Thermal effects during laser treatment of articular cartilage

Justification: Osteoarthritis is one of the most common diseases that lead to disability. Arthroscopic laser treatment of articular cartilage is an effective and promising method of treating osteoarthritis, but its technique can be improved due to the results of this study.Purpose: To determine the degree of thermal effect of two-wave near-infrared laser radiation on articular cartilage during laser treatment.Methods: Samples of articular cartilage of a bull were exposed to infrared laser radiation with various parameters. During exposure, the distance from the end of the fiber to the sample was 2 mm. At the same time, the surface temperature of the cartilage was measured using a thermal imaging camera, and the temperature in the sample volume was measured point-by-point using a thermocouple.Results: The change in the surface temperature of cartilage samples when exposed for 2 s to radiation with λ= 0.97 µm/7 W was ΔT=2.4±0.5 °C, and with λ=µm/5W - ΔT=21.1 °C. Exposure for 2 hours with two-wave radiation with λ= 1.55/5 W + λ=0.97 microns / 3 W led to an increase in surface temperature by 21.8 ± 0.5 °C. When exposed for 2 seconds to two-wave radiation with λ= 1.55/ 5 W + λ=0.97 microns / 3 W, the increase in the temperature of the biological tissue at a depth of 1 mm was: on the optical axis - ΔT =11 ° C, at a distance of 1 mm from the axis - ΔT=4 ° C, at a distance of 2 mm from axes - ΔT=3 °C. Conclusions: 1) When using two-wave radiation λ= 1.56 microns and λ=0.97 microns, the greatest contribution to the heating of cartilage tissue is made by λ= 1.56 microns absorbed in the surface areas, while radiation λ=0.97 microns is absorbed weaker and penetrates deeper layers. 2) The maximum increase in cartilage temperature occurs within 1 mm from the axis of propagation of laser radiation. Due to this, laser treatment makes it possible to effectively achieve "smoothing" of the cartilage surface with minimal impact on tissues outside the treated area. 3) Laser radiation with the parameters used, in addition to purely thermal effects on cartilage tissue, can trigger the processes of its regeneration by the mechanisms of mechanobiology and photobiomodulation.