Evaluation of treatment efficacy of minimally invasive low-level laser therapy system for musculoskeletal diseases

Abstract

Although the mechanism of low-level laser therapy (LLLT) is still unclear, there has been recent interest in using it to treat orthopedic diseases. Numerous studies have developed optical clearing methods to increase the therapeutic efficacy of LLLT because, owing to light scattering and absorption, light energy decreases when penetrating tissue.In this study, we investigated methods that enhance the therapeutic efficacy of LLLT. First, we evaluated the effects of individual and combination applications of two optical clearing methods: hyperosmotic chemical agents (HCAs) and compression. The results showed that the transmitted light energy increased when the methods were combined compared to individual applications. However, the inherent light energy loss problem of LLLT was still present. Therefore, we developed the minimally invasive laser needle system (MILNS) to address the inherent light energy loss problem during tissue penetration and applied it to three orthopedic diseases: osteoporosis, arthritis, and muscle atrophy. MILNS employs a fine hollow needle that delivers light to targets in deep tissue without light scattering. The therapeutic efficacy of MILNS was evaluated by micro computed tomography (μ-CT) and histological analysis. The bio-stimulatory effects of MILNS on orthopedic diseases were found to produce positive therapeutic outcomes such as the suppression of bone loss, arthritis, and muscle atrophy progression. Thus, MILNS improved the therapeutic efficacy of LLLT because the three orthopedic diseases had controversial results with regard to the bio-stimulation of LLLT.Although we realized positive therapeutic outcomes, the therapeutic parameters of MILNS have to be investigated because the response of each biological cell to the wavelength and light dosage differed. Based on the results of this study, we expect that MILNS may be developed as a

treatment modality that enhances the therapeutic efficacy of LLLT.