressure and on the tensile stresses in the annulus fibrosis. Acta Ortho Scand. 1963; 33:183.
27. Nachemson AL. Fusion for low back pain and sciatica. Acta Orthop Scand 1985; 56(4):285-86.
28. Nachemson AL. Lumbar disc herniation-conclusions. Acta Orthop Scand (Suppl 251)1993;64.
29. North RB, Campbell JN, James CS, Conover-Walker, Wang H, Paintadosi S, Rybock JD, Long DM. Failed back surgery syndrome: 5-year follow up in 102 patients undergoing repeated operation. Neurosurgery 1991; 28(5):685-91.
30. Ramos G, Martin W. Effects of vertebral axial decompression on intradiscal pressure, JNeurosurg 1994; 81:350-353.
31. Ramos G. Personal communication.
32. Revel M Payan C, Vallee C, Laredo JD, Lassae B, Roux C, Carter Salomon C. Delmas E, Roucoules J, Beauvais C, Savy JM Chiecheportiche V, Bourgeois P, Smadja M, Hercot O, Wybier M, Cagan GM, Blum-Boisgard C, Fermanian J. Automated percutaneous discectomy versus chemonucleolysis in the treatment of sciatica. A randomized multicenter trial. Spine 1993; 18(1):1-7.
33. Rydevik B, Brown MD, Llundborg G. Pathoanatomy and pathophysiology of nerve root compression. Spine 1984; 9:7-15.
34. Rydevik B, Myers R, Powell HC. Pressure increase in dorsal root ganglion following mechanical compression. Closed compartment syndrome in nerve roots. Spine 1989; 14:574-76.
35. Rydevik B, Holms S, Brown NM. Nutrition of spinal nerve root. Trans Orthop Res Soc 1984; 9:276.
36. Saal JS, Franson R, Dobrow R, Saal JA, White A, Goldwaite N. High levels of inflammatory phospholipase A2 activity in lumbar disc herniations. Spine 1990; 15(7):674-78.
37. Saal JA, Saal JS, Herzog R. The natural history of lumbar intervertebral disc extrusions treated non operatively. Spine 1990; 15(7):683-86.
38. Schellhas K, Pollei SS, Gundry C, Heithoff K, Lumbar disc high-intensity zone. Correlation of magnetic resonance imaging and discography. Spine 1996; 21:79-86.
39. Schnebel B. Simmons J, Chowing J, Davidson R. A digitizing technique for the study of movements of intradiscal dye in response to flexion and extension of the lumbar spine. Spine 1988; 13:309-12.
40. Shiratzi-Adl A. Biomechanics of the lumbar spine in sagittal /lateral moments. Spine 1994; 19:2407-12.
41. Simmons JW, Aprille CN, Dwyer AP, Brodsky AE. A reassessment of Holt's data on the "question of discography." Clin Orthop 1988; 237:120-4.
42. Spengler D, Bigos S, Martin N, Seh J, Fisher L, Nachemson A. Back injuries in industry: A retrospective study. Overview and cost analysis. Spine 1986; 11:241-45.
43. Spitzer WO, Leblanc FE, Dupuis M. Scientific approach to the assessment and management of activity-related spinal disorders. Spine 1987; 12:7S.
44. Turner JA, Ersek M, Herron L, Deyo R. Surgery for lumbar spinal stenosis, attempted meta-analysis of the literature. Spine 1992; 17(1): 1-8.
45. Vanharanta H, Sachs BJ, Spivey MA, Guyer RD, Hochshuler SH, Rashbaum RF, Johnson RG, Ohnmeiss D, Mooney V. The relationship of pain provocation to lumbar disc deterioration as seen by CT/discography. Spine 1987; 12(3):295-98.
46. Weber H, Holme I, Amlie E. The natural course of acute sciatica, With nerve root symptoms in a double blind placebo controlled trial evaluating the effect of piroxicam (NSAID). Spine 1993; 18:1433-8.
47. Weber H. Spine update. The natural history of disc herniation and the influence of intervention. Spine 1994. 19(19):2234-38.
48. Weisel SW, Tsourmas, Fefer HL, Citrin CM, Patronas N. A study of computer assisted tomography: The incidence of positive CAT scans in an asymptomatic population. Spine 9:549-51.
49. Zuckerman J, Derby R, Hsu K et al. Normal magnetic imaging with abnormal discography. Spine 1988; 13:1355-9.

