Ultrasound is a therapeutic modality that has been used by chiropractors and 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 0.8-3.0 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.
A typical ultrasound treatment will take from 3-5 minutes depending on the size of the area being treated. 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), bursitis, 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.
Several different electrical stimulation devices exist, each producing different frequencies, waveforms, and effects. Electrical modalities include
- Transcutaneous Electrical Nerve Stimulation (TENS) (the most commonly used)
- Interferential Current (IFC)
- Galvanic Stimulation (GS)
Common Characteristics of Electrotherapy Stimulation
TENS, IFC, and GS all apply electrical stimulation to nerves and muscles via adhesive pads placed on the skin. These devices are powered by batteries, and some units have an adapter that allows powering from an outlet.
Side effects are rare, but include allergic skin irritation under the adhesive pads and transient pain from the electrical charge. Placing the pads over the heart or over pacemaker leads could conceivably cause cardiac arrhythmia; placing them over the throat could conceivably cause low blood pressure; and placing them over a pregnant uterus could conceivably cause fetal damage. Because of these risks, electrical stimulation over these areas should be avoided. Electrical stimulation should also not be applied over malignancies or infected areas.
High frequency stimulation, sometimes called “conventional”, is tolerable for hours, but the resultant pain relief lasts for a shorter period of time. Low-frequency stimulation, sometimes called “acupuncture-like”, is more uncomfortable and tolerable for only 20-30 minutes, but the resultant pain relief lasts longer.
TENS users should experiment with various electrode placements. Electrodes can be placed over the painful area, surrounding the painful area, over the nerve supplying the painful area, or even on the opposite side of the body. TENS users need to try the unit for several days with several electrode placements prior to deciding if it will be useful. A home trial for several days to weeks is preferable.
Interferential current is essentially a deeper form of TENS. In essence, IFC modulates a high frequency (4000 Hz) carrier waveform with the same signal produced by a TENS unit. The high frequency carrier waveform penetrates the skin more deeply than a regular TENS unit, with less user discomfort for a given level of stimulation. Deep in the tissues, the carrier waveform is cancelled out, resulting in a TENS-like signal deep under the skin.
Galvanic stimulation is most useful in acute injuries associated with major tissue trauma with bleeding or swelling. In contrast to TENS and IFC units, which apply alternating current, galvanic stimulators apply direct current.
Electrical stimulation is a type of physical therapy modality used to accomplish various tasks in physical therapy. If you have an injury or illness that causes pain or limited functional mobility, your doctor or PT may use electrical stimulation, or E-stim, as one part of your rehabilitation program.
Your doctor or physical therapist will use different types of electrical stimulation to accomplish different tasks. These may include:
- TENS: Transcutaneus electrical neuromuscular stimulation (TENS) is a physical therapy modality used to manage acute and chronic pain in physical therapy. Your PT will use TENS to decrease your pain by applying electrodes to your body over painful areas. The intensity of the electricity will be adjusted to block the painful signals traveling from your body to your brain.
- Neuromuscular electrical stimulation (NMES): NMES uses an electrical current to cause a single muscle or a group of muscles to contract. By placing electrodes on the skin in various locations the physical therapist can recruit the appropriate muscle fibers. Contracting the muscle via electrical stimulation helps improve the way your affected muscle contracts. The physical therapist can change the current setting to allow for a forceful or gentle muscle contraction. Along with increasing muscle function, the contraction of the muscle also promotes blood flow to the area that assists in healing. NMES can also be used to help decrease muscular spasm by artificially tiring your muscle in spasm, allowing it to relax.
- Russian stimulation: Russian stimulation is a form of electrical stimulation that can accomplish a similar task as NMES: to improve the way your muscles contract. Russian stimulation simply uses a different wave form that may be a little more comfortable for you to tolerate.
- Interferential current: Interferential current (IFC) is often used to decrease pain, decrease muscular spasm, or improve localized blood flow to various muscles or tissues. It is often used to decrease low back pain and muscular spasm. Interferential current typically uses 4 electrodes in a crisscross pattern. This causes the currents running between the electrodes to “interfere” with one another, and allows your therapist to use a higher intensity current while still maintaining maximum comfort for you.
Remember, many forms of electrical stimulation is a passive treatment; you are doing nothing while receiving the stimulation. Other forms, like NMES and Russian stim, require that you are active while the E-stim is in use.
Electrical stimulation should never be the only treatment you receive during physical therapy. Research indicates that active engagement in your physical therapy program – with or without electrical stimulation – yields the best results.