In general terms, combination therapy involves the simultaneous application of ultrasound (US) with an electrical stimulation therapy. In Europe, Diadynamic Currents are frequently utilised, but in the UK, US is most often combined with bipolar Interferential Therapy (IF).
There is a significant lack of published material in this area. And much of the information herein is anecdotal or based on the experience of those who use the modality frequently. Broadly, the effects of the combined treatment are those of the individual modalities. There is no evidence at present for any additional effects which can only be achieved when the modalities are used in this particular way.
It is suggested that:
- by combining US with IF, the advantages/effects of each treatment modality can be realised, but lower intensities are used to achieve the effect.
- the accommodation effects that accompany IF treatment are reduced (or even eliminated)
The main advantages on such a combination are said to be:
- in localising lesions (especially chronic) i.e.diagnostic use
- in ensuring accurate localisation of US treatment- to provide increased accuracy/effectiveness in treating deeper lesions
- in treating trigger points
Exposure of a peripheral nerve to US reduces the membrane resting potential by increasing its permeability to various ions (especially Sodium (Na+) and Calcium (Ca++). By virtue of this adjusted permeability, the nerve membrane is taken closer to its threshold (the point where it depolarises, though doesn’t usually make the nerve fire. The simultaneous application of the Interferential current through the nerve induces the depolarisation potential, though it will take a smaller current than usual to achieve this due to the potentiation effect of the ultrasound.
This can easily be demonstrated. If both the US and IF are applied, and during the application, the US is turned down to zero, the sensation produced by the IF will diminish even though the IF intensity has not been changed. The intensity of the IF sensation returns when the US is turned up again.
The combination of US with IF appears to give rise to less adverse treatment effects than are associated with the combination of US with Diadynamic Currents, or other electrical stimulations. It has also been suggested that a greater effective treatment depth can be achieved with the US - IF combination though there is no direct evidence for such a claim..
In summary, it would appear that by combining the two treatment modalities, none of the individual effects of the treatments are lost, but the benefit is that lower treatment intensities can be used to achieve the same results, & there are additional benefits in terms of diagnosis & treatment times.