This article is reprinted with the permission of the authors from the Journal of Neurosurgery, Volume 81.

J Neurosurg 81:350-353, 1994

Effects of vertebral axial decompression on intradiscal pressure

GUSTAVO RAMOS, M.D., AND WILLIAM MARTIN, M.D.

Departments of Neurosurgery and Radiology, Rio Grande Regional Hospital, McAllen, and Division of Neurosurgery, Health Sciences Center University of Texas, San Antonio, Texas

The object of this study was to examine the effect of vertebral axial decompression on pressure in the nucleus pulposus of lumbar discs. Intradiscal pressure measurement was performed by connecting a cannula inserted into the patient's L4-5 disc space to a pressure transducer. The patient was placed in a prone position on a VAX-D therapeutic table and the tensionometer on the table was attached via a pelvic harness. Changes in intradiscal pressure were recorded at resting state and while controlled tension was applied by the equipment to the pelvic harness. Intradiscal pressure demonstrated an inverse relationship to the tension applied. Tension in the upper range was observed to decompress the nucleus pulposus significantly, to below -100 mm Hg.

SURGICAL procedures utilizing conventional and percutaneous approaches have established the merits of decompression of intravertebral disc spaces in the management of low-back pain syndrome associated with lumbar disc herniation.4,12,13,15 Surgery will continue to play an important role in the treatment of patients with low-back pain and sciatica associated with herniated discs and degenerative disc problems. However, for patients who are not candidates for surgery, there is a need to establish a conservative approach that offers an effective means of returning the patient to a functional level of activity.

Considerable controversy exists in regard to the various techniques currently employed. Aside from basic bed rest, there are few noninterventional modalities that have been adopted as standards of therapy. Manipulative techniques for mechanical low-back pain associated with posterior facet syndrome or muscle strain have not been found as useful in the management of herniated or degenerated lumbar discs. Similarly, other modalities including ultrasound treatments, various electrical stimulation techniques, short-wave therapy, acupuncture, steroid injections, and the administration of anti-inflammatory agents and muscle relaxants all have a following among some practitioners but fall short of addressing the underlying problems associated with intervertebral disc lesions. All of these treatment methods fail by comparison to surgery, in our opinion, because they have the common problem of not relieving the pain from neurocompression or from the stimuli associated with a prolapsed nucleus pulposus. The only noninterventional method that has been shown to hold any promise of relieving pressure on vital structures of the lumbar region is that of distraction of the lumbar vertebrae by mechanical forces applied along the axis of the spinal column.2,3,5,14

There has been some investigation into the effects of distracting segments of the spinal column excised from cadavers,11,14 as well as radiological studies that provided evidence that the application of certain forms of tension can distract vertebral bodies.3,5 On the other hand, there are equally pertinent studies that failed to demonstrate any positive effects from other methods of applying spinal tractions.1,10 Nachemson and Elfstrom6-9 have studied the effects of movement and posture on intradiscal pressure. Their measurements show pressure changes caused by positioning and posture range between 25 and 275 mm Hg, suggesting that some positions and postures may be inadvisable for patients suffering from lumbar disc lesions. Anderson, et al.,1 and others have shown that certain traction techniques can actually cause an increase in intradiscal pressure, which would be undesirable in the treatment of low-back pain associated with herniated discs and a neurocompression etiology.

A new form of therapy, termed "vertebral axial decompression," has recently been introduced in the physical therapy department of the Rio Grande Regional Hospital. This treatment modality has shown considerable promise in relieving low-back pain associated with herniated discs or degenerative disc disease of the lumbar vertebrae in patients who are not considered candidates for surgery. The purpose of this research project was to investigate the influence of this new treatment modality on intradiscal pressure in the lumbar spine of patients receiving this form of therapy.

Fig. 1. Photograph illustrating the equipment and the position of the patient as the system is activated. The caudal end of the table extends, applying tension to the pelvic belt. Upper body movement is restrained by having the patient grasp the hand grips. A graph of the tension applied is plotted by a chart recorder on the control console and the intradiscal pressure readings are entered on the same graph at the apex of each distraction curve.

