The effect of monopolar radiofrequency energy on partial-thickness defects of articular cartilage.

PURPOSE To evaluate the effect of monopolar radiofrequency (RF) energy on partial-thickness defects of articular cartilage, comparing the outcome of partial-thickness defects treated with monopolar RF energy with that of treatment by conversion of partial-thickness defects to full-thickness defects by curettage and microfracture. TYPE OF STUDY Randomized trial using adult female sheep. MATERIALS AND METHODS Thirty-six sheep were used in this study. Both stifles in each animal were randomly assigned to 1 of the following 3 procedures: (1) partial-thickness defect without any treatment to serve as a sham-operated control, (2) partial-thickness defect with RF energy treatment, and (3) partial-thickness defect treated by conversion of the defect to a full-thickness defect by curettage and microfracture. Nine sheep were euthanized at 0, 2, 12, and 24 weeks after surgery (n = 6 per group). After euthanasia, cartilage samples were harvested from the defect sites, and chondrocyte viability was analyzed by confocal laser microscopy using a triple-labeling technique. Cartilage samples also were decalcified and stained with hematoxylin and eosin and safranin-O for histologic analysis. Surface properties of cartilage samples were analyzed using scanning electron microscopy. RESULTS The analysis of chondrocyte viability showed that RF treatment caused death of almost all chondrocytes in the defect. Histologic analysis showed that RF treatment caused detrimental effects to chondrocytes and proteoglycan concentration that progressed over time, and that full-thickness defects were repaired by fibrocartilage by 24 weeks after surgery. Scanning electron microscopy analysis indicated that RF-treated groups were significantly smoother and less irregular than control groups at 2, 12, and 24 weeks after surgery. CONCLUSIONS This study showed that monopolar RF energy caused long-term damage to cartilage in this sheep model and did not appear to have the beneficial effects reported in a previous study that evaluated application of this technique using a bipolar RF probe.