Ultrasound therapy is a form of electrotherapy treatment therapists use to treat soft tissue injuries. It involves passing high frequency sound waves into soft tissue. Here we explain how it works, the benefits and contraindications.
How does ultrasound work?
The metal head of an ultrasound machine produces mechanical vibrations. as a result, this produces sound waves (like a buzzing). However, the frequency of these sound waves is so high that humans cannot hear them.
When the sound waves come into contact with air it causes a dissipation of the waves. Therefore, therapists use a special ultrasound gel on the skin so the sound waves transmit into your body. Ultrasound therapy also works underwater because ultrasound waves can travel through water.
As the treatment head moves over the skin the energy from the waves transmits into your soft tissues.
Effects of therapeutic ultrasound
Some people dispute the effects of therapeutic ultrasound. To date, there is still little evidence explaining how ultrasound causes a therapeutic effect in injured tissue. Nevertheless, practitioners worldwide continue to use this treatment modality relying on personal experience. Below are a number of the theories by which ultrasound causes a therapeutic effect.
As the ultrasound waves pass from the treatment head into the skin they cause the vibration of the surrounding tissues, particularly those that contain collagen. This increased vibration leads to the production of heat within the tissue.
In most cases, patients cannot feel this themselves. This increase in temperature may cause an increase in the extensibility of structures such as ligaments, tendons, scar tissue, and fibrous joint capsules. In addition, heating may also help to reduce pain and muscle spasm which promotes healing.
Effects on the inflammatory and repair processes:
Ultrasound therapy may reduce the healing time of certain soft tissue injuries by accelerating the the inflammatory process (by attracting more mast cells to the site of injury).
This may cause an increase in blood flow which is beneficial in the sub-acute phase of tissue injury. This is one reason not to use Ultrasound immediately after injury.
Ultrasound may also stimulate the production of more collagen which is the main protein component in soft tissue such as tendons and ligaments. Hence ultrasound may accelerate the proliferative phase of tissue healing. It is thought to improve the extensibility of mature collagen and so can have a positive effect on fibrous scar tissue which may form after an injury.
Application of ultrasound:
Ultrasound is normally applied by use of a small metal treatment head which emits the ultrasonic beam. This is moved continuously over the skin for approximately 3-5 mins. Treatments may be repeated 1-2 times daily in more acute injuries and less frequently in chronic cases.
Ultrasound dosage can be varied either in intensity or frequency of the ultrasound beam. Simply speaking lower frequency application provides a greater depth of penetration and so is used in cases where the injured tissue is suspected to be deeply situated. Conversely, higher frequency doses are used for structures that are closer to the surface of the skin.
Contraindications of ultrasound
As ultrasound is thought to affect the tissue repair process and so it is also highly possible that it may affect diseased tissue in an abnormal fashion. In addition, the proposed increase in blood may also function in spreading malignancies around the body. Therefore a number of contraindications should be followed when using therapeutic ultrasound:
Do not use if the patient suffers from:
- Malignant or cancerous tissue
- Acute infections
- Risk of haemorrhage
- Severely ischemic tissue
- Recent history if venous thrombosis
- Exposed neural tissue
- Suspicion of a bone fracture
- If the patient is pregnant
- Do not use in the region of the gonads (sex organs), the active bone growth plates of children, or the eye.