Interferential Current
According to John Revord, MD, a Physical Medicine & Rehabilitation doctor with NeuroSpine Center of Wisconsin, Interferential Current (IFC) is essentially a deeper form of TENS. In essence, IFC modulates a high frequency (4000 Hz) carrier waveform with the same signal produced by a TENS unit. The high frequency carrier waveform penetrates the skin more deeply than a regular TENS unit, with less user discomfort for a given level of stimulation. Deep in the tissues, the carrier waveform is cancelled out, resulting in a TENS-like signal deep under the skin.Anecdotal evidence suggests that the IFC units may be useful for patients who have not had relief from TENS.
Even though IFC devices are typically significantly more expensive than TENS units, Dr. Kenyon only recommends the use of IFC devices to achieve physiological therapeutic benefit which includes:
- An increase in localized blood flow which can improve healing by reducing swelling (the additional blood flowing through the area takes edematous fluid away with it) and as a result helps remove damaged tissue and bring nutrients necessary for healing to the injured area.
- The stimulation of local nerve cells that can have a pain reducing/anaesthetic effect due to potentially blocking the transmission of the pain signals (pain gate mechanism) or by stimulating the release of pain reducing endorphins (opiod mechanism).
- Some degree of muscle stimulation as muscle contraction can be achieved through external application of an electrical current, overcoming some of the muscle inhibition often caused by local injury and swelling.
The electrical current is applied to the affected area using four electrodes. The four electrodes are placed in such a way that the two currents produced cross each other in the affected area. For example, if it is a knee injury that is being treated, the two currents can be applied so that they cross deep within the actual knee joint itself. Where the two currents meet, they actually ‘interfere’ with each other; hence the name ‘interferential.’
Should the Patient Feel Interferential Current?
The patient should not feel any discomfort from the application of the interferential current but may also feel a massage like tingling sensation throughout the area being treated. This sensation may continue for a brief period following treatment as well. The intensity of the current should be increased within the patient’s comfort level. A stronger current will usually have a more beneficial effect but the intensity should not be turned up so high as to cause pain.
Interferential Current (IFC) Equipment on Shoulder
Safety and Contraindications
IFC has been used in physical therapy treatment for many years and has been proven to be very safe. However, use should be avoided on individuals with pacemakers and near the low back or abdomen of pregnant women. You should also avoid the use of this modality in a body part where there is any possible risk of metastasis.
