ABSTRACT

Reductions in low back pain and referred leg pain associated with a diagnosis of herniated disc,
degenerative disc disease or facet syndrome have previously been reported after treatment with a VAX-D
table, which intermittently distracts the spine. The object of this study was to use dermatomal
somatosensory evoked potentials (DSSEPs) to demonstrate lumbar root decompression following
VAX-D therapy. Seven consecutive patients with a diagnosis of low back pain and unilateral or bilateral
L5 or S1 radiculopathy were studied at our center. Disc herniation at the L5-S1 level was documented by
MRI or CT in all patients. All patients were studied bilaterally by DSSEPs at L5 and S1 before and after
VAX-D therapy. All patients had at least 50% improvement in radicular symptoms and low back pain and
three of them experienced complete resolution of all symptoms. The average pain reduction was 77%.
The number of treatment sessions varied from 12 to 35. DSSEPs were considered to show improvement
if triphasic characteristics returned or a 50% or greater increase in the P1-P2 amplitude was seen. All
patients showed improvement in DSSEPs after VAX-D therapy either ipsilateral or contralateral to the
symptomatic leg. Two patients showed deterioration in DSSEPs in the symptomatic leg despite clinically
significant improvement in pain and radicular symptoms. Overall, 28 nerve roots were studied before and
after VAX-D therapy. Seventeen nerve root responses were improved, eight remained unchanged and
three deteriorated. The significance of DSSEP improvement contralateral to the symptomatic leg is
emphasized. Direct compression of a nerve root by a disc herniation is probably not the sole explanation
for referred leg pain. (Neurol Res 2001; 23:706-714)

Key words: lumbar radiculopathy vertebral decompression dermatomal somatosensory evoked
potentials low back pain VAX-D therapy

INTRODUCTION

Improvements in low back and referred leg pain associated with a diagnosis of herniated disc,
degenerative disc disease or facet syndrome have previously been reported after VAX-D therapy (1). In
71% of the 778 cases, the pain was reduced to 0 or 1 on a 0 to 5 scale. Improvements in mobility and
activities of daily living were also noted. The average decrease in pain, plus or minus the standard error
of the estimate, was 2.88 +/-0.05 units on a scale of 0-5, and a paired two-sample t-test shows that this
pain decrease was at least 2.68 units with p<0.00005. The average increase in mobility was 1.17 +/- 0.03
on a 0-3 scale, and this value was at least 1.04 units with p<0.00005. Similarly, the average increase in
the activity score was 0.96+/-0.04 units on a 0-3 scale, and this average improvement was at least 0.83
with p<0.00005. The coefficient of linear correlation (2) between mobility and pain scores was 0.72 and
between pain and activity it was 0.60. The clinical improvement in pain, mobility and activities of daily
living argues strongly that nerve root decompression can reasonably be expected to follow VAX-D
therapy.

Lumbar disc decompression is clearly possible non-surgically through the application of effective lumber
distraction tensions. Gupta and Ramarao (3) treated 14 patients with prolapsed intervertebral disc
syndrome with continuous traction and showed complete or partial resolution of the defects on
epidurogram. Mathews (4) likewise showed reductions in disc herniations in two patients by
epidurography accompanied by vertebral body separation of 2mm per disc space. Ramos and Martin (5)
measured intradiscal pressure by connecting a cannula inserted into the patient’s L4-5 disc space to a
pressure transducer. Tensions applied by the VAX-D table were observed to decompress the nucleus
pulposus significantly, to below –100 mm Hg.

Dermatomal somatosensory evoked potentials (DSSEPs) are an established and effective physiologic
tool for assessing single nerve root function pre- and post- operatively (6,7,8,9,10,11) and are useful as
well for monitoring potential acute nerve root injury during surgical procedures using intrapedicular fixation
of the lumbosacral spine (12).

