The Thermal Effect of Monopolar Radiofrequency Energy on the Properties of Joint Capsule An In Vivo Histologic Study Using a Sheep Model

The purpose of this in vivo study was to analyze the short-term tissue response of joint capsule to monopolar radiofrequency energy and to compare the effects of five power settings at 65°C on heat distribution in joint capsule. In 12 mature Hampshire sheep, the medial and lateral aspects of both stifles were treated with monopolar radiofrequency energy under arthroscopic control in a single uniform pass to the synovial surface. The radiofrequency generator power settings were 0, 10, 15, 20, 25, and 30 watts (N 8/group). The electrode tip temperature was 65°C. Histologic analysis at 7 days after surgery revealed thermal damage of capsule at all radiofrequency power settings. The lesion's cross-sectional area, depth, vascularity, 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, whereas synovial hyperplasia, fibroblast proliferation, and rowi...