Effects of monopolar radiofrequency energy on ovine joint capsular mechanical properties.

Radiofrequency energy may provide a relatively noninvasive method to stabilize joints with excessive laxity by thermally shrinking redundant joint capsular tissue. The authors determined the percentage of shrinkage associated with five radiofrequency treatment temperatures and evaluated the effect of this energy on the structural properties of joint capsular tissue in vitro. First, 36 adult sheep femoropatellar joint capsular specimens were treated with one of five treatment temperatures (n = 6 per group) or served as a control to determine tissue shrinkage. An additional 24 specimens were treated with three temperatures that resulted in different shrinkage: 45 degrees C, 65 degrees C, and 85 degrees C. Tissue stiffness, relaxation, and failure strength were determined for each specimen (n = 6 per group). Tissue shrinkage was correlated significantly with treatment temperature. There was a significant decrease in tensile stiffness in the 65 degrees C and 85 degrees C treatment groups. There were no significant differences between stress relaxation before treatment and after treatment. Relaxation properties after treatment were not different from each other or from control values either normalized to pretreatment values or expressed as raw data. Failure strength was not affected significantly at any temperature.