Ultrasound: effectiveness of treatments given under water.

The purpose of this study was to determine whether ultrasound treatments given with a limb immersed in tap water are as effective in heating the tendons overlying a superficial bony prominence as ultrasound treatments given with the applicator and coupling agent in direct contact with the limb. The lateral epicondyle of a pig was treated with the applicator in contact with the limb and with the limb immersed in a water bath with the applicator held 2cm from the skin surface. With a thermocouple inserted into a 20-gauge needle, the temperature elevations in the tendon of the extensor muscles originating at the lateral epicondyle were measured. It was found that the temperatures of the tendons rose into the therapeutic range when the ultrasound was applied directly to the skin surface, but not when treatment was given under water. It is therefore preferable to give ultrasound treatments with the applicator in direct contact with the subject rather than in an immersion bath with tap water as the coupling agent.