[show abstract][hide abstract] ABSTRACT: Interference is an important feature of the waves. When two or more in phase light waves meet, a new and reinforced wave is generated. Shoulder pain is a common clinical problem and laser is one of the treatments frequently used to relieve it.
To test the safety of interferential laser therapy generated by two independent low level lasers and compare its effectiveness with conventional single laser therapy in the reduction of shoulder musculoskeletal pain and associated disability.
Randomised and single-blind controlled clinical trial.
Physiotherapy Unit and Rehabilitation Department of Ramon y Cajal University Hospital (Madrid).
200 patients with shoulder musculoskeletal pain were randomly assigned in two groups, 100 people each.
Group I, experimental (n=100) received interferential laser, placing two probes opposite each other over the shoulder joint. Group II, control (n=100) received conventional laser therapy, using a single probe along with a second inactive dummy probe. Lasers used were GaAlAs diode (810 nm, 100 mW), in continuous emission. Laser was applied in contact mode through ten sessions, on 5 shoulder points (7 Joules/point) per session.
visual analogue scale (VAS) score and shoulder pain disability index (SPADI), recorded before and after laser treatment.
There were no differences between both groups in the reduction of pain, either assessed by VAS scale (median difference=0, 95% CI of the difference = -.6 to .5, p = 0.81) or SPADI index (median difference = .4, 95% CI of the difference = -2.9 to 3.8, p = 0.80), using the Mann-Whitney U-test. Comparison between the scores recorded before and after the treatment, within each group, showed significant differences for VAS during movement (median difference=3, 95% CI of the difference = 2.07 to 4, p < 0.001) and SPADI index (median difference=3.5, 95% CI of the difference = 2.67 to 3.85, Wilcoxon test, p < 0.001), for both groups.
In this study, the application of two low level lasers in order to generate interference inside the irradiated tissue showed to be a safe therapy. Both interferential and conventional laser therapy reduced shoulder pain and disability. Nevertheless, differences between them were not detected. Future research in this field could include applying this technique with other laser parameters or application forms.
[show abstract][hide abstract] ABSTRACT: Objectives: To test the safety of the diode light therapy and evaluate the advantages of the interferential effect of two light probes versus a conventional light probe in the relief of shoulder pain and disability caused by shoulder tendinopathies.Design: Randomized single-blind pilot study.Setting: Clinical electrotherapy unit.Participants: A total of 30 patients with shoulder pain from tendinopathies.Interventions: The patients were randomly assigned into two groups. Group 1 (n = 15) received interferential light therapy generated by two independent and identical cluster probes composed of light emitting and superluminescent diodes. Similarly, two applicators were applied in group 2 (n = 15), but only one was active, as in conventional clinical therapy. Each multi-diode cluster probe was composed of seven light-emitting diodes at 600 nm and 12 superluminescent diodes at 950 nm.Main outcome measures: Pain was evaluated by visual analogue scale (VAS) at day, at night and during several shoulder movements. Shoulder functional status was measured by means of the University California Los Angeles scale (UCLA).Results: Comparison between both treatments using the Mann-Whitney U-test showed better results for the interferential treatment. There were significant differences in pain reduction during abduction (P < 0.05) and external rotation (P < 0.05), with pain reductions in abduction and external rotation of 1.5 (± 1.3) and 0.5 (± 1.0) respectively.Conclusion: Interferential light therapy was safe and effective regarding the shoulder pain reduction during abduction and external rotation movements. The estimated size sample needed for future two-treatment parallel-design studies will require about 60 patients.