Athletic Training and Sports Health Care

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Clinical Roundtable 

Light Amplification by Stimulated Emission of Radiation

Susan Saliba, PhD, ATC, PT; Paul Borsa, PhD, ATC

Abstract

 

Abstract

 

Dr. Konin: What is behind the recent buzz regarding laser as a rehabilitative tool?

Dr. Borsa: Therapeutic lasers are extremely popular in European countries, Russia, Australia, and Canada, and are now beginning to permeate the U.S. medical communities. I have seen a number of articles in health and rehabilitation periodicals such as NATA News dedicated to the use of therapeutic lasers in health care practice. I think people are reading these articles and wanting to know more about the modality, hence the recent buzz.

Dr. Saliba: Laser has always interested clinicians as a potential method to influence healing, but the recent increase in interest is probably linked to the U.S. Food and Drug Administration (FDA) approvals. In 2002, laser therapy was approved by the FDA as part of a comprehensive treatment for carpal tunnel syndrome and non-specific neck and shoulder pain. Clinicians are now able to bill for these treatments, making it more justifiable to purchase a unit and use the laser clinically.

Dr. Konin: How did you get involved and develop an interest with using therapeutic laser?

Dr. Borsa: I developed an interest in the use of therapeutic laser mainly from learning about the modality while teaching a therapeutic modalities course and then seeking out and reading the literature behind its actions.

Dr. Saliba: We were fortunate to have an early laser at the University of Virginia with an investigational device exemption in the 1980s. Most of the research at that time was conducted in Europe, but empirically we saw some effects of using laser, especially on the resolution of hematomas. I collaborated on an animal study that investigated the effects of gallium arsenide laser treatments on the size change of a hematoma induced on a rat hind limb.

Dr. Konin: Simply put, what are the benefits of laser that other modalities may not offer?

Dr. Borsa: Laser has the benefit of stimulating cellular processes that are conducive to growth and repair, which separates it from other therapeutic modalities. Laser is not a thermal modality; although there may be transient heating of the skin, the thermal effect is not significant. The body’s response to red and infrared light exposure is similar to the process of photosynthesis. Laser delivers light to tissues (in the form of a photon) where it is absorbed by cells (specifically the membrane and intracellular organelles). Once absorbed, the energy is converted to biochemical energy (mainly in the form of adenosine triphosphate [ATP]), where it assists in cell growth and repair. It can facilitate tissue healing, primarily repair and regeneration, which other modalities such as ultrasound and electrical stimulation are not able to do directly.

Dr. Saliba: Laser, similar to ultrasound, is a passive treatment that adds energy into the system to influence the inflammatory and healing processes. These modalities give clinicians a mechanism to accelerate the proliferative phase of inflammation and decrease pain. Ultimately, therapeutic exercise is the most important factor in rehabilitation, but if there is a means to initiate exercise sooner with less pain, modality use is desirable. A wound treated with laser may have the tensile strength at 10 days that an untreated wound would have at 14 days. Although the 4-day difference does not seem like it would make a meaningful change, if the wound, such as a capsule tear, can tolerate exercise that contributes to the development and organization of collagen earlier, then there may be an effect on the outcome.

Dr. Konin: Are there any concerns, disadvantages, or potential side effects that should caution one to use laser?

Dr. Borsa: There are little known risks or side effects with laser. Side effects are rare and transitory. Therapeutic dose is the main concern. I use a class IV high-power laser, as opposed to the class IIIb or low-level laser. The class IV laser uses output powers >500 mW (0.5 W), but typically <6 W of peak power. Low-level or class IIIb lasers use output powers ≤500 mW. The advantage of the class IV laser is you get to deliver a greater magnitude of light energy to the tissues in a shorter amount of time. However, you have to be careful not to burn the skin. This can easily be accomplished by using a pulsed mode with a 50% duty cycle and also by keeping the laser diode moving across the skin, thus preventing heat build-up.Some individuals respond with a rash or reddening of skin. Individuals who are immunosuppressed or have an autoimmune disorder such as lupus are at risk for hypersensitivity. Some people report feeling nauseous after receiving a high dose of laser. Laser should not be used on a tattoo because the dark pigment from the ink can cause heating of the skin. Eye protection for both therapists and patients is needed when using laser to prevent retinal exposure. A laser beam, if pointed directly into the eye, has the potential to damage ocular tissues, primarily the retina.

