Abstract
Low reactive-level laser therapy (LLLT) has been reported as having a beneficial effect in the therapy of rheumatoid arthritis. Some concerns have been expressed about the possible photothermal damage to articular tissue, for example the synovial membrane, following extended doses of LLLT such as are usually applied. The present study was designed to assess qualitatively and quantitatively the possible photothermal damage to articular membranous tissue foltowing an extended exposure (30 min) of infrared laser radiation on the rat synovial membrane, both through the capsule and with the capsule dissected away to aliow direct exposure. A third group of unirradiated anima]s acted as the control. The laser was a gallium aluminium arsenide (GaAlAs) diode laser system, delivering 60 mW, to a total spot size from three diodes of approximately 0.3 cm2, power density ≅ 0.2 W/cm2, incident energy 108 J, energy density 360 J/cm2. Evaluation of any photoinduced thermal damage was made both macroscopically and with blinded microscopic histological assessment. No damage was macroscopically visible, and no difference was found in the histology of the control, indirectly and directly-irradiated synovial membrane specimens. The authors conclude that, at the wavelength and delivery parameters given, even with extended dosage, laser therapy has no adverse photothermal effects on encapsulated or exposed synovial membrane in vivo.
