Athletic Training and Sports Health Care

Sports Medicine Digest 

Photobiomodulation Reduces Pain in Patients With Shoulder Tendinopathy

Kristen M. Agena, MS, ATC, CSCS, CES; Cailee E. Welch Bacon, PhD, ATC; Tamara C. Valovich McLeod, PhD, ATC, FNATA

Abstract

Haslerud S, Magnussen LH, Joensen J, Lopes-Martins RA, Bjordal JM. The efficacy of low-level laser therapy for shoulder tendinopathy: a systematic review and meta-analysis of randomized controlled trials. Physiother Res Int. 2015;20:108–125.

Clinical Question: A systematic review and meta-analysis was conducted to understand the effectiveness of low level laser therapy (LLLT) in reducing pain in patients with shoulder tendinopathy.

Data Sources: Studies published between 1987 and 2012 were identified for review if they included (1) randomized controlled trials, controlled clinical trials, or trials with crossover design; (2) human patients experiencing pain and functional disability due to a diagnosed shoulder tendinopathy or subacromial impingement; and (3) incorporated LLLT within a range of 632 to 1,064 nm over the pathological tendon, acupuncture point, or trigger point to one group in a controlled trial.

Study Selection: Of 395 studies initially identified by the selected search terms, 17 studies met all inclusion criteria and were used in the meta-analysis.

Data Extraction: Pain was assessed with the Visual Analog Scale (VAS).

Main Results: Positive effects were reported in 11 studies, whereas no significant effects were reported in 6 studies, with 4 of those noted to have inadequate dosage. Eleven of 15 (73%) studies addressing pain relief favored LLLT over no treatment, placebo, or other modalities. Nine of these 11 studies had tests for overall effect (Z scores) that were statistically significant (P < .05) and had a minimally important change score of 14 or greater on the VAS. When trials with an inadequate dosage based on World Association for Laser Therapy (WALT) recommendations were removed, 10 of 11 (90%) studies reported statistically significant findings for pain reduction.

Conclusions: The primary outcome of pain reduction was significantly improved when LLLT was performed as a single therapy and when it was combined with exercise or a multimodal physiotherapy plan. Pain improved from 73% to 90% after LLLT when recommended WALT dosage parameters were followed. These findings support the use of LLLT for the treatment of shoulder tendinopathies when the recommended dosage is used.

Summary: Photobiomodulation (PBM) entails the physiological mechanisms that are affected by the therapeutic use of light known as PBM therapy (PBMT). PBMT may use single or multiple non-ionizing light sources, including laser diodes, superluminescent diodes, and light-emitting diodes, in the visible and infrared spectrum. According to the North American Association for Photobiomodulation Therapy (NAALT), PBM involves photo-physical and photochemical events in endogenous chromophores that may result in the reduction of pain or inflammation (inhibitory effect) or the promotion of wound healing and tissue regeneration (stimulatory effect).1 Since September 2014, the use of the terms PBM and PBMT has been encouraged by the NAALT and WALT over other terms, including LLLT, due the wide variety of electromagnetic energy sources, parameters, and therapeutic benefits it encompasses.

Clinicians treating shoulder tendinopathies may attempt to reduce pain with a variety of interventions. In 2002, the U.S. Food and Drug Administration initially approved the use of lasers for treating pain originating in the head and neck and pain associated with carpal tunnel syndrome and arthritis,2 but the list of conditions has been expanded over the past 15 years. Since 2002, systematic reviews and meta-analyses have addressed the effectiveness of PBMT to treat a variety of musculoskeletal conditions, but the meta-analysis by Haslerud et al.3 is the only study to focus solely on shoulder tendinopathies. When used as a monotherapy under the proper treatment parameters, PBMT had a significant effect on decreasing pain in comparison to placebo and ultrasonography. However, most clinicians use a multifaceted approach to treating patients, including the use of multiple modalities and a variety of exercise…

Haslerud S, Magnussen LH, Joensen J, Lopes-Martins RA, Bjordal JM. The efficacy of low-level laser therapy for shoulder tendinopathy: a systematic review and meta-analysis of randomized controlled trials. Physiother Res Int. 2015;20:108–125.

Clinical Question: A systematic review and meta-analysis was conducted to understand the effectiveness of low level laser therapy (LLLT) in reducing pain in patients with shoulder tendinopathy.

Data Sources: Studies published between 1987 and 2012 were identified for review if they included (1) randomized controlled trials, controlled clinical trials, or trials with crossover design; (2) human patients experiencing pain and functional disability due to a diagnosed shoulder tendinopathy or subacromial impingement; and (3) incorporated LLLT within a range of 632 to 1,064 nm over the pathological tendon, acupuncture point, or trigger point to one group in a controlled trial.

Study Selection: Of 395 studies initially identified by the selected search terms, 17 studies met all inclusion criteria and were used in the meta-analysis.