Dr. Saliba: There are few side effects of laser, and most commercial lasers in sports medicine have relatively low power so the potential for overdose is low. However, when applying energy to a system, it is important to note that more is not necessarily better. The goal is to stimulate the normal physiological processes, and when too much energy is applied or when the treatment is applied too frequently (as in more than once per day), then the cellular processes may slow. A minimal amount of energy is needed for laser treatments, which is one reason why such variable outcomes are reported.Laser is a focused light energy. Because the beam does not diverge, a concentrated amount of light could be absorbed by the retina, potentially causing damage. Holding the beam so that the light goes into the eye is dangerous, but because of the collimated beam, an area surrounding the eye can be treated. Some lasers are beyond the visible spectrum, such as infrared lasers. Additional care should be used with these lasers since the beam cannot be seen and could be inadvertently directed into the eye.

Dr. Konin: What long-term outcomes are we awaiting that could make the most impact on our usage of laser?

Dr. Borsa: We desperately need well-designed and controlled dose-ranging studies that will determine proper dose requirements for a wide variety of musculoskeletal conditions. The therapeutic outcomes in animal studies are compelling and need to be translated to human populations. This can be accomplished through well-designed clinical trials. Laser therapy appears to have its greatest therapeutic effect in the postacute stage after in-flammation has subsided and the repair process is under way. Tissue regeneration and repair is significantly accelerated when exposed to proper doses of laser. Laser has not been found to significantly control acute inflammation and pain, so this area needs to be more thoroughly investigated.I think that laser could one day become a standard conventional therapeutic modality in medical clinics after the efficacy is established. It has far-reaching applications such as assisting with injury repair for sprains, strains, contusions, postsurgical tissue healing, neuron and muscle fiber regeneration, and tissue reperfusion. It will not happen overnight; it probably will take years or decades before laser is a mainstream modality.

Dr. Saliba: Controlled clinical trials really are needed to determine the effects of laser treatments. The pathology and timing of the treatment must be documented as well as the type and intensity of the laser. There is some early evidence that laser will affect the cells differently at the various points in the inflammatory process. For example, a treatment that shows effectiveness acutely may be ineffective later or vice versa. Distinguishing the timing of the treatment with the dosage in the research may help determine better treatment algorithms clinically.

Dr. Konin: What is the single best piece of advice regarding the use of laser you think is important to share with clinicians?

Dr. Borsa: You, as the operator of the device, need to figure out proper dosing parameters and schedules. This involves choosing the adequate lasing medium for depth of penetration, power output (intensity), time of exposure (duration), frequency (times per week), length (days/weeks/months), and spot size (beam diameter), along with other factors such as using a pulsed mode or continuous wave, direct contact versus scanning (non-contact) technique. All of these factors add up to a cumulative dosage.This is a gray area for clinicians and researchers, and you need to become comfortable with the device and how you use it when treating athletic injuries. Laser follows the Arndt-Schultz principle in that if you underdose or understimulate a target (eg, sprained ligament) you get no, or very little, therapeutic benefit. If you overdose, you suppress cellular function and hinder the reparative process. If you can find the proper therapeutic window in which to operate, you will get positive results. That, to me, is the most important piece of advice I can give clinicians.

Dr. Saliba: Know what you have. There are numerous laser products on the market and many are combined with other light sources such as superluminous diodes or light-emitting diodes (LEDs). It is difficult to discriminate the various products and determine the intensity of the lasers marketed currently. Although there may be some benefit of using these other light therapies, they do not have the unique characteristics of a laser. Therefore, when purchasing a laser, it is important to understand the power of the device (generally, the higher the better), the wavelength that can affect penetration, and the number of laser diodes. Several laser diodes on the same applicator shorten the treatment time. Making this information available seems obvious but looking through product literature is confusing.

This Clinical Roundtable was conducted July 31, 2009.

Susan Saliba, PhD, ATC, PT, is from the Department of Human Services, University of Virginia, Charlottesville, Va.

Paul Borsa, PhD, ATC is from the Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Fla.

Moderator: Jeff G. Konin, PhD, ATC, PT

10.3928/19425864-20091020-02

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