Clinical Material and Methods

Five cases were selected from among individuals who were referred for a neurosurgical consultation and had previously sustained a work-related injury that resulted in herniation of a lumbar disc at one or more levels. The diagnosis in each case was confirmed by magnetic resonance imaging. The patients chosen were scheduled for percutaneous discectomy. Introduction of the cannula for the purpose of performing percutaneous discectomy offered an opportunity to measure pressure changes in the disc prior to the operative procedure.

The patient was prepared and a cannula was inserted under local anesthesia into the nucleus pulposus of the L4-5 intervertebral disc using anteroposterior and lateral fluoroscopy to position the end. With the cannula in place, the patient was moved to a VAX-D table. The VAX-D equipment is routinely utilized in our nonsurgical treatment program for patients suffering from low-back pain. The equipment consists of a split table design with a tensionometer mounted on the caudal, moveable section. The patient lies in a prone position and grasps hand grips to restrain movement of the upper body, which is supported on the fixed section of the table (Fig. 1).

The cannula was then connected to a pressure monitor using a disposable pressure transducer. The lines were filled with normal saline. The pelvic harness designed for this therapy was fastened around the pelvic girdle and connected to the tensionometer via straps attached to the harness. When the system was activated the caudal section supporting the lower body extended slowly, applying a distraction force via the pelvic harness connected to the tensionometer. The level of tension was preset by the operator on the control console and observed and plotted on a chart recorder. The movement of the table was stopped and held when the desired tension was reached. An average course of therapy consisted of 30-minute sessions on the table once a day for 10 to 15 days. During each session the patient undergoes alternating cycles of distraction and relaxation, the timing and periodicity having been programed by the therapist.

In this study various distraction tensions, ranging from 50 to 100 Ibs, were used for vertebral axial decompression therapy. The distraction tensions applied were monitored on a digital readout and recorded on a continuous graph tracing by a chart printer incorporated in the control console. The resulting changes in intradiscal pressure in the L4-5 nucleus pulposus were observed on a digital readout on the pressure monitor, and the readings were entered onto the chart recording at the point when the apex of distraction tension was achieved. The pressure readings were then applied to the negative-range calibrated curves prepared for each transducer to derive accurate intradiscal pressure readings.

*See Fig. 2 for graphs of data points.
Measurements in the first two patients could not be translated accurately and are omitted (see text).

Fig. 2 Graphs showing the intradiscal pressures recorded in the L4-5 nucleus pulposus of three patients (Case 3, upper; Case 4, center; and Case 5, lower) with a herniated disc at this level. Pressure is plotted against distraction tension consistent with the range of tension recommended as the therapeutic protocol for the equipment used in this study.

The biological transducers employed in this study are primarily designed to measure pressure changes in the positive range. Following each procedure the presssure monitor and the disposable pressure transducer used for each patient were individually calibrated and a correction curve was plotted showing the transducer readings versus actual pressures, to correct for the nonlinearity of the instrumentation in the range of negative pressures achieved. A pneumatic calibration analyzer with an accuracy of 2% was used for this purpose.

Results

Intradiscal pressure measurements showed that distraction tension routinely applied by the VAX-D equipment reduced the intradiscal pressure significantly to negative levels in the range of -100 to -160 mm Hg. The relationship between distraction tensions and intradiscal pressure changes for three patients is presented in Table 1. The extent of decompression (measured in mm Hg) shows an inverse relationship to the tension applied and may be expressed by a polynomial equation.

Discussion

Intradiscal pressure changes were monitored in five patients. When the first two patients were tested, it was not recognized that biological transducers produce nonlinear measurements in the negative ranges at the levels achieved in this study. Since the disposable units had been discarded it was not possible to translate the findings accurately: however the intradiscal pressures were observed to be significantly lowered. Also the findings were consistent with the later three patients, for whom the transducers were retained and individually calibrated, permitting accurate interpretation of the results.

An interesting observation was that changes in intradiscal pressure appeared to be minimal until a threshold distraction tension was reached. When the threshold was exceeded the intradiscal pressure was observed to decrease dramatically to levels in excess of 300 mm Hg below the positive pressure observed prior to the application of pelvic tension. As indicated in the curves plotted for intradiscal pressures versus distraction tension, it appeared that the decrease in pressure tends to level off as the applied distraction tensions approached 100 Ibs. The concept of a threshold distraction tension and the levels observed in these trials are consistent with radiographic studies of vertebral body separation reported in other publications.2

The results indicate that it is possible to lower pressure in the nucleus pulposus of herniated lumbar discs to levels significantly below 0 mm Hg when distraction tension is applied according to the protocol described for vertebral axial decompression therapy. These findings may offer a plausible explanation for the mechanism of action for this therapeutic modality. Future research is warranted to study the decompression phenomenon achieved with this technology and its relationship to clinical outcome in patients with anatomical dysfunction of the lumbar spine. We are preparing a follow-up study on the clinical efficacy of this treatment modality.

