Objective: To compare the effectiveness of application of low-level laser therapy (LLLT) to trigger points and traditional acupoints for patients with cervical myofascial pain syndrome (MPS).

Design: A single-blinded, randomized, placebo-controlled trial Setting: University rehabilitation hospital Participants: One hundred and twenty one patients with cervical MPS Intervention: The investigators performed this experiment using low level 810-nm gallium aluminum arsenide (Ga-Al-As) laser. One hundred participants were randomly assigned to four treatment groups, including (1) acupoint therapy (2) acupoint control (3) trigger point therapy and (4) trigger point control groups.

Main Outcome measures: The investigators evaluated the patient's visual analogue scale (VAS) pain scores, pressure pain threshold and cervical range of motion (ROM) before and after the therapy.

Low level laser therapy (LLLT) has been promoted since 1960s. It was clinically applied on neurological, musculoskeletal and soft tissue disorders, with the effects such as acceleration of wound healing, edema reduction in human flexor tendon injuries, improvement of morning stiffness, and pain relief in rheumatoid arthritis and lateral epicondylitis. As for relief of musculoskeletal pain, however, the effect of LLLT is controversial. Some studies reported that LLLT was a safe and effective treatment for relief of musculoskeletal pain, while others considered LLLT as ineffective in treating certain musculoskeletal diseases.

LLLT has been used to stimulate traditional acupoints, which is denoted as laser acupuncture. In addition to pain relief, laser acupuncture has been reported to be effective in a variety of disorders such as intractable hiccups,enuresis, as well as weight reduction. Nevertheless, the underlying mechanisms and modes of application of laser acupuncture remain unclear.

There has been evidence that needle acupuncture on traditional acupoints or trigger points may ease neck pain. However, needle acupuncture has some limitations because it is an invasive procedure with risk of infection or pneumothorax. Besides, some patients were not able to tolerate the discomfort from needle manipulation during acupuncture therapy.

LLLT is a type of non-invasive painless therapy and hence a good alternative to needle acupuncture. LLLT has been used to treat neck pain since 1981 and demonstrated significant reduction of pain intensity and improvement of cervical range of motion (ROM) in patients with cervical myofascial pain syndrome (MPS). In most of the studies on LLLT and cervical MPS, trigger points were chosen as the application area domain for LLLT. However, there is no report yet to compare the effectiveness of LLLT on trigger points and traditional acupoints.

In the present single-blinded, randomized, controlled study, the investigators aimed to investigate the effectiveness of application of LLLT to the trigger points and traditional acupoints in patients with cervical MPS. The outcome measurement was pain relief and the improvement of cervical ROM, on which the findings could provide in-depth understanding of the therapeutic mechanism of LLLT and further allow more flexible options of clinical application.

Inclusion Criteria:

1. complaint of regional pain in the neck,
2. presence of a palpable taut band,
3. presence of a tender spot along the length of taut ban, and
4. reproduction or enhancement of the clinical symptoms by compression of the active trigger point

Exclusion Criteria:

1. cervical spine lesion, such as radiculopathy or myelopathy,
2. fracture or surgery of cervical spine,
3. cervical spine instability, and
4. cognitive deficits or psychiatric illness