Low and medium Frequency Electrotherapy - Implox

3.4.2 Application of interferential therapy
Application point for therapy may lie on the surface of the body, or in deeper-lying tissues.
Due to the higher frequency and the absence of galvanic effects, medium-frequency alternating current is suitable for
treatment of deeper-lying tissues (muscles, tendons, burs or periosteum).
The selected application method will depend on the application points. The application methods are as follows:
• pain-point or trigger-point application,
• nerve application;
• (para) vertebral application;
• transregional application;
• muscular application (see Chapter 5).
The present range of Enraf-Nonius equipment offers five methods for interferential therapy:
1. two-pole (bipolar) method;
2. four-pole (tetrapolar) method (Classic Interferential without vector);
3. four-pole method with Dipole vector (manually adjustable);
4. four-pole method with Dipole vector (automatic);
5. four-pole method with Isoplanar vector
3.4.2.1 The two-pole method
In this method two electrodes are used and superimposition of the two alternating currents takes place within the
equipment. The current leaving the equipment is a fully modulated alternating current.
In the two-pole method the modulation depth is always 100% (Fig. 15).
Fig. 15.
Bipolar interferential therapy
3.4.2.2 The four-pole method (Classic Interferential)
In this method four electrodes are used, and two unmodulated currents leave the equipment. Interference occurs
where the two currents intersect within the tissue.
The modulation depth depends on the direction of the currents, and can vary from 0 to 100%. 100% modulation
depth only occurs at the diagonals (and hence at the intersection) of the two currents.
This is, of course, a theoretical situation, based on the assumption that the tissue is homogeneous. In the real
situation, the tissue is heterogeneous, so that the intensity of the two channels has to be used to get the 100%
modulation depth (Fig. 16). This can also be used to compensate for differences in sensation occurring under the
electrode pairs.
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