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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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There are three essential components to a laser system, those being; a lasing medium, an energy source, and the mechanical structure of the laser. We will confine this discussion to cold lasers in the near to far infra-red range of the electromagnetic spectra (visible red to invisible red). The lasing medium is a material which is capable of being excited by an outside source and absorbing that energy produced when electrons are excited from one level to another. Lasing media can be gaseous, liquid, solid crystal or semiconductor in nature. Helium-neon is an example of a gas medium laser while gallium aluminum arsenide is an example of a semiconductor medium laser. The selection of the lasing medium is important since this will dictate the wavelength of the device’s output and ultimately determine the color of the beam and depth of penetration.

The energy source is the next component that needs description however, invariably the energy source most common to systems used in pain management will be electrical power. Lasers operating in the 632 (visible red) to 1000nm (far infra-red) wavelength and used to treat pain and myofascial syndromes will typically be driven by a local main power supply.

Early therapeutic lasers utilized two wavelength specific mirrors mounted parallel to each other and a fixed distance from each other ( a multiple of the lasers wavelength) so as to reflect only a certain wavelength range. This mechanical structure holds true today for many lasers except those using semiconductor technology. These units use polished diodes and special lenses to both selectively emit and concentrate the laser beam consisting of light particles or photons.

Laser light distinguishes itself from other forms of light in that it is monochromatic, directional and coherent. The spectral emission (bandwidth) from a laser is much more limited than other sources of light such as incandescent or flourescent light. Lasers emit at specific wavelengths such as 632nm (helium-neon laser) whereas, by comparison, an infra-red lamp emits many wavelengths within the infra-red spectral range (multiple wavelengths). This becomes important as wavelength becomes the primary determinant of depth of penetration. The term collimation refers to a laser’s high degree of beam parallelity and is the opposite of beam divergence. This becomes clinically important since the greater the divergence, the larger the spot size for treatment and the lower the power density. A more focused beam increases the power density and also increases the ocular hazard for both operator and patient. To minimize losses in power, the laser should be kept as close to the target tissue as possible. It is important to note that non laser sources of light scatter light at many wavelengths in different directions, in stark contrast to laser light which is focused almost perfectly parallel and in one direction. Finally, a laser is said to have coherence, a property whose biological significance has been debated by researchers. Coherence suggests a synchronicity in light waves so that each wave maintains a precise spatial relationship with other waves and that this pattern is maintained over long distances. Having said this, there is a trend towards manufacturing superluminous diodes (SLDs) which are highly monochromatic and collimated, but not coherent sources of light. This translates to a less expensive, and cheaper manufacturing process while retaining many of the true laser’s desired qualities.35

Laser frequencies are often a point of discussion and debate as they relate to cold laser application. There are many manuals in existence written for the most part, anecdotally, whereby authors passionately make an argument for the importance of frequency modulation (chopping a continuous wave) into various frequency cycle or pulse bursts, sometimes altering the pulse amplitude, width, and interpulse interval. Whether there is strong evidence at this time that a pulsing frequency affects a specific clinical condition is not clear. That is not to say that future research will not elucidate key frequencies as optimal for therapeutic goals. There is in existence an entire library of information that supports the physics of frequencies in general (sound, light, electrical etc) as being important in achieving certain characteristics such as conveying intelligence in radio waves (AM,FM). Authors such as Voll, Nogier and Bahr all wrote about resonance theory and how frequencies transfer kinetic energy to electrically charged cell particles and also can transmit specific information. We know for instance that electromagnetic frequencies in brain research are associated with certain bodily reactions, such as delta waves for deep sleep, and gamma waves in stress. In any case, the role of laser frequencies remains an open area for clinical investigation.

Tendinopathy. There have been numerous reports published that support the beneficial aspects of LLLT in tendon healing through laser’s positive effects on collagen tissue. Enwemeka et al reported that several laser types including HeNe, GaAs, and GaAlAs all promoted beneficial effects on tendon healing when combined with ultrasound and early weight bearing, over those of ultrasound and early weight bearing, together or in isolation, without laser.23 The authors noted improvements in biochemical, biomechanical and morphological indices of tendon healing. A clinical study using 176 patients with tendonitis conducted by Logdberg-Andersson et al found that laser application significantly reduced the morbidity associated with acute tendonitis over a 6 session treatment course.24 Similar findings were corroborated by Bjordal et al in 2001,25 Thomasson,26 and Hronkova et al.27 Energy densities ranging between 5 and 20J/cm2 and wavelengths above 800nm are recommended for deeper penetration capabilities. No more specific dosage recommendations can be provided at this time since more research is required to elucidate more precise dosages. Practitioners who treat facial points for conditions such as neuralgias or TMJ syndrome will irradiate at dosages approximating 1-5J/cm2 and may experience success with either HeNe or deeper penetrating lasers such as GaAlAs.

Last updated on: January 28, 2012