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7 Articles in Volume 4, Issue #5
A Case For Intractable Pain Centers: Part 1
Co-Existing Psychological Factors
Cold Lasers in Pain Management
Diagnosing Diffuse Aches and Pains
Occipital Nerve Block for Cervicogenic Headaches
Opioid Therapy in Chronic Non-cancer Pain Management
Reflex Sympathetic Dystrophy (RSD)

Cold Lasers in Pain Management

Low energy laser therapy has been shown — at appropriate dosimetry, wavelength, duration, and site-specific application — to reduce tissue pain/ tenderness, normalize circulation patterns in tissue trauma, and increase collagen formation in wounds.
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Laser practitioners also apply this mode of treatment to various forms of tendinopathy including medial and lateral epicondylitis, plantar fascitis, rotator cuff and various other enthesopathies. All these conditions have been studied using laser as the primary form of treatment with varying degrees of success. There is such a wide variation in treatment response noted in these studies which is consistent with the wide array of dosage parameters used, not to mention wavelength choice, which is crucial for proper penetration depth. The majority of “no difference” trials have used a helium-neon laser source which has the least penetration power of any laser coupled with low power density capability. The end result is a negligible energy density and not a high probability of a therapeutic effect. Unfortunately, many clinical trials have been accidentally undermined from the start with poor dosage selection parameters. Investigations utilizing higher energy densities (>3J/cm2) were more likely to show a statistically significant difference between treatment and control groups.

Wound Healing. There is considerably more and better research support for the use of cold laser application in wound healing perhaps than any other medical condition discussed so far. In 2004, Woodruff et al published a meta-analysis on the subject and concluded that laser therapy is an effective tool for promoting wound repair.28 This conclusion draws support from many others who have investigated the use of laser in wound healing. One of the primary laser mediated physiological benefits to a wound is that a laser will increase the amount of collagen formation in the irradiated region. Laser has demonstrated to have positive effects on both macrophage and fibroblast cell lines.29 A more recent finding has been that certain laser wavelengths, such as the 630nm (helium-neon), has an inhibitory effect on certain bacterial strains including E. coli.30 This has valuable implications for the treatment of infected wounds. There have been quite a number of significant in vitro and in vivo findings as they pertain to cold laser usage that would help explain many of the empirical or observational reports that are pervasive in the literature today. Nicola et al found that laser biostimulation of rat femurs over the course of 8 days using a 660nm wavelength and dosing the lasing site at 10J/cm2 had a positive effect on bone cell activity, both resorption and formation, around the site of repair without changing bone structure.31 Similar findings were reported by other researchers who also reported increased trabecular bone growth, along with a hastened collagen matrix organization.7 Other cell lines including mogenic types including muscle satellite cells have also been shown to be affected by LLLT, specifically laser’s ability to increase the number of satellite cells around isolated single muscle fibers.32 These findings are bolstered by the NASA studies on light emitting diodes (LEDs) as reported by Whelan et al concluding that light therapy has been found to increase fibroblasts, osteoblasts, skeletal muscle cells and human epithelial cells.33 Their work was performed primarily on rodents but the authors feel that it is only a matter of time before similar findings are corroborated in human studies.

A special note regarding the role of NASA in laser research would be appropriate given the scope and magnitude of this agency’s contribution to the role of light therapy thus far. Studies on cells exposed to varying levels of gravity have concluded that human cells require gravity to stimulate growth. This requirement poses significant challenge to those astronauts involved in long term space flight. NASA developed LEDs as a way in which to stimulate the basic but essential mitochondrial processes of each cell so as to provide not only tissue healing, but also to minimize bone and muscle atrophy. NASA views LED technology as a promising alternative to medication and surgery whereby the biostimulation of natural regenerative mechanisms would be the primary goal. In regards to wound healing, the NASA project has demonstrated that wavelengths between 670 and 880nm at total energy levels of 4-8J/cm2 applied at power densities of 50mW/cm2 are optimal parameters.34

Conclusion

There continues to be a pressing need for properly controlled randomized clinical trials in the field of laser therapy. It is not difficult to see that these devices could impart a powerful placebo effect in even the most skeptical patient. The research base regarding lasers is only as good as the methods and designs implemented in the individual trials comprising the base. There is more reason to be optimistic than not however, since more product interest will necessitate an increased push for better research validation. Those practitioners who have used cold lasers on a regular basis will in many cases remark that “absence of evidence is not evidence of absence.” I would have to agree in the case of cold laser. For the most part, many of the authors who published manuscripts that found “no difference” between control and treatment groups have stated in their conclusion that more research is recommended, and furthermore, more research is warranted. The in-vitro and in-vivo studies clearly have demonstrated that dose and wavelength are critical in achieving therapeutic goals, yet many reports fail to fully describe both parameters. This is not a failure of the modality under study, it is a flaw in the study design. Cold lasers are slowly working their way to becoming commonly used therapeutic modalities of choice in the treatment of painful conditions of musculo-skeletal origin. More work needs to be done in elucidating human dose-response relationships and condition-specific optimal wavelength selection. Ultimately, it will be the day to day performance of cold lasers on patient problems that will have the most impact in deciding the clinical place cold lasers will occupy in the therapeutic milieu, quite apart from the research support. From this perspective, the introduction of cold laser into the field of pain management could supercede the growth pattern of many of our more contemporary modalities.

Last updated on: January 28, 2012
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