>>Continued
Response of pain to
static magnetic fields in postpolio patients:
A double-blind pilot
study.
METHOD
Subjects
We recruited 50 patients with postpolio
syndrome who reported muscular or arthritic pain and who consented to
participate in the study. The diagnosis of the postpolio syndrome was made
according to well-established criteria.
The
patients selected for the study had significant pain for at least 4 weeks,
had not taken an analgesic or similar drug for at least 3 hours before the
study, had a trigger point or a circumscribed painful region by palpation,
and had body weight less than 140% of predicted for age and height. Patients
were required remain in the clinic for 1 hour after the scheduled visit with
the postpolio team. Only five of the patients invited to participate
refused; four could not stay at the clinic for the additional required time
and one refused because of concern about side effects.
The
consent form given to the patients stated the purpose of the research. No
explanations were given as to expected responses, but patients were told
that the level of pain would be assessed by palpation of a trigger point
before and after application of the device......
Table
1 summarizes the characteristics of these patients according to the group to
which they were randomized (magnetic treatment or placebo).
Treatment Intervention
The
specific devices used were the BIOflex® magnets with a pattern of
concentrically arranged circles of alternating magnet polarity. The company
made available to us 8 discs 40mm in diameter, 1.5mm thick; 18 discs 90mm in
diameter, 1.5mm thick; 20 credit-card-sized pads, 83 X 53mm, 1.5mm thick;
and 24 strips, 175 X 50mm, 1.5mm thick. The magnetic field intensity of the
active devices was rated at 500 Gauss at the device surface for the 40-mm
disc and the strips. The 90-mm discs and the credit-card pads were rated as
300 Gauss at the surface of the device. The manufacturer supplied us with an
equal number of the active and placebo devices of identical size and shape.
Each device was placed in a number-coded envelope, and all devices were
delivered to us in four separate boxes according to device shape. The code
numbers identifying active and placebo devices were not broken until all
patients completed the study.
After
the patients gave their written consent, they were asked to complete a
McGill Pain Questionnaire to provide a subjective evaluation of their
general pain experience. In this study, only one area of reported pain was
evaluated, even though multiple sites may have been present. An active
trigger point associated with the site of referred pain was grossly elicited
first by finger palpation and then identified by firm application of a blunt
object approximately lcm in diameter, which in nonpainful areas produces a
sensation of pressure but no pain. The subject was asked to subjectively
grade the pain at the trigger point on a scale from 1 to 10 (with 1 being
the least and 10 being the maximum). When patients reported pain in more
than one area, the area most sensitive to palpation was selected.
The
pain scale used in this study had been previously validated and is
particularly applicable to patients with disabilities. Depending on the area
involved, we used either a disc, a credit-card-sized pad, or a strip-shaped
device. An envelope containing a device of the appropriate shape was
randomly selected from a box and applied to the skin with adhesive tape.
Each patient was then asked to remain in the clinic or immediate clinic
area, to keep the device in place for the next 45 minutes, and assume
whatever position was most comfortable, including walking. After 45 minutes,
the device was removed, and the patient was asked to report whatever
sensations were felt after the application of the device. Again, the patient
was asked to assess the intensity of the pain felt on palpation of the
active trigger point associated with the referred pain site. The same scale
of 1 to 10 was used. Although we did not measure the exact pressure exerted
by the blunt object at the trigger point before and after the study, the
investigators tried to be as consistent as possible on the amount of applied
pressure. There was no systematic follow-up of patients after the
application of the device, but in many cases we obtained information at the
time of the patients next visit to our clinic.......