Dvonch et al (13) studied the root specificity of DSSEPs using myelograms and surgical findings as the
standards and found the accuracy of DSSEPs to be 85.7% for lumbar radiculopathy when compared to
myelograms and 87.5% when compared to surgery. Sensitivity was 0.93 and specificity was 0.86. Chi
square analysis was applied and accuracy was defined as the ratio of all correct results to the total
number of nerve root pairs tested. Bilateral DSSEPs were performed on each patient at L5 and S1.
Each nerve root was compared to the contralateral root and differences in latency of more than 3 msec or
amplitude differences of more than 75% were considered significant. Overall, DSSEPs were shown to
have an 86% accuracy in root specific diagnosis. The authors also concluded that since pain is a frequent
accompaniment of root entrapment, DSSEP findings can provide information in addition to the structural
abnormalities demonstrated by myelograms by offering a physiologic way of monitoring the sensory side
of the nervous system. DSSEPs should thus be a useful adjunct in the selection of patients undergoing
lumbar spine surgery.

PAIN LEVEL (0 to 10 scale)
 

PATIENT	BEFORE	AFTER	# OF TREATMENTS
	VAX-D	VAX-D
1	5	0	12
2	8	0-0.5	35
3	7-8	4	13
4	3	0	10
5	5	1	10
6	5-6	2	20
7	6-7	2	20

Figure 1. Pain levels and number of treatments for the seven patients.

Scarff et al (14) performed DSSEPs on 38 consecutive patients with suspected disc herniation. These patients subsequently underwent myelography and surgery with verification of nerve root entrapment by disc herniation. For each patient, comparisons were made regarding latency and amplitude of the DSSEPs from the involved and uninvolved leg. Differences in latency of more than 3 msec measured from the peak positive wave or an amplitude reduction of 75% were considered significant. Of the 38 patients, 35 had abnormal evoked potentials for the specific root involved. One patient had abnormalities for the contra-lateral root and 2 patients with bulging discs had normal DSSEPs. Similarly, Larson (15) utilized somatosensory evoked potentials (SSEPs) and DSSEPs in evaluating 66 patients with lumbar stenosis. Satisfactory recordings were obtained from stimulation of the medial (L5) and lateral (S1) aspects of the foot in 62 of the 66 patients. Onset latency remained unchanged but the amplitude of the initial portion of the evoked potential waveform diminished to 50% or less of control after walking, flexion or extension. These changes were reversible and the presence of these abnormal responses correlated with a good surgical result. Furthermore, 26 of these patients had predominantly only unilateral symptoms of the lower limb but bilateral evoked response abnormalities were seen.

MATERIALS AND METHODS

DSSEPs were conducted at our center on seven consecutive patients suffering from mechanical low
back pain with referred leg pain in either an L5 or S1 distribution or both. Clinically, patients with L5
radiculopathy experience pain in the back of the thigh, lateral calf and dorsum of the foot. Patients with S1
radiculopathy experience pain in the back of the thigh, back of the calf and lateral foot (17). Two patients
had bilateral symptoms. All seven patients had disc bulging or disc herniation on MRI or CT at the L5-S1
level. Two of these patients had disc herniations at L4-5 and one patient (patient #2) had multilevel disc
herniations with symptoms referring into the left S1 distribution only. The initial pain levels and numbers of
treatments are shown in Figure 1.

Each patient underwent bilateral lower extremity DDSEPs at L5 and S1 immediately before and within two
weeks after the completion of VAX-D therapy. Data was obtained using a Nihon-Kohden Neuro Pack #4
instrument. All patients were studied at our center by a certified technologist from Rasmussen
Diagnostics, Woodstock, Georgia. The number of treatment sessions per patient varied from 10 to 35.

Dermatomal stimulation at L5 was done medial to the extensor hallicus tendon on each side with the
ground reference over the anterior ankle. For S1, stimulation was done at the lateral aspect of the fifth
metatarsal with the ground electrode over the ankle, as shown in Figure 2. Cortical electrodes were
placed 3 cm anterior and posterior to Cz. Filter settings were set at 10 Hz to 250Hz. The rate of
stimulation was 3 per second delivered as a square wave pulse of 0.2msec duration with intensities of 2.2
to 7.6 mA. Stimulation intensity varied somewhat between patients and was determined by beginning at a
low level of stimulation and increased until the patient perceived a strong but not painful, tapping
sensation. Two trials were performed on each root to verify that the waveform was reproducible. The
number of stimulations per trial ranged from 150 to 300. The two trials were then averaged and the final
waveform was smoothed using a 9-point running average. Each patient was studied consistently each
time either supine or in a recliner. Room temperature remained constant at 72 degrees Fahrenheit and
wakefulness was assured.

