Effects of monopolar radiofrequency energy on ovine joint capsular mechanical properties

Radiofrequency energy may provide a relatively noninvasive method to stabil ize joints with excessive laxity by thermally shrinking redundant joint cap sular tissue. The authors determined the percentage of shrinkage associated with five radiofrequency treatment temperatures and evaluated the effect o f this energy on the structural properties of joint capsular tissue in vitr o. First, 36 adult sheep femoropatellar joint capsular specimens were treat ed with one of five treatment temperatures (n = 6 per group) or served as a control to determine tissue shrinkage. An additional 24 specimens were tre ated with three temperatures that resulted in different shrinkage: 45 degre es C, 65 degrees C, and 85 degrees C, Tissue stiffness, relaxation, and fai lure strength were determined for each specimen (n = 6 per group). Tissue s hrinkage was correlated significantly with treatment temperature. There was a significant decrease in tensile stiffness in the 65 degrees C and 85 deg rees C treatment groups. There were no significant differences between stre ss relaxation before treatment and after treatment. Relaxation properties a fter treatment were not different from each other or from control values ei ther normalized to pretreatment values or expressed as raw data. Failure st rength was not affected significantly at any temperature.