RESULTS
Table 1
shows the characteristics of the study participants. There was no
significant difference in any of the variables that described the two
groups. There was a much greater proportion of women than men in both groups
(the women-to-men ratio of the participants in the study is slightly higher
than the ratio for our clinics population). The race-ethnicity distribution
of the participants parallels that of the postpolio clinic patients. The age
of onset of poliomyelitis and the age of onset of the postpolio syndrome
were almost identical in both groups. Since the time of onset of the
postpolio syndrome cannot always be clearly established, the data in the
table should be considered estimates only. The classification of the type of
pain as predominantly muscular or predominantly arthritic is somewhat
arbitrary because arthritic changes are often accompanied by muscular spasm
with clearly distinguishable trigger points. An analysis of the frequency
distribution of the location of pain where the active or inactive magnetic
devices were applied did not show any significant difference between the two
groups. The sacroiliac joint was the most common location for both groups
(41% of those who received the magnetized device and 33% of those who
received the inactive device).
Table 2
shows the mean and standard deviation of the pain scores before and after
application of the device in the two groups of subjects. The pretreatment
score was almost identical in both groups of subjects, but there was a
highly significant difference between pre-treatment and posttreatment scores
in the two groups. Those who received the active device reported much less
pain than those who had the inactive device.
It is
of interest to examine the proportion of patients in each group who reported
improvement in pain intensity. Since the average decrease of pain score was
1.1 (+-1.6) in the subjects who received the inactive device, we decided to
dichotomize changes in pain scores as "improved" if the score decreased by 3
points or more and "not improved" if the decrease was less than 3 points. As
shown in table 3, 22 patients (76%) in the active-device group showed
improvement, compared with only 4 (19%) in the inactive-device group. This
difference is highly significant (p < .0001). Also, the average score
decrease in the four patients who had a placebo effect was 4 points versus 7
for those who had a treatment effect..
Table 2: Pretreatment
and Posttreatment Pain scores
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Pretreatment Pain Score (mean +- SD)
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Posttreatment Pain Score (mean +- SD)
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Change in Pain score (mean +- SD)
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Table 3: Proportion of
Subjects Reporting Pain Improvement by Magnetic Activity of the Treatment
Device
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Active Magnetized Device (n=29)
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X2 (1 df ) = 20.6 (p
<.0001).
DISCUSSION
The results of this randomized pilot clinical trial show that static
magnetic fields of an intensity of 300 to 500 Gauss are effective in the
control of pain in patients with the postpolio syndrome. Whether the pain
was of a myofascial or arthritic nature, it seemed to respond equally well
to the static magnetic field and the effect was noticed within 45 minutes
from the onset of the application.
We must point out that we studied the effect of the static magnetic fields
in one painful area only on each subject and we did not attempt to quantify
the potential impact of such field on other painful areas that may have been
present on the same patient. Interestingly, some patients recorded benefit
derived from the magnetic field in other areas. This effect was reported
mostly in the patients who bad pain in both sacroiliac joints, in which case
we always applied the device on the one that was most sensitive to
palpation......
The intensity of the applied magnetic fields was rather low in relation to
that applied in other studies, and we did not attempt to assess a
dose-response effect. It is likely that the level of penetration of the
magnetic field is related not only to the magnets intensity, but also to the
distance between the superficial area to which the device is applied and the
site of the trigger point that lies on the fascial plane of a muscle,
tendon, or joint. Because of this, we excluded from the study very obese
patients or those who had a significant amount of subcutaneous fat overlying
the trigger point associated with the painful area. The fact that Hong did
not find evidence of effect in his double-blind study of a loose magnet
necklace may be due to the small delivered magnetic intensity of the device
which was not directly applied over specific pain trigger points.
We cannot explain the significant and quick pain relief reported by our
study patients. The effect could result from a local or direct change in
pain receptors, but it is also possible that there was an indirect central
response in pain perceptioin at the cerebral cortical or subcortical areas,
or a change in the release of enkephalins at the reticular system. If the
magnetic fields have an impact on the subcortical level of the brain, it is
possible that the application of one magnetic device in one painful area may
benefit to a greater or lesser extent the pain elicited in other trigger
points. This is an issue that requires further study. Bruno and colleagues
have pointed out the existence of lesions in various areas of the brain of
poliomyelitis survivors, and they believe that these lesions may explain the
hypersensitive response to painful stimuli that they have observed in
postpolio patients. This should not be interpreted to mean that the relief
of pain produced by magnetic fields that we observed was specific for
postpolio patients because similar responses to magnetic fields have been
reported in patients without known lesions of the central nervous system.
