Photobiomodulation for Tendinopathy: A Review of Preclinical Studies

The outcomes of clinical studies utilizing Photobiomodulation on tendon disorders are not homogeneous and since its design depends on preclinical studies utilizing animal models as a prerequisite, this review investigates the literature to help extrapolate preclinical evidence-based outcomes (safety and efficacy) into clinical treatment options. PubMed and Embase databases were searched for tendinopathy, Photobiomodulation and preclinical studies with inclusion criteria were restricted to in vivo animal studies using rat's models subjected to partially injured tendons. Data extracted were methodology quality and design, light parameters, study methods, and outcomes. Twenty two articles were included, half of them were partially transected, while the other half were partially traumatized. The most common wavelengths used were 660, 830, and 904 nm with energy density range between 1 and 17 J/cm2 and applied mostly daily. Fourteen studies (64%) relied merely on a single assessment. Histological measurements were the most common method of evaluation (75%) and 35% of studies used chemical measures. Mechanical outcomes were reported in four, and two studies demonstrate significant effects. Photobiomodulation has the potential to enhance tendon structure and function, however, inevitable embedded heterogeneity related to study design and quality of methods, light parameters delivered, and evaluations methods renders the ability to establish unified treatment parameters difficult. Adjustments for variability within preclinical studies might lead to better designing of clinical studies. It is recommended to embrace a protocol for designing and performing preclinical studies to improve its quality. Moreover, it is recommended to prove efficacy using at least two evaluation methods and apply Photobiomodulation as a combined varying energy/wavelength protocol (several energies with several wavelengths). Clinical relevance: Establishing a proof of concept for Photobiomodulation that may lead to further high-quality clinical studies, in which the applicable parameters can be determined.