The authors theorized that the morphology of the waveforms would be distorted or suppressed prior to
VAX-D therapy given that the duration of clinical symptoms ranged from 8 weeks to 60 months for the
patients in this study. Treatment sessions were given Monday through Friday with patients under
treatment from 2 to 7 weeks. This amount of time may have allowed nerve root functional recovery while
the patient was receiving VAX-D therapy. Our study is in contrast to previous studies in the literature
which eliminated patients with poorly reproducible waveforms before surgery. Intra-operative studies have
focused on latency delays or a sudden loss of the first component of the waveform as a sign of acute nerve
root injury. Because VAX-D therapy is a treatment which may have cumulative benefit over time (1), the
authors assumed that as nerve roots were decompressed, electrical transmission would improve but not
necessarily return the DSSEP to a truly normal waveform. We thus placed emphasis on the reconstitution
of the waveform and its overall morphology, while evaluating DSSEPs generated in this study using
latency and amplitude parameters consistent with the literature as well. Additionally, the literature has
emphasized side to side comparisons at each nerve root level. This study compares each nerve root
before and after VAX-D therapy.

Several quantitative measures of waveform quality were considered, including the amplitudes of the
P1-P2 and P2-P3 portions of the waveform, their post-stimulus times of occurrence, and the presence or
absence of P1, P2, and P3 “peaks” (positive or negative) in the waveform. However, for some
waveforms it was not possible to distinguish with certainty between true peaks and noise artifacts. In this
circumstance, the authors felt that it was more practical to consider the waveform as a whole, and decide
if its quality increased or decreased significantly. The quality depends on the amplitudes, the presence or
absence of P1, P2, and P3 peaks, and the ability to distinguish the waveform from the noise. The
measure is subjective, so all the waveforms are shown in Figure 4, and are labeled as “better”, “worse”, or
“same”. These decisions were made separately by the three authors and the technician, all of whom
agree with this labeling.

RESULTS

All the DSSEPs, before and after VAX-D therapy, are shown in Figure 4. Clinically, all patients in our
study were symptomatic before VAX-D therapy. Low back and referred leg pain were reduced by over
50% in each patient after VAX-D therapy and three were essentially pain free. The average pain
reduction was 77%. Before VAX-D therapy, DSSEP waveform morphology was often abnormal, with
absence of the first peak (P1) being most typically seen. This is not an unexpected finding since temporal
dispersion of axonal volleys will affect early cortical DSSEP peaks, resulting in their

diminution or loss without the loss of later peaks. It has been postulated that the resiliency of later peaks is
due to the cerebral cortex functioning as an integrator, resynchronizing the incoming inputs (18). For
those DSSEPs in which P1 was present before and after VAX-D therapy, a P1 latency was measured as
well as a P1-P2 amplitude. Following the criteria of Scarff et al (14) for latency and Larson (15) for
amplitude, a difference in latency of 3 msec or greater or an amplitude change of 50% or greater was
considered significant. No significant changes were seen on average in either latency or amplitude in our
study for those DSSEPs possessing a distinct P1 before and after VAX-D therapy.

If there were no intrinsic difference between the data before treatment and the data after treatment, then
the probability that the DSSEP response would improve would be equal to the probability that it would get
worse. There would also be some probability that the quality of the response would neither increase nor
decrease but would remain the same, within the limits of our ability to estimate the quality of these
waveforms.

In Figure 5, eight of the 28 responses did not change significantly, 17 improved, and three were worse
after treatment. The probability that results this good would be obtained by chance is less than 0.0013, i.e.
p< 0.0013, according to the cumulative binomial distribution, as shown below. If it were true that, for the
20 responses that changed, a change for the better (B) were as likely as a change for the worse (W), then

P (17 of the 20 are B ) = 20!/ (17! 3! 220 ) = 0.001087189

P (18 of the 20 are B ) = 20!/ (18! 2! 220 ) = 0.000181198

P (19 of the 20 are B ) = 20!/ (19! 1! 220 ) = 0.000019073

P (all 20 are B ) = 20!/ (20! 0! 2 20 ) = 0.000000954

Sum 0.001288414

The sum of these gives the probability that 17 or more of the 20 would be better by chance: P (17 or more
are B ) = 0.001288414 . So p < 0.0013 that results as favorable as those found in this study would
occur by chance. Statistically, these results are very
significant.