Data Extraction: Pain was assessed with the Visual Analog Scale (VAS).

Main Results: Positive effects were reported in 11 studies, whereas no significant effects were reported in 6 studies, with 4 of those noted to have inadequate dosage. Eleven of 15 (73%) studies addressing pain relief favored LLLT over no treatment, placebo, or other modalities. Nine of these 11 studies had tests for overall effect (Z scores) that were statistically significant (P < .05) and had a minimally important change score of 14 or greater on the VAS. When trials with an inadequate dosage based on World Association for Laser Therapy (WALT) recommendations were removed, 10 of 11 (90%) studies reported statistically significant findings for pain reduction.

Conclusions: The primary outcome of pain reduction was significantly improved when LLLT was performed as a single therapy and when it was combined with exercise or a multimodal physiotherapy plan. Pain improved from 73% to 90% after LLLT when recommended WALT dosage parameters were followed. These findings support the use of LLLT for the treatment of shoulder tendinopathies when the recommended dosage is used.

Summary: Photobiomodulation (PBM) entails the physiological mechanisms that are affected by the therapeutic use of light known as PBM therapy (PBMT). PBMT may use single or multiple non-ionizing light sources, including laser diodes, superluminescent diodes, and light-emitting diodes, in the visible and infrared spectrum. According to the North American Association for Photobiomodulation Therapy (NAALT), PBM involves photo-physical and photochemical events in endogenous chromophores that may result in the reduction of pain or inflammation (inhibitory effect) or the promotion of wound healing and tissue regeneration (stimulatory effect).1 Since September 2014, the use of the terms PBM and PBMT has been encouraged by the NAALT and WALT over other terms, including LLLT, due the wide variety of electromagnetic energy sources, parameters, and therapeutic benefits it encompasses.

Clinicians treating shoulder tendinopathies may attempt to reduce pain with a variety of interventions. In 2002, the U.S. Food and Drug Administration initially approved the use of lasers for treating pain originating in the head and neck and pain associated with carpal tunnel syndrome and arthritis,2 but the list of conditions has been expanded over the past 15 years. Since 2002, systematic reviews and meta-analyses have addressed the effectiveness of PBMT to treat a variety of musculoskeletal conditions, but the meta-analysis by Haslerud et al.3 is the only study to focus solely on shoulder tendinopathies. When used as a monotherapy under the proper treatment parameters, PBMT had a significant effect on decreasing pain in comparison to placebo and ultrasonography. However, most clinicians use a multifaceted approach to treating patients, including the use of multiple modalities and a variety of exercise protocols. This meta-analysis found significant improvement in pain when PBMT was used as an adjunct to exercise and in conjunction with other modalities and exercise. Despite studies supporting the use of lasers to diminish pain, 6 of 17 studies did not provide evidence to support the use of laser. However, 4 of 6 studies were considered to have used inadequate dosages based on dosage-dependent outcomes noted in a study by Tumilty et al.4 and compared to WALT dosage recommendations.5

There are numerous factors for clinicians to understand regarding being able to provide adequate dosing with PBM devices. The wavelength(s) emitted, ranging from 400 to 1,300 nm, will dictate the depth of penetration and whether the photons (light energy) reach the target tissue. The classification of the light or laser unit based on the power output measured in watts (W) or milliwatts (1 mW = 1 × 10−3 W) affects the total amount of energy and the risk for biological damage that can occur. The power output is affected by frequency (Hz), duty cycle, pulse width, or whether the energy emitted is continuous or pulsed. The components of PBM are dependent on how well the device has been calibrated, a factor that was implicated in 3 of 4 studies that had an inadequate dosage.3

The range of factors affecting dosing parameters are significant concerns to clinicians who want to better understand PBMT for their patients. In 2010, the WALT provided PBMT minimum dosage recommendations for class 3B lasers over various shoulder tendons, based on specific wavelengths of the light emitted (Table 1), and suggested daily treatments for 2 weeks or treatment every other day for 3 to 4 weeks, with irradiation occurring over most of the pathological tissue in the tendon or synovia.5 The aforementioned recommendations should be critically evaluated by clinicians because they are based on studies incorporating specific wavelengths of laser light and classes of therapeutic lasers. In many clinics, the PBM devices may range from class 1 to 4 and incorporate individual or combination wavelength diodes that are different than the wavelength diodes cited in studies. These factors can significantly affect the variability in the power and energy output of those units and thus the effectiveness of the treatment.

