Monopolar radiofrequency energy effects on joint capsular tissue: Potential treatment for joint instability - An in vivo mechanical, morphological, and biochemical study using an ovine model

The purpose of this study was to evaluate the thermal effect of monopolar r adiofrequency energy, a potential treatment means for joint instability, on the mechanical, morphologic, and biochemical properties of joint capsular tissue in an in vivo ovine model. The energy was applied arthroscopically t o the synovial surface of the femoropatellar joint capsule of 24 sheep. The sheep were sacrificed at 0, 2, 6, and 12 weeks after surgery (6 per group) . Monopolar radiofrequency energy initially caused a significant decrease i n tissue stiffness and an increase in tissue relaxation properties, followe d by gradual improvement in the tissue's mechanical properties by 6 weeks a fter surgery. Microscopic examination illustrated that radiofrequency energ y initially caused collagen hyalinization and cell necrosis, followed by ac tive tissue repair. Biochemical analysis revealed that treated collagen was significantly more trypsin-susceptibile than untreated collagen at 6 and 2 weeks after surgery, indicating early collagen denaturation. This study de monstrated that this treatment initially caused a significantly deleterious effect on the mechanical properties of the joint capsule, which was associ ated with partial denaturation of joint capsular tissue. This was followed by gradual improvement of the mechanical, morphologic, and biochemical prop erties of the tissue over time.