Current Perspectives in Clinical Treatment & Management in Workers' Compensation Cases,
2011, 191-201
191
Advances in Laser Therapy for the Treatment of Work Related Injuries
Brian A. Pryor, PhD
LiteCure, LLC.; E-mail: brianp@LiteCure.com
Abstract: Laser Therapy has been used as a therapeutic modality for many years and has yet to become a
standard of care. This modality has great potential to be used in the clinic for the reduction of pain, inflammation
and to aid in the healing process. For years many studies have been done showing the benefits of laser therapy but
implementation of this technology into clinically successful products has been lagging behind. This chapter will
briefly review the science behind laser therapy, the traditional systems which were used and new technologies,
Class IV lasers, now being used to treat injuries seen in the work place. New advances in this technology are
being made which are leading to improved and consistent clinical outcomes. The mechanisms of action for pain
relief, reduction of edema and tissue healing will be presented as well as important parameters to use in order to
succeed when choosing this exciting therapeutic modality. Included are brief reviews of laser therapy when
treating epicondylitis, carpal tunnel syndrome, neck and back pain as well as in post surgical rehabilitation
applications. Laser therapy is a tool which can have great benefit when treating both acute stage injuries as well
improving some chronic conditions.
INTRODUCTION
Lasers have been used for many years for a variety of medical applications. Applications such as laser hair removal
and vision correction have aided in popularizing this high tech innovation in the field of medicine. Surgical lasers
are also now being used to perform surgeries which previously would have been very difficult with traditional
techniques. Lasers also have been used in rehabilitation and occupational therapy clinics for many years, especially
in some European counties. This technology is now getting integrated more and more into everyday practices in the
United States, as good products with sound science are being introduced to the marketplace.
Over 30 years ago, Andre Mester first observed that a very low level of laser energy was causing cellular changes in
mice (Mester 1967). Since that first observation there have been thousands of studies done on using lasers to
influence cellular repair, reproduction or inhibition (Hode & Turner 2002). Many of these studies have utilized very
low output power, laser systems.
For the past 10 or more years, the lasers used in physical therapy and occupational therapy have been low power
devices, typically between 5 mW to 500 mW of output power. These devices have been called "low level lasers" or
"cold lasers." These terms arose to differentiate these types of therapeutic applications from more powerful laser
systems which are used to ablate tissue for surgical or cosmetic applications. Most of these terms have been inspired
more by marketing than by science. The term cold laser was first used by the early scientist in this field performing
in vitro studies since many skeptics claimed that heat and not laser light was the cause of the cellular changes they
were reporting. Being diligent scientists, they measured the insignificant temperature changes during their
experiments and proved that the laser light was causing cellular changes. The entire field then took on the term, cold
laser therapy. In fact almost all lasers when used clinically for any significant amount of time will produce a small
temperature change in tissue. The important thing to acknowledge is that the rise in temperature is not the cause of
the cellular changes. The stimulation of cellular activity is caused by a photochemical response to the laser light.
The reservation of many therapists to integrate laser therapy into their clinic has resulted from conflicting findings in
the literature. Often times these studies have been done with very low dosages which have shown inconsistent or
even poor results. The studies performed on more superficial conditions such as wounds have shown very good
clinical results. The challenge has been with more complex conditions or those with a deep tissue component. Newer
laser systems with higher output power are now available and gaining acceptance in the market due to the ability to
treat deep tissue such as a hamstring injury. Results are more consistent and due to the ability to deliver a larger
amount of energy, broad areas can be treated in a short time assuring a therapist won't "miss" the troubled area.
Chris E. Stout, Matt Kruger and Jeffrey Rogers, (Eds)
All rights reserved - 2011 Bentham Science Publishers Ltd.
192 Current Perspectives in Clinical Treatment
Brian A. Pryor
New scientific studies are proving positive outcomes on challenging conditions using these higher powered laser
systems (Alaskym et al 2010; Charles et al 2010).
MECHANISM OF ACTION
Photochemical effects can occur when laser light is absorbed by a chromophore and a biochemical change is inspired.
