Sorting through research on using cold lasers as an adjunct to therapy

By Tiziano Marovino, DPT, MSC, BHSC, BRLS, BPE, CSCS, CES

Cold laser, soft laser or low level lasers all mean the same thing. Lasers operating under a specified power level of 1 watt and/or intensity level of 1 watt per centimeter squared are considered non-thermal devices and typically class 3B devices by an agreed upon international standard.¹

The use of low level laser therapy use in North America (on a larger scale for clinical purposes) began in Canada around 1985, when He-Ne (helium neon) lasers of small-power 5-10mW range began to emerge. The idea of using a laser in physical therapy was an attractive one to many clinicians, and in the absence of any significant governmental regulatory control of the devices, using this new technology was a simple process.

The use of laser therapy grew steadily over the next few years and so too did the availability of new features, including different wavelengths and external frequencies. The clinical rationale for the use of lasers was based largely on either cellular or animal research, with very little in the way of controlled clinical trials.

As time passed, the availability of more in vivo and in vitro evidence grew steadily but a relative paucity of clinical evidence became glaringly apparent. By the early 1990s, a Scandinavian group began publishing human clinical trials, finding no difference in laser treated versus control groups. This group published numerous times and reported on various soft tissue conditions, with the results always the same.^2,3 In all fairness to laser use, these researchers did not conform to minimal dosage requirements, as they were understood even at that time.

We would expect, both then and now, that there will likely be an energy threshold requirement for various clinical conditions, with modifying variables being skin pigmentation and adiposity. Here we are 17 years later, in the United States, and in the beginning of another potential laser revolution in rehabilitation. What has changed? We would expect that in the last decade a sizeable amount of clinical research would now be available. Is this really the case?

Industrial or Independent Research?

Industrial research is that research evidence generated by manufacturing companies whose sole purpose is to sell devices. Industrial research is when a company A performs its own in-house research and/or pays either money or gratuities to another center to carry out the research with that company A's product.

This form of research prevails in the marketplace even today. When a laser company offers to educate therapists in the wide array of cold laser applications, they are in many cases using information gathered in poorly controlled trials with few actual patients. As well, there continues to be an over-reliance on cellular and animal model studies to support the clinical use of laser. The problem with this practice is, of course, that cellular and animal results may not transfer readily over to the human condition.

Here is one example. A recent publication on laser-accelerated pain and inflammation reduction written by a laser expert (who also happens to be employed by a laser manufacturer) made some very enticing commentary on cold laser's abilities to 1) enhance leukocyte infiltration; 2) increase macrophage activity; 3) increase neovascularization; 4) increase fibroblastic proliferation; 5) increase keratinocyte proliferation; 6) increase early epithelialization; 7) increase growth factor; 8) enhance cell proliferation and differentiation; and 9) heal wound tensile strength.

A cursory review of the references used in this article reveals that, despite the author's claim of LLLT having "over 200 clinical studies–many of which are double-blind, placebo controlled, and in excess of 2,000 articles on LLLT," of the 28 references listed to support his contentions, 22 are in vivo or in vitro studies, four are abstracts published for European conferences, and the remaining two references are studies published in the Journal of Laser Therapy. If any of those aforementioned 2,000 articles that the author alluded to were in fact randomized, controlled clinical trials supporting the stated claims, they would likely have also been included in the article by the author.⁴

Lasers in PT: A Future?

Laser devices continue to sell in the United States, despite a lack of good experimental evidence demonstrating efficacy. Manufacturers will continue to market lasers for applications of questionable benefit because they profit from their sales. Therapists will continue to purchase these devices because they want to believe they will make a difference in their patients' clinical problems. Patients will continue to get better when laser is applied to their problem area, both from a placebo effect, and we hope, from a treatment effect.

The relative contribution of each continues to be a mystery, however, because proper clinical trials on our patient populations have not been carried out in sufficient numbers and with proper controls. The use of industrial research and/or in vivo-vitro trials continue to be used in place of randomized, controlled clinical trials to justify clinical efficacy. Laser studies need to be performed at independent centers using similar populations and with the application of a rigorous control standard in study design, all in keeping with evidence-based practice paradigms currently in use.

