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There is currently a lot of discussion in rehab circles surrounding the efficacy and therapeutic potential of light-based modalities. From professional sports teams to private practices, these technologies are starting to be used on a daily basis to treat injured tissue. Light-based therapy used to treat pain and inflammation can be delivered by both lasers and LEDs, and consumers often want to know the operational and therapeutic differences between them. Let’s take a look at the similarities and differences between the two.
Both laser and LED therapies rely on being able to deliver an adequate amount of energy to the target tissue in order to precipitate a photochemical process known as photobiomodulation (PBM). PBM “is a nonthermal process involving endogenous chromophores eliciting photophysical and photochemical events at various biological scales. Some processes that are impacted include, but are not limited to, the alleviation of pain or inflammation, immunomodulation, and promotion of wound healing and tissue regeneration.”1
Both sources of light share the same mechanism of action and are both commonly generated using diode technology. When used and studied in therapeutic applications, both lasers and LEDs are often built to emit similar wavelengths, either in the red or near-infrared spectrum, and have been shown to have pain and inflammatory reduction properties.2 Significant differences between the two do exist, however; including the power generated, the specificity of wavelength, and the physical characteristics of the beam generated from the diode.
Laser light is unique, in that it is monochromatic, coherent, and collimated. These traits make it well-suited to many medical applications.3 The monochromatic, or single wavelength, beam is ideal for stimulating chromophores in biological tissue that only respond to very specific wavelengths. Coherent photons are organized where non-coherent photons are not. This property is important to minimize photon scatter as light interacts with tissue. Lastly, since injured tissue is normally deep in the body, laser’s columnated beam helps focus energy in a narrow, direct path which is ideal for treating tissues at depth.
LEDs usually emit light in a small band of wavelengths (~20 nm wide) but cannot emit a single specified wavelength (~1 nm wide). This bandwidth impacts their ability to dial in the wavelength to optimally target desired tissues. Additionally, LEDs produce neither a collimated nor coherent beam, which is less ideal when treating deeper tissues. Lastly, LED’s operate at significantly lower power (wattage) than most lasers, which impacts their ability to reach deeper tissues in smaller windows of time.
When trying to target deeper tissues, wavelength is a critical variable that can play a significant role in the light’s ability to penetrate tissue. But it is not the only determining factor in therapeutic effectiveness. Power is a second variable that also plays a large role in determining both proper use and consistency of outcomes for light-based therapies.4 Lasers are generally capable of producing much higher powers than LEDs, which significantly impacts their ability to reach deeper tissues.
This is due to the concept of therapeutic depth, which involves getting an adequate amount of photonic energy to injured tissue to have a photobiomodulation effect. Since a significant amount of light is lost as it passes through tissue, having more initial power at the surface improves the modality’s ability to provide adequate amounts of energy at depth.
For superficial uses, such wound healing5, therapeutic effects can be achieved with a minimal amount of energy applied to the surface, for which LEDs are well suited. For deeper or more wide-spread conditions, such as fibromyalgia6 or chronic low back pain7, a greater amount of energy must be delivered for a sufficient therapeutic effect to be achieved.
Knowing what types of injuries will be treated with your light-based modality will impact which device will be most beneficial to the practice. LEDs often get a lot of initial attention because they are much cheaper than laser technology. Lasers used to treat deep tissue (that offer a wider range of power), however, give providers the most flexibility in terms of treatment capabilities as they can be used to treat both superficial and deep conditions. Weighing the considerations listed above should help you make the right decision when it comes time to purchase one of these devices.
2. Kim, W.-S., & Calderhead, R. G. (2011). Is light-emitting diode phototherapy (LED-LLLT) really effective? Laser Therapy, 20(3), 205–215. http://doi.org/10.5978/islsm.20.205
3. Azadgoli B, Baker RY. Laser applications in surgery. Annals of Translational Medicine. 2016;4(23):452. doi:10.21037/atm.2016.11.51.
4. Knappe, V & Frank, Frank & Rohde, Ewa. Principles of Lasers and Biophotonic Effects. Photomedicine and Laser Surgery. 2004;22: 411-7. 10.1089/pho.2004.22.411.