Photobiomodulation, which is the term the industry has decided upon, is an example of a photochemical process in
which photons from a laser source interact with cells and cause a stimulation or a biochemical change. The mechanism
of action of laser therapy or photobiomodulation has been debated for some time. To this day there are various thoughts
to the exact mechanism. In fact there may be several potential mechanisms and even slightly different mechanisms
depending on the type of cell being stimulated. The most supported mechanism is that cytochrome c, which is found in
the mitochondria inside the intercellular membrane, acts as the photoreceptor. Cytochrome c absorbs light from 500 nm
to 1100 nm due to specific properties of this large molecule (Karu 1995). Once light is absorbed cytochrome c is
excited and can more readily bond with oxygen and become cytochrome c oxidase which is critical to the formation of
ATP. ATP is critical for energy production in the cell and leads to host of biologic responses or secondary mechanisms.
These mechanisms lead to the reduction of pain, inflammation and healing of tissue.
REDUCING PAIN
Pain management has been one major indication for laser therapy. How does this work? There have been extensive
studies looking various mechanisms resulting from photobomodulation and resulting pain relief (Hode & Turner
2007; Faegapani et a1 2008).
Upon laser interaction with cells the following processes have been seen to occur. There is an increase in serotonin
(5-HT) levels (Cassone et al 1993; Walker 1983; Cassone et al 1990). Serotonin acts as a chemical messenger that
transmits nerve signals between nerve cells. Serotonin levels impact mood.
There are also increases in Beta Endorphins, which decrease pain sensation.
These increases (Montesinos 1988; Labajos 1988; Cramond et al 1994), can act to abolish pain at the receptor site.
Nitric Oxide which is critical for normal action potential in impulse transmission activity in nerve cells is also increased
upon laser stimulation (Mrowiec 1997). NO also has an effect on vasodilatation which enhances oxygenation.
Bradykinins which can be prevalent in injured tissue, induce pain sensation by stimulating nociceptive afferents.
Laser therapy has been shown to decrease these peptides reducing pain levels (Jimbo et al 1998).
Therapeutic lasers have also shown the following positive effects:
Normalization of Ion Channels, Ca++, Na++, K+ proven to reduce pain levels (Alvarez-Leefmans et al 2005;
Friedman & Lubart 1911).
Blocked Depolarization of C-Fiber Afferent Nerves (Wakabayashi 1993): Therapeutic lasers can suppress the
excitation of these fibers, particularly in low velocity neural pathways from nociceptors (Kawatani et al 1993).
Increase Nerve Cell action potential: Injury or trauma can impair the resting potential of nerve cells leading to a very
low threshold for pain. Laser treatment has shown to increase the resting potential closer to the norm of —70
mV(Blom et al 2000).
Increase release of Acetylcholine(Lupyr & Sergienko 1986; Mester et al 1977): Acetylcholine helps normalize nerve
signal transmission in the autonomic and somatic pathways.
Axonal Sprouting and Nerve Cell regeneration: Several studies have shown the lasers positive effects in nerve repair
which can have a dramatic effect in pain relief (Anders et al 1993; El-Ani et al 2009; Anders et al 2005).
Advances in Laser Therapy for the Treatment of Work Related Injuries
Current Perspectives in Clinical Treatment 193
All of these proven cellular responses contribute to pain relief upon therapeutic laser treatment. These mechanisms,
together with the anti-inflammatory and the tissue healing benefits make the laser an integral modality in both
making patients feel better and get better.
Reducing Inflammation
In addition to the above mentioned mechanisms for reducing pain, laser treatments have been shown to reduce
inflammation. The following actions have been proven to produce key elements which aid in the reduction of
edema.
Enhancement of ATP (Friedman & Lubart 1911; Cui et al 2002; Casanassima et al 1984)
Stimulation of Vasodilatation (NO) (Gladwin & Shiva 2009)
•
Reduction in Interkeukin-1 (Albertini et al 2005)
•
Stabilization of the Cellular Membrane (Greco et al 2001)
•
Acceleration of Leukocytic Activity (Greguss et al 1978)
•
Increase Prostaglandin Synthesis (Abiko et a1 2000; Harada et al 2004)
•
Enhanced Lymphocyte Response (Karu 1991)
•
Increased Angiogenesis (Krispel et a1 2002; Belkin et al 1994)
•
Temperature Modulation (Kurokawa et al 1991; Maeda 1990)
•
Enhanced Superoxide Dismutase SOD levels (Eichler et a1 2003; Eichler et a1 2005)
PROMOTING HEALING
Wound healing has been the area where most of the traditional laser therapeutic studies have been completed. The
results in these studies have been very encouraging and the mechanisms of tissue healing are important for other
injuries; such as tears and contusions, as many of the same mechanisms are needed to promote tissue healing.
