The effect of monopolar radiofrequency treatment pattern on joint capsular healing. In vitro and in vivo studies using an ovine model.

The purpose of this study was to compare joint capsular healing after two delivery patterns of monopolar radiofrequency energy: 1) uniform treatment of the joint capsule (paintbrush pattern) and 2) multiple single linear passes (grid pattern). First, an in vitro study was performed to compare the percent shrinkage of these two treatment patterns using the femoropatellar joints (stifles) of six sheep. Monopolar radiofrequency energy (settings, 70 degrees C/15W) was applied to the lateral joint capsule; the treated area was approximately 10 x 10 mm. There was no significant difference in shrinkage between the grid (27% +/- 8.7%) and paintbrush (29% +/- 7.9%) patterns. In the in vivo study, stifles of 24 sheep were randomly assigned to the paintbrush or the grid pattern groups and treatment was performed arthroscopically. Sheep were sacrificed immediately after surgery, or at 2, 6, or 12 weeks after surgery. At 6 weeks after surgery, confocal microscopy demonstrated that treated areas had almost completely repaired in the grid group; some nonviable areas were still present in the paintbrush group. Mechanical testing at 6 weeks indicated that joint capsule in the grid group had better mechanical properties than capsule in the paintbrush group. This study revealed that radiofrequency treatment of joint capsule in a grid pattern allowed faster healing than tissue treated in a paintbrush pattern.

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 radiofrequency 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 to 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 in tissue stiffness and an increase in tissue relaxation properties, followed by gradual improvement in the tissue's mechanical properties by 6 weeks after surgery. Microscopic examination illustrated that radiofrequency energy initially caused collagen hyalinization and cell necrosis, followed by active tissue repair. Biochemical analysis revealed that treated collagen was significantly more trypsin-susceptibile than untreated collagen at 0 and 2 weeks after surgery, indicating early collagen denaturation. This study demonstrated that this treatment initially caused a significantly deleterious effect on the mechanical properties of the joint capsule, which was associated with partial denaturation of joint capsular tissue. This was followed by gradual improvement of the mechanical, morphologic, and biochemical properties of the tissue over time.

The effect of radiofrequency energy on the length and temperature properties of the glenohumeral joint capsule.

The purpose of this in vitro study was to evaluate the effect of radiofrequency energy on the length and temperature properties of the glenohumeral joint capsule in a sheep model. Dissected glenohumeral joint capsules were placed in a 37 degrees C tissue bath and treated with radiofrequency energy at temperature settings of 60 degrees, 65 degrees, 70 degrees, 75 degrees and 80 degrees C. Pretreatment and posttreatment tissue length was measured, and tissue temperature changes were recorded at distances of 0.0, 0.5, 1.0, 1.5 mm away from the probe path. Tissue shrinkage was found to be less than 4% for treatments below 65 degrees C, and increased to 14% for treatments at 80 degrees C. Posttreatment lengths of tissues treated at 65 degrees, 70 degrees, 75 degrees, 80 degrees C were significantly shorter than pretreatment lengths. The maximum tissue temperatures directly below the probe were observed to be 3.7 degrees to 6.7 degrees C lower than the set temperatures. As the distance from the probe was increased, the tissue temperature was found to decrease, reaching a value of less than 45 degrees C at 1.5 mm for all five treatment temperature settings. This study provided basic information on temperature settings, tissue shrinkage, and tissue temperature distribution of radiofrequency treatment.