Abstract

Low back pain is one of the most significant medical and socioeconomic problems in modern society.
International guidelines call for evidence-based management for the pain and disability associated with
musculoskeletal disorders. The purpose of this randomised controlled trial is to address the question of
efficacy and appropriateness of VAX-D (Vertebral Axial Decompression) Therapy, a new technology that
has been shown in clinical research to create negative intradiscal pressures, and has been shown to be
effective in treating patients presenting with chronic low back pain (>3 months duration) with associated
leg pain. Successful outcome was defined as a 50% reduction in pain utilising a 10cm Visual Analogue
Pain Scale and an improvement in the level of functioning as measured by patient-nominated disability
ratings. Patients were randomly assigned to VAX-D or to TENS which was used as a control treatment or
placebo. The TENS treatment demonstrated a success rate of 0% while VAX-D demonstrated a success
rate of 68.4% (P<0.001). A statistically significant reduction in pain and improvement in functional
outcome was obtained in patients with chronic low back pain treated with VAX-D. (Neurol Res 2001;
23:780-784)

Introduction
Low back pain is a major cause of disability in today’s society. According to the National Health and
Medical Research Council (NHMRC), each year approximately 600,000 Australians present with low back
pain as a recent illness. Although a high percentage of patients with acute low back pain recover within
4-6 weeks, a significant number of patients suffer from recurrences. Von Korff has studied the natural
history and found that approximately 60% will have recurrences. (1) In a study of back pain in primary care,
Von Korff and Saunders found that 60% to 75% improve in the first month, 33% report intermittent or
persistent pain at year one, and 20% of patients describe substantial limitations at this time. (2)
Klenerman et al demonstrated that 7.3% of individuals with acute low back pain who had not recovered by
two months still reported high levels of pain and disability at twelve months after onset. (3) Chronic low
back pain is increasing faster than any other disability, and 5-7% of the population will report their back
problems as being a chronic illness. Fifty percent of work loss caused by back pain is accounted for by
duration of disability for longer than 4 weeks. In Australia chronic low back pain affects more than
1,900,000 individuals and costs Australia more than 10 billion dollars each year.

International guidelines call for evidence-based management for the pain and disability associated with
musculoskeletal disorders. Today's primary care practitioners have a comprehensive responsibility in the
management of their patient’s low back conditions, and they must be aware that recurrences after the
presenting episode are likely. The literature suggests that for those who have not recovered by two
months, management efforts should begin. (4)

Acute disc injury and discogenic pain is one of the primary processes leading to low back pain and
lumbar radiculopathy, although the pathophysiologic mechanisms are still not well understood. It is
believed that increases in disc pressures resulting from heavy lifting, vibrational and postural forces etc.
are important factors in the pathogenesis of low back pain. The effects of disc hydraulics in herniations or
protrusions may cause a mechanical deformation of the nerve roots and a compression-induced
impairment of the vasculature. In addition, it has been found that the biochemical properties of the nucleus
pulposus may induce a toxic or inflammatory reaction in the nerve root.

There have been many studies indicating that the disc and its associated pathology are identified as a
primary cause of low back pain and lumbar radiculopathy. Hirsch stimulated various lumbar tissues in
awake patients with the use of carefully placed needles. (5) Stimulation of the posterior portion of the
annulus produced low back pain in many individuals. Furthermore, he was able to eliminate the pain by the
injection of a minute volume of local anaesthetic into the annulus. Smythe and Wright placed nylon threads
into various lumbar tissues while performing lumbar spinal operations. (6) During the postoperative
period, they pulled on the threads and asked the patients to describe the location of any pain produced.
The annulus fibrosus was the most common site of low back pain, and the compressed nerve root was
responsible for sciatic pain. Tension placed on a normal nerve root resulted in no pain.

Falconer and associates published their observations made during exploration of the lumbar spine under
local anaesthesia. (7) Murphy reported similar results in his small series of surgical cases. (8) Both
authors concluded that the annulus and nerve root were the pain generating tissues. Wiberg in 1950,
operating on 200 patients using local anaesthesia of the skin and muscles only, reported that pain
emanated from the disc. (9) Kublisch operated on 193 patients using local anaesthesia and drew certain
conclusions about the likely origin of back and leg pain. (10) Sciatica could only be produced by
stimulation of a swollen, stretched, or compressed nerve root. Back pain was produced in the majority of
cases by stimulating the outer layer of annulus fibrosus and the posterior longitudinal ligament.