Below is a list of important physiological changes upon laser treatment along with references to the studies which
measured these modifications.
•
Enhanced Leukocyte Infiltration (Karu 1991)
•
Increased Macrophage activity (Bansal et al 2003; Qin et al 1992; Bolton et al 1990)
•
Increased Neovascularization (Gladwin & Shiva 2009)
•
Increased Fibroblast Proliferation (Cagnie et a1 2003; Abrahamse & Hawkins 2006)
•
Keratinocyte Proliferation (Graves et al 1990)
•
Early Epithelialization (Bayat et al 2005)
•
Growth Factors Increase (Benayahu et al 2005; Abrahamse et a1 2008)
•
Greater wound tensile strength (Mester et al 1967)
The combined effect of pain relief, reduction of edema and promotion of tissue healing makes laser therapy a
valuable tool in all aspects and stages of treatment of injuries. Treatments can be performed soon after an injury and
help with both pain relief and healing.
HOW MUCH LASER LIGHT IS NEEDED?
Certainly there is a threshold, or an optimal amount of light which is needed to turn on the therapeutic effects listed
above. Hundreds of the scientific studies have been done in vivo and have characterized the optimal dosage or range
of dosages need to achieve a cellular response (Hode & Turner 2007).
194 Current Perspectives in Clinical Treatment
Brian A. Pryor
These studies are imperative, since they give a baseline for the amount of laser energy we need to deliver in a given
area to achieve results at the cellular level. However, if we were to use this same dosage which had an effect when
exposed in a Petri dish, on the surface of the skin, we would get considerably less dosage at the tissue in which we
want to achieve therapeutic results.
When using a therapeutic laser in vivo, we need to consider many additional parameters. If most of the laser light is
absorbed in the dermis, for example, then we cannot achieve an optimal effect. When laser light hits tissue, it can be
absorbed, scattered (including reflection), or transmitted. The main components in tissue that we need to consider
are: melanin, oxyhemoglobin, deoxyhemoglobin, and water. We can get light into the body with wavelengths from
600 nm (red end of the spectrum) to 1100 nm (near infrared end of the spectrum). The range is often referred to as
the "therapeutic window" for laser applications.
Although these wavelengths can penetrate, each wavelength has unique penetration characteristics.
If we put an ordinary white light source, a flashlight, into the palm of our hand, we will see a red glow out the other
side. Longer wavelengths such as red penetrate deeper. The amount of red light visibly seen through the hand is
dependent on the color of the skin. Melanin absorbs light strongly, so dark skin will absorb more light, especially
wavelengths from 500 nm to 800 nm. Wavelengths longer than 1200 nm absorb in water very strongly and therefore
it is difficult to get much penetration in tissue. These longer wavelength lasers are typically used in ablative
procedures such as surgery or skin resurfacing.
The important parameter for a therapy laser system to have is the appropriate wavelength to allow penetration to
deep tissue. Wavelengths longer than 800 nm can typically achieve appropriate depths to treat most musculo skeletal
conditions. When dealing with wounds or more superficial conditions shorter wavelengths such as 635 nm can be
used effectively, since penetration is less important.
1WPower
5WPower
10WPower
Figure 1: 980tun/810 nm laser output penetrating though a hand as a function of output power. Images were taken at a fixed
exposure rate using an Infrared sensitive camera. This figure shows that high output power penetrates deeper as a function of
exposure time.
Since all wavelengths have a probability of scattering, absorbing, or transmitting, the more power, or the greater
number of photons you have, the greater depth of penetration as a function of time. (See Fig. 1) Let's assume that
we get 2.5% of the total laser light delivered to the skin actually reaching the patella tendon. If we use a 250 mW
laser source, we are only getting 6.25 mW at the tendon or.00625 J per second of exposure.