5. Harry T. Whelan, et al. “Effect of NASA Light-Emitting Diode Irradiation on Wound Healing .” Journal of Clinical Laser Medicine & Surgery. July 2004, 19(6): 305-314. https://doi.org/10.1089/104454701753342758
6. Panton, Lynn, et al. “Effects of Class IV Laser Therapy on Fibromyalgia Impact and Function in Women with Fibromyalgia.” The Journal of Alternative and Complementary Medicine. May 2013, 19(5): 445-452. https://doi.org/10.1089/acm.2011.0398
7. Vallone, Francesco, et al. “Effect of Diode Laser in the Treatment of Patients with Nonspecific Chronic Low Back Pain: A Randomized Controlled Trial.” Photomedicine and Laser Surgery. August 2014, 32(9): 490-494.
Contributed by Mark Callanen, PT, DPT, OCS
Photobiomodulation therapy (also known as laser therapy) is a nonthermal, photochemical process that results in beneficial therapeutic outcomes, including the alleviation of pain and inflammation, immunomodulation, and promotion of wound healing and tissue regeneration. It also promotes muscle relaxation and increased local circulation. While this sounds similar to the effects of ultrasound, the two modalities are actually quite different.
Therapeutic ultrasound works by a piezoelectric effect. A vibrating crystal in the head creates cavitation in tissue via sound waves. This cavitation produced in therapeutic ultrasound machines causes friction among water molecules and in turn creates heat in the tissue. This warming effect promotes local vasodilation.
When deep tissue lasers are used, there is often minor heating at the epidermis, as melanin and hair will absorb light energy. While the minor heating can help relax muscles and decrease pain, the heat sensed at the skin is not what creates the improvements in microcirculation and local vasodilation – these effects result from a process called photobiomodulation (PBM).1,2
Local perfusion increases after specific wavelengths of light reach the inner mitochondrial membrane of injured cells and excite the chromophore Cytochrome C. When energized adequately, activated Cytochrome C oxidase frees up bound nitrous oxide (NO), which improves vasodilation in the local area and promotes healing.3 In addition to freeing up NO, there are a host of other beneficial cellular interactions that take place during photobiomodulation that positively influence the inflammatory cascade and improve tissue healing by impacting the mitochondria directly.3
The chart below shows several differences between the laser and ultrasound modalities. Given that laser’s mechanism of action impacts the metabolism of the mitochondria and ultrasound does not, the influence the two modalities has on tissue(s) is quite different.
An added benefit of PBM therapy is that it can be used over metal implants, while ultrasound cannot. Since light is simply reflected off metal, use over total joints is not a contraindication. Given laser’s ability to have positive effects on inflammation and pain, it is the ideal modality to use on post-operative total joint patients with pain and swelling.
As research continues to build and better outcomes are achieved consistently, health professionals are increasingly viewing PBM therapy as a clinical asset worth investing in. Unlike ultrasound, laser’s ability to quickly impact pain, inflammation, and tissue repair make it a very versatile modality – one that clinicians find themselves reaching for again and again. So if you are looking at bringing a modality into into your practice, take a look at deep tissue therapy lasers – the only thing you will regret is not getting one sooner.
1. Mrowiec J 1997, ‘Analgesic effect of low-power infrared laser radiation in rats’, Proc SPIE, vol. 3198,no. 83, pp. 83-89. 2. Asagai, Y. 2000, “Thermagraphic study of low level laser for acute phase injury”, Las Ther, vol 12. pp 31-33. 3. Chris E. Stout, Matt Kruger and Jeffrey Rogers, (Eds)- © 2011 Bentham Science Publishers Ltd. Current Perspectives in Clinical Treatment & Management in Workers’ Compensation Cases, 2011, 15: 191-2.
Contributed by Mark Callanen, PT, DPT, OCS
Treating headaches (HA) can be challenging, and they make up a sizable portion of many practices. Head pain is the 5th leading cause of visits to emergency departments in the U.S. and accounted for 1.2% of all outpatient visits.1 With approximately 300 classifications of different types of HA2, learning how to differentiate and treat this problem challenges even the most experienced clinicians.