CASE REPORTS

Patient #1

A 48 year old male with a five-month history of chronic low back and left leg pain predominantly in an S1
distribution. Lumbar MRI revealed a moderate left paramedian herniated nucleus pulposis compressing
the S1 nerve root. The patient received 12 VAX-D treatments and experienced complete resolution of low
back and left leg pain.

Patient #2

A 54 year old county school psychologist with an eight week history of low back pain and left S1
radiculopathy. He had a previous episode of left leg sciatica several years before which resolved with bed
rest and medication. Lumbar CT revealed a large left paracentral herniated nucleus pulposis at L5-S1
compressing the left S1 root. Additionally, a moderate central herniated disc was seen at L4-5 resulting in
moderate spinal stenosis and a small left paracentral disc herniation was seen at L3-4. He underwent a
total of 35 VAX-D treatments and experienced a greater than 90% reduction of his low back and left leg
pain.

Patient #3

A 31 year old female with a 2 year history of chronic low back pain and intermittent left leg pain following
an L5 and S1 distribution. Lumbar CT showed a contained central annular bulging of the L3-4 and L4-5
discs with no significant underlying neural compromise, as well as a small to moderate midline herniation
at L5-S1 causing some effacement of the underlying thecal sac. She completed 13 VAX-D sessions with
a 50% reduction in pain and experienced a subjective increase in mobility.

Patient #4

A 48 year old male with a 60 month history of chronic low back pain and right leg pain in an S1
distribution. Lumbar MRI showed desiccation and degenerative changes of the L5-S1 disc with a right
sided herniation causing effacement of the right S1 root. Minimal bulging of the L3-4 and L4-5 discs was
noted as well. After ten VAX-D treatments all pain was eliminated.

Patient #5

A 56 year old female with a 9 month history of chronic low back pain and occasional episodes of right
sided sciatica in an L5 distribution. Lumbar MRI showed degenerative disc disease at L4-5 and L5-S1
with a mild diffuse disc bulge at L4-5 encroaching upon the right L5 root. The patient experienced an 80%
reduction of pain after her tenth VAX-D treatment.

Patient #6

A 23 year old male with a 10 month history of low back pain after a lifting injury at work. Pain and
numbness were present intermittently in both legs in an L5 and S1 distribution but more severely affected
the left leg. Lumbar MRI scan showed degenerative disc disease at L4-5 and L5-S1 with a left sided
herniated disc at L5-S1. After twenty VAX-D treatments he no longer experienced any numbness in his
legs and his pain was reduced by 50%. He elected to stop further treatments in favor of returning to work.

Patient #7

A 33 year old EMT with a 38 month history of low back pain associated with periods of either right, left or
bilateral leg pain and numbness in an L5 and S1 distribution. Predominantly the right leg was most
symptomatic at the time she underwent VAX-D therapy. A lumbar MRI before treatment showed a
degenerated L4-5 disc with a left paracentral herniation indenting the thecal sac. At L5-S1 the disc was
degenerated with a small left paracentral herniation without nerve root compromise. The patient
underwent 20 VAX-D treatments with complete resolution of leg numbness and a 70% reduction in low
back and leg pain.

DISCUSSION

We know that VAX-D is a safe and generally successful treatment of low back pain associated with
lumbar disc herniation, degenerative disc disease, or facet syndrome. VAX-D was designed with a
primary purpose to relieve low back pain with or without radiculopathy. Surgery, oftentimes, is focused
primarily on nerve root decompression to relieve radicular pain and any improvement in back pain follows
as a secondary benefit. This secondary benefit occurs despite the fact that discectomy and laminectomy
involve further disc and spine disruption. The literature is clear that not all patients benefit by surgical
nerve root decompression and also that surgical patients on average fare no better long term than patients
who are managed conservatively (20,21,22,23 24).