If we use a 10 W laser source, we will get 250 mW at the tendon or 0.25 J in a second. By using a lower powered
laser source for a longer time you can potentially achieve a large dosage to deep tissue. Using the example above,
for the 250 mW laser to achieve the equivalent amount of energy as the lOW laser puts out in 1 second it would take
almost 1 minute. (See Table 1)
Current Perspectives in Clinical Treatment 195
Advances in Laser Therapy for the Treatment of Work Related Injuries
Table 1: Treatment time for various output power laser systems
Output Power
Dosage
Size of treatment area
Treatment Time
5 mW
4 J/cm2
5 in x 5 in
35 hours
100 mW
4 J/cm2
5 in x 5 in
1 hour 47 min
250 mW
4 J/cm2
5 in x 5 in
43 min
500 mW
4 J/cm2
5 in x 5 in
21.5 min
5W
4 J/cm2
5 in x 5 in
2 min 9 sec
10 W
4 J/cm2
5 in x 5 in
1 min 5 sec
In principle a lower power unit with the appropriate wavelength for good penetration (800nm to 1000nm) used for a
long period of time, ultimately will be able to get to the same depth and yield therapeutic results. However, one
study showed that results were not the same by using a very low power density. It was shown that under 10 -5 W/cm2
et al 1993).
evnwhxposdfralgeitm,hdnoasurblet(Adichk
Many conditions are very hard to diagnose to a very precise afflicted area, or often times conditions have other
involved muscles contributing to the pain. Therefore it is important to treat as broad of an area as possible. This is
where newer, higher power laser units can have a great advantage. Since you can get a therapeutic dosage of light
deep into tissue, in a short treatment time, it is possible to treat a very broad area. This enables the affected area and
satellite areas of pain to be effectively treated.
A good example of this, is when treating a patient with carpal tunnel syndrome. Carpal tunnel is typically associated
with an impairment associated at the carpus/wrist. Often times the pain may be associated with a nerve impairment in
the area around the elbow, or possibly at the cervical spine. As discussed previously, a typical range for effective
dosage is on the order of 4 to 10 J/cm 2 . Since the target area is not extremely deep, in the case of carpal tunnel we
would use approximately 5 J/cm 2. If we assume we want to treat the entire wrist area (3"x 6" or 116 cm 2) it would take
approximately 580 J (5 J/cm 2 * 116 cm2). When treating with a typical lower power laser with 250 mW output, it takes
approximately 38 minutes. Treating the same area using a higher power, 10 W, laser would only take 58 seconds. The
older, lower powered laser systems make it very hard to treat a broad enough area to get consistent results in an
everyday clinic. Treating carpal tunnel effectively and consistently, takes a treatment protocol which can address the
possible involvement of the nerve route all the way to the cervical spine area. (see Fig. 2) This type of comprehensive
approach is not practical when using a lower power laser system. If using a 10 W laser, treating this entire area will
take 4 to 6 minutes depending on the size of the patient and there will be positive and consistent outcomes.
Figure 2: Nerve route to treat when treating carpal tunnel syndrome
196 Current Perspectives in Clinical Treatment
Brian A. Pryor
THE FOLLOWING SECTIONS WILL GO OVER SOME TREATMENTS AND STUDIES DONE ON
SEVERAL OF THE MOST COMMON, WORK RELATED INJURIES.
Epicondylitis
Laser Therapy can be a very effective modality in treating epicondylitis. Some of the early studies done using laser
therapy showed negative to moderate results (Haker et al 1987; Haker & Lundeberg 1990; Basford et al 2000).
All of these studies used very low dosages and only treated small, very select areas. Other studies using a more
comprehensive treatment area, with a larger dosage, show significant results in blinded studies (Simunovic &
Trobonjaca 2001; Simunovic et al 1998; Adamek eta! 1997; Terashima 1990; Damjanova & Manolov 2000).
One study compares the treatment of laser, corticosteroid injections, and a combination therapy of laser and
injections. The combined treatment had a significant higher analgesic effect over the other two (Konstantinovic
1997). This study reminds us that using appropriate adjunctive therapies can often lead to much enhanced outcomes.
A summary of studies on the effect of laser therapy on tendonitis was done by Bjordal (Bjordal 1997). This review
concluded that laser therapy was an effective treatment both at reducing the inflammation, as well as stimulating
tendon regeneration. Optimal dosages were between 0.2- 4 J/cm 2 for regeneration and 3-8 J/cm 2 for reduction of
inflammation. A recent double blind study using a higher power class IV laser has shown significant results at 3
month follow up of the laser treated group over a sham group, when measuring grip strength, pain with grip and
lateral palpation. The treatment technique used a very comprehensive protocol and relatively short treatment times
(Alaskym et al 2010).