Cervicogenic headache (CGHA) is one of the most common and treatable types of HA, accounting for 14-18% of all HA.3 Characteristics of CGHA include unilateral headache that doesn’t change side; pain that is exacerbated with neck movements or abnormal postures; pain produced with pressure applied over the supero-posterior ipsilateral neck; ipsilateral neck, shoulder, or arm pain; and restricted cervical spine range of motion (ROM).4
When inflammation and/or pain is being generated from one or more of the upper 3 cervical segments, it can cause this type of HA.5 CGHA has a very distinct unilateral pattern, often traveling from the occipital area towards the ipsilateral side of the forehead and face due to the involvement of the trigeminal nuclei. Unlike most headaches, it can be reproduced via physical exam. Once CGHA has been confirmed it is then a matter of deciding what treatment to use on the offending segment(s). But what treatment is best?
Any manual treatment that helps improve the segmental mobility of the involved segment(s) will usually help the condition. This can include soft tissue work, mobilization, and/or manipulation. Following up with ROM exercises, postural correction, and using modalities to minimize local pain complaints is standard practice for most clinicians.
For an even better outcome, you may want to consider adding a tool known as “photobiomodulation therapy” to this manual approach. Also commonly known as “laser therapy”, PBM therapy has been shown to significantly help with chronic and acute cervical pain.6
The laser helps the body reduce pain and inflammation via a process known as photobiomodulation.7-10 If applied to the upper cervical area, it has the potential to help patients dealing with CGHA by impacting inflammation, improving cervical muscle endurance, and reducing pain as it relates to peripheral nociception.
PBM has been shown in both in-vitro and in-vivo studies to reduce inflammation by impacting levels of prostaglandin E2, interleukin 1β, and tumor necrosis factor α.11 Animal studies have also confirmed that the anti-inflammatory effects of PBM therapy are similar to pharmacological agents such as celecoxib (Celebrex), meloxicam, diclofenac, and dexamethasone.12,13 Additionally, PBM therapy stands out as an ideal modality choice when treating zygapophyseal joint inflammation due to its ability to deeply penetrate tissue.14,15
Since photobiomodulation promotes increased ATP production in the mitochondria of muscle cells, endurance is significantly improved by laser therapy due to decreases in oxidative stress on muscle tissue.16,17 Additionally, the added ATP production enhances the contractile function of skeletal muscle by attenuating strength loss.18,19 These positive changes in muscle output should help improve reconditioning postural muscles in the neck and upper back as length tension characteristics are being adjusted with corrective exercises and postural cueing.
Finally, the mechanism for delivering pain from the periphery can be impacted with PBM therapy as it inhibits transmission at the neuromuscular junction which has been shown to reduce myofascial pain and trigger points.20,21 Soft tissue dysfunction is commonly associated with pain in the upper cervical spine and HA. Additionally, Aδ and C afferent fibers, which convey peripheral nociception, can have their transmission rates reduced by laser, leading to a reduction in pain perception.6 Slowing peripheral nociception could reduce one of the key drivers of CGHA.
The impact of correctly diagnosing CGHA and isolating the irritable segment(s) in the neck is a critical step in helping these individuals. Having the knowledge and skill to help them is not common place in all out-patient clinics. A growing number of clinics are utilizing PBM therapy with their patients and might find the use of the laser a game changer regarding their approach to CGHA, despite not having the highly developed manual skills to isolate and treat the offending segment.
It is easy to see how PBM therapy could help current protocols by reducing local inflammation, improving muscle function of the surrounding muscles, and reducing the nociceptive abilities of the nerves involved with CGHA. Even if you are a clinician with the skill to provide the perfect manual treatment to the upper cervical spine, any one of the characteristics listed above could further improve a CGHA outcome. Imagine if you could add all three…
Patients dealing with both acute and chronic neck pain have already been shown to benefit from PBM6, so why shouldn’t people dealing with CGHA? If your practice treats patients with neck related disorders, you might want to consider a therapeutic laser as the next modality you add to your clinic, regardless of the manual tools that are at your disposal.