The present study used DSSEPs to provide an objective means of measuring a physiologic cortical
manifestation of nerve root decompression. In 1994 using disc manometrics, Ramos provided clear
documentation that negative intradiscal pressure changes down to –150 mm Hg were achieved with
VAX-D treatment. Tilaro and Miskovich (25), using a CPT neurometer, showed that peripheral peroneal
and sural nerve distribution sensation were improved in 27% or returned to normal in 67% of 17 patients
with radiculopathy symptoms after VAX-D treatment. They used the CPT Neurometer to deliver a
sinusoidal electrical stimulus. The threshold of perception was defined as the minimal amount of stimulus
required to evoke a sensation at least 50% of the times it was presented. Results were taken three times
at each site and were reliable, i.e., statistically they could not have been fabricated by a patient. Tilaro
and Miskovich reasoned that improvement with VAX-D must have reflected nerve root decompression
because no other change in function of the peroneal and sural nerves, spinal cord, brainstem or cerebral
cortex would be expected. Neurometer measurements rely on the patient’s subjective experience
(perception) of sensory stimulation. Perception involves cortical activation and integration. It is a
conscious subjective response.

Somatosensory testing, in general, assesses the electrophysiology of the pathway to the brain’s cortex as
a consequence of a sensory experience such as vision, hearing, or extremity sensation. Scalp electrodes
pick up cortical activity which is then signal averaged to create a waveform. Our results extend the work of
Ramos and Tilaro. We chose DSSEPs to isolate L5 and S1 root function by dermatomal stimulation.
Further, results were taken bilaterally such that each patient in essence served as his or her own control.
Four roots were monitored for all patients. Restored waveforms had a triphasic appearance which is
normal and expected for the method of recording we used. DSSEP’s are used widely for monitoring
potential spinal cord or nerve root injury during spinal surgery, particularly when there is a concern about
injuring nerve roots.

In this study, we found that multiple nerve roots appear to be decompressed in most of the patients, which
fits nicely with the data of Tilaro and Miskovich. Their neurometer measurements were taken over the
peroneal and sural nerves, which are relatively large. Although these nerves derive from a limited number
of nerve roots, they are not pure. Stimulation of the peroneal nerve sends impulses through L4 and L5
roots. Likewise, stimulation of the sural nerve sends impulses through L5 and S1. It may be that multiple
nerve root decompression was responsible for the large improvements in the perception thresholds
measured by Tilaro and Miskovich.

Clinical implications that can be derived may have importance as to how we view the low back and what
we may think is the main source of pain for a particular patient. Patient clinical histories and examinations
suggest that nerve roots are not involved in isolation but that adjacent nerve roots and even contralateral
changes may exist to account for symptoms that overlap dermatomes or are bilateral despite a unilateral
lesion. The DSSEPs reviewed here provide physiologic evidence that this possibility not only exists but
is likely.

The best surgical outcome to be expected occurs when spine imaging is consistent with symptoms and
clinical findings. These patients tend to do well with surgery and therefore one might conclude that nerve
root decompression has something to do with why leg pain in particular responds. Other patients do less
well, particularly when symptoms and clinical findings are inconsistent with the results of diagnostic
imaging. Possible explanations relate to irreversible nerve root injury from a ruptured disc, epidural
fibrosis and other poorly understood reasons.

The remarkable improvements following VAX-D therapy (71%) for a variety of pathologies (1) suggests
some possibilities for these “otherwise poorly understood reasons.” Our study suggests that VAX-D
exerts its benefit at more than one level ipsilateral and contralateral to the direction of disc herniation.
Evidence is provided that multiple root abnormalities by DSSEP may be present despite one structural
lesion by MRI. Although clinicians assume that the consequences of such structural pathology is an
important source of pain, our present results raise the possibility that such pathology may not be the main
cause of pain but may allow consequent or subsequent changes to become the primary source of pain for
an individual patient. Tsai et al (26) studied 33 patients with intraoperative DSSEPs undergoing
micro-decompression for single level, unilateral lumbosacral radiculopathy. Nineteen patients had
acceptable DSSEPs at baseline with 13 of these19 patients having an abnormal DSSEP for the
symptomatic nerve root defined as a side-to- side latency asymmetry of greater than 5% before surgery.
Four patients had DSSEP side-to-side latencies within 5% at each nerve root level and 2 patients had
poorly reproducible evoked responses on the symptomatic side. All latency asymmetries resolved and
improved waveforms were seen in the 2 patients with poor evoked responses before surgery. Despite
apparently successful nerve root decompression, clinical outcome at 3 months was good to excellent in 13
patients, fair in 4 patients and poor in 2 patients. This may at first seem surprising but do we really know
what is the most important source of pain and whether it relates to the primary event such as a disc
herniation or does it follow as a consequence? In our study, all patients were clinically improved but only
one showed contralateral improvement by DSSEP. The authors wonder what the outcome would have
been if the patient had been operated on ipsilaterally. With the above analysis, we now have an
explanation for overlapping dermatomal complaints, bilateral symptoms, and sometimes pain going down
“the wrong leg”- meaning that the MRI shows a disc herniation directed opposite to the symptomatic leg.