With a comprehensive treatment approach, laser therapy is an effective modality in treating medial and lateral
epicondylitis with long lasting results.
Carpal Tunnel Syndrome
Carpal Tunnel syndrome is another very common work related condition which can be improved by treatment with laser
therapy. The key to getting success when treating this condition is to use a broad approach to treatment. Just treatment of
the carpal area may not yield results, as often this condition can stem from irritation of the cervical spine region. One
study showed by treating the spinous processes, the pain and tingling was alleviated (Chermanz eta! 1997).
A very nice study showing long term results was done by Neaeser, et al. This study showed significant decreases in
Melzack pain score, median nerve sensory latency, Phalen sign and Tinel sign, post-real treatment series but not
seen post-sham treatments. Patients were able to perform prior work (computer typist, handyman) and their
condition remained stable for 1-3 years (Naeser 2002).
As with many conditions, laser treatment of carpal tunnel syndrome, should be complimented by exercise and other
standard protocols. Conditioning and changes in work habits are imperative to success and full resolution. As
mentioned earlier, treating a broad area and including the nerve route, when treating carpal tunnel will ensure rapid
and consistent results.
NECK AND BACK PAIN
Neck and back pain are very common, often difficult to fmd a specific cause to the pain and always difficult to treat.
The pain can often be nonspecific, making both diagnostics and treatments very challenging. Lasers have been shown
to be effective when used in the treatment regime for these areas (Barnsley et al 2006; Bjordal et al 2003). A recent
meta-analysis of clinical studies using lasers, concluded that laser therapy reduces pain immediately after treatment in
both acute and chronic neck pain and pain relief lasted up to 22 weeks after treatmentBjordal et al 2009).
A recent pilot study, being done by the Health Sciences Department of Colorado University, Denver, compared the
pain relief obtained for nonspecific lower back pain between manipulation with Class IV laser therapy versus
manipulation alone. The manipulation + laser group had significantly less pain at week 4. With both neck and back
pain it is important to use a laser system which has appropriate penetration to reach deep tissues.
Advances in Laser Therapy for the Treatment of Work Related Injuries
Current Perspectives in Clinical Treatment
197
Since laser therapy can relieve pain and increase blood flow it will help to increase mobility for neck and back
patients. Acute neck and back pain will respond to laser treatments very quickly, many times a positive response is
seen after the first treatment. For more chronic conditions, it can take longer to see an effect, 3 to 5 treatments to
even see a small benefit and it may take up to 12 treatment sessions, in order to see a significant improvement.
Working soft tissue while delivering therapeutic laser will also help to improve outcomes in these challenging cases.
(See Fig. 4) This treatment approach is the key to having prolonged results. The combination of laser treatments,
stretching and exercise can have a major effect when treating patients with neck and back pain.
POST SURGICAL APPLICATIONS
Integrating laser therapy into post surgical rehab can lead to much quicker and better overall outcomes. By using the
laser immediately post surgery, you will be able to reduce inflammation and pain. Since the laser also has tissue
healing effects, the surgical site will improve faster, and there may be less scarring from the surgical incisions. Post
rotator cuff repair and post anterior cruciate ligament repair, are two procedures which adding laser therapy to the
post surgical rehabilitation plan, can dramatically improve the healing rate.
Patients will be more compliant to exercise, stretching, etc. since after the laser treatment they will have much better
range of motion and less pain. Most surgical rehab programs can benefit greatly by adding laser therapy.
TREATMENT BASICS
When treating patients, it is critical to understand the overall diagnosis and work laser therapy into the rehabilitation
program. A broad area should be treated as well as treating any potentially contributing muscle or joint. Fig. 3 shows
a typical area which would be treated in the case of epicondylitis. When using a laser with output power of greater
than 4W, or anytime the patient feels any warmth, a scanning method should be used. The patient should feel
soothing warmth during treatment, this sensation should never be more than a pleasant warmth. If the temperature is
uncomfortable, the output power should be reduced. These higher power laser units will allow for a broader and
faster treatment.