Acknowledgments

The authors gratefully acknowledge the director and staff of the Department of Physical Therapy for their assistance in administering the vertebral axial decompression therapy.

Disclosure

The authors have no financial interest in either the equipment or the methodology advanced in this study.

References

1. Anderson GBI, Schultz AB, Nachemson AL: Intravertebral disc pressures during traction. Scand J Rehabil Suppl 9:88-91, 1983
2. Colachis SC Jr, Strohm BR: Effects of intermittent traction on separation of lumbar vertebrae. Arch Phys Med Rehabil 50:251-258, 1969
3. Gupta RC. Ramarao SV: Epidurography in reduction of lumbar disc prolapse by traction. Arch Phys Med Rehabil 59:322-327, 1978
4. Hirsch C. Nachemson A: Lyle reliability of lumbar disk surgery. Clin Orthop 29:189-195, 1963
5. Mathews JA: Dynamic discography: a study of lumbar traction. Ann Phys Med 9:275-279, 1968
6. Nachemson A: The load on lumbar disks in different positions of the body. Clin Orthop 45:107-122. 1966
7. Nachemson A:

VAX-D has been subjected to clinical trials at major hospitals in the United States and Canada, and has proven to be an effective treatment for lowback pain. VAX-D is applicable as a primary, active treatment modality for the management of most patients with disabling low-back pain and neurological deficits associated with herniated discs, degenerative disc problems and posterior facet syndrome.

The therapy combines a number of patented principles, which are administered via an automated and closely monitored system incorporated in the design of the VAX-D Therapeutic Table and Control console. This equipment is a Class II medical device registered originally in 1989 under the 510K No. K894435. The FDA registration has recently been updated as K951622 in response to a submission of the published article on intervertebral decompression. Please note under the section entitled "Intended use" in the updated FDA Summary of Safety and Effectiveness, reference is made to VAX-D achieving relief of low back and radicular pain through decompression of intervertebral discs.

Clinical research establishing the efficacy and safety were conducted at major hospitals in the U.S. and Canada. In these studies the patients were primarily Worker's Compensation cases who were referred to the Neurosurgical service of the respective hospitals following several months on conservative care without achieving significant progress.

The initial clinical trials, the 'Low Back Distress Study' was done at University Hospital, London. This was a study with subjective indices of pain and disability recorded daily along with analgesic use, Neurological dysfunction was assessed on a weekly basis. All the patients had a CT scan to confirm their diagnosis before starting treatment. The trials were conducted under the supervision of the Neurosurgical department.

Additional trials were carried out at the Departments of Neurosurgery and Radiology, Rio Grande Regional Hospital, McAllen, Texas. The patients were primarily Worker's Compensation cases who were referred to the Neurosurgical service following several months on conservative care, without achieving significant progress. In addition to replicating the basic results observed at University Hospital, significant research into the mechanism of action was also carried out.

These studies were conducted as a collaborative effort by the departments of Neurosurgery and Diagnostic imaging. The diagnosis, confirmed by MRI on all patients, was a herniated lumbar disc at one or more levels, often associated with additional complications such as degenerative changes and / or facet problems.

Clinical discomanometry research, in which intradiscal pressure changes were recorded during VAX-D Therapy, established that decompression (that is, unloading due to distraction and positioning of the patient on the VAX-D Table) of the intravertebral disc of the lumbar spine can be achieved with this equipment. The extent measured in mm. Hg. follows an inverse relationship to the tension applied to the pelvic belt during therapy. Resting positive pressure readings were observed to decrease to levels in the range of minus 150mm. Hg. in patients on VAX-D Therapy. An article on these clinical studies was published by Dr. G. Ramos, and Dr. W. Martin in the journal of Neurosurgery in September 1994.

To rule out artifact the investigators employed standard biological transducers and pressure monitoring equipment. Their paper also notes that they took the added precaution of individually calibrating the equipment employed in each case to make sure the negative pressure readings were accurate.