We suggest that VAX-D therapy effectively manages mechanical low back pain with or without referred
leg pain through spine segment mobilization. Spine segment motion integrity is a crucial concept and
probably best explains the correlation previously found between reduced pain and improved gross spine
mobility subsequent to VAX-D therapy (1). A spine motion segment consists of two vertebral bodies with
an intervening disc and all attached and enclosed structures (27). Segment motion normally is dynamic
with flexion, extension, torsion, and tilting often combined simultaneously allowing pain-free movement in a
normal spine. This occurs normally without nerve root impingement despite even extreme spine flexion
and extension seen in gymnasts and contortionists. Furthermore, it is known that the spinal cord can
adapt to length changes of the spinal canal because the cord itself is folded when the spine is in a neutral
position and will unfold during flexion and can fold further during spine extension. The nerve roots follow
the spinal cord but do not fold and unfold (27). It is the ability of the vertebra to translate and rotate upon
each other that provides slack to the nerve roots. Impairments here stymie functional compensations to
reduce “the pressure on nerve roots” as the spine is loaded by weight- bearing activities. VAX-D therapy
helps to restore mobility and allows for a return of dynamic functional compensation. A natural
consequence of disc injury is to accelerate “natural” fusion of the segment. If the segment “fuses” in a
position that allows enough room in the lateral recess, central canal, and neural foramina –then there may
be no pain. If however, such fusion is less harmonious there will be pain plus lost motion. VAX-D is
unique in its position to alter the reactive process leading to symptomatic bony fusion whereby osteophytic
changes are seen on the anterior and posterior aspects of the vertebral endplates. Again Gose,
Naguszewski and Naguszewski (1) showed a clear and strong correlation between increased mobility and
decreased pain reported after VAX-D therapy. This dynamic compensation is presumed to be the result
of spinal reflexes that function specifically to maintain proper alignment of stacked spine motion
segments. These spinal reflexes are protective against nerve root injury and can be acted upon by higher
centers to facilitate smooth, safe and effective voluntary movement. We know that the erector spinae
muscles are “ratcheted” on the spine like shingles on the roof of a house to allow accordion-like motion.
The transversospinal muscles span one, two, three or more segments (28). Spinal reflexes are in place to
coordinate all of these muscles to allow full range of motion without nerve root impingement. With acute
lumbar injuries, the spinal reflexes may induce sustained muscular contraction resulting in radiographic
straightening of the lumbar spine and immobilization of one or more lumbar motion segments. Sustained
muscular contraction for weeks may lead to adhesive capsulitis of the facets, perpetuating motion
segment immobility despite eventual resolution of muscular spasm. Additionally, the persistence of
contracted musculature may eventuate into contracture reducing mobility of the affected lumbar motion
segment. Such focal contracture so to speak, is myofascial fusion. We argue that VAX-D therapy is best
suited to release such contracture.

With degenerative disc disease there is a loss of disc height. Disc height is crucial in determining neural
foraminal vertical height. Ligamentum flavum hypertrophy may develop and encroach upon the nerve roots
posteriorly. End plate changes and facet changes can also encroach on the neural foramina anteriorly and
posteriorly respectively. All these changes limit the extent to which neuro-protective spinal reflexes can
relieve pressure on nerve roots. The spine motion segment loses dynamic range and the small “shingled”
muscles cannot act to cause a dynamic translation of the segment and reduce pressure on the
neuro-vascular bundle. At this point axial loading of the motion segment is poorly tolerated because there
is no dynamic reserve to allow minute translation, rotation or tilting of the neural foramen. The neural
foramen is fixed in anterior and posterior diameter with further narrowing occurring vertically as the disc
fatigues and bulges under axial loading. Disc fatigue is probably time dependent under sustained axial
loading and accounts for the clinical presentation of patient complaints that they cannot stand or sit for
more than a minute or two (static loading) before worsening radicular symptoms occur. Walking relieves
symptoms at least initially by providing external dynamic weight shifting across the affected lumbar motion
segment.

