Effect of irradiation with a low-intensity diode laser on the metabolism of equine articular cartilage in vitro

Objective-To determine whether irradiation with a low-intensity diode laser , which produces radiation at a wavelength of 810 nm, will induce nontherma l enhancement of chondrocyte metabolism. Sample Population-144 grossly normal articular cartilage explants aseptical ly harvested from the femoral condyles of 6 adult horses. Procedure-Treated cartilage explants were irradiated with a diode laser at 1 of 7 fluence levels that ranged from 8 to 1,600 J/cm(2). Explants were in cubated for 24 or 72 hours, labeled for 24 hours with ([3)5S]Na2SO4, and as sayed for newly synthesized sulfated glycosaminoglycan (GAG; measured incor poration of (SO4)-S-35) and endogenous GAG, chondroitin 6-sulfate (CS), and keratan sulfate (KS) content, using a dimethylmethylene blue assay. Laser- induced temperature changes were measured during irradiation with a diode l aser and a neodymium:yttrium aluminum garnet (Nd:YAG) laser, which produces radiation at a wavelength of 1,064 nm, using conditions that were reported in previous studies to increase explant metabolism. Results-After incubation for 24 or 72 hours, rate of (SO4)-S-35 uptake or e ndogenous GAG, CS, or KS content in irradiated explants was not significant ly different than in nonirradiated explants. Cartilage temperature Increase d < 4.75 C during diode laser application. Cartilage temperature increased 5 to 12 C during Nd:YAG laser application. Conclusions-Minimal thermal increases in cartilage explants with use of a l ow-intensity diode laser resulted in no change in proteoglycan metabolism o f chondrocytes. An increase in tissue temperature over a narrow range with use of a Nd:YAG laser may have contributed to the metabolic alteration of c hondrocytes reported in previous studies.