Figure 3: Comprehensive treatment area for laser treatment of epicondylitis
Scanning of the area with the laser should be done in a grid type pattern in order to ensure comprehensive coverage
of the affected area. Some laser systems allow the handpiece to be placed in contact with the patient's tissue. In this
case some manual manipulation or massage can be done while delivering therapeutic laser treatment (see Fig. 3).
This can be a very effective approach when treating deep tissue conditions such as muscle or tendon tears or strains.
Slight passive range of motion should be used when possible, during the last few minutes of treatment. Treatment of
any associated trigger points with the laser is also a very effective way to enhance therapeutic results. Many
therapists will combine soft tissue work after laser therapy. Another common adjunct therapy is to use TENS or estim after completing laser therapy.
198 Current Perspectives in Clinical Treatment
Brian A. Pryor
Figure 4: Example of a laser therapy handpiece allowing tissue massage/manipulation while delivering laser energy.
It is typically recommended that laser therapy be done every other day for a three week period, for a total of 6 to 9
treatments, depending on the condition, and if it is acute or chronic. When appropriate, laser treatments can be given
on a daily basis. If patients are in an environment where treatment is given every day, then it is recommended to
treat with the laser on a daily basis. Acute conditions will respond very quickly to laser treatment and a significant
benefit may be realized after the initial treatment. Typically a total of 6 treatments will be needed to see major
improvement. Chronic conditions will take longer to respond and may take up to 3 treatments to realize any benefit
and as many as 12 treatments to see significant outcomes.
Another advantage of using laser therapy is that there are very few contraindications. The contraindications which most
manufacturers lists are, don't treat pregnant patients, don't treat patients who are taking any photosensitive medication;
don't treat patients with cancer, don't treat over open growth plates, don't treat the eyes, don't treat the testicles, don't
treat over any active hemorrhaging. Eye safety is the biggest precaution when performing laser therapy. Appropriate
eye wear supplied with the laser should be worn by the clinician and the patient when treating. The eye should never be
treated and when treating conditions around the face, specific eye wear, like metal eye shields must be utilized. Most
contraindications listed for laser therapy are based on prudence and not on the results of studies. For comparison,
cosmetic lasers such as skin resurfacing or hair removal systems, are very powerful, hundreds of times more power
than even the most powerful therapeutic lasers. Even at these high powers and large dosages used in these types of
ablative procedures, there have been very few side effects out of millions of treatments.
Laser therapy treatments are very easy to administer, and depending on the power level of the laser being used,
treatment times take less than 10 minutes for most peripheral conditions and less than 15 minutes when treating a
large area like the back or hip. The laser is easy to integrate into standard treatment protocols in a clinic. Uniform
administration is achieved without requiring a high level of technical skill. Patients enjoy treatments, and will
mostly respond very quickly, leading to faster more effective outcomes and enhanced compliance.
CONCLUSION
The future of laser therapy will be an exciting one. Preliminary studies are showing promising results when treating
conditions such as peripheral neuropathies, strokes, and many other debilitating conditions. Fundamental studies in
laboratories are continuing to refine our understanding of the mechanisms of action of laser therapy. The results of
these laboratory studies need to be followed up with the appropriate animal models and then followed through to
good scientifically sound, clinic based studies with measurable outcomes. As we learn more, we will be able to
refine device specifications and protocols for clinicians to have the appropriate tool for treating specific conditions.
The field of biophotostimulation is growing, and will continue to find new applications where lasers and other light
devices can be used to address a variety of medical issues. Multidisciplinary collaboration will lead to faster
discoveries and better therapeutic tools.
When implementing laser therapy in the clinical environment, you need to make sure you use the right tool for the
right job. You need to take into account the types of conditions you are treating and the time you can afford treating
those conditions. Lasers can be an integral tool for treating the majority of rehab and workman's compensation
Advances in Laser Therapy for the Treatment of Work Related Injuries
Current Perspectives in Clinical Treatment 199
related conditions. This tool, like all others, must be used appropriately in your treatment regime to maximize
overall outcomes. As discussed above, the laser will help compliance with other parts of your treatment program,
helping to expedite positive outcomes and getting people back to in the game and back to work. Laser therapy can
be an important modality when treating both acute and chronic work related injuries.
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