If the disc is a major source of low back pain then applying specific target therapy for the treatment of disc
pathology should improve patient outcomes. VAX-D is a primary, non-surgical treatment for the
management of patients with disabling low-back pain and neurological symptoms associated with
herniated and degenerative disc disease. Research has shown that the VAX-D table is a decompression
device that is capable of reducing intradiscal pressures to negative levels. (11)

Successful reduction of intradiscal pressures with VAX-D represents a technological advance that should
provide a means of addressing compressive disc pathology. Creating negative intradiscal pressure is
likely to affect both the biomechanical and biochemical causes of discogenic pain. Patients suffering from
discogenic pain and/or associated sciatic pain are seeking conservative treatment without the risks
associated with injections and surgical procedures.

VAX-D incorporates advanced technology that permits the application of distractive tensions without
eliciting reflex muscle guarding. Conventional traction devices have not demonstrated this ability or the
ability to reduce intradiscal pressures to negative levels. Studies published in the medical literature report
that intradiscal pressure either remains unchanged or increases during traction. (12) It has also been
demonstrated that paraspinal muscles are not able to fully relax during conventional traction.

The beneficial effects of VAX-D decompression in the relief of peripheral nerve dysfunction has been
previously reported in the literature, (13) and a multi-center outcome study reported that VAX-D treatment
was successful in 71% of the 778 cases studied. (14).

This study was designed to evaluate the effect of VAX-D on chronic low back pain.

Material and Methods

In association with Quintiles, the world's largest health care consultancy organisation for data analysis in
clinical trials, a protocol was developed and then approved by the Human Research Ethics Committee at
the University of Wollongong, New South Wales, Australia.

It was predetermined that the treatment would be considered a success if the patient attained a fifty
percent (50%) decrease in pain, numerically on the Visual Analogue Scale (VAS). Absolute changes in
pain score determined by VAS over time were analysed with repeated measures analysis of variance and
t-test. In addition, improvements in disability were recorded on a patient nominated disability rating. Any
level of improvement in disability was acceptable. The instruments for determination of these outcomes
were supplied by the National Musculoskeletal Initiative of Australia. The study itself was to be conducted
in the medical clinics of the VAX-D Spinal Institute and so to prevent bias in the data collection Quintiles
were engaged to collect and analyse the data. TENS was selected as an appropriate placebo treatment
as a means of establishing a plausible but (probably) ineffective control for an unblinded treatment.
 

Through advertisement in local papers forty-four patients with chronic low back pain greater than 3 months
in duration, with associated leg pain, and a confirmed disc protrusion or herniation on CT Scan or MRI
were selected and randomised into the two treatment methods, either VAX-D or TENS. The patients were
randomised in sequential order and treatments were determined by a predefined central randomisation
list.

The average duration of pain in the patient population was 7.3 years. The conditions for receiving either
treatment including travelling to and from the clinic and duration of therapy were designed to be the same
for both populations. Inclusion criteria for the study were: age 18-65 years; a minimum VAS score of 2;
candidates must live within 45 minutes of the clinic location; capable of thoroughly understanding the
information given and following protocol. All candidates signed an informed consent form.

Exclusion criteria were: osseous stenosis; unstable spine (bilateral pars defect or Spondylolisthesis of
Grade II or greater); spinal surgical implants; shoulder problems which prevent compliance with VAX-D
therapy; spinal pain due to tumor, infection, or inflammatory disease; pregnancy; and previous VAX-D
therapy.

