The thermal effect of monopolar radiofrequency energy on the properties ofjoint capsule - An in vivo histologic study using a sheep model

The purpose of this in vivo study was to analyze the short-term tissue resp onse of joint capsule to monopolar radiofrequency energy and to compare the effects of five power settings at 65 degrees C on heat distribution in joi nt capsule. In 12 mature Hampshire sheep, the medial and lateral aspects of both stifles were treated with monopolar radiofrequency energy under arthr oscopic control in a single uniform pass to the synovial surface. The radio frequency generator power settings were 0, 10, 15, 20, 25, and 30 watts (N = 8/group), The electrode tip temperature was 65 degrees C. Histologic anal ysis at 7 days after surgery revealed thermal damage of capsule at all radi ofrequency power settings, The lesion's cross-sectional area, depth, vascul arity, and inflammation were commensurate with radiofrequency power. Tissue damage was indicated by variable inflammatory cell infiltration, fusion of collagen, pyknosis of fibroblasts, myonecrosis, and vascular thrombosis, w hereas synovial hyperplasia, fibroblast proliferation, and rowing of sarcol emmal nuclei demonstrated regenerative processes. This study revealed that radiofrequency power settings and heat loss through lavage solution play a significant role in heat distribution and morphologic alterations in joint capsule after arthroscopic application of monopolar radiofrequency energy.