References1. Smitherman TA, Burch R, Sheikh H, Loder E. The prevalence, impact, and treatment of migraine and severe headaches in the United States: a review of statistics from national surveillance studies. Headache. 2013 Mar;53(3):427-36. 2. Heachache Classification Subcommittee of the Internoational Headache Society. The international classification of headache disorders, 2nd Edition. Cephalagia 2004; 24: suppl 1. 3. G. Zito, G. Jull , I. Story. Clinical tests of musculoskeletal dysfunction in the diagnosis of cervicogenic headache. Manual Therapy 11 (2006) 118–129. 4. Sjaastad O, Fredriksen TA, Pfaffenrath V. Cervicogenic headache: diagnostic criteria. the cervicogenic headache international study group. Headache. 1998;38:442–5. 5. Lord S, Bogduk N. The cervical synovial joints as sources of posttraumatic headache. Journal of Musculoskeletal Pain 1996;4:81–94. 6. Chow, RT. Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis of randomized placebo or active-treatment controlled trials. Lancet 2009; 374: 1897–908. 7. Sattayut S, Hughes F, Bradley P. 820nm gallium aluminium arsenide laser modulation of prostaglandin E2 production in interleukin I stimulated myoblasts. Laser Therapy 1999; 11: 88–95. 8. Sakurai Y, Yamaguchi M, Abiko Y. Inhibitory eff ect of low-level laser irradiation on LPS-stimulated Prostaglandin E2 production and cyclooxygenase-2 in human gingival fibroblasts. Eur J Oral Sci 2000; 1081: 29–34. 9. Aimbire F, Albertini R, Pacheco MTT, et al. Low-level laser therapy induces dose-dependent reduction of TNFα levels in acute inflammation. Photomed Laser Surg 2006; 24: 33–37. 10. Bjordal JM, Johnson MI, Iverson V, Aimbire F, Lopes-Martins RAB. Photoradiation in acute pain: a systematic review of possible mechanisms of action and clinical effects in randomized placebocontrolled trials. Photomed Laser Surg 2006; 24: 158–68. 11. Bjordal JM, Lopes-Martins RAB, Iversen VV. A randomised, placebo controlled trial of low level laser therapy for activated achilles tendinitis with microdialysis measurement of peritendinous prostaglandin E2 concentrations. Br J Sports Med 2006; 40: 76–80. 12. Campana V, Moya M, Gavotto A, et al. The relative effects of He-Ne laser and meloxicam on experimentally induced inflammation. Laser Therapy 1999; 11: 36–42. 13. Albertini R, Aimbire F, Correa FI, et al. Eff ects of diff erent protocol doses of low power gallium–aluminum–arsenate (Ga–Al–As) laser radiation (650 nm) on carrageenan induced rat paw oedema. J Photochem Photobiol B 2004; 27: 101–07. 14. Enwemeka C. Attenuation and penetration of visible 632・8nm and invisible infrared 904nm light in soft tissues. Laser Therapy 2001; 13: 95–101. 15. Gursoy B, Bradley P. Penetration studies of low intensity laser therapy (LILT) wavelengths. Laser Therapy 1996; 8: 18. 16. Leal Junior EC, Lopes-Martins RA, Vanin AA, et al. Effect of 830 nm low-level laser therapy in exercise-induced skeletal muscle fatigue in humans. Lasers Med Sci 2009; 24: 425–31. 17. Leal Junior EC, Lopes-Martins RA, Dalan F, et al. Effect of 655-nm Low-Level Laser Therapy on Exercise-Induced Skeletal Muscle Fatigue in Humans. Photomed Laser Surg 2008; 26: 419–24. 18. Kelly A. Larkin-Kaiser, KA. Near-Infrared Light Therapy to Attenuate Strength Loss After Strenuous Resistance Exercise. Journal of Athletic Training 2015;50(1):45–50. 19. Nampo, FK. Low-level phototherapy to improve exercise capacity and muscle performance: a systematic review and meta-analysis. Lasers Med Sci (2016) 31:1957–1970. 20. Nicolau R, Martinez M, Rigau J, Tomas J. Neurotransmitter release changes induced by low power 830nm diode laser irradiation on the neuromuscular junction. Lasers Surg Med 2004; 35: 236–41. 21. Nicolau RA, Martinez MS, Rigau J, Tomas J. Effect of low power 655nm diode laser irradiation on the neuromuscular junctions of the mouse diaphragm. Lasers Surg Med 2004; 34: 277–84.