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Ultrasound and Physical Therapy: An Introduction
Jim Doree
Ultrasound is a therapeutic modality that has been
used by physical therapists since the 1940s. Ultrasound is applied using
a round-headed wand or probe that is put in direct contact with the
patient's skin. Ultrasound gel is used on all surfaces of the head in
order to reduce friction and assist in the transmission of the ultrasonic
waves. Therapeutic ultrasound is in the frequency range of about 0.8-1.0
MHz.
The waves are generated by a piezoelectric effect caused by the vibration
of crystals within the head of the wand/probe. The sound waves that
pass through the skin cause a vibration of the local tissues. This vibration
or cavitation can cause a deep heating locally though usually no sensation
of heat will be felt by the patient. In situations where a heating effect
is not desirable, such as a fresh injury with acute inflammation, the
ultrasound can be pulsed rather than continuously transmitted.
Ultrasound can produce many effects other than just the potential heating
effect. It has been shown to cause increases in tissue relaxation, local
blood flow, and scar tissue breakdown. The effect of the increase in
local blood flow can be used to help reduce local swelling and chronic
inflammation, and, according to some studies, promote bone fracture
healing. The intensity or power density of the ultrasound can be adjusted
depending on the desired effect. A greater power density (measured in
watt/cm2 is often used in cases where scar tissue breakdown is the goal.
Ultrasound can also be used to achieve phonophoresis. This is a non-invasive
way of administering medications to tissues below the skin; perfect
for patients who are uncomfortable with injections. With this technique,
the ultrasonic energy forces the medication through the skin. Cortisone,
used to reduce inflammation, is one of the more commonly used substances
delivered in this way.
A typical ultrasound treatment will take from 3-5 minutes. In cases
where scar tissue breakdown is the goal, this treatment time can be
much longer. During the treatment the head of the ultrasound probe is
kept in constant motion. If kept in constant motion, the patient should
feel no discomfort at all. If the probe is held in one place for more
than just a few seconds, a build up of the sound energy can result which
can become uncomfortable. Interestingly, if there is even a very minor
break in a bone in the area that is close to the surface, a sharp pain
may be felt. This occurs as the sound waves get trapped between the
two parts of the break and build up until becoming painful. In this
way ultrasound can often be used as a fairly accurate tool for diagnosing
minor fractures that may not be obvious on x-ray.
Some conditions treated with ultrasound include tendonitis (or tendinitis
if you prefer), non-acute joint swelling, muscle spasm, and even Peyronie's
Disease (to break down the scar tissue). Contraindications of ultrasound
include local malignancy, metal implants below the area being treated,
local acute infection, vascular abnormalities, and directly on the abdomen
of pregnant women. It is also contraindicated to apply ultrasound directly
over active epiphyseal regions (growth plates) in children, over the
spinal cord in the area of a laminectomy, or over the eyes, skull, or
testes.
About the Author
Jim received his physical therapy
degree in 1997 from the University of Alberta in Edmonton, Alberta,
Canada. Please see more information and articles on his web site at
'The Physical Therapy Web Space' (http://automailer.com/tws/). View
this and other articles related to Physical Therapy at The Physical
Therapy Web Space.
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