Low and medium Frequency Electrotherapy - Implox
Low and medium Frequency Electrotherapy - Implox
Low and medium Frequency Electrotherapy - Implox
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2 PAIN CONTROL AND SELECTIVE STIMULATION<br />
2.1 Introduction<br />
Pain reduction can be achieved in many different ways. It is beyond the scope of this book to list all the means<br />
available. However, we shall discuss a number of the theories that have been advanced to explain the underlying<br />
mechanism of the pain reduction effect. With respect to electrotherapy, it will become clear that phase duration,<br />
frequency <strong>and</strong> amplitude play an important role.<br />
2.2 Pain theories<br />
Enraf-Nonius electrotherapy equipment offers a range of current types that relate to the present-day theories<br />
explaining the reduction of pain by electrostimulation. The following three theories are important.<br />
2.2.1 Gate control theory (Melzack <strong>and</strong> Wall)<br />
This theory (7.21) is based on the assumption that stimulation of the thick myelinated nerve fibres will cause a neural<br />
inhibition at the spinal level. This inhibition will block the transport of pain stimuli to the brain via the thin nonmyelinated<br />
nerve fibres.<br />
Type II <strong>and</strong> III<br />
nerve fibres<br />
+<br />
Central Control<br />
+<br />
Action<br />
system<br />
Substantia<br />
Gelatinosa<br />
-<br />
Type IV<br />
nerve fibres - +<br />
GATE CONTROL SYSTEM<br />
-<br />
Transmision<br />
cell<br />
(Lamina<br />
V)<br />
Fig. 1.<br />
Diagrammatic representation of the Gate-Control-Theory (Melzack <strong>and</strong> Wall).<br />
In other words, selective stimulation of the type II <strong>and</strong> type III nerve fibres will create a feed-forward inhibition of the<br />
stimuli arising in the type IV nerve fibres. In this case, stimulation of the type IV nerve fibres is undesirable.<br />
Although the existence of a central influence is now also considered (see paragraph 2.2.2), the Gate control theory is<br />
still regarded as one of the most important starting points in pain suppression (7) .<br />
Category Efferent Afferent Conductionspeed (m/s) Diameter<br />
(µm)<br />
A-a I 70-120 12-22<br />
Thick A-ß II 50-70 5-12<br />
A-? II 30-50 5-12<br />
A-d III