Another way to avoid adaptation is presented by electronic modulation
of intensity, frequency and pulse width. Manual frequency modulation
is well-known in the use of interferential current but will not be
discussed in this paper. Some patients don’t like the “on-off” burst
feeling, which makes modulation a good alternative.
From a theoretical point of view, three different possibilities can be
used in TENS (1.6.1 – 1.6.3). MET probably uses the same three
(1.6.4-1.6.6) as well, but they have a different underlying
explanation. Cleaning the skin prior to treatment or regularly wetting
the probes may be more important than the choice of electrodes.
Self-adhesive electrodes, whether they are carbon or silver, usually
are the easiest to use. In most cases, silver ones give the best
1.6.1 TENS: Local Electrode Placement
Since this paper is about back pain, the real local electrode position
isn’t really at stake. Electrodes cannot really be put on the
pathologic site. In knee or shoulder problems, where the injury or
disease is between the electrodes, the milliampere current could cause
side effects. In back problems, the pathology is deeper in the body,
at the joint or the disc. However, the possible negative effects from
milliampere currents on healing can not be denied (see 2.3). The most
suitable electrode types are carbon or silver ones.
Paravertebral Electrode Placement
If pain decrease is to be achieved on a gate-control basis, a
one-inch mistake can cause the treatment to have no effects at all.
According to endorphin release theory, any position that stimulates A
(- and C –fibers) will do the right thing. From a practical point of
view, a vertebral position, counting the spinous process (SP), will
always lead to correct electrode placement.
To avoid misplacement, the electrodes can be placed above and under
the SP. The stimulus reaches the medial ramus cutaneous of the spinal
nerve. In a few occasions, positions 1 or 2 inches lateral of the SP
may enhance the results, probably because it causes stretching effects
on the capsule of the facet joint. The intervertebral disc may be the
subject of comparable effects; i.e. some patients with nerve root
compression report more pain relief when electrodes are put on the
paravertebral muscles of the opposite side using intensities above
motor level. Again carbon or silver electrodes can be used.
TENS: Specific Electrodes Positions
Myofascial trigger points (MTP) and acupuncture points both require
specific knowledge. Though literature indicates that TENS can be used
on these, MET might be in a better position to treat trigger points.
Acupuncture points can also be used, of course, but these shouldn’t be
treated in a “cookbook way.” Acupuncture is mostly an art and can not
be left to inexperienced therapists. As to the type of electrodes, the
same remark can be made.
1.6.4 MET: Probe Electrodes
The electrode type makes a big difference and, as in TENS, specific
positions can give very good results. Probes can be used for shorter
treatments of two to 10 minutes. If longer treatment is needed, the
use of self-adhesive electrodes will be much easier. In MET, it is
very important to send the current through the injury site. Therefore,
probes should be held dorsal and ventral or left and right of the
trunk. Many positions are necessary for all kinds of back pain whether
it be an intervertebral disc or a facet joint problem. The probe
positions should describe a large “X” through the pathology.
1.7 Treatment Time
This is a very important parameter. Pain relief through gate-control
usually lasts only a few minutes after treatment. This is probably not
what the patient came for. Thus repeating the treatment several times
a day can solve this problem. Using the TENS device with larger pulse
widths to obtain pain relief through endorphin release will not be
much different. According to the literature, this effect may last up
to 60 minutes. Unless the patient is asked to switch on the machine
several times a day, the pain will return after this first hour.
Minor problems or almost cured injuries may need no more than 20 or 30
minutes of treatment. This can be done with the probes. If the patient
suffers more pain, a longer treatment will be required. In most cases
two to four hours will decrease the pain; and it is best to repeat
this every second day. Daily treatments can be used in severe cases,
but if side effects such as more pain occur, it is best to switch back
to treatment every other day.
Electrotherapy in the milliampere range can be used at three intensity
levels. Depending on the theoretical basis of pain decrease one can
use low, moderate or high intensity. Leading to possibilities known
as: low intensity/high frequency (enkephalin release), moderate
intensity/burst frequency (gate-control), high intensity/low frequency
Some authors conclude that there is no strict
relation between frequency/intensity and the opioid type. Anyway,
always give the patient good instructions about this. The effect may
be zero if the intensity is set at wrong level. All authors agree that
TENS is useless if the patient does not understand the information or
if there are sensitivity disturbances at the electrode site(s).