In his text, Therapeutic Lasers: Theory and Practice, David Baxter writes, "the claims made on behalf of laser therapy, particularly by some laser manufacturers, have been grossly exaggerated, if not actually misleading." He goes on to admonish the quality of existing research as "poor, often being no more than anecdotal reports of the author's experience of a particular type of laser system, or the laser treatment of a certain condition or range of conditions."¹

Laser Devices

Caveat emptor, or buyer beware, is the operative phrase when purchasing a laser or laser system. A prior commentary from a previous article in this magazine on laser therapy quotes a United States researcher: "If you talk to the FDA, they will tell you that they [the FDA] do not have to approve laser therapy for any particular treatmentÉwhat they specifically forbid you to do is lay public claim about its efficacy, specific effects and what laser therapy can and cannot do."⁵

While not false, this statement is not entirely accurate. The FDA certainly does have an approval process in place for any new medical device or product, and it does specifically approve each step of the process from investigation (IDE), to marketing (PMN to PMA), to complaints or problems along the way. Furthermore, the FDA does approve usage of a device for very specific and pre-defined purposes. For more information on a specific company's product, the reader is referred to the FDA Website where that company's specific section 510(k) pre-market notification of intent letter, or facsimile, can often be found. In this document, the reader can identify exactly what that device is and how FDA has classified the device including specific application(s) and restrictions for the device.

As readers review this information, they might be surprised at how some "laser devices" are actually infra-red devices, or are class 2 versus class 3 devices, and not necessarily lasers. What is the difference? Class 2 devices are very low power units that possibly limit any clinical usefulness. Another distinguishing feature of a true laser is the beam uniformity or collimation. This is a unique property of laser and one that is not usually associated with an infra-red lamp.

The FDA understands this and defines an infra-red device as "a device that emits energy at frequencies of between approximately 700 to 50,000 nanometers to provide topical heating."⁶ A cold laser emits at a specific wavelength (monochromatic) and generates no heat (cold laser).

So how does one of these "similar" devices get FDA approval? The manufacturer shows the FDA the technical specifications on their product, demonstrating that the product is similar to one already approved by the FDA. If the FDA agrees, they approve the new device under a "substantial equivalence" provision, allowing this new device to be used within the parameters of the application.

Why is any of this important? Because devices are often being marketed and sold under misleading labels and are using inappropriate research to justify their clinical use. Does this mean the devices do not work? Absolutely not; the devices may perform as well as the manufacturers claim they do, or perhaps even better, but that is not the point. The point is that for the most part, many claims regarding the effectiveness of laser therapy are questionable and without scientific validation at this time.

Physical therapists should understand this when they purchase a laser unit, and should also be encouraged to study the effects of laser on their target conditions of interest. This information can be shared with other PTs who are interested in lasers and will ultimately create a scenario whereby therapists no longer need to rely on extrapolated research for answers to clinical questions.

Conclusion

Laser therapy has not been tested thoroughly in randomized, double-blinded, clinical trials, and potential users of this technology should understand this. This scenario creates a situation whereby the clinician using laser therapy has an opportunity to perform some valuable systematic data collection while simultaneously treating a patient.

Those of us who have used lasers before on a regular basis and on many clinical conditions have a belief that this form of treatment is beneficial, but this belief is based on mostly clinical observation rather than good science. Much of the existing research supporting these observations is arguably substandard despite being in concordance with empirical and observational data.

Having said this, there is only one lesson, and that is that therapists should inform themselves about of what is important in a laser device (parameters) and not rely singularly on a laser company's "body of evidence" supporting the use of the product. This evidence often consists of a series of abstracts, some published (others not), which often have little clinical relevance to a specific application.

In conclusion, laser therapy users will need to take responsibility for the application of this modality and to eventually demonstrate clinical effectiveness through well-designed scientific trials consistent with an evidence-based paradigm. Patients, payors and the clinical community should accept no less.

References

1. Baxter, D. (1994). Therapeutic lasers: Theory and practice. Churchill Livingstone.

2. Thorsen, H., Gam, A., & Svensson, B. (1992). Low level laser therapy for myofascial pain in the neck and shoulder girdle. A double blind, cross-over study. Scandinavian Journal of Rheumatology, 21(3), 139-141.

3. Vasseljien, O., Hoeg, N., et al. (1992). Low level laser versus placebo in the treatment of tennis elbow. Scandinavian Journal of Rehabilitative Medicine, 24(1), 37-42.

4. Martin, R. (2003). Laser-Accelerated inflammation/pain reduction and healing. Practical Pain Management, Nov/Dec, 20-25.

5. Bassett, J. (2002). A thousand points of light: Lasers may point the way to a bright future for PTs. ADVANCE for Physical Therapists and PT Assistants, 13(1), 31-32.

6. Food and Drug Administration. (2003). Retrieved from the World Wide Web, www.fda.gov/cdrh/devadvice

Tiziano Marovino is the former director of research and development for World Laser Corporation and a cold laser consultant to government, industry, health and corporate sectors. He has presented and published in the field of low level laser therapy. Dr. Marovino has taught low level laser therapy (LLLT) at four universities in Canada and the U.S. Currently, he is director of rehabilitation services at Preferred Medicine, Spine, Sports, and Orthopedics, Allen Park, MI.