Furthermore it is important to note that the investigators were able to reproduce their results when distraction tensions were applied according to the VAX-D protocol.

The publication of this study was a first in the reported literature of this phenomenon and we feel has made an important contribution to the scientific knowledge regarding the clinical application of this technology. Equally important is the fact that the decreases recorded in the intradiscal pressures were well beyond physiological variations and therefore represented findings that could only have been attributed to the conditions of the clinical trial, that is treatment on the VAX-D table.

In addition to the definitive measurements, the study included a group of patients, referred for a neurosurgical consultation, who were treated with VAX-D Therapy. The incidence of patients that experienced a positive outcome, with relief of pain and distressing symptoms, following a course of 15 daily (half hour) sessions, was in the range of 65 to 70%. The data also notes that of the patients that achieved remission of symptoms, 90% suffered from a herniated lumbar disc. Diagnostic imaging confirmed that 89 % of the successfully treated hernias were classified as subligamentous, whereas 11% had extruded segments that had perforated the annular ligament.

Analysis of the clinical data showed that 70% of the successfully treated cases presented with sciatic pain. Similar results are reported from over 9O independant VAX-D Clinics throughout the United States, Canada and Puerto Rico.

A follow up of patients for up to 12 months at the trial centers, has not uncovered any unexpected level of relapse. However some have returned voluntarily for 'reduced frequency' sessions on the Table from time to time. Patients that require further therapy generally appear to be those with complicating factors such as degenerative disc changes, or stenosis.

VAX-D OUTCOME STUDY

Following two seperate FDA approvals (one for the device and one for the safety and efficacy of the treatment/decompression), 22 medical centers were asked to collect data on all patients who received VAX-D therapy for low back pain. The purpose of the study was to assess the efficacy of Vertebral Axial Decompression Therapy in the treatment of low back pain resulting from documented lumbar disc disease.

The patients ranged in age from 25 to 60 years at the treatment onset and they were followed from one to two years. All patients had failed proir attempts at treatment which included physical therapy, acupuncture, chiropractic care, epidural injections, and in some cases, surgical intervention. All patients had documented chronic back pain and pathology was found on MRI or radigraphic images. Use of a "double blind" type study was not practical as patients very early in the study would guess whether they were part of the "sham" group receiving only regular traction or part of the VAX-D therapy group. An earlier study in Canada designed to be"double blind" soon found that patients refused regular traction as they discerned or discovered that they "were not getting the better treatment".

The study was divided into five diagnostic groups which were comprised of patients with extruded herniated discs; multiple herniated discs without extrusion, with or without degenerative disc disease; single herniated disc, regardless of degenerative disease; degenerative disc disease. without herniation; and facet syndrome.

Each patient chose a subjective pain index ranging from 0 to 5 (5 being severe pain) and a disability index of 0 to 3 (3 being bedfast). Each was also assessed for objective signs of decreased mobility on a 0 to 3 scale (3 being completely immobile). They were assigned by diagnosis into one of the above five groups.

All patients received VAX-D Therapy of at least 10 sessions plus additional treatments if the patient continued to improve. Patient history, schedule, including frequency and intensity of therapy, was recorded along with patient symptoms and satisfaction with treatment. Measurements were made at the beginning, mid-point, and end of treatment.

If treatment success is defined as a reduction in pain to 0 or 1 on a 0 to 5 scale, the treatment was successful in 75% of the patients. The success rate varied from 67% for the patients with extruded herniated discs, to 77% for patients with degenerative disc disease or single herniated discs. It was 71% for people with multiple herniated discs and 70% for facet syndrome.

On a pain scale of 0 (none) to 5 (severe), the people with extruded herniated discs had an average pain of 4.19 at the beginning of treatment and an average of 1.33 after treatment, a reduction of 68%. The cases of multiple herniated discs went from 4.15 to 1.17, a reduction of 72%. The patients with a single herniation had a reduction from 4.14 to 1.08, or 74%. The degenerative disc cases went from 3.94 to 1.03, a 74% reduction. Those with facet syndrome went from 4.10 to 0.97, a 76% reduction in pain.

In summary, the data on mobility and ADL appear to correspond to pain results and it appears that approximately 20 treatments with VAX-D Therapy has been proven to be effective in about three-fourths of all patients who have any combination of these types of disc disease.

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