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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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Carpal Tunnel Syndrome. Although not as studied a clinical condition as other pathologies, this landmark cold laser investigation occurred at the Flint, Michigan GM plant when Anderson et al studied the effects of cold laser on carpal tunnel syndrome (CTS).14 In this particular study involving 119 subjects, half received sham laser plus physical therapy while the treatment group received real laser plus physical therapy. The results of this randomized,controlled and double blinded study were that there was a statistically significant treatment effect shown by the real laser group, furthermore, the authors stated that low level laser therapy combined with physical therapy (strengthening, ROM etc) improves functional measures of wrist-hand work performance and results in greater probability of return to work. Since that study was completed, others have followed with similar confirmations of lasers potential efficacy in the treatment of this insidious and economically costly occupational disease known as CTS. Dosages described by various investigators range from 2-10 joules of energy per point per treatment session with several key points usually comprising the total treatment area. As an example, Weintraub reports using 9 joules of energy over 5 points per session with a treatment course ranging from 7 to 15 sessions depending on individual patient response.15 Balmes et al applied a 5J/cm2 (energy density) dosage schedule to their patient sample (n=33) and found beneficial results as measured by sensory distal latency on EMG.16

Myofascial Pain and Trigger Points. The application of cold laser to myofascial syndromes is very common among photobiology specialists. These seemingly innocuous but sometimes debilitating tender and painful areas can be a cause for concern for many patients. There have been numerous therapies and treatments expounded for their TP eradication properties stemming from pharmacotherapy and injections to acupuncture and positional release techniques. Numerous studies have supported the benefits of cold laser application for musculo-skeletal pain and dysfunction caused by trigger points, a common source of localized myalgic pain. Laasko et al published a randomized, double blinded, placebo controlled clinical trial involving 41 patients with confirmed trigger points in the upper extremities.17 His treatment regimen included each subject receiving 5 treatment sessions (twice daily) using both a near infra-red (670nm) of 10mW average power and a far infra-red unit (820nm) of 25mW average power level. A total of 1 and 5J/cm2 respectively were used by these investigators. Their results supported a positive treatment response with both wavelengths, however the 820nm laser provided the greatest treatment effect.

Simonovic et al studied 243 subjects with confirmed trigger points and found very similar results with pain, tenderness, local muscle tautness, and amount of required pain medication all reducing significantly in his patient population sample.18 They used virtually identical wavelengths as Laasko et al including a helium-neon 632.8nm and an infra-red 820nm unit. They found that pain decreased by over 70% and concluded by endorsing LLLT as either an effective monotherapy and/or a very important adjunct.

These findings simply confirmed what was originally found in 1986 when one of the first studies examining the effectiveness of LLLT on the trigger point phenomenon appeared in the Journal of Physical Therapy. Snyder-Mackler et al reported that LLLT, even at what is recognized today as being at very low dosage (J/cm2), was effective in reducing pain and tenderness in their small sample group.19 This group of investigators utilized a relatively low powered helium neon laser with supposed minimal penetration capabilities and what we know today is optimally designed for more superficial scanning such as in decubitus ulcers and/or post injury tissue necrosis.

Subsequent studies seem to support the idea that laser therapy not only reduces pain/tenderness but may also act to normalize disrupted circulation patterns inherent in tissue trauma. Several studies have alluded to a noticeable temperature “adjusting” mechanism when LLLT has been used. In acute conditions Asagai et al noted that there was a noticeable cooling effect in the “hot zone” of an injury post laser application where inflammation was most pronounced.20 In contrast, the “peripheral zone” in injury, which is typically of lower temperature during inflammation, was seen to gradually rise by the same amount as the hot zone dropped (approximately 3C degrees) post lasing. The authors noted that consistent with these vascular changes confirmed by thermography, there was concurrent reduction in clinical signs of swelling/edema as well. In the treatment of chronic pain, Fukuuchi et al, using a higher power GaAlAs (semiconductor) laser with output of 100mW at a wavelength of 810nm, found that skin temperature rose significantly in the treatment group and not at all in the sham control group.21 Furthermore, 75% of the treatment group demonstrated improvement in pain and tenderness levels while only 4% of the control group improved. An increase in tissue temperature is an unusual finding given that soft or cold lasers are named as such for their non thermal effects. These positive outcome results are similar to those of Salansky et al who also showed that when laser was added to a treatment regimen consisting of therapeutic exercise and spinal adjustments for treatment of whiplash injury, the therapeutic results are superior than treatment consisting of exercise and spinal adjustments alone.22

Dosimetry Note. It is a generally accepted laser principle that the more chronic an area, the greater the energy required to cause a therapeutic effect. Conversely, the more acute the problem, the less energy used to irradiate the region. The amount of treatment time per point will vary depending on the average power rating of the lasing device being used. This is where a more powerful laser has the advantage of being able to saturate an area with light energy at a faster rate leading to considerably shorter treatment duration times. This has implications for clinical efficiencies when treating multiple patients throughout the day. As an applied example, if a clinician intends to irradiate an area with a target dose of 1 joule and we compare 3 different laser power output levels, we find the following; a 1mW laser beam would require 1000 seconds to achieve this dosage, whereas a 10mW laser would require 100 seconds, and a 50mW laser approximately 20 seconds to make dosage. If the target dose is closer to 10 joules of energy, we can see that these irradiation times are multiplied by a factor of 10. If we are treating multiple trigger points (5-6) we now further multiply the total time by 5 or 6 times. It is this scenario that has laser manufacturer’s scrambling to develop more powerful laser systems.

Last updated on: January 28, 2012
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