Effect of photobiomodulation on femoral fracture specimens in rats with experimentally induced osteoporosis

Bone repairing is a complex mechanism that demands good bodily conditions to happen; however, some systemic conditions can negatively influence this process, such as some chronic inflammatory conditions and changes in the microarchitecture of bone tissue. This study aims to evaluate the potential of Photobiomodulation (PBM) therapy using an infrared diode laser (808 nm) in the bone repair of femoral fractures in osteoporotic rats. A total of 24 adult rats, aged 6 months old, were initially subjected to bilateral ovariectomy, to induce osteoporosis. After 90 days, the rats were subjected to femoral fractures and fixation with plates and screws of the 1.5 mm system. The rats were randomly divided into PBM (n = 9), those that were irradiated in the trans-surgical period with low-power laser, and WPBM (n = 9), those that were not irradiated. For the PBM group, a low-power laser with a 808 nm wavelength, 0.0283 cm<sup>2</sup> spot area, 100 mW power was applied for 60 s, with 6 J/point energy, 212 J/cm<sup>2</sup> energy density, single and punctual application in five determined points around the entire reparative "gap," following the applications once per day, during eight days of the postoperative period. The animals were euthanized at 14 and 42 days after surgery, and the samples were sent for microtomographic, histometric, and immunohistochemical analyses. Data were analyzed using the two-way ANOVA test and the Holm-Sidak post-test when p < 0.05. The microtomographic analysis showed no differences between the groups analyzed in any experimental period (p > 0.05). Histometric analysis showed a greater area of newly formed bone for the PBM group compared to the WPBM group (p < 0.05), corroborating the immunohistochemical result, which shows greater labeling of TGF-B and VEGF. It can be concluded that the use of PBM therapy by infrared laser irradiation improved the repair of fractures in femurs of osteoporotic rats and it should be considered in future clinical research.