Typically, patients with mechanical back pain experience an increase in their low back pain and radicular
symptoms during times when their spine is asked to support body weight such as during prolonged sitting
or standing. The pain generators for these patients may be a herniated disc, reduced neuroforaminal size
secondary to degenerative disc disease or facet syndrome. It has been shown that lumbar traction can
produce a “distraction” or increased separation of 1 to 2 mm between each pair of lumbar vertebra (4) as
well as reduce the size of disc herniations (3,4). Furthermore,

Twoney (29) studied the effects of traction on the lumbar spines of cadavers stripped of the paraspinal
musculature and found residual lengthening of the lumbar spine after release from sustained traction. This
residual lengthening was seen in those spines in which degenerative disc changes were prominent and
may relate to disc rehydration since the spines were continuously bathed in normal saline throughout the
experiment. In-vivo, we do not know whether “traction” physically results in sustained lengthening of the
spine segment after a distraction tension has been released but we do know that lengthening of the
lumbar spine segments does occur during applied traction. Lumbar distraction may improve facet joint
mobility by releasing an entrapped interarticular meniscus or fold of the capsule or synovial membrane
(30) and may restore spine segment mobility by stretching and releasing erector spinae muscles
contracted by sustained spasm.

The VAX-D table represents a technological advance in the application of effective lumbar distraction
tensions with improved patient tolerability and satisfaction compared to previous lumbar traction devices
requiring thoracic corsets or the application of heavy static weights (1). VAX-D therapy has been shown
to decompress the nucleus pulposis significantly, to below –100 mm Hg (5). The intervertebral discs
separate the vertebra with the annulus fibrosis containing the nucleus pulposis by its attachment to the
vertebral margins. The negative intradiscal pressures generated by VAX-D suggests that an increased
separation of the vertebra occurs during VAX-D therapy, as it did with older lumbar traction devices.

Traditionally, the term “decompression” as applied to the spine has referred to nerve root decompression.
Surgery for decompression has been directed at the radiographic sites of nerve root entrapment including
the removal of herniated disc material or osteophytes at the lateral recess or neural foramen. This study,
however, has demonstrated that most of the patients suffering from chronic low back pain and
radiculopathy had multiple nerve root abnormalities based on abnormal DSSEPs, many of which would
not be predicted radiographically. Successful treatment by VAX-D therapy resulted in clinical reduction in
pain and improved DSSEP waveforms suggesting that nerve root decompression is occurring at multiple
levels. With VAX-D therapy, the concept of “decompression” can now be broadened to include the lumbar
spine motion segment itself, with decompression not only of the nerve roots, but also the disc, facet joints
and potentially, the paraspinal musculature as it is stretched and muscular spasm resolves.

An acute disc injury and discogenic pain may often be the primary process leading to low back pain and
lumbar radiculopathy. Biochemical and inflammatory changes within the disc contribute to the patient’s
pain. The negative intradiscal pressures generated by Vax- D therapy may promote healing as nutrients,
oxygen and water are transfused into the disc which is otherwise an avascular structure, dependent
predominantly upon a diffusion gradient as the main mechanism of transport of these vital substances into
the disc (31). However, chronic low back pain is often accompanied by lost mobility and secondary
consequences such as nerve root dysfunction above and contralateral to the disc herniation, as indicated
by this study.

For any given patient with low back and referred leg pain, we cannot predict with certainty which cause
has assumed primacy. Therefore surgery, by being directed at root decompression at the site of the
herniation alone, may not be effective if secondary causes of pain have become predominant. Vax- D
therapy however addresses both primary and secondary causes of low back and referred leg pain. We
thus submit that VAX-D therapy should be considered first, before the patient undergoes a surgical
procedure which permanently alters the anatomy and function of the affected lumbar spine segment.

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3. Gupta RC, Romarao SV. Epidurography in the reduction of lumbar disc prolapse by traction. Arch
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