Sunday, January 3, 2010

Low-Level Laser Therapy Reduces Neck Pain

An extensive review of the literature found that low-level laser therapy can effectively reduce nonspecific acute neck pain immediately after treatment and for several months in patients with chronic neck pain. In some cases there may be advantages of this approach over traditional pharmacotherapies, if laser therapy is properly applied.

Low-level laser therapy (LLLT) is a relatively uncommon, noninvasive treatment for neck pain, in which nonthermal, or “cold,” laser irradiation is applied to sites of pain. An international group of researchers conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to assess the efficacy of LLLT in neck pain [Chow et al. 2009]. Their search included all studies prior to August 2008 comparing efficacy of LLLT with placebo (eg, sham laser) or with active control (eg, exercise) in acute and chronic, nonspecific neck pain; studies involving diagnosed pathological conditions (eg, rheumatoid arthritis, neurological disease) were excluded.

There were 16 RCTs identified for evaluation (14 of good quality), encompassing a total of 820 patients. In acute neck pain, evidence was limited to two trials with mixed results, showing that patients were around 70% more likely to experience reduced pain following LLLT as compared with placebo (relative risk [RR] 1.69 [95% CI 1.22-2.33]). Five trials of LLLT for chronic neck pain showed a 4-fold improvement with this therapy (RR 4.05 [2.74-5.98]). In 11 trials reporting changes in VAS scores (100 mm visual analogue scale) the average baseline pain was roughly 60 mm and LLLT reduced pain intensity by a third, or about 20 mm. Seven trials provided longer-term followup data after completion of treatment for chronic pain, and initial pain relief persisted during 3 months with a mean VAS reduction of 22 mm. LLLT appeared effective regardless of the level of baseline pain, symptom duration, age, or sex, and 5 studies also demonstrated a reduction in disability following LLLT. Only half of the trials reported data regarding adverse events associated with LLLT, but those noted were mild and not different from placebo.

Clinical Concepts: Part of what makes LLT so attractive is its ease of use and painless application, since it does not promote heat like a surgical laser. The exact mechanism of how LLLT reduces pain is unclear, but the authors speculate that it could involve reducing inflammation, stemming nerve conduction of painful stimuli, and/or ameliorating muscle fatigue. In the past, LLLT has demonstrated mixed clinical efficacy for low back pain and rheumatoid arthritis; however, the current analysis of LLLT for neck pain demonstrated a clinically significant 33% reduction in pain [see our prior blogpost discussing clinical significance in pain trials].

The wide range of data in this current review suggests that the effectiveness of LLLT may depend on the experience and skill of the practitioner in selecting an effective LLLT protocol in terms of wavelength, energy, time variables, and irradiation points (see below). Despite this, the authors assert that the long-term results of LLLT contrast favorably with those for nonsteroidal antiinflammatory drugs or other analgesic agents, for which side effects are common and pain relief ends rapidly when drug use is discontinued. Furthermore, added benefits may be gained when LLLT is used in the context of a regular exercise and stretching program.

Some Technical Notes: The application of LLLT is complicated by multiple variables, such as the wavelength of the laser, its energy, and duration of application, which can produce different effects in different human tissues. In the current study, these variables were not consistent across trials; for example, the energy delivered per treatment point on the neck ranged from 0.06 to 54 Joules and the irradiation duration lasted between 1 and 600 seconds. A dose-response effect was associated with LLLT, but the accumulated data could not provide definitive guidance regarding the best practice for LLLT. Still, the authors propose from their analysis that the optimum mean dose per point for wavelengths of 820–830 nm (nanometers) was 5·9 Joules, with an irradiation time of 39.8 seconds, and for 904 nm, 2.2 Joules delivered for 238 seconds. Along with that, when treating neck pain with LLLT, irradiation of known trigger points, acupuncture points, tender points, and symptomatic zygapophyseal joints is advisable, they note.

Reference: Chow RT, Johnson MI, Lopes-Martins RAB, Bjordal JM. Efficacy of low-level laser therapy in the management of neck pain: A systematic review and meta-analysis of randomized placebo or active-treatment controlled trials. Lancet. 2009;374(9705):1897-1908 [abstract here]. (At the time of this posting a courtesy PDF of the full article was available here, but this may be discontinued.)