Short–Wave Diathermy (SWD)
Short–wave diathermy is the application to the tissues of electrical fields which oscillate at a frequency of 27.12KHz and have a wavelength of 11.06M (condenser field method). The oscillating fields produce distortion of molecules, rotation of dipoles and vibration of ions. When the inductothermy cable is used there is a current oscillating in the cable which produces an electromagnetic field, which in turn induces eddy currents (and therefore ionic vibration) in the tissues. The movement of the molecules and ions generates heat within the tissues. Tissues of high impedance are bone, fat, fascia and other fibrous tissue structures. Tissues of low impedance are blood, lymph and muscle. If the oscillating electrical field is applied in parallel with the tissues, then those with low impedance will tend to be heated more, whereas the tissues of high impedance will be heated if they are in series with the field. The superficial tissues of low impedance tend to be heated when the inductothermy cable is used.

Short–wave diathermy can be used to treat both deep and superficial lesions. Large areas can be treated and it is useful for soft–tissue injuries, degenerative and inflammatory arthropathies, slow healing wounds, sinusitis and conditions of the deep–seated pelvic structures.

Short–wave diathermy may be pulsed (one form of pulsed electromagnetic energy–PEME). This mean power is, therefore, considerably reduced. The main difference is that during the relatively long rest period, the heat developed is dispersed by the circulation and the treatment is referred to as ‘non–thermal’. Pulsed SWD is particularly useful for giving pain relief in acute soft–tissue lesions and arthropathies. In crush injuries or trauma which results in excessive swelling, pulsed SWD obtains marked reduction in local edema. For acute lesions the recommended dosage is 65 us at 100 pps for 15 minutes.

Progression of treatment, if necessary, involves increasing pulse widths and frequencies. The possibilities of varying the treatment depend upon the machine used. In wounds treated with pulsed SWD there is increased organization of connective tissue and growth of epithelial tissue so that healing is accelerated. Areas with metal in the field which are a contraindication to continuous short wave may be treated with pulsed SWD.