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Written by Robert J Lewis
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Two treatment methods I have been asked about are Ultrasound and TENS.
Ultrasound is mechanical vibration, often described as a micro-massage, and therefore not strictly electrotherapy, although it is usually referred to under this heading. Ultrasound gives vibrations which are of a higher frequency than sound waves, beyond hearing range, and therefore fall into the ultrasonic category. Most therapeutic ultrasound units come in frequencies of either 1MHz (one million cycles per second) or 3MHz (three million cycles per second) or a combination of both. Ultrasound frequency of 1MHz penetrates more deeply than 3MHz. An ultrasound beam can be pulsed or continuous. Continuous ultrasound produces a lot of heat in the tissues and is used for chronic injuries or large areas. Pulsed ultrasound produces less heat but still produces the same micro-massage effects, and is mostly used for acute conditions. It is also used in areas where the bone is close to the surface to avoid overheating and possible tissue damage.
Ultrasound requires a medium for transmission, and this usually takes the form of a coupling gel which is put on the skin to form a coupling between the ultrasound head that delivers the beam and the skin. Body parts can also be treated with ultrasound under water. To avoid refraction of energy, the treatment head of the unit must be held perpendicular to the skin, and kept moving to avoid concentration of energy on one area of tissue. Ultrasound is not usually applied on the day of the injury, although some therapists believe it is safe to use 3MHz, as there is the possibility of the micro-massage causing further bleeding and therefore tissue damage. It is certainly best not to overdose, and therefore the intensity of the beam for an acute injury would start at around 0.25Wcm² for 3-4 minutes, twice a day. Progression should then be made by increasing the time and decreasing the frequency of treatment, with a maximum treatment time of 10-15 minutes.
Another possible guide to considering treatment time, particularly with larger areas, is 2 minutes of treatment for every 10cm² of surface area covered. Ultrasound should be painless, if pain is felt treatment should be stopped, the intensity could be too high or pain may indicate a stress fracture is present.
The micro-massage and heat produced by the ultrasound relieves pain due to its effect on sensory nerve endings. It causes smooth muscles surrounding blood vessels to relax, improves circulation and aids the process of healing.
Ultrasound has been used in the treatment of:
· Traumatic and inflammatory
conditions
· Pain relief (example – herpes zoster, low back pain)
· Chronic rheumatoid and arthritic conditions
· Softening scar and excessive fibrous tissue
· Healing of chronic ulcers of pressure sores
· Ligament/muscle injuries
· Sprains and strains
· Frozen shoulder
· Bursitis
Dangers of ultrasound
Burns could occur; therefore ultrasound should not be used in areas where feeling is reduced. Other contraindications include:
· Over the cardiac
region
· Malignant and
precancerous tissue
· Thrombosis and
phlebitis
· Reproductive
organs
· Abdomen of
pregnant women
· Acute infections
· The brain and
eyes
· Areas at risk of
haemorrhage
Transcutaneous Electrical Nerve Stimulation (TENS)
Pain thresholds vary and are recognised differently by individuals. The central nervous system adjusts and regulates all sensations before they reach conscious level. The pain gate theory (Melzack and Wall, 1965) suggests that the perception of pain is controlled by a ‘gate’ which can be opened or closed. This ‘gate’ can be controlled by electrical stimulation, which can be effective in reducing pain. The electrical pulses necessary can be administered by a TENS machine. These machines are readily available and consist of a control unit and two electrodes which are applied to the skin. The position of the electrodes varies and may be above and below the painful area or over the affected nerve. The electrodes should not be placed over areas with little or no feeling (anaesthetic areas). By adjusting the pulse and its frequency it is usually possible to find a setting that produces a tingling sensation and gives almost instant pain relief.
TENS appears to be more effective in treating older injuries and persistent pain, and should not be used in recent injuries to allow training or competitive activities to continue, as it may mask the condition which could result in more severe injury.
Uses of TENS include:
· Severe, longstanding pain caused by a variety of conditions
· Burning pain felt in a limb where there has been partial damage to the sympathetic and somatic sensory nerves.
· Searing pain felt in the distribution of branches of the trigeminal nerve in the face
· Chronic leg, back and neck pain
Contraindications include:
●Anyone with a pacemaker
●Anyone with abnormal cardiac rhythm
●Treating areas around the carotid sinus and mouth
To be effective, TENS needs prolonged use, even 24 hours a day, sometime for several weeks or months.
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