Even so, our understanding of pain and pain relief is far from complete.
Insofar as we can determine from the literature, this double blind
placebo-controlled study using permanent magnets in a bipolar configuration
directly applied to trigger points may be the first reported. This study
coincides with mounting evidence that magnetic fields interact in
significant ways with biological tissues. The exact mechanisms of the
interaction of magnetic fields with biological tissues resulting in
functional changes are unknown. This is particularly true for our
understanding of the pain relief associated with the application of a
magnetic field to trigger points as demonstrated in this study. Much
progress, however, is being made in the field of bioelectromagnetics, in
both the experimental studies and theoretical concepts. Several of these
concepts (some old and some new) appear to be promising; certainly, they are
ultimately testable.
We are interested in the possible role of water in the pain mechanism, and
attempts will be made to evaluate the physical basis of this idea using
magnetic resonance technology. It is now clear that water is organized in
space and time, and in a human study conducted by one of us (C.H.)
subjective pain relief was associated with a shift of T-cells into the
S-phase Beall and colleagues demonstrated cyclical changes in the physical
state(s) of water with the water being most organized in the S-phase. That
water plays a major role in explaining the therapeutic effects of magnetic
fields has also been proposed by others.
The fact that none of our patients reported any discomfort resulting from
the use of magnetic devices and that no complications have been reported in
the literature supports the notion that low-intensity magnetic fields
produced by permanent magnets or electromagnetic devices are biologically
safe....
CONCLUSIONS
The delivery of static magnetic fields through a magnetized device directly
applied to a pain trigger point or to a localized painful area results in
significant relief of pain within a short period of time (less than 45
minutes in our study) and with no apparent side effects. Based on the
results of this study and reports in the literature of the effect on people
with arthritis, it appears that magnetic field energy may be useful in the
management of pain in individuals with other types of impairments that are
commonly treated in primary care settings.
Specific issues that need
to be explored through new studies are: (1) dose-response to pain relief;
(2) duration of the effect after applying a static permanent magnetic field;
(3) identification of the local and central effects of magnetic fields on
the same pain area; (4) effect of the simultaneous application of magnets on
several pain trigger areas; (5) possible difference of effect of various
sizes and shapes of a magnetized device; and (6) cost effectiveness of pain
management with magnetic fields versus traditional pharmacologic or physical
therapy modalities.
Acknowledgments: The
authors are indebted to Valory Pavlik, PhD, for her assistance in the study
design, the statistical analysis of the results, and the review of the
manuscript. Mandy Smith, PT, contributed to the selection of patients. Mrs.
Christine Toronjo was responsible for the processing of data.
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Supplier
BIOflex® Medical Magnetics,
Inc., 3370 NE 5th Avenue, Oakland Park, FL 33334.
From the Department of
Family and Community Medicine and the Department of Physical Medicine and
Rehabilitation (Dr. Vallbona) and the Department of Molecular Biology and
Biophysics (Drs. Hazlewood, Jurida), Baylor College of Medicine, Houston,
TX.
Submitted for publication
February 12, 1997. Accepted in revised form April 11, 1997.
No commercial party having
a direct financial interest in the results of the research supporting this
article has or will confer a benefit upon the authors or upon any
organization with which the authors are associated.
Reprint requests to Carlos
Vallbona, MD, Baylor College of Medicine, One Baylor Plaza, Houston, TX
77030.
©1997 by the American
Congress of Rehabilitation Medicine and the American Academy of Physical
Medicine and Rehabilitation
0003-9993/97/7811-4378$3.00/0
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