WALT Shoulder Tendinopathy Dosage Recommendations5

Table 1:

WALT Shoulder Tendinopathy Dosage Recommendations5

The WALT dosage information is described in terms of joules (J) of energy and energy density as J/cm2. Although some manufacturers provide dosing parameters of their devices in terms of J or J/cm2, different parameters such as Hz may be used. However, this confusion can be addressed by calculating average power of the device by using the formula: Average Power (W) = Frequency (Hz) × Peak Power (W) × Pulse Rate (s). The energy dose calculation can then be determined using the formula: Energy (J) = Power (W) × Treatment Time (s), whereas Treatment Time (s) = energy (J) / Power (W). These formulas should enable a clinician to calculate the total energy and time required to apply the WALT minimum dose per point (J/cm2) recommendation. In some cases, if the requisite information is not readily available in the operating or treatment manuals that come with the device, the clinician may need to contact the manufacturer directly to clarify the device's technical specifications to be able to properly address output parameters for their device.

The number of diodes for each energy source, the irradiation area point size (cm2) of the overall aperture opening, and whether different applicator heads can be attached affect the area and thus the power density (W/cm2) of the output. The power density in turn affects the energy density (J/cm2). These are important because the number and size of treatment locations affect the total tissue area (total cm2) that needs to be treated. The total treatment area divided by the aperture area plays a part in determining the total treatment time per session. Finally, the distance from the light source to the target tissue, tissue pigmentation, and makeup of tissue content will affect energy transmission and absorption, and thus the length of the treatment session. Because most published PBM studies used individuals with light skin, the transmission of PBM energy into darker skinned individuals will likely cause photons to be absorbed more superficially, leading to the need to further evaluate the effectiveness of and set-up parameters for individuals with varying amounts of pigmentation.

It is important to note that WALT recommendations primarily involve minimum dosage suggestions for specific wavelengths. Similar to most treatment interventions, there is a biphasic dose-response with PBM, meaning there is a therapeutic range with doses below having no effect, whereas doses above the range cause tissue damage. Haslerud et al.3 found studies that reported a positive reduction in shoulder tendinopathy pain had power outputs that ranged from 3 to 100 mW and energy outputs of 0.9 to 4.5 J per point. Tumilty et al.4 incorporated WALT recommendations5 and described an effective range for power density between 20 and 320 mW/cm2 and energy density between 1.8 to 19.2 J/cm2 for various tendinopathies depending on the depth of the tendons and wavelength of light used. However, the therapeutic range for many tissues is still being studied and best practices have not been determined for many tissue pathologies relative to specific PBM wavelengths and combination wavelength units.

Due to the variability in the research on PBM, clinicians must critically appraise the available evidence to determine which studies are applicable to their individual device. Health care providers should familiarize themselves with PBM devices and follow the manufacturer's suggestions and recommended dosing guidelines in an effort to improve patient outcomes. Although efforts have been made to determine the effectiveness of various PBM therapies, it is important that clinicians and researchers continue gathering and sharing data on the most beneficial dosage recommendations for treating not only shoulder tendinopathies but other musculoskeletal conditions so health care providers may have another effective tool to treat their patients.

References

  1. North American Association for Photo-biomodulation Therapy. NAALT. www.naalt.org. Updated January 2015. Accessed May 30, 2017.
  2. Fulop AM, Dhimmer S, Deluca JR, et al. A meta-analysis of the efficacy of laser phototherapy on pain relief. Clin J Pain. 2010;26:729–736.
  3. Haslerud S, Magnussen LH, Joensen J, Lopes-Martins RA, Bjordal JM. The efficacy of low-level laser therapy for shoulder tendinopathy: a systematic review and meta-analysis of randomized controlled trials. Physiother Res Int. 2015;20:108–125. doi:10.1002/pri.1606 [CrossRef]
  4. Tumilty S, Munn J, McDonough S, Hurley DA, Basford JR, Baxter GD. Low level laser treatment of tendinopathy: a systematic review with meta-analysis. Photomed Laser Surg. 2010;28:3–16. doi:10.1089/pho.2008.2470 [CrossRef]
  5. World Association for Laser Therapy. Dosage recommendations. http://waltza.co.za/documentation-links/recommendations/dosage-recommendations. Published April 2010. Accessed September 24, 2016.

WALT Shoulder Tendinopathy Dosage Recommendations5

DosagePoint Size (cm2)Minimum Location (J/point)Minimum Total (J)
904-nm GaAs laser, > 5 mW mean output, 30 to 600 seconds irradiation time
  Supraspinatus2 to 324
  Infraspinatus2 to 324
  Biceps brachii2 to 32
780- to 860-nm GaAlAs laser, 5 to 500 mW mean output, 20 to 300 seconds irradiation time
  Supraspinatus2 to 348
  Infraspinatus2 to 348
  Biceps brachii1 to 26
Authors

From the Athletic Training Program (KMA, CEWB, TCVM) and School of Osteopathic Medicine in Arizona (CEWB, TCVM), A. T. Still University, Mesa Arizona; and Luther College, Decorah, Iowa (KMA).

The authors have no financial or proprietary interest in the materials presented herein.

Correspondence: Kristen M. Agena, MS, ATC, CSCS, CES, Luther College, 700 College Drive, Decorah, IA 52101. E-mail: agenkr01@luther.edu

10.3928/19425864-20190207-04

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