Trigger points are defined as hyperirritable areas of tenderness in a muscle that when pressed or pinched can cause local and/or distant referred pain (e.g., someplace else down the arm or leg). Trigger points can be active (currently already causing pain) or latent (only painful when pressed or pinched).
Trigger points are common in the neck, upper trapezius, hip, back, and buttock regions. These are areas where muscles often contract without relaxing causing a build up of tension. Over time, the muscle itself forms a taut band of tight, static tissue instead of elastic, flexible muscle. In the center of this taut band is a pinpoint area that when stimulated can cause the pain of a trigger point.
Physical therapists often treat this problem using a variety of techniques that may be noninvasive or invasive. Noninvasive approaches include massage, stretching, and ultrasound. Invasive treatments include dry needling and corticosteroid injections. Dry needling refers to using needles to stimulate the trigger point without actually injecting any medication or other substances.
In a recent study, physical therapists from Tehran University of Medical Sciences in Iran used three different treatments for latent trigger points of the upper trapezius muscle. There were four total groups all together (phonophoresis, pressure release, ultrasound therapy, control group). Participants in each group were all women who had a positive trigger point of the upper trapezius.
Phonophoresis is a way to use ultrasound to push a topical corticosteroid (antiinflammatory ointment applied over the skin) through the skin into the muscle. Pressure release is the application of sustained pressure to the trigger point until pain is reduced.
Ultrasound therapy is the same as phonophoresis but without the corticosteroid cream — just the sound waves applied over the surface of the skin but directed down toward the bone. The sound bounces back off the bone and creates heat to the muscle tissue. Of course, the control group received no treatment but was measured before and after just the same.
Before treatment, the physical therapist measured each woman’s pain level, pain pressure threshold (PPT), and neck range of motion. These same measurements were taken after treatment and compared for each group. Pain pressure threshold was measured using a special device called a dual inclinometer. Pressure was applied to the trigger point until pain was created. The amount of pressure required to elicit pain was recorded as the pain pressure threshold.
The results showed that the women in all three treatment groups had decreased pain, decreased pain pressure thresholds, and improved neck motion. The control group stayed the same without improvement in any area.
The phonophoresis and pressure release techniques yielded better results than the ultrasound. Phonophoresis outperformed pressure release. The mechanisms by which these treatments work to reduce the effects of trigger points aren’t entirely clear yet.
Some experts suggest the increase in blood flow to the area from phonophoresis helps clear out substances in the area that cause pain. Pressure release may help by lengthening the muscle fibers themselves. Once the pressure is removed, there is a release of antipain hormones (e.g., endorphins, enkephalins), thus blocking pain and making it possible to move once again. Ultrasound may not have been as effective as phonophoresis or pressure release because a pulsed form of ultrasound was used that does not generate any heat to improve circulation.
The authors concluded that phonophoresis and pressure release are both good treatment techniques to relieve the pain and loss of motion caused by trigger points of the upper trapezius muscle. Both treatment approaches are safe and effective providing relief of painful symptoms without adverse effects.