Patients randomised to VAX-D were treated according to the manufacturer's protocol. Patients lie on the
split table device in a prone position. VAX-D utilises handgrips that the patient grasps with arms extended
above the head to stabilise (restrain) the shoulder girdle and upper body. This is thought to be the most
effective means of assuring that tensions applied to the pelvis are transmitted accurately along the linear
axis of the spinal column during the procedure. The fact that the patient may release at any time during the
treatment provides an important safety factor. A special harness designed to apply forces primarily to the
lateral pelvic alae is fitted and tightened around the patient. The pelvic harness is connected to a
tensionometer at the caudal end of the table. The function of the tensionometer is to provide constant
feedback to the programmed logic control and operating system. During the VAX-D session a continuous
chart recording is generated plotting the controlled time/energy progress of the entire procedure.

Tensions are applied to the lumbar spine in a cyclic fashion from the baseline tension up to the therapeutic
range of fifty to ninety-five pounds. Each treatment session is thirty minutes in length and is comprised of
fifteen cycles of decompression alternating with relaxation. Each decompression and relaxation phase
may be individually varied as suitable for the particular treatment parameters.

A chart recorder prints the time energy curve for each decompression-relaxation cycle. This affords the
technician a means of monitoring and adjusting the decompression process. Patients received VAX-D
therapy five times per week for four weeks and then once per week for four weeks in accordance with
protocol. All VAX-D treatments were administered by certified VAX-D technicians at four clinics in the
Sydney area.

Patients randomised to TENS therapy received treatment at one of the four clinics. Electrodes were
placed according to the manufacturer's protocol. Patients lay prone on a treatment table and received
TENS for thirty minutes daily for twenty days then once a week for four weeks. All patients receiving TENS
were monitored by a technician.

Neither group received any physical therapy modalities, epidural steroid injections or other treatments
during the trial. Both patient groups were allowed to take non-narcotic pain relievers and anti-inflammatory
medication if necessary.

A 10-cm Visual Analogue Scale (VAS) for pain and a four-point disability rating scale were used to
assess patient response. The level of pain on the VAS was recorded on a 10cm line marked at one end
‘No Pain’ and marked at the other end ‘The Worst Pain Imaginable’. The written instruction to the patient
was to ‘please place a mark on the line below to indicate your current level of pain’. The self-nominated
disability rating scale required patients to list the four activities that were most affected by their low back
pain. These were scored according to the following criteria: 1 = cannot do at all; 2 = can do but severely
limited; 3 = can do but slightly limited, 4 = can do without limitation.

Data was collected at the initiation of the study prior to randomization and at the end of the eight week
treatment period in a separate interview. Success was defined as (equal to or greater than) a 50%
improvement in the patient's pain and any improvement in their disability rating.

Patients were free to withdraw from the study on their own volition at anytime. The study treatment could be
terminated prematurely if any of the following events occurred: patient wished to terminate his/her
participation for whatever cause (two cases); the investigator judged it was in the best interest of the
patient to withdraw (zero cases); the patient was unable to comply with protocol (zero cases).

The efficacy-evaluable population used for statistical analysis of efficacy is comprised of all patients who
were randomised to study treatment, received at least 10 study treatments, had efficacy data recorded
after Baseline, and satisfied the inclusion/exclusion criteria.

The primary efficacy measure in this study was the proportion of successfully treated patients in each of
the treatment groups. The difference in proportions of successfully treated patients in each treatment
group was tabulated and compared using Fisher's Exact Test and 95% confidence limits.

Successfully treated patients were to be followed up at six months to determine whether the successful
outcome was sustained.

Results
Forty-four patients were enrolled into the study. Twenty-two were randomised to each of the treatment
groups. A summary of demographic characteristics for the 44 enrolled patients is presented in Table 1.

Two patients (4.5% of 44), Patient 029 and Patient 003, were regarded as having withdrawn/not
completed the study according to the protocol. Patient 029, randomised to TENS, withdrew due to not
wishing to continue and Patient 003, randomised to VAX-D, withdrew due to treatment no longer being
required. No patients were withdrawn by the investigator. Patients 018 and 034 both randomised to
VAX-D, did not comply with the study criteria and are therefore excluded from the efficacy-evaluable
population. They both had a baseline VAS score less than 2 but this error of inclusion was not picked up
until the completion of the trial. The efficacy-evaluable population therefore comprised of 40 patients: 19
patients randomised to VAX-D, 21 randomised to TENS.

A summary of the data collected at baseline and post-treatment in the efficacy-evaluable population is
presented in Table 2.

In the efficacy-evaluable population the proportion of successfully treated patients was 13 out of 19 patients (68.4%) for the VAX-D treatment group compared to zero out of 21 (0%) for the TENS treatment group. There was a high
statistically significant treatment group comparison p-value of <0.001. The 95% confidence interval for the
difference in proportions of successfully treated patients, comparing VAX-D with TENS was 47.5% to
89.3%.

In the VAX-D group all patients recorded some improvement in their pain levels whereas in the TENS
group 13/ 21 recorded an increase in pain.

At six-month follow-up, of the 13 successful cases, 2 have been lost to follow-up, 1 case suffered a
significant other injury and of the remaining 10, seven have shown sustained success (ie. they still meet
the criteria for successful outcome).

The results reported for the TENS group were less that that expected for a placebo control. The negative
outcomes may have been due to the fact that the TENS patients (and the VAX-D patients) had to travel to
and attend a medical clinic five days per week for four weeks, and one day per week for four weeks. This
fact that both treatment groups had to travel to, and attend the clinic, was necessary to ensure that the only
variable between the two groups was in the type of treatment that they received. The benefits of treatment
in the VAX-D group clearly outweighed the negative effects of travelling, which became evident in the
placebo group.

Discussion
Disc stresses coupled with ongoing increased intradiscal pressures from mechanical loading may lead to
failures in the normal biomechanics of the disc and progress to degeneration, posterior displacement of
the nuclear material, annular disruptions and herniations. Other causative factors in the course of disc
degeneration are negative diffusion gradients, reduction of the fluid content of the nucleus pulposus, and
abnormal disc metabolism. With positive disc pressures throughout the day that are above diastolic
pressure, the metabolism of the disc becomes anaerobic thus impeding the normal reparative healing
abilities.

Proteolytic enzymes (matrix metalloproteinases) reside in the disc and have been implicated in disc
degeneration. (15) The matrix metalloproteinases are regulated by specific inhibitors (TIMPS), cytokines
(Interleukin-1) and growth factors. (16) Spinal loading may interfere with diffusion into the disc by reducing
the gradient across the vertebral endplate. As disc metabolism becomes anaerobic, there is an
accumulation of lactic acid, fall in pH, loss of chondrocyte and fibroblast function, and activation of the
metalloproteinases.

Although the mechanism of action may not be fully understood the thixotrophic (17) properties of the
nucleus material may facilitate nuclear migration toward the centre of the disc under negative pressures
created by VAX-D.

It has been shown experimentally that elevated lactate levels and low pH in the disc prohibit disc
proteoglycan synthesis and accelerates matrix degeneration (18).

Destruction of the proteoglycan matrix and fluid retention properties can lead to a degenerative cascade
with loss of cellular reparative functions and vitality. The reduction of intradiscal pressures may enhance
the diffusion gradient across the endplate into the avascular disc. It has been postulated that mechanisms
that facilitate oxygen and nutrient uptake in the disc may exert a beneficial effect on the metabolism and
restorative functions.

Successful reduction of intradiscal pressures with VAX-D therapy represents a technological advance in
lumbar spinal treatment and is likely to affect both the biomechanical and biochemical causes of
discogenic pain. The results from this study demonstrate that VAX-D is an effective treatment for the
management of patients with chronic low back pain and is significantly superior when compared to TENS
therapy. Analysis of the data demonstrated an attributable success rate of 68.4% for VAX-D. These
findings are consistent with earlier studies by Gose E, Naguszewski W, Naguszewski R. (14)
The results of this prospective study demonstrated that VAX-D can achieve a statistically significant
improvement in pain and functional outcome in managing

patients suffering from disc related chronic low back pain.
Acknowledgments: Australian National Musculoskeletal Initiative: For advice and instruction on the use of
instruments for the outcome measures used in the present study.

Jane Ambrose, Biostatistician Quintiles: For statistical analysis of the data.

Disclosure: Dr Russell Smart is contracted to and a shareholder in VAX-D Australasia Pty Ltd, a private company
that delivers